Silver halide photographic material provided with antistatic coating

Abstract

 A silver halide photographic material having at least a light-sensitive emulsion layer and an antistatic containing (1) a water-soluble conductive polymer, (2) hydrophobic polymer particles and (3) a curing agent on a plastic film support, wherein said hydrophobic polymer particles contain an acrylamide group or contain styrene and an alkyl acrylate and/or an alkyl methacryate that have 1 - 12 carbon atoms, and form a stable dispersion with the aid of a nonionic surfactant having 3 or more alkylene oxide chains.

Description

BACKGROUND OF THE INVENTION

[0001] This invention relates to a silver halide photographic material having an antistatic coating on a plastic film support. More particularly, this invention relates to a silver halide photographic material having improved antistatic quality.

[0002] Plastic film supports generally have a great tendency to experience static buildup, which in many cases have put various limitations on the use of these supports. To take silver halide photographic materials as an example, plastic film supports such as polyethylene terephthalate films are commonly used but they often experience static buildup, particularly at low temperatures in the winter season. Provisions against this static buildup problem bear particular importance to recent practices in the photographic industry including high-speed coating of high-­sensitivity photographic emulsions and exposure of high-­sensitivity photographic materials in automatic printers.

[0003] When static charge builds up on photographic materials, occasional discharging produces static marks or foreign matters such as dust particles are electro­statically deposited to produce surface defects such as pinholes which cause substantial deterioration of the quality of photographic materials. Correcting these defects results in considerable decrease in the operational efficiency. Under these circumstances, antistatic agents are customarily used in photographic materials and recently employed antistatic agents include fluorine-containing surfactants, cationic surfactants, amphoteric surfactants, surfactants or high-molecular weight compounds containing polyethylene oxide groups, and polymers having sulfonic acid or phosphoric acid groups in the molecule.

[0004] A practice that has recently gained increasing popularity in the art is to adjust triboelectric series with fluorine-containing surfactants or to provide improved conductivity by means of conductive polymers. For example, Unexamined Published Japanese Patent Application Nos. 91165/1974 and 121523/1974 disclose the application of ionic polymers having a dissociative group in the backbone chain of the polymer.

[0005] These prior art techniques, however, have the problem that their antistatic capability is markedly reduced by development and subsequent processing. This may be because the capability of antistatic agents is lost as they pass through a development step using alkalies, a fixing step under acidic conditions, and subsequent steps including washing. Hence, if processed films such as printing light-­sensitive materials are subjected to a printing process, serious surface defects such as pinholes will occur on account of electrostatic deposition of dust particles. In order to deal with this problem, Unexamined Published Japanese Patent Application Nos. 84658/1980 and 174542/1986 have proposed an antistatic coating that is composed of a water-soluble conductive polymer having a carboxyl group, a hydrophobic polymer having a carboxyl group, and a polyfunctional aziridine. This approach insures that the capability of the antistatic coating is retained after photographic processing but it is still unsatisfactory in terms of transparency.

[0006] It has also been found that when supercontrasty emulsions containing tetrazolium or hydrazine compounds are applied to plastic film supports having this antistatic coating, the sensitivity of the emulsions decrease with time during storage.

SUMMARY OF THE INVENTION

[0007] It is, therefore, an object of the present invention to provide a silver halide photographic material having a highly transparent and haze-free antistatic coating.

[0008] Another object of the present invention is to provide a highly stable silver halide photographic material that exhibits high antistatic capability and which yet will not undergo desensitization with time even if a tetrazolium or hydrazine compound is used.

[0009] These objects of the present invention can be attained by a silver halide photographic material having at least a light-sensitive emulsion layer and an antistatic coating containing (1) a water soluble conductive polymer, (2) hydrophobic polymer particles and (3) a curing agent on a plastic film support, which hydrophobic polymer particles contain an acrylamide group or contain styrene and an alkyl acrylate and/or an alkyl methacrylate that have 1 - 12 carbon atoms, and form a stable dispersion with the aid of a nonionic surfactant having 3 or more alkylene oxide chains.

[0010] The light-sensitive emulsion layer in this photographic material desirably contains a tetrazolium or hydrazine compound.

DETAILED DESCRIPTION OF THE INVENTION

[0011] The water-soluble conductive polymer used in the present invention is capable of forming a transparent layer even if it is used alone but the resulting layer can readily crack if the drying conditions vary even by the slightest degree. In accordance with the present invention, this problem is effectively prevented by incorporating hydrophobic polymer particles.

[0012] The water-soluble conductive polymer for use in the present invention may be a polymer having at least one conductive group selected from the group consisting of a sulfonic acid group, a sulfate ester group, a quaternary ammonium salt group, a tertiary ammonium salt group, a carboxyl group and a polyethylene oxide group. Among these groups, a sulfonic acid group, a sulfate ester group and a quaternary ammonium salt group are preferred. These conductive groups must be present in an amount of at least 5 wt% per molecule of the polymer. The water-soluble conductive polymer may also contain a carboxyl group, a hydroxyl group, an amino group, an epoxy group, an aziridine group, an active methylene group, a sulfinic acid group, an aldehyde group or a vinylsulfone group. Among these groups, a carboxyl group, a hydroxyl group, an amino group, an epoxy group, an aziridine group and an aldehyde group are preferred. These groups are preferably contained in an amount of at least 5 wt% per molecule of the polymer. The water-soluble conductive polymer generally has a molecular weight in the range of 3,000 - 100,000, with the range of 3,500 - 50,000 being preferred.

[0013] The water-soluble conductive polymer that can be used in the present invention may be exemplified by, but not limited to, the following compounds.

[0014] In the above formulas (1) - (50), x, y, z and w each represents the mol% of the relevant monomer component, and M represents the average molecular weight (the term "average molecular weight" as used herein means the number average molecular weight).

[0015] The polymers enumerated above can be synthesized by polymerizing monomers that are either commercially available or obtainable in the usual manner. These compounds are added in amounts that generally range from 0.01 to 10 g/m², preferably form 0.1 to 5 g/m².

[0016] The hydrophobic polymer particles to be incorporated in the water-soluble conductive polymer layer used in the present invention are contained in the form of a "latex" that is substantially insoluble in water. The hydrophobic polymer contains an acrylamide group or contains styrene and an alkyl acrylate and/or an alkyl methacrylate that have 1 - 12 carbon atoms.

[0017] Hydrophobic polymers containing an acrylamide group are obtained by polymerizing monomers selected from among any desired combinations of acrylamide and methacrylamide derivatives. Preferably, an acrylamide derivative and/or a methacrylamide derivative is contained in an amount of at least 0.1 mol%, with the content of at least 1 mol% being particularly preferred.

[0018] Hydrophobic polymers that are composed of styrene and an alkyl acrylate and/or an alkyl methacrylate having 1 - 12 carbon atoms are obtained by polymerizing monomers selected from among any desired combinations of styrene, styrene derivatives, alkyl acrylates and alkyl methacrylates. Preferably, a styrene derivative, an alkyl acrylate or an alkyl methacrylate is contained in an amount of at least 10 mol%, with the content of at least 30 mol% being particularly preferred.

[0019] Latices of these hydrophobic polymers can be formed by either one of the following two methods: i) emulsion polymerization and ii) dissolving a solid polymer in a low-­boiling solvent, forming a fine dispersion of the polymer particles, and then distilling off the solvent. Emulsion polymerization is preferred since it is capable of producing a latex of fine polymer particle of a uniform size.

[0020] Nonionic surfactants are preferably used in emulsion polymerization and, in the present invention, nonionic surfactants having 3 or more alkylene oxide chains to be described below are used. These nonionic surfactants are used in amounts of no more than 10 wt% of the monomers. The excessive use of surfactants will make the conductive layer cloudy and hence should be avoided.

[0021] Molecular weights of at least 3,000 will suffice for the hydrophobic polymer and the transparency of the conductive layer will be little affected by the difference in the molecular weight of the hydrophobic polymer if it is no less than 3,000.

[0022] In the present invention, the hydrophobic polymer particles are preferably used in an amount of 0.1 to 10 g/m², more preferably from 0.3 to 5 g/m².

[0023] Specific examples of the hydrophobic polymer that can be used in the present invention are listed below.

[0024] In the present invention, the antistatic coating is formed on a transparent support. All photographic transparent supports may be used but preferred examples are polyethylene terephthalate and cellulose triacetate films that are adapted to transmit at least 90% of visible light. These transparent supports can be prepared by methods that are well known to one skilled in the art. If desired, they may be blued by adding dyes in small amounts that will not substantially impair light transmission.

[0025] The supports to be used in the present invention may coated with a subbing layer containing a latex polymer after corona discharge treatment. Corona discharge treatment is preferably performed to provide an energy of 1 mW - 1 kW/m² per minute. In a particularly preferred case, supports coated with a latex-containing subbing layer may be subjected to another corona discharge treatment before an antistatic coating is applied.

[0026] A polyfunctional aziridine is preferably used as a curing agent to cure the antistatic coating provided in accordance with the present invention. Particularly preferred are bifunctional or trifunctional aziridines that have molecular weights of no more than 600. In the present invention, the curing agent is preferably used in an amount of 0.01 to 10 g/m², with the range of 0.05 to 5 g/m² being particularly preferred.

[0027] The antistatic coating may be positioned closer to the support than a light-sensitive layer, or it may be provided on the back side of the support which is opposite the light-sensitive layer.

[0028] A nonionic surfactant is used as a dispersant in the present invention and a polyalkylene oxide compound is a preferred nonionic surfactant.

[0029] The polyalkylene oxide compound to be used in the present invention is a compound that contains at least 3, preferably no more than 500, polyalkylene oxide chains in the molecule. Such compounds can be synthesized either by condensation reaction between polyalkylene oxides and compounds having active hydrogen atoms such as aliphatic alcohols, phenols, aliphatic acids, aliphatic mercaptans or organic amines, or by condensing polyols such as polypropylene glycol or polyoxytetramethylene polymers with aliphatic mercaptans, organic amines, ethylene oxide or propylene oxide.

[0030] Each of the polyalkylene oxide chains in the molecule of the polyalkylene oxide compound may be divided into two or more segments to form a block copolymer. In this case, the polyalkylene oxide has a total degree of polymerization in the range of 3 - 100.

[0031] In the present invention, the nonionic surfactant is preferably used in an amount ranging from 0.0001 to 0.1 g/m², with the range of 0.0005 to 0.05 g/m² being more preferred.

[0032] Specific examples of the polyalkylene oxide that may be used in the present invention are enumerated below.

Illustrative compounds

[0033] ( Ao - 1 ) HO(CH₂CH₂O)nH (n=4)
( Ao - 2 ) HO(CH₂CH₂O)nH (n=35)
( Ao - 3 ) HO(CH₂CH₂O)nH (n=135)
( Ao - 4 ) HO(CH₂CH₂O)nH (n=225)
( Ao - 5 ) HO(CH₂CH₂O)nH (n=450)
( Ao - 6 ) n-C₄H₉O(CH₂CH₂O)_ℓH (ℓ=20)
( Ao - 7 ) n-C₈H₁₇O(CH₂CH₂O)_ℓH (ℓ=30)
( Ao - 8 ) n-C₁₂H₂₅O(CH₂CH₂O)_ℓH (ℓ=30)


( Ao - 10) n-C₁₂H₂₅S(CH₂CH₂O)_ℓH (ℓ=30)
( Ao - 11) C₄H₉S(CH₂CH₂O)nCOCH₂CH₂COOH (n=50)

[0034] The hydrazine compound to be used in the present invention is preferably represented by the following general formula (H):

where R₁ is a monovalent organic residue; R₂ is a hydrogen atom or a monovalent organic residue; Q₁ and Q₂ are each a hydrogen atom, an optionally substituted alkylsulfonyl group, or an optionally substituted arylsulfonyl group; X₁ is an oxygen atom or a sulfur atom.

[0035] Among the compounds represented by the general formula (H), one in which X₁ is an oxygen atom and R₂ is a hydrogen atom is particularly preferred.

[0036] Monovalent organic groups represented by R₁ and R₂ include aromatic residues, heterocyclic residues and aliphatic residues.

[0037] Illustrative aromatic residues include a phenyl group and a naphthyl group, which may have such substituents as alkyl, alkoxy, acylhydrazinol dialkylamino, alkoxycarbonyl, cyano, carboxy, nitro, alkylthio, hydroxy, sulfonyl, carbamoyl, halogen, acylamino, sulfonamido, urea and thiourea. Substituted phenyl groups include 4-methyl­phenyl, 4-ethylphenyl, 4-oxyethylphenyl, 4-dodecylphenyl, 4-carboxyphenyl, 4-diethylaminophenyl, 4-octylaminophenyl, 4-benzylaminophenyl, 4-acetamido-2-methylphenyl, 4-(3-­ethylthioureido_phenyl, 4-[2-(2,4-di-tert-butyl­phenoxy)butylamido]phenyl and 4-[2-(2,4-di-tert-butyl­phenoxy) butylamido]phenyl.

[0038] Illustrative heterocyclic residues are 5- or 6-­membered single or fused rings having at least one of oxygen, nitrogen, sulfur and selenium atoms. These rings may have substituents. Specific examples of heterocyclic residues include: pyrroline, pyridine, quinoline, indole, oxazole, benzoxazole, naphthoxazole, imidazole, benzimidazole, thiazoline, thiazole, benzothiazole, naphthothiazole, selenazole, benzoselenazole and naphthoselenazole rings.

[0039] These hetero rings may be substituted by alkyl groups having 1 - 4 carbon atoms such as methyl and ethyl, alkoxy groups having 1 - 4 carbon atoms such as methoxy and ethoxy, aryl groups having 6 - 18 carbon atoms such as phenyl, halogen atoms such as chlorine and bromine, alkoxycarbonyl groups, cyano group, amino group, etc.

[0040] Illustrative aliphatic residues include straight-­chained or branched alkyl groups, cycloalkyl groups, substituted alkyl or cycloalkyl groups, alkenyl groups and alkynyl groups. Exemplary straight-chained or branched alkyl groups are alkyl groups having 1 - 18, preferably 1 - 8, carbon atoms, such as methyl, ethyl, isobutyl and 1-­octyl. Exemplary cycloalkyl groups include cyclopropyl, cyclohexyl, adamantyl, etc. having 3-10 carbon atoms. Substituents on alkyl and cycloalkyl groups include an alkoxy group (e.g. methoxy, ethoxy, propoxy or butoxy), an alkoxycarbonyl group, a carbamoyl group, a hydroxy group, an alkylthio group, an amido group, an acyloxy group, a cyano group, a sulfonyl group, a halogen atom (e.g. Cl, Br, F or I), an aryl group (e.g. phenyl, halogen-substituted phenyl or alkyl-substituted phenyl), etc. Specific examples of the substituted alkyl or cycloalkyl group include 3-methoxypropyl, ethoxycarbonylmethyl, 4-chloro­cyclohexyl, benzyl, p-methylbenzyl and p-chlorobenzyl. An exemplary alkenyl group is an allyl group, and an exemplary alkynyl group is a propargyl group.

[0041] Preferred examples of the hydrazino compound that can be used in the present invention are listed below and it should be understood that they are by no means intended to limit the scope of the present invention.

[0042] The hydrazine compound represented by the general formula (H) is incorporated in a silver halide emulsion layer and/or a non-light-sensitive layer on the same side as silver halide emulsion layers on a support. Preferably, the hydrazine compound is incorporated in a silver halide emulsion layer and/or an underlying layer. The hydrazine compound is preferably added in an amount of 10⁻⁵ to 10⁻¹ mole per mole of Ag, more preferably from 10⁻⁴ to 10⁻² mole per mole of Ag.

[0043] The tetrazolium compound to be used in the present invention is described below. This tetrazolium compound may be represented by the following general formula (T):

where R₁, R₂ and R₃ are each independently a substituted or unsubstituted phenyl group; X^⊖ is an anion; and n is 2.

[0044] Preferred substituents are either a hydrogen atom or those which have a negative or positive value of Hamett's sigma (σP) which represents an electron withdrawing ability. Substituents having a negative value of σP are particularly preferred.

[0045] Hamett's sigma value in relation to phenyl substitution is found in many documents including the article of C. Hansch et al. in Journal of Medical Chemistry, 20, 304, 1977. Illustrative groups having particularly preferred negative sigma values include: methyl (σP = -0.17; the figures in parentheses that appear in the following description refer to σP values); ethyl (-0.15); cyclopropyl (-0.21); n-propyl (-0.13); iso-propyl (-0.15); cyclobutyl (-0.15); n-butyl (-0.16); iso-o-butyl (-0.20); n-pentyl (-0.15); cyclohexyl (-0.22); amino (-0.66); acetylamino (-0.15); hydroxyl (-0.37); methoxy (-0.27); ethoxy (-0.24); propoxy (-0.25); butoxy (-0.32); and pentoxy (-0.34). All of these groups are useful as substituents on the compound (T) to be used in the present invention.

[0046] Specific examples of the compound of the general formula (T) to be used in the present invention are listed below but it should be understood that they are by no means intended to limit the scope of the present invention.

Illustrative compounds

[0047] 

[0048] The tetrazolium compounds to be used in the present invention can be easily synthesized by known methods, for example, the one described in Chemical Reviews, 55, 335-­483.

[0049] The totrazolium compound to be used in the present invention is preferably incorporated in an amount of from about 1 mg to 10 g, more preferably from about 10 mg to about 2 g, per mole of the silver halide in the silver halide photographic material of the present invention.

[0050] The silver halide in the silver halide emulsion to be used in the photographic material of the present invention may be selected from among those which are commonly used in silver halide emulsions as illustrated by silver bromide, silver chloride, silver iodobromide, silver chlorobromide, silver chloroiodobromide, etc. Silver halide grains may be prepared by an acid method, a neutral method or an ammoniacal method.

[0051] The silver halide grains to be used in the present invention may have a uniform silver halide composition throughout the interior of grains, or they may be core/shell grains having different silver halide compositions in the bulk and the surface layer of grains. The silver halide grains may be of a type in which a latent image is formed predominantly on the surface or of a type in which a latent image is formed predominantly in the bulk.

[0052] The silver halide emulsions to be used in the present invention may be stabilized with various compounds such as those described in prior patents including U.S. Patent Nos. 2,444,607, 2,716,062, 3,512,982, West German Patent Publication Nos. 1,189,380, 2,058, 626, 2,118,411, Japanese Patent Publication No. 4133/1968, U.S. Patent No. 3,342,596, Japanese Patent Publication No. 4417/1972, West German Patent Publication No. 2,149,789, Japanese Patent Publication Nos. 2825/1964 and 13566/1974. Preferred examples of the compounds that can be used for stabilizing purposes include: 5,6-trimethylene-7-hydroxy-5-tria­zolo(1,5-a)pyrimidine, 5,6-tetramethylene-7-hydroxy-5-tria­zole(1,5-a)pyrimidine, 5-methyl-7-hydroxy-S-triazolo(1,5-­a)-pyrimidine, 5-methyl-7-hydroxy-S-triazolo(1,5-a)pyrim­idine, 7-hydroxy-S-triazolo(1,5-a)pyrimidine, 5-methyl-6-­boromo-7-hydroxy-S-triazolo(1,5-a)pyrimidine, gallic acid esters (e.g. isoamyl gallate, dodecyl gallate, propyl gallate and sodium gallate), mercaptans (e.g. 1-phenyl-5-­mercaptotetrazole, 2-mercaptobenzothiazole), benzotriazoles (e.g. 5-bromobenzotriazole, 5-methylbenzotriazole), and benzimidazoles (e.g. 6-nitrobenzimidazole).

[0053] The silver halide photographic material of the present invention and/or developers may have amino compounds incorporated therein.

[0054] In order to provide enhanced developability, developing agents such as phenidone and hydroquinone, or restrainers such as benzotriazole may be incorporated in emulsion layers. Alternatively, developing agents and restrainers may be incorporated in backing layers in order to enhance the ability of various processing solutions.

[0055] Gelatin is used with particular advantage as a hydrophilic colloid in the present invention. Gelatin to be used in the present invention may be pretreated with either an alkali or an acid. If ossein gelatin is to be used, it is preferably freed of the calcium or iron content. The preferred calcium content is from 1 to 999 ppm, with the range of 1 - 500 ppm being more preferred. The preferred iron content is from 0.01 to 50 ppm, with the range of 0.1 - 10 ppm being more preferred. Adjustments of the calcium or iron content can be accomplished by passing an aqueous gelatin solution through an ion-exchanging device.

[0056] Illustrative developing agents that can be used to develop the silver halide photographic material of the present invention include chlorohydroquinone, bromohydroquinone, methylhydroquinone, 2,3-dibromohydro quinone, 2,5-diethylhydroquinone, catechol, its derivatives such as 4-chlorocatechool, 4-phenylcatechol, 3-methyoxy­catechol, pyrogallol, its derivatives such as 4-­acetylpyrogallol, ascorbic acid and its derivatives such as sodium ascorbate.

[0057] Developing agents of Ho-(CH=CH)_n-NH₂ type may be represented by ortho- and para-aminophenols such as 4-­aminophenol, 2-amino-6-phenylphenol, 2-amino-4-chloro-6-­phenylphenol and N-methyl-p-aminophenol.

[0058] Exemplary developing agents of H₂N-(CH=CH)_n-NH₂ type include 4-amino-2-methyl-N,N-diethylaniline, 2,4-diamino-­N,N-diethylaniline-N-(4-amino-3-methylphenyl)morpholine and p-phenylenediamine.

[0059] Exemplary heterocyclic developing agents include 3-­pyrazolidones such as 1-phenyl-3-pyrazolidone, 1-phenyl-­4,4-dimethl-3-pyrazolidone and 1-phenyl-4-methyl-4-­hydroxymethyl-3-pyrazolidone, 1-phenyl-4-amino-5-­pyrazolone, and 5-aminouracil.

[0060] The developing agents that can be used effectively in the present invention are described in T.H. James, ed., The Theory of the Photographic Process, 4th ed., pp. 291-334 and Journal of the American Chemical Society, 73, 3,100 (1951). These developing agents may be used either singly or as admixtures and they are preferably used as admixtures. Developers that are used to develop the photographic material of the present invention may contain preservatives selected from among sulfites such as sodium sulfite and potassium sulfite and the inclusion of such preservatives will not be deleterious to the objects of the present invention. Hydroxylamines and hydrazide compounds may also be used as preservatives and, in this case, they are preferably used in amounts of 5 - 500 g, more preferably from 20 to 200 g, per liter of the developer.

[0061] Glycols may be contained as organic solvents in the developer and exemplary glycols include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, 1,4-butanediol and 1,5-pentanediol, with diethylene glycol being preferably used. These glycols are preferably used in amounts of 5 - 500 g, more preferably from 20 to 200 g, per liter of the developer. These organic solvents may be used either singly or as admixtures.

[0062] The silver halide photographic material of the present invention has very good keeping quality if it is processed with a developer that contains one or more of the development restrainers described above.

[0063] The developer of the composition described above preferably has a pH of 9 - 13, with the range of 10 - 12 being more preferred from the viewpoint of preservability and photographic characteristics. As regards cations in the developer, the proportion of potassium ions is preferably higher than that of sodium ions in order to enhance the activity of the developer.

[0064] The silver halide photographic material of the present invention can be processed under various conditions. The processing temperature, for example, the development temperature is preferably not higher than 50°C, more preferably within the range of about 25 - about 40°C. The development time is typically set to be no longer than 2 min, and particularly good results are often achieved by completing the development within 10 - 50 sec. Other processing steps such as washing, stopping, stabilizing and fixing may also be performed under usual conditions. If desired, prehardening, neutralizing and any other necessary steps may be included. Of course, these steps may be omitted depending on the case. Development may be carried out either manually (e.g. tray development or rack development) or mechanically (e.g. roller development or hanger development).

[0065] The following examples are provided for the purpose of further illustrating the present invention but are in no way to be taken as limiting.

Example 1

[0066] Subbed polyethylene terephthalate films were subjected to corona discharge treatment at an energy of 8 W/m² per min. Thereafter, antistatic coating solutions having the composition described below were applied with a roll fit coating pan and an air knife at a rate of 30 m/min to provide deposits also shown below.
Water-soluble conductive polymer (A) 0.6 g/m²
Hydrophobic polymer particles (B) 0.4 g/m²
Nonionic surfactant (Ao) 0.004 g/m²
The hydrophobic polymer particles (B) were dispersed with the nonionic surfactant and used as a latex. Hardener (H)

[0067] The applied antistatic coatings were dried at 90°C for 2 min and subsequently heat-treated at 140°C for 90 sec.

[0068] Gelatin was applied onto these antistatic coatings to provide a deposit of 2.0 g/m². The so prepared samples were subjected to a haze test. Formaldehyde and 2,4-­dichloro-6-hydroxy-S-triazine sodium were used as hardeners of gelatin. The results of the haze test are shown in Table 1.

Haze test

[0069] Using a turbidimeter Model T-2600DA of Tokyo Denshoku K.K., the film supports were measured and percent haze was determined.

Table 1

No.	Water-soluble conductive polymer (A)	Hydrophobic polymer particles (B)	Nonionic surfactant (Ao)	Haze	Remarks
1	3	a	-	80	Comparison
2	3	1	1	90	Invention
3	5	2	2	95
4	7	2	2	93
5	9	3	2	95
6	13	3	9	95
7	18	6	15	92
8	20	2	2	90
9	21	8	19	94
10	22	8	28	93
11	24	2	2	93
12	41	3	9	92
13	3	16	1	90
14	5	17	2	95
15	7	17	2	93
16	9	18	2	95
17	13	18	9	95
18	18	21	15	92
19	20	17	2	90
20	21	23	19	94
21	22	23	28	93
22	24	17	2	93
23	41	18	9	92

a: compound described in Unexamined Published Japanese Patent Application No. 84658/1980:

[0070] Table 1 shows that the samples prepared in accordance with the present invention had satisfactory haze resistance.

Example 2

Preparation of emulsions:

[0071] Silver chlorobromide (5 mol% AgBr) grains that contained a rhodium salt in an amount of 10⁻⁵ mole per mole of silver and which had an average grain size of 0.11 µm with a monodispersibility of 15 were prepared by a controlled double-jet method in an acidic atmosphere (pH 3.0). The grains were grown in a system containing 30 mg of benzyladenine in 1,000 ml of a 1% aqueous gelatin solution. After mixing silver and the halide, 6-methyl-4-­hydroxy-1,3,3a-7-tetraazaindene was added in an amount of 600 mg per mole of silver halide, and the mixture was subsequently washed and desalted.

[0072] In the next step, 6-methyl-4-hydroxy-1,3,3a,7-­tetraazaindene was added in an amount of 60 mg per mole of silver halide and thereafter sodium thiosulfate was added in an amount of 15 mg per mole of silver halide, followed by sulfur sensitization at 60°C. After the sulfur sensitization, 6-methyl-4-hydroxy-1,3,3a,7-tetraazaindene was added as a stabilizer in an amount of 600 mg per mole of silver halide.

[0073] To the thus prepared emulsions, the additives shown below were added to provide the deposits also shown below, and the resulting coating solutions were applied onto polyethylene terephthalate supports in a thickness of 100 µm that had been subbed with a latex polymer in accordance with Example 1 described in U.S. Patent No. 4571379.

Protective film for emulsion layer:

[0074] Coating solution for the protective film for the emulsion layer was prepared to provide the deposits described below and was applied together with the emulsion to be superposed on the latter.

Fluorinated dioctyl sulfosuccinate ester	200 mg/m²
Sodium dodecylbenzenesulfonate	100 mg/m²
Matting agent (polymethyl methacrylate; average particle size, 3.5 µm)	100 mg/m²
Lithium nitrate salt	30 mg/m²
Propyl gallate ester	300 mg/m²
Sodium 2-mercaptobenzimidazole-5-sulfonate	30 mg/m²
Alkali-processed gelatin (isoelectric point, 4.9)	1.3 g/m²
Colloidal silica	30 mg/m²
Styrene-maleic acid copolymer	100 mg/m²
Bis(vinylsulfonylmethyl)ether	15 mg/m²

[0075] The other side of the support which was opposite the emulsion layer was subjected to corona discharge treatment at a power of 30 W/m² per min and coated with a poly(styrene-butyl acrylate-glycidyl methacrylate) latex polymer in the presence of a hardener (hexamethylene aziridine), and further overlaid with an antistatic coating as in Example 1. Subsequently, a coating solution for backing layer was prepared to the formula indicated below in such a way the additives contained would have the deposits also shown below. The so prepared solution was coated to form a backing layer.

Protective film for backing layer:

[0076] A coating solution for the protective film for backing layer was prepared to the formula shown below in such a way that the additives used would provide the deposits also shown below. The so prepared coating solution was applied together with the backing layer in superposion on the latter.

Dioctyl sulfosuccinate ester	200 mg/m²
Matting agent (polymethyl methacrylate; average particle size, 4.0 µm)	50 mg/m²
Alkali-processed gelatin (isoelectric point = 4.9)	1.0 g/m²
Fluorinated sodium dodecylbenzene-sulfonate	50 mg/m²
Bis(vinylsulfonylmethyl)ether	20 mg/m²

[0077] The coating solutions described above were applied after preliminary pH adjustment to 5.4.

[0078] Each of the samples thus prepared was divided into two parts; one part was stored at 23°C × 55% r.h. for 3 days, and the other part was humidified at 23°C × 55% for 3h. packed in superposion on the another in a moisture-proof bag and stored under accelerated aging conditions (at 55°C for 3 days) to prepare aged specimens. Both types of specimens were exposed through an optical step wedge and processed with a developer and a fixing solution that had the formulations shown below. Thereafter, the sensitivity and specific surface resistance of each specimen were measured. The sensitivity was determined as the amount of exposure necessary to provide an optical density of 1.0 and expressed in terms of relative values.

[0079] The results are shown in Table 2.

Processing scheme
Step	Temperature (°C)	Time (sec)
Development	34	15
Fixing	32	10
Washing	R.T.	10

Developer
Hydroquinone		25 g
1-Phenyl-4,4-dimethyl-3-pyrazolidone		0.4 g
Sodium bromide		3 g
5-Methyl benzotriazole		0.3 g
5-Nitroindazole		0.05 g
Diethylaminopropane-1,2-diol		10 g
Potassium sulfite		90 g
Sodium 5-sulfosalicylate		75 g
Ethylenediaminetetraacetic acid sodium salt		2 g
Water		to make 1,000 ml
pH adjusted to 11.5 with sodium hydroxide

Fixing solution
Formula A
Ammonium thiosulfate (72.5 wt% aq. sol.)	240 ml
Sodium sulfite	17 g
Sodium acetate (3H₂O)	6.5 g
Boric acid	6 g
Sodium citrate (2H₂O)	2 g
Acetic acid (90 wt% aq. sol.)	13.6 ml

Formula B
Pure water (ion-exchanged water)	17 ml
Sulfuric acid (450 wt% aq. sol.)	4.7 g
Aluminum sulfate (aq. sol. with 8.1 wt% Al₂O₃)	26.5 g

[0080] Before use, formulas A and B were successively dissolved in 500 ml of water and worked up to a total volume of 1,000 ml. The resulting fixing solution had a pH of ca. 4.3.

Table 2

No.	Water-soluble conductive polymer (A)	Hydrophobic polymer particles (B)	Nonionic surfactant (Ao)	Hydrazine compound (H)	Specific surface resistance		Relative sensitivity		Remarks
					I*	II**	I*	II**
1	3	a	-	9	3.0 × 10¹⁰	3.0 × 10¹³	100	30	Comparison
2	3	1	1	9	4.0 × 10¹⁰	2.0 × 10¹¹	100	90	Invention
3	20	2	2	24	2.0 × 10¹⁰	8.0 × 10¹⁰	110	100
4	7	2	2	14	5.0 × 10¹⁰	4.0 × 10¹¹	120	100
5	9	3	2	14	5.0 × 10¹⁰	6.0 × 10¹¹	110	95
6	18	6	15	24	3.0 × 10¹⁰	7.0 × 10¹¹	105	100
7	3	16	1	6	3.0 × 10¹⁰	5.0 × 10¹¹	100	85
8	5	17	2	9	4.0 × 10¹⁰	4.0 × 10¹¹	105	90
9	24	17	2	43	5.0 × 10¹⁰	5.0 × 10¹¹	110	100
10	9	18	2	10	5.0 × 10¹⁰	3.0 × 10¹¹	110	100
11	18	21	15	12	8.0 × 10¹⁰	8.0 × 10¹¹	120	105
12	21	23	19	24	2.0 × 10¹⁰	5.0 × 10¹¹	105	90

*I: Measured after storage at 23°C × 55% r.h. for 3 days.

*II: Measured after storage in moisture-proof bag at 55°C for 3 days following humidification at 23°C × 55% r.h. for 3h.

[0081] As is clear from the data in Table 2, the samples prepared in accordance with the present invention experienced less desensitization during storage and the antistatic coating used did not deteriorate so much as the comparative sample upon processing.

Example 3

[0082] Silver chlorobromide (2 mol% AgBr) grains that contained a rhodium salt in an amount of 10⁻⁵ mole per mole of silver and which had an average grain size of 0.20 µm at a monodispersibility of 20 were prepared as in example 2. These grains were desalted and subjected to sulfur sensitization as in Example 2.

[0083] Additives prepared to provide the deposits described below were added to the emulsion thus prepared, and the resulting coating solution was applied to subbed polyethylene terephthalate films of the same type as used in Example 1.

[0084] The coating solution described above was applied after preliminary pH adjustment to 6.5 with sodium hydroxide. A coating solution for protective film for the emulsion layer was prepared using the additives described below in such a way that they would provide the deposits also shown below, and the thus prepared coating solution was applied together with the emulsion coating solution in superposition on the latter.

Fluorinated dioctyl sulfosuccinate ester	100 mg/m²
Dioctyl sulfosuccinate ester	100 mg/m²
Matting agent (amorphous silica)	50 mg/m²
Compound (O)	30 mg/m²
5-Methylbenzotriazole	20 mg/m²
Compound (P)	500 mg/m²
Propyl gallate ester	300 mg/m²
Styrene-maleic acid copolymer	100 mg/m²
Alkali-processed gelatin (isoelectric point = 4.9)	1.0 g/m²
Formaldehyde	10 mg/m²
Polyacrylamide	500 mg/m²

[0085] This coating solution was applied after preliminary pH adjustment to 5.4 with citric acid.

[0086] In the next step, an antistatic coating and a backing layer were provided as in Example 2 on the other side of the support which was opposite the emulsion layer, except that formaldehyde was used as a hardener in the backing layer.

[0087] The samples thus prepared were processed and their performance evaluated as in Example 2, except that the following two recipes were used as developer. The results are shown in Table 3.

Formula A
Pure water (ion-exchanged water)	150 mℓ
Ethylenediaminetetraacetic acid disodium salt	2 g
Diethylene glycol	50 g
Potassium sulfite (55% w/v aq. sol.)	100 ml
Potassium carbonate	50 g
Hydroquinone	15 g
1-Phenyl-3-pyrazolidone	0.5 g
1-Phenyl-5-mercaptotetrazole	30 mg
Potassium hydroxide	q.s. for pH 10.4
Potassium bromide	4.5 g

Formula B
Pure water (ion-exchanged water)	3 mg
Diethylene glycol	50 g
Ethylenediaminetetraacetic acid disodium salt	25 mg
Acetic acid (90% aq. sol.)	0.3 ml

[0088] Before use, formulas A and B were successively dissolved in 500 ml of water and worked up to a total volume of 1,000 ml.

Table 3

No.	Water-soluble conductive polymer (A)	Hydrophobic polymer particles (B)	Nonionic surfactant (Ao)	Tetrazolium compound (T)	Specific surface resistance		Relative sensitivity		Remarks
					I*	II**	I*	II**
1	3	a	-	2	4.0 × 10¹⁰	5.0 × 10¹³	100	30	Comparison
2	3	1	1	2	4.0 × 10¹⁰	3.0 × 10¹¹	100	80	Invention
3	3	16	1	2	4.0 × 10¹⁰	5.0 × 10¹¹	100	90
4	5	17	2	2	5.0 × 10¹⁰	7.0 × 10¹⁰	105	95
5	7	2	2	3	3.0 × 10¹⁰	2.0 × 10¹¹	105	90
6	13	3	9	5	7.0 × 10¹⁰	5.0 × 10¹¹	110	100
7	13	18	9	7	6.0 × 10¹⁰	2.0 × 10¹¹	110	100
8	20	2	2	7	6.0 × 10¹⁰	6.0 × 10¹¹	105	95
9	21	23	19	16	5.0 × 10¹⁰	6.0 × 10¹¹	100	95
10	22	8	28	9	5.0 × 10¹⁰	5.0 × 10¹¹	100	85
11	22	23	28	2	4.0 × 10¹⁰	5.0 × 10¹¹	105	100
12	41	3	9	16	8.0 × 10¹⁰	5.0 × 10¹¹	100	90

*I: Measured after storage at 23°C × 55% r.h. for 3 days.

*II: Measured after storage in moisture-proof bag at 55°C for 3 days following humidification at 23°C × 55% r.h. for 3h.

[0089] As is clear from the data in Table 3, the samples prepared in accordance with the present invention experienced less desensitization during storage and the antistatic coating used did not deteriorate so much as the comparative sample upon processing. The result was the same whether a hydrazine compound was used as in Example 2 or a tetrazolium compound was used as in Example 3.

[0090] The present invention successfully provides a highly stable silver halide photographic material that has a haze-­free and highly transparent antistatic coating and which will undergo less increase in specific surface resistance over time as well as less desensitization even if a supercontrasty agent such as a tetrazolium or hydrazine compound is used.

Claims

1. In a silver halide photographic material having at least a light-sensitive emulsion layer and an antistatic coating containing (1) a water-soluble conductive polymer, (2) hydrophobic polymer particles and (3) a curing agent on a plastic film support, the improvement wherein said hydrophobic polymer particles contain an acrylamide group or contain styrene and an alkyl acrylate and/or an alkyl methacrylate that have 1 - 12 carbon atoms, and form a stable dispersion with the aid of a nonionic surfactant having 3 or more alkylene oxide chains.

2. A silver halide photographic material according to claim 1 wherein said water-soluble conductive polymer has at least one conductive group selected from the group consisting of a sulfonic acid groups, a sulfate ester group, a quaternary ammonium salt group, a tertiary ammonium salt group, a carboxyl group and a polyethylene oxide group.

3. A silver halide photographic material according to claim 1 wherein said water-soluble conductive polymer has at least one conductive group selected from the group consisting of a sulfonic acid group, a sulfate ester group and a quaternary ammonium salt group.

4. A silver halide photographic material according to claim 3 wherein said conductive group is contained in an amount of at least 5 wt% per molecule of the water-soluble conductive polymer.

5. A silver halide photographic material according to claim 3 wherein said water-soluble conductive polymer has at least one group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, an epoxy group, an aziridine group, an active methylene group, a sulfinic acid group, a vinylsulfone group and an aldehyde group.

6. A silver halide photographic material according to claim 5 wherein said at least one group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, an epoxy group, an aziridine group, an active methylene group, a sulfinic acid group, a vinylsulfone group and an aldehyde group is contained in an amount of at least 5 wt% per molecule of the water-soluble conductive polymer.

7. A silver halide photographic material according to claim 1 wherein said water-soluble conductive polymer has a molecular weight of 3,000 - 100,000.

8. A silver halide photographic material according to claim 1 wherein said water-soluble conductive polymer is contained in an amount of 0.01 - 10 g/m².

9. A silver halide photographic material according to claim 1 wherein said hydrophobic polymer particles contain at least 0.1 mol% of an acrylamide derivative and/or a methacrylamide derivative.

10. A silver halide photographic material according to claim 1 wherein said hydrophobic polymer particles contain at least 10 mol% of a styrene derivative and an alkyl acrylate and/or an alkyl methacrylate.

11. A silver halide photographic material according to claim 1 wherein said hydrophobic polymer particles have a molecular weight of at least 3,000.

12. A silver halide photographic material according to claim 1 wherein said hydrophobic polymer particles are used in an amount in the range of from 0.1 to 10 g/m².

13. A silver halide photographic material according to claim 1 wherein said curing agent is a polyfunctional aziridine.

14. A silver halide photographic material according to claim 13 wherein said polyfunctional aziridine is bi- or trifunctional.

15. A silver halide photographic material according to claim 14 wherein said polyfunctional aziridine has a molecular weight of no more than 600.

16. A silver halide photographic material according to claim 1 wherein said curing agent is used in amount in the range of from 0.01 to 10 g/m².

17. A silver halide photographic material according to claim 1 wherein said nonionic surfactant is a compound containing at least three polyalkylene oxide chains in the molecule.

18. A silver halide photographic material according to claim 1 wherein said nonionic surfactant is used in an amount in the range of from 0.0001 to 0.1 g/m².

19. A silver halide photographic material according to claim 1 wherein said light-sensitive emulsion layer contains a tetrazolium or hydrazine compound.

20. A silver halide photographic material according to claim 19 wherein said tetrazolium compound is represented by the following general formula (T):

where R₁, R₂ and R₃ are each independently a phenyl group or a substituted phenyl group; X^⊖ is an anion; and n is 2.

21. A silver halide photographic material according to claim 20 wherein said tetrazolium compound is used in an amount in the range of from 1 mg to 10 g per mole of silver halide.

22. A silver halide photographic material according to claim 19 wherein said hydrazine compound is represented by the following general formula (H):

where R₁ is a monovalent organic residue; R₂ is a hydrogen atom or a monovalent organic residue; Q₁ and Q₂ are each a hydrogen atom, an optionally substituted alkylsulfonyl group, or an optionally substituted arylsulfonyl group; and X₁ is an oxygen atom or a sulfur atom.

23. A silver halide photographic material according to claim 19 wherein said hydrazine compound is used in an amount in the range of from 10⁻⁵ to 10⁻¹ mole per mole of silver halide.

24. A silver halide photographic material according to claim 1 wherein said plastic film support is made of polyethylene terephthalate or cellulose triacetate that transmits at least 90% of visible light.