Thermally processed image recording material

Abstract

 A thermally processed image recording material which comprises, on a support, at least (a) a reducible silver salt, (b) a reducing agent, (c) a binder, and (d) at least one kind of compound having a melting point of 115°C to 180°C and/or a log P value of 3.0 to 7.0 which is selected from the group consisting of polyhalogenated compounds represented by the following formula (1) and dimer compounds thereof:

wherein Z¹ and Z² independently represent a halogen atom, X¹ represents a hydrogen atom or an electron withdrawing group, Y¹ represents -CO- group or -SO₂-, Q represents an arylene group which may have one or more substituents or a divalent heterocyclic group which may have one or more substituents, L¹ represents -CONH-*, -SO₂NH-* or -COO-* where * represents a bonding site for W, L² represents -O-, an alkylene group, an arylene group or a combination thereof, W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group where the groups mentioned in the definition of W may have one or more substituents, and n represents 0 or 1.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a thermally processed image recording material. More particularly, the present invention relates to a thermally processed image recording material which causes almost no fog and exhibits high sensitivity as well as superior storage stability before development and superior image stability after development.

BACKGROUND OF THE INVENTION

[0002] A large number of photosensitive materials are known which have a photosensitive layer on a support and form image by imaging exposure. Examples of a system that enables environmental conservation or simplification of image formation includes a technique of forming an image by heat development.

[0003] In recent years, reduction of amount of waste processing solutions is strongly desired in the medical diagnosis field and the photographic art field from the standpoints of environmental protection and space savings. Techniques relating to photothermographic materials for use in medical diagnosis and photographic-art processes are required which enables efficient exposure by a laser scanner or a laser image setter and formation of a clear black image having high resolution and sharpen ss. The photothermographic materials can provide users with a simple and non-polluting heat development processing system that eliminates the use of solution-type processing chemicals.

[0004] Methods for forming an image by heat development are described, for example, in U.S. Patent Nos. 3,152,904 and 3,457,075 and D. Klosterboer, Imaging Processes and Materials, "Thermally Processed Silver Systems", Neblette, 8th ed., compiled by J.Sturge, V. Walworth and A. Shepp, Chapter 9, p.279, (1989). The photothermographic material contains a reducible light-insensitive silver source (e.g., organic silver salt), a photocatalyst (e.g., silver halide) in a catalytically active amount, and a reducing agent for silver, which are usually dispersed in an organic binder matrix. This photothermographic material is stable at an ambient temperature, but when the material is heated at a high temperature (e.g., 80°C or higher) after light exposure, silver is produced through an oxidation-reduction reaction between the reducible silver source (which functions as an oxidizing agent) and the reducing agent. The oxidation-reduction reaction is accelerated by catalytic action of a latent image generated upon exposure. The silver produced by the reaction of the reducible silver salt in the exposed region provides a black image and this presents a contrast to the non-exposure region to form an image.

[0005] Fog is a serious problem in photographic materials. Various researches have been made to reduce the fog in silver halide photosensitive materials for thermal photography. For example, U.S. Patent No. 3,589,903 discloses use of mercury salts. Furthermore, there have also been disclosed uses of carboxylic acids such as benzoic acid and phthalic acid (U.S. Patent No. 4,152,160), benzoylbenzoic acid compounds (U.S. Patent No. 4,784,939), indane or tetralincarboxylic acids (U.S. Patent No. 4,569,906), dicarboxylic acids (U.S. Patent No. 4,820,617), heteroaromatic carboxylic acids (U.S. Patent No. 4,626,500), halogenated compounds (U.S. Patent Nos. 4,546,075, 4,756,999, 4,452,885, 3,874,946 and 3,955,982), halogen molecules or halogen atoms bonded to heterocycles (U.S. Patent No. 5,028,523), palladium compounds (U.S. Patent No. 4,103,312 and British Patent No. 1,502,670), iron family compounds (U.S. Patent No. 4,128,428), substituted triazoles (U.S. Patent Nos. 4,123,374, 4,129,557 and 4,125,430), sulfur compounds (U.S. Patent Nos. 4,213,784, 4,245,033, and JP-A-51-26019 [the abbreviation "JP-A" as used herein means an "unexamined published Japanese patent application"]), thiouracils (U.S. Patent No.4,002,479), sulfinic acid (JP-A-50-123331), metal salts of thiosulfonic acid (U.S. Patent Nos. 4,125,403, 4,152,160 and 4,307,187), and combinations of metal salts of thiosulfonic acid and sulfinic acid (JP-A-53-20923 and JP-A-53-19825), thiosulfonic acid esters (JP-B-62-50810 [the abbreviation "JP-B" as used herein means an "examined Japanese patent publication"], JP-A-7-209797 and JP-A-9-43760).

[0006] There has also been disclosed use of disulfide compounds (JP-A-51-42529 and JP-B-63-37368). However, those compounds have drawbacks, for example, insufficient anti-fog effect, decrease of Dmax (maximum image density) and sensitivity at a larger addition amount and so forth.

[0007] Further, polyhalogenated compounds are extremely effective components for dry silver photosensitive materials as an antifoggant and a stabilizer for storage, and such compounds have been disclosed in JP-B-54-165, EP 605981A, EP 631176A, U.S. Patent Nos. 4,546,075, 4,756,999, 4,452,885, 3,874,946, 3,955,982, JP-A-10-171063, JP-A-10-197989, JP-A-9-265150 and so forth. However, those compounds have drawbacks, for example, insufficient anti-fog effect, insufficient storage stability of photosensitive materials before development, insufficient image stability after heat development (for example, coloration of non-image areas caused by heat or light), and decrease of sensitivity and Dmax when those compounds are added in such an amount that sufficiently suppresses the fog.

SUMMARY OF THE INVENTION

[0008] Accordingly, an object of the present invention is to solve those problems of the related art. The object of the present invention is to provide a thermally processed image recording material which causes almost no fog and exhibits high sensitivity as well as superior storage stability before development and superior image stability against high temperature in the dark and against light.

[0009] The inventors of the present invention assiduously studied in order to achieve the aforementioned object. As a result, they found that superior thermally processed image recording materials can be provided with desired advantages by using polyhalogenated compounds of a specific structure which have a melting point within a specific range or a log P value within a specific range. Thus, the present invention has been accomplished.

[0010] According to the first aspect of the present invention, there is provided a thermally processed image recording material which comprises, on a support, at least (a) a reducible silver salt, (b) a reducing agent, (c) a binder, and (d) at least one kind of compound having a melting point of 115°C to 180°C which is selected from the group consisting of polyhalogenated compounds represented by the following formula (1) and dimer compounds thereof:

wherein Z¹ and Z² independently represent a halogen atom, X¹ represents a hydrogen atom or an electron withdrawing group, Y¹ represents -CO- group or -SO₂-, Q represents an arylene group which may have one or more substituents or a divalent heterocyclic group which may have one or more substituents, L¹ represents -CONH-*, -SO₂NH-* or -COO-* where * represents a bonding site for W, L² represents -O-, an alkylene group, an arylene group or a combination thereof, W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group where the groups mentioned in the definition of W may have one or more substituents, and n represents 0 or 1.

[0011] According to the second aspect of the present invention, there is provided a thermally processed image recording material which comprises, on a support, at least (a) a reducible silver salt, (b) a reducing agent, (c) a binder, and (d) at least one kind of compound having a log P value of 3.0 to 7.0 which is selected from the group consisting of polyhalogenated compounds represented by the following formula (1) and dimer compounds thereof:

wherein Z¹ and Z² independently represent a halogen atom, X¹ represents a hydrogen atom or an electron withdrawing group, Y¹ represents -CO- group or -SO₂-, Q represents an arylene group which may have one or more substituents or a divalent heterocyclic group which may have one or more substituents, L¹ represents -CONH-*, -SO₂NH-* or -COO-* where * represents a bonding site for W, L² represents -O-, an alkylene group, an arylene group or a combination thereof, W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group where the groups mentioned in the definition of W may have one or more substituents, and n represents 0 or 1.

[0012] Preferably, in the formula (1), Z¹, Z² and X¹ represent a bromine atom, Y¹ represents -SO₂-, Q represents an arylene group which may have one or more substituents, W represents a hydrogen atom or an alkyl group which may have one or more substituents, and n is 0.

[0013] Preferably, the thermally processed image recording material of the present invention is a photothermographic material which further comprises a photosensitive silver halide.

[0014] Preferably, the compound represented by the formula (1) has a melting point of 115°C to 180°C and a log P value of 3.0 to 7.0.

[0015] Preferably, the compound represented by the formula (1) has a log P value of 3.5 to 6.0.

[0016] Preferably, the electron withdrawing group represented by X¹ in the formula (1) is cyano group, a C_2-30 alkoxycarbonyl group, a C_7-30 aryloxycarbonyl group, a C_1-30 carbamoyl group, a sulfamoyl group with may be substituted with a C_0-30 alkyl group, a C_1-30 alkylsulfonyl group, a C_6-30 arylsulfonyl group, a halogen atom or an acyl group.

[0017] Preferably, the substituent on the arylene group represented by Q in the formula (1) is selected from a group consisting of a halogen atom such as fluorine atom, chlorine atom, bromine atom or iodine atom; an alkyl group including a cycloalkyl group, an active methine group and so forth; an aralkyl group; an alkenyl group; an alkynyl group; an aryl group; a heterocyclic group including N-substituted nitrogen-containing heterocyclic group such as morpholino group; an alkoxycarbonyl group; an aryloxycarbonyl group; a carbamoyl group; an imino group; an imino group substituted at the N atom; a thiocarbonyl group; a carbazoyl group; cyano group; a thiocarbamoyl group; an alkoxy group; an aryloxy group; a heterocyclyloxy group; an acyloxy group; an (alkoxy or aryloxy)carbonyloxy group; a sulfonyloxy group; an acylamino group; a sulfonamido group; a ureido group; a thioureido group; an imido group; an (alkoxy or aryloxy)carbonylamino group; a sulfamoylamino group; a semicarbazide group; a thiosemicarbazide group; an (alkyl or aryl)sulfonylureido group; a nitro group; an (alkyl or aryl)sulfonyl group; a sulfamoyl group; a group containing phosphoric acid amide or phosphoric acid ester structure; and a silyl group.

[0018] Preferably, the heterocycle in the heterocyclic group represented by Q in the formula (1) is a ring of pyridine, pyrazine, pyrimidine, benzothiazole, benzimidazole, thiadiazole, quinoline, isoquinoline or triazole.

[0019] Preferably, L¹ in the formula (1) represents -CONH-*,

[0020] Preferably, the compounds represented by the formula (1) is added to the image-forming layer or a layer adjacent thereto.

[0021] Preferably, the compounds represented by the formula (1) is added in an amount of 1 × 10^-4 to 1 mole per mole of the light insensitive silver salt of the image-forming layer.

BRIEF DESCRIPTION OF THE DRAWING

[0022] 

Fig. 1 is a side view of one example of heat developing apparatus. In the figure, there are shown a thermally processed image recording material 10, carrying-in roller pairs 11, carrying-out roller pairs 12, rollers 13, a flat surface 14, heaters 15, and guide panels 16. The apparatus consists of a preheating section A, a heat development section B, and a gradual cooling section C.

PREFERRED EMBODIMENT OF THE INVENTION

[0023] Embodiments and working examples of the present invention will be explained in detail below.

[0024] The thermally processed image recording material of the present invention comprises, on a support, an image-forming layer containing an organic silver salt as a reducible silver salt and a binder, and contains a reducing agent in a layer on the image-forming layer side. The thermally processed image recording material of the present invention preferably further comprises a photosensitive silver halide, and the image-forming layer is preferably a photosensitive layer containing a photosensitive silver halide. Further, one of the characteristics of the thermally processed image recording material of the present invention is that it contains at least one kind of compound having a melting point within a specific range or a log P value within a specific value which is selected from the group consisting of polyhalogenated compounds represented by the formula (1) and dimer compounds thereof in a layer on the image-forming layer side.

[0025] By using the specific polyhalogenated compounds defined in the present specification for thermally processed image recording materials, there can be obtained superior advantages, i.e., higher sensitivity, suppressed heat-induced fog in non-image areas and increased image storability against heat and light compared with the cases using other polyhalogenated compounds.

[0026] It was found for the first time by the present invention that the superior advantages of the present invention could be achieved by using the compounds of the formula (1) having a melting point of 115°C to 180°C, and it could not have been expected at all. If a compound of the formula (1) having a melting point lower than 115°C is used, sensitivity is decreased. On the other hand, if a compound of the formula (1) having a melting point higher than 180°C is used, the effects for suppressing fog and improving image storability become insufficient. The melting point is preferably 120°C to 180°C.

[0027] It was also found for the first time by the present invention that the superior advantages of the present invention could be achieved by using the compounds of the formula (1) having a log P value of 3.0 to 7.0, and it could not have been expected at all. If a compound of the formula (1) having a log P value falling outside the range, the effects for suppressing fog and improving image storability become insufficient. The log P value is preferably 3.5 to 6.0. The log P value represents a logarithm of distribution coefficient P between an aqueous phase and a non-polar liquid phase, and defined in Medicinal Chemistry, p.25 [Ishiyaku Shuppan Co., Ltd.] and so forth. Specifically, the sample is dissolved in two phase liquid of octanol and water and a ratio (P) of concentrations in each phase is determined wherein

. Log P value is generally used as an indicator of hydrophobicity in the chemical field, and larger value of log P means larger hydrophobicity. The experimental procedure for the determination of log P value is described in Experimental Section of Journal of Organic Chemistry., 32, 2584-2585 (1967). The log P value can conveniently determined by using MacLog P (ver 2.0.3), which is a software sold by Biobyte Co., Ltd.

[0028] The formula (1), which represents the structures of the polyhalogenated compounds used in the present invention, will be explained. The formula (1) is shown below.

[0029] In the formula (1), Z¹ and Z² independently represent a halogen atom. The halogen atom referred to in the present specification may be any of fluorine, chlorine, bromine and iodine. It is preferred that both of Z¹ and Z² represent a bromine atom.

[0030] In the formula (1), X¹ is a hydrogen atom or an electron withdrawing group. The electron withdrawing group used herein is a substituent having a Hammett's substituent constant σp of a positive value, and specific examples thereof include cyano group, a C_2-30 alkoxycarbonyl group, a C_7-30 aryloxycarbonyl group, a C_1-30 carbamoyl group, a sulfamoyl group with may be substituted with a C_0-30 alkyl group, a C_1-30 alkylsulfonyl group, a C_6-30 arylsulfonyl group, a halogen atom, an acyl group, a heterocyclic group and so forth. In the formula (1), X¹ is preferably a halogen atom, more preferably a bromine atom.

[0031] In the formula (1), it is most preferred that all of Z¹, Z² and X¹ represent a bromine atom.

[0032] In the formula (1), Y¹ is -CO- or -SO₂-, and it is preferably -SO₂-.

[0033] In the formula (1), Q represents an arylene group which may have one or more substituents or a divalent heterocyclic group which may have one or more substituents.

[0034] The arylene group represented by Q in the formula (1) is preferably a monocyclic or condensed ring arylene group having 6-30 carbon atoms, preferably a monocyclic or condensed ring arylene group having 6-20 carbon atoms. Examples thereof include, for example, phenylene, naphthylene and so forth, and it is particularly preferably a phenylene group. The arylene group represented by Q may have one or more substituents. If there are two or more substituents, they may be identical or different. The substituent on the arylene group may be any group so long as it does not adversely affect photographic performance. Examples thereof include, for example, a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom), an alkyl group (including a cycloalkyl group, an active methine group and so forth), an aralkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group (including N-substituted nitrogen-containing heterocyclic group such as morpholino group), an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an imino group, an imino group substituted at the N atom, a thiocarbonyl group, a carbazoyl group, cyano group, a thiocarbamoyl group, an alkoxy group, an aryloxy group, a heterocyclyloxy group, an acyloxy group, an (alkoxy or aryloxy)carbonyloxy group, a sulfonyloxy group, an acylamino group, a sulfonamido group, a ureido group, a thioureido group, an imido group, an (alkoxy or aryloxy)carbonylamino group, a sulfamoylamino group, a semicarbazide group, a thiosemicarbazide group, an (alkyl or aryl)sulfonylureido group, a nitro group, an (alkyl or aryl)sulfonyl group, a sulfamoyl group, a group containing phosphoric acid amide or phosphoric acid ester structure, a silyl group and so forth. These substituents may further be substituted with similar substituents.

[0035] Particularly preferred substituents on the arylene group represented by Q in the formula (1) are an alkyl group, an alkoxy group, an aryloxy group and a halogen atom.

[0036] In the formula (1), the heterocycle of the divalent heterocyclic group represented by Q may be a saturated or partially saturated or aromatic 5- to 7-membered heterocycle containing at least one of N, O and S atoms. The heterocycle may consist of a single ring, or may form a condensed ring with another ring or other rings. Examples of the heterocycle in the heterocyclic group represented by Q include, for example, rings of pyridine, pyrazine, pyrimidine, benzothiazole, benzimidazole, thiadiazole, quinoline, isoquinoline, triazole and so forth. The heterocyclic group may have one or more substituents. If there are two or more substituents, they may be identical or different. Examples of the substituent on the heterocyclic group include, for example, those mentioned for the substituent on the arylene group represented by Q.

[0037] In the formula (1), Q is preferably an arylene group, and it is particularly preferably a phenylene group.

[0038] In the formula (1), L² represents -O-, an alkylene group (having preferably 1-30 carbon atoms, more preferably 1-20 carbon atoms, particularly preferably 1-10 carbon atoms), an arylene group (having preferably 6-30 carbon atoms, more preferably 6-20 carbon atoms, particularly preferably 6-10 carbon atoms) or a group composed of a combination of the foregoing. L² is preferably an alkylene group, -O- or a group composed of a combination thereof.

[0039] In the formula (1), n represents 0 or 1, preferably 0.

[0040] In the formula (1), L¹ represents -CONH-*, -SO₂NH-* or -COO-*, preferably -CONH-*, where * represents a bonding site for W.

[0041] In the formula (1), W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, and these groups may have one or more substituents.

[0042] The alkyl group, alkenyl group and alkynyl group represented by W in the formula (1) are liner, branched or cyclic groups or groups composed of a combination thereof. W is preferably an alkyl group having preferably 1-20 carbon atoms, more preferably 1-12 carbon atoms, particularly preferably 1-6 carbon atoms. Examples thereof include, for example, methyl, ethyl, allyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, n-pentyl, sec-pentyl, iso-pentyl, 3-pentyl, n-hexyl, n-octyl, n-dodecyl, cyclohexyl and so forth.

[0043] The alkyl group, alkenyl group and alkynyl group represented by W in the formula (1) may have a substituent, preferably a substituent having 3 or less of carbon atoms and π value (a value defined as π value in Journal of Medical Chemistry, 1973, 1207) of -0.3 or higher. Specific examples thereof include a halogen atom (e.g., fluorine atom, chlorine atom, bromine atom), an alkoxy group (e.g., methoxy group, ethoxy group), a nitro group, an amino group (e.g., dimethylamino group), an alkoxycarbonyl group (e.g., methoxycarbonyl group, ethoxycarbonyl group), an acylthio group (e.g., acetyl thio group), a silyl group, an alkylthio group (e.g., methylthio group, ethylthio group), a heterocyclic group and so forth. The substituent is preferably a halogen atom or an alkoxy group.

[0044] The aryl group represented by W in the formula (1) is a monocyclic or condensed ring aryl group having preferably 6-20 carbon atoms, more preferably 6-16 carbon atoms, particularly preferably 6-10 carbon atoms. Examples thereof include, for example, phenyl group, naphthyl group and so forth, and it is preferably a phenyl group. The aryl group represented by W may have a substituent, and examples thereof include those mentioned for the substituent on the arylene group represented by Q.

[0045] The heterocyclic group represented by W in the formula (1) may be a saturated or partially saturated or aromatic 5- to 7-membered heterocyclic group containing at least one of N, O and S atoms. The heterocyclic group may consist of a single ring, or it may form a condensed ring with another ring or other rings. Examples of the heterocyclic group include, for example, pyridyl, pyrazinyl, pyrimidinyl, thiazolyl, imidazolyl, benzothiazolyl, benzimidazolyl, thiadiazolyl, quinolyl, isoquinolyl, triazolyl and so forth. These may have a substituent, and examples thereof include those mentioned for the substituent on the arylene group represented by Q.

[0046] W in the formula (1) is preferably a hydrogen atom, an alkyl group or an aryl group, particularly preferably a hydrogen atom or an alkyl group.

[0047] According to the present invention, a dimer compound of a compound represented by the formula (1) may also be used. The dimer compound is a compound where two compounds of the formula (1) is bonded directly at their terminals of the group represented by W via a bridging group such as -O-. In the present invention, a compound of the formula (1) (monomer compound), a dimer compound thereof or a combination thereof may be used.

[0048] The compounds of the formula (1) can be synthesized by usual organic synthesis reactions known to those skilled in the art. For example, they can be synthesized by the method described below.

[0049] First, readily available 3-sulfinobenzoic acid (A), sodium hydroxide, sodium chloroacetate and potassium iodide are dissolved in water and stirred at 80°C for several hours. After the internal temperature is lowered to 30°C, the reaction mixture was added with concentrated hydrochloric acid and stirred for a while to deposit crystals. The crystals are collected by suction filtration and dried to obtain Intermediate (B).

[0050] Next, bromine is added dropwise to an aqueous solution of sodium hydroxide at room temperature, and then an aqueous solution of Intermediate (B) and sodium hydroxide is added dropwise thereto at room temperature. Deposited crystals are taken by filtration, and the obtained crystals are added to diluted hydrochloric acid, stirred and taken by filtration. The crystals are fully washed with water and dried to obtain Intermediate (C).

[0051] Intermediate (C) and dimethylformamide (DMF) are dissolved in thionyl chloride and the mixture is stirred at 70°C for 30 minutes. Then, excess thionyl chloride is evaporated under reduced pressure to obtain Intermediate (D).

[0052] Finally, a methanol solution of an alkylamine is cooled with ice, and added with Intermediate (D). After stirring the mixture at room temperature for 10 minutes, diluted aqueous hydrochloric acid is added to deposit white crystals. The crystals are taken by filtration, fully washed with water and dried to obtain a compound of the formula (1).

[0053] Other compounds can similarly be synthesized by, for example, substituting other regents for the 3-sulfinobenzoic acid used as the starting material or suitably selecting the type of alkylamine.

[0054] Structures, melting points or log P values of P-1 to P-25 and P'-1 to P'-26 as specific examples of the compound used in the present invention will be shown below. However, the compounds that can be used in the present invention are not limited to these compounds. The melting points were measured by using Model 530 produced by BUCHI, and the Log P values were calculated by the software MacLogP (ver 2.0.3) sold by Biobyte Co., Ltd.

[0055] The compounds represented by the formula (1) may be used for the thermally processed image recording material of the present invention by dissolving said compounds in water or a suitable organic solvent, for example, alcohols such as methanol, ethanol, propanol and fluorinated alcohol, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, dimethylformamide, dimethyl sulfoxide, methyl cellosolve and so forth. If the compounds have an acidic group bonded thereto, they may be neutralized with equivalent alkali and added as salts.

[0056] The compounds of the formula (1) may also be used in the thermally processed image recording material as an emulsified dispersion mechanically prepared according to an already well known emulsification dispersion method by using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, ethyl acetate or cyclohexanone as an auxiliary solvent for dissolution. Alternatively, the compounds may be used after dispersion of a powder thereof in water by using a ball mill, a colloid mill, a sand grinder mil, MANTON GAULIN, a microfluidizer, or by means of ultrasonic wave according to a known method for solid dispersion.

[0057] The compounds represented by the formula (1) may be added to any layers on a support provided on the image-forming layer side, i.e., the image-forming layer and/or the other layers provided on the same side. The compounds may preferably be added to the image-forming layer or a layer adjacent thereto. Two or more kinds of the compounds represented by the formula (1) may be used in combination.

[0058] The addition amount of the compounds represented by the formula (1) may be 1 × 10^-4 to 1 mole, preferably 1 × 10^-3 to 0.8 mole, more preferably 5 × 10^-3 to 0.5 mole, per mole of the light insensitive silver salt of the image-forming layer.

[0059] The thermally processed image recording material of the present invention comprises an organic silver salt as a reducible silver salt. An organic silver salt that can be used in the present invention is a silver salt relatively stable against light, but forms a silver image when it is heated at 80°C or higher in the presence of an exposed photocatalyst (e.g., a latent image of photosensitive silver halide) and a reducing agent. The organic silver salt may be any organic substance containing a source capable of reducing the silver ion. Such light insensitive organic silver salts are disclosed in JP-A-10-62899, paragraphs 0048 to 0049 and EP 0803763A1, page 18, line 24 to page 19, line 37. Silver salts of an organic acid, particularly silver salts of a long chained aliphatic carboxylic acid (having from 10 to 30, preferably from 15 to 28 carbon atoms) are preferred. Preferred examples of the organic acid silver salt include silver behenate, silver arachidinate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver maleate, silver fumarate, silver tartrate, silver linoleate, silver butyrate, silver camphorate, mixtures thereof and so forth.

[0060] The shape of the organic silver salt that can be used for the present invention is not particularly limited. However, scaly organic silver salts are preferred for the present invention. Scaly organic silver salts are herein defined as follows. A sample of an organic silver salt to be analyzed is observed with an electronic microscope, and grains of the salt seen in the field are approximated to rectangular parallelepipeds. The three different edges of each rectangular parallelepiped are represented as a, b and c where a is the shortest, c is the longest, and c and b may be the same. From the shorter edges a and b, x is obtained according to the following equation:

[0061] The values of x are obtained for about 200 grains seen in the field, and an average of them (x (average)) is obtained. Samples that satisfy the requirement of x (average) ≥ 1.5 are defined to be scaly. Scaly grains preferably satisfy 30 ≥ x (average) ≥ 1.5, more preferably 20 ≥ (average) ≥ 2.0. In this connection, acicular (needle-like) grains falls satisfy 1 ≤ x (average) < 1.5.

[0062] In scaly grains, it is understood that a corresponds to the thickness of tabular grains of which main planes are defined by the sides of b and c. The average of a is preferably from 0.01 µm to 0.23 µm, more preferably from 0.1 µm to 0.20 µm. The average of c/b is preferably from 1 to 6, more preferably from 1.05 to 4, even more preferably from 1.1 to 3, particularly preferably from 1.1 to 2.

[0063] The grain size distribution of the organic silver salt is preferably monodispersed. The term "monodispersed" as used herein means that the percentage of the value obtained by dividing the standard deviation of the length of the short axis or long axis by the length of the short axis or long axis, respectively, is preferably 100% or less, more preferably 80% or less, further preferably 50% or less. The shape of the organic silver salt can be determined from a transmission electron microscope image of organic silver salt dispersion. Another method for determining the monodispesibility is a method involving obtaining the standard deviation of a volume weight average diameter of the organic silver salt. The percentage (coefficient of variation) of the value obtained by dividing the standard deviation by the volume weight average diameter is preferably 100% or less, more preferably 80% or less, further preferably 50% or less. As a measurement method, for example, the grain size (volume weight average diameter).can be determined by irradiating organic silver salt dispersed in a solution with a laser ray and determining an autocorrelation function of the fluctuation of the scattered light on the basis of the change in time.

[0064] The organic acid silver salt used for the present invention is prepared by allowing a solution or suspension of alkali metal salt (e.g., Na salt, K salt, Li salt) of the above-described organic acid to react with silver nitrate. The organic acid alkali metal salt can be obtained by treating the organic acid with an alkali. The preparation of the organic acid silver salt may be performed batchwise or continuously in any appropriate reaction vessel. Stirring in the reaction vessel may be effected by any stirring method according to the required properties of the grains. The organic acid silver salt is preferably prepared by a method of gradually or rapidly adding an aqueous silver nitrate solution to a reaction vessel containing an organic acid alkali metal solution or suspension, a method of gradually or rapidly adding a previously prepared organic acid alkali metal salt solution or suspension to a reaction vessel containing an aqueous silver nitrate solution, or a method of previously preparing an aqueous silver nitrate solution and an organic acid alkali metal salt solution or suspension and simultaneously adding those solutions to a reaction vessel.

[0065] The aqueous silver nitrate solution and the organic acid alkali metal salt solution or suspension may have any concentration so as to control the grain size of the organic acid silver salt to be prepared and may be added at any addition rate. The aqueous silver nitrate solution and the organic acid alkali metal salt solution or suspension each may be added by a method of adding the solution or suspension at a constant rate or a method of adding the solution or suspension while increasing or decreasing the addition rate with any time function. The solution may also be added to the liquid surface or in the liquid of the reaction solution. When an aqueous silver nitrate solution and an organic acid alkali metal salt solution or suspension are previously prepared and then simultaneously added to a reaction vessel, either of the aqueous silver nitrate solution and the organic acid alkali metal salt solution or suspension may be added in advance, but the aqueous silver nitrate solution is preferably added in advance by a precedence degree of from 0 to 50 volume %, more preferably from 0 to 25 volume %, of the entire addition amount. Furthermore, a method of adding the solution while controlling the pH or silver potential of the reaction solution during the reaction described in JP-A-9-127643 may be preferably used.

[0066] The pH of the aqueous silver nitrate solution and the organic acid alkali metal salt solution or suspension added may be adjusted according to the required properties of the grains. For adjusting the pH, any acid or alkali may be added. Furthermore, depending on the required property of the grains, for example, in order to control the grain size of the organic acid silver salt to be prepared, the temperature in the reaction vessel may be suitably selected. The temperature of the aqueous silver nitrate solution and the organic acid alkali metal salt solution or suspension added may also be suitably controlled. In order to ensure the liquid flowability of the organic acid alkali metal salt solution or suspension, the solution is preferably heated and maintained at a temperature of 50°C or higher.

[0067] The organic acid silver salt for use in the present invention is preferably prepared in the presence of a tertiary alcohol. The tertiary alcohol preferably has a total carbon number of 15 or less, more preferably 10 or less. Examples of preferred tertiary alcohols include tert-butanol. The tertiary alcohol may be added in any timing during the preparation of the organic acid silver salt. The tertiary alcohol is preferably added at the time of preparation of the organic acid alkali metal salt to dissolve the organic alkali metal salt. The tertiary alcohol may be added in any amount of from 0.01 to 10 in terms of the weight ratio to H₂O used as a solvent for the preparation of the organic acid silver salt, and preferably added in an amount of from 0.03 to 1 in terms of the weight ratio to H₂O.

[0068] Preferably, the scaly organic silver salt for use in the present invention is prepared by reacting an aqueous solution of a water-soluble silver salt with an aqueous solution of an alkali metal salt of an organic acid in a aqueous tertiary alcohol solution in a reaction vessel (the method includes a step of adding the aqueous tertiary alcohol solution containing an alkali metal salt of an organic acid into a liquid already existing in a reaction vessel), wherein the temperature difference between the liquid already existing in the reaction vessel and the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid to be added thereto falls between 20°C and 85°C. The liquid existing in the reaction vessel in advance is preferably an aqueous solution of a water-soluble silver salt put into the reaction vessel in advance. In a case where the aqueous solution of a water-soluble silver salt is not put into the reaction vessel in advance but is put into the vessel from the start along with an aqueous solution of an alkali metal salt of an organic acid in a tertiary alcohol, the liquid existing in the reaction vessel is water or a mixed solvent of water and a tertiary alcohol, as will be mentioned hereinafter. Even in a case where the aqueous solution of a water-soluble silver salt is put into the reaction vessel in advance, the reaction vessel may contain water or a mixed solvent of water and a tertiary alcohol.

[0069] With the temperature difference between the liquid already existing in the reaction vessel and the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid to be added being controlled to fall within the defined range during the addition, the crystal shape of the organic silver salt to be formed can favorably controlled.

[0070] The water-soluble silver salt is preferably silver nitrate. The concentration of the water-soluble silver salt in the aqueous solution is preferably 0.03 mole/liter to 6.5 moles/liter, more preferably 0.1 mole/liter to 5 moles/liter. The pH of the aqueous solution is preferably 2 to 6, more preferably 3.5 to 6.

[0071] The aqueous solution of a water-soluble silver salt may contain a tertiary alcohol having from 4 to 6 carbon atoms. The amount of the tertiary alcohol, if any, in the aqueous solution is 70% by volume or less, preferably 50% by volume or less, based on the total volume of the aqueous solution. The temperature of the aqueous solution is preferably 0°C to 50°C, more preferably 5°C to 30°C. In a case where the aqueous solution of a water-soluble silver salt and the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid are simultaneously added into a reaction vessel as in the manner to be mentioned below, the temperature of the solutions is most preferably 5°C to 15°C.

[0072] Specific examples of the alkali metal of the alkali metal salt of an organic acid include Na and K. The alkali metal salt of an organic acid may be prepared by adding NaOH or KOH to an organic acid. In this step, it is desirable that the amount of the alkali to be added to an organic acid is not larger than the equivalent amount of the organic acid so that unreacted organic acid can remain in the reaction mixture. In this case, the amount of the remaining unreacted organic acid may be 3 mole % to 50 mole %, preferably 3 mole % to 30 mole %, per mole of the total organic acid. After the alkali is added in an amount larger than the intended amount, additional acid such as nitric acid or sulfuric acid may be added to neutralize the excess alkali to perform the preparation.

[0073] Depending on the required properties of the organic silver salt, the pH of the reaction system may be controlled. For controlling the pH, any acid or alkali may be used.

[0074] Further, the aqueous solution of a water-soluble silver salt, the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid, or even the liquid existing in the reaction vessel in advance (solvent etc.) may be optionally added with compounds of the formula (1) described in JP-A-62-65035, water-soluble group-containing N-heterocyclic compounds such as those described in JP-A-62-150240, inorganic peroxides such as those described in JP-A-50-101019, sulfur compounds such as those described in JP-A-51-78319, disulfide compounds such as those described in JP-A-57-643, hydrogen peroxide and so forth.

[0075] The aqueous tertiary alcohol solution of an alkali metal salt of an organic acid is preferably in a mixed solvent of water and a tertiary alcohol having 4 to 6 carbon atoms for ensuring uniformity of the solution. Alcohols in which the number of carbon atoms exceeds the defined range are not preferred as their miscibility with water becomes poor. Among the tertiary alcohol having 4 to 6 carbon atoms, most preferred is tert-butanol as its miscibility with water is the highest of all. Alcohols other than such tertiary alcohols are also unfavorable as mentioned above since they have a reducing property and adversely affect the process of forming the intended organic silver salts. The amount of the tertiary alcohol that may be used in the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid may be 3% by volume to 70% by volume, preferably 5% by volume to 50 % by volume, relative to the volume of water in the aqueous solution.

[0076] The concentration of the alkali metal salts of an organic acid in the aqueous tertiary alcohol solution of the alkali metal salts of an organic acid may be 7% by weight to 50% by weight, preferably 7% by weight to 45% by weight, more preferably 10% by weight to 40% by weight.

[0077] The temperature of the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid to be added into a reaction vessel is preferably 50°C to 90°C, more preferably 60°C to 85°C, most preferably 65°C to 85°C, in order that the alkali metal salt of an organic acid in the solution should be kept at a temperature sufficient for preventing the salt from being crystallized or solidified. For constantly controlling the predetermined reaction temperature, it is desirable that the temperature of the aqueous solution should be controlled to be a temperature falling within the defined range all the time.

[0078] The organic silver salt preferably used for the present invention may be prepared according to i) a method comprising first putting the total amount of an aqueous solution of a water-soluble silver salt into a reaction vessel, followed by adding thereto an aqueous tertiary alcohol solution of an alkali metal salt of an organic acid as a single portion (single addition method), or ii) a method comprising simultaneously putting both an aqueous solution of a water-soluble silver salt and an aqueous tertiary alcohol solution of an alkali metal salt of an organic acid into a reaction vessel at least any time (simultaneous addition method). In the present invention, the latter simultaneous addition method is preferred, since the mean grain size of the organic silver salt produced can be well controlled to narrow the grain size distribution thereof by the latter method. In this method, it is desirable that at least 30% by volume, more preferably from 50 to 75% by volume, of the total amount of the two is simultaneously put into the reaction vessel. In a case where any one of the two is put into the reaction vessel in advance, it is desirable that the solution of a water-soluble silver salt is put into the vessel.

[0079] In any case, the temperature of the liquid previously existing in the reaction vessel (the liquid is the aqueous solution of a water-soluble silver salt put into the reaction vessel in advance as mentioned above; or when the aqueous solution of a water-soluble silver salt is not put into the reaction vessel in advance, the liquid is a solvent put into the vessel in advance as described below) is preferably 5°C to 75°C, more preferably 5°C to 60°C, most preferably 10°C to 50°C. Throughout the entire process of the reaction, the reaction temperature is preferably controlled to be a constant temperature falling within the defined range. As the case may be, however, the reaction temperature may be controlled in some temperature profiles varying within the defined range.

[0080] The temperature difference between the liquid existing in the reaction vessel and the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid to be added is preferably 20°C to 85°C, more preferably 30°C to 80°C. In this case, it is desirable that the temperature of the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid should be higher than that of the liquid already existing in the reaction vessel.

[0081] By performing the process as described above, the rate at which the aqueous tertiary alcohol solution of an alkali metal salt of an organic acid having a higher temperature is rapidly cooled by the reaction vessel and precipitated to give fine crystals, and the rate at which the deposited alkali metal salt is reacted with the water-soluble silver salt to give an organic silver salt are both favorably controlled, and therefore the crystal shape, crystal size and crystal size distribution of the organic silver salt can be favorably controlled. In addition, the properties of the thermally processed material, in particular, as a photothermographic image recording material, can also be improved.

[0082] The reaction vessel may contain a solvent in advance, and water is preferably used as the solvent which is contained in advance. A mixed solvent of water and a tertiary alcohol may also be preferably used.

[0083] The aqueous tertiary alcohol solution of an alkali metal salt of an organic acid, the aqueous solution of a water-soluble silver salt, or the reaction mixture may optionally be added with a dispersing aid that is soluble in aqueous media. The dispersing aid may be any one capable of dispersing the organic silver salt formed. Specific examples thereof include those mentioned below as the dispersing aid for organic silver salts.

[0084] In the process of producing organic silver salts, the salts formed are preferably desalted and dehydrated. The methods for desalting and dehydrating the salts are not particularly limited, and well known conventional method may be used. For example, preferably used are known filtration methods including centrifugation filtration, suction filtration, ultrafiltration, flocculation by the coagulation method followed by washing with water and so forth. Also preferably used is supernatant removal by centrifugal precipitation. The desalting and dehydration may be effected once or may be repeated. Addition and removal of water may be effected continuously or separately. The desalting and the dehydration is preferably effected to such a degree that the finally removed water should have a conductivity of 300 µS/cm or less, more preferably 100 µS/cm or less, most preferably 60 µS/cm or less. As for the conductivity, there is no particular lower limit, it may generally be 5 µS/cm or so.

[0085] To improve conditions of the coated surface of the thermally processed image recording material, in particular, the photothermographic image recording material, the organic silver salt formed is preferably further processed in a process comprising dispersing it in water, forming a high-pressure and high-speed flow of the resulting aqueous dispersion, and re-dispersing the salt by lowering the pressure to form a fine aqueous dispersion of the salt. In this case, the dispersion medium preferably consists of water alone, but may contain an organic solvent so long as it is in an amount of 20% by weight or less of the dispersion medium.

[0086] As for the method for finely dispersing the organic silver salt, for example, it can be mechanically dispersed in the presence of a dispersing aid by a known dispersing apparatus (e.g., a high-speed mixer, a homogenizer, a high-speed impact mill, a Banbary mixer, a homomixer, a kneader, a ball mill, a vibrating ball mill, a planetary ball mill, an attriter, a sand mill, a bead mill, a colloid mill, a jet mill, a roller mill, a trone mill or a high-speed stone mill).

[0087] It is desirable that the organic silver salt is dispersed substantially in the absence of a photosensitive silver salt, since the photosensitive silver salt will increase fog and markedly lower sensitivity, if it is present during the dispersion. For the present invention, the amount of the photosensitive silver salt that may be in the aqueous dispersion of the organic silver salt should be 0.1 mole % or less per mole of the organic silver salt, and the photosensitive silver salt is not added intentionally.

[0088] For obtaining a uniform organic silver salt solid dispersion having a high S/N ratio and a small grain size and being free from coagulation, it is preferable to uniformly apply strong force within a range that should not cause breakage or unacceptable temperature increase of the organic silver salt grains as the image-forming media. To this end, a dispersion method comprising the steps of converting an aqueous dispersion that contains an organic silver salt and an aqueous solution of dispersant into a high-speed flow, and then releasing the pressure, is preferred.

[0089] The dispersing apparatuses and techniques used for performing the above-described re-dispersion method are described in detail, for example, in Toshio Kajiuchi and Hiromoto Usui, Bunsan-Kei Rheology to Bunsanka Gijutsu (Rheology of Dispersion System and Dispersion Technology), pp.357-403, Shinzan Sha Shuppan (1991), and Kagaku Kogaku no Shinpo (Progress of Chemical Engineering), vol. 24, pp. 184-185, compiled by Corporation Kagaku Kogakukai Tokai Shibu, Maki Shoten (1990), JP-A-59-49832, U.S. Patent No. 4,533,254, JP-A-8-137044, JP-A-8-238848, JP-A-2-261525, JP-A-1-94933 and so forth. The re-dispersion method used in the present invention comprises steps of supplying a water dispersion containing at least an organic silver salt into a pipeline under a positive pressure by means of a high-pressure pump or the like, passing the dispersion through a narrow slit provided inside the pipeline, and then subjecting the dispersion to rapid pressure reduction to perform fine dispersion.

[0090] As for the high-pressure homogenizer, it is generally considered that fine and uniform dispersion can be achieved therein by enhancing (a) "shear force" to be generated at the passage of a dispersoid through a narrow slit (75 µm to 350 µm or so) under high pressure at high speed and (b) "cavitation force" to be generated by the pressure releasing, but without changing the preceding impact force resulting from the liquid-liquid collision or the liquid-wall collision in the high-pressure narrow space. One old example of the dispersion apparatus of this type is a Golline homogenizer. In this apparatus, a liquid to be dispersed introduced under high pressure is converted into a high-speed flow when it is passed through a narrow gap formed on the wall of a cylindrical surface. Then, the flow collides against a surrounding wall with its own force, and is emulsified and dispersed by the impact force. For the liquid-liquid collision mentioned above, for example, there can be mentioned a Y-type chamber of Microfluidizer, a spherical chamber utilizing a spherical check valve such as that described in JP-A-8-103642 mentioned below and so forth. For the liquid-wall collision, there can be mentioned a Z-type chamber of Microfluidizer and so forth. The pressure is generally 100 to 600 kg/cm², and the flow rate is generally a few meters/sec to 30 meters/sec. In order to increase the dispersion efficiency, some apparatuses are designed wherein the high flow rate area is so modified as to have a serrated configuration, thereby increasing the frequency of collision. Typical examples of such devices are Golline homogenizer, Microfluidizer from Microfluidex International Corporation, Microfluidizer from Mizuho Kogyo Co., Ltd., Nanomizer from Tokushu Kika Kogyo Co., Ltd and so forth. Other examples of such apparatuses are described in JP-A-8-238848, JP-A-8-103642 and U.S. Patent No. 4,533,254.

[0091] In dispersing process of the organic silver salt, dispersion having a desired grain size may be obtained by controlling the flow rate, the difference in the pressure before and after at the pressure releasing and the frequency of the processing. From viewpoints of photographic performance and the grain size, the flow rate is preferably from 200 to 600 m/sec and the difference in the pressure at the pressure releasing is preferably from 900 to 3,000 kg/cm², and more preferably, the flow rate is from 300 to 600 m/sec, and the difference in the pressure at the pressure releasing is from 1,500 to 3,000 kg/cm². The frequency of the dispersion processing may be appropriately chosen as required, and is usually from 1 to 10 times. From a viewpoint of productivity, the frequency is approximately from 1 to 3 times. The water dispersion under a high pressure is preferably not warmed at a high temperature from viewpoints of dispersibility and photographic performance. At a high temperature above 90°C, a grain size may readily become large and fog may be increased. Accordingly, the water dispersion is preferably kept at a temperature of from 5°C to 90°C, more preferably from 5°C to 80°C, particularly preferably from 5°C to 65°C, by using a cooling apparatus in a step before the conversion into a high-pressure and high-speed flow, or a step after the pressure release, or both of the steps. It is particularly effective to provide the cooling step at the time of dispersion under a high pressure of from 1,500 to 3,000 kg/cm². The cooling apparatus may be appropriately selected from a double pipe or triple pipe with a static mixer, a multi-tubular exchanger, a coiled heat exchanger and so forth depending on an amount of heat exchange to be reqired. The size, wall thickness or material of a pipe may be appropriately selected to increase heat exchange efficiency depending on an applied pressure. In addition, depending on an amount of heat exchange, a refrigerant used in the cooling apparatus may be a well water at 20°C or a chilled water at from 5 to 10°C cooled by a refrigerator, and if desired, a refrigerant such as ethylene glycol/water at -30°C may also be used.

[0092] The organic silver salt is dispersed into solid fine grains preferably in the presence of a dispersing aid. The dispersing aid can be selected from, for example, synthetic anion polymers such as polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, maleic acid monoester copolymer and acryloylmethylpropanesulfonic acid copolymer, semisynthetic anionic polymers such as carboxymethyl starch and carboxymethyl cellulose, anionic polymers such as alginic acid and pectic acid, anionic surfactants described in JP-A-52-92716, International Patent Publication WO88/04794 and so forth, the compounds described in JP-A-9-179243, known anionic, nonionic or cationic surface active agents, known polymers such as polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxypropyl cellulose and hydroxypropylmethyl cellulose, and naturally-occurring polymer compounds such as gelatin.

[0093] The dispersing aid is generally mixed with the organic silver salt in a form of powder or wet cake before the dispersing process, and fed as slurry into a dispersing apparatus. However, the dispersing aid may also be mixed with the organic silver salt beforehand, and then the mixture may be subjected to a treatment such as by heating or with a solvent to form an organic silver salt powder or wet cake. The pH may be controlled with a suitable pH modifier before, during or after the dispersing operation.

[0094] Other than the mechanical dispersion, the organic silver salt can be made into microparticles by roughly dispersing the salt in a solvent through pH control, and then changing the pH in the presence of a dispersing aid. For the operation, an organic solvent may be used as a solvent for the rough dispersion, and such organic solvent can be removed after the formation of grains.

[0095] The dispersion prepared can be stored with stirring to prevent precipitation of the grains during storage, or stored in a highly viscous state formed by means of a hydrophilic colloids (e.g., a jelly state formed with gelatin). Furthermore, the dispersion may contain a preservative in order to prevent proliferation of microorganisms during storage.

[0096] The organic silver salt prepared by a method for preparing organic silver salts is preferably dispersed in an aqueous solvent, and then mixed with an aqueous solution of a photosensitive silver salt to provide a coating solution for photosensitive image-forming media.

[0097] In advance of the dispersion operation, the stock solution is preferably roughly dispersed (preparatory dispersion). The rough dispersion may be performed using a known dispersion means (for example, a high-speed mixer, a homogenizer, a high-speed impact mill, a Banbary mixer, a homomixer, a kneader, a ball mill, a vibrating ball mill, a planetary ball mill, an attriter, a sand mill, a bead mill, a colloid mill, a jet mill, a roller mill, a trone mill or a high-speed stone mill). Other than the mechanical dispersion, the stock solution may be roughly dispersed in a solvent by controlling pH and thereafter formed into fine grains in the presence of a dispersion aid by changing pH. At this time, the solvent used for the rough dispersion may be an organic solvent. The organic solvent is usually removed after the completion of fine grain formation.

[0098] The dispersion thus obtained is then mixed with an aqueous photosensitive silver salt solution to produce a coating solution for photosensitive image-forming media. The coating solution enables the manufacture of a thermally processed image recording material exhibiting low haze and low fog, and having high sensitivity. When a photosensitive silver salt coexists at the time of dispersing process under a high-pressure by conversion into a high-speed flow, fog may increase and sensitivity may often highly decrease. Furthermore, when an organic solvent is used as a dispersion medium instead of water, haze and fog may increase and sensitivity may be likely to decrease. When a conversion method where a part of the organic silver salt in the dispersion is converted into a photosensitive silver salt is used instead of the method of mixing an aqueous photosensitive silver salt solution, sensitivity may be likely to decreased.

[0099] The above-described water dispersion obtained using conversion into high-speed flow under a high-pressure is substantially free of a photosensitive silver salt. The content thereof is 0.1 mole % or less based on the light insensitive organic silver salt, and the photosensitive silver salt is not added intentionally.

[0100] The grain size (volume weight average diameter) in the solid fine grain dispersion of organic silver salt can be determined by, for example, irradiating the solid fine grain dispersion dispersed in a solution with a laser ray and determining an autocorrelation function of the fluctuation of the scattered light on the basis of the change in time (volume weight average diameter). The solid fine grain dispersion preferably has an average grain size of 0.05 to 10.0 µm, more preferably from 0.1 to 5.0 µm, further preferably from 0.1 to 2.0 µm.

[0101] The organic silver salt solid fine grain dispersion preferably used in the present invention comprises at least an organic silver salt and water. The ratio of the organic silver salt to water is not particularly limited. The organic silver salt preferably accounts for from 5 to 50 weight %, more preferably from 10 to 30 weight % of the entire dispersion. A dispersing aid is preferably used as described above but it is preferably used in a minimum amount within the range suitable for attaining a minimum grain size, specifically, in an amount of from 1 to 30 weight %, more preferably from 3 to 15 weight %, based on the organic silver salt.

[0102] In the present invention, a photothermographic material may be produced by mixing an organic silver salt aqueous dispersion and a photosensitive silver salt aqueous dispersion. The mixing ratio of the organic silver salt and the photosensitive silver salt may be selected according to the purpose. However, the ratio of the photosensitive silver salt to the organic silver salt is preferably from 1 to 30 mole %, more preferably from 3 to 20 mole %, still more preferably from 5 to 15 mole %. In the mixing, two or more organic silver salt aqueous dispersions are preferably mixed with two or more photosensitive silver salt aqueous dispersions, so that the photographic properties can be controlled.

[0103] The organic silver salt may be used in any desired amount in the present invention. However, it is preferably used in an amount of from 0.1 to 5 g/m², more preferably from 1 to 3 g/m², in terms of silver.

[0104] The thermally processed image recording material of the invention contains a reducing agent for the organic silver salt. The reducing agent for the organic silver salt may be any substance capable of reducing silver ions into silver, but is preferably an organic substance. Some examples of the reducing agent are described in JP-A-11-65021, paragraphs 0043 to 0045 and EP 0803764A1, from page 7, line 34 to page 18, line 12. Especially preferred for use in the present invention are bisphenol-type reducing agents (e.g., 1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane ). The amount of the reducing agent is preferably from 0.01 to 5.0 g/m², more preferably from 0.1 to 3.0 g/m². The amount of the reducing agent is preferably 5 to 50 mole %, more preferably 10 to 40 mole %, per mole of silver in the image-forming layer. The reducing agent is preferably contained in the image-forming layer.

[0105] The reducing agent used in the invention is preferably added in the form of a dispersion of solid microparticles. The microparticle dispersion of the reducing agent may be prepared in any known means for preparing fine particles (e.g., ball mill, vibration ball mill, sand mill, colloid mill, jet mill, roller mill etc.). A dispersing aid may be used in preparing the solid microparticle dispersion.

[0106] The thermally processed image recording material of the present invention is preferably a photothermographic material which further contains a photosensitive silver halide. The photosensitive silver halide that can be used for the present invention is not particularly limited as for the halogen composition, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide, and silver chloroiodobromide may be used. The halide composition may have a uniform distribution in the grains, or the compositions may change stepwise or continuously in the grains. Silver halide grains having a core/shell structure may be preferably used. Core/shell grains having preferably a double to quintuple structure, more preferably a double to quadruple structure may be used. A technique for localizing silver bromide on the surface of silver chloride or silver chlorobromide grains may also be preferably used.

[0107] For the preparation of the photosensitive silver halide, methods well known in the art, e.g., the methods described in Research Disclosure, No. 17029 (June, 1978) and U.S. Patent No. 3,700,458, can be used. More specifically, applicable methods for the present invention include a method comprising the step of preparing photosensitive silver halide grains by adding a silver-supplying compound and a halogen-supplying compound to a solution of gelatin or another polymer and then mixing the prepared grains with an organic silver salt.

[0108] As for a grain size of the photosensitive silver halide, smaller grains are desirable to prevent cloudiness of the photosensitive material after image formation. Specifically, the grain size may preferably be not greater than 0.20 µm, preferably from 0.01 to 0.15 µm, more preferably from 0.02 to 0.12 µm. The term "grain size" used herein means a diameter of a sphere having the same volume as the grain where the silver halide grains are regular crystals in cubic or octahedral form and where the silver halide grains are irregular crystals such as spherical or rod-like grains. Where silver halide grains are tabular grains, the term means the diameter of a circle having the same area as a projected area of the main surface of the tabular grain.

[0109] Examples of the form of silver halide grains include a cubic form, octahedral form, tabular form, spherical form, rod-like form and potato-like form. In particular, cubic grains are preferred for the present invention. Silver halide grains having round corners are also preferably used in the present invention. Surface index (Miller index) of outer surfaces of the photosensitive silver halide grains is not particularly limited. However, it is desirable that [100] face be present in a high proportion that can achieve high spectral sensitizing efficiency when a spectral sensitizing dye adsorbed thereto. The proportion of [100] face may be preferably not lower than 50%, more preferably at least 65%, still more preferably at least 80%. The proportion of Miller index [100] face can be determined using the method described in T. Tani, J. Imaging Sci., 29, 165 (1985), where the difference in adsorption of a sensitizing dye to [111] face and [100] face is utilized.

[0110] The photosensitive silver halide grain used in the present invention contains a metal or metal complex of Group VIII to Group X in the periodic table of elements (including Group I to Group XVIII). The metal or the center metal of the metal complex of Group VIII to X of the periodic table is preferably rhodium, rhenium, ruthenium, osmium or iridium. The metal complex may be used alone, or two or more complexes of the same or different metals may also be used in combination. The metal complex content is preferably from 1 × 10^-9 to 1 × 10^-3 mole per mole of silver. Such metal complexes are described in JP-A-11-65021, paragraphs 0018 to 0024.

[0111] In the present invention, an iridium compound is preferably contained in the silver halide grains. Examples of the iridium compound include hexachloroiridium, hexammineiridium, trioxalatoiridium, hexacyanoiridium and pentachloronitrosyliridium. The iridium compound is used after dissolving it in water or an appropriate solvent, and a method commonly used for stabilizing the iridium compound solution, more specifically, a method comprising adding an aqueous solution of hydrogen halogenide (e.g., hydrochloric acid, bromic acid, fluoric acid) or halogenated alkali (e.g., KCl, NaCl, KBr, NaBr) may be used. In place of using a water-soluble iridium, separate silver halide grains previously doped with iridium may be added and dissolved at the time of preparation of silver halide. The addition amount of the iridium compound is preferably 1 × 10^-8 to 1 × 10^-3 mole, more preferably 1 × 10^-7 to 5 × 10^-4 mole, per mole of silver halide.

[0112] Further, metal complexes that can be contained in the silver halide grains used for the present invention (e.g., [Fe(CN)₆]^4-), desalting methods and chemical sensitization method are described in JP-A-11-84574, paragraphs 0046 to 0050 and JP-A-11-65021, paragraphs 0025 to 0031.

[0113] In the thermally processed image recording material of the present invention, one kind of photosensitive silver halide emulsion may be used or two or more kinds of photosensitive silver halide emulsions (for example, those different in the average grain size, different in the halogen composition, different in the crystal habit or different in the chemical sensitization conditions) may be used in combination. By using a plurality of kinds of photosensitive silver halides different in sensitivity, contrast can be controlled. Examples of the techniques concerning these aspects includes those mentioned in JP-A-57-119341, JP-A-53-106125, JP-A-47-3929, JP-A-48-55730, JP-A-46-5187, JP-A-50-73627, JP-A-57-150841 and so forth. Sensitivity difference among the emulsions is preferably 0.2 log E or more.

[0114] The addition amount of the photosensitive silver halide is preferably 0.03 to 0.6 g/m², more preferably 0.05 to 0.4 g/m², most preferably 0.1 to 0.4 g/m², in terms of the coated silver amount per 1 m² of the photosensitive material. The addition amount of the photosensitive silver halide is preferably from 0.01 to 0.5 mole, more preferably from 0.02 to 0.3 mole, still more preferably from 0.03 to 0.25 mole, per mole of the organic silver salt.

[0115] The method and conditions for mixing photosensitive silver halide and organic silver salt, which are prepared separately, are not particularly limited so long as the effect of the present invention can be attained satisfactorily. However, a method of mixing the silver halide grains and the organic silver salt after completion of respective preparations in a high-speed stirring machine, a ball mill, a sand mill, a colloid mill, a vibrating mill or a homogenizer or the like, or a method involving preparing organic silver salt while mixing therewith light-sensitive silver halide after completion of the preparation in any timing during preparation of the organic silver salt, or the like may be used.

[0116] Preferred addition time point for the silver halide into the coating solution for image-forming layer resides in a period of from 180 minutes before the coating to immediately before the coating, preferably 60 minutes to 10 seconds before the coating. The method and conditions for mixing are not particularly limited so long as the effect of the present invention can be attained satisfactorily. Specific examples of the mixing method include a method in which the mixing is performed in a tank designed so that a desired average residence time therein can be obtained, which residence time is calculated from addition flow rate and feeding amount to a coater, a method utilizing a static mixer described in N. Harnby, M.F. Edwards, A.W. Nienow, "Ekitai Kongo Gijutsu (Techniques for Mixing Liquids)", translated by Koji Takahashi, Chapter 8, Nikkan Kogyo Shinbunsha, 1989 and so forth.

[0117] The thermally processed image recording material of the present invention contains a binder. The binder used for the present invention will be explained below.

[0118] The performance of the thermally processed image recording material of the present invention is improved if the layer containing an organic silver salt is formed by applying a coating solution comprising 30% by weight or more of water as to the total solvent and drying it, and if the binder of the layer containing an organic silver salt comprises a polymer latex soluble or dispersible in an aqueous solvent (water solvent) and showing an equilibrated moisture content of 2 weight % or less at 25°C and relative humidity of 60%. In the most preferred embodiment, the polymer latex is prepared to have an ion conductivity of 2.5 mS/cm or less. As a method for preparing such polymer latex, there can be mentioned a method comprising synthesizing a polymer and purifying it by using a functional membrane for separation.

[0119] The aqueous solvent in which the polymer binder is soluble or dispersible is water or a mixed solvent of water and 70% by weight or less of a water-miscible organic solvent. Examples of the water-miscible organic solvent include, for example, alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol; cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; ethyl acetate, dimethylformamide and so forth.

[0120] The terminology "aqueous solvent" referred to herein is also used for systems in which the polymer is not thermodynamically dissolved but is present in a so-called dispersed state.

[0121] The "equilibrated moisture content at 25°C and relative humidity of 60%" referred to herein for polymer latex is represented by the following equation, in which W1 indicates the weight of a polymer in humidity-conditioned equilibrium at 25°C and relative humidity of 60%, and W0 indicates the absolute dry weight of the polymer at 25°C.

[0122] For the details of the definition of moisture content and the method for measuring it, for example, there can be referred Lecture of Polymer Engineering, 14, Test Methods for Polymer Materials (Polymer Society of Japan, Chijin Shokan).

[0123] The equilibrated moisture content at 25°C and relative humidity of 60% of the binder polymer used for the present invention is preferably 2% by weight or less, more preferably from 0.01 to 1.5% by weight, even more preferably from 0.02 to 1% by weight.

[0124] In the present invention, polymers dispersible in aqueous solvents are particularly preferred.

[0125] Examples of the dispersed state include, for example, that of a polymer latex in which fine solid particles of polymer are dispersed, that in which a polymer is dispersed in a molecular state or as micelles and so forth. All of them are preferred.

[0126] In preferred embodiments of the invention, hydrophobic polymers such as acrylic resins, polyester resins, rubber resins (e.g., SBR resins), polyurethane resins, polyvinyl chloride resins, polyvinyl acetate resins, polyvinylidene chloride resins and polyolefin resins can preferably be used. The polymers may be linear, branched or crosslinked. They may be so-called homopolymers in which a single kind of monomer is polymerized, or copolymers in which two or more different kinds of monomers are polymerized. The copolymers may be random copolymers or block copolymers. The polymers may have a number average molecular weight of 5000 to 1000000, preferably from 10000 to 200000. Polymers having a too small molecular weight suffer from insufficient mechanical strength of the emulsion layer, and those having a too large molecular weight suffer from bad film forming property. Therefore, the both are not preferred.

[0127] The "aqueous solvent" mentioned above refers to a dispersion medium of which composition comprises at least 30% by weight of water. As for the dispersion condition, those in any condition may be used, including, for example, emulsion dispersion, micellar dispersion, molecular dispersion of a polymer having a hydrophilic moiety in the molecule and so forth. Among those, polymer latex is particularly preferred.

[0128] Preferred examples of the polymer latex are mentioned below. They are expressed with the constituent monomers. The numerals parenthesized indicate the contents in terms of % by weight. The molecular weights are number average molecular weights.

P-1: Latex of -MMA(70)-EA(27)-MAA(3)- (molecular weight: 37000)

P-2: Latex of -MMA(70)-2EHA(20)-St(5)-AA(5)- (molecular weight: 40000)

P-3: Latex of -St(50)-Bu(47)-MMA(3)- (molecular weight: 45000)

P-4: Latex of -St(68)-Bu(29)-AA(3)- (molecular weight: 60000)

P-5: Latex of -St(70)-Bu(27)-IA(3)- (molecular weight: 120000)

P-6: Latex of -St(75)-Bu(24)-AA(1)- (molecular weight: 108000)

P-7: Latex of -St(60)-Bu(35)-DVB(3)-MAA(2)- (molecular weight: 150000)

P-8: Latex of -St(70)-Bu(25)-DVB(2)-AA(3)- (molecular weight: 280000)

P-9: Latex of -VC(50)-MMA(20)-EA(20)-AN(5)-AA(5)- (molecular weight: 80000)

P-10: Latex of -VDC(85)-MMA(5)-EA(5)-MAA(5)- (molecular weight: 67000)

P-11: Latex of -Et(90)-MAA(10)- (molecular weight: 12000)

P-12: Latex of -St(70)-2EHA(27)-AA(3)- (molecular weight: 130000)

P-13: Latex of -MMA(63)-EA(35)-AA(2)- (molecular weight: 33000)

[0129] Abbreviations used for the constituent monomers are as follows:

MMA:

methyl methacrylate

EA:

ethyl acrylate

MAA:

methacrylic acid

2EHA:

2-ethylhexyl acrylate

St:

styrene

Bu:

butadiene

AA:

acrylic acid

DVB:

divinylbenzene

VC:

vinyl chloride

AN:

acrylonitrile

VDC:

vinylidene chloride

Et:

ethylene

IA:

itaconic acid

[0130] The polymer latexes mentioned above are also commercially available, and those mentioned below can be used, for example. Examples of acrylic resins are CEBIAN A-4635, 46583, 4601 (all from Daicel Chemical Industries), Nipol Lx811, 814, 821, 820, 857 (all from Nippon Zeon) etc.; examples of polyester resins are FINETEX ES650, 611, 675, 850 (all from Dai-Nippon Ink & Chemicals), WD-size, WMS (both from Eastman Chemical) etc.; examples of polyurethane resins are HYDRAN AP10, 20, 30, 40 (all from Dai-Nippon Ink & Chemicals) etc.; examples of rubber resins are LACSTAR 7310K, 3307B, 4700H, 7132C (all from Dai-Nippon Ink & Chemicals), Nipol Lx416, 410, 438C, 2507 (all from Nippon Zeon) etc.; examples of polyvinyl chloride resins are G351, G576 (both from Nippon Zeon) etc.; examples of polyvinylidene chloride resins are L502, L513 (both from Asahi Chemical Industry) etc.; examples of polyolefin resins are CHEMIPEARL S120, SA100 (both from Mitsui Petrochemical) etc.

[0131] These polymer latexes may be used each alone, or two or more kinds of them may be blended as required.

[0132] As the polymer latex used in the present invention, styrene/butadiene copolymer latex is particularly preferred. In the styrene/butadiene copolymer, the weight ratio of styrene monomer units to butadiene monomer units is preferably 40/60 to 95/5. The ratio of the styrene monomer units and the butadiene monomer units preferably account for from 60 to 99% by weight of the copolymer. The preferred range of the molecular weight of the copolymer is similar to that mentioned above.

[0133] Examples of styrene/butadiene copolymer latexes preferably used for the present invention include the aforementioned P-3 to P-8, commercially available products, LACSTAR-3307B, 7132C, Nipol Lx416 and so forth.

[0134] The layer containing organic silver salt of the thermally processed image recording material of the invention may optionally contain a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose and hydroxypropyl cellulose. The addition amount of the hydrophilic polymer is preferably 30% by weight or less, more preferably 20% by weight or less, of the total binder in the layer containing organic silver salt.

[0135] The layer containing organic silver salt (that is, the image-forming layer) of the thermally processed image recording material of the invention is preferably formed by using polymer latex. The amount of the binder in the layer containing organic silver salt is such an amount that the weight ratio of total binder/organic silver salt should be 1/10 to 10/1, more preferably 1/5 to 4/1.

[0136] The layer containing organic silver salt usually also serves as a photosensitive layer (emulsion layer) containing a photosensitive silver salt, that is, a photosensitive silver halide. In such a case, the weight ratio of total binder/silver halide is preferably 5 to 400, more preferably 10 to 200.

[0137] The total amount of the binder in the image-forming layer is preferably 0.2 to 30 g/m², more preferably 1 to 15 g/m². The image-forming layer may optionally contain a crosslinking agent, a surfactant for improving coating property of the coating solution and so forth.

[0138] The solvent for the coating solution for the layer containing organic silver salt of the thermally processed image recording material of the invention (for simplicity, solvents and dispersion media are collectively referred to as solvent) is an aqueous solvent containing at least 30% by weight of water. As for components other than water, any water-miscible organic solvents including, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, ethyl acetate and so forth may be used. The water content of the solvent for the coating solution is preferably at least 50% by weight, more preferably at least 70% by weight. Preferred examples of the solvent composition are water, water/methyl alcohol = 90/10, water/methyl alcohol = 70/30, water/methyl alcohol/dimethylformamide = 80/15/5, water/methyl alcohol/ethyl cellosolve = 80/10/5, water/methyl alcohol/isopropyl alcohol = 85/10/5 and so forth (numerals indicate weight %).

[0139] As a sensitizing dye that can be used for the present invention, there can be advantageously selected those sensitizing dyes which can spectrally sensitize silver halide grains within a desired wavelength range after they are adsorbed by the silver halide grains and have spectral sensitivity suitable for spectral characteristics of the light source to be used for exposure. Such sensitizing dyes and addition methods therefor are described in JP-A-11-65021, paragraphs 0103 to 0109 and EP 0803764A1, page 19, line 38 to page 20, line 35, and there can be mentioned the compounds of formula (II) described in JP-A-10-186572. The sensitizing dye is added to the silver halide emulsion preferably during the period after the desalting step and before the coating step, more preferably during the period after the desalting step and before the start of the chemical ripening.

[0140] As antifoggants, stabilizers and stabilizer precursors that can be used for the present invention, there can be mentioned, for example, those mentioned in JP-A-10-62899, paragraph 0070 and EP 0803764A1, from page 20, line 57 to page 21, line 7. Antifoggants preferably used for the present invention are organic halides. Examples thereof include, for example, those disclosed in JP-A-11-65021, paragraphs 0111 to 0112. Particularly preferred are the compounds of formula (II) mentioned in JP-A-10-339934 (specific examples are tribromomethylnaphthylsulfone, tribromomethylphenylsulfone, tribromomethyl(4-(2,4,6-trimethylsulfonyl)phenyl)sulfone, etc.).

[0141] The antifoggant is preferably added in the form of a solid microparticle dispersion. The solid microparticle dispersion is performed by using a known pulverizing means (e.g., a ball mill, a vibration ball mill, a sand mill, a colloid mill, a jet mill, a roller mill). At the time of solid microparticle dispersion, a dispersing aid such as anionic surfactant (e.g., sodium triisopropylnaphthalenesulfonate (mixture of those having three isopropyl groups on different positions)) may be used.

[0142] Other examples of the antifoggant include the mercury(II) salts described in JP-A-11-65021, paragraph 0113 and the benzoic acids described in the same, paragraph 0114.

[0143] The thermally processed image recording material of the invention may contain an azolium salt as the antifoggant. Examples of the azolium salt include, for example, the compounds of the formula (XI) described in JP-A-59-193447, the compounds described in JP-B-55-12581 and the compounds of the formula (II) described in JP-A-60-153039. The azolium salt may be present in any site of the thermally processed image recording material, but is preferably in a layer on the photosensitive layer side, more preferably in the layer containing organic silver salt. The azolium salt may be added at any time during the preparation of the coating solution. When the azolium salt is added to the layer containing organic silver salt, it may be added at any time during the period of from the preparation of the organic silver salt to the preparation of the coating solution. The azolium salt is preferably added during the period after the preparation of the organic silver salt and immediately before the coating. The azolium salt may be added in any form such as powder, solution and microparticle dispersion. It may also be added as a solution that also contains other additives such as sensitizing dye, reducing agent and color tone adjuster. In the present invention, the amount of the azolium salt to be added is not particularly limited, but it is preferably 1 × 10^-6 mole to 2 moles, more preferably 1 × 10^-3 mole to 0.5 mole, per mole of silver.

[0144] The thermally processed image recording material of the invention may optionally contain any of mercapto compounds, disulfide compounds and thione compounds in order to control development by retarding or accelerating it, or enhance spectral sensitivity, or improve storage stability before and after development. Examples of those compounds include, for example, those described in JP-A-10-62899, paragraphs 0067 to 0069, those of the formula (I) mentioned in JP-A-10-186572 and those mentioned in the paragraphs 0033 to 0052 of the same as specific examples, and those described in EP 0803764A1, page 20, lines 36 to 56. Among these, preferred are mercapto-substituted heteroaromatic compounds.

[0145] In the present invention, it is preferable to add a color tone adjuster. Examples of the color tone adjuster are mentioned in JP-A-10-62899, paragraphs 0054 to 0055 and EP 0803764A1, page 21, lines 23 to 48. Preferred are phthalazinone, phthalazinone derivatives (e.g., 4-(1-naphthyl)phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone, 2,3-dihydro-1,4-phthalazinone and other derivatives) and metal salts thereof; combinations of phthalazinones and phthalic acid or derivatives thereof (e.g., phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride etc.); phthalazines including phthalazine and phthalazine derivatives (e.g., 4-(1-naphthyl)phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine, 2,3-dihydrophthalazine and other derivatives) and metal salts thereof; combinations of phthalazines and phthalic acid or derivatives thereof (e.g., phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride etc.). Particularly preferred are combinations of phthalazines and phthalic acid or derivatives thereof.

[0146] Plasticizers and lubricants that can be used in the present invention for the photosensitive layer are described in JP-A-11-65021, paragraph 0117; ultrahigh contrast agents for forming ultrahigh contrast images are described in the same but in paragraph 0118; and hardness enhancement promoters are described in the same but in paragraph 0102.

[0147] The thermally processed image recording material of the present invention may preferably contain, as an ultrahigh contrast agent, one or more substituted alkene derivatives, substituted isooxazole derivatives, and specific acetal compounds represented by the following formulas (2) to (4), respectively.

[0148] The compounds of the formulas (2), (3) and (4) will be explained below.

[0149] In the formula (2), R¹, R² and R³ each independently represents a hydrogen atom or a substituent, and Z represents an electron withdrawing group or a silyl group. R¹ together with Z, R² together with R³, R¹ together with R², or R³ together with Z may be combined with each other to form a ring structure. In the formula (3), R⁴ represents a substituent; and in the formula (4), X and Y independently represent a hydrogen atom or a substituent, A and B independently represent an alkoxyl group, an alkylthio group, an alkylamino group, an aryloxy group, an arylthio group, an anilino group, a heterocyclyloxy group, a heterocyclylthio group or a heterocyclylamino group, and X together with Y, or A together with B may be combined with each other to form a ring structure.

[0150] The compound represented by the formula (2) will be explained in detail below.

[0151] In the formula (2), R¹, R² and R³ independently represent a hydrogen atom or a substituent, and Z represents an electron withdrawing group or a silyl group. In the formula (2), R¹ together with Z, R² together with R³, R¹ together with R², or R³ together with Z may be combined with each other to form a ring structure.

[0152] When R¹, R² or R³ represents a substituent, examples of the substituent include a halogen atom (e.g., fluorine, chlorine, bromide, iodine), an alkyl group (including a cycloalkyl group and active methine group), an aralkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group (including N-substituted nitrogen-containing heterocyclic group), a quaternized nitrogen-containing heterocyclic group (e.g., pyridinio group), an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, carboxyl group or a salt thereof, an imino group, an imino group substituted at N atom, a thiocarbonyl group, a sulfonylcarbamoyl group, an acylcarbamoyl group, a sulfamoylcarbamoyl group, a carbazoyl group, an oxalyl group, an oxamoyl group, cyano group, a thiocarbamoyl group, hydroxyl group or a salt thereof, an alkoxyl group (including a group containing ethyleneoxy group or propyleneoxy group repeating unit), an aryloxy group, a heterocyclyloxy group, an acyloxy group, an (alkoxyl or aryloxy)carbonyloxy group, a carbamoyloxy group, a sulfonyloxy group, an amino group, a substituted amino group (alkyl-, aryl- or heterocyclyl-substituted amino group etc.), an acylamino group, a sulfonamido group, a ureido group, a thioureido group, an imido group, an (alkoxyl or aryloxy)carbonylamino group, a sulfamoylamino group, a semicarbazide group, a thiosemicarbazide group, a hydrazino group, a quaternary ammonio group, an oxamoylamino group, an (alkyl or aryl)sulfonylureido group, an acylureido group, an acylsulfamoylamino group, nitro group, mercapto group, a substituted thio group (alkyl-, aryl- or heterocyclyl-substituted thio group etc.), an acylthio group, an (alkyl or aryl)sulfonyl group, an (alkyl or aryl)sulfinyl group, sulfo group or a salt thereof, a sulfamoyl group, an acylsulfamoyl group, a sulfonylsulfamoyl group or a salt thereof, a phosphoryl group, a group containing phosphoramide or phosphoric acid ester structure, a silyl group and a stannyl group.

[0153] These substituents may further be substituted with any one or more of the above-described substituents.

[0154] The electron withdrawing group represented by Z in the formula (2) is a substituent that gives a positive value of the Hammett's substituent constant σp, and specific examples include cyano group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an imino group, an imino group substituted at N atom, a thiocarbonyl group, a sulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group, nitro group, a halogen atom, a perfluoroalkyl group, a perfluoroalkanamido group, a sulfonamido group, an acyl group, a formyl group, a phosphoryl group, carboxyl group (or a salt thereof), sulfo group (or a salt thereof), a heterocyclic group, an alkenyl group, an alkynyl group, an acyloxy group, an acylthio group, a sulfonyloxy group, and an aryl group substituted with the above-described electron withdrawing group. The heterocyclic group mentioned above is a saturated or unsaturated heterocyclic group, and examples include a pyridyl group, a quinolyl group, a quinoxalinyl group, a pyrazinyl group, a benzotriazolyl group, an imidazolyl group, a benzimidazolyl group, a hydantoin-1-yl group, a succinimido group and a phthalimido group.

[0155] The electron withdrawing group represented by Z in the formula (2) may further have one or more substituents, and examples of such substituents include those described as the substituent on the groups represented by R¹, R² or R³ in the formula (2).

[0156] In the formula (2), R¹ together with Z, R² together with R³, R¹ together with R², or R³ together with Z may be combined with each other to form a ring structure. The ring structure formed is a non-aromatic carbocyclic ring or a non-aromatic heterocyclic ring.

[0157] The preferred scope of the compound represented by the formula (2) will be described below.

[0158] The silyl group represented by Z in the formula (2) may preferably be trimethylsilyl group, t-butyldimethylsilyl group, phenyldimethylsilyl group, triethylsilyl group, triisopropylsilyl group or trimethylsilyldimethylsilyl group.

[0159] The electron withdrawing group represented by Z in the formula (2) may preferably be a group having a total carbon atom number of 0 to 30 such as cyano group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, a thiocarbonyl group, an imino group, an imino group substituted at N atom, a sulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group, nitro group, a perfluoroalkyl group, an acyl group, a formyl group, a phosphoryl group, an acyloxy group, an acylthio group or a phenyl group substituted with one or more electron withdrawing groups, more preferably cyano group, an alkoxycarbonyl group, a carbamoyl group, an imino group, a sulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group, an acyl group, a formyl group, a phosphoryl group, a trifluoromethyl group, or a phenyl group substituted with one or more electron withdrawing group, and most preferably cyano group, a formyl group, an acyl group, an alkoxycarbonyl group, an imino group or a carbamoyl group.

[0160] The group represented by Z in the formula (2) is preferably an electron withdrawing group.

[0161] The substituent represented by R¹, R² or R³ in the formula (2) may preferably be a group having a total carbon atom number of 0 to 30, and specific examples of the group include a the same groups as those explained as the electron withdrawing group represented by Z in the formula (2), as well as an alkyl group, hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group, an amino group, an alkylamino group, an arylamino group, a heterocyclylamino group, a ureido group, an acylamino group, a sulfonamido group and a substituted or unsubstituted aryl group and the like.

[0162] In the formula (2), R¹ is preferably an electron withdrawing group, an aryl group, an alkylthio group, an alkoxyl group, an acylamino group, hydrogen atom, or a silyl group.

[0163] When R¹ represents an electron withdrawing group, the electron withdrawing group may preferably be a group having a total carbon atom number of 0 to 30 such as cyano group, nitro group, an acyl group, a formyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a thiocarbonyl group, an imino group, an imino group substituted at N atom, an alkylsulfonyl group, an arylsulfonyl group, a carbamoyl group, a sulfamoyl group, a trifluoromethyl group, a phosphoryl group, carboxyl group (or a salt thereof), a saturated or unsaturated heterocyclic group, more preferably cyano group, an acyl group, a formyl group, an alkoxycarbonyl group, a carbamoyl group, an imino group, an imino group substituted at N atom, a sulfamoyl group, carboxyl group (or a salt thereof) or a saturated or unsaturated heterocyclic group, and most preferably cyano group, a formyl group, an acyl group, an alkoxycarbonyl group, a carbamoyl group or a saturated or unsaturated heterocyclic group.

[0164] When R¹ represents an aryl group, the aryl group is preferably a substituted or unsubstituted phenyl group having a total carbon atom number of from 6 to 30. The substituent may be any substituent, and an electron withdrawing substituent is preferred.

[0165] In the formula (2), R¹ is more preferably an electron withdrawing group or an aryl group.

[0166] The substituent represented by R² or R³ in the formula (2) may preferably be the same group as those explained as the electron withdrawing group represented by Z in the formula (2), as well as an alkyl group, hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group, an amino group, an alkylamino group, an anilino group, a heterocyclylamino group, an acylamino group or a substituted or unsubstituted phenyl group.

[0167] In the formula (2), it is more preferred that one of R² and R³ is hydrogen atom and the other is a substituent. The substituent may preferably be an alkyl group, hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group, an amino group, an alkylamino group, an anilino group, a heterocyclylamino group, an acylamino group (particularly, a perfluoroalkanamido group), a sulfonamido group, a substituted or unsubstituted phenyl group or a heterocyclic group, more preferably hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group or a heterocyclic group, and most preferably hydroxyl group (or a salt thereof), an alkoxyl group or a heterocyclic group.

[0168] In the formula (2), it is also preferred that Z together with R¹ or R² together with R³ form a ring structure. The ring structure formed is a non-aromatic carbocyclic ring or a non-aromatic heterocyclic ring, preferably a 5-, 6- or 7-membered ring structure having a total carbon atom number, including those of substituents thereon, of 1 to 40, more preferably 3 to 30.

[0169] The compound represented by the formula (2) is more preferably a compound wherein Z represents cyano group, a formyl group, an acyl group, an alkoxycarbonyl group, an imino group or a carbamoyl group; R¹ represents an electron withdrawing group or an aryl group, and one of R² and R³ represents hydrogen atom and the other represents hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group or a heterocyclic group.

[0170] A class of most preferable compounds represented by the formula (2) are constituted by those wherein Z and R¹ form a non-aromatic 5-, 6- or 7-membered ring structure, and one of R² and R³ represents hydrogen atom and the other represents hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group or a heterocyclic group. In such a compound, Z which forms a non-aromatic ring structure together with R¹ is preferably an acyl group, a carbamoyl group, an oxycarbonyl group, a thiocarbonyl group or a sulfonyl group, and R¹ is preferably an acyl group, a carbamoyl group, an oxycarbonyl group, a thiocarbonyl group, a sulfonyl group, an imino group, an imino group substituted at N atom, an acylamino group or a carbonylthio group.

[0171] The compound represented by the formula (3) will be described below.

[0172] In the formula (3), examples of the substituent represented by R⁴ include those explained as the substituent represented by R¹, R² or R³ in the formula (2).

[0173] The substituent represented by R⁴ in the formula (3) may preferably be an electron withdrawing group or an aryl group. Where R⁴ represents an electron withdrawing group, the electron withdrawing group may preferably be a group having a total carbon atom number of 0 to 30, such as cyano group, nitro group, an acyl group, a formyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkylsulfonyl group, an arylsulfonyl group, a carbamoyl group, a sulfamoyl group, a trifluoromethyl group, a phosphoryl group, an imino group or a saturated or unsaturated heterocyclic group, more preferably cyano group, an acyl group, a formyl group, an alkoxycarbonyl group, a carbamoyl group, a sulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group or a heterocyclic group, and most preferably cyano group, a formyl group, an acyl group, an alkoxycarbonyl group, a carbamoyl group or a heterocyclic group.

[0174] Where R⁴ represents an aryl group, the aryl group may preferably be a substituted or unsubstituted phenyl group having a total carbon atom number of 0 to 30. Examples of the substituent include those described as the substituent represented by R¹, R² or R³ in the formula (2).

[0175] R⁴ in the formula (3) is most preferably cyano group, an alkoxycarbonyl group, a carbamoyl group, a heterocyclic group or a substituted or unsubstituted phenyl group, and most preferably cyano group, a heterocyclic group or an alkoxycarbonyl group.

[0176] The compound represented by the formula (4) will be described in detail below.

[0177] In the formula (4), X and Y independently represent hydrogen atom or a substituent, and A and B independently represent an alkoxyl group, an alkylthio group, an alkylamino group, an aryloxy group, an arylthio group, an anilino group, a heterocyclylthio group, a heterocyclyloxy group or a heterocyclylamino group, and X together with Y or A together with B may be combined with each other to form a ring structure.

[0178] Examples of the substituent represented by X or Y in the formula (4) include those described as the substituent represented by R¹, R² or R³ in the formula (2). Specific examples include an alkyl group (including a perfluoroalkyl group and a trichloromethyl group), an aryl group, a heterocyclic group, a halogen atom, cyano group, nitro group, an alkenyl group, an alkynyl group, an acyl group, a formyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an imino group, an imino group substituted at the nitrogen atom, a carbamoyl group, a thiocarbonyl group, an acyloxy group, an acylthio group, an acylamino group, an alkylsulfonyl group, an arylsulfonyl group, a sulfamoyl group, a phosphoryl group, carboxyl group (or a salt thereof), sulfo group (or a salt thereof), hydroxyl group (or a salt thereof), mercapto group (or a salt thereof), an alkoxyl group, an aryloxy group, a heterocyclyloxy group, an alkylthio group, an arylthio group, a heterocyclylthio group, an amino group, an alkylamino group, an anilino group, a heterocyclylamino group, a silyl group and the like.

[0179] These groups may further have one or more substituents. X together with Y may be combined with each other to form a ring structure, and the ring structure formed may be either a non-aromatic carbocyclic ring or a non-aromatic heterocyclic ring.

[0180] In the formula (4), the substituent represented by X or Y may preferably be a substituent having a total carbon number of from 1 to 40, more preferably from 1 to 30, such as cyano group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an imino group, an imino group substituted at the nitrogen atom, a thiocarbonyl group, a sulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group, nitro group, a perfluoroalkyl group, an acyl group, a formyl group, a phosphoryl group, an acylamino group, an acyloxy group, an acylthio group, a heterocyclic group, an alkylthio group, an alkoxyl group or an aryl group.

[0181] In the formula (4), X and Y are more preferably cyano group, nitro group, an alkoxycarbonyl group, a carbamoyl group, an acyl group, a formyl group, an acylthio group, an acylamino group, a thiocarbonyl group, a sulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group, an imino group, an imino group substituted at the nitrogen atom, a phosphoryl group, a trifluoromethyl group, a heterocyclic group , a substituted phenyl group or the like, most preferably cyano group, an alkoxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, an arylsulfonyl group, an acyl group, an acylthio group, an acylamino group, a thiocarbonyl group, a formyl group, an imino group, an imino group substituted at the nitrogen atom, a heterocyclic group, a phenyl group substituted by any electron withdrawing group or the like.

[0182] X and Y may also be preferably combined with each other to form a non-aromatic carbocyclic ring or a non-aromatic heterocyclic ring. The ring structure formed is preferably a 5-, 6- or 7-membered ring having a total carbon atom number of 1 to 40, more preferably 3 to 30. X and Y for forming a ring structure are preferably an acyl group, a carbamoyl group, an oxycarbonyl group, a thiocarbonyl group, a sulfonyl group, an imino group, an imino group substituted at the nitrogen atom, an acylamino group, a carbonylthio group or the like.

[0183] In the formula (4), A and B independently represent an alkoxyl group, an alkylthio group, an alkylamino group, an aryloxy group, an arylthio group, an anilino group, a heterocyclylthio group, a heterocyclyloxy group or a heterocyclylamino group, which may be combined with each other to form a ring structure.

[0184] The substituents represented by A and B in the formula (4) are preferably a group having a total carbon atom number of 1 to 40, more preferably 1 to 30, and the group may further have one or more substituents.

[0185] In the formula (4), A and B are more preferably combined with each other to form a ring structure. The ring structure formed is preferably a 5-, 6- or 7-membered non-aromatic heterocyclic ring having a total carbon atom number of 1 to 40, more preferably 3 to 30. Examples of a structure (-A-B-) formed by the linking of A and B include -O-(CH₂)₂-O-, -O-(CH₂)₃-O-, -S-(CH₂)₂-S-, -S-(CH₂)₃-S-, -S-ph-S-, -N(CH₃)-(CH₂)₂-O-, -N(CH₃)-(CH₂)₂-S-, -O-(CH₂)₂-S-, -O-(CH₂)₃-S-, -N(CH₃)-ph-O-, -N(CH₃)-ph-S-, -N(ph)-(CH₂)₂-S- and the like.

[0186] The compound represented by the formula (2), (3) or (4) for use in the present invention may be introduced with an adsorbing group capable of adsorbing to silver halide. Examples of the adsorbing group include the groups described in U.S. Patent Nos. 4,385,108 and 4,459,347, JP-A-59-195233, JP-A-59-200231, JP-A-59-201045, JP-A-59-201046, JP-A-59-201047, JP-A-59-201048, JP-A-59-201049, JP-A-61-170733, JP-A-61-270744, JP-A-62-948, JP-A-63-234244, JP-A-63-234245 and JP-A-63-234246, such as an alkylthio group, an arylthio group, a thiourea group, a thioamide group, a mercaptoheterocyclic group and a triazole group. The adsorbing group to silver halide may be formed as a precursor. Examples of the precursor include the groups described in JP-A-2-285344.

[0187] The compound represented by the formula (2), (3) or (4) for use in the present invention may be introduced with a ballast group or a polymer commonly used in the field of immobile photographic additives such as a coupler. The compounds incorporated with the ballast group may be preferred for the present invention. The ballast group is a group having 8 or more carbon atoms and being relatively inactive in the photographic performance. Examples of the ballast group include an alkyl group, an aralkyl group, an alkoxyl group, a phenyl group, an alkylphenyl group, a phenoxy group, an alkylphenoxy group and the like. Examples of the polymer include those described in JP-A-1-100530 and the like.

[0188] The compound represented by the formula (2), (3) or (4) for use in the present invention may contain a cationic group (specifically, a group containing a quaternary ammonio group or a nitrogen-containing heterocyclic group containing a quaternized nitrogen atom), a group containing an ethyleneoxy group or a propyleneoxy group as a repeating unit, an (alkyl, aryl or heterocyclic)thio group, or a dissociative group capable of dissociation by a base (e.g., carboxyl group, sulfo group, an acylsulfamoyl group, a carbamoylsulfamoyl group), preferably a group containing an ethyleneoxy group or a propyleneoxy group as a repeating unit, or an (alkyl, aryl or heterocyclic)thio group. Specific examples of these groups include the compounds described in JP-A-7-234471, JP-A-5-333466, JP-A-6-19032, JP-A-6-19031, JP-A-5-45761, U.S. Patent Nos. 4,994,365 and 4,988,604, JP-A-3-259240, JP-A-7-5610, JP-A-7-244348 and German Patent No. 4,006,032.

[0189] Specific examples of the compounds represented by the formulas (2) to (4) for use in the present invention are shown below. However, the scope of the present invention is not limited to the following compounds.

[0190] The compounds represented by the formulas (2) to (4) for use in the present invention may be used after being dissolved in water or an appropriate organic solvent such as an alcohol (e.g., methanol, ethanol, propanol, fluorinated alcohol), a ketone (e.g., acetone, methyl ethyl ketone), dimethylformamide, dimethyl sulfoxide or methyl cellosolve.

[0191] The compounds may also be used as an emulsified dispersion mechanically prepared according to an already well known emulsification dispersion method by using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, ethyl acetate or cyclohexanone as an auxiliary solvent for dissolution. Alternatively, the compounds may be used after dispersion of a powder in a suitable solvent such as water by using a ball mill, a colloid mill or the like, or by means of ultrasonic wave according to a known method for solid dispersion.

[0192] The compounds represented by the formulas (2) to (4) for use in the present invention may be added to any layers on a support provided at the side of the image-forming layer, i.e., the image-forming layer and/or the other layers provided on the same side. The compounds may preferably be added to the image-forming layer and a layer adjacent thereto.

[0193] The amount of the compounds represented by the formulas (2) to (4) for use in the present invention is preferably from 1 × 10^-6 to 1 mole, more preferably from 1 × 10^-5 to 5 × 10^-1 mole, most preferably from 2 × 10^-5 to 2 × 10^-1 mole per mole of silver.

[0194] The compounds represented by formulas (2) to (4) can be easily synthesized according to known methods. For example, the compounds may be synthesized by referring to the methods described in U.S. Patent Nos. 5,545,515, 5,635,339 and 5,654,130, International Patent Publication WO97/34196 or Japanese Patent Application Nos. 9-354107, JP-A-11-133546, JP-A-11-95365.

[0195] The compounds represented by the formulas (2) to (4) may be used alone or in combination of two or more compounds. In addition to these compounds, any of the compounds described in U.S. Patent Nos. 5,545,515, 5,635,339 and 5,654,130, International Patent Publication WO97/34196, U.S. Patent No. 5,686,228 or Japanese Patent Application Nos. 9-228881, JP-A-11-119372, Japanese Patent Application Nos. 9-354107, JP-A-11-133546, JP-A-11-119373, JP-A-11-109546, JP-A-11-95365, JP-A-11-95366, JP-A-11-149136 may also be used in combination.

[0196] Furthermore, in the present invention, the hydrazine derivatives described in JP-A-10-339932 and JP-A-10-161270 may be used in combination. In addition, the following hydrazine derivatives may also be used in combination: the compounds represented by (Chem. 1) of JP-B-6-77138, specifically, compounds described at pages 3 and 4 of the publication; the compounds represented by the formula (I) of JP-B-6-93082, specifically, Compounds 1 to 38 described at pages 8 to 18 of the publication; the compounds represented by the formulas (4), (5) and (6) of JP-A-6-230497, specifically, Compounds 4-1 to 4-10 described at pages 25 and 26, Compounds 5-1 to 5-42 described at pages 28 to 36 and Compounds 6-1 to 6-7 described at pages 39 and 40 of the publication; the compounds represented by the formulas (1) and (2) of JP-A-6-289520, specifically, Compounds 1-1) to 1-17) and 2-1) described at pages 5 to 7 of the publication; the compounds represented by (Chem. 2) and (Chem. 3) of JP-A-6-313936, specifically, compounds described at pages 6 to 19 of the publication; the compound represented by (Chem. 1) of JP-A-6-313951, specifically, the compounds described at pages 3 to 5 of the publication; the compound represented by the formula (I) of JP-A-7-5610, specifically, Compounds I-1 to I-38 described at pages 5 to 10 of the publication; the compounds represented by the formula (II) of JP-A-7-77783, specifically, Compounds II-1 to II-102 described at pages 10 to 27 of the publication; the compounds represented by the formulas (H) and (Ha) of JP-A-7-104426, specifically, Compounds H-1 to H-44 described at pages 8 to 15 of the publication; the compounds characterized by having in the vicinity of the hydrazine group an anionic group or a nonionic group capable of forming an intramolecular hydrogen bond with a hydrogen atom of hydrazine, described in EP713131A, particularly, the compounds represented by the formulas (A), (B), (C), (D), (E) and (F), specifically, Compounds N-1 to N-30 described in the publication; the compound represented by the formula (1) described in EP713131A, specifically, Compounds D-1 to D-55 described in the publication; various hydrazine derivatives described at pages 25 to 34 of Kochi Gijutsu (Known Techniques), pages 1 to 207, Aztech (issued on March 22, 1991); and Compounds D-2 and D-39 described in JP-A-62-86354 (pages 6 and 7).

[0197] These hydrazine derivatives for use in the present invention may be used after being dissolved in water or an appropriate organic solvent such as an alcohol (e.g., methanol, ethanol, propanol, fluorinated alcohol), a ketone (e.g., acetone, methyl ethyl ketone), dimethylformamide, dimethyl sulfoxide or methyl cellosolve.

[0198] The compounds may also be used as an emulsified dispersion mechanically prepared according to an already well known emulsification dispersion method by using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, ethyl acetate or cyclohexanone as an auxiliary solvent for dissolution. Alternatively, the compounds may be used after dispersion of a powder in water by using a ball mill, a colloid mill or the like, or by means of ultrasonic wave according to a known method for solid dispersion.

[0199] The hydrazine derivatives may be added to any layers on a support provided at the side of the image-forming layer, i.e., the image-forming layer and/or the other layers provided on the same side. The compounds may preferably be added to the image-forming layer and a layer adjacent thereto.

[0200] The amount of the hydrazine derivatives is preferably from 1 × 10^-6 to 1 mole, more preferably from 1 × 10^-5 to 5 × 10^-1 mole, most preferably from 2 × 10^-5 to 2 × 10^-1 mole per mole of silver.

[0201] In addition, the acrylonitrile compounds disclosed in U.S. Patent No. 5,545,515, more specifically the compounds CN-1 to CN-13 disclosed therein and the like may also be used as the ultrahigh contrast agent.

[0202] In the present invention, a contrast accelerator may be used in combination with the above-described ultrahigh contrast agent for the formation of an ultrahigh contrast image. For example, amine compounds described in U.S. Patent No. 5,545,505, specifically, AM-1 to AM-5; hydroxamic acids described in U.S. Patent No. 5,545,507, specifically, HA-1 to HA-11; hydrazine compounds described in U.S. Patent No. 5,558,983, specifically, CA-1 to CA-6; and onium salts described in JP-A-9-297368, specifically, A-1 to A-42, B-1 to B-27 and C-1 to C-14 may be used.

[0203] Methods for the preparation and the addition as well as amounts of the aforementioned contrast accelerators may be applied as described in the patent publications cited above.

[0204] The thermally processed image recording material of the present invention may have a surface protective layer, for example, to prevent adhesion of the image-forming layer. The details of the surface protective layer are described in, for example, JP-A-11-65021, paragraphs 0119 to 0120.

[0205] Gelatin is preferred for the binder in the surface protective layer of the thermally processed image recording material of the present invention, but polyvinyl alcohol (PVA) is also preferably used. Examples of PVA includes, for example, completely saponified PVA-105 [having a polyvinyl alcohol (PVA) content of at least 94.0% by weight, a degree of saponification of 98.5 ± 0.5 mole %, a sodium acetate content of 1.5% by weight or less, a volatile content of 5.0% by weight or less, a viscosity (4% by weight at 20°C) of 5.6 ± 0.4 mPa·s]; partially saponified PVA-205 [having a PVA content of 94.0% by weight, a degree of saponification of 88.0 ± 1.5 mole %, a sodium acetate content of 1.0% by weight, a volatile content of 5.0% by weight, a viscosity (4% by weight at 20°C) of 5.0 ± 0.4 mPa·s]; modified polyvinyl alcohols, MP-102, MP-202, MP-203, R-1130, R2105 (all from Kraray) and so forth. The polyvinyl alcohol content (per m² of the support) of one protective layer is preferably 0.3 to 4.0 g/m², more preferably 0.3 to 2.0 g/m².

[0206] The temperature at which the coating solution for the image-forming layer is prepared is preferably 30°C to 65°C, more preferably 35°C to 60°C but lower than 60°C, even more preferably 35°C to 55°C. The temperature of the coating solution is preferably kept at 30°C to 65°C immediately after the addition of polymer latex. A reducing agent and an organic silver salt are mixed preferably before the addition of polymer latex.

[0207] The organic silver salt-containing liquid or the coating solution for the thermographic image-forming layer is a preferably so-called thixotropic flow. Thixotropy indicates a property of a fluid that viscosity of the fluid lowers with the increase of shear rate. While any apparatus may be used for measuring the viscosity of fluids, RFS Fluid Spectrometer from Rheometrics Far East Co., Ltd. is preferably used and the measurement is performed at 25°C. The organic silver salt-containing liquid or the coating solution for the photothermographic image-forming layer preferably has a viscosity of 400 mPa·s to 100,000 mPa·s, more preferably 500 mPa·s to 20,000 mPa·s, at a shear rate of 0.1 sec^-1. The viscosity is preferably 1 mPa·s to 200 mPa·s, more preferably 5 mPa·s to 80 mPa·s, at a shear rate of 1000 sec^-1.

[0208] Various thixotropic fluid systems are known and, for example, described in "Lecture on Rheology", Kobunshi Kanko Kai; Muroi & Morino, "Polymer Latex", Kobunshi Knako Kai and so forth. Thixotropic fluids indispensably contain a large amount of fine solid microparticles. For enhancing thixotropic property, it is effective that the fluids shall contain a viscosity-increasing linear polymer, or the contained fine solid microparticles shall have anisotropic shapes and have an increased aspect ratio. Use of an alkaline viscosity-increasing agent or a surfactant is also effective for that purpose.

[0209] The photothermographic emulsion layer used in the present invention is formed as one or more layers on the support. When it consists of one layer, the layer must contain an organic silver salt, a silver halide, a developing agent and a binder, as well as optional additional materials such as color tone adjuster, coating aid and other auxiliary agents. When it consists of two layers, the first emulsion layer (in general, this is directly adjacent to the support) must contain an organic silver salt and a silver halide, and the second emulsion layer or the two layers must contain the other ingredients. Apart from these layer structures, also employable is another type of two-layer structure in which one layer is a single emulsion layer containing all the necessary ingredients and the other layer is a protective top coat layer. Multicolor photothermographic image recording material may contain these two layers for each color, or may contain all the necessary ingredients in a single layer as described in U.S. Patent No. 4,708,928. As for multicolor photothermographic image recording materials with multiple dyes, the individual emulsion layers are contained in the material in such a state that they are partitioned each other by using a functional or non-functional barrier layer between the adjacent photosensitive layers as described in U.S. Patent No. 4,460,681.

[0210] The photosensitive layer of the thermally processed image recording material of the present invention may contain various types of dyes and pigments for improving the color tone, for preventing interference fringes generated during laser exposure, and for preventing irradiation. The details of such dyes and pigments are described in International Patent Publication WO98/36322. Preferred dyes and pigments for the photosensitive layer are anthraquinone dyes, azomethine dyes, indoaniline dyes, azo dyes, indanthrone pigments of anthraquinone type (e.g., C.I. Pigment Blue 60 etc.), phthalocyanine pigments (e.g., copper phthalocyanines such as C.I. Pigment Blue 15; metal-free phthalocyanines such as C.I. Pigment Blue 16), triarylcarbonyl pigments of printing lake pigment type, indigo, inorganic pigments (e.g., ultramarine, cobalt blue etc.) and so forth. These dyes and pigments may be added to the layer in any desired manner. For example, they may be added as solutions, emulsions or dispersions of fine solid microparticles, or they may be added in such a state that they are mordanted on a polymer mordant. The amount of these compounds to be used may vary depending on the intended absorbance, but they are preferably used in an amount of 1 µg to 1 g per m² of the thermally processed image recording material, in general.

[0211] In the thermally processed image recording material of the invention, an antihalation layer may be provided at a position opposite to the light source with respect to the photosensitive layer. The details of the antihalation layer are described in JP-A-11-65021, paragraphs 0123 to 0124.

[0212] In the present invention, a decoloring dye and a base precursor are preferably added to a light insensitive layer of the thermally processed image recording material so that the light insensitive layer should function as a filter layer or an antihalation layer. Thermally processed image recording materials generally have light insensitive layers in addition to photosensitive layers. Depending on their positions, the light insensitive layers are classified into (1) a protective layer to be disposed on a photosensitive layer (remoter from the support than the photosensitive layer); (2) an intermediate layer to be disposed between photosensitive layers or between a photosensitive layer and a protective layer; (3) an undercoat layer to be disposed between a photosensitive layer and a support; (4) a backing layer to be disposed on a side opposite to that on which a photosensitive layer is disposed. The filter layer is provided in the photosensitive material as the layer (1) or (2). The antihalation layer is provided in the photosensitive material as the layer (3) or (4).

[0213] The decoloring dye and the base precursor are preferably added to the same light insensitive layer. However, they may be added separately to adjacent two light insensitive layers. If desired, a barrier layer may be disposed between the two light insensitive layers.

[0214] For adding a decoloring dye to a light insensitive layer, a solution, emulsion or solid microparticles dispersion of the dye can be added to a coating solution for the light insensitive layer. The dye may also be added to the light insensitive layer by using a polymer mordant. These addition methods are the same as those generally employed for adding dyes to ordinary thermally processed image recording materials. Polymer latex used for impregnated polymers are described in U.S. Patent No. 4,199,363, German Patent Laid-Open Nos. 25,141,274, 2,541,230, EP-A-029104, and JP-B-53-41091. A method for emulsification by adding a dye to a polymer solution is described in International Patent Publication WO88/00723.

[0215] The amount of the decoloring dye to be added is determined depending on the use of the dye. In general, the dye is used in such an amount that the dye added can ensure an optical density (absorbance), measured at an intended wavelength, of larger than 1.0. The optical density is preferably 0.2 to 2. The amount of the dye capable of ensuring the optical density within the range may be generally from 0.001 to 1 g/m² or so, preferably from 0.005 to 0.8 g/m² or so, particularly preferably from 0.01 to 0.2 g/m² or so.

[0216] Decoloring the dyes in that manner can lower the optical density of the material to 0.1 or less. Two or more different types of decoloring dyes may be used in the thermodecoloring type recording materials or thermally processed image recording materials. Similarly, two or more different types of base precursors may be used in combination.

[0217] The thermally processed image recording material of the present invention is preferably a so-called single-sided photosensitive material comprising at least one photosensitive layer containing a silver halide emulsion on one side of support, and a backing layer on the other side.

[0218] The thermally processed image recording material of the present invention preferably contains a matting agent for improving the transferability of the material. Matting agents are described in JP-A-11-65021, paragraphs 0126 to 0127. The matting agent is added in an amount of preferably 1 to 400 mg/m², more preferably 5 to 300 mg/m², in terms of the amount per 1 m² of the image recording material.

[0219] The matting degree of the surface of the emulsion layer is not particularly limited so long as the matted emulsion layer surface is free from stardust defects. However, Beck's smoothness of the matted surface is preferably 50 seconds to 10000 seconds, more preferably 80 seconds to 10000 seconds.

[0220] The matting degree of the backing layer in the present invention is preferably falls 10 seconds to 1200 seconds, more preferably 30 seconds to 700 seconds, even more preferably 50 seconds to 500 seconds, in terms of the Beck's smoothness.

[0221] The matting agent is preferably contained in the outermost surface layer, or in a layer functioning as an outermost surface layer, or in a layer near to the outer surface of the image recording material. It is also preferably contained in a layer functioning as a protective layer.

[0222] The details of a backing layer that can be used in the present invention are described in JP-A-11-65021, paragraphs 0128 to 0130.

[0223] A hardening agent may be added to the photosensitive layer, the protective layer, the backing layer and other layers in the thermally processed image recording material of the present invention. The details of the hardening agent are described in T.H. James, "THE THEORY OF THE PHOTOGRAPHIC PROCESS, FOURTH EDITION", Macmillan Publishing Co., Inc., 1977, pp. 77-87. For example, preferably used are polyvalent metal ions described on page 78 of the reference; polyisocyanates described in U.S. Patent No. 4,281,060 and JP-A-6-208193; epoxy compounds described in U.S. Patent No. 4,791,042; vinylsulfone compounds described in JP-A-62-89048 and so forth.

[0224] The hardening agent is added to coating solutions as a solution. Preferred addition time point for the solution into the coating solution for protective layer resides in a period of from 180 minutes before the coating to immediately before the coating, preferably 60 minutes to 10 seconds before the coating. The method and conditions for mixing are not particularly limited as far as the effect of the present invention can be attained satisfactorily. Specific examples of the mixing method include a method in which the mixing is performed in a tank designed so that a desired average residence time therein can be obtained, which residence time is calculated from addition flow rate and feeding amount to a coater, a method utilizing a static mixer described in N. Harnby, M.F. Edwards, A.W. Nienow, "Ekitai Kongo Gijutsu (Techniques for Mixing Liquids)", translated by Koji Takahashi, Chapter 8, Nikkan Kogyo Shinbunsha, 1989 and so forth.

[0225] Surfactants that can be used in the thermally processed image recording material of the invention are described in JP-A-11-65021, paragraph 0132; usable solvents are described in the same but in paragraph 0133; usable supports are described in the same but in paragraph 0134; usable antistatic and electroconductive layers are described in the same but in paragraph 0135; and usable methods for forming color images are described in the same but in paragraph 0136.

[0226] Transparent supports for the thermally processed image recording material of the present invention may be colored with blue dyes (e.g., with Dye-1 described in Examples of JP-A-8-240877), or may be colorless. Techniques for undercoating the supports are described in JP-A-11-84574, JP-A-10-186565 and so forth.

[0227] The thermally processed image recording material of the invention is preferably of a monosheet type. The monosheet type does not use any additional sheets such as image receiving materials, but can form images directly on the material itself.

[0228] The thermally processed image recording material of the present invention may further contain an antioxidant, a stabilizer, a plasticizer, a UV absorber or a coating aid. Such additives may be added to any of photosensitive layers or light insensitive layers. For these additives, International Patent Publication WO98/36322, EP803764A1, JP-A-10-186567, JP-A-10-18568 and so forth may be referred to.

[0229] The thermally processed image recording material of the present invention can be produced by using any coating method. Specific examples thereof include various types of coating techniques, for example, extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating, extrusion coating utilizing a hopper of the type described in U.S. Patent No. 2,681,294 and so forth. Preferably used are extrusion coating and slide coating described in Stephen F. Kistler, Petert M. Schweizer, "LIQUID FILM COATING", published by CHAPMAN & HALL Co., Ltd., 1997, pp.399-536, and particularly preferably used is the slide coating. An example of the shape of a slide coater used for the slide coating is shown in Figure 11b, 1, on page 427 of the aforementioned reference. If desired, two or more layers may be formed at the same time, for example, according to the methods described from page 399 to page 536 of the aforementioned reference, or the methods described in U.S. Patent No. 2,761,791 and British Patent No. 837,095.

[0230] As a method for preventing uneven processing caused by dimensional change of the thermally processed image recording material of the present invention during the aforementioned heat development, effectively used is a method comprising heating the material for 5 seconds or more at a temperature of from 80°C to a temperature lower than 115°C (preferably 113°C or lower) so as not to produce images and then performing heat development at a temperature of 110°C or higher (preferably 130°C or higher) to form images (so-called multi-step heating method).

[0231] Other techniques that can be used for the thermally processed image recording material of the present invention are also in EP803764A1, EP883022A1, International Patent Publication WO98/36322, JP-A-9-281637, JP-A-9-297367, JP-A-9-304869, JP-A-9-311405, JP-A-9-329865, JP-A-10-10669, JP-A-10-62899, JP-A-10-69023, JP-A-10-186568, JP-A-10-90823, JP-A-10-171063, JP-A-10-186565, JP-A-10-186567, JP-A-10-186569, JP-A-10-186570, JP-A-10-186571, JP-A-10-186572, JP-A-10-197974, JP-A-10-197982, JP-A-10-197983, JP-A-10-197985, JP-A-10-197986, JP-A-10-197987, JP-A-10-207001, JP-A-10-207004, JP-A-10-221807, JP-A-10-282601, JP-A-10-288823, JP-A-10-288824, JP-A-10-307365, JP-A-10-312038, JP-A-10-339934, JP-A-11-7100, JP-A-11-15105, JP-A-11-24200, JP-A-11-24201, JP-A-11-30832, JP-A-11-84574 and JP-A-11-65021.

[0232] An example of the structure of a heat-developing apparatus used for the heat development of the thermally processed image recording material of the present invention is shown in Fig. 1. Fig. 1 depicts a side view of a heat-developing apparatus. The apparatus shown in Fig. 1 comprises carrying-in roller pairs 11 (lower rollers are heating rollers), which carry a thermally processed image recording material 10 into the heating section while making the material in a flat shape and preheating it, and carrying-out roller pairs 12, which carry out the thermally processed image recording material 10 after heat development from the heating section while maintaining the material to be in a flat shape. The thermally processed image recording material 10 is heat-developed while it is conveyed by the carrying-in roller pairs 11 and then by the carrying-out roller pairs 12. A conveying means for carrying the thermally processed image recording material 10 under the heat development is provided with multiple rollers 13 so that they should be contacted with the side of the image-forming layer, and a flat surface 14 consisting of non-woven fabric (composed of aromatic polyamide, Teflon etc.) or the like is provided on the opposite side so that it should be contacted with the back surface. The thermally processed image recording material 10 is conveyed by driving of the multiple rollers 13 contacted with the image-forming layer side, while the back surface slides on the flat surface 14. As a heating means, heaters 15 are provided over the rollers 13 and under the flat surface 14 so that the thermally processed image recording material 10 should be heated from the both sides. Examples of the heating means include panel heaters and so forth. While clearance between the rollers 13 and the flat surface 14 may vary depending on the member of the flat surface, it is suitably adjusted to a clearance that allows the conveyance of the thermally processed image recording material 10. The clearance is preferably 0-1 mm.

[0233] The material of the surface of the rollers 13 and the member of the flat surface 14 may be composed of any materials so long as they have heat resistance and they should not cause any troubles in the conveyance of the thermally processed image recording material 10. However, the material of the roller surface is preferably composed of silicone rubber, and the member of the flat surface is preferably composed of non-woven fabric made of aromatic polyamide or Teflon (polytetrafluoroethylene). The heating means preferably comprises multiple heaters so that temperature of each heater can be adjusted freely.

[0234] The heating section is constituted by a preheating section A comprising the carrying-in roller pairs 11 and a heat development section B comprising the heaters 15. The temperature of the preheating section A located upstream from the heat development section B is preferably selected to be lower than the heat development temperature (for example, by about 10-30°C), and the temperature and heat development time are preferably adjusted so that they are sufficient for evaporating moisture contained in the thermally processed image recording material 10. The temperature of the heat development section B is also preferably selected to be higher than the glass transition temperature (Tg) of the support of the thermally processed image recording material 10 so that uneven development should be prevented.

[0235] Moreover, guide panels 16 are provided downstream from the heat development section B, and they constitute a gradual cooling section C together with the carrying-out roller pairs 12. The guide panels 16 are preferably composed of a material of low heat conductivity, and it is preferred that the cooling is performed gradually.

[0236] The heat-development apparatus is explained with reference to an example shown in the drawing. However, the apparatus is not limited to the example. For example, the heat-development apparatus used for the present invention may have a variety of structures such as disclosed in JP-A-7-13294. For the multi-stage heating method, which is preferably used in the present invention, the thermally processed image recording material may be successively heated at different temperatures in such an apparatus as mentioned above, which is provided with two or more heat sources at different temperatures.

[0237] The thermally processed image recording material of the invention may be developed in any manner. Usually, an imagewise exposed thermally processed image recording material is developed by heating. The temperature for the development is preferably 80°C to 250°C, more preferably 100°C to 140°C. The development time is preferably 1 to 180 seconds, more preferably 10 to 90 seconds, even more preferably 10 to 40 seconds.

[0238] For thermal development for the material, preferred is a plate heater system. For heat development by the plate heater system, the methods described in Japanese Patent Application Nos. 9-229684 and JP-A-11-133572 are preferred. The plate heater system described in these references is a heat development apparatus wherein a thermally processed image recording material on which a latent image is formed is brought into contact with a heating means in a heat development section to obtain a visible image. In this apparatus, the heating means comprises a plate heater, and a plurality of presser rollers are disposed facing to one surface of the plate heater. Heat development of the thermally processed image recording material is attained by passing the material between the presser rollers and the plate heater. The plate heater is preferably sectioned into 2 to 6 stages, and the temperature of the top stage is preferably kept lower by 1 to 10°C or so than that of the others. Such a method is also described in JP-A-54-30032. Such a plate heater system can remove moisture and organic solvent contained in the thermally processed image recording material out of the material, and prevent deformation of the support of the thermally processed image recording material by rapidly heating the material.

[0239] The thermally processed image recording material of the present invention can be exposed in any manner. As light source of exposure, laser rays are preferred. As the laser used in the present invention, gas lasers (Ar⁺, He-Ne), YAG lasers, dye lasers, semiconductor lasers and so forth are preferred. A combination of semiconductor laser and second harmonic generating device may also be used. Preferred are gas or semiconductor lasers for red to infrared emission.

[0240] Single mode lasers can be used for the laser rays, and the technique disclosed in JP-A-11-65021, paragraph 0140 can be used.

[0241] The laser output is preferably at least 1 mW, more preferably at least 10 mW. Even more preferred is high output of at least 40 mW. If desired, a plurality of lasers may be combined. The diameter of one laser ray may be on the level of 1/e² spot size of a Gaussian beam, falling between 30 and 200 µm or so.

[0242] The thermally processed image recording material of the invention forms a monochromatic image based on silver image, and is preferably used as photothermographic photosensitive materials for use in medical diagnosis, industrial photography, printing and COM. Needless to say, in such applications, the monochromatic images formed can be duplicated on duplicating films, MI-Dup, from Fuji Photo Film for medical diagnosis; and for printing, the images can be used as the mask for forming reverse images on printing films such as DO-175 and PDO-100 from Fuji Photo Film, or on offset printing plates.

EXAMPLES

[0243] The present invention will be more specifically explained with reference to the following examples. However, the scope of the present invention is not limited by the following examples.

[0244] Synthesis examples of the compounds of the formula (1) will be mentioned below.

〈Synthesis Example 1: Synthesis of Exemplary Compound (P-5)〉

[0245] 

(1) Synthesis of Intermediate Compound (B)

[0246] The readily available Compound (A) (93 g), sodium hydroxide (43 g), sodium chloroacetate (123 g) and potassium iodide (10 g) were dissolved in water (300 ml), and stirred at 80°C for 2 hours. After the internal temperature was lowered to 30°C, the solution was added with concentrated hydrochloric acid (50 ml). After the reaction mixture was stirred for a while, crystals were deposited. The crystals were taken by suction filtration and dried. As a result, 80 g of Intermediate Compound (B) was obtained as white crystals.

(2) Synthesis of Intermediate Compound (C)

[0247] To a solution of NaOH (57 g) in water (500 ml), bromine (33 ml) was added dropwise at room temperature, and then an aqueous solution of Intermediate Compound (B) (24 g) and NaOH (8 g) in water (100 ml) was added dropwise at room temperature. The deposited crystals were taken by filtration, and the obtained crystals were added to diluted hydrochloric acid, stirred and corrected by filtration. The crystals were fully washed with water and dried. As a result, 30 g of Intermediate Compound (C) was obtained as white crystals.

(3) Synthesis of Intermediate Compound (D)

[0248] The Intermediate Compound (C) (30 g) and DMF (1 ml) were dissolved in thionyl chloride (100 ml) and stirred at 70°C for 30 minutes. Then, excessive thionyl chloride was evaporated under reduced pressure. As a result, 31 g of Intermediate (D) was obtained as white crystals.

(4) Synthesis of Exemplary Compound (P-3)

[0249] A solution of octylamine (8.0 g) in methanol (50 ml) was cooled on ice, and added with Intermediate Compound (D) (4.0 g). After the mixture was stirred for 10 minutes at room temperature, 50 ml of diluted hydrochloric acid was added to the mixture. As a result, white crystals were deposited. The crystals were taken by filtration to obtain 3.0 g of Exemplary Compound (P-3) as white crystals (yield: 62%).

〈Synthesis Example 2: Synthesis of Exemplary Compound (P-1)〉

[0250] 3.5 g of Exemplary Compound (P-1) was obtained as white crystals (yield: 81%) in the same manner as that of Synthesis Example 1 except that the octylamine was replaced with an equimolar amount of n-butylamine.

〈Synthesis Example 3: Synthesis of Exemplary Compound (P-7)〉

[0251] 3.7 g of Exemplary Compound (P-7) was obtained as white crystals (yield: 84%) in the same manner as that of Synthesis Example 1 except that the octylamine was replaced with an equimolar amount of n-pentylamine.

〈Synthesis Example 4: Synthesis of Exemplary Compound (P'-12)〉

[0252] 3.1 g of Exemplary Compound (P'-12) was obtained as white crystals in the same manner as that of Synthesis Example 1 except that the octylamine was replaced with an equimolar amount of 2,2,2-trifluoroethylamine.

〈Synthesis Example 5: Synthesis of Exemplary Compound (P'-4)〉

[0253] 2.9 g of Exemplary Compound (P'-4) was obtained as white crystals in the same manner as that of Synthesis Example 1 except that the octylamine was replaced with an equimolar amount of isopentylamine.

[0254] Preparation and evaluation of thermally processed image recording materials of the present invention utilizing the compounds of the formula (1) will be mentioned in the following Examples 1 and 2.

[0255] Structures of the comparative compounds used in the examples are shown below. Comparative Compounds 1-4 shown below correspond to Comparative Compounds 1-4 mentioned in Tables 1 and 3 mentioned later in the present specification, and Comparative Compounds (1)-(5) shown below correspond to Comparative Compounds (1)-(5) mentioned in Tables 2 and 4 mentioned later in the present specification.

〈Example 1〉

[0256] The structures of the compounds used in Example 1 are shown below.

1. Preparation of PET support

[0257] Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity IV of 0.66 (measured in phenol/tetrachloroethane = 6/4 (weight ratio) at 25°C) was obtained in a conventional manner. The PET was pelletized, and the pellets were dried at 130°C for 4 hours, melted at 300°C, extruded from a T-die, and quenched to prepare an unstretched film having such a thickness that the film thickness after thermal fixation should become 175 µm.

[0258] The film was stretched along the longitudinal direction by 3.3 times using rollers having different peripheral speeds and then stretched along the transverse direction by 4.5 times using a tenter. In this case, the temperatures were 110°C and 130°C, respectively. Thereafter, the film was subjected to thermal fixation at 240°C for 20 seconds and relaxed by 4% along the transverse direction at the same temperature. Then, after chucks of the tenter were released, the both edges of the film were knurled, and the film was rolled up at 4 kg/cm² to provide a roll of the film having a thickness of 175 µm.

2. Surface corona discharging treatment

[0259] Using a solid state corona discharging treatment machine Model 6KVA manufactured by Piller Inc., both surfaces of the support were treated at room temperature at 20 m/minute. In this case, from the read out values of the electric current and the voltage, it was seen that the treatment of 0.375 kV·A·minute/m² was applied to the support. The treated frequency in this case was 9.6 kHz and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

3. Preparation of undercoated support

(1) Preparation of coating solution for undercoat layer

[0260] Coating solutions of the following formulations (1) to (3) were prepared.

Formulation (1) (for undercoat layer on photosensitive layer side)

[0261] 

Pesresin A-515GB made by Takamatsu Yushi K.K. (30 % by weight solution)	234 g
Polyethylene glycol monononylphenyl ether (mean ethylene oxide number = 8.5, 10 % by weight solution)	21.5 g
MP-1000 made by Soken Kagaku K.K. (polymer microparticles, mean particle size: 0.4 µm)	0.91 g
Distilled water	744 ml

Formulation (2) (for 1st layer on back surface)

[0262] 

Butadiene-styrene copolymer latex (solid content: 40 % by weight, weight ratio of butadiene/styrene = 32/68)	158 g
2,4-Dichloro-6-hydroxy-S-triazine sodium salt (8 % by weight aqueous solution)	20 g
1 % by weight Aqueous solution of sodium laurylbenzenesulfonate	10 ml
Distilled water	854 ml

Formulation (3) (for 2nd layer on back surface side)

[0263] 

SnO2/SbO (weight ratio: 9/1, mean particle size: 0.038 µm, 17 % by weight dispersion)	84 g
Gelatin (10% aqueous solution)	89.2 g
Metorose TC-5 made by Shin-Etsu Chemical Co., Ltd. (2% aqueous solution)	8.6 g
MP-1000 (polymer microparticles) made by Soken Kagaku K.K.	0.01 g
1 % by weight Aqueous solution of sodium dodecylbenzenesulfonate	10 ml
NaOH (1%)	6 ml
Proxel (made by ICI Co.)	1 ml
Distilled water	805 ml

(2) Preparation of undercoated support

[0264] After applying the aforementioned corona discharging treatment to both surfaces of the aforementioned biaxially stretched polyethylene terephthalate support having a thickness of 175 µm, one surface (photosensitive layer coating surface side) thereof was coated with the undercoating solution of Formulation (1) by a wire bar in a wet coating amount of 6.6 ml/m² (per one surface) and dried at 180°C for 5 minutes. Then, the back surface thereof was coated with the undercoating solution of Formulation (2) by a wire bar in a wet coating amount of 5.7 ml/m² and dried at 180°C for 5 minutes. Further, the back surface thus coated was coated with the undercoating solution of Formulation (3) by a wire bar in a wet coating amount of 7.7 ml/m² and dried at 180°C for 6 minutes to prepare an undercoated support.

4. Preparation of coating solution for back surface

(1) Preparation of Solid microparticie dispersion (a) of base precursor

[0265] 64 g of Base precursor compound 11, 28 g of diphenylsulfone and 10 g of a surface active agent, Demor N (manufactured by Kao Corporation), were mixed with 220 ml of distilled water, and the mixture was beads-dispersed using a sand mill (1/4 Gallon Sand Grinder Mill, manufactured by Imex Co.) to obtain Solid microparticle dispersion (a) of the base precursor compound having a mean particle size of 0.2 µm.

(2) Preparation of dye solid microparticle dispersion

[0266] 9.6 g of Cyanine dye compound 13 and 5.8 g of sodium p-dodecylbenzenesulfonate were mixed with 305 ml of distilled water and the mixture was beads-dispersed using a sand mill (1/4 Gallon Sand Grinder Mill, manufactured by Imex Co.) to obtain a dye solid microparticle dispersion having a mean particle size of 0.2 µm.

(3) Preparation of coating solution for antihalation layer

[0267] 17 g of gelatin, 9.6 g of polyacrylamide, 70 g of the aforementioned Solid microparticle dispersion (a) of the base precursor, 56 g of the aforementioned dye solid microparticle dispersion, 1.5 g of polymethyl methacrylate microparticles (mean particle size 6.5 µm), 0.03 g of benzoisothiazolinone, 2.2 g of sodium polyethylenesulfonate, 0.2 g of Blue dye compound 14 and 844 ml of water were mixed to prepare a coating solution for antihalation layer.

5. Preparation of coating solution for back surface protective layer

[0268] In a container kept at 40°C, 50 g of gelatin, 0.2 g of sodium polystyrenesulfonate, 2.4 g of N,N-ethylenebis(vinylsulfonacetamide), 1 g of sodium t-octylphenoxyethoxyethanesulfonate, 30 mg of benzoisothiazolinone, 37 mg of N-perfluorooctylsulfonyl-N-propylalanine potassium salt, 0.15 g of polyethyleneglycol mono(N-perfluorooctylsulfonyl-N-propyl-2-aminoethyl) ether [average polymerization degree of ethylene oxide: 15], 32 mg of C₈F₁₇SO₃K, 64 mg of C₈F₁₇SO₂N(C₃H₇)(CH₂CH₂O)₄(CH₂)₄-SO₃Na, 8.8 g of an acrylic acid/ethyl acrylate copolymer (copolymerization ratio (by weight): 5/95), 0.6 g of Aerosol OT (manufactured by American Cyanamid Company), 1.8 g (as liquid paraffin) of a liquid paraffin emulsion and 950 ml of water were mixed to form a coating solution for a back surface protective layer.

6. Preparation of Silver halide emulsion 1

[0269] 1421 ml of distilled water was added with 8.0 ml of a 1 % by weight potassium bromide solution, and further added with 8.2 ml of 1 mol/L nitric acid and 20 g of phthalized gelatin. Separately, Solution A was prepared by adding distilled water to 37.04 g of silver nitrate to dilute it to 159 ml, and Solution B was prepared by diluting 32.6 g of potassium bromide with distilled water to a volume of 200 ml. To the aforementioned mixture maintained at 37°C and stirred in a titanium-coated stainless steel reaction vessel, the whole volume of Solution A was added by the control double jet method over 1 minute at a constant flow rate while pAg was maintained at 8.1. Solution B was also added by the control double jet method. Then, the mixture was added with 30 ml of 3.5 % by weight aqueous hydrogen peroxide solution, and further added with 36 ml of a 3 % by weight aqueous solution of benzimidazole. Separately, Solution A2 was prepared by diluting Solution A with distilled water to a volume of 317.5 ml, and Solution B2 was prepared by dissolving tripotassium hexachloroiridate in Solution B in such an amount that its final concentration should become 1 × 10^-4 mole per mole of silver, and diluting the obtained solution with distilled water to a volume twice as much as the volume of Solution B, 400 ml. The whole volume of Solution A2 was added to the mixture again by the control double jet method over 10 minutes at a constant flow rate while pAg was maintained at 8.1. Solution B2 was also added by the control double jet method. Then, the mixture was added with 50 ml of a 0.5 % by weight solution of 2-mercapto-5-methylbenzimidazole in methanol. After pAg was raised to 7.5 with silver nitrate, the mixture was adjusted to pH 3.8 using 0.5mol/L sulfuric acid, and the stirring was stopped. Then, the mixture was subjected to precipitation, desalting and washing with water, added with 3.5 g of deionized gelatin and 1 mol/L sodium hydroxide to be adjusted to pH 6.0 and pAg of 8.2 to form a silver halide dispersion.

[0270] The grains in the completed silver halide emulsion were pure silver bromide grains having a mean spherical diameter of 0.053 µm and a variation coefficient of 18% in terms of spherical diameter. The grain size and others were obtained from averages for 1000 grains by using an electron microscope. The [100] face ratio of these grains were determined to be 85% by the Kubelka-Munk method.

[0271] The aforementioned dispersion was added with 0.035 g of benzoisothiazolinone (added as a 3.5 % by weight methanol solution of the compound) with stirring at 38°C, after 40 minutes since then, added with the solid dispersion (an aqueous gelatin solution) of Spectral sensitizing dye A described above in an amount of 5 × 10^-3 mole per mole of silver. After 1 minutes, the mixture was warmed to 47°C, and after 20 minutes, added with 3 × 10^-5 mole of sodium benzenethiosulfonate per mole of silver. Further after 2 minutes, the mixture was added with Tellurium sensitizer B in an amount of 5 × 10^-5 mole per mole of silver followed by ripening for 90 minutes. Immediately before finishing the ripening, the mixture was added with 5 ml of a 3.5 % by weight methanol solution of N,N'-dihydroxy-N''-diethylmelamine, and after lowering the temperature to 31°C, added with 5 ml of a 3.5 % by weight methanol solution of phenoxyethanol, 7 × 10^-3 mole of 5-methyl-2-mercaptobenzimidazole per mole of silver, and 6.4 × 10^-3 mole of 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole per mole of silver to prepare Silver halide emulsion 1.

7. Preparation of Silver halide emulsion 2

[0272] In the same manner as the preparation of Silver halide emulsion 1 except that the liquid temperature upon forming the grains was changed from 37°C to 50°C, a pure silver bromide cubic grain dispersion having a mean grain size of 0.08 µm as spheres and a variation coefficient of 15% for size as spheres was prepared. Further, as in the case of Silver halide emulsion 1, the steps of precipitation, desalting, washing with water and dispersion were performed. Furthermore, in the same manner as in the case of Silver halide emulsion 1 except that the addition amount of Spectral sensitizing dye A was changed to 4.5 × 10^-3 mole per mole of silver, the spectral sensitizer, the chemical sensitizer, 5-methyl-2-mercaptobenzimidazole and 1-phenyl-2-heptyl-5-mercapto-1,3,4-traizole were added to the dispersion to obtain Silver halide emulsion 2.

8. Preparation of Silver halide emulsion 3

[0273] In the same manner as the preparation of Silver halide emulsion 1 except that the liquid temperature upon forming the grains was changed from 37°C to 27°C, a pure silver bromide cubic grain dispersion having a mean grain size of 0.038 µm as spheres and a variation coefficient of 20% for size as spheres was prepared. Further, as in the case of Silver halide emulsion 1, the steps of precipitation, desalting, washing with water and dispersion were performed. Furthermore, in the same manner as in the case of Silver halide emulsion 1 except that the addition amount of Spectral sensitizing dye A was changed to 6 × 10^-3 mole per mole of silver, the spectral sensitizer, the chemical sensitizer, 5-methyl-2-mercaptobenzimidazole and 1-phenyl-2-heptyl-5-mercapto-1,3,4-traizole were added to the dispersion to obtain Silver halide emulsion 2.

9. Preparation of Mixed emulsion A for coating solution

[0274] 70% by weight Silver halide emulsion 1, 15% by weight Silver halide emulsion 2 and 15% by weight Silver halide emulsion 3 were mixed, and added with benzothiazolium iodide in an amount of 7 × 10^-3 mole per mole of silver as a 1 % by weight aqueous solution.

10. Preparation of scaly fatty acid silver salt

[0275] 87.6 kg of behenic acid (Edenor C22-85R, trade name, manufactured by Henkel Co.), 423 L of distilled water, 49.2 L of a 5 mol/L aqueous solution of NaOH, and 120 L of tert-butanol were mixed and allowed to react with stirring at 75°C for one hour to obtain a solution of sodium behenate. Separately, 206.2 L of an aqueous solution containing 40.4 kg of silver nitrate (pH 4.0) was prepared and kept at 10°C. A mixture of 635 L of distilled water and 30 L of tert-butanol contained in a reaction vessel kept at 30°C was added with the whole amount of the aforementioned sodium behenate solution and the whole amount of the aqueous silver nitrate solution at constant flow rates over the periods of 62 minutes and 10 seconds, and 60 minutes, respectively. In this case, they were added in such a manner that only the aqueous silver nitrate solution was added for 7 minutes and 20 seconds after starting the addition of the aqueous silver nitrate solution, and for 9 minutes and 30 seconds after finishing the addition of the aqueous silver nitrate solution, only the sodium behenate solution was added. In this operation, the outside temperature was controlled so that the temperature in the reaction vessel should be 30°C and the liquid temperature should be constant. The piping of the addition system for the sodium behenate solution was warmed by steam trace and the steam opening was controlled such that the liquid temperature at the outlet orifice of the addition nozzle should be 75°C. The piping of the addition system for the aqueous silver nitrate solution was maintained by circulating cold water outside a double pipe. The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically with respect to the stirring axis as the center, and the positions are controlled at heights for not contacting with the reaction mixture.

[0276] After finishing the addition of the sodium behenate solution, the mixture was left with stirring for 20 minutes at the same temperature and then the temperature was decreased to 25°C. Thereafter, the solid content was recovered by a suction filtration and the solid content was washed with water until electric conductivity of the filtrate became 30 µS/cm. Thus, a fatty acid silver salt was obtained. The solid content was stored as a wet cake without being dried.

[0277] When the shape of the obtained silver behenate grains was evaluated by an electron microscopic photography, the grains were scaly crystals having a = 0.14 µm, b = 0.4 µm, and c = 0.6 µm in mean values, a mean aspect ratio of 5.2, a mean diameter as spheres of 0.52 µm, and a variation coefficient of 15% for mean diameter as spheres (the shape of the silver behenate grains was approximated to be a rectangular parallelepiped, and the sides of the rectangular parallelepiped were defined to be a, b and c from the shortest side.).

[0278] To the wet cake corresponding to 100 g of the dry solid content was added with 7.4 g of polyvinyl alcohol (PVA-217, trade name) and water to make the total amount 385 g, and the mixture was pre-dispersed by a homomixer.

[0279] Then, the pre-dispersed stock dispersion was treated three times by using a dispersing machine (Microfluidizer-M-110S-EH; trade name, manufactured by Microfluidex International Corporation, using G10Z interaction chamber) with a pressure controlled to be 1750 kg/cm² to obtain a silver behenate dispersion. During the cooling operation, a dispersion temperature of 18°C was achieved by providing coiled heat exchangers fixed before and after the interaction chamber and controlling the temperature of the refrigerant.

11. Preparation of 25 % by weight dispersion of reducing agent

[0280] 10 kg of 1,1-bis(2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane and 10 kg of a 20 % by weight aqueous solution of denatured polyvinyl alcohol (Poval MP203, manufactured by KURARAY CO., LTD.) were added with 16 kg of water, and mixed sufficiently to form a slurry. The slurry was fed by a diaphragm pump to a sand mill of horizontal type (UVM-2, manufactured by Imex Co.) containing zirconia beads having a mean diameter of 0.5 mm, and dispersed for 3 hours and 30 minutes. Then, the slurry was added with 0.2 g of benzothiazolinone sodium salt and water so that the concentration of the reducing agent should become 25 % by weight to obtain a reducing agent dispersion. The reducing agent particles contained in the reducing agent dispersion obtained as described above had a median diameter of 0.42 µm and the maximum particle size of 2.0 µm or shorter. The reducing agent dispersion was filtered through a polypropylene filter having a pore size of 10.0 µm to remove dusts and so forth, and stored.

12. Preparation of 10 % by weight dispersion of mercapto compound

[0281] 5 kg of 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole and 5 kg of a 20 % by weight aqueous solution of denatured polyvinyl alcohol (Poval MP203, manufactured by KURARAY CO., LTD.) were added with 8.3 kg of water and mixed sufficiently to form a slurry. The slurry was fed by a diaphragm pump to a sand mill of horizontal type (UVM-2, manufactured by Imex Co.) containing zirconia beads having a mean diameter of 0.5 mm, and dispersed for 6 hours. Then, the slurry was added with water so that the concentration of the mercapto compound should become 10 % by weight to obtain a mercapto compound dispersion. The mercapto compound particles contained in the mercapto compound dispersion obtained as described above had a median diameter of 0.40 µm and the maximum particle size of 2.0 µm or shorter. The mercapto compound dispersion was filtered through a polypropylene filter having a pore size of 10.0 µm to remove dusts and so forth, and stored. The dispersion was filtered through a polypropylene filter having a pore size of 10 µm immediately before use.

13. Preparation of solid microparticle dispersion of compound of formula (1)

[0282] 30 g of each of the compounds of the formula (1) shown in Tables 1 and 2 was added with 4 g of MP polymer (MP-203 manufactured by KURARAY CO., LTD.), 0.25 g of Compound C and 66 g of water and the mixture was stirred sufficiently to form a slurry. Thereafter, 200 g of zirconia silicate beads having a diameter of 0.5 mm were placed in a vessel together with the slurry and the slurry was dispersed by a dispersing machine (1/16 G Sand Grinder Mill; manufactured by Imex Co.) for 5 hours to prepare a solid microparticle dispersion. In the particles, 80 % by weight of the particles had a diameter of 0.3 µm to 1.0 µm. Each of Comparative Compounds was also dispersed in the same manner as above.

14. Preparation of 10 % by weight dispersion of phthalazine compound

[0283] A solution of 10 g of 6-isopropylphthalazine dissolved in 90 g of methanol was used.

15. Preparation of 20 % by weight dispersion of pigment

[0284] 64 g of C.I. Pigment Blue 60 and 6.4 g of Demor N manufactured by Kao Corporation were added with 250 g of water and mixed sufficiently to provide a slurry. Then, 800 g of zirconia beads having a mean diameter of 0.5 mm were placed in a vessel together with the slurry and the slurry was dispersed by a dispersing machine (1/4G Sand Grinder Mill; manufactured by Imex Co.) for 25 hours to obtain a pigment dispersion. The pigment particles contained in the pigment dispersion obtained as described above had a mean particle size of 0.21 µm.

16. Preparation of 40 % by weight SBR latex

[0285] An SBR latex purified by ultrafiltration (UF) was obtained as follows.

[0286] The SBR latex mentioned below diluted by 10 times with distilled water was diluted and purified by using an UF-purification module FS03-FC-FUYO3A1 (manufactured by Daisen Membrane System K.K.) until the ion conductivity became 1.5 mS/cm, and added with Sandet-BL (manufactured by SANYO CHEMICAL INDUSTRIES, LTD.) to a concentration of 0.22 % by weight. Further, the latex was added with NaOH and NH₄OH so that the ratio Na⁺ ion:NH₄⁺ ion should become 1:2.3 (molar ratio) to adjust pH to 8.4. At this point, the concentration of the latex was 40 % by weight.

[SBR latex: a latex of -St(68)-Bu(29)-AA(3), wherein the numerals in the parentheses indicate the contents in terms of % by weight, St represents styrene, Bu represents butadiene and AA represents acrylic acid]

[0287] The latex had the following characteristics: mean particle size of 0.1 µm, concentration of 45%, equilibrated moisture content at 25°C, relative humidity 60% of 0.6 % by weight, ion conductivity of 4.2 mS/cm (measured for the latex stock solution (40%) by using a conductometer, CM-30S, manufactured by Toa Electronics, Ltd., at 25°C), and pH of 8.2.

17. Preparation of coating solution for emulsion layer (photosensitive layer)

[0288] 1.1 g of the 20 % by weight aqueous dispersion of the pigment obtained above, 103 g of the organic acid silver salt dispersion, 2 g of the 20 % by weight aqueous solution of polyvinyl alcohol, PVA-205 (manufactured by KURARAY CO. LTD.), 25 g of the 25 % by weight dispersion of the reducing agent, a compound of the formula (1) (type and amount thereof are shown in Table 1), 6.2 g of the 10% dispersion of the mercapto compound, 130 g of the 40 % by weight SBR latex purified by ultrafiltration (UF) and undergone pH adjustment, and 16 ml of the 10 % by weight methanol solution of the phthalzine compound were mixed and added to 10 g of the aforementioned Silver halide emulsion A, and mixed sufficiently to prepare a coating solution for an emulsion layer. The coating solution was fed to a coating die in such a feeding amount giving a coating amount of 70 ml/m² and coated.

[0289] The viscosity of the coating solution for emulsion layer described above was measured by a B-type viscometer manufactured by Tokyo Keiki K.K. and found to be 85 [mPa·s] at 40°C (Rotor No. 1, 60 rpm).

[0290] The viscosity of the coating solution was measured at 25°C by an RFS fluid spectrometer produced by Rheometric Far East Co., Ltd., and found to be 1500, 220, 70, 40 and 20 [mPa·s] at shear rates of 0.1, 1, 10, 100 and 1000 [1/second], respectively.

18. Preparation of coating solution for intermediate layer on the emulsion layer surface

[0291] 772 g of an aqueous solution of 10 % by weight polyvinyl alcohol, PVA-205 (manufactured by KURARAY CO., LTD.), 5.3 g of the 20 % by weight dispersion of the pigment, and 226 g of a 27.5 % by weight latex of methyl methacrylate/styrene/butyl acrylate/hydroxyethyl methacrylate/acrylic acid copolymer (copolymerization ratio (by weight): 64/9/20/5/2) were added with 2 ml of a 5 % by weight aqueous solution of Aerosol OT (manufactured by American Cyanamid Company), 10.5 ml of a 20 % by weight aqueous solution of phthalic acid diammonium salt and water in such an amount giving a total amount of 880 g to form a coating solution for intermediate layer. This coating solution was fed to a coating die in such an amount that gave a coating amount of 10 ml/m².

[0292] The viscosity of the coating solution measured by a B-type viscometer at 40°C (Rotor No. 1, 60 rpm) was 21 [mPa·s].

19. Preparation of coating solution for 1st protective layer on emulsion layer surface

[0293] 64 g of inert gelatin was dissolved in water, added with 80 g of a 27.5 % by weight latex solution of methyl methacrylate/styrene/butyl acrylate/hydroxyethyl methacrylate/acrylic acid copolymer (copolymerization ratio (by weight): 64/9/20/5/2), 64 ml of a 10 % by weight methanol solution of phthalic acid, 74 ml of a 10 % by weight aqueous solution of 4-methylphthalic acid, 28 ml of 0.5 mol/L sulfuric acid, 5 ml of a 5 % by weight aqueous solution of Aerosol OT (manufactured by American Cyanamid Company), 0.5 g of phenoxyethanol, 0.1 g of benzoisothiazolinone, and water in such an amount that gave a total amount of 750 g to form a coating solution. The coating solution was mixed with 26 ml of 4 % by weight chromium alum by a static mixer immediately before coating, and fed to a coating die in such an amount that gave a coating amount of 18.6 ml/m².

[0294] The viscosity of the coating solution measured by a B-type viscometer (Rotor No. 1, 60 rpm) at 40°C was 17 [mPa·s].

20. Preparation of coating solution for 2nd protective layer on emulsion layer surface

[0295] 80 g of inert gelatin was dissolved in water, added with 102 g of a 27.5 % by weight latex solution of methyl methacrylate/styrene/butyl acrylate/hydroxyethyl methacrylate/acrylic acid copolymer (copolymerization ratio (by weight): 64/9/20/5/2), 3.2 ml of a 5 % by weight solution of N-perfluorooctylsulfonyl-N-propylalanine potassium salt, 32 ml of a 2 % by weight aqueous solution of polyethylene glycol mono(N-perfluorooctylsulfonyl-N-propyl-2-aminoethyl) ether [average polymerization degree of ethylene oxide = 15], 23 ml of a 5 % by weight aqueous solution of Aerosol OT (manufactured by American Cyanamid Company), 4 g of polymethyl methacrylate microparticles (mean particle size: 0.7 µm), 21 g of polymethyl methacrylate microparticles (mean particle size: 6.4 µm), 1.6 g of 4-methylphthalic acid, 8.1 g of phthalic acid, 44 ml of 0.5 mol/L sulfuric acid, 10 mg of benzoisothiazolinone and water in such an amount that gave a total amount of 650 g to provide a coating solution. The coating solution was mixed with 445 ml of a solution containing 4 % by weight chromium alum and 0.67 % by weight of phthalic acid by a static mixer immediately before coating to form a coating solution for surface protective layer, which was fed to a coating die in such an amount that gave a coating amount of 8.3 ml/m².

[0296] The viscosity of the coating solution measured by a B-type viscometer (Rotor No. 1, 60 rpm) at 40°C was 9 [mPa·s].

21. Preparation of thermally processed image recording material

[0297] On the back side of the aforementioned support having an undercoat layer, the coating solution for antihalation layer and the coating solution for back surface protective layer were simultaneously applied as stacked layers so that the applied solid content amount of the solid microparticle dye in the antihalation layer should be 0.04 g/m², and the applied amount of gelatin in the protective layer should be 1.7 g/m², and dried to form an antihalation back layer.

[0298] Then, on the side opposite to the back side, an emulsion layer (coated silver amount of the silver halide was 0.14 g/m²), intermediate layer, first protective layer, and second protective layer were simultaneously applied in this order from the undercoat layer by the slide bead application method as stacked layers to form a sample of thermally processed image recording material.

[0299] The coating was performed at a speed of 160 m/min. The gap between the tip of coating die and the support was set to be 0.14 to 0.28 mm, and the coated width was controlled so that it spread by each 0.5 mm at both sides compared with the projecting slit width of the coating solution. The pressure in the reduced pressure chamber was adjusted to be lower than the atmospheric pressure by 392 Pa. In this case, handling, temperature and humidity were controlled so that the support should not be electrostatically charged and further electrostatic charge was eliminated by ionized wind immediately before the coating. In the subsequent chilling zone, the material was blown with air showing a dry-bulb temperature of 18°C and a wet-bulb temperature of 12°C for 30 seconds to cool the coating solutions. Then, in the floating type drying zone in a coiled shape, the material was blown with drying air showing a dry-bulb temperature of 30°C and a wet-bulb temperature of 18°C for 200 seconds. Subsequently, the material was passed through a drying zone of 70°C for 20 seconds, and then another drying zone of 90°C for 10 seconds, and cooled to 25°C to evaporate the solvent in the coating solution. The average wind velocities of the wind applied to the coated layer surface in the chilling zone and the drying zones were 7 m/sec.

22. Evaluation of photographic performance

[0300] After each thermally processed image recording material was light-exposed by a laser sensitometer (details are given below), the thermally processed image recording material was treated at 118°C for 5 seconds and then treated at 122°C for 16 seconds (heat development).

Laser sensitometer:

[0301] 

Combination of two diode lasers of 660 nm showing an output of 35 mW.

Single mode.

Gaussian beam spot 1/e² of 100 µm.

[0302] The light source was proceeded along the sub-scanning direction at a pitch of 25 µm and each pixel was written 4 times.

[0303] The evaluation of the image obtained was performed by using a Macbeth TD904 densitometer (visible density). The measurement results were evaluated as Dmin, sensitivity (evaluated by a relative value of a reciprocal of a ratio of exposure amounts giving a density higher than Dmin by 1.0, and the sensitivity of the thermally processed image recording material of Experiment No. 1 shown in Table 1 below was defined as 100), Dmax, and gradation (contrast) (fresh photographic properties). The contrast was expressed by a gradient of a straight line connecting the points at the densities from which the value for Dmin was subtracted, 0.5 and 1.5, with the abscissa being a logarithm of the exposure amount.

[0304] As for the evaluation of image storage stability, Image storage stability 1 shows the change of the photographic properties after storing the thermally processed image recording materials after heat development in the dark for 24 hours at a temperature of 60°C and relative humidity of 50%, and Image storage stability 2 shows the change of the photographic properties after storing them for 24 hours under the light irradiation of 10,000 luces at a temperature of 40°C and relative humidity of 50%.

[0305] As seen from the results shown in Tables 1 and 2, when the specific compounds for the invention were used for the thermally processed image recording materials, good photographic performance and good image storage stability could be obtained.

〈Example 2〉

[0306] The structures of the compounds used in Example 2 are shown below.

1. Preparation of silver halide emulsion (Emulsion A)

[0307] 11 g of alkali-treated gelatin (calcium content of 2700 ppm or less), 30 mg of potassium bromide and 10 mg of sodium benzenesulfonate were dissolved in 700 ml of water, and the pH of the mixture was adjusted to pH 5.0 at a temperature of 40°C, and added with 159 ml of an aqueous solution containing 18.6 g of silver nitrate and an aqueous solution containing 1 mole/liter of potassium bromide, 5 × 10^-6 mole/liter of (NH₄)₂RhCl₅ (H₂O), and 2 × 10^-5 mole/liter of K₃IrCl₆ by the control double jet method over a period of 6 minutes and 30 seconds, while the pAg was kept at 7.7. Then, the solution was added with 476 ml of an aqueous solution containing 55.5 g of silver nitrate and an aqueous halide salt solution containing 1 mole/liter of potassium bromide and 2 × 10^-5 mole/liter of K₃IrCl₆ by the control double jet method over a period of 28 minutes and 30 seconds, while the pAg was kept at 7.7. Thereafter, by lowering the pH to cause aggregation and precipitation to attain a desalting treatment. The mixture was added with 0.17 g of Compound A and 51.1 g of low molecular weight gelatin having an average molecular weight of 15,000 (calcium content: 20 ppm or less), and the pH and pAg of the mixture were adjusted to 5.9 and 8.0, respectively. The obtained grains were cubic grains having a mean grain size of 0.08 µm, a variation coefficient of 9% for projected area and a [100] face ratio of 90%.

[0308] The silver halide grains obtained as described above were warmed to a temperature of 60°C, added with 76 µmoles of sodium benzenesulfonate per mole of silver, and after 3 minutes, added with 71 µmoles of triethylthiourea. Then, the mixture was ripened for 100 minutes, and added with 5 × 10^-4 mole of 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, and the temperature of the mixture was lowered to 40°C.

[0309] Thereafter, while the mixture was kept at a temperature of 40°C, the mixture was added with 12.8 × 10^-4 mole of Sensitizing dye A and 6.4 × 10^-3 mole of Compound B per mole of silver halide with stirring. After 20 minutes, the mixture was quenched to 30°C to finish the preparation of Silver halide emulsion A.

2. Preparation of organic silver salt dispersion (Organic silver salt A)

[0310] 87.6 kg of behenic acid (Edenor C22-85R, trade name, manufactured by Henkel Co.), 423 L of distilled water, 49.2 L of a 5 mol/L aqueous solution of NaOH and 120 L of tert-butanol were mixed and allowed to react with stirring at 75°C for one hour to obtain a solution of sodium behenate. Separately, 206.2 L of an aqueous solution containing 40.4 kg of silver nitrate was prepared and kept at 10°C. A mixture of 635 L of distilled water and 30 L of tert-butanol contained in a reaction vessel kept at 30°C was added with the whole amount of the aforementioned sodium behenate solution and the whole amount of the aqueous silver nitrate solution at constant flow rates over the periods of 62 minutes and 10 seconds, and 60 minutes, respectively. In this case, they were added in such a manner that only the aqueous silver nitrate solution was added for 7 minutes and 20 seconds after starting the addition of the aqueous silver nitrate solution, and for 9 minutes 30 seconds after finishing the addition of the aqueous silver nitrate solution, only the sodium behenate solution was added. In this operation, the outside temperature was controlled so that the temperature in the reaction vessel should become 30°C and the liquid temperature should not be raised. The piping of the addition system for the sodium behenate solution was maintained by steam trace and the steam amount was controlled such that the liquid temperature at the outlet orifice of the addition nozzle should be 75°C. The piping of the addition system for the aqueous silver nitrate solution was maintained by circulating cold water outside a double pipe. The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically with respect to the stirring axis as the center, and the positions are controlled at heights for not contacting with the reaction liquid.

[0311] After finishing the addition of the sodium behenate solution, the mixture was left with stirring for 20 minutes at the same temperature and then the temperature was decreased to 25°C. Thereafter, the solid content was recovered by a suction filtration and the solid content was washed with water until electric conductivity of the filtrate became 30 µS/cm. The solid content obtained as described above was stored as a wet cake without being dried.

[0312] When the shape of the obtained silver behenate grains was evaluated by an electron microscopic photography, the grains were scaly crystals having a mean diameter of projected area of 0.52 µm, a mean grain thickness of 0.14 µm, and a variation coefficient of 15% for mean diameter as spheres.

[0313] Then, a dispersion of silver behenate was prepared as follows. To the wet cake corresponding to 100 g of the dry solid content was added with 7.4 g of polyvinyl alcohol (PVA-217, trade name, average polymerization degree: about 1700) and water to make the total amount 385 g, and the mixture was pre-dispersed by a homomixer. Then, the pre-dispersed stock dispersion was treated three times by using a dispersing machine (Microfluidizer-M-110S-EH; trade name, manufactured by Microfluidex International Corporation, using G10Z interaction chamber) with a pressure controlled to be 1750 kg/cm² to obtain a silver behenate dispersion. During the cooling operation, a desired dispersion temperature was achieved by providing coiled heat exchangers fixed before and after the interaction chamber and controlling the temperature of the refrigerant.

[0314] The silver behenate grains contained in the silver behenate dispersion obtained as described above were grains having a volume weight mean diameter of 0.52 µm and a coefficient of variation of 15%. The measurement of the grain size was carried out by using Master Sizer X manufactured by Malvern Instruments Ltd. When the grains were evaluated by an electron microscopic photography, the ratio of the long side to the short side was 1.5, the grain thickness was 0.14 µm and a mean aspect ratio (ratio of circular diameter of projected area of grain and grain thickness) was 5.1.

3. Preparation of dispersion of solid microparticles of reducing agent: 1,1-bis(2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane

[0315] 25 g of 1,1-bis(2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane was added with 25 g of a 20 % by weight aqueous solution of MP polymer (MP-203, manufactured by KURARAY CO., LTD.), 0.1 g of Safinol 104E manufactured by Nisshin Kagaku K.K., 2 g of methanol and 48 ml of water and the mixture was stirred sufficiently to form a slurry, which was left for 3 hours as slurry. Then, 360 g of zirconia beads having a mean diameter of 1 mm were placed in a vessel together with the slurry and the slurry was dispersed by a dispersing machine (1/4G Sand Grinder Mill; manufactured by Imex Co.) for 3 hours to prepare a dispersion of reducing agent solid microparticles. As for the particle sizes, 80% of the particles had a particle size of 0.3 µm to 1.0 µm.

4. Preparation of solid microparticle dispersion of compound of formula (1)

[0316] 30 g of each of the compounds of the formula (1) shown in Tables 3 and 4 was added with 4 g of MP polymer (MP-203 manufactured by KURARAY CO., LTD.), 0.25 g of Compound C and 66 g of water and the mixture was stirred sufficiently to form a slurry. Thereafter, 200 g of zirconia silicate beads having a diameter of 0.5 mm were placed in a vessel together with the slurry and the slurry was dispersed by a dispersing machine (1/16 G Sand Grinder Mill; manufactured by Imex Co.) for 5 hours to prepare a solid microparticle dispersion. In the particles, 80 % by weight of the particles had a diameter of 0.3 µm to 1.0 µm. Each of Comparative Compounds was also dispersed in the same manner as above.

5. Preparation of solid microparticle dispersion of Ultrahigh contrast agent B

[0317] 10 g of Ultrahigh contrast agent B was added with 2.5 g of polyvinyl alcohol (PVA-217, manufactured by KURARAY CO., LTD.) and 87.5 g of water and the mixture was stirred sufficiently to form a slurry, which was left for 3 hour as slurry. Thereafter, 240 g of zirconia beads having a diameter of 0.5 mm were placed in a vessel together with the slurry and the slurry was dispersed by a dispersing machine (1/4 G Sand Grinder Mill; manufactured by Imex Co.) for 10 hours to prepare a solid microparticle dispersion. In the particles, 80 % by weight of the particles had a size of 0.1 µm to 1.0 µm, and the mean particle size was 0.5 µm.

6. Preparation of solid microparticle dispersion of Compound Z

[0318] 30 g of Compound Z was added with 3 g of MP polymer (MP-203, manufactured by KURARAY CO. LTD.) and 87 ml of water, and the mixture was stirred sufficiently to form a slurry, which was left for 3 hours as slurry. Thereafter, by following the same procedure as the preparation of the aforementioned solid microparticle dispersion of the reducing agent, a solid microparticle dispersion of Compound Z was prepared. In the particles, 80 % by weight of the particles had a size of 0.3 µm to 1.0 µm.

7. Preparation of coating solution for emulsion layer

[0319] To 1 mole of silver of the organic acid silver salt microcrystal dispersion prepared as described above were added the following binder, materials, Silver halide emulsion A and water to provide a coating solution for emulsion layer.

Binder; Laxster 3307B (made by DAINIPPON INK AND CHEMICALS, INC.; SBR latex, glass transition temperature: 17°C)	500 g as solid content
1,1-Bis(2-hydroxy-3,5-dimethylphenyl-3,5,6-trimethylhexane	149 g as solid content
Compound of the formula (1)	Type and amount (mole) shown in Table 2
Ultrahigh contrast agent B	15 g as solid content
Sodium ethylthiosulfonate	0.15 g
4-Methylbenzotriazole	1.04 g
Polyvinyl alcohol (PVA-235, made by KURARAY CO. LTD.)	10.8 g
6-Isopropylphthalzine	15.0 g
Sodium dihydrogen-orthophsophsate·dihydride	0.37 g
Compound Z	9.7 g as solid content
Dye A	Amount giving an optical density of 0.3 at 783 nm (about 0.37 g)
Silver halide emulsion A	0.06 mole as Ag

8. Preparation of coating solution for lower protective layer of emulsion layer surface

[0320] 956 g of a polymer latex solution of methyl methacrylate/styrene/2-ethylhexyl acrylate/2-hydroxyethyl methacrylate/acrylic acid copolymer = 58.9/8.6/25.4/5.1/2 (% by weight) having a particle size of 120 nm (glass transition temperature: 57°C. solid content concentration: 21.5 % by weight, containing Compound D as film-forming aid in an amount of 15 % by weight relative to the solid content of the latex) was added with water, and then added with 1.62 g of Compound E, 3.15 g of Compound S, 1.98 g of a matting agent (polystyrene particles, mean particle size: 7 µm), 23.6 g of polyvinyl alcohol (PVA-235, manufactured by KURARAY CO., LTD.) and water to prepare a coating solution.

9. Preparation of coating solution for upper protective layer of emulsion layer surface

[0321] 630 g of a polymer latex containing copolymer of methyl methacrylate/styrene/2-ethylhexyl acrylate/2-hydroxyethyl methacrylate/acrylic acid = 58.9/8.6/25.4/5.1/2 (% by weight) (glass transition temperature: 54°C, solid content: 21.5 % by weight, mean particle diameter: 70 nm, containing Compound D as a film-forming aid in an amount of 15 % by weight as to solid content of the latex) was added with H₂O, 6.30 g of 30 % by weight solution of carnauba wax (Cellosol 524, Chukyo Yushi Co., Ltd.), 0.72 g of Compound E, 7.95 g of Compound F, 0.09 g of Compound S, 1.18 g of a matting agent (polystyrene particles, mean diameter: 7 µm) and 8.30 g of polyvinyl alcohol (PVA-235, Kuraray Co., Ltd.) and further added with H₂O to form a coating solution.

10. Preparation of PET support having backing layer/undercoat layer

(1) Support

[0322] Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity IV of 0.66 (measured in phenol/tetrachloroethane = 6/4 (weight ratio) at 25°C) was obtained in a conventional manner. The PET was pelletized, and the pellets were dried at 130°C for 4 hours, melted at 300°C, extruded from a T-die, and quenched to prepare an unstretched film having such a thickness that the film thickness after thermal fixation should become 120 µm.

[0323] The film was stretched along the longitudinal direction by 3.3 times using rollers having different peripheral speeds and then stretched along the transverse direction by 4.5 times using a tenter. In this case, the temperatures were 110°C and 130°C, respectively. Thereafter, the film was subjected to thermal fixation at 240°C for 20 seconds and relaxed by 4% along the transverse direction at the same temperature. Then, after chucks of the tenter were released, the both edges of the film were knurled, and the film was rolled up at 4.8 kg/cm² to provide a roll of the film having a width of 2.4 m, length of 3500 m and thickness of 120 µm.

(2) Undercoat layer (a):

[0324] 

Polymer latex (1) (core shell type latex comprising 90 % by weight of core and 10 % by weight of shell, core: vinylidene chloride/methyl acrylate/methyl methacrylate/acrylonitrile/acrylic acid = 93/3/3/0.9/0.1 (% by weight), shell: vinylidene chloride/methyl acrylate/methyl methacrylate/acrylonitrile/acrylic acid = 88/3/3/3/3 (% by weight), weight average molecular weight; 38000)	3.0 g/m2 as solid content
2,4-Dichloro-6-hydroxy-s-triazine	23 mg/m2
Matting agent (polystyrene, mean diameter; 2.4 µm)	1.5 mg/m2

(3) Undercoat layer (b)

[0325] 

Deionized gelatin (Ca2+ content; 0.6 ppm, jelly strength; 230 g)

50 mg/m2

(4) Electroconductive layer

[0326] 

Julimer ET-410 (Nihon Junyaku Co., Ltd.)	96 mg/m2
Alkali-treated gelatin (molecular weight; about 10000, Ca2+ content; 30 ppm)	42 mg/m2
Deionized gelatin (Ca2+ content; 0.6 ppm)	8 mg/m2
Compound A	0.2 mg/m2
Polyoxyethylene phenyl ether	10 mg/m2
Sumitex Resin M-3 (water-soluble melamine resin, Sumitomo Chemical Co., Ltd.)	18 mg/m2
Dye A	Amount giving optical density of 1.2 at 783 nm
SnO2/Sb (weight ratio: 9/1, acicular grains, long axis/short axis = 20-30, Ishihara Sangyo Kaisha, Ltd.)	160 mg/m2
Matting agent (Polymethyl methacrylate, mean particle size: 5 µm)	7 mg/m2

(5) Protective layer

[0327] 

Polymer latex (2) (copolymer of methyl methacrylate/styrene/ 2-ethylhexyl acrylate/2-hydroxyethyl methacrylate/acrylic acid = 59/9/26/5/1 (% by weight))	1000 mg/m2 as solid content
Polystyrenesulfonate (molecular weight: 1000-5000)	2.6 mg/m2
Cellosol 524 (Chukyo Yushi Co., Ltd.)	25 mg/m2
Sumitex Resin M-3 (water-soluble melamine compound, Sumitomo Chemical Co., Ltd.)	218 mg/m2

(6) Preparation of PET support with backing layer and undercoat layer

[0328] Undercoat layer (a) and Undercoat layer (b) were applied successively on both sides of the support (base), and each dried at 180°C for 4 minutes. Then, an electroconductive layer and a protective layer are successively applied to one side provided with Undercoat layer (a) and Undercoat layer (b), and each dried at 180°C for 4 minutes to prepare a PET support having backing layers and undercoat layers. The dry thickness of Undercoat layer (a) was 2.0 µm.

(7) Heat treatment during transportation

(7-1) Heat treatment

[0329] The PET support with backing layers and undercoat layers prepared as described above was introduced into a heat treatment zone having a total length of 200 m set at 160°C, and transported at a tension of 3 kg/cm² and a transportation speed of 20 m/minute.

(7-2) Post-heat treatment

[0330] Following the aforementioned heat treatment, the support was passed through a zone at 40°C for 15 seconds for post-heat treatment, and rolled up. The rolling up tension for this operation was 10 kg/cm².

11. Preparation of thermally processed image recording material

[0331] On the undercoat layers of the aforementioned PET support coated with Undercoat layer (a) and Undercoat layer (b), the coating solution for emulsion layer was coated so that the coated silver amount should become 1.6 g/m². Further, the coating solution for lower protective layer for emulsion surface was coated on the emulsion layer simultaneously with the coating solution for emulsion layer as laminated layers, so that the coated solid content of the polymer latex should be 1.31 g/m². Then, the coating solution for upper protective layer for emulsion surface was coated on the coated layer, so that the coated solid content of the polymer latex should be 3.02 g/m² to obtain a thermally processed image recording material. The film surface pH of the obtained thermally processed image recording material on the image-forming layer side was 4.9, and the Beck's smoothness was 660 seconds. As for the opposite surface, the film surface pH was 5.9 and the Beck's smoothness was 560 seconds.

12. Evaluation of photographic performance

(Light exposure)

[0332] The obtained thermally processed image recording material was light exposed for 2 × 10^-8 seconds by using a laser light-exposure apparatus of single channel cylindrical inner surface type provided with a semiconductor laser with a beam diameter (1/2 of FWHM of beam intensity) of 12.56 µm, laser output of 50 mW and output wavelength of 783 nm. The exposure time was adjusted by controlling the mirror revolution number, and exposure was adjusted by changing output. The overlap coefficient of the light exposure was 0.449.

(Heat development)

[0333] Each light-exposed thermally processed image recording material was heat-developed by using a heat-developing apparatus as shown in Fig.1. The roller surface material of the heat development section was composed of silicone rubber, and the flat surface consisted of Teflon non-woven fabric. The heat development was performed at a transportation linear speed of 20 mm/second and a temperature of 90-110°C in the preheating section for 15 seconds (driving units of the preheating section and the heat development section were independent from each other, and speed difference as to the heat development section was adjusted to -0.5% to -1%), and 120°C for 20 seconds in the heat development section, and for 15 seconds in the gradual cooling section. The temperature precision as for the transverse direction was ±1°C.

(Evaluation of photographic performance)

[0334] The evaluation of the image obtained was performed by using a Macbeth TD904 densitometer (visible density). The measurement results were evaluated as Dmin, sensitivity (evaluated by a relative value of a reciprocal of a ratio of exposure amounts giving a density higher than Dmin by 1.0, and the sensitivity of the thermally processed image recording material of Experiment No. 1 shown in Table 1 below was defined as 100), Dmax, and gradation (contrast) (fresh photographic properties). The contrast was expressed by a gradient of a straight line connecting the points at the densities from which the value for Dmin was subtracted, 0.3 and 1.5, with the abscissa being a logarithm of the exposure amount.

[0335] As for the evaluation of image storage stability, Image storage stability 1 shows the change of the photographic properties after storing the thermally processed image recording materials after heat development in the dark for 24 hours at a temperature of 60°C and relative humidity of 50%, and Image storage stability 2 shows the change of the photographic properties after storing them for 24 hours under the light irradiation of 10,000 luces at a temperature of 40°C and relative humidity of 50%.

[0336] As seen from the results shown in Tables 3 and 4, when the specific compounds for the invention were used for the thermally processed image recording materials, good photographic performance (sensitivity, fog, gradation)and good image storage stability could be obtained.

Claims

1. A thermally processed image recording material which comprises, on a support, at least (a) a reducible silver salt, (b) a reducing agent, (c) a binder, and (d) at least one kind of compound having a melting point of 115°C to 180°C which is selected from the group consisting of polyhalogenated compounds represented by the following formula (1) and dimer compounds thereof:

wherein Z¹ and Z² independently represent a halogen atom, X¹ represents a hydrogen atom or an electron withdrawing group, Y¹ represents -CO- group or -SO₂-, Q represents an arylene group which may have one or more substituents or a divalent heterocyclic group which may have one or more substituents, L¹ represents -CONH-*, -SO₂NH-* or -COO-* where * represents a bonding site for W, L² represents -O-, an alkylene group, an arylene group or a combination thereof, W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group where the groups mentioned in the definition of W may have one or more substituents, and n represents 0 or 1.

2. A thermally processed image recording material which comprises, on a support, at least (a) a reducible silver salt, (b) a reducing agent, (c) a binder, and (d) at least one kind of compound having a log P value of 3.0 to 7.0 which is selected from the group consisting of polyhalogenated compounds represented by the following formula (1) and dimer compounds thereof:

wherein Z¹ and Z² independently represent a halogen atom, X¹ represents a hydrogen atom or an electron withdrawing group, Y¹ represents -CO- group or -SO₂-, Q represents an arylene group which may have one or more substituents or a divalent heterocyclic group which may have one or more substituents, L¹ represents -CONH-*, -SO₂NH-* or -COO-* where * represents a bonding site for W, L² represents -O-, an alkylene group, an arylene group or a combination thereof, W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group where the groups mentioned in the definition of W may have one or more substituents, and n represents 0 or 1.

3. The thermally processed image recording material according to claim 1 or 2, wherein, in the formula (1), Z¹, Z² and X¹ represent a bromine atom, Y¹ represents -SO₂-, Q represents an arylene group which may have one or more substituents, W represents a hydrogen atom or an alkyl group which may have one or more substituents, and n is 0.

4. The thermally processed image recording material according to any one of claims 1-3, which further comprises a photosensitive silver halide.

5. The thermally processed image recording material according to any one of claims 1-4, wherein the compound represented by the formula (1) has a melting point of 115°C to 180°C and a log P value of 3.0 to 7.0.

6. The thermally processed image recording material according to any one of claims 1-5, wherein the compound represented by the formula (1) has a log P value of 3.5 to 6.0.

7. The thermally processed image recording material according to any one of claims 1-6, wherein the electron withdrawing group represented by X¹ in the formula (1) is cyano group, a C_2-30 alkoxycarbonyl group, a C_7-30 aryloxycarbonyl group, a C_1-30 carbamoyl group, a sulfamoyl group with may be substituted with a C_0-30 alkyl group, a C_1-30 alkylsulfonyl group, a C_6-30 arylsulfonyl group, a halogen atom or an acyl group.

8. The thermally processed image recording material according to any one of claims 1-7, wherein the substituent on the arylene group represented by Q in the formula (1) is selected from a group consisting of a halogen atom such as fluorine atom, chlorine atom, bromine atom or iodine atom; an alkyl group including a cycloalkyl group, an active methine group and so forth; an aralkyl group; an alkenyl group; an alkynyl group; an aryl group; a heterocyclic group including N-substituted nitrogen-containing heterocyclic group such as morpholino group; an alkoxycarbonyl group; an aryloxycarbonyl group; a carbamoyl group; an imino group; an imino group substituted at the N atom; a thiocarbonyl group; a carbazoyl group; cyano group; a thiocarbamoyl group; an alkoxy group; an aryloxy group; a heterocyclyloxy group; an acyloxy group; an (alkoxy or aryloxy)carbonyloxy group; a sulfonyloxy group; an acylamino group; a sulfonamido group; a ureido group; a thioureido group; an imido group; an (alkoxy or aryloxy)carbonylamino group; a sulfamoylamino group; a semicarbazide group; a thiosemicarbazide group; an (alkyl or aryl)sulfonylureido group; a nitro group; an (alkyl or aryl)sulfonyl group; a sulfamoyl group; a group containing phosphoric acid amide or phosphoric acid ester structure; and a silyl group.

9. The thermally processed image recording material according to any one of claims 1-8, wherein the heterocycle in the heterocyclic group represented by Q in the formula (1) is a ring of pyridine, pyrazine, pyrimidine, benzothiazole, benzimidazole, thiadiazole, quinoline, isoquinoline or triazole.

10. The thermally processed image recording material according to any one of claims 1-9, wherein L¹ in the formula (1) represents -CONH-*,

11. The thermally processed image recording material according to any one of claims 1-10, wherein the compounds represented by the formula (1) is added to the image-forming layer or a layer adjacent thereto.

12. The thermally processed image recording material according to any one of claims 1-11, wherein the compounds represented by the formula (1) is added in an amount of 1 × 10^-4 to 1 mole per mole of the light insensitive silver salt of the image-forming layer.

Drawing