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(11) | EP 0 943 956 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Radiographic material having antispot protection and improved speed to Dmin ratio |
| (57) The present invention relates to a process for manufacturing a silver halide photographic
material comprising the step of adding to a silver halide emulsion a polyamine-polycarboxyl
derivative and an aryl compound having at least two hydroxyl groups and at least one
additional substituent represented by a sulfonic group, an hydroxyl group, a carboxy
group or a hydroxymethyl group. The use of such a combination as antispotting agent
to prevent metal contamination and to increase the speed to Dmin ratio of a silver
halide photographic emulsion and a silver halide element comprising such an aryl compound
is also claimed. |
FIELD OF THE INVENTION
[0001] The present invention relates to a silver halide radiographic material. More particularly, the present invention relates to the combination of a polyamine-polycarboxyl derivative and an aryl derivative in a process to prepare a silver halide emulsion to preserve the resulting photographic material from spot defects due to metallic contamination and to increase the speed to Dmin ratio thereof.
BACKGROUND OF THE INVENTION
[0002] Silver halide emulsions are usually prepared by precipitating silver halide (silver bromide, silver iodide, silver chloride or mixture thereof) in the presence of a hydrophilic colloid (normally gelatin). Afterwards, the silver halide emulsions have to be subjected to a sensitization process for increasing their sensitivity to light. The sensitization process mainly involves spectral sensitization and chemical sensitization. Spectral sensitization comprises the addition of spectral sensitizing dyes which can be adsorbed on the silver halide grain surface in order to make the emulsion sensitive to visible or infrared radiation. Chemical sensitization comprises the addition of various chemical substances to obtain a prescribed value of sensitivity and contrast. Typical methods for chemical sensitizing a silver halide photographic emulsion include sulfur sensitization, noble metal sensitization, and reduction sensitization. It is also common in the art to have combination methods, such as sulfur-noble metal sensitization, reduction-noble metal sensitization, and the like. A number of patents and patent applications, as well as literature references discloses specific methods to improve chemical sensitization. For example, Research Disclosure, September 1994, Item 36544, Paragraph IV, pp. 510-511, gives a wide array of references for each of the above-mentioned methods.
[0003] In recent years, there has been a strong demand for high sensitivity, low graininess and low fog in a silver halide photographic element as well as for rapid processing in which development is expedited. Various improvements in the above sensitizing methods have been made.
[0004] One approach focuses on the addition of coating aids. After the sensitization process, the silver halide emulsion is coated on a support together with coating additives. A wide description of useful coating aids can be found in Research Disclosure No. 38597, September 1996, "Photographic Silver Halide Emulsions, Preparations, Addenda, Systems and Processing", Item IX.
[0005] Another improvement area is in the preparation of silver halide elements. It is important that the silver halide elements be free from any metal contamination. However, fine metal particles are produced by the equipment which is used during the manufacturing process itself. This problem can occur during any step from the base preparation to final coating. Even if different metals like copper or nickel can be present on the final material, the main metal contaminant is constituted by fine iron particles. The presence of iron ions like Fe in oxidation state (III) can desensitize the silver halide and produce a lower density halo on the developed film creating a white spot. The presence of fine metallic iron particles or iron ions like Fe in oxidation state (II) can generate, by oxidation, the release of one or two electrons, which produce sensitized halo on the developed film creating black spots. The terms white or black spot are relative terms merely meaning that the spot appear whiter or blacker than the surrounding non-contaminated area of the film. Such spots in developed image can give bad image quality and be unacceptable in many photographic films,especially in an X-ray application where these spots can interfere with medical diagnosis. One known approach for controlling or eliminating these defects is to add a sequestering or chelating agent. The chemical compound gives generally a strong complex with the metal and can remove them from the photosensitive element. The final effect is effectively to prevent spot formation in silver halide photographic film.
[0006] US Patent 3,443,951 discloses the use of phosphoric acid esters in photographic element to prevent spot formation caused by metal particles.
[0007] US Patent 4,340,665 discloses the use of phosphate and amine complexing agents in synergistic combination to reduce spot formation caused by iron contamination of photographic element.
[0008] US Patent 3,925,086 discloses the use of azotriazoles and azotetrazoles as antispot agent in photographic silver halide emulsion or in processing baths.
[0009] US Patent 3,300,312 discloses the use of sulfosalicylic acid in photographic elements to reduce spotting from metallic particles.
[0010] EP 733,940 discloses the use of both phosphate and sulfosalicylic acid in photographic elements to reduce spotting from spurious metal particle contamination.
[0011] GB Patent 1,350,303 discloses the use of thienyl or furyl compound to reduced tendency to spot formation due to metal or metal oxide contamination.
[0012] GB Patent 1,350,302 discloses the use of aldoxime compound to reduced tendency to spot formation due to metal or metal oxide contamination.
[0013] US Patent 4,340,665 discloses the use of phosphate and hydroxyethylene diamine triacetate in photographic silver halide materials to reduce metal particle contamination.
[0014] These methods provide substantial spot decrease; however, a loss of sensitometric properties is usually observed.
[0015] Hydroxy substituted aryl compounds are described, for example, in the patents and patent applications described hereinbelow.
[0016] US 5,028,520 discloses the use of hydroquinone sulfonic acid potassium salt on tabular silver halide emulsion in an amount of from 0.03 to 0.5 moles per mole of silver to decrease the surface glossiness. It is also disclosed that no effect is obtained with amount lower than 0.03 mole per mole of silver.
[0017] JP 54-040729, JP 56-001936 and JP 62-021143 disclose the use of polyhydroxybenzene derivatives on cubic silver halide emulsions to decrease pressure sensitivity in graphic art films.
[0018] EP 452772, EP 476521, EP 482599 and EP 488029 disclose the use of polyhydroxybenzene derivatives with functional groups that allow better silver halide grain adsorption to decrease pressure sensitivity of final film.
[0019] EP 339870 discloses a silver halide photographic emulsion having in reactive association a sensitizing amount of polyalkylene glycol compound and a fog reducing amount of an arylhydroxy compound.
[0020] European Patent Application No. 97-116341.5 discloses the use of aryl derivative in a process to prepare a silver halide emulsion to improve the speed to Dmin ratio of the resulting photographic materials.
[0021] European Patent Application No. 97-116342.3 discloses the use of aryl derivative in a process to prepare a silver halide emulsion to preserve from spot defects due to metallic contamination the resulting photographic materials.
SUMMARY OF THE INVENTION
[0022] The present invention provides a process for manufacturing a silver halide photographic material comprising the step of adding to a silver halide emulsion a polyamine-polycarboxyl derivative and an aryl compound having at least two hydroxyl groups and at least one additional substituent represented by a sulfonic group, an hydroxyl group, a carboxy group or a hydroxymethyl group.
[0023] In another embodiment of the present invention, a silver halide photographic element is provided comprising at least one silver halide emulsion layer coated on a support base, wherein said silver halide emulsion layer comprises a combination of a polyamine-polycarboxyl derivative and an aryl compound having at least two hydroxyl groups and at least one additional substituent represented by a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group.
[0024] In yet another embodiment, the present invention relates to the use of a combination of a polyamine-polycarboxyl derivative and an aryl compound having at least two hydroxyl groups and at least one additional substituent represented by a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group to preserve from spot defects due to metallic a silver halide photographic emulsion comprising silver halide tabular grains and to increase the speed to Dmin ratio thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The manufacturing process of silver halide elements usually comprises an emulsion-making step, a chemical and optical sensitization step, and a coating step. The silver halide emulsion-making step generally comprises a nucleation step, in which silver halide grain seeds are formed, followed by one or more growing steps, in which the grain seeds achieve their final dimension, and a washing step, in which all soluble salts are removed from the final emulsion. A ripening step is usually performed between the nucleation and growing step and/or between the growing and the washing steps. The resulting silver halide emulsion is then coated on a proper support to prepare a silver halide photographic material.
[0026] According to the method of the present invention, a polyamine-polycarboxyl derivative and an aryl compound having at least two hydroxyl groups and at least one additional substituent represented by a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group is added to the silver halide emulsion at any time before the coating of the silver halide emulsion. The term "any time before the coating" means during or after the emulsion-making step, before, during or after the chemical and optical sensitization step, or just before coating. According to a preferred embodiment of the process of the present invention the polyamine-polycarboxyl derivative and aryl compound combination is added just before coating.
[0027] Preferably, the polyamine-polycarboxyl derivative is represented by the following formula:
wherein Z is a divalent organic linking group, R1 and R2, equal or different, can be a hydrogen atom, an aryl group or a -(CH2)p-COOH group, and n, m, and p, equal or different, are an integer from 1 to 3.
[0028] Useful examples of the divalent organic linking group Z are represented by an alkylene group of from 1 to 10 carbon atoms, an arylene group, an alkylarylene group, an aralkylene group, a cycloalkylene group, and the like.
[0029] When the term "group" or "residue" is used in this invention to describe a chemical compound or substituent, the described chemical material includes the basic group or residue and that group or residue with conventional substitution. For example, "alkylene group" includes not only such alkyl moiety as methylene, ethylene, butylene, octylene, and the like, but also moieties bearing substituent groups such as halogen, cyano, hydroxyl, nitro, amino, carboxylate, and the like.
[0030] One or more carbon atoms of the divalent organic linking groups Z described above can be replaced by one or more heteroatoms such as nitrogen, sulfur, or oxygen. The nitrogen atom can also be further substituted by an alkyl group having from 1 to 3 carbon atoms or a -(CH2)p-COOH group.
[0031] According to a preferred embodiment of the present invention, the polyamine-polycarboxyl derivative is represented by the following formula:
wherein Z1 and Z2 are represented by an alkylene chain of from 1 to 5 carbon atoms, R1 and R2, equal or different, can be a hydrogen atom, an aryl group or a - (CH2)p-COOH group, and n, m, and p, equal or different, are an integer from 1 to 3.
[0032] Useful examples of polyamine-polycarboxyl derivatives represented by the above mentioned general formula are listed below.
[0033] The addition amount of the above described polyamine-polycarboxyl derivatives is lower than 30 millimoles per mole of silver, preferably in the range of from 0.1 to 30 millimoles per mole of silver, more preferably from 1 to 30 millimoles per mole of silver, and most preferably from 5 to 30 millimoles per mole of silver. When expressed in terms of millimoles per square meter per side of the resulting silver halide radiographic material the above mentioned amounts corresponds to an amount lower than 0.6, preferably in the range of from 0.002 to 0.6, more preferably from 0.02 to 0.6, and most preferably from 0.1 to 0.6 millimoles per square meter per side.
[0034] Preferably, the aryl compound is represented by the following formula:
wherein R is a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group and n is an integer of from 1 to 4.
[0035] More preferably, the aryl compound is represented by the following formula:
wherein R is a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group and n is an integer of from 1 to 4.
[0036] Most preferably, the aryl compound is represented by the following formula:
wherein R is a sulfonic group and n is an integer of from 1 to 4.
[0037] Useful examples of aryl compounds represented by the above mentioned general formula are listed below.
[0038] The addition amount of the above described aryl compound is typically lower than 30 millimoles per mole of silver, preferably in the range of from 0.1 to 30 millimoles per mole of silver, more preferably from 1 to 30 millimoles per mole of silver, and most preferably from 5 to 30 millimoles per mole of silver. When expressed in terms of millimoles per square meter per side of the resulting silver halide radiographic material the above mentioned amounts corresponds to an amount lower than 0.6, preferably in the range of from 0.002 to 0.6, more preferably from 0.02 to 0.6, and most preferably from 0.1 to 0.6 millimoles per square meter per side.
[0039] Silver halide emulsions useful in the present invention can be prepared using a single-jet method, a double-jet method, or a combination of these methods and can be ripened using, for instance, an ammonia method, a neutralization method, or an acid method. Parameters which may be adjusted to control grain growth include pH, pAg, temperature, shape and size of reaction vessel, and the reaction method (e.g., accelerated or constant flow rate precipitation, interrupted precipitation, ultrafiltration during precipitation, reverse mixing processes and combinations thereof). A silver halide solvent, such as ammonia, thioethers, thioureas, etc., may be used, if desired, for controlling grain size, grain structure, particle size distribution of the grains, and the grain-growth rate. Methods for preparing silver halide emulsions are generally known to those skilled in the art and can be found in references such as Trivelli and Smith, The Photographic Journal, Vol. LXXIX, May 1939, pp. 330-338, T.H. James, The Theory of The Photographic Process, 4th Edition, Chapter 3, Chimie et Physique Photographique, P. Glafkides, Paul Montel (1967), Photographic Emulsion Chemistry, G. F. Duffin, The Focal Press (1966), Making and Coating Photographic Emulsions, V. L. Zelikman, The Focal Press (1966), in US Pat. Nos. 2,222,264; 2,592,250; 3,650,757; 3,917,485; 3,790,387; 3,716,276; and 3,979,213; Research Disclosure, Sept. 1994, Item 36544 "Photographic Silver Halide Emulsions, Preparations, Addenda, Systems and Processing."
[0040] In the preparation of silver halide emulsions, commonly employed halogen compositions of the silver halide grains can be used. Typical silver halides include silver chloride, silver bromide, silver iodide, silver chloroiodide, silver bromoiodide, silver chlorobromoiodide and the like. However, silver bromide and silver bromoiodide are preferred silver halide compositions with silver bromoiodide compositions containing from 0 to 10 mol% silver iodide, preferably, from 0.2 to 5 mol% silver iodide, and more preferably, from 0.5 to 1.5 mol% silver iodide. The halogen composition of individual grains may be homogeneous or heterogeneous.
[0041] As a binder for silver halide emulsions, gelatin is preferred, but other hydrophilic colloids can be used, alone or in combination, such as, dextran, cellulose derivatives (e.g., hydroxyethylcellulose, carboxymethyl cellulose), collagen derivatives, colloidal albumin or casein, polysaccharides, synthetic hydrophilic polymers (e.g., polyvinylpyrrolidone, polyacrylamide, polyvinylalcohol, polyvinylpyrazole) and the like. Gelatin derivatives, such as, highly deionized gelatin, acetylated gelatin and phthalated gelatin can also be used. It is also common to employ the hydrophilic colloids in combination with synthetic polymeric binders and peptizers such as acrylamide and methacrylamide polymers, polymers of alkyl and sulfoalkyl acrylates and methacrylates, polyvinyl alcohol and its derivatives, polyvinyl lactams, polyamides, polyamines, polyvinyl acetates, and the like.
[0042] The grains of these silver halide emulsions may be coarse or fine, and the grain size distribution of them may be narrow or extensive. Further, the silver halide grains may be regular grains having a regular crystal structure such as cube, octahedron, and tetradecahedron, or the spherical or irregular crystal structure, or those having crystal defects such as twin planes, or those having a tabular form, or combination thereof. Furthermore, the grain structure of the silver halides may be uniform from the interior to exterior thereof, or be multilayer. In a simple embodiment, the grains may comprise a core and a shell, which may have different halide compositions and/or may have undergone different modifications such as the addition of doping agents. Besides having a differently composed core and shell, the silver halide grains may also comprise different phases in-between. Furthermore, the silver halides may be of such a type as allows a latent image to be formed mainly on the surface thereof or of such type as allows it to be formed inside the grains thereof.
[0043] In a preferred embodiment of the present invention, tabular silver halide emulsions are employed. Tabular silver halide emulsions are characterized by the average diameter:thickness ratio of silver halide grains (often referred to in the art as aspect ratio). Tabular silver halide grains have an aspect ratio of at least 2:1, preferably, 2:1 to 20:1, more preferably, 2:1 to 14:1, and most preferably, 2:1 to 8:1. Average diameters of the tabular silver halide grains range from about 0.3 to about 5 mm, preferably, from about 0.5 to about 3 mm, more preferably, from about 0.8 to about 1.5 mm. The tabular silver halide grains have a thickness of less than 0.4 mm, preferably, less than 0.3 mm, and more preferably, within 0.1 to 0.3 mm. The projected area of the tabular silver halide grains accounts for at least 50%, preferably, at least 80%, and more preferably, at least 90% of the projected area of all the silver halide grains of the emulsion.
[0044] The tabular silver halide grain dimensions and characteristics described above can be readily ascertained by procedures well known to those skilled in the art. The term "diameter" is defined as the diameter of a circle having an area equal to the projected area of the grain. The term "thickness" means the distance between two substantially parallel main planes constituting the tabular silver halide grains. From the measure of diameter and thickness of each grain the diameter:thickness ratio of each grain can be calculated, and the diameter:thickness ratios of all tabular grains can be averaged to obtain their average diameter:thickness ratio. By this definition, the average diameter:thickness ratio is the average of individual tabular grain diameter:thickness ratios. In practice, it is simpler to obtain an average diameter and an average thickness of the tabular grains and to calculate the average diameter:thickness ratio as the ratio of these two averages. Whatever the method used, the average diameter:thickness ratios obtained do not greatly differ.
[0045] Silver halide emulsions containing tabular silver halide grains can be prepared by various processes known to those of ordinary skill in the art for the preparation of photographic elements.
[0046] Preparation of silver halide emulsions containing tabular silver halide grains is described, for example, in de Cugnac and Chateau, "Evolution of the Morphology of Silver Bromide Crystals During Physical Ripening", Science and Industries Photographiques, Vol. 33, No.2 (1962), pp.121-125, in Gutoff, "Nucleation and Growth Rates During the Precipitation of Silver Halide Photographic Emulsions", Photographic Science and Engineering, Vol. 14, No. 4 (1970), pp. 248-257, in Berry et al., "Effects of Environment on the Growth of Silver Bromide Microcrystals", Vol.5, No.6 (1961), pp. 332-336, in Research Disclosure, Sept. 1994, Item 36544 "Photographic Silver Halide Emulsions, Preparations, Addenda, Systems and Processing", in US Pat. Nos. 4,063,951; 4,067,739; 4,184,878; 4,434,226; 4,414,310; 4,386,156; and 4,414,306; and in EP Pat. Appln. No. 263,508.
[0047] At the end of the silver halide grain formation, water soluble salts are removed from the emulsion by procedures known in the art. Suitable washing processes are those wherein the dispersing medium and soluble salts dissolved therein can be removed from the silver halide emulsion on a continuous basis, such as, for example, a combination of dialysis or electrodialysis for the removal of soluble salts or a combination of osmosis or reverse osmosis for the removal of the dispersing medium.
[0048] Among the known techniques for removing the dispersing medium and soluble salts while retaining silver halide grains in the remaining dispersion, ultrafiltration is a particularly advantageous washing processes for the practice of this process. Typically, an ultrafiltration unit comprising membranes of inert, non-ionic polymers is used as a washing process. Since silver halide grains are large in comparison with the dispersing medium and the soluble salts or ions, silver halide grains are retained by the membranes while the dispersing medium and the soluble salts dissolved therein are removed.
[0049] Prior to use, silver halide grain emulsions are generally fully dispersed and bulked up with gelatin or other dispersion of peptizer and subjected to any of the known methods for achieving optimum sensitivity. A wide description of methods and compounds useful in chemical and optical sensitization can be found in Research Disclosure No. 38597, September 1996, "Photographic Silver Halide Emulsions, Preparations, Addenda, Systems and Processing", Items IV and 5.
[0050] Chemical sensitization is performed by adding chemical sensitizers and other additional compounds to the silver halide emulsion, followed by the so-called chemical ripening at high temperature for a predetermined period of time. Chemical sensitization can be performed by various chemical sensitizers such as gold, sulfur, reducing agents, platinum, selenium, sulfur plus gold, and the like. Tabular silver halide grains, after grain formation and desalting, are preferably chemically sensitized by at least one gold sensitizer and at least one sulfur sensitizer. During chemical sensitization other compounds can be added to improve the photographic performances of the resulting silver halide emulsion, such as, for example, antifoggants, stabilizers, optical sensitizers, supersensitizers, and the like.
[0051] Gold sensitization is performed by adding a gold sensitizer to the emulsion and stirring the emulsion at high temperature of preferably 40°C or more for a predetermined period of time. As a gold sensitizer, any gold compound which has an oxidation number of +1 or +3 and is normally used as gold sensitizer can be used. Preferred examples of gold sensitizers are chloroauric acid, the salts thereof and gold complexes, such as those described in US 2,399,083. Specific examples of gold sensitizers include chloroauric acid, potassium chloroaurate, auric trichloride, sodium aurithiosulfate, potassium aurithiocyanate, potassium iodoaurate, tetracyanoauric acid, 2-aurosulfobenzothiazole methochloride and ammonium aurothiocyanate.
[0052] Sulfur sensitization is performed by adding a sulfur sensitizer to the silver halide emulsion and stirring the emulsion at a high temperature of 40°C or more for a predetermined period of time. Useful examples of sulfur sensitizer include thiosulfonates, thiocyanates, sulfinates, thioethers, and elemental sulfur.
[0053] The amounts of the gold sensitizer and the sulfur sensitizer change in accordance with the various conditions, such as activity of the gold and sulfur sensitizer, type and size of silver halide grains, temperature, pH and time of chemical ripening. These amounts, however, are preferably from 1 to 20 mg of gold sensitizer per mole of silver, and from 1 to 100 mg of sulfur sensitizer per mole of silver. The temperature of chemical ripening is preferably 45°C or more, and more preferably 50°C to 80°C. The pAg and pH may take arbitrary values.
[0054] During chemical sensitization, addition times and order of gold sensitizer and sulfur sensitizer are not particularly limited For example, gold and sulfur sensitizers can be added at the initial stage of chemical sensitization or at a later stage either simultaneously or at different times. Usually, gold and sulfur sensitizers are added to the silver halide emulsion by their solutions in water, in a water-miscible organic solvent, such as methanol, ethanol and acetone, or as a mixture thereof.
[0055] A stabilizer is preferably added at any time before the addition of the sulfur sensitizer. Even if the action of the stabilizer is not yet fully understood, it is believed that it acts as a digest stabilizer and a site director for the sulfur sensitizer. Preferably, the stabilizer is added before the addition of sulfur chemical sensitizer in an amount of from 1 to 500 milligrams per mole of silver, preferably, from 10 to 300 milligrams per mole of silver.
[0056] Specific examples of useful stabilizers include thiazole derivatives; benzothiazole derivatives; mercapto-substituted heterocyclic compounds(e.g., mercaptotetrazoles, mercaptotriazoles, mercaptodiazoles, mercaptopyrimidines, mercaptoazoles); azaindenes, (e.g., triazaindenes and tetrazaindenes); triazoles; tetrazoles; and sulfonic and sulfinic benzene derivatives. Azaindenes are preferably used, more preferably, tetraazaindenes.
[0057] Moreover, the silver halide grain emulsion may be optically sensitized to a desired region of the visible spectrum. The method for spectral sensitization is not particularly limited. For example, optical sensitization may be possible by using an optical sensitizer, including a cyanine dye, a merocyanine dye, complex cyanine and merocyanine dyes, oxonol dyes, hemioxonol dyes, styryl dyes and streptocyanine dyes, either alone or in combination. Useful optical sensitizers include cyanines derived from quinoline, pyridine, isoquinoline, benzindole, oxazole, thiazole, selenazole, imidazole. Particularly useful optical sensitizers are the dyes of the benzoxazole-, benzimidazole- and benzothiazole-carbocyanine type. Usually, the addition of the spectral sensitizer is performed after the completion of chemical sensitization. Alternatively, spectral sensitization can be performed concurrently with chemical sensitization, before chemical sensitization, or even prior to the completion of silver halide precipitation. When the spectral sensitization is performed before the chemical sensitization, it is believed that the preferential absorption of spectral sensitizing dyes on the crystallographic faces of the tabular grains allows chemical sensitization to occur selectively at unlike crystallographic surfaces of the tabular grains. In a preferred embodiment, the spectral sensitizers produce J aggregates, if adsorbed on the surface of the silver halide grains, and a sharp absorption band (J-band) with a bathochromic shift with respect to the absorption maximum of the free dye in aqueous solution.
[0058] It is known in the art of radiographic photographic elements that the intensity of the sharp absorption band (J-band) shown by the spectral sensitizing dye absorbed on the surface of the light-sensitive silver halide grains will vary with the quantity of the specific dye chosen as well as the size and chemical composition of the grains. The maximum intensity of J-band has been obtained with silver halide grains having the above described sizes and the chemical compositions absorbed with J-band spectral sensitizing dyes in a concentration of from 25 to 100 percent or more of monolayer coverage of the total available surface area of the silver halide grains. Optimum dye concentration levels can be chosen in the range of 0.5 to 20 millimoles per mole of silver halide, preferably, in the range of 2 to 10 millimoles.
[0059] Spectral sensitizing dyes producing J aggregates are well known in the art, as illustrated by F. M. Hamer, Cyanine Dyes and Related Compounds, John Wiley and Sons, 1964, Chapter XVII and by T. H. James, The Theory of the Photographic Process, 4th Edition, MacMillan, 1977, Chapter 8.
[0060] In a preferred form, J-band exhibiting dyes are cyanine dyes. Such dyes comprise two basic heterocyclic nuclei joined by a linkage of methine groups. The heterocyclic nuclei preferably include fused benzene rings to enhance J aggregation. The heterocyclic nuclei are preferably quinolinium, benzoxazolium, benzothiazolium, benzoselenazolium, benzimidazolium, naphthoxazolium, naphthothiazolium and naphthoselenazolium quaternary salts.
[0061] Suitable cyanine dyes, which are joined by a methine linkage, include two basic heterocyclic nuclei, such as pyrrolidine, oxazoline, thiazoline, pyrrole, oxazole, thiazole, selenazole, tetrazole and pyridine and nuclei obtained by fusing an alicyclic hydrocarbon ring or an aromatic hydrocarbon ring to each of the above nuclei, such as indolenine, benzindolenine, indole, benzoxazole, naphthoxazole, benzothiazole, naphthothiazole, benzoselenazole, benzimidazole and quinoline. These nuclei can have substituents groups.
[0062] Suitable merocyanine dyes, which are joined by a methine linkage, include a basic heterocyclic nucleus of the type described above and an acid nucleus, such as a 5- or 6-membered heterocyclic nucleus derived from barbituric acid, 2-thiobarbituric acid, rhodanine, hydantoin, 2-thiohydantoin, 4-thiohydantoin, 2-pyra-zolin-5-one, 2-isoxazolin-5-one, indan-1,3-done, cyclohexane-1-3-dione, and isoquinolin-4-one.
[0063] Preferred dyes are cyanine dyes, such as those represented by the following formula:
wherein n, m and d each independently represents 0 or 1, L represents a methine linkage, e.g., =CH-, =C(C2H5)-, etc., R1 and R2 each represents a substituted or unsubstituted alkyl group, preferably, a lower alkyl group of from 1 to 4 carbon atoms, e.g., methyl, ethyl, propyl, butyl, cyclohexyl and dodecyl, a hydroxyalkyl group, e.g., b-hydroxyethyl and W-hydroxybutyl, an alkoxyalkyl group, e.g., b-methoxyethyl and W-butoxyethyl, a carboxyalkyl group, e.g., b-carboxyethyl and W-carboxybutyl, a sulfoalkyl group, e.g., b-sulfoethyl and W-sulfobutyl, a sulfatoalkyl group, e.g., b-sulfatoethyl and W-sulfatobutyl, an acyloxyalkyl group, e.g., b-acetoxyethyl, g-acetoxypropyl and W-butyrylorybutyl, an alkoxycarbonylalkyl group, e.g., b-methoxycarbonylethyl and W-ethoxycarbonylbutyl, benzyl, phenethyl, or an aryl group of up to 30 carbon atoms, e.g., phenyl, tolyl, xylyl, chlorophenyl and naphthyl, X represents an acid anion, e.g., chloride, bromide, iodide, thiocyanate, sulfate, perchlorate, p-toluenesulfonate and methylsulfate; the methine linkage forming an intramolecular salt when p is 0; Z1 and Z2, the same or different, each represents the non-metallic atoms necessary to complete the same simple or condensed 5- or 6-membered heterocyclic nucleus, such as a benzothiazole nucleus (e.g., benzothiazole, 3-, 5-, 6- or 7-chloro-benzothiazole, 4-, 5- or 6-methylbenzothiazole, 5- or 6-bromobenzothiazole, 4- or 5-phenyl-benzothiazole, 4-, 5- or 6-methoxybenzothiazole, 5,6-dimethyl-benzothiazole and 5- or 6-hydroxy-benzothiazole), a naphthothiazole nucleus (e.g., a-naphthothiazole, b-naphthothiazole, 5-methoxy-b-naphthothiazole, 5-ethoxy-a-naphthothiazole and 8-methoxy-a-naph-thothiazole), a benzoselenazole nucleus (e.g., benzoselenazole, 5-chloro-benzoselenazole and tetrahydrobenzoselenazole), a naphthoselenazole nucleus (e.g., a-naphtho-selenazole and b-naphthoselenazole), a benzoxazole nucleus (e.g., benzoxazole, 5- or 6-hydroxy-benzoxazole, 5-chloro-benzoxazole, 5- or 6-methoxy-benzoxazole, 5-phenyl-benzoxazole and 5,6-dimethyl-benzoxazole), a naphthoxazole nucleus (e.g., a-naphthoxazole and b-naphthoxazole), a 2-quinoline nucleus (e.g., 2-quinoline, 6-, 7, or 8-methyl-2-quinoline, 4-, 6- or 8-chloro-2-quinoline, 5-, 6-or 7-ethoxy-2-quinoline and 6- or 7-hydroxy-2-quinoline), a 4-quinoline nucleus (e.g., 4-quinoline, 7- or 8-methyl-4-quinoline and 6-methoxy-4-quinoline), a benzimidazole nucleus (e.g., benzimidazole, 5-chloro-benzimidazole and 5,6-dichloro-benzimidazole), a thiazole nucleus (e.g., 4- or 5-methyl-thiazole, 5-phenyl-thiazole and 4,5-di-methyl-thiazole), an oxazole nucleus (e.g., 4- or 5-methyl-oxazole, 4-phenyl-oxazole, 4-ethyl-oxazole and 4,5-dimethyl-oxazole), and a selenazole nucleus (e.g., 4-methyl-selenazole and 4-phenyl-selenazole. More preferred dyes within the above class are those having an internal salt group and/or derived from benzoxazole and benzimidazole nuclei as indicated before. Typical methine spectral sensitizing dyes include those listed below.
[0064] The methine spectral sensitizing dyes are generally known in the art. Particular reference can be made to US Pat. Nos. 2,503,776; 2,912,329; 3,148,187; 3,397,060; 3,573,916; and 3,822,136 and FR Pat. No. 1,118,778. Also their use in photographic emulsions is very well known wherein they are used in optimum concentrations corresponding to desired values of sensitivity to fog ratios. Optimum or near optimum concentrations of spectral sensitizing dyes generally go from 10 to 500 mg per mole of silver, preferably, from 50 to 200, and more preferably, from 50 to 100.
[0065] Spectral sensitizing dyes can be used in combinations which result in supersensitization, i.e., spectral sensitization which is greater in a spectral region than that from any concentration of one dye alone or which would result from an additive effect of the dyes. Supersensitization can be obtained with selected combinations of spectral sensitizing dyes and other addenda, such as stabilizers and antifoggants, development accelerators and inhibitors, optical brighteners, surfactants and antistatic agents, as described by Gilman, Photographic Science and Engineering, 18, pp. 418-430, 1974 and in US Pat. Nos. 2,933,390; 3,635,721; 3,743,510; 3,615,613; 3,615,641; 3,617,295; and 3,635,721.
[0066] Other additives can be added to the silver halide emulsion before or during coating, such as, stabilizers or antifoggants (i.e., azaindenes, triazoles, tetrazoles, imidazolium salts, polyhydroxy compounds and others); developing promoters (e.g., benzyl alcohol, polyoxyethylene type compounds, etc.); image stabilizers (i.e., compounds of the chromane, cumaran, bisphenol type, etc.); and lubricants (i.e., wax, higher fatty acids glycerides, higher alcohol esters of higher fatty acids, etc.). Also, coating aids, modifiers of the permeability in the processing liquids, defoaming agents, antistatic agents and matting agents may be used. Other useful additives are disclosed in Research Disclosure, Item 17643, December 1978 in Research Disclosure, Item 18431, August 1979, in Research Disclosure, Item 308119, Section IV, December 1989, and in Research Disclosure Item 36544, September 1994.
[0067] Suitable supports include glass, paper, polyethylene-coated paper, metals, polymeric film such as cellulose nitrate, cellulose acetate, polystyrene, polyethylene terephthalate, polyethylene, polypropylene and the like.
[0068] Preferred light-sensitive silver halide photographic elements are radiographic light-sensitive elements employed in X-ray imaging comprising a silver halide emulsion layer(s) coated on both surfaces of a support, preferably, a polyethylene terephthalate support. The silver halide emulsions are preferably coated on the support at a silver coverage in the range of 1.5 to 3 g/m2 per side. Usually, the radiographic light-sensitive elements are associated with intensifying screens so as to be exposed to radiation emitted by the screens. The screens are made of relatively thick phosphor layers which transform the X-rays into more imaging-effective radiation such as light (e.g., visible light). The screens absorb a larger portion of X-rays than the light-sensitive elements do and are used to reduce the X-ray dose necessary to obtain a useful image. Intensifying screens absorbing more than 25% of the total X-radiation are preferably used. Depending on their chemical composition, the phosphors can emit radiation in the ultraviolet, blue, green or red region of the visible spectrum and the silver halide emulsions are sensitized to the wavelength region of the radiation emitted by the screens. Sensitization is performed by using spectral sensitizing dyes absorbed on the surface of the silver halide grains as described above.
[0069] Other layers and additives, such as subbing layers, surfactants, filter dyes, intermediate layers, protective layers, anti-halation layers, barrier layers, dye underlayers, development inhibiting compounds, speed-increasing agents, stabilizers, plasticizers, chemical sensitizers, UV absorbers and the like can be present in the radiographic element. Dye underlayers are particularly useful to reduce the crossover of the double coated silver halide radiographic element. Reference to well-known dye underlayer can be found in US Pat. Nos. 4,900,652; 4,855,221; 4,857,446; and 4,803,150. In a preferred embodiment, a dye underlayer is coated on at least one side of the support, more preferably, on both sides of the support, before the coating of at least two silver halide emulsion.
[0070] The silver halide radiographic elements are preferably fore-hardened. Typical examples of organic or inorganic hardeners include chrome salts (e.g., chrome alum, chromium acetate), aldehydes (e.g., formaldehyde and glutaraldehyde), isocyanate compounds (hexamethylene diisocyanate), active halogen compounds (e.g., 2,4-dichloro-6-hydroxy-s-triazine), epoxy compounds (e.g., tetramethylene glycol diglycidylether), N-methylol derivatives (e.g., dimethylolurea, methyloldimethyl hydantoin), aziridines, mucohalogeno acids (e.g., mucochloric acid), active vinyl derivatives (e.g., vinylsulfonyl and hydroxy-substituted vinylsulfonyl derivatives) and the like. Other references to well known hardeners can be found in Research Disclosure, December 1989, Vol. 308, Item 308119, Section X, and Research Disclosure, September 1994, Vol. 365, Item 36544, Section II(b).
[0071] A detailed description of photographic elements and of various layers and additives can be found in Research Disclosure 17643 December 1978, Research Disclosure 18431 August 1979, Research Disclosure 18716 November 1979, Research Disclosure 22534 January 1983, Research Disclosure 308119 December 1989, and Research Disclosure 36544, September, 1994.
[0072] The silver halide photographic element can be exposed and processed by any conventional processing technique. Any known developing agent can be added into the developer, such asdihydroxybenzenes (e.g., hydroquinone), pyrazolidones (1-phenyl-3-pyrazolidone or 4,4-dimethyl-1-phenyl-3-pyrazolidone), and aminophenols (e.g., N-methyl-p-aminophenol), alone or in combinations thereof. Preferably, the silver halide photographic elements are developed in a developer comprising dihydroxybenzenes as the main developing agent, and pyrazolidones and p-aminophenols as auxiliary developing agents.
[0073] Other well known additives can be present in the developer, such as, for example, antifoggants (e.g., benzotriazoles, indazoles, tetrazoles), silver halide solvents (e.g., thiosulfates, thiocyanates), sequestering agents (e.g., amino-polycarboxylic acids, aminopolyphosphonic acids), sulfite antioxidants, buffers, restrainers, hardeners, contrast promoting agents, surfactants, and the like. Inorganic alkaline agents, such as KOH, NaOH, and LiOH are added to the developer composition to obtain the desired pH which is usually higher than 10.
[0074] The silver halide photographic element can be processed with a fixer of a typical composition for the application required. The fixing agents include thiosulfates, thiocyanates, sulfites, ammonium salts, and the like. The fixer composition can comprise other well known additives, such asacid compounds (e.g., metabisulfates), buffers (e.g., carbonic acid, acetic acid), hardeners (e.g., aluminum salts), tone improving agents, and the like.
[0075] The exposed radiographic elements can be processed by any of the conventional processing techniques. Such processing techniques are illustrated for example in Research Disclosure, Item 17643, cited above, and Research Disclosure 36544 September 1994. Roller transport processing is particularly preferred, as illustrated in US Pat. Nos. 3,025,779; 3,515,556; 3,545,971; and 3,647,459 and in UK Patent 1,269,268. Hardening development can be undertaken, as illustrated in US Patent 3,232,761.
[0076] With regard to the processes for the silver halide emulsion preparation and the use of particular ingredients in the emulsion and in the light-sensitive element, reference is made to Research Disclosure, September 1996, Item 38957, and particularly to the following chapters:
I. Emulsion grains and their preparation.
II. Vehicles, vehicle extenders, vehicle-like addenda and vehicle related addenda.
III. Emulsion washing.
IV. Chemical sensitization
V. Spectral sensitization and desensitization
VI. UV dyes/optical brighteners/luminescent dyes
VII. Antifoggants and stabilizers
VIII. Absorbing and scattering materials.
IX. Coating physical property modifying addenda.
X. Dye image formers and modifiers.
XI. Layers and layer arrangements
XV. Supports
[0077] The present invention will be now described in greater detail with reference to the following but not limiting examples. All the amounts referred to in the following examples are relative to one mole of silver in the resulting silver halide emulsion, unless differently specified.
EXAMPLE 1
Sample 1 (reference )
[0078] A silver bromoiodide emulsion with an average grain equivalent diameter of 1.25 micron, an average grain thickness of 0.18 micron, a COV of 37 % and 0.9 percent iodide in mole respect to the total halide ions was prepared by double jet method was employed for all examples 1 through 14.
[0079] The emulsion was chemically and spectrally sensitized using sulfur, gold, mercury and palladium sensitizers plus a triethyl ammonium salt of 5,5'-dichloro-9-ethyl-3,3'-di-(3-sulfopropyl) oxacarbocyanine as spectral sensitization dye. The digest was performed for about 120 to 130 minutes at 60° and stabilized successively with 200 mg of potassium iodide and 1366 mg of 5-methyl-7-hydroxy-2-3-4-triazoindolizine (4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene) before chilling and kept in cold storage until needed for coating.
[0080] The sensitized silver halide emulsion was melted at 45°C and subjected to coating finals. As coating auxiliaries were added 1293 mg of calcium nitrate, 80 mg of azodicarboxylic dimorpholide, 18338 mg of polyethylacrylate (in dispersion at 20% in water plus 367 mg of lauryl sulfate), 66738 mg of dextran as gel extender, 267 mg of colanyl blue as chromatic corrector. The pH was corrected to 6.3 before adding 3774 mg of SSMA copolymer (copolymer of styrene sulfonic acid and maleic anhydride).
[0081] The resulting silver halide emulsion was immediately coated on the two faces of blue 7 mil polyester base with a conventional antistatic top-coat containing hardening agents. The coating speed was 8.3 meters per minute and the covering weight was around 2.25 g of silver per m2 per side.
[0082] The resulting film sample was subjected to different test to evaluate its resistance to iron contamination and its resistance to ageing.
[0083] A first portion of the fresh film sample was kept 3 days at 38°C before being subjected to iron (III) contamination. This was done by applying on one side and at the rate of 23 ml per square meter a solution containing 0.2% by weight ferric sulfate Fe2(SO4)3 as iron source, 1% standard DGF Gel as coating auxiliary, 0.12% Triton X-100 as surfactant, 1% citric acid as chelating agent and sodium carbonate Na2CO3 for pH 6.3. This solution is coated on half surface of a 10 by 28 cm sheet with a Mayer bar number ten. This method allows to ensure that a determined level of contaminant is present and to make discernible the compounds that are capable of removing defects caused by the contaminant.
[0084] The contaminated film was dried and exposed to white light with a standard bromograph for 3/10 of second with filter number 2.
[0085] The exposed films were processed through a 90 seconds dry to dry medical X-ray automatic processor type XP-515 (manufactured by Imation Corp., MN, USA) with standard chemistry (XAD 3 developer and XAF 3 fixer, both manufactured by Imation Corp., MN, USA).
[0086] The optical densities were measured on both the non-contaminated and the contaminated areas and the desensitizing effect of iron (III) is determined using the following formula:
wherein D1 represents the average value of 10 density measurements on the contaminated area of the material and D2 represents the average value of 10 density measurements on the non-contaminated area of the same sheet.
[0087] The value of ΔD % is negative if there is a desensitization effect, positive if there is a sensitization effect of the contaminant, and is proportional to the resulting effect of iron contamination on the final material which has not antispot protection. The results are reported in the following Table 1.
[0088] A second and third portion of the fresh film sample were kept 3 days at 38°C and 10 days at 50°C, respectively, without any metallic contamination before being subjected to X-ray exposure using an X-ray tube at 75 kV and 300 mA for 0.06 second with a pair of Trimax™ T8 type screens.
[0089] The exposed films were processed through a 90 seconds dry to dry medical X-ray automatic processor type XP-515 (manufactured by Imation Corp., MN, USA) with standard chemistry (XAD 3 developer and XAF 3 fixer, both manufactured by Imation Corp., MN, USA). The sensitometric results are reported in Table 1.
Sample 2 (control)
[0090] The procedure of sample 1 is repeated, except that during addition of coating finals, 6.24 milimole of compound 1 (2,5-dihydroxy-1 ,4-benzenedisulfonic acid dipotassium salt - HQDS, corresponding to exemplified compound A-9) is added per one mole of silver, corresponding to 90 mg of compound per square meter of coated film. The iron contamination process is carried out in the same manner on the half sheet to determine the protection effect of compound 1. The results are reported in the following Table 1.
Sample 3 (Comparison)
[0091] The procedure of sample 1 is repeated, except that during addition of coating finals, 5.3 milimole of D.T.P.A. (Diethylenetriamine-pentaacetic acid, corresponding to exemplified compound P-6) were added for one mole of silver. The results are reported in Table 1.
Sample 4 (Comparison)
[0092] The procedure of sample 1 is repeated, except that during addition of coating finals, 10.86 milimole of D.T.P.A. is added for one mole of silver. The results are reported in Table 1.
Sample 5 (Comparison)
[0093] The procedure of sample 1 is repeated, except that during addition of coating finals, 21.71 milimole of D.T.P.A. is added for one mole of silver. The results are reported in Table 1.
Sample 6 (Comparison)
[0094] The procedure of sample 1 is repeated, except that during addition of coating finals, 5.28 milimole of D.C.T.A. (1,2-Diaminocyclohexane-N,N,N',N'-tetraacetic acid, corresponding to exemplified compound P-7) is added for one mole of silver. The results are reported in Table 1.
Sample 7 (Comparison)
[0095] The procedure of sample 1 is repeated, except that during addition of coating finals, 10.8 milimole of D.C.T.A. is added for one mole of silver. The results are reported in Table 1.
Sample 8 (Comparison)
[0096] The procedure of sample 1 is repeated, except that during addition of coating finals, 21.72 milimole of D.C.T.A. is added for one mole of silver. The results are reported in Table 1.
Sample 9 (Comparison)
[0097] The procedure of sample 1 is repeated, except that during addition of coating finals, 5.29 milimole of T.D.T.A. (Trimethylenediamine-N,N,N',N'-tetraacetic acid, corresponding to exemplified compound P-2) is added for one mole of silver. The results are reported in Table 1.
Sample 10 (Comparison)
[0098] The procedure of sample 1 is repeated, except that during addition of coating finals, 10.85 milimole of T.D.T.A. is added for one mole of silver. The results are reported in Table 1.
Sample 11 (Comparison)
[0099] The procedure of sample 1 is repeated, except that during addition of coating finals, 21.69 milimole of T.D.T.A. is added for one mole of silver. The results are reported in Table 1.
Sample 12 (Invention)
[0100] The procedure of sample 1 is repeated, except that during addition of coating finals, 6.24 milimole of hydroquinone disulfonic acid potassium salt (2,5-di-hydroxy-1,4-benzenedisulfonic acid dipotassium salt) and 21.71 milimole of D.T.P.A. are added for one mole of silver. The results are reported in Table 1.
Sample 13 (Invention)
[0101] The procedure of sample 1 is repeated, except that during addition of coating finals, 6.24 milimole of hydroquinone disulfonic acid potassium salt (2,5-di-hydroxy-1 ,4-benzenedisulfonic acid dipotassium salt) and 21.72 milimole of D.C.T.A. are added for one mole of silver. The results are reported in Table 1.
Sample 14 (Invention)
[0102] The procedure of sample 1 is repeated, except that during addition of coating finals, 6.24 milimole of hydroquinone disulfonic acid potassium salt (2,5-dihydroxy-1,4-benzenedisulfonic acid dipotassium salt) and 21.69 milimole of T.D.T.A. are added for one mole of silver. The results are reported in Table 1.
TABLE 1
| Sample | Compound | mmol/m2/side | Δ OD% | 3 Days 38°C Incubation | 10 Days 50°C Incubation | ||||
| Speed | Dmin | Sp/Dmin | Speed | Dmin | Sp/Dmin | ||||
| 1 (C) | - | - | -13.4 | 100 | 0.22 | 455 | 100 | 0.22 | 455 |
| 2 (C) | HQDS | 0.13 | -7.4 | 110 | 0.21 | 524 | 110 | 0.21 | 524 |
| 3 (C) | DTPA | 0.11 | -5.7 | 105 | 0.22 | 476 | 107 | 0.22 | 485 |
| 4 (C) | DTPA | 0.23 | -5.6 | 117 | 0.22 | 530 | 127 | 0.23 | 563 |
| 5 (C) | DTPA | 0.45 | -4.8 | 128 | 0.22 | 583 | 157 | 0.25 | 626 |
| 6 (C) | DCTA | 0.11 | -4.5 | 108 | 0.22 | 490 | 113 | 0.22 | 515 |
| 7 (C) | DCTA | 0.22 | -4.3 | 108 | 0.22 | 491 | 120 | 0.22 | 545 |
| 8 (C) | DCTA | 0.45 | -3.7 | 117 | 0.22 | 532 | 157 | 0.23 | 681 |
| 9 (C) | TDTA | 0.11 | -5.8 | 102 | 0.22 | 465 | 113 | 0.22 | 515 |
| 10 (C) | TDTA | 0.23 | -3.6 | 105 | 0.22 | 476 | 120 | 0.23 | 533 |
| 11 (C) | TDTA | 0.45 | -3.8 | 110 | 0.22 | 500 | 130 | 0.23 | 565 |
| 12 (I) | DTPA + HQDS | 0.45 + 0.13 | -4.5 | 119 | 0.22 | 541 | 167 | 0.22 | 740 |
| 13 (I) | DCTA + HQDS | 0.45 + 0.13 | -3.7 | 107 | 0.21 | 510 | 147 | 0.22 | 666 |
| 14 (I) | TDTA + HQDS | 0.45 + 0.13 | -4.0 | 113 | 0.22 | 515 | 127 | 0.22 | 575 |
[0103] The example number 1, taken as control, shows the desensitizing effect of 0.12 milimole per square meter of iron (III) on our system. All speed values are measured 0.1 LogE above Dmin and the sensitivity of the control is taken as 100.
[0104] The results of Sample 2 show that HQDS, an aryl compounds as described in European Patent Application No. 97-116342.3, was able to reduce the negative effect of iron (III) present in the film and to increase the speed to Dmin ratio also after accelerated ageing.
[0105] The results examples 3 to 11 clearly show that the polyamine-polycarboxyl derivatives were able to reduce the negative effect of iron (III) present in the film but that these compounds promoted a proportional increase of speed and Dmin so that the Dmin values reached unacceptable levels in particular after accelerated ageing.
[0106] The results of samples 12 to 14 clearly showed that the association of a polyamine-polycarboxyl derivative with an aryl compound like HQDS strongly increased the sensitivity of the final material without increasing the Dmin, even in stressed incubation situation. The example 12 showed 0.2 LogE sensitivity increase with the same Dmin. The association between a polyamine-polycarboxyl derivative and an aryl compound like H.Q.D.S clearly led to a synergic effect.
[0107] Accordingly, the photographic elements of the present invention comprising a silver halide emulsion containing in association a polyamine-polycarboxyl derivative and an aryl compound were preserved from spot defects due to metallic contamination and at the same time showed an improved speed to Dmin ratio.
1. A process for the manufacturing of a silver halide photographic element comprising
the steps of:
(i) preparing a silver halide emulsion,
(ii) sensitizing said silver halide emulsion by means of a chemical and optical sensitization method, and
(iii) coating said silver halide emulsion onto a support,
wherein said process is characterized in that said process further comprises the step
of adding to said silver halide emulsion a polyamine-polycarboxyl derivative and an
aryl compound having at least two hydroxyl groups and at least one additional substituent
represented by a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl
group.
2. The process according to claim 1, wherein said aryl compound is represented by the
following formula:
wherein R is a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group and n is an integer of from 1 to 4.
wherein R is a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group and n is an integer of from 1 to 4.
3. The process according to claim 1, wherein said polyamine-polycarboxyl derivative is
represented by the following formula:
wherein Z is a divalent organic linking group, R1 and R2, equal or different, can be a hydrogen atom, an aryl group or a -(CH2)p-COOH group, and n, m, and p, equal or different, are an integer from 1 to 3.
wherein Z is a divalent organic linking group, R1 and R2, equal or different, can be a hydrogen atom, an aryl group or a -(CH2)p-COOH group, and n, m, and p, equal or different, are an integer from 1 to 3.
4. The process according to claim 1, wherein said aryl compound and said polyamine-polycarboxyl
derivative are added in an amount lower than 30 millimoles per mole of silver.
5. The process according to claim 1, wherein said aryl compound and said polyamine-polycarboxyl
derivative are added in an amount lower than 6 millimoles per square meter per side
of said silver halide photographic element.
6. A silver halide photographic element comprising at least one silver halide emulsion
layer coated on a support base, wherein said silver halide emulsion layer comprises
a combination of a polyamine-polycarboxyl derivative and an aryl compound having at
least two hydroxyl groups and at least one additional substituent represented by a
sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group.
7. The photographic element according to claim 6, wherein said aryl compound is represented
by the following formula:
wherein R is a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group and n is an integer of from 1 to 4.
wherein R is a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group and n is an integer of from 1 to 4.
8. The photographic element according to claim 6, wherein said polyaminepolycarboxyl
derivative is represented by the following formula:
wherein Z is a divalent organic linking group, R1 and R2, equal or different, can be a hydrogen atom, an aryl group or a -(CH2)p-COOH group, and n, m, and p, equal or different, are an integer from 1 to 3.
wherein Z is a divalent organic linking group, R1 and R2, equal or different, can be a hydrogen atom, an aryl group or a -(CH2)p-COOH group, and n, m, and p, equal or different, are an integer from 1 to 3.
9. The photographic element according to claim 6, wherein said aryl compound and said
polyamine-polycarboxyl derivative are present in an amount lower than 30 millimoles
per mole of silver.
10. The photographic element according to claim 6, wherein said aryl compound and said
polyamine-polycarboxyl derivative are present in an amount lower than 6 millimoles
per square meter per side of said silver halide photographic element.
11. The use of a combination of a polyamine-polycarboxyl derivative and an aryl compound
having at least two hydroxyl groups and at least one additional substituent represented
by a sulfonic group, an hydroxyl group, a carboxy group or an hydroxymethyl group
to preserve from spot defects due to metallic compounds a silver halide photographic
emulsion and to increase the speed to Dmin ratio thereof.