JP2007316193A - Heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material which excels in pre-exposure storage stability while having low fog, excels also in stability of a silver image after heat development, and provides high maximum density even by short-time heat development. <P>SOLUTION: The heat developable photosensitive material has a photosensitive layer containing a photosensitive emulsion, a reducing agent and a binder on a support, wherein the photosensitive layer contains a hydrophobic protective colloidal fine particle dispersion prepared by adding a dispersant having a functional group with an affinity for a hydrophilic group of a protective colloid to an aqueous dispersant solution of silver halide fine particles dispersed with a hydrophilic natural polymer dispersant as the protective colloid, and the photosensitive layer contains a binder having a polymerization degree of 600-3,000 and a binder having a polymerization degree of 100-400. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photothermographic material (also referred to as a photothermographic material, a photothermographic material, or simply a photosensitive material) having a photosensitive layer containing a photosensitive emulsion, a reducing agent, and a binder.

  Conventionally, in the fields of medical treatment and printing plate making, waste liquid from wet processing of image forming materials has been a problem in terms of workability. In recent years, reduction of waste processing liquid has been strongly desired from the viewpoint of environmental conservation and space saving. ing. Therefore, there is a need for technology related to photothermographic materials that can be used for efficient exposure, such as laser imagers and laser imagesetters, and that can form high-resolution and clear black images. Yes.

  As such a technique, a photothermographic material containing an aliphatic carboxylic acid silver salt, a photosensitive silver halide and a reducing agent on a support is known (see, for example, Non-Patent Document 1 and Patent Document 1). Since this photothermographic material does not use any solution processing chemicals, it is possible to provide a user with a simpler system that does not damage the environment.

  By the way, these photothermographic materials have built-in photosensitive silver halide grains installed in a photosensitive layer (photosensitive layer) as a photosensor, and aliphatic carboxylic acid silver salt as a silver ion supply source. An image is formed by heat development usually at 80 ° C. or higher with the reducing agent thus formed, and fixing is not performed.

  The silver halide emulsion used as a light receiving element in the photothermographic material as described above, particularly a photothermographic material formed by a solvent-based coating method, is a protective colloid of a hydrophilic natural polymer dispersant such as gelatin. As silver halide grains are exposed to an organic solvent, there is a problem that grain aggregation or unnecessary grain growth (also referred to as ripening) occurs. However, gelatin is a protective colloid, such as silver halide grain formation technology using aqueous media, chemical sensitization technology of silver halide grains using water-soluble sensitizers, and storage technology for silver halide emulsions using gelatin gelation. There are many conventional techniques that have advantages in use, and problems such as aggregation of silver halide grains generated in a solvent system have been promoted with some degree of compromise.

  Conventionally, as a method of improving the aggregation of silver halide grains, long-chain fatty acids are dispersed in silver halide grains by adding silver halide grains in the process of forming organic silver salt grains contained in a photothermographic material. Aggregation is mitigated by using an agent. However, in this method, the dispersibility of the silver halide grains is insufficient, and furthermore, since it is a mixed system with an organic silver salt, fogging, which is one of the important characteristics as a photothermographic material, has increased, and is still The current situation is that the problem has not been solved.

  In the past, water-based dispersed AgX particles were mixed at the time of fatty acid silver particle preparation, color point loss due to maturation and aggregation of AgX particles (Dmax decrease), and fog increase due to increased contact probability with fatty acid silver salt (development) Time and storage) was a major issue.

  Further, since the photothermographic material contains an aliphatic carboxylic acid silver salt, a photosensitive silver halide and a reducing agent, fog is likely to occur during the storage period before heat development. In addition, after exposure, only heat development is performed and fixing is not performed. Therefore, even after heat development, all or a part of silver halide, aliphatic carboxylic acid silver salt, and reducing agent coexist and remain for a long time. However, there is a problem that metallic silver is generated in the light-sensitive material by heat or light, and the image quality of the silver image is likely to change.

Furthermore, in recent years, rapid thermal development is progressing, and it is required to obtain a high-density image in a short time. A reducing agent is effective as a means for solving these problems (see, for example, Patent Documents 2 and 3). When a photosensitive material before heat development is stored for a long time, and when a silver image obtained after heat development is stored for a long time. There is a problem that fog is likely to occur. In addition, since the color tone of the image silver to be formed is yellowish, it tends to cause a decrease in diagnostics particularly in medical applications, and further improvement has been demanded.
"DrySilver Photographic Materials" (Handbook of Imaging Materials, Marcel Dekker, Inc., p. 48, 1991) US Pat. No. 3,152,904 JP 2001-188314 A JP 2004-4650 A

  The object of the present invention is to provide excellent heat preservation, low fog, excellent stability of a silver image after heat development, high density even in short time heat development, and good silver tone. It is to provide a development photosensitive material.

  The above object of the present invention has been achieved by the following constitution.

1.
In a photothermographic material having a photosensitive layer containing a photosensitive emulsion, a reducing agent, and a binder on a support, the photosensitive layer contains silver halide fine particles in which a hydrophilic natural polymer dispersant is dispersed as a protective colloid. Hydrophobic protective colloid fine particle dispersion prepared by adding a dispersant having a functional group having an affinity for the hydrophilic group of the protective colloid to an aqueous dispersion, and a photosensitive layer having a polymerization degree of 600 to A photothermographic material comprising a 3,000 binder and a binder having a polymerization degree of 100 to 400.
2.
2. The photothermographic material according to item 1, wherein the binder contains two or more binders having a polymerization degree of 600 to 3,000.
3.
3. The photothermographic material according to item 1 or 2, wherein the binder is a polyvinyl acetal resin.
4).
4. The photothermographic material according to any one of items 1 to 3, wherein the dispersant is an organic polymer.
5).
The hydrophobic protective colloid fine particle dispersion was prepared by adding a dispersant to an aqueous dispersion of silver halide fine particles to precipitate the silver halide fine particles, and dispersing the precipitate in a hydrophobic solvent. 5. The photothermographic material according to any one of items 1 to 4, wherein:
6).
The photothermographic material according to any one of 1 to 5, wherein the reducing agent is represented by the following general formula (1).

[Wherein, R ₁ represents a hydrogen atom or a substituent, and R ₂ and R ₃ each represents a branched alkyl group having 3 to 8 carbon atoms. A ₁ and A ₂ each represent a hydroxyl group or a group that can be deprotected to form a hydroxyl group, and n and m each represents an integer of 3 to 5. ]

  According to the present invention, there is provided a photothermographic material which is low in fog and can obtain a high maximum density even in short-time heat development, has almost no increase in fog during storage, and is excellent in stability of a silver image after heat development. it can.

  Hereinafter, the photothermographic material of the present invention will be described in detail sequentially for each constituent material.

[Hydrophilic natural polymer as protective colloid]
The natural polymer that can be used in the present invention is not particularly limited except that it is hydrophilic. For example, gelatin and its derivatives, graft polymers of gelatin and other polymers, proteins such as albumin and casein. , Sugar derivatives such as sodium alginate and starch derivatives, etc., but in the present invention, silver halide grains are prevented from agglomerating, silver halide grains are dispersed relatively uniformly, and finally developed. From the viewpoint of controlling silver into a desired shape, gelatin is preferably used, and those obtained by chemically modifying hydrophilic groups such as amino groups and carboxyl groups of gelatin to improve the properties of gelatin are preferable.

As gelatin, it is preferable to use chemically modified gelatin as described above. Here, “chemically modified gelatin” refers to —C (═O) O—, —NH—, —N═, —N <, —O—, —S—, —NH—C () present in gelatin. = NH ₂ ⁺ ) Gelatin modified by reacting a compound that reacts with a reactive group such as NH- and -NH-C (= NH) NH-.

  For example, examples of the hydrophobic modification of an amino group in a gelatin molecule include phenylcarbamoylation, phthalation, cinnamoylation, acetylation, benzoylation, and nitrophenylation. Examples of the hydrophobic modification of the carboxyl group include methyl esterification and amidation.

  In the present invention, it is preferable to use gelatin obtained by chemically modifying an appropriate number of amino groups among the amino groups present in gelatin.

  Hereinafter, the gelatin in which the amino group is chemically modified will be described in detail.

  As the amino group in gelatin, the amino group of the gelatin molecule end group, lysine group, hydroxy lysine group, histidine group, amino group of arginine group, as well as the amino group of arginine group if converted to ornithine group. Can be mentioned. Furthermore, impurity groups, such as an adenine group and a guanine group, can also be mentioned.

The chemical modification of the amino group (—NH ₂ ) is to add a reaction reagent to gelatin and react with the amino group to form a covalent bond or deaminate. That is, it refers to changing a primary amino group (—NH ₂ ) to a secondary amino group (—NH—), a tertiary amino group (—N <), or a deaminated product.

Specifically, for example, acid anhydrides (maleic anhydride, o-phthalic anhydride, succinic anhydride, isatoic anhydride, benzoic anhydride, etc.), acid halides (R-COX, R-SO, etc.) ₂ X, R—O—COX, phenyl-COCl, etc.), aldehyde compound (R—CHO, etc.), epoxy group-containing compound, deaminating agent (HNO ₂ , deaminase, etc.), active ester compound (sulfonic acid ester, p -Nitrophenyl acetate, i-propenyl acetate, methyl o-chlorobenzoate, p-nitrophenyl benzoate, etc.), isocyanate compounds (aryl isocyanate, etc.), active halogen compounds [aryl halides (benzyl bromide, biphenylhalomethanes, benzoylhalomethane) , Phenylbenzoylhalomethane, 1-fluoro-2.4-dinini Chloro derivatives of (robenzene), β-ketohalide, α-haloaliphatic acid, β-halonitrile, (s-triazine, pyrimidine, pyridazine, pyrazine, pyridazone, quinoxaline, quinazoline, phthalazine, benzoxazole, benzothiazole, benzimidazole) Carbamoylating agents (cyanate, nitrourea, etc.), acrylic type active double bond group-containing compounds (maleimide, acrylic amine, acrylamide, acrylonitrile, methyl methacrylate, vinyl sulfone, vinyl sulfonate ester, sulfonamide, styrene and vinyl pyridine, Allylamine, butadiene, isoprene, chloroprene, etc.), sultone (butane sultone, propane sultone), guanidine agent (o-methylisourea, etc.), dithiocarbamate (4- (N, N- diethyl-dithiocarbamyl) and benzoic acid), a carboxyl azide addition can be accomplished by reacting.

In this case, from the reagent to form covalent bonds react with -OH group or -COOH group of gelatin, more preferred reagents primarily react with -NH ₂ groups of the gelatin. Chemical modification is mainly 60% or more, preferably 80 to 100%, more preferably 95 to 100%.

  Furthermore, it is more preferable that the reaction product does not substantially contain (a group in which the ether bond or oxygen in the ketone group is replaced with a chalcogen atom, for example, —S— or a thione group). Here, “substantially free” refers to preferably 10% or less, more preferably 0 to 3% of the number of chemically modified groups. Therefore, among the above, acid anhydrides, sultone compounds, compounds having an active double bond group, carbamoylating agents, active halogen compounds, isocyanate compounds, active ester compounds, compounds having an aldehyde, and deaminating agents are more preferable. An embodiment in which cross-linking between gelatin molecules cannot be substantially achieved by the chemical modification is more preferable. Here, “substantially not possible” is preferably 10% or less of the chemically modified group, more preferably 0 to 3%.

Further speaking, chemical modification preferably in the form of -COOH group is introduced 1-3 every time -NH ₂ group is one modification, the -COOH group per the -NH ₂ group is one modified One form of chemical modification is more preferred. Examples of reagents used for chemical modification include succinic anhydride, phthalic anhydride, and maleic anhydride when one —COOH group is introduced per one —NH ₂ group, and two —COOH groups are introduced. In this case, trimellitic anhydride is used, and in the case of introducing three —COOH groups, pyromellitic anhydride is used.

In particular, phthalated gelatin obtained by chemically modifying the —NH ₂ group with phthalic anhydride is preferable in that it can be produced industrially stably in addition to the great effect of the present invention.

  Regarding other details of the chemical modification agent and the chemical modification method of gelatin, JP-A-4-226449, JP-A-50-3329, U.S. Pat. Nos. 2,525,753, 2,614,928, 2,614,929, 2,763,639, 2,594,293, 3,132,945, edited by Yoshihiro Abiko: Niwa to Gelatin, Chapter II, Niwa to Gelatin Industry Association (1987), edited by Ward et al .: The Science and Technology of Gelatin, Chapter 7, Academic Press (1977). it can.

  In the chemically modified gelatin according to the present invention, the amino group chemical modification% is preferably 30 to 100%, more preferably 30 to 90%, and particularly preferably 45 to 80%. . If the modification rate is less than 30%, the aggregation and precipitation properties are reduced in the desalting step, and a large amount of an aggregating agent that affects the photographic performance is required.

  The methionine content of the chemically modified gelatin of the present invention is not particularly defined, but is preferably 30 μmol / g or more, more preferably 35 μmol / g or more.

  The molecular weight of the chemically modified gelatin is preferably 10,000 to 200,000, more preferably 20,000 to 90,000.

The chemical modification% of the —NH ₂ group of the chemically modified gelatin can be determined as follows.

Gelatin that has not been chemically modified and gelatin that has been chemically modified are prepared, and the number of —NH ₂ groups of both is determined as e1 and e2. The chemical modification% can be obtained from 100 × (e1−e2) / e1. The method for obtaining e1 and e2 can include methods using infrared absorption intensity based on —NH ₂ group, NMR signal intensity of the proton, color reaction and fluorescence reaction. The description of Organic Edition-2, Maruzen (1991) can be referred to. Other examples include changes in the titration curve of gelatin and quantitative methods such as the formol titration method. For details, see the description in The Science and Technology of Gelatin (supra), Chapter 15. Can be.

There is no particular limitation on the addition timing of the amino group-modified gelatin in the present invention. Generally, it is added in the step of silver halide grain formation, immediately before the desalting step or in the redispersion step after desalting, but each time one —NH ₂ group is modified, a —COOH group is added. It is preferable to add gelatin that is chemically modified so that one is introduced before the desalting step (that is, add it before the start of the desalting step at the latest).

[Dispersant]
The polymer used in the present invention has a function of precipitating and separating silver halide grains by adding and mixing to a photosensitive silver halide grain aqueous dispersion containing a natural polymer as a protective colloid, and an organic solvent dispersion. Can function as a dispersant for photosensitive silver halide grains. More preferably, it has a function capable of changing dispersion in an organic solvent system to an easy one as a thermosensitive polymer or as a hydrophobic colloid. That is, the polymer according to the present invention is water-soluble at a temperature lower than a specific temperature “also called Lower Critical Solution Temperature (LCST)”, and at a temperature higher than the specific temperature. Preferably it can be hydrophobic.

  The “n-octanol / water / logarithm of distribution coefficient (log P value)” is an index representing the degree of hydrophobicity or hydrophilicity of a substance. As a common logarithm of the concentration ratio (concentration in organic solvent / concentration in water) when the substance is dissolved in an organic solvent (usually n-octanol) that does not mix with water and mixed with water and reaches equilibrium Desired.

  The logP value can be measured by a flask permeation method described in JIS Z 7260-107 (2000). The logP value can also be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27, 21 (1987)), Viswanadhan's fragmentation method (J. Chem. Inf. Comput. Sci., 29,). 163 (1989).), Broto's fragmentation method (Eur. J. Med. Chem.-Chim. Theor., 19, 71 (1984).) And the like are preferably used, among which the Crippen's fragmentation method is more preferable. preferable. When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the scope of the present invention by the Crippen's fragmentation method.

  As an organic polymer (hereinafter also referred to as a synthetic polymer) applicable to the present invention, a polymer having a log P value of 0.8 to 2.0 is preferable. For example, polyvinyl alcohols, hydroxyethyl celluloses, cellulose acetates, cellulose acetates Butylates, polyvinylpyrrolidones, casein, starch, poly (acrylic acid and acrylate), poly (methyl methacrylic acid and methacrylic ester), polyvinyl chloride, polymethacrylic acid, styrene-maleic anhydride Polymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, polyvinyl acetals (polyvinyl formal and polyvinyl butyral), polyesters, polyurethanes, phenoxy resins, polyvinylidene chlorides, polymers Epoxides, polycarbonates, polyvinyl acetates, polyolefins, cellulose esters, polyamides, and the like.

  Several types of these synthetic polymers may be copolymers, but synthetic polymers obtained by copolymerizing monomers of acrylic acid, methacrylic acid and esters thereof are particularly preferable.

  The synthetic polymer according to the present invention may be a polymer that dissolves in both water and an organic solvent in the same state, but may be dissolved or insolubilized in water or an organic solvent by controlling pH or controlling temperature. included. For example, although a polymer having an acidic group such as a carboxyl group becomes hydrophilic in a dissociated state depending on the type, it becomes lipophilic and can be made soluble in a solvent when the pH is lowered to a non-dissociated state. Conversely, a polymer having an amino group becomes lipophilic when the pH is raised, and becomes ionized and water-soluble when the pH is lowered.

  Nonionic activators are well known for the phenomenon of cloud point, but some polymers have the property that they become lipophilic and soluble in organic solvents with increasing temperature, and are hydrophilic, that is, soluble in water, with decreasing temperature. It is included in the present invention. It is sufficient that micelles are formed and uniformly emulsified even if they are not completely dissolved.

  In the present invention, since various monomers are combined, it is not generally stated which monomer should be used and to what extent, but it is desirable to combine a hydrophilic monomer and a hydrophobic monomer in an appropriate ratio. It can be easily understood that the following polymer is obtained.

  The polymer that dissolves in both the water and the organic solvent may have a solubility of at least 1% by mass (25 ° C.) with respect to water, although it may be adjusted by adjusting the conditions such as pH as described above or not adjusted. The organic solvent preferably has a solubility of, for example, 5% by mass (25 ° C.) in methyl ethyl ketone.

  As the polymer that is soluble in both water and the organic solvent according to the present invention, a so-called block polymer, graft polymer, comb polymer, and the like are more suitable than a linear polymer from the viewpoint of solubility. Comb polymers are particularly preferred. The isoelectric point of the polymer is preferably pH 6 or less.

  Various methods can be used for producing the comb polymer, and it is desirable to use a monomer capable of introducing a side chain having a molecular weight of 200 or more into the comb part (side chain). In particular, it is preferable to use a polyoxyalkylene group-containing ethylenically unsaturated monomer such as ethylene oxide or propylene oxide. As the polyoxyalkylene group-containing ethylenically unsaturated monomer, those having a polyoxyalkylene group represented by the following general formula are particularly preferable.

-(EO) _k- (PO) _m- (TO) _n- R
In the above formula, E represents an ethylene group, P represents a propylene group, T represents a butylene group, and R represents a substituent. Examples of the butylene group include a tetramethylene group and an i-butylene group. k represents an integer of 1 to 300, m represents an integer of 0 to 60, and n represents an integer of 0 to 40. Preferably, k is 1 to 200, m is 0 to 30, and n is 0 to 20. However, k + m + n ≧ 2.

  The polyoxyalkylene group-containing ethylenically unsaturated monomer may be used alone or in combination of two or more.

  The substituent represented by R represents an alkyl group, an aryl group, a heterocyclic group, and the like. As the alkyl group, methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl, and the like. As the aryl group, Groups such as phenyl and naphthyl, and examples of the heterocyclic group include groups such as thienyl and pyridyl. These groups are further halogen atoms, alkoxy groups (methoxy, ethoxy, butoxy, etc.), alkylthio groups (methylthio, butylthio, etc.), acyl groups (acetyl, benzoyl, etc.), alkanamide groups (acetamide, propionamide, etc.), It may be further substituted with an arylamide group (such as benzoylamide). These substituents may be further substituted with these groups.

  The polyoxyalkylene group represented by the preceding formula can be introduced into the polymer by using an ethylenically unsaturated monomer having these polyoxyalkylene groups. Examples of ethylenically unsaturated monomers having these groups include (polyoxyalkylene) acrylates and methacrylates, and (polyoxyalkylene) acrylates and methacrylates are commercially available hydroxy poly (oxyalkylene) materials such as trade names. “Pluronic” (Pluronic: manufactured by Asahi Denka Kogyo Co., Ltd.), Adeka polyether (manufactured by Asahi Denka Kogyo Co., Ltd.), Carbowax (Carbowax: manufactured by Glico Products), Triton (Toriton: manufactured by Rohm and Haas) and P . E. What is sold as G (Daiichi Kogyo Seiyaku Co., Ltd.) can be manufactured by reacting with acrylic acid, methacrylic acid, acrylic chloride, methacrylic chloride, or acrylic acid anhydride by a known method. Separately, poly (oxyalkylene) diacrylate produced by a known method can also be used.

  Moreover, as a monomer of a commercial item, it is Blemmer PE-90, Blemmer PE-200, Blemmer PE-350, Blemmer AE-90, Blemmer AE-200 as a hydroxyl group terminal polyalkylene glycol mono (meth) acrylate made by NOF Corporation. , Blemmer AE-400, Blemmer PP-1000, Blemmer PP-500, Blemmer PP-800, Blemmer AP-150, Blemmer AP-400, Blemmer AP-550, Blemmer AP-800, Blemmer 50PEP-300, Blemmer 70PEP-350B Blemmer AEP series, Blemmer 55PET-400, Blemmer 30PET-800, Blemmer 55PET-800, Blemmer AET series, Blemmer 30PPT-800, Blenmer Over 50PPT-800, Blemmer 70PPT-800, Blemmer APT series, Brenmer 10PPB-500B, and the like Brenmer 10APB-500B. Similarly, Blemmer PME-100, Blemmer PME-200, Blemmer PME-400, Blemmer PME-1000, Blemmer PME-4000, Blemmer AME-400, Blemmer as alkyl-terminated polyalkylene glycol mono (meth) acrylates manufactured by NOF Corporation. 50POEP-800B, Blemmer 50AOEP-800B, Blemmer PLE-200, Blemmer ALE-200, Blemmer ALE-800, Blemmer PSE-400, Blemmer PSE-1300, Blemmer ASE series, Blemmer PKEP series, Blemmer AKEP series, Blemmer AE-300 , Blemmer ANE-1300, Blemmer PNEP series, Blemmer PNPE series, Blemmer 43ANEP- 00, Bremer 70ANEP-550, etc., Kyoeisha Chemical Co., Ltd. light ester MC, light ester 130MA, light ester 041MA, light acrylate BO-A, light acrylate EC-A, light acrylate MTG-A, light acrylate 130A, light Examples include acrylate DPM-A, light acrylate P-200A, light acrylate NP-4EA, and light acrylate NP-8EA.

  As the synthetic polymer according to the present invention, a graft polymer using a so-called macromer can also be used. For example, it is described in “New Polymer Experimental Studies 2, Synthesis and Reaction of Polymers”, edited by the Society of Polymer Science, Kyoritsu Shuppansha, 1995. It is also described in detail in “Yamashita Yuya:“ Chemical Monomer Chemistry and Industry ”, IPC, 1989. Among the macromers, the useful weight average molecular weight is in the range of 10,000 to 200,000, the preferred range is 10,000 to 150,000, and the particularly preferred range is 10,000 to 120,000. If the molecular weight is less than 10,000, the effect cannot be exhibited, and if it is more than 200,000, the polymerizability with the comonomer forming the main chain is deteriorated. Specifically, AA-6, AS-6S, AN-6S, etc. manufactured by Toagosei Co., Ltd. can be used.

  Needless to say, the present invention is not limited to the above specific examples. The polyoxyalkylene group-containing ethylenically unsaturated monomer may be used alone or in combination of two or more.

  Other monomers specifically reacted with the above monomers include acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, allyl esters, allyloxyethanols, vinyl ethers, vinyl esters, itaconic acid Examples thereof include dialkyl, dialkyl esters of fumaric acid or monoalkyl esters, crotonic acid, itaconic acid, acrylonitrile, methacrylonitrile, maleilonitrile, styrene and the like. Specific examples of the compound include the following.

Acrylic acid esters: methyl acrylate, ethyl acrylate, propyl acrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate, trimethylolpropane monoacrylate, benzyl acrylate, methoxybenzyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, etc.
Methacrylic acid esters: methyl methacrylate, ethyl methacrylate, propyl methacrylate, chloroethyl methacrylate, 2-hydroxyethyl methacrylate, trimethylolpropane monomethacrylate, benzyl methacrylate, methoxybenzyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, etc.
Acrylamides: acrylamide, N-alkylacrylamide (alkyl groups having 1 to 3 carbon atoms, methyl, ethyl, propyl), N, N-dialkylacrylamide, N-hydroxyethyl-N-methylacrylamide, N-2- Acetamidoethyl-N-acetylacrylamide and the like. In addition, as alkyloxyacrylamide, methoxymethylacrylamide, butoxymethylacrylamide, etc.
Methacrylamides: methacrylamide, N-alkylmethacrylamide, N-hydroxyethyl-N-methylmethacrylamide, N-2-acetamidoethyl-N-acetylmethacrylamide, methoxymethylmethacrylamide, butoxymethylmethacrylamide, etc.
Allyl compounds: allyl esters (allyl acetate, allyl caproate, allyl caprylate, allyl laurate, allyl palmitate, allyl stearate, allyl benzoate, allyl acetoacetate, allyl lactate, etc.), allyloxyethanol, etc.
Vinyl ethers: alkyl vinyl ethers (hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, ethyl hexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether, hydroxyethyl Vinyl ether, diethylene glycol vinyl ether, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, butylaminoethyl vinyl ether, benzyl vinyl ether, tetrahydrofurfuryl vinyl ether, etc.),
Vinyl esters: vinyl butyrate, vinyl-i-butyrate, vinyl trimethyl acetate, vinyl diethyl acetate, vinyl valate, vinyl caproate, vinyl chloroacetate, vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl lactate, Vinyl-β-phenylbutyrate, vinylcyclohexylcarboxylate, etc.
Dialkyl itaconates: dimethyl itaconate, diethyl itaconate, dibutyl itaconate, etc. Dialkyl esters or monoalkyl esters of fumaric acid: dibutyl fumarate, etc., crotonic acid, itaconic acid, acrylonitrile, methacrylonitrile, maleilonitrile, styrene, etc.

  When introducing an amide group, a linear or branched alkyl group having 4 to 22 carbon atoms, an aromatic group, or a heterocyclic group having 5 or more members, among these monomers or other monomers, these functional groups A monomer containing can be selected. For example, 1-vinylimidazole or a derivative thereof can be used to introduce a heterocyclic group having 5 or more members. Furthermore, an isocyanate or epoxy group is previously introduced into the polymer, and these are reacted with an alcohol or amine containing a linear or branched alkyl group, an aromatic group, or a 5- or more-membered heterocyclic group. Thus, various functional groups may be introduced into the polymer. In order to introduce isocyanate or epoxy, Karenz MOI (manufactured by Showa Denko) or Bremer G (manufactured by Nippon Oil & Fats Co., Ltd.) can be used. It is also preferable to introduce a urethane bond.

  As the polymerization initiator, an azo polymer polymerization initiator or an organic peroxide can be used. Examples of the azo polymer polymerization initiator include ABN-R (2,2′-azobisisobutyronitrile) and ABN-V (2,2′-azobis (2,4-dimethylvalero) manufactured by Nippon Hydrazine Kogyo Co., Ltd. Nitrile)), ABN-E (2,2'-azobis (2-methylbutyronitrile)) and the like. Organic peroxides include bezoyl peroxide, dimethyl ethyl ketone peroxide, lauryl peroxide, pertetra A, perhexa HC, perhexa TMH, perhexa C, perhexa V, perhexa 22, perhexa MC, perbutyl H manufactured by NOF Corporation. , Parkmill H, Parkmill P, Permenter H, Perocta H, Perbutyl C, Perbutyl D, Perhexyl D, Parroyl IB, Parroyl 355, Parroyl L, Parroyl S, Parroyl SA, Nyper BW, Nyper BMT-K40, Nyper BMT-T40, Niper BMT-M, Parroyl IPP, Parroyl NPP, Parroyl TCP, Parroyl EEP, Parroyl MBP, Parroyl OPP, Parroyl SBP, Park Mill ND, Parocta ND, Percyclo D, perhexyl ND, perbutyl ND, perhexyl PV, perhexa 250, perocta O, perhexyl O, perbutyl O, perbutyl IB, perbutyl L, perbutyl 355, perhexyl I, perbutyl I, perbutyl E, perhexa 25Z, perhexa 25MT, perbutyl A, Examples include perhexyl Z, perbutyl ZT, and perbutyl Z.

  Moreover, as a polymerization inhibitor, although a quinone type inhibitor is used, hydroquinone and p-methoxyphenol are mentioned. Seiko Chemical's phenothiazine, methoquinone, non-flex alba, MH (methyl hydroquinone), TBH (t-butyl hydroquinone), PBQ (p-benzoquinone), tolquinone, TBQ (t-butyl-p-benzoquinone), 2,5 And diphenyl-p-benzoquinone.

  The isoelectric point of the polymer according to the present invention is preferably pH 6 or less. If a polymer having a high isoelectric point is used, as will be described later, when the silver halide grains are desalted by the aggregation precipitation method, the decomposition of the silver halide grains is promoted and the photographic performance is adversely affected. . Further, when silver halide fine particles are dispersed in a solvent, it is difficult to disperse unless the pH is raised, which is not preferable from the viewpoint of fogging. Examples of the measurement of the isoelectric point of the polymer include an isoelectric focusing method and a method of measuring the pH after passing a 1% aqueous solution through a mixed bed column of a cation and an anion exchange resin.

  Various acidic groups can be introduced to lower the isoelectric point of the polymer. Examples include carboxylic acid and sulfonic acid groups. For the introduction of carboxylic acid, in addition to using monomers of acrylic acid and methacrylic acid, a polymer containing methyl methacrylate or the like can be obtained by partial hydrolysis. In addition to using styrenesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid as a monomer, the sulfonic acid group can be introduced after the preparation of the polymer by various sulfation techniques. In particular, when a carboxylic acid is used, the solubility in a solvent is relatively high in an unneutralized state, and the property can be changed to water-soluble by neutralization or semi-neutralization, which is particularly preferable. Neutralization can also be performed with sodium or potassium salts, and organic salts such as ammonia, monoethanolamine, diethanolamine, and triethanolamine may be used. Imidazoles, triazoles, and amidoamines can also be used.

  The polymerization can be carried out in the presence or absence of a solvent, but is preferably in the presence of a solvent from the viewpoint of workability. Preferred solvents include alcohols such as ethanol, i-propanol, butanol, i-butanol, and t-butanol; ketones such as acetone, methyl ethyl ketone, methyl-i-butyl ketone, and methyl amyl ketone; methyl acetate, ethyl acetate , Esters such as butyl acetate, methyl lactate, ethyl lactate, butyl lactate; methyl 2-oxypropionate, ethyl 2-oxypropionate, propyl 2-oxypropionate, butyl 2-oxypropionate, 2-methoxypropionic acid Monocarboxylic acid esters such as methyl, ethyl 2-methoxypropionate, propyl 2-methoxypropionate and butyl 2-methoxypropionate; polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone; methyl cellosolve; Ethers such as losolve, butyl cellosolve, butyl carbitol, ethyl cellosolve acetate; propylene glycols such as propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate and esters thereof Halogen solvents such as 1,1,1-trichloroethane and chloroform; ethers such as tetrahydrofuran and dioxane; aromatics such as benzene, toluene and xylene; and further fluorination such as perfluorooctane and perfluorotributylamine Inert liquids.

  Depending on the polymerizability of each monomer, a dropping polymerization method in which a monomer and an initiator are added dropwise to a reaction vessel is also effective for obtaining a polymer having a uniform composition. By removing by column filtration, reprecipitation purification, solvent extraction, etc., unreacted monomers can be removed. Alternatively, low-boiling unreacted monomers can be removed by stripping.

  In the present invention, examples of particularly preferable polymers include copolymers having the following monomers as constituent elements. That is, NIPAM (N-i-propyl acrylamide) / PSE (stearoxy polyethylene glycol monomethacrylate) -400, DAAM (diacetone acrylamide) / PSE-400, DAAM / NIPAM / PSE-400, DAAM / NIPAM / PME (methoxy) Polyethylene glycol monomethacrylate) / PSE, DAAM / AAm (acrylamide) / PME / PSE-400, DAAM / ACMO (acryloyl morpholine) / PME / PSE-400, DAAM / HEAA (hydroxyethyl acrylamide) / PME / PSE- 400 etc. can be mentioned.

  The amide group possessed by DAAM or NIPAM and the carboxyl group in the natural polymer are easily hydrogenated to form a complex. In addition, the alkyl chain possessed by PSE increases the affinity with an organic solvent, facilitates precipitation separation in an aqueous solution, and facilitates dispersion in an organic solvent.

[Binder resin]
In the photothermographic material, the photosensitive layer (image forming layer) and the non-photosensitive layer can contain a binder resin (hereinafter also abbreviated as a binder) for various purposes.

  The binder resin contained in the photosensitive layer can carry silver salt, silver halide grains, a reducing agent, and other components, and the binder used preferably is transparent or translucent, generally colorless, Examples thereof include polymers, synthetic polymers and copolymers, and other media for forming a film, for example, those described in paragraph “0069” of JP-A No. 2001-330918. Among these, methacrylic acid alkyl esters, methacrylic acid aromatic esters, styrenes and the like are particularly preferred examples. Among such polymer compounds, a polymer compound having an acetal group is preferably used.

  Even a high molecular compound having an acetal group is more preferably a polyvinyl acetal having an acetoacetal structure, for example, U.S. Pat. Nos. 2,358,836, 3,003,879, 2,828,204, UK The polyvinyl acetal shown by patent 771,155 etc. can be mentioned. Preferred binders for the present invention are polyvinyl acetals, particularly preferably polyvinyl butyral.

  Here, the polymerization degree of the binder resin will be described. In the present invention, in order to uniformly support silver halide grains, it is required that the organic polymer that is a dispersant for the silver halide grains has an affinity. For this reason, it is preferable that it is a polymer with a low degree of polymerization. In the case of preparing a coating film by coating a photosensitive emulsion, the emulsion preferably has a certain viscosity in order to obtain good coating properties. If the viscosity of the coating solution is too high, it will flow, and if it is too low, the solution will not spread sufficiently, making it difficult to apply uniformly, and the coating properties will not be sufficient. From the above, the polymerization degree of the binder resin of the photosensitive layer according to the present invention is preferably a mixture of a binder having a polymerization degree of 600 to 3,000 and a binder having a polymerization degree of 100 to 400, and further having a polymerization degree of 600 to 3,000. It is desirable to mix two or more binders.

  Next, the glass transition temperature (Tg) of the binder resin will be described. The Tg of the binder resin is a guideline for the thermal phase transition temperature inside each layer. If the Tg is too low, it will promote changes in photographic performance due to diffusion of the material during storage and changes in density after thermal development. Therefore, it is not preferable. On the other hand, if the Tg is too high, the resin fluidity cannot be optimized at a high temperature such as a drying temperature or a heat development temperature. This is not preferable because the drying rate of the coating solution solvent is reduced during drying, and the diffusion rate of a material necessary for image formation is reduced during development. As mentioned above, it is preferable that Tg of the binder resin of the photosensitive layer concerning this invention is 65-95 degreeC. By optimizing Tg, it is preferable in that a low fog density and a high maximum density can be obtained in image formation.

  Further, for non-photosensitive layers (photosensitive layers) such as overcoat layers and undercoat layers, particularly protective layers and backcoat layers, cellulose esters which are polymers having a higher softening temperature, particularly triacetyl cellulose and cellulose acetate. Polymers such as butyrate are preferred. If necessary, two or more binder resins may be used in combination as described above.

These binder resins are used in an effective range to function as a binder for fixing elements of each layer. The effective range can be easily determined by one skilled in the art. For example, as an index for holding at least an aliphatic carboxylic acid silver salt in the photosensitive layer, the ratio of the binder to the aliphatic carboxylic acid silver salt is preferably 15: 1 to 1: 2 (mass ratio), particularly 8 : The range of 1-1: 1 is preferable. That is, it is preferable that the binder amount of the photosensitive layer is a 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased, and may not be used. On the other hand, if it is larger than 6 g / m ² , the reactivity with other components such as silver halide and fatty acid silver is lowered, and the necessary maximum concentration cannot be obtained.

[Crosslinking agent]
The photosensitive layer may contain a cross-linking agent that can link the binders together by bridging bonds. By using a crosslinking agent for the binder, it is known that filming is improved and development unevenness is reduced, but there is also an effect of suppressing fogging during storage and suppressing generation of printout silver after development. is there.

  As the crosslinking agent used, various crosslinking agents conventionally used for ordinary photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based compounds described in JP-A No. 50-96216 are used. Sulfonic acid ester-based, acryloyl-based, carbodiimide-based, and silane compound-based cross-linking agents are used, and the following isocyanate-based, silane compound-based, epoxy-based compounds, and acid anhydrides are preferable.

  Isocyanate-based crosslinking agents are isocyanates having at least two isocyanate groups and adducts thereof (adducts), specifically, aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, and benzene diisocyanates. , Naphthalene diisocyanates, biphenyl diisocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates and diisocyanates with di- or trivalent polyalcohols Examples include adducts. As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used. In addition, the adduct of isocyanate and polyalcohol has particularly high ability to improve interlayer adhesion and prevent layer peeling, image shift and bubble generation.

  Such an isocyanate may be contained in any part of the photothermographic material. For example, the photosensitivity of the support in the support (especially when the support is paper, it can be included in the size composition), photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc. It can be added to any layer on the layer side, and can be added to one or more of these layers.

  As usable thioisocyanate-based crosslinking agents, compounds having a thioisocyanate structure corresponding to the above-mentioned isocyanates are also useful.

  The amount of the crosslinking agent used is usually in the range of 0.001 to 2 mol, preferably 0.005 to 0.5 mol, with respect to 1 mol of silver.

  The isocyanate compound and thioisocyanate compound that can be contained in the present invention are preferably compounds that function as the above-mentioned crosslinking agent, but a good result can be obtained even if the compound has only one functional group.

  Examples of the silane compound include compounds represented by general formulas (1) to (3) disclosed in JP-A No. 2001-264930.

  The epoxy compound that can be used as a crosslinking agent is not particularly limited as long as it has one or more epoxy groups and the number of epoxy groups, molecular weight, and the like. The epoxy group is preferably contained in the molecule as a glycidyl group via an ether bond or an imino bond. Moreover, any of a monomer, an oligomer, a polymer, etc. may be sufficient as an epoxy compound, and the number of the epoxy groups which exist in a molecule | numerator is about 1-10 normally, Preferably it is 2-4. When the epoxy compound is a polymer, it may be either a homopolymer or a copolymer, and the number average molecular weight (Mn) thereof is particularly preferably in the range of about 2,000 to 20,000.

In addition, as the crosslinking agent used in the present invention, any crosslinking agent that can react with a hydroxyl group or a carboxyl group can be preferably used. Examples thereof include an acid anhydride, an oxazoline compound, and a carbodiimide compound. A crosslinking agent may use only 1 type or may use 2 or more types together. The addition amount is not particularly limited, but is preferably in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / m ² , more preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / m ² . It is. Moreover, it is preferable that it is 0.5-200 mass parts with respect to 100 mass parts of binders of the component layer contained, 2-100 mass parts is more preferable, Furthermore, 3-50 mass parts is especially preferable.

  This epoxy compound or acid anhydride can be added to any layer on the photosensitive layer side of the support such as the photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc. It can be added to one layer or two or more layers. When added to the photosensitive layer, if accompanied by the progress of the crosslinking reaction and a decrease in developability, adding more to the layer closer to the support than the photosensitive layer, without loss of developability, with film (adhesiveness) ), Development unevenness can be improved.

  The cross-linking agent used in the present invention may be added in a state of being premixed in the binder solution, may be added at the end of the preparation process of the coating solution, or may be added immediately before coating.

  The photosensitive emulsion contained in the photosensitive layer comprises silver halide fine particles in which the hydrophilic natural polymer is dispersed as a protective colloid and non-photosensitive aliphatic carboxylic acid silver salt particles.

[Photosensitive silver halide]
The photosensitive silver halide is inherently capable of absorbing light as an intrinsic property of silver halide crystals, or capable of absorbing visible light to infrared light by an artificial physicochemical method, and ultraviolet light. Halogen treated and manufactured so that physicochemical changes can occur in the silver halide crystal and / or crystal surface when light in any region within the light wavelength range of the light region to the infrared light region is absorbed. Refers to silver halide crystal grains.

  The silver halide according to the present invention can be prepared as a silver halide grain emulsion (also referred to as a silver halide emulsion) using a known method. That is, any of acid method, neutral method, ammonia method, etc. may be used, and as a method of reacting soluble silver salt and soluble halogen salt, any one of one-side mixing method, simultaneous mixing method, combination thereof, etc. may be used. Of these methods, the so-called controlled double jet method, in which silver halide grains are prepared while controlling the formation conditions, is preferred.

  Usually, silver halide seed grains are divided into two stages: grain nucleation and grain growth, and these may be performed continuously at once, or the formation of nuclei (seed grains) and grain growth are separated. It is also possible to do this. A controlled double jet method in which particle formation is controlled by controlling the pAg, pH, etc., which are particle formation conditions, is preferable because the particle shape and size can be controlled. For example, when performing a method in which nucleation and grain growth are separated, first, an aqueous silver salt solution and an aqueous halide solution are uniformly and rapidly mixed in an aqueous gelatin solution, and after nucleation (nucleation process), control is performed. Silver halide grains are prepared by a grain growth step in which grains are grown while supplying a silver salt aqueous solution and a halide aqueous solution under pAg, pH, and the like. After the formation of grains, the desired salt halide emulsion can be obtained by removing unnecessary salts by a known desalting method such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. Can do.

  The particle size distribution of the silver halide grains according to the present invention is preferably monodispersed. The monodispersion mentioned here means that the coefficient of variation of the particle diameter obtained by the following formula is 30% or less. Preferably it is 20% or less, More preferably, it is 15% or less.

Coefficient of variation of particle size (%) = (standard deviation of particle size / average value of particle size) × 100
Examples of the shape of the silver halide grains include cubes, octahedrons, tetrahedron grains, tabular grains, spherical grains, rod-like grains, and potato grains. Among these, cubes, octahedrons, 14 Planar and tabular silver halide grains are preferred.

  The average aspect ratio when using tabular silver halide grains is preferably 1.5 to 100, more preferably 2 to 50. These are described in US Pat. Nos. 5,264,337, 5,314,798, and 5,320,958, and the desired tabular grains can be easily obtained. Further, grains having rounded corners of silver halide grains can be preferably used.

  The crystal habit on the outer surface of the silver halide grain is not particularly limited, but when a sensitizing dye having crystal habit (plane) selectivity is used in the adsorption reaction of the sensitizing dye on the surface of the silver halide grain. It is preferable to use silver halide grains having a relatively high proportion of crystal habits adapted to the selectivity. For example, when using a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100], the proportion of the [100] face on the outer surface of the silver halide grain is preferably high, and this ratio is 50 % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani, J .; ImagingSci. 29, 165 (1985).

  The silver halide grains used in the present invention preferably use a compound represented by the following general formula at the time of grain formation.

YO (CH ₂ CH ₂ O) _m (CH (CH ₃ ) CH ₂ O) _p (CH ₂ CH ₂ O) _n Y
In the formula, Y represents a hydrogen atom, —SO ₃ M, or —CO—B—COOM, and M represents an ammonium group substituted with a hydrogen atom, an alkali metal atom, an ammonium group, or an alkyl group having 5 or less carbon atoms. And B represents a chain or cyclic group forming an organic dibasic acid. m and n each represents 0 to 50, and p represents 1 to 100.

  The polyethylene oxide compound represented by the above general formula is a step of producing a gelatin aqueous solution when producing a normal silver halide photographic light-sensitive material, a step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved, such as a step of coating an emulsion on a support. This is described in JP-A-44-9497. The polyethylene oxide compound also functions as an antifoaming agent during nucleation. The compound represented by the above general formula is preferably used at 1% by mass or less, more preferably 0.01 to 0.1% by mass with respect to silver.

  The polyethylene oxide compound only needs to be present at the time of nucleation, and is preferably added in advance to the dispersion medium before nucleation, but it may be added during nucleation or a silver salt used at the time of nucleation. You may add and use for aqueous solution or halide aqueous solution. Preferably, it is used by adding 0.01 to 2.0% by mass to the aqueous halide solution or both aqueous solutions. Also, the compound is preferably present for at least 50% of the nucleation step, more preferably 70% or more. The polyethylene oxide compound may be added as a powder or dissolved in a solvent such as methanol.

  The temperature at the time of nucleation is usually 5 to 60 ° C., preferably 15 to 50 ° C. Even if the temperature is constant, the temperature rise pattern (the temperature at the start of nucleation is 25 ° C. It is preferable to control the temperature within the above temperature range even when the temperature is gradually increased and the temperature at the end of nucleation is 40 ° C.) and vice versa.

[Non-photosensitive aliphatic carboxylic acid silver salt]
The non-photosensitive aliphatic carboxylic acid silver salt used in the present invention is relatively stable to light, but is heated to 80 ° C. or higher in the presence of exposed photosensitive silver halide and a reducing agent. In this case, the silver salt functions as a silver ion supplier to form a silver image. The non-photosensitive aliphatic carboxylic acid silver salt may be any aliphatic carboxylic acid salt capable of supplying silver ions that can be reduced by a reducing agent. The aliphatic carboxylic acid silver salt is particularly preferably a silver salt of a long-chain aliphatic carboxylic acid (having 10 to 30, preferably 15 to 28 carbon atoms). Preferred examples of the aliphatic carboxylic acid silver salt include silver lignocerate, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, erucic acid. Including silver and mixtures thereof.

  In the present invention, the aliphatic carboxylic acid silver salt contains 70 to 99.99 mol% of silver behenate. Furthermore, it is preferable to contain 70 to 99 mol% of silver behenate, and more preferably 80 to 90 mol% of silver behenate. In addition, it is preferable to use an aliphatic carboxylic acid silver salt having a silver erucate content of 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0.1 mol% or less.

  The sphere equivalent diameter of the non-photosensitive aliphatic carboxylic acid silver salt particles is preferably 0.05 to 0.5 μm. More preferably, it is 0.10 to 0.5 μm. The particle size distribution is preferably monodisperse. The monodispersity can be expressed by the standard deviation of the average diameter, and the standard deviation of the aliphatic carboxylic acid silver salt particles of the present invention is preferably 0.3 or less. Furthermore, it is preferable that it is 0.2 or less.

  Measurement of particle size and size distribution in this case includes laser diffraction method, centrifugal sedimentation light transmission method, X-ray transmission method, electrical detection band method, shading method, ultrasonic attenuation spectroscopy, method of calculating from image, etc. The particle size distribution can be determined by a known particle size distribution measuring method. Among them, for fine particles, a laser diffraction method and a method of calculating from an image are preferable. Furthermore, the laser diffraction method is preferable, and the aliphatic carboxylic acid silver salt particles dispersed in the liquid can be measured with a commercially available laser diffraction particle size distribution analyzer.

  The aliphatic carboxylic acid silver salt particles are prepared by reacting a solution containing silver ions with an aliphatic metal carboxylate salt solution or suspension. The solution containing silver ions is preferably an aqueous silver nitrate solution, the aliphatic carboxylic acid metal salt solution or suspension is an aqueous solution or an aqueous dispersion, and the addition and mixing are preferably performed simultaneously. Any method such as a method of adding to the liquid surface of the bath or a method of adding to the liquid may be used, but a method of adding and mixing in the transfer means is preferred. Mixing in the transfer means means line mixing, and before the mixture of the solution containing silver ions and the aliphatic metal carboxylic acid alkali metal salt solution or suspension enters the batch storing the mixture containing the reactants. It is performed. As the stirring means in the mixing section, any means such as mechanical stirring such as a homomixer, static mixer, turbulent flow effect or the like may be used, but it is preferable not to use mechanical stirring. In addition, the mixing in the transfer means includes a solution containing silver ions, an alkali metal salt of an aliphatic carboxylic acid salt or a suspension, water, a circulated liquid of a mixed liquid stored in a batch after mixing, and the like. Liquids or suspensions may be mixed.

  In the present invention, the concentration of the aqueous silver nitrate solution is preferably 1 to 15% by mass, and the concentration of the aliphatic carboxylic acid metal salt aqueous solution or the aqueous dispersion is preferably in the range of 1 to 5% by mass. In a low concentration range outside the above-mentioned concentration range, productivity is remarkably deteriorated and is not realistic, and in a high concentration range, it is difficult to adjust the particle size and size distribution within the range of the present invention. The mixing molar ratio of silver nitrate to the aliphatic carboxylic acid alkali metal salt is preferably in the range of 0.9 to 1.1, and outside the range, the particle size and size distribution can be adjusted within the range of the present invention. In addition to difficulty, the yield of aliphatic carboxylic acid silver salt is reduced, and the formation of silver oxide that causes fogging is likely to occur.

  The prepared aliphatic carboxylic acid silver salt is preferably washed with water and then dried from the viewpoint of storage stability. Washing with water is performed mainly for the purpose of removing unreacted ions, but it may be performed with an organic solvent in consideration of the subsequent drying step. The washing with water is preferably performed at 50 ° C. or lower. Furthermore, it is preferable to carry out at 30 degrees C or less. When carried out at 50 ° C. or higher, it is difficult to adjust the particle size and size distribution within the scope of the present invention. The drying is preferably performed at a temperature lower than the phase transition temperature of the aliphatic carboxylic acid silver salt. Furthermore, it is preferable to carry out at 50 degrees C or less, and it is preferable to carry out at low temperature as much as possible. Drying above the phase transition temperature makes it difficult to adjust the particle size and size distribution within the scope of the present invention.

  In the present invention, the preparation of the aliphatic carboxylic acid silver salt is preferably performed in the absence of photosensitive silver halide grains. In the preparation in the presence of light-sensitive silver halide, it is difficult to adjust the size and size distribution of the aliphatic carboxylic acid silver salt grains within the scope of the present invention because of compatibility with fogging performance.

The aliphatic carboxylic acid silver salt can be used in a desired amount, but the total silver amount including the silver halide is preferably 0.8 to 1.5 g / m ^2, more preferably 1.0 to 1.3 g / m ^2. The range of is preferable.

[Reducing agent]
In the present invention, it is preferable to use the compound represented by the general formula (1) alone or in combination with another reducing agent having a different chemical structure as a reducing agent for silver ions. The reducing agent used in combination here is also preferably a bisphenol type reducing agent. Examples of the reducing agent that can be used in combination with the compound represented by the general formula (1) include paragraph numbers “0043” to “0045” of JP-A No. 11-65021, page 7, line 34 to page 18, line 12 of European Patent Publication No. EP0803764A1. Paragraph numbers “0124” to “0133” of JP-A-2003-302723, paragraph numbers “0124” to “0127” of JP-A-2003-315554, and paragraph numbers “0042” to “0057” of JP-A-2004-4650. Are listed.

  The compound represented by the general formula (1) is preferably contained in a photosensitive layer containing an organic acid silver salt, but may be contained in an adjacent non-photosensitive layer.

  Hereinafter, the reducing agent represented by the general formula (1) will be described in detail.

In the general formula (1), R ₁ represents a hydrogen atom or a substituent. Examples of the substituent include an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, a halogen atom, and a cyano group. Preferably, they are a hydrogen atom, an alkyl group, a cycloalkyl group, or an alkenyl group, More preferably, they are a hydrogen atom or an alkyl group. These substituents may further have a substituent, such as an alkyl group, a cycloalkyl group, a halogenated alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, a halogen atom, Cyano group, hydroxyl group, carboxyl group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, amino group, anilino group, acylamino group , Aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl and arylsulfonylamino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, sulfo group Alkyl and arylsulfinyl groups, alkyl and arylsulfonyl groups, acyl groups, aryloxycarbonyl groups, alkoxycarbonyl groups, carbamoyl groups, aryl and heterocyclic azo groups, imide groups, silyl groups, hydrazino groups, ureido groups, boronic acid groups, Examples thereof include a phosphato group, a sulfato group, and other known substituents.

R ₂ and R ₃ each represent a branched alkyl group having 3 to 8 carbon atoms. As the branched alkyl group, t-butyl group, t-amyl group, i-propyl group, i-butyl group, i-propyl group, 1,1-dimethylbutyl group, 1-methylcyclopentyl group, 1-methylcyclobutyl Groups, 1-methylcyclopropyl group, 1-methylbutyl group, 1,3-dimethylbutyl group, 1-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethyl-1-methylpropyl group, etc. It is done. A t-butyl group, a 1,1-dimethylbutyl group or a t-amyl group is preferable, and a t-amyl group is more preferable. These branched alkyl groups may further have a substituent, and examples of the substituent include a hydroxyl group, a cyano group, a mercapto group, a halogen atom, an amino group, an imide group, a silyl group, and a hydrazino group.

A ₁ and A ₂ each represent a hydroxyl group or a group that can be deprotected to form a hydroxyl group, and is preferably a hydroxyl group. Examples of the group that can be deprotected to form a hydroxyl group include a group that is deprotected by the action of an acid and / or heat to form a hydroxyl group. Specifically, ether groups (methoxy, t-butoxy, allyloxy, benzyloxy, triphenylmethoxy, trimethylsilyloxy, etc.), hemiacetal groups (tetrahydropyranyloxy, etc.), ester groups (acetyloxy, benzoyloxy, p- Nitrobenzoyloxy, formyloxy, trifluoroacetyloxy, pivaloyloxy, etc.), carbonate groups (ethoxycarbonyloxy, phenoxycarbonyloxy, t-butyloxycarbonyloxy, etc.), sulfonate groups (p-toluenesulfonyloxy, benzenesulfonyloxy, etc.) Carbamoyloxy group (phenylcarbamoyloxy etc.), thiocarbonyloxy group (benzylthiocarbonyloxy etc.), nitrate ester group, sulfenate group (2,4-dinitrobe Zen sulfenyl oxy, etc.). n and m each represents an integer of 3 to 5, preferably 3 or 4, and more preferably 3.

The structures of the exemplified substituents R ₁ , R ₂ , R ₃ , A ₁ and A ₂ are one of the factors that determine the thermal properties and crystallinity of the bisphenol type reducing agent. The melting point, thermal decomposition temperature, and crystallinity of the toner are highly correlated with photographic performance.

  When used in the photothermographic material according to the invention, the melting point is preferably 80 to 250 ° C., and the thermal decomposition temperature is preferably 200 ° C. or higher. In photothermographic materials in which a reducing agent remains in the photosensitive material after development processing, the reducing agent with higher crystallinity suppresses material diffusion during storage. Therefore, it is more preferable that the crystallinity of the reducing agent is higher.

  Although the specific example of a reducing agent represented by General formula (1) below is shown, this invention is not limited to these.

  The reducing agent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form, and may be contained in the photothermographic material.

  In the present invention, U.S. Pat. Nos. 3,589,903, 4,021,249, British Patent 1,486,148, and JP-A-51-51933, JP-A-50-36110, JP-A-50-116033. 52-84727 or JP-B-51-35727, such as 2,2'-dihydroxy-1,1'-binaphthyl, 6,6'-dibromo-2,2'-dihydroxy-1 Bisnaphthols described in U.S. Pat. No. 3,672,904 such as 1,1'-binaphthyl and the like, and further, for example, 4-benzenesulfonamidophenol, 2-benzenesulfonamidophenol, 2,6-dichloro-4-benzenesulfone As described in US Pat. No. 3,801,321 such as amidophenol, 4-benzenesulfonamidonaphthol and the like Sulfonamidophenols or sulfonamide naphthols can also be used as the silver ion reducing agent.

  The amount of the reducing agent used varies depending on the type of the aliphatic carboxylic acid silver salt, the reducing agent, and other additives, but generally 0.05 to 10 mol, preferably 1 mol per mol of the aliphatic carboxylic acid silver salt. 0.1-3 mol is suitable. In the present invention, the reducing agent is added to and mixed with a photosensitive emulsion solution composed of photosensitive silver halide and aliphatic carboxylic acid silver salt grains and a solvent immediately before coating, and the coating reduces the fluctuation in photographic performance due to the stagnation time. It may be preferable.

[Chemical sensitization, spectral sensitization, supersensitization]
The photosensitive silver halide grains can be chemically sensitized. For example, by a method described in JP-A Nos. 2001-249428 and 2001-249426, a compound that releases chalcogen such as sulfur, selenium, and tellurium, and a noble metal compound that releases noble metal ions such as gold ions can be used for photosensitivity. It is possible to form and impart a chemical sensitization center (chemical sensitization nucleus) capable of capturing electrons or holes generated by photoexcitation of the light-sensitive silver halide grains or the spectral sensitizing dye on the grains. In particular, it is preferably chemically sensitized with an organic sensitizer containing a chalcogen atom.

  These organic sensitizers containing chalcogen atoms are preferably compounds having groups capable of adsorbing to silver halide and unstable chalcogen atom sites. These organic sensitizers are disclosed in JP-A-60-150046, JP-A-4-109240, JP-A-11-218874, JP-A-11-218875, JP-A-11-218876, JP-A-11-194447, etc. Organic sensitizers having various structures can be used, and of these, at least one compound having a structure in which a chalcogen atom is bonded to a carbon atom or a phosphorus atom by a double bond Is preferred. In particular, a thiourea derivative having a heterocyclic group and a triphenylphosphine sulfide derivative are preferred. As a method of performing chemical sensitization, techniques according to various chemical sensitization techniques conventionally used in the production of conventional silver halide light-sensitive materials for wet processing can be used (edited by TH James). The Theory of the Photographic Process, 4th edition, McCillan Publishing Co., Ltd., edited by the Japan Photographic Society, "Basics of Photographic Engineering (Silver Salt Photography), Corona, 1979). Especially, silver halide grain emulsion. In the case of performing chemical sensitization in advance and then mixing with non-photosensitive aliphatic carboxylic acid silver salt particles, chemical sensitization can be performed by a conventional method.

The amount of the chalcogen compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, etc., but is 10 ⁻⁸ to 10 ⁻ per mol of silver halide. ² mol is preferred, more preferably 10 ⁻⁷ to 10 ⁻³ mol.

  There are no particular restrictions on the environmental conditions for chemical sensitization, but in the presence of a compound that can eliminate or reduce the size of silver chalcogenide or silver nuclei on the photosensitive silver halide grains. Further, it may be preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom, particularly in the presence of an oxidizing agent capable of oxidizing silver nuclei. The sensitizing conditions in this case are preferably 6 to 11 as pAg, more preferably 7 to 10, pH 4 to 10 is more preferable, 5 to 8 is more preferable, and temperature is 30 ° C. or less. It is preferable to perform sensitization.

  Chemical sensitization using these organic sensitizers is preferably carried out in the presence of a heteroatom-containing compound having adsorptivity to spectral sensitizing dyes or silver halide grains. By performing chemical sensitization in the presence of a compound having adsorptivity to silver halide grains, dispersion of the chemically sensitized central core can be prevented, and high sensitivity and low fog can be achieved. Although the spectral sensitizing dye will be described later, a nitrogen-containing heterocyclic compound described in JP-A-3-24537 is preferable as a heteroatom-containing compound having adsorptivity to silver halide. In the nitrogen-containing heterocyclic compound, examples of the heterocyclic ring include pyrazole, pyrimidine, 1,2,4-triazole, 1,2,3-triazole, 1,3,4-thiadiazole, 1,2,3-thiadiazole, 1 , 2,4-thiadiazole, 1,2,5-thiadiazole, 1,2,3,4-tetrazole, pyridazine, 1,2,3-triazine ring, a ring in which two or three of these rings are bonded, for example, tria Examples include zolotriazole, diazaindene, triazaindene, pentazaindene ring and the like. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, phthalazine, benzimidazole, indazole, benzthiazole ring and the like can also be applied.

  Among these, an azaindene ring is preferable, and an azaindene compound having a hydroxyl group as a substituent, such as a hydroxytriazaindene, tetrahydroxyazaindene, hydroxypentazaindene compound, or the like is more preferable.

  The heterocyclic ring may have a substituent other than the hydroxyl group. Examples of the substituent include an alkyl group, a substituted alkyl group, an alkylthio group, an amino group, a hydroxyamino group, an alkylamino group, a dialkylamino group, an arylamino group, a carboxyl group, an alkoxycarbonyl group, a halogen atom, and a cyano group. You may have.

The addition amount of these heterocyclic compounds varies over a wide range depending on the size, composition and other conditions of the silver halide grains, but the approximate amount is 10 ⁻⁶ to 1 mol per mol of silver halide. And preferably in the range of 10 ⁻⁴ to 10 ⁻¹ mol.

  The photosensitive silver halide can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, a chloroaurate or an organic gold compound can be used as a gold sensitizer. The gold sensitization technique disclosed in JP-A-11-194447 is useful as a reference.

  In addition to the above-described sensitization methods, reduction sensitization methods and the like can also be used, and as a shell-like compound for reduction sensitization, ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, borane compounds A silane compound, a polyamine compound, or the like can be used. Further, reduction sensitization can be performed by ripening the emulsion while maintaining the pH at 7 or higher or the pAg at 8.3 or lower.

  In the present invention, the silver halide grains subjected to chemical sensitization were formed in the absence of the aliphatic carboxylic acid silver salt even though they were formed in the presence of the aliphatic carboxylic acid silver salt. However, both may be mixed.

  When the surface of the photosensitive silver halide grain is chemically sensitized, it is preferable that the effect of the chemical sensitization substantially disappears after the thermal development process. Here, the chemical sensitization effect substantially disappears when the sensitivity of the imaging material obtained by the chemical sensitization technique is 1.1 when the chemical sensitization is not performed after the thermal development process. Say to decrease to less than double. In order to eliminate the chemical sensitization effect in the thermal development process, an oxidant capable of destroying the chemical sensitization center (chemical sensitization nucleus) by an oxidation reaction at the time of thermal development, such as the above-mentioned halogen radical releasing compound, etc. It is necessary to contain an appropriate amount in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the chemical sensitization effect, and the like.

  The photosensitive silver halide is preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. As spectral sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes, and the like can be used. For example, JP-A Nos. 63-159841, 60-140335, 63-231437, 63-259651, 63-304242, 63-15245, U.S. Pat. Nos. 4,639,414, 4 , 740,455, 4,741,966, 4,751,175, and 4,835,096 can be used.

  Useful sensitizing dyes used in the present invention are described in, for example, Research Disclosure (hereinafter abbreviated as RD) 17643IV-A (December 23, 1978), RD18431X (August 1978, 437) or It is described in the cited literature. In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various laser imagers and scanner light sources. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

  Useful cyanine dyes are cyanine dyes having basic nuclei such as thiazoline nucleus, oxazoline nucleus, pyrroline nucleus, pyridine nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus and imidazole nucleus. Useful merocyanine dyes are preferably acidic nuclei such as thiohydantoin nucleus, rhodanine nucleus, oxazolidinedione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus in addition to the basic nuclei described above. Including.

  In the present invention, a sensitizing dye having spectral sensitivity particularly in the infrared can also be used. Examples of infrared spectral sensitizing dyes preferably used include infrared spectral sensitizing dyes disclosed in U.S. Pat. Nos. 4,536,473, 4,515,888, and 4,959,294. It is done.

  In the photothermographic material of the present invention, a sensitizing dye represented by the following general formula (SD1) and a sensitizing dye represented by the following general formula (SD2) as described in JP-A No. 2004-309758 are disclosed. It is preferable to contain at least one selected from the above.

In the formula, Y ₁ and Y ₂ each represent an oxygen atom, a sulfur atom, a selenium atom or a —CH═CH— group, and L _{1 to} L ₉ each represent a methine group. R ¹ and R ² each represents an aliphatic group. R ³ and R ⁴ each represent a lower alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group. W ₁ , W ₂ , W ₃ , and W ₄ are each a hydrogen atom, a substituent, or a nonmetallic atom necessary for bonding between W ₁ and W ₂ , W ₃ and W ₄ to form a condensed ring. Represents a group. Alternatively, R ³ and W ₁ , R ³ and W ₂ , R ⁴ and R ³ , R ⁴ and W ₄ are bonded to each other to represent a group of nonmetallic atoms necessary to form a 5- or 6-membered condensed ring. . X ₁ represents an ion necessary for canceling the charge in the molecule, and k 1 represents the number of ions necessary for canceling the charge in the molecule. m1 represents 0 or 1, and n1 and n2 each represents 0, 1 or 2. However, n1 and n2 are not 0 at the same time.

  The above-mentioned infrared sensitizing dyes are described in, for example, HM Hammer: The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dies and Related Compounds, published by A. Weissberger ed. It can be easily synthesized by the method described.

  These infrared sensitizing dyes may be added at any time after the silver halide is prepared. For example, silver halide grains or silver halides in a so-called solid dispersion state added to a solvent or dispersed in a fine particle form. It can be added to a light-sensitive emulsion containing grains / silver aliphatic carboxylate grains. Similarly to the heteroatom-containing compound having adsorptivity to the silver halide grains, chemical sensitization can be performed after adding and adsorbing to the silver halide grains prior to chemical sensitization. Can prevent the dispersion of the chemical sensitization core and can achieve high sensitivity and low fog.

  The above spectral sensitizing dyes may be used alone, but as described above, it is preferable to use a combination of a plurality of types of spectral sensitizing dyes. Often used for purposes such as supersensitization and expansion or adjustment of the photosensitive wavelength region.

  Emulsions containing photosensitive silver halides and aliphatic carboxylic acid silver salts used in heat-developable photosensitive materials are sensitizing dyes, dyes that themselves do not have spectral sensitizing action, or substances that do not substantially absorb visible light. In addition, a substance that exhibits a supersensitization effect may be included in the emulsion, whereby the silver halide grains may be supersensitized.

  Useful sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in RD17643 (issued in December, 1978), Section J, page 23, or Japanese Patent Publication No. 9-25500. No. 43-4933, JP-A-59-19032, JP-A-59-192242, JP-A-5-341432, and the like, but as a supersensitizer, a heteroaromatic mercapto compound represented by the following is used. Or a mercapto derivative compound is preferable.

Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic ring or condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium, or tellurium atoms. Preferred heteroaromatic rings are preferably benzimidazole, naphthimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzotelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine , Purine, quinoline, or quinazoline. However, other heteroaromatic rings are also included.

  In addition, a mercapto derivative compound which substantially forms the above mercapto compound when contained in a dispersion of an aliphatic carboxylic acid silver salt or a silver halide grain emulsion is also included. In particular, mercapto derivative compounds represented below are preferred examples.

Ar-SS-Ar
In the formula, Ar has the same meaning as in the case of the mercapto compound represented above.

  The heteroaromatic ring is, for example, a halogen atom (chlorine, bromine, iodine), a hydroxyl group, an amino group, a carboxyl group, or an alkyl group (having one or more carbon atoms, preferably having 1 to 4 carbon atoms). And a substituent selected from the group consisting of alkoxy groups (having one or more carbon atoms, preferably 1 to 4 carbon atoms).

  In addition to the above supersensitizers, macrocycles having heteroatoms disclosed in JP-A-2001-330918 can also be used as supersensitizers.

  The supersensitizer is preferably used in an amount of 0.001 to 1.0 mol per mol of silver in the photosensitive layer containing the aliphatic carboxylic acid silver salt and silver halide grains. Most preferably, it is 0.01-0.5 mol per 1 mol of silver.

  In the present invention, it is preferable that spectral sensitization is performed by adsorbing a spectral sensitizing dye on the surface of photosensitive silver halide grains, and that the spectral sensitization effect substantially disappears after the thermal development process. . Here, the spectral sensitization effect substantially disappears when the sensitivity of the imaging material obtained with a sensitizing dye, supersensitizer, etc. is 1 when the spectral sensitization is not performed after the thermal development. It means to decrease to 1 times or less.

  In order to eliminate the spectral sensitization effect in the thermal development process, a spectral sensitizing dye that is easily detached from the silver halide grains by heat is used during thermal development or / and the spectral sensitizing dye is destroyed by an oxidation reaction. It is necessary to contain an appropriate amount of an oxidizing agent that can be formed, for example, the above-mentioned halogen radical releasing compound in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the spectral sensitization effect, and the like.

[Color tone adjuster]
Next, the color tone of an image obtained by thermally developing a photothermographic material will be described.

  Regarding the color tone of an output image for medical diagnosis such as a conventional X-ray photographic film, it is said that a cold tone image tone is easier for a reader to obtain a more accurate diagnostic observation result. Here, the cool image tone means a pure black tone or a bluish black tone of a black image. On the other hand, the warm image tone is said to be a warm black tone with a black image, but in order to allow a more precise quantitative discussion, the International Lighting Commission (CIE) ), Based on the recommended expression.

The terms “more cold” and “more warm” regarding the color tone can be expressed by the hue angle hab at the minimum density Dmin and the optical density D = 1.0. That is, the hue angle hab is expressed by the color coordinates a ^* and b ^* of the color space L ^* a ^* b ^* color space, which is a color space having a perceptually uniform rate recommended by the International Commission on Illumination (CIE) in 1976. Using the following formula.

(Formula) hab = tan-1 (b ^* / a ^* )
As a result of examination by the expression method based on the hue angle, the hue of the photothermographic dry imaging material of the present invention after development is preferably such that the range of the hue angle hab is 180 degrees <hab <270 degrees, more preferably 200 degrees. It has been found that degrees <hab <270 degrees, most preferably 220 degrees <hab <260 degrees. This is disclosed in Japanese Patent Application Laid-Open No. 2002-6463.

Conventionally, the CIE 1976 (L ^* u ^* v ^* ) color space or the (L ^* a ^* b ^* ) color space near the optical density of 1.0 is specified as u ^* , v ^* or a ^* , b ^* . It is known that a diagnostic image having a favorable color tone can be obtained by adjusting the numerical value, and is described in, for example, Japanese Patent Application Laid-Open No. 2000-29164.

However, as a result of further intensive studies on photothermographic materials, the horizontal axis is u ^* or a ^* and the vertical axis is v in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space. ^When plotting u ^* , v ^* or a ^* , b ^* at various photographic densities on a graph with ^* or b ^* and creating a linear regression line, adjust the linear regression line to a specific range By doing so, it has been found that it has a diagnostic ability equivalent to or higher than that of a conventional wet silver salt photosensitive material. A preferable range of conditions is described below.

(1) The optical density of the silver image obtained after heat development processing of the photothermographic material was measured at 0.5, 1.0, 1.5 and the lowest optical density, and CIE 1976 (L ^* u ^* v ^* ) Linear regression line determination coefficient (multiple determination) R2 created by arranging u ^* and v ^* at each optical density in two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^*. Is preferably 0.998 to 1.000. Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (v ^* / u ^* ) is 0.7 to 2.5.

(2) In addition, the optical density of the photothermographic dry imaging material is measured at 0.5, 1.0, 1.5 and the lowest optical density, next to the CIE 1976 (L ^* a ^* b ^* ) color space. The coefficient of determination (multiple determination) R2 of the linear regression line created by arranging a ^* and b ^* at the respective optical densities on two-dimensional coordinates with the axis a ^* and the vertical axis b ^* is 0.998-1 .000 is preferred. Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (b ^* / a ^* ) is 0.7 to 2.5.

An example of a method for creating the above-described linear regression line, that is, a method for measuring u ^* , v ^*, a ^* , and b ^{* in} the CIE 1976 color space will be described next.

A four-stage wedge sample including an unexposed portion and optical densities of 0.5, 1.0, and 1.5 is prepared using a heat development apparatus. Each wedge density portion thus created is measured with a spectrocolorimeter (Minolta: CM-3600d, etc.), and u ^* , v ^* or a ^* , b ^* are calculated. The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 degrees, and the measurement is performed in the transmission measurement mode. Plot u ^* , v ^* or a ^* , b ^* measured on a graph with u ^* or a ^{* on} the horizontal axis and v ^* or b ^{* on the} vertical axis to obtain a linear regression line, and the coefficient of determination (multiple determination) Find R2, intercept and slope.

  Next, a specific method for obtaining a linear regression line having the above characteristics will be described.

  In the present invention, by adjusting the addition amount of a compound or the like directly or indirectly involved in the development reaction process such as a reducing agent (developer), silver halide grains, aliphatic silver carboxylate and the following toning agent. The developed silver shape can be optimized to obtain a preferable color tone. For example, when the developed silver shape is dendritic, it becomes a bluish direction, and when it is a filament shape, it becomes a yellowish direction. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

  Conventionally, phthalazinone or phthalazine and phthalic acids and phthalic anhydrides are generally used as the color toning agent. Examples of suitable toning agents are disclosed in RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, 4,021,249, and the like.

  In addition to such a color tone agent, the color tone can be adjusted using couplers disclosed in JP-A-11-288057, European Patent No. 1,134,611A2, etc., and leuco dyes described in detail below. it can. In particular, a coupler or leuco dye is preferably used for fine adjustment of the color tone.

  As described above, the photothermographic material can also be adjusted in color tone using a leuco dye. The leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds. Any leuco dye that can be oxidized by the body to form a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  Representative leuco dyes suitable for use in the present invention are not particularly limited and include, for example, biphenol leuco dyes, phenol leuco dyes, indoaniline leuco dyes, acrylated azine leuco dyes, phenoxazine leuco dyes, phenodiazine leuco dyes and And phenothiazine leuco dye. US Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4,022 are useful. No. 4,617, No. 4,123,282, No. 4,368,247, No. 4,461,681, and JP-A-50-36110, JP-A-52-206831, JP-A-5-204087, No. 11-231460, JP-A Nos. 2002-169249, 2002-236334, and the like.

  In order to adjust to a predetermined color tone, it is preferable to use leuco dyes of various colors singly or in combination of a plurality of types. In the present invention, the use of a highly active reducing agent changes the color tone (especially yellowishness) depending on the amount and ratio of use, and the use of fine grain silver halide results in a concentration of 2. In order to prevent the image from becoming excessively reddish at a high density portion of 0 or more, it is preferable to use a leuco dye that develops yellow and cyan colors and adjust the amount of use.

  The color density is preferably adjusted appropriately in relation to the color tone of the developed silver itself. In the present invention, color is developed so as to have a reflection optical density of 0.01 to 0.05 or a transmission optical density of 0.005 to 0.50, and the color tone is adjusted so that an image in the above preferred color tone range is obtained. Is preferred. The sum of the maximum densities at the maximum absorption wavelength of the dye image formed by the leuco dye is preferably 0.01 to 0.50, more preferably 0.02 to 0.30, and particularly preferably 0.03 to 0. It is preferable to develop the color so as to have.

(Yellow coloring leuco dye)
As described above, the photothermographic material can also be adjusted in color tone using a leuco dye. In the present invention, a color image forming agent whose absorbance at 360 to 450 nm is increased by oxidation is preferably used as the yellow color-forming leuco dye. These color image forming agents are particularly preferably color image forming agents represented by the following general formula (YA).

In the formula, R ₁₁ represents a substituted or unsubstituted alkyl group, R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, and R ₁₁ and R ₁₂ are 2-hydroxyphenylmethyl groups. There is nothing. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on the benzene ring.

R ₁₁ represents a substituted or unsubstituted alkyl group. When R ₁₂ is a substituent other than a hydrogen atom, R ₁₁ represents an alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms and may have a substituent. Specifically, methyl, ethyl, butyl, octyl, i-propyl, t-butyl, t-octyl, t-pentyl, sec-butyl, cyclohexyl, 1-methyl-cyclohexyl and the like are preferred, and steric rather than i-propyl. Is preferably a large group (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl, etc.), and among them, secondary or tertiary An alkyl group is preferable, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferable. Examples of the substituent that R ₁₁ may have include a halogen atom, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamido group, an acyloxy group, an oxycarbonyl group, and a carbamoyl group. , Sulfamoyl group, sulfonyl group, phosphoryl group and the like.

R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, and the acylamino group is preferably an acylamino group having 1 to 30 carbon atoms. Among these, the description of the alkyl group is the same as R ₁₁ described above. The acylamino group may be unsubstituted or substituted, and specific examples include an acetylamino group, an alkoxyacetylamino group, and an aryloxyacetylamino group. R ₁₂ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, and t-butyl. R ₁₁ and R ₁₂ are not 2-hydroxyphenylmethyl groups.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, and the description of the alkyl group is the same as that for R ₁₁ . R ₁₃ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, t-butyl and the like. Further, it is preferable either R _12, R ₁₃ is a hydrogen atom.

R ₁₄ represents a group capable of substituting on the benzene ring, and is, for example, the same group as described for the substituent R ⁴ in formula (RD1). R ₁₄ is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or an oxycarbonyl group having 2 to 30 carbon atoms, and more preferably an alkyl group having 1 to 24 carbon atoms. Examples of the substituent of the alkyl group include an aryl group, an amino group, an alkoxy group, an oxycarbonyl group, an acylamino group, an acyloxy group, an imide group, and a ureido group, and more preferable examples include an aryl group, an amino group, an oxycarbonyl group, and an alkoxy group. preferable. These alkyl group substituents may be further substituted with these substituents.

  Next, the bisphenol compound represented by the following general formula (YB), which is particularly preferably used in the present invention, among the compounds represented by the general formula (YA) will be described.

In the formula, Z represents —S— or —C (R ₂₁ ) (R ₂₁ ′) —, and R ₂₁ and R ₂₁ ′ each represents a hydrogen atom or a substituent. Examples of the substituent represented by R ₂₁ and R ₂₁ ′ include the same groups as the substituents exemplified in the description of R ^{1 in} the general formula (RD1). R ₂₁ and R ₂₁ ′ are preferably a hydrogen atom or an alkyl group.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ each represent a substituent, and examples of the substituent include the same groups as those described for R ² and R ³ in the general formula (RD1).

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, but an alkyl group is more preferable. Examples of the substituent on the alkyl group include the same groups as those described in the description of the substituent in the general formula (RD1). R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are more preferably tertiary alkyl groups such as t-butyl, t-pentyl, t-octyl and 1-methyl-cyclohexyl.

R ₂₄ and R ₂₄ ′ each represent a hydrogen atom or a substituent, and examples of the substituent include the same groups as the substituents described in the description of R ⁴ in formula (RD1).

  Examples of the compounds represented by the general formulas (YA) and (YB) include compounds II-1 to II-40 described in paragraphs “0032” to “0038” of JP-A No. 2002-169249, European Patents 1 and 211. , 093, and the compounds ITS-1 to ITS-12 described in paragraph “0026”.

  Although the specific example of the bisphenol compound represented by general formula (YA) and (YB) below is shown, this invention is not limited to these.

  The addition amount of the compound of the general formula (YA) (including the hindered phenol compound and the compound of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0.0005, per mol of silver. It is -0.01 mol, More preferably, it is 0.001-0.008 mol.

  Moreover, the addition ratio of the yellow color-forming leuco dye to the sum of the reducing agents is preferably 0.001 to 0.2, more preferably 0.005 to 0.1 in terms of molar ratio.

(Cyan coloring leuco dye)
The photothermographic material of the present invention can also be adjusted in color tone by using a cyan color-forming leuco dye in addition to the yellow color-forming leuco dye. The cyan chromophoric leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds. Any leuco dye that forms a pigment by oxidation with an oxidant of the agent can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  What is preferably used as the cyan color-forming leuco dye is a color image forming agent that increases its absorbance at 600 to 700 nm when oxidized. Examples of these compounds include compounds of general formulas (I) to (IV) disclosed in JP-A-59-206831 (particularly compounds having λmax in the range of 600 to 700 nm) and JP-A-5-204087 (specific examples). Are described in paragraphs “0032” to “0037” (1) to (18)) and compounds of general formulas 4 to 7 in JP-A No. 11-231460 (specifically, in paragraph “0105”). No. 1 to No. 79 compounds).

  The cyan color-forming leuco dye preferably used in the present invention is a compound represented by the following general formula (CLA) or general formula (CLB-I). The color image forming agent represented by the general formula (CLB-I) is particularly preferable in that it has high color development efficiency, can be adjusted in color even when added in a small amount, and is excellent in image storage stability.

  Hereinafter, the compounds of general formula (CLA) and general formula (CLB-I) will be described in detail.

In the formula, R ₃₁ and R ₃₂ represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, —NHCOR ₃₀ group (R ₃₀ represents an alkyl group, an aryl group, or a heterocyclic group). Or R ₃₁ and R ₃₂ are a group that forms an aliphatic hydrocarbon ring, an aromatic hydrocarbon ring, or a heterocyclic ring by being linked to each other. A ₃ represents a —NHCO— group, a —CONH— group or a —NHCONH— group, and R ₃₃ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group.

-A ₃ R ₃₃ may be a hydrogen atom. For example, the —A ₃ R ₃₃ moiety represents a hydrogen atom, or A ₃ represents a —NHCO— group, —CONH— group, or —NHCONH— group, and R ₃₃ represents a substituted or unsubstituted alkyl group, aryl group, or Represents a heterocyclic group.

W ₃ represents a hydrogen atom or —CONHR ₃₅ group, —COR ₃₅ group or —COOR ₃₅ group (R ₃₅ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group), and R ₃₄ represents a hydrogen atom. Represents a halogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkoxy group, a carbamoyl group or a nitrile group. R ₃₆ represents —CONHR ₃₇ group, —COR ₃₇ group or —COOR ₃₇ group (R ₃₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group) X ₃ represents a substituted or unsubstituted group, An aryl group or a heterocyclic group is represented.

In the general formula (CLA), examples of the halogen atom represented by R ₃₁ and R ₃₂ include a fluorine atom, a bromine atom, and a chlorine atom, and the alkyl group is an alkyl group having up to 20 carbon atoms (methyl Group, ethyl, butyl, dodecyl and the like, and the alkenyl group includes alkenyl groups having up to 20 carbon atoms (vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl- 3-propenyl, 3-pentenyl, 1-methyl-3-butenyl and the like, and the alkoxy group includes an alkoxy group having up to 20 carbon atoms (methoxy, ethoxy and the like). Examples of the alkyl group represented by R ₃₀ in the —NHCOR ₃₀ group include alkyl groups having up to 20 carbon atoms (methyl, ethyl, butyl, dodecyl, etc.), and aryl groups such as phenyl and naphthyl. Examples of the heterocyclic group include thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like. The alkyl group represented by R ₃₃ is preferably an alkyl group having up to 20 carbon atoms, and examples thereof include methyl, ethyl, butyl, dodecyl and the like, and the aryl group is preferably an aryl group having 6 to 20 carbon atoms. Examples thereof include phenyl and naphthyl, and examples of the heterocyclic group include thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like.

In the -CONHR ₃₅ group, -COR ₃₅ group or -COOR ₃₅ group represented by W ₃ , the alkyl group represented by R ₃₅ is preferably an alkyl group having up to 20 carbon atoms, such as methyl, ethyl , Butyl, dodecyl and the like, and the aryl group is preferably an aryl group having 6 to 20 carbon atoms, such as phenyl and naphthyl, and the heterocyclic group includes, for example, thienyl, furyl, imidazolyl and pyrazolyl. , Pyrrolyl and the like.

Examples of the halogen atom represented by R ₃₄ include fluorine, chlorine, bromine and iodine. Examples of the alkyl group include chain or cyclic alkyl groups such as methyl, butyl, dodecyl and cyclohexyl. Examples of the group include alkenyl groups having up to 20 carbon atoms (vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3- Butenyl etc.), examples of the alkoxy group include methoxy, butoxy, tetradecyloxy and the like, and examples of the carbamoyl group include diethylcarbamoyl, phenylcarbamoyl and the like. Nitrile groups are also preferred. Among these, a hydrogen atom and an alkyl group are more preferable.

R ₃₃ and R ₃₄ may be connected to each other to form a ring structure. The above groups can further have a single substituent or multiple substituents. Typical substituents include halogen atoms (fluorine, chlorine, bromine, etc.), alkyl groups (methyl, ethyl, propyl, butyl, dodecyl, etc.), hydroxyl groups, cyano groups, nitro groups, alkoxy groups (methoxy, ethoxy, etc.) ), Alkylsulfonamide groups (such as methylsulfonamide, octylsulfonamide), arylsulfonamides (such as phenylsulfonamide, naphthylsulfonamide groups), alkylsulfamoyl groups (such as butylsulfamoyl), arylsulfamoyl ( Phenylsulfamoyl etc.), alkyloxycarbonyl group (methoxycarbonyl etc.), aryloxycarbonyl group (phenyloxycarbonyl etc.), aminosulfonamide group, acylamino group, carbamoyl group, sulfonyl group, sulfinyl group, sulfoxy group, Group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, arylcarbonyl group, and an amino carbonyl group.

R ₃₀ or R ₃₅ is preferably a phenyl group, more preferably a phenyl group having a plurality of halogen atoms and cyano groups as substituents.

In the —CONHR ₃₇ group, —COR ₃₇ group or —COOR ₃₇ group represented by R ₃₆ , the alkyl group represented by R ₃₇ is preferably an alkyl group having up to 20 carbon atoms, for example, methyl, ethyl, butyl The aryl group is preferably an aryl group having 6 to 20 carbon atoms, such as phenyl and naphthyl. Examples of the heterocyclic group include thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like. Is mentioned.

As the substituent that the group represented by R ₃₇ can have, the same substituents as those described in the description of R _{31 to} R _{34 in} formula (CLA) can be used.

Examples of the aryl group represented by X ₃ include aryl groups having 6 to 20 carbon atoms such as phenyl and naphthyl. Examples of the heterocyclic group include thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like. . Examples of the substituent that the group represented by X ₃ can have include the same substituents as those described in the description of R _{31 to} R _{34 in} formula (CLA). The group represented by X ₃ is preferably an aryl group or heterocyclic group having an alkylamino group (such as diethylamino) at the para position.

  These groups may include photographically useful groups.

  Specific examples of the cyan color forming leuco dye (CLA) are shown below, but the cyan color forming leuco dye used in the present invention is not limited thereto.

  Next, the compound represented by general formula (CLB-I) is demonstrated. The compound represented by the general formula (CLB-I) is preferably a compound represented by the following general formula (CLB-II) or (CLB-III), and most preferably a compound represented by (CLB-III). .

  First, the compound represented by formula (CLB-I) will be described.

In the formula, R ₄₁ , R ₄₂ , R _40a and R _40b each represent a hydrogen atom, an aliphatic group, an aromatic group, an alkoxy group, an aryloxy group, an acylamino group, a sulfonamide group, a carbamoyl group, or a halogen atom. R ₄₃ represents a hydrogen atom, an aliphatic group, an aromatic group, an acyl group, an alkoxycarbonyl group, an aryloxycarboquinyl group, a carbamoyl group, a sulfamoyl group, or a sulfonyl group. X ₄₁ and X ₄₂ represent a substitutable group on the benzene ring. m41 and m42 represent an integer of 0 to 5. When m41 and m42 is 2 or more, plural X ₄₁ and X ₄₂ may be the same or different.

Specific examples of the aliphatic group represented by R ₄₁ , R ₄₂ , R _40a and R _40b include hydrocarbon groups such as an alkyl group, an alkenyl group and an alkynyl group. These hydrocarbon groups preferably have 1 to 25 carbon atoms, and more preferably 1 to 20 carbon atoms. Examples of the alkyl group having 1 to 25 carbon atoms include methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, and cyclohexyl, cycloalkyl groups such as cyclohexyl and cyclopentyl groups, and alkenyl groups such as ethenyl-2. Examples of alkynyl groups such as -propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, and the like include ethynyl, 1propynyl, propargyl, and the like.

Specific examples of the aromatic group represented by R ₄₁ , R ₄₂ , R _40a and R _40b include aryl groups (phenyl, naphthyl, etc.), heterocyclic groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl). , Pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl and the like.

  Specific examples of the alkoxy group include methoxy, ethoxy, i-propoxy group, t-butoxy and the like, specific examples of the aryloxy group include phenoxy and naphthyloxy, and the acylamino group includes acetylamino, benzoylamino and the like. However, specific examples of the sulfonamide group include methanesulfonamide, butanesulfonamide, octanesulfonamide, and benzenesulfonamide, and examples of the carbamoyl group include aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, and pentyl. Examples include aminocarbonyl, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl and the like.

  The halogen atom is chlorine, bromine or iodine.

R ₄₁ and R ₄₂ are preferably an aliphatic group, an alkoxy group, an aryloxy group, more preferably an alkyl group or an alkoxy group, still more preferably a secondary or tertiary alkyl group or an alkoxy group.

R _40a and R _40b are preferably a hydrogen atom or an aliphatic group, more preferably a hydrogen atom.

Examples of the aliphatic group, aromatic group, alkoxy group and aryloxy group represented by R ₄₃ include the groups exemplified as specific examples for R ₄₁ and R ₄₂ .

Specific examples of the acyl group represented by R ₄₃ include acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl and the like.

Specific examples of the alkoxycarbonyl group represented by R ₄₃ include a methoxycarbonyl group, an ethoxycarbonyl group, a t-butoxycarbonyl group, and the like.

Specific examples of the aryloxycarbonyl group represented by R ₄₃ include phenoxycarbonyl and the like. Examples of the carbamoyl group include aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, pentylaminocarbonyl, cyclohexylaminocarbonyl. , Phenylaminocarbonyl, 2-pyridylaminocarbonyl and the like, examples of the sulfamoyl group include methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl and the like, and examples of the sulfonyl group include methylsulfonyl, butylsulfonyl and octyl. And sulfonyl.

R ₄₃ is preferably a hydrogen atom, an alkyl group, or an acyl group, more preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an acyl group.

Specific examples of the group that can be substituted on the benzene ring represented by X ₄₁ and X ₄₂ include alkyl groups having 1 to 25 carbon atoms (methyl, ethyl, propyl, isopropyl, t-butyl, pentyl, hexyl cyclohexyl, etc. ), Cycloalkyl groups (cyclohexyl, cyclopentyl, etc.), alkenyl groups (vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl -3-butenyl etc.), alkynyl group (ethynyl, propargyl etc.), glycidyl group, acrylate group, methacrylate group, aryl group (phenyl, naphthyl etc.), heterocyclic group (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, Pyrazinyl, pyrimidinyl, pyridazinyl, Lenazolyl, sulphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atom (chlorine, bromine, iodine, fluorine, etc.), alkoxy group (methoxy, ethoxy, propyloxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc.), aryl Oxy group (phenoxy, etc.), alkoxycarbonyl group (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl group (phenyloxycarbonyl, etc.), sulfonamide group (methanesulfonamide, ethanesulfonamide, butanesulfone) Amide, hexanesulfonamide, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl group (aminosulfonyl, methylaminosulfonyl, dimethyl) Ruaminosulfonyl, butylaminosulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyridylaminosulfonyl, etc.), ureido groups (methylureido, ethylureido, pentylureido, cyclohexylureido, phenylureido, 2-pyridylureido, etc.) ), Acyl groups (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.), carbamoyl groups (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, pentylaminocarbonyl, cyclohexylaminocarbonyl, phenyl) Aminocarbonyl, 2-pyridylaminocarbonyl, etc.), amide groups (acetamide, propiona) Amide, butanamide, hexaneamide, benzamide, etc.), sulfonyl group (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexylsulfonyl, phenylsulfonyl, 2-pyridylsulfonyl, etc.), sulfonamide group (methylsulfonamide, octylsulfonamide, phenylsulfone) Amide, naphthylsulfonamide, etc.), amino group (amino, ethylamino, dimethylamino, butylamino, cyclopentylamino, anilino, 2-pyridylamino, etc.), cyano group, nitro group, sulfo group, carboxyl group, hydroxyl group, oxamoyl group Etc. Further, these groups may be further substituted with these groups.

X ₄₁ and X ₄₂ are preferably an alkoxy group, an aryloxy group, a carbamoyl group, an amide group, a sulfonamide group, an amino group, more preferably an alkoxy group or an amino group.

  Next, among the compounds represented by the general formula (CLB-I), the compounds represented by the general formula (CLB-II) and the general formula (CLB-III) which are preferably used will be described.

Wherein, R _41, R _42, R ₄₃ are each synonymous with R _41, R _42, R ₄₃ in the general formula (CLB-I). X ₄₃ and X ₄₄ each represents an aliphatic group, an aromatic group, an amino group, an alkoxy group or an aryloxy group.

Examples of the aliphatic group, aromatic group, amino group, alkoxy group and aryloxy group represented by X ₄₃ and X ₄₄ are the aliphatic groups represented by X ₄₁ and X ₄₂ in the general formula (CLB-I). Examples thereof include the same groups as the specific examples of the group, aromatic group, amino group, alkoxy group and aryloxy group. X ₄₃ and X ₄₄ are preferably an alkoxy group, an aryloxy group or an amino group, more preferably an alkoxy group or an amino group.

R ₄₄ , R ₄₅ , R ₄₆ and R ₄₇ each represent a hydrogen atom or an alkyl group. Specific examples of the alkyl group include methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl and the like. These groups may have a substituent at an arbitrary position, and examples of the substituent include the groups exemplified as the substituent in the general formula (CLB-I). R ₄₄ , R ₄₅ , R ₄₆ and R ₄₇ are preferably an alkyl group having 1 to 10 carbon atoms, more preferably methyl or ethyl.

  The compounds represented by the general formulas (CLB-I) to (CLB-III) can be easily synthesized by a conventionally known method such as the method described in JP-B-7-45477. Specific examples of the leuco dyes represented by the general formulas (CLB-I) to (CLB-III) are shown below, but the present invention is not limited thereto.

  The addition amount of the cyan chromophoric leuco dye is usually 0.00001 to 0.05 mol, preferably 0.0005 to 0.02 mol, more preferably 0.001 to 0.01 mol, per mol of silver. is there. The addition ratio of the cyan color-forming leuco dye to the sum of the reducing agents is preferably 0.001 to 0.2, more preferably 0.005 to 0.1 in terms of molar ratio.

  In the photothermographic material of the invention, the sum of the maximum densities at the maximum absorption wavelength of a dye image formed with a cyan leuco dye is preferably 0.01 to 0.50, more preferably 0.02 to 0.30. In particular, it is preferable to develop the color so as to have 0.03 to 0.10.

  In the present invention, in addition to the above-described cyan color-forming leuco dye, a magenta color-forming leuco dye or a yellow color-forming leuco dye can be used in combination to enable further fine color tone adjustment.

  The yellow coloring leuco dye and cyan coloring leuco dye represented by the general formulas (YA) and (YB) are added in the same manner as the reducing agent addition method represented by the general formula (1). It may be added, and may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form, and may be contained in the photosensitive material.

  The reducing agent of the general formula (1), the yellow color-forming leuco dye and the cyan color-forming leuco dye of the general formulas (YA) and (YB) are preferably contained in a photosensitive layer containing an aliphatic carboxylic acid silver salt. However, one may be contained in the photosensitive layer and the other may be contained in the non-photosensitive layer adjacent to the photosensitive layer, or both may be contained in the non-photosensitive layer. When the photosensitive layer is composed of a plurality of layers, they may be contained in separate layers.

[Anti-fogging agent, image stabilizer]
Any constituent layer of the photothermographic material of the present invention includes an antifoggant for preventing fogging during storage before thermal development, and image stabilization for preventing image deterioration after thermal development. It is preferable to contain an agent. The fog prevention and image stabilizer that can be used in the present invention will be described below.

  Since reducing agents with protons such as bisphenols and sulfonamidophenols are mainly used as reducing agents, these hydrogens are stabilized, the reducing agents are deactivated, and reactions that reduce silver ions are prevented. It is preferred that a compound capable of preventing is contained. Further, it is preferable that a compound capable of oxidizing and bleaching silver atoms or metallic silver (silver clusters) generated during storage of raw films and images is preferably contained. Specific examples of the compound having these functions include, for example, biimidazolyl compounds, iodonium compounds and compounds capable of releasing halogen atoms as active species described in paragraphs “0096” to “0128” of JP-A-2003-270755. Can be mentioned.

  Further, a polymer having at least one repeating unit of a monomer having a halogen radical releasing group as disclosed in JP-A No. 2003-91054, vinyl sulfones described in paragraph “0013” of JP-A No. 6-208192 and / or Examples of preferred anti-fogging and image stabilizers include β-halosulfones and vinyl type inhibitors having an electron-withdrawing group described in Japanese Patent Application No. 2004-234206.

  When the reducing agent used in the present invention has an aromatic hydroxyl group (—OH), particularly in the case of bisphenols, a non-reducing compound having a group capable of forming a hydrogen bond with these groups It is preferable to use together. Specific examples of particularly preferred hydrogen bonding compounds in the present invention include compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937. It is done.

  On the other hand, many compounds that can release halogen atoms as active species are known as antifogging and image stabilizers. Specific examples of the compound that generates these active halogen atoms include compounds represented by general formula (9) described in paragraphs “0264” to “0271” of JP-A No. 2002-287299.

  The addition amount of these compounds is preferably within a range in which the increase in printout silver due to the formation of silver halide due to the reaction between the halogen released from the compound and silver ions does not become a problem. Specific examples of compounds that generate these active halogen atoms include, in addition to the above-mentioned patents, compounds (III-1) to (III-) described in paragraphs “0086” to “0087” of JP-A No. 2002-169249. 23), compounds 1-1a to 1-1o and 1-2a to 1-2o described in paragraphs “0031” to “0034” of JP-A-2003-50441, and compounds 2a to 1-20056 described in paragraphs “0050” to “0056” 2z, 2aa to 2ll, 2-1a to 2-1f, compounds 4-1 to 4-32 described in paragraphs “0055” to “0058” of JP-A No. 2003-91054, and paragraphs “0069” to “0072” Examples thereof include compounds 5-1 to 5-10.

  Antifoggants preferably used in the present invention include, for example, compound examples a to j described in paragraph “0012” of JP-A-8-314059, and thiosulfonates described in paragraph “0028” of JP-A-7-209797. Esters A to K, compound examples (1) to (44) described from page 14 of JP-A No. 55-140833, and compounds (I-1) to (I) described in paragraph “0063” of JP-A No. 2001-13627 -6), (C-1) to (C-3) described in paragraph “0066”, compounds (III-1) to (III-108) described in paragraph “0027” of JP-A-2002-90937, vinyl sulfone And / or β-halosulfones as compounds VS-1 to VS-7, compounds HS-1 to HS-5 and sulfonylbenzotriazo described in paragraph “0013” of JP-A-6-208192 Compounds KS-1 to KS-8 described in JP-A No. 2000-330235 as substituted compounds, PR-01 to PR-08 described in JP-T 2000-515995 as substituted propene nitrile compounds, JP-A 2002-2002 Examples thereof include compounds (1) -1 to (1) -132 described in paragraphs “0042” to “0051” of No. 207273.

  The antifoggant is generally used in an amount of at least 0.001 mol per 1 mol of silver. Usually, the range is 0.01 to 5 mol, preferably 0.02 to 0.6 mol, per mol of silver.

  In addition to the above compounds, the photothermographic material may contain various compounds conventionally known as antifoggants, but may generate reactive species similar to the above compounds. Even a compound that can be used may be a compound that has a different antifogging mechanism. For example, U.S. Pat. Nos. 3,589,903, 4,546,075, 4,452,885, JP-A-59-57234, U.S. Pat. Nos. 3,874,946, 4,756,999. And compounds described in JP-A-9-288328 and JP-A-9-90550. Further, other antifoggants include compounds disclosed in US Pat. No. 5,028,523 and European Patents 600,587, 605,981, and 631,176.

[Color preparation]
The photothermographic material forms a photographic image by heat development processing, and usually contains a toning agent (toner) for adjusting the color tone of silver as needed, dispersed in an (organic) binder matrix. It is preferable.

  Examples of suitable toning agents for use in the present invention are disclosed in RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. For example, there are the following.

  Imides (succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide, etc.); mercaptans (3-mercapto-1,2,4-triazole, etc.); phthalazinone derivatives or metal salts of these derivatives (phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); phthalazine and phthalic acids (eg, phthalic acid) , 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid); phthalazine and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivative and anhydride (phthalic acid) 4-methylphthalic acid, 4-nitrophthalic acid and tetrachloro Combination of at least one compound selected from the barrel anhydride, etc.). Particularly preferred color tones are phthalazinone or a combination of phthalazine and phthalic acids and phthalic anhydrides.

[Dye / Pigment]
In the photothermographic material, a filter layer is formed on the same side as or opposite to the photosensitive layer in order to control the amount of light transmitted through the photosensitive layer or the wavelength distribution, or a dye or pigment is added to the photosensitive layer. It is preferable to contain.

  As the dye used, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the photosensitive material. For example, when the photothermographic material is an image recording material using infrared light, a squarylium dye having a thiopyrylium nucleus as disclosed in JP-A-2001-83655 (referred to herein as a thiopyrylium squarylium dye). And a squarylium dye having a pyrylium nucleus (referred to herein as a pyrylium squarylium dye), a thiopyrylium croconium dye similar to a squarylium dye, or a pyrylium croconium dye. The compound having a squarylium nucleus is a compound having 1-cyclobuten-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy in the molecular structure. It is a compound having -4,5-dione. Here, the hydroxyl group may be dissociated. Hereinafter, these pigments are collectively referred to as squarylium dyes for convenience. As the dye, a compound described in JP-A-8-201959 is also preferable.

[Activators and slip agents]
(Fluorine surfactant)
In the present invention, a fluorine-based surfactant represented by the following general formula (SF) is used in order to improve film transportability and environmental suitability (accumulation in a living body) in a laser imager (heat development processing apparatus). Preferably used.

Formula (SF) (Rf− (L) _n −) _p − (Y) _m − (A) _q
In the formula, Rf represents a substituent containing a fluorine atom, L represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, and A represents An anionic group or a salt thereof is represented, n and m each represents an integer of 0 or 1, p represents an integer of 1 to 3, and q represents an integer of 1 to 3. However, when q is 1, n and m are not 0 at the same time.

  In the general formula (SF), examples of the substituent containing a fluorine atom represented by Rf include a fluorinated alkyl group having 1 to 25 carbon atoms (trifluoromethyl, trifluoroethyl, perfluoroethyl, perfluorobutyl, perfluoro Octyl, perfluorododecyl, perfluorooctadecyl, etc.) or alkenyl fluoride groups (perfluoropropenyl, perfluorobutenyl, perfluorononenyl, perfluorododecenyl, etc.). Rf preferably has 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms. Rf preferably has 2 to 12 fluorine atoms, more preferably 3 to 12 fluorine atoms.

  Examples of the divalent linking group having no fluorine atom represented by L include alkylene groups (methylene, ethylene, butylene, etc.), alkyleneoxy groups (methyleneoxy, ethyleneoxy, butyleneoxy, etc.), oxyalkylene groups (oxymethylene). Oxyethylene, oxybutylene, etc.), oxyalkyleneoxy groups (oxymethyleneoxy, oxyethyleneoxy, oxyethyleneoxyethyleneoxy, etc.), phenylene groups, oxyphenylene groups, phenyloxy groups, oxyphenyloxy groups or these groups Examples include a combined group.

  A represents an anionic group or a salt thereof. For example, a carboxyl group or a salt thereof (sodium salt, potassium salt and lithium salt), a sulfo group or a salt thereof (sodium salt, potassium salt and lithium salt), a sulfuric acid half ester group or a salt thereof Examples thereof include salts (sodium salt, potassium salt and lithium salt), and phosphoric acid groups or salts thereof (sodium salt, potassium salt and the like).

  Examples of the (p + q) -valent linking group having no fluorine atom represented by Y include, for example, an atomic group composed mainly of a nitrogen atom or a carbon atom as a trivalent or tetravalent linking group having no fluorine atom. Can be mentioned. n1 represents 0 or an integer of 1, and is preferably 1.

  The fluorine-based surfactant represented by the general formula (SF) is an alkyl compound having 1 to 25 carbon atoms into which a fluorine atom is introduced (trifluoromethyl, pentafluoroethyl, perfluorobutyl, perfluorooctyl, perfluorooctadecyl, etc. Compound) and alkenyl compounds (compounds having perfluorohexenyl, perfluorononenyl, etc.), 3- to 6-valent alkanol compounds each having no fluorine atom introduced, and aromatic compounds having 3 to 4 hydroxyl groups Alternatively, it can be obtained by further introducing an anionic group (A) into the compound obtained by addition reaction or condensation reaction with a hetero compound (partially converted to alkanol compound) by, for example, sulfate esterification.

  Examples of the trivalent to hexavalent alkanol compound include glycerin, pentaerythritol, 2-methyl-2-hydroxymethyl 1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentene, and 1,2,6-hexane. Examples include triol, 1,1,1-tris (hydroxymethyl) propane, 2,2-bis (butanol) -3, aliphatic triol, tetramethylolmethane, D-sorbitol, xylitol, D-mannitol and the like. Examples of the aromatic compound and hetero compound having 3 to 4 hydroxyl groups include 1,3,5-trihydroxybenzene (phloroglucin) and 2,4,6-trihydroxypyridine.

  The preferred specific compounds of the fluorine-based surfactant represented by the general formula (SF) are shown below.

  As a method of adding the fluorine-based surfactant represented by the general formula (SF) to the coating solution, it can be added according to a known addition method. That is, it can be dissolved and added in alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone and acetone, polar solvents such as dimethyl sulfoxide and dimethylformamide. Further, fine particles of 1 μm or less can be dispersed in water or an organic solvent by sand mill dispersion, jet mill dispersion, ultrasonic dispersion or homogenizer dispersion, and added. Many techniques for fine particle dispersion are disclosed, but they can be dispersed according to these techniques. The fluorine-based surfactant represented by the general formula (SF) is preferably added to the outermost protective layer.

The addition amount of the fluorine-based surfactant represented by the general formula (SF) is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ² , particularly 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol. preferable. If the range is less than the former range, charging characteristics may not be obtained. If the range exceeds the former range, the humidity dependency is large, and the storage stability under high humidity may be deteriorated.

(Surface property modifier)
The photothermographic material is used in contact with various apparatuses during winding, rewinding, and transporting of the photosensitive material in a manufacturing process such as coating, drying, and processing, or between a photosensitive surface and a backing surface. The contact between photosensitive materials is often undesirably affected. For example, the surface of the photosensitive material may be scratched or slipped, or the photosensitive material may be deteriorated in the developing device.

  Therefore, in the photothermographic material, in order to prevent scratches on the surface and deterioration of transportability, a lubricant, in any one of the constituent layers of the material, particularly the outermost layer on the support, It is preferable to add a matting agent or the like to adjust the surface physical properties of the photosensitive material.

  In the photothermographic material of the present invention, the outermost layer on the support contains organic solid lubricant particles having an average diameter of 1 to 30 μm, and the organic solid lubricant particles are dispersed by a polymer dispersant. This is true. The melting point of the lubricant particles is preferably higher than the heat development processing temperature, and is 80 ° C. or higher, more preferably 110 ° C. or higher.

  The organic solid lubricant particles used in the present invention are preferably compounds that lower the surface energy. Examples thereof include particles formed by pulverizing polyethylene, polypropylene, polytetrafluoroethylene, and copolymers thereof. Examples of organic solid lubricant particles made of polyethylene and polypropylene include polytetrafluoroethylene, polypropylene / polyethylene copolymer, polyethylene (low density), polyethylene (high density), and polypropylene.

  The organic solid lubricant particles are preferably a compound represented by the following general formula (SC1) or general formula (SC2).

Formula (SC1) (R _SC1 ) _p -X _SC1 -L ₆ -X _SC2- (R _SC2 ) _q
Formula (SC2) (R _SC1 -COO-) _z ^-- M ^{+ z}
In the formula, R _SC1 and R _SC2 are each a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group having 6 to 60 carbon atoms, and when p or q is 2 or more, a plurality of R _SC1 And R _SC2 may be the same as or different from each other. X _SC1 and X _SC2 each represent a divalent linking group containing a nitrogen atom. L ₆ represents a substituted or unsubstituted p + q valent alkyl group, alkenyl group, aralkyl group or aryl group. M represents a Z-valent metal ion.

In the compound represented by the general formula (SC1) or (SC2), the total number of carbon atoms is not particularly limited, but is generally preferably 20 or more, and more preferably 30 or more. Examples of the substituent that the alkyl group, alkenyl group, aralkyl group or aryl group in the definition of R _SC1 and R _SC2 may have include a halogen atom, a hydroxyl group, a cyano group, an alkoxy group, an aryloxy group, an alkylthio group. Groups, arylthio groups, alkoxycarbonyl groups, aryloxycarbonyl groups, amino groups, acylamino groups, sulfonylamino groups, ureido groups, carbamoyl groups, sulfamoyl groups, acyl groups, sulfonyl groups, sulfinyl groups, aryl groups and alkyl groups. be able to. These groups may further have a substituent, and preferred substituents are a halogen atom, a hydroxyl group, an alkoxy group, an alkylthio group, an alkoxycarbonyl group, an acylamino group, a sulfonylamino group, an acyl group, and an alkyl group. . As the halogen atom, a fluorine atom and a chlorine atom are preferable.

The alkyl component in the alkoxy group, alkylthio group, and alkoxycarbonyl group is the same as the alkyl group of R _SC2 described later. The amino group of the acylamino group and sulfonylamino group may be an N-substituted amino group, and the substituent is preferably an alkyl group. The groups bonded to the acylamino group, the carbonyl group of the acyl group, and the sulfonyl group of the sulfonylamino group are an alkyl group and an aryl group, and the above alkyl groups are preferable.

R _SC1 and R _SC2 are substituted or unsubstituted alkyl, alkenyl, aralkyl, or aryl groups having 6 to 60 carbon atoms, preferably 6 to 40 carbon atoms, more preferably 10 to 30 carbon atoms. The alkyl group, alkenyl group, and aralkyl group may be linear, branched, or cyclic, or may be a mixture thereof. Examples of preferred _RSC1 and R _SC2, octyl, t-octyl, dodecyl, tetradecyl, hexadecyl, 2-hexyl decyl, octadecyl, C _n H _2n-1 (the n 20 to 60), eicosyl, docosanyl, Merishiniru, octenyl , Myristolyl, oleyl, erucyl, phenyl, naphthyl, benzyl, nonylphenyl, dipentylphenyl, cyclohexyl groups and groups having these substituents.

The divalent linking groups X _SC1 and X _SC2 containing a nitrogen atom are preferably —CON (R ₃ ) —, —N (R ₄ ) CON (R ₅ ) —, and —N (R ₆ ) COO—. Here, R < ₃ > -R < ₆ > shows a hydrogen atom or a substituent, respectively.

L ₆ represents a substituted or unsubstituted p + q valent alkyl group, alkenyl group, aralkyl group or aryl group. Although carbon number of these hydrocarbon groups is not specifically limited, Preferably it is 1-60, More preferably, it is 1-40, More preferably, it is 10-40. “p + q valence” in a p + q valent hydrocarbon group means that p + q hydrogen atoms in the hydrocarbon are removed and p X _SC1 − groups and q −X _SC2 groups are bonded thereto. . p and q represent an integer of 0 to 6, 1 ≦ p + q ≦ 6, and preferably 1 ≦ p + q ≦ 4. Moreover, the case where both p and q are 1 is preferable.

  The compound represented by the general formula (SC1) may be a synthetic product or a natural product. Even if it is a natural product or a synthetic product, a synthetic compound using a higher fatty acid or alcohol as a raw material includes those having different numbers of carbon atoms and those having a straight chain and a branched chain. There is no problem using it. From the viewpoint of the quality stability of the composition, a synthetic product is preferable.

  Although the specific example of a compound represented with preferable general formula (SC) below is shown, this invention is not limited to these.

  Lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxy stearic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, N-lauryl lauric acid amide, N-palmityl palmitic acid amide, N- Stearyl stearic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl palmitic acid amide, N-stearyl-hydroxystearic acid amide, N Oleyl-hydroxystearic acid amide, methylol stearic acid amide, methylol behenic acid amide, methylene bis stearic acid amide, methylene bis lauric acid amide, methylene bis hydroxy stearic acid amide, ethyl Biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene Bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, butylene bishydroxystearic acid amide, N, N'-distearyl adipic acid amide, N, N'-distearyl sebacic acid amide, methylene bisoleic acid amide, ethylenebis Oleic acid amide, ethylene bis erucic acid amide, hexamethylene bis oleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide, -Xylylene stearamide, N, N'-distearylisophthalamide, ethanolamine distearate, N-butyl-N'-stearyl urea, N-phenyl-N'-stearyl urea, N-stearyl-N ' -Stearyl urea, xylylene bisstearyl urea, toluylene bisstearyl urea, hexamethylene bisstearyl urea, diphenylmethane bisstearyl urea.

  The organic solid lubricant is preferably used in a state of being dispersed in the coating solution in advance. As the name suggests, the organic solid lubricant has a property that the surface is slippery, and therefore, the affinity between water and the organic solvent is not sufficiently high in many cases. It may cause sedimentation. Aggregation or sedimentation in the coating solution is undesirable because it causes coating failure when processed into a film. Examples of a method for improving the stability of the dispersion include a method of modifying the surface and using an electrostatic effect, and a method of using a steric hindrance effect using a surface adsorbing layer by a polymer dispersant. The former is a general dispersion stabilization method, but there is a concern about the influence of the surface modifier itself on other performance from the point of use in a photothermographic material, and it is effective in both aqueous and non-aqueous systems. The latter method, which is easy to express, is preferred.

  As the polymer dispersant, a binder used in the photosensitive material can be used. Specifically, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, cellulose acetate butyrate, cellulose acetate propionate, and the like can be used.

  The amount of the polymer dispersant is preferably used in the range of 1 to 200% by mass with respect to the organic solid lubricant particles as a dispersion. A dispersion method is not particularly limited, but a resolver type, an ultrasonic type, a pressure type, or the like can be used, and it is preferable to perform a dispersion treatment with a dispersion device having a cooling device so as not to generate heat.

  The average particle diameter of the organic solid lubricant particles refers to the average particle diameter after dispersion by the following method. In order to obtain the average particle size referred to in the present invention, a dispersion liquid containing lubricant particles is diluted, dropped onto a grid with a carbon support film and dried, and a transmission electron microscope (manufactured by JEOL Ltd .: 2000FX type) is used. Etc.), after taking a picture at a direct magnification of 5000 times, the negative is captured as a digital image with a scanner, and each particle size (equivalent circle diameter) is measured by 300 or more using an appropriate image processing software. The average particle diameter can be obtained from the arithmetic average.

  In the light-sensitive material of the present invention, at least one layer on the support contains the compound represented by the general formula (SC), and a nonionic fluorine-containing surfactant and an anionic fluorine-containing surfactant are included. It is preferable to contain.

  The nonionic fluorine-containing surfactant that can be used is not particularly limited, but a compound represented by the following general formula (AIF) is preferable.

Formula (AIF) Rf _1- (AO) _n -Rf ₂
In the formula, Rf ₁ and Rf ₂ represent a fluorine-containing aliphatic group and may be the same or different. AO represents a divalent group having at least one alkyleneoxy group, and n represents an integer of 1 to 30.

Examples of the fluorine-containing aliphatic group represented by Rf ₁ and Rf ₂ include aliphatic groups composed of linear, branched and cyclic groups, or combinations thereof, such as alkylcycloaliphatic groups. Preferred fluorine-containing aliphatic groups are each a fluoroalkyl group having 1 to 20 carbon atoms (such as —C ₄ F ₉ and —C ₈ F ₁₇ ), and a sulfofluoroalkyl group (C ₇ F ₁₅ SO ₃ —, C ₈ F). ₁₇ SO ₃ — etc.), C _n F _{2n + 1} SO ₂ N (R ₁ ) R ₂ — group (R ₁ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an alkyl carboxyl group or an aryl group, respectively. , R ₂ represents an alkylene group having 1 to 20 carbon atoms and an alkylenecarbonyl group, and n represents an integer of 1 to 20. C ₇ F ₁₅ SO ₂ N (C ₂ H ₅ ) CH ₂ —, C ₈ F ₁₇ SO ₂ N (CH ₂ COOH) CH ₂ CH ₂ CH ₂ — and the like), which may further have a substituent.

AO is a group having an alkyleneoxy group such as ethyleneoxy, propyleneoxy, i-propyleneoxy, and may have a substituent such as an amino group at the terminal. n is preferably an integer of 5 to 15. Examples of the nonionic fluorine-containing surfactant represented by the general formula (AIF) include C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₂₄ C ₁₂ F ₂₅ , C ₈ F ₁₇ (CH ₂ CH ₂ O). ₈ C ₈ F ₁₇ , C ₇ F ₁₅ CH ₂ CH (OH) CH ₂ (CH ₂ CH ₂ O) ₁₅ CH ₂ CH (OH) CH ₂ C ₇ F ₁₅ , C ₇ F ₁₅ (CH ₂ CH ₂ O) ₁₀ C ₇ F ₁₅ , C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₅ C ₁₂ F ₂₅ , C ₈ F ₁₇ CH ₂ CH (OH) CH ₂ (CH ₂ CH ₂ O) ₂₀ CH ₂ CH (OH) CH ₂ C ₈ F ₁₇ , C ₈ F ₁₇ (CH ₂ CH ₂ O) ₁₈ C ₈ F ₁₇ , C ₈ F ₁₇ (CH ₂ CH ₂ O) ₂₀ C ₈ F ₁₇ , C ₇ F ₁₅ SO ₂ N (C _{2 H 5) CH 2 (CH 2} CH 2 O) 22 CH 2 N (CH 3) SO 2 C 7 F 15, although such _{C 9 F 17 O (CH 2} CH 2 O) 22 C 9 F 17 and the like, The present invention is not limited to these. There.

  The anionic fluorine-containing surfactant (FA) that can be used in the present invention is not particularly limited, and specific compounds are shown below, but the present invention is not limited thereto.

The amount of each fluorine-containing surfactant used is generally 0.01 to 1 g, preferably 10 to 500 mg, per 1 m ² of the photosensitive material. More preferably, it is 50-300 mg.

  As fluorine-containing surfactants, in addition to the above, ionic fluorine-based surfactants described in JP-A-60-244945, JP-A-63-306437, and JP-A-1-24245, JP-A-5-197068 And fluorine-based surfactants used in combination with anions and cations described in JP-A-5-204115.

  The addition layer of the fluorine-containing surfactant is not particularly limited and may be in any layer, but is preferably contained in the outermost surface layer.

[Support]
Examples of the support material used for the photothermographic material include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (aluminum, etc.), etc., but flexible in handling as an information recording material. A material that can be processed into a sheet or a roll having a property is suitable. Therefore, as a support in the photothermographic material of the present invention, cellulose acetate film, polyester film, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyamide film, polyimide film, cellulose triacetate film (TAC) or A plastic film such as a polycarbonate (PC) film is preferable, and a biaxially stretched PET film is particularly preferable. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  In order to improve the charging property, a conductive compound such as a metal oxide and / or a conductive polymer can be included in the constituent layer. These may be contained in any layer, but are preferably contained in the backing layer or the surface protective layer on the photosensitive layer side, the undercoat layer and the like. The conductive compounds described in columns 14 to 20 of US Pat. No. 5,244,773 are preferably used.

Among these, in the present invention, the surface protective layer on the backing layer side preferably contains a conductive metal oxide. Here, the conductive metal oxide is crystalline metal oxide particles, and those containing oxygen defects and those containing a small amount of hetero atoms forming a donor with respect to the metal oxide used are generally used. In particular, it is particularly preferable because of its high conductivity, and the latter is particularly preferable because it does not give fog to the silver halide emulsion. Examples of metal oxides are ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O _5, etc., or a composite oxide thereof, especially ZnO, TiO ₂ and SnO ₂ are preferred. As an example of containing a heteroatom, addition Al, or In to ZnO, addition Sb, Nb, P, such as a halogen element relative to SnO _2, In addition, Nb for TiO _2, Ta Etc. are effective. The amount of these different atoms added is preferably in the range of 0.01 to 30 mol%, but particularly preferably 0.1 to 10 mol%. Furthermore, a silicon compound may be added during the production of fine particles in order to improve fine particle dispersibility and transparency.

The metal oxide fine particles used in the present invention have electrical conductivity, and their volume resistivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A Nos. 56-143431, 56-120519, and 58-62647. Furthermore, as described in Japanese Examined Patent Publication No. 59-6235, a conductive material in which the above metal oxide is attached to other crystalline metal oxide particles or fibrous materials (such as titanium oxide) may be used. .

The particle size that can be used is preferably 1 μm or less, but if it is 0.5 μm or less, the stability after dispersion is good and it is easy to use. In order to make the light scattering property as small as possible, it is very preferable to use conductive particles of 0.3 μm or less because a transparent photosensitive material can be formed. Further, when the conductive metal oxide is needle-like or fibrous, the length is preferably 30 μm or less and the diameter is preferably 1 μm or less, particularly preferably the length is 10 μm or less and the diameter is 0.3 μm or less. / Diameter ratio is 3 or more. SnO ₂ is commercially available from Ishihara Sangyo Co., Ltd., and SNS10M, SN-100P, SN-100D, FSS10M and the like can be used.

[Layer structure]
The photothermographic material of the present invention has at least one photosensitive layer as an image forming layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer. For example, a protective layer is preferably provided on the photosensitive layer for the purpose of protecting the photosensitive layer, and the opposite surface of the support is "sticked" between the photosensitive materials or in the photosensitive material roll. In order to prevent “,” a backcoat layer is provided.

  As a binder used in these protective layers and backcoat layers, polymers having a glass transition point (Tg) higher than that of the photosensitive layer and less likely to be scratched or deformed, such as cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Is selected from the binders.

  For gradation adjustment or the like, two or more photosensitive layers may be provided on one side of the support or one or more layers on both sides of the support.

[Application of component layers]
The photothermographic material is preferably formed by preparing a coating solution obtained by dissolving or dispersing the above-described constituent layers in a solvent, applying a plurality of coating solutions simultaneously, and then performing a heat treatment. Here, “multiple simultaneous multi-layer coating” means that a coating solution for each constituent layer (photosensitive layer, protective layer, etc.) is prepared, and when this is coated on a support, the coating and drying are repeated for each layer individually. Instead, it means that the respective constituent layers are formed in such a state that simultaneous multilayer coating and drying can be performed. That is, the upper layer is provided before the remaining amount of all the solvents in the lower layer reaches 70% by mass or less (more preferably 90% by mass or less).

  There are no particular restrictions on the method of applying multiple layers of each constituent layer simultaneously, for example, bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, reverse roll coating method, gravure coating method, extrusion coating. A known method such as a method can be used. Of these various methods, the slide coating method and the extrusion coating method are more preferable. These coating methods have been described on the side having the photosensitive layer, but the same applies to the case of coating with the undercoat layer when the back layer is provided. Japanese Unexamined Patent Publication No. 2000-15173 has a detailed description on the simultaneous multilayer coating method in the photothermographic material.

The silver coating amount is preferably selected in accordance with the purpose of the light-sensitive material, but is preferably 0.8 to 1.5 g / m ² for the purpose of medical images, and 1.0 to 1 .3 g / m ² is more preferable. Among the applied silver amount, those derived from silver halide preferably account for 2 to 18%, more preferably 5 to 15%, based on the total silver amount. The coating density of silver halide grains of 0.01 μm or more (equivalent particle diameter equivalent to sphere) is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁸ particles / m ² . Furthermore, 1 * 10 < ¹⁵ > -1 * 10 < ¹⁷ > piece / m < ² > is preferable.

Furthermore, the coating density of the non-photosensitive long-chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ to 1 × 10 ⁻¹⁴ g per silver halide grain of 0.01 μm or more (equivalent particle diameter in terms of sphere). Is preferably 1 × 10 ⁻¹⁶ to 1 × 10 ⁻¹⁵ g.

  In the case of coating under the conditions within the above range, preferable results are obtained from the viewpoint of the optical maximum density of the silver image per fixed coating silver amount, that is, the silver coating amount (covering power) and the color tone of the silver image. Is obtained.

The photothermographic material of the invention preferably contains a solvent in the range of 5 to 1,000 mg / m ² during development. It is more preferable to adjust so that it may be 10-150 mg / m < ² >. As a result, the photothermographic material has high sensitivity, low fog, and high maximum density. Examples of the solvent include, but are not limited to, those described in paragraph “0030” of JP-A No. 2001-264930. These solvents can be used alone or in combination of several kinds. The content of the solvent in the photosensitive material can be adjusted by changing conditions such as temperature conditions in the drying step after the coating step. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

[Heat development]
The photothermographic material of the present invention is characterized in that after imagewise exposure, the photothermographic material is processed by a heat developing machine for forming an image by heating at a desired development temperature. The heat development temperature is preferably in the range of 110 to 150 ° C, and more preferably in the range of 115 to 135 ° C. If the heating temperature is less than 80 ° C., sufficient image density cannot be obtained in a short time, and if the heating temperature is high (particularly 200 ° C. or more), transfer to the roller due to melting of the binder, transportability, developing machine, etc. are also adversely affected. Effect. By heating, a silver image is generated by a redox reaction between the aliphatic carboxylic acid silver salt (which functions as an oxidizing agent) and the reducing agent. This reaction process proceeds without any supply of treatment liquid such as water from the outside.

  Any heating means may be used, such as contact heating with a heating drum or a heating plate, non-contact heating such as radiation, but contact heating with a heating plate is preferred. The contact heating surface may be on either the photosensitive layer side or the non-photosensitive layer side, but the non-photosensitive layer side is preferably the contact heating surface in terms of stability to the processing environment. The developing unit is preferably configured by combining a plurality of independently temperature-controlled zones and a plurality of means, and further has at least one heat retention zone for maintaining a specific developing temperature. preferable. Therefore, in the thermal development apparatus that can be preferably used in the present invention, the thermal development process can adopt a separate configuration for the temperature raising part and the heat retaining part, and the heating means such as a heating member and the sheet film are closely connected in the temperature raising part. It is possible to prevent uneven density by making contact, and it is not necessary to make such close contact in the heat retaining part, and by using an optimal heating method that differs between the temperature rising part and the heat retaining part, high image quality without density unevenness Thus, it is possible to achieve a configuration that allows rapid processing of the thermal development process, downsizing of the apparatus, and cost reduction.

  In the thermal development apparatus, the temperature raising unit heats the sheet film while pressing the sheet film against a plate heater by a counter roller, and the heat retaining unit is in a slit formed between guides having at least one heater. The sheet film can be heated. In the temperature raising part, the sheet heater can be brought into close contact with the plate heater by pressing it against the plate heater with the opposing roller. On the other hand, in the heat retaining part, the conveying force of the opposing roller in the temperature raising part is used. Since it suffices to transport while keeping (heating) between the slits, driving parts for the transport system become unnecessary, and the size of the apparatus can be reduced and the cost can be reduced without requiring much precision of the slit dimensions.

  According to this heat development apparatus, in the first zone, the sheet film is heated by securing a close contact between the heating means such as a heating member and the sheet film, and the occurrence of density unevenness is suppressed. Since there is no need to make contact, by keeping the sheet film warm in the guide gap in the second zone, it is possible to quickly process the thermal development process, downsize the equipment and reduce costs while maintaining high image quality without density unevenness. Can be configured. When the guide gap is 3 mm or less, there is little effect on the heat retaining performance regardless of the sheet film conveyance posture in the second zone, and the positioning accuracy between the fixed guide and another guide is not so required, and both guides are processed. The tolerance for time curvature error and mounting accuracy is increased, resulting in a significant increase in design freedom, which can contribute to cost reduction of the apparatus.

  In the thermal development apparatus, it is preferable that a guide gap of the second zone is in a range of 1 to 3 mm. When the guide gap is 1 mm or more, the coated surface of the photothermographic material of the sheet film is difficult to touch the guide surface, and the occurrence of scratches is reduced.

  Further, it is preferable that the fixed guide and the guide in the second zone have substantially the same curvature. When the curvature of the guide in the second zone is given to reduce the size of the apparatus, a guide with a substantially constant guide gap can be configured.

  Further, the engagement time with the sheet film in the temperature raising portion and the heat retaining portion can be configured to be 10 seconds or less, and the period of the temperature raising step and the heat retaining step can be shortened so that the rapid processing of the thermal development process can be performed. Is possible.

  In addition, a concave portion is provided between the temperature raising portion and the heat retaining portion so that foreign matter from the temperature rising portion enters the concave portion, so that the front end of the film is conveyed while the temperature raising portion is conveyed. The foreign matter accumulated and moved by the portion can be prevented from being brought into the heat retaining portion, and jamming, scratches, density unevenness, etc. can be prevented from occurring on the sheet film.

  In addition, it is preferable that the temperature raising part and the heat retaining part are configured to heat the sheet film by opening the application surface side of the photothermographic material. Also in the cooling section, it is preferable to perform cooling by opening the coated surface side of the photothermographic material.

  However, the mechanism of the heat retaining zone may be a mechanism that maintains the heated film temperature, and is not limited to the above. The development time is preferably 5 to 10 seconds.

(Developer having a preheat zone heated to 70 to 100 ° C. immediately before heat development)
In the present invention, an image is formed by processing a photothermographic material in a heat developing machine having a preheat zone heated to 70 to 100 ° C. after the imagewise exposure and before the heat development step of heating at a desired development temperature. preferable. Furthermore, it is preferable to process with the heat developing machine which has a preheat zone heated to 90-100 degreeC. Although there is no restriction | limiting in particular in the heating mechanism of a preheat zone, From a viewpoint of cost and controllability, contact heating with a heating plate is preferable. The heating temperature accuracy of the preheat zone is preferably ± 1 ° C., more preferably ± 0.5 ° C. Although the appropriate value of the heating time varies depending on the heating mechanism, it is preferably in the range of 0.5 to 7 seconds, and more preferably in the range of 1 to 3 seconds.

(Developer having a slow cooling zone in which development is stopped by adjusting to a temperature lower by 10 to 20 ° C. than the thermal development temperature)
The present invention relates to a heat developing machine having a slow cooling zone in which a photothermographic material is heated at a desired development temperature after imagewise exposure and then adjusted to a temperature lower by 10 to 20 ° C. than the heat development temperature to stop development. It is preferable to form an image by processing in the above. Furthermore, it is preferable to process with a heat developing machine having a slow cooling zone in which the development is stopped by adjusting the temperature to 10 to 15 ° C. lower than the heat development temperature. The mechanism of the slow cooling zone is not particularly limited, but contact cooling with a plate adjusted to a desired temperature is preferable from the viewpoint of cost and controllability. The temperature accuracy of the slow cooling zone is preferably ± 1 ° C., more preferably ± 0.5 ° C. The slow cooling time is preferably x0.25 or more with respect to the development time, and is preferably in the range of x0.25 to x1.0 in view of rapid processing.

  The laser imager (heat development processing device) referred to in the present invention is configured to supply uniform and stable heat to the entire surface of a film supply device represented by a film tray, a laser image recording device, and a photothermographic material. The image forming apparatus includes a heat developing unit and a film supply unit, which is configured to include a conveying unit until the heat-developable photosensitive material image-formed by heat development is discharged from the apparatus through laser recording.

[exposure]
As for the exposure used for the exposure of the photothermographic material of the present invention or the exposure in the image forming method of the present invention, various conditions are adopted with respect to the light source, exposure time, etc. suitable for obtaining a desired appropriate image. can do.

  The photothermographic material of the present invention preferably uses a laser beam when recording an image. It is desirable to use a light source suitable for the color sensitivity imparted to the photosensitive material. For example, if the photosensitive material is sensitive to infrared light, it can be applied to any light source as long as it is in the infrared light range. However, the laser power is high, or the photothermographic material is made transparent. From the viewpoint of being able to do so, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

The photothermographic material of the present invention preferably exhibits its characteristics when exposed to light of high illuminance with a light amount of 1 mW / mm ² or more for a short time. The illuminance here refers to the illuminance when the photosensitive material after heat development has an optical density of 3.0. When exposure is performed at such high illuminance, the amount of light (= illuminance × exposure time) required to obtain a required optical density is small, and a high sensitivity system can be designed. More preferably, the light quantity is ² mW-50 W / mm < ² >, More preferably, it is 10 mW-50 W / mm < ² >. Any light source may be used as long as it is as described above, but it can be preferably achieved by using a laser.

  As a laser preferably used for the photosensitive material of the present invention, a gas laser (Ar ion, Kr ion, He—Ne), YAG laser, dye laser, semiconductor laser and the like are preferable. Also, a semiconductor laser and a second harmonic generation element can be used. In addition, if the spectral sensitivity distribution of the halation dye and the photosensitive silver halide in the photosensitive layer is adjusted, the photothermographic material using the structure of the present invention also has a blue to violet light emitting semiconductor laser (peak at wavelengths of 350 nm to 440 nm). And the like having strength) can be used. Examples of the blue to purple light-emitting high-power semiconductor laser include NLHV3000E semiconductor laser manufactured by Nichia Corporation.

  The exposure is preferably performed by laser scanning exposure, but various methods can be adopted as the exposure method. For example, as a first preferred method, there is a method using a laser scanning exposure machine in which the angle formed by the exposure surface of the photosensitive material and the scanning laser beam is not substantially perpendicular.

  Here, “substantially not vertical” is preferably 55 to 88 degrees, more preferably 60 to 86 degrees, and still more preferably 65 to 84 degrees as the angle closest to the vertical during laser beam scanning. , Most preferably 70-82 degrees.

  The beam spot diameter on the photosensitive material exposure surface when the photosensitive material is scanned with the laser beam is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the “shift angle” from the vertical of the laser beam incident angle. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

  Further, as a second method, it is also preferable to perform exposure using a laser scanning exposure machine that emits scanning laser light that is a vertical multi. Compared with a single longitudinal mode scanning laser beam, image quality degradation such as generation of interference fringe-like unevenness is reduced. In order to make a vertical multiplex, methods such as using return light by combining and applying high frequency superposition are preferable. Note that the vertical multi means that the exposure wavelength is not single, and the exposure wavelength distribution is usually 5 nm or more, preferably 10 nm or more. The upper limit of the exposure wavelength distribution is not particularly limited, but is usually about 60 nm.

  Furthermore, as a third aspect, it is also preferable to form an image by scanning exposure using two or more laser beams. As such an image recording method using a plurality of laser beams, it is used in an image writing means of a laser printer or a digital copying machine for writing an image for each line by one scanning because of a demand for high resolution and high speed. For example, Japanese Patent Laid-Open No. 60-166916 is known. This is a method in which laser light emitted from a light source unit is deflected and scanned by a polygon mirror and imaged on a photoconductor via an fθ lens or the like. This is in principle the same laser scanning optics as a laser imager or the like. Device.

  The image formation of laser light on the photoconductor in the image writing means of laser printers and digital copiers is for the purpose of writing images line by line in one scan, and one line from the image formation position of one laser light. The next laser beam is imaged by shifting. Specifically, the two light beams are close to each other on the image plane in the sub-scanning direction at an order of several tens of μm, and the print density is 400 dpi (dpi is the number of dots per inch = 2.54 cm). The sub-scanning direction pitch of the two beams is 63.5 μm, and 42.3 μm at 600 dpi.

  Unlike the method of shifting the resolution in the sub-scanning direction as described above, in the present invention, it is preferable to form an image by condensing two or more lasers at the same place on the exposure surface while changing the incident angle. At this time, the exposure energy on the exposure surface when writing with one ordinary laser beam (wavelength λ [nm]) is E, and N laser beams used for exposure have the same wavelength (wavelength λ [nm]). In the case of the same exposure energy (En), it is preferable that the range is 0.9 × E ≦ En × N ≦ 1.1 × E. By doing so, energy is secured on the exposure surface, but the reflection of each laser beam to the photosensitive layer is reduced because the exposure energy of the laser is low, and the occurrence of interference fringes is suppressed.

  In the above description, a plurality of laser beams having the same wavelength as λ are used. However, ones having different wavelengths may be used. In this case, it is preferable that (λ−30) <λ1, λ2,... Λn ≦ (λ + 30) with respect to λ [nm].

In the above-described image recording methods of the first, second, and third aspects, the laser used for scanning exposure is generally well-known solid laser such as ruby laser, YAG laser, glass laser; Ne laser, Ar ion laser, Kr ion laser, CO ₂ laser, CO laser, He—Cd laser, N ₂ laser, excimer laser and other gas lasers; InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP Semiconductor lasers such as ₂ lasers and GaSb lasers; chemical lasers, dye lasers, etc. can be selected and used in a timely manner according to the application, but among these, semiconductors with a wavelength of 600 to 1200 nm due to maintenance and light source size problems laser It preferred to use a laser beam with. In the laser used in a laser imager or laser image setter, the beam spot diameter on the exposed surface of the material when scanned with a photothermographic material is generally 5 to 75 μm as the minor axis diameter, and as the major axis diameter. The laser beam scanning speed can be set to an optimum value for each photothermographic material depending on the sensitivity and laser power at the laser oscillation wavelength unique to the photothermographic material.

[Development processing]
In the present invention, from the viewpoint of speeding up, it is necessary to correspond to an embodiment in which exposure processing and heat development processing are performed simultaneously. In order to perform the exposure process and the thermal development process at the same time, that is, to start development on a part of the sheet that has already been exposed while exposing a part of the sheet photosensitive material, an exposure unit and a development unit that perform the exposure process The distance between the two is preferably 0 to 50 cm, and this makes the series of processing time for exposure and development extremely short. The preferable range of this distance is 3 to 40 cm, more preferably 5 to 30 cm. Here, the exposure part refers to a position where light from an exposure light source is irradiated to the photothermographic material, and the development part refers to a position where the photothermographic material is heated for the first time for heat development.

  In addition, the conveyance speed in the heat development part of a photosensitive material is 20-200 mm / sec, Especially preferably, it is 30-150 mm / sec. By setting the conveyance speed within this range, density unevenness during heat development can be improved, and the processing time can be shortened.

  Hereinafter, the form of the thermal development apparatus used in the present invention will be described with reference to the drawings.

  FIG. 1 is a side view schematically showing a main part of a heat development apparatus according to a preferred embodiment. As shown in FIG. 1, a heat development apparatus 40 according to a preferred embodiment includes an EC surface in which a photothermographic material is applied on one side of a sheet-like support base made of PET or the like, and an EC surface. A latent image is formed on the EC surface with the laser light L from the optical scanning exposure unit 55 while carrying the sub-scanning conveyance of the film F having the BC surface on the opposite support substrate side, and then the film F is formed on the BC surface side. The latent image is visualized by heating and developing from above, transported upward through the curved transport path, and discharged.

  The heat developing device 40 is provided in the vicinity of the bottom of the apparatus housing 40a, and a film storage unit 45 that stores a large number of unused films F, and a pickup roller that picks up and conveys the uppermost film F in the film storage unit 45. 46, a conveyance roller pair 47 for conveying the film F from the pickup roller 46, and a curved surface guide 48 configured to have a curved surface so as to guide and convey the film F from the conveyance roller pair 47 with the conveyance direction substantially reversed. Then, the laser beam L is optically scanned on the film F based on the image data between the conveying roller pair 49a, 49b for conveying the film F from the curved surface guide 48 in the sub-scanning manner, and the conveying roller pair 49a, 49b. And an optical scanning exposure unit 55 that forms a latent image on the EC surface by exposure.

  The thermal developing device 40 further heats the film F on which the latent image is formed from the BC surface side to raise the temperature to a predetermined heat development temperature, and heats the heated film F to a predetermined heat. A heat retaining section 53 that retains the developing temperature, a cooling section 54 that cools the heated film F from the BC surface side, a densitometer 56 that is disposed on the outlet side of the cooling section 54 and measures the density of the film F, and a density A transport roller pair 57 that discharges the film F from the total 56, and a film placement unit 58 that is provided on the upper surface of the apparatus housing 40a so that the film F discharged by the transport roller pair 57 is placed. With.

  As shown in FIG. 1, in the thermal development device 40, from the bottom of the device housing 40 a upward, the film storage unit 45, the substrate unit 59, the transport roller pairs 49 a and 49 b, the temperature raising unit 50, and the heat retaining unit 53 (upstream). The film storage portion 45 is at the lowermost position, and the substrate portion 59 is provided between the temperature raising portion 50 and the heat retaining portion 53, so that it is not easily affected by heat.

  Further, since the conveyance path from the pair of conveyance rollers 49a and 49b for the sub-scan conveyance to the temperature raising unit 50 is configured to be relatively short, the front end of the film F is exposed while the film F is exposed by the optical scanning exposure unit 55. On the side, heat development heating is performed by the temperature raising unit 50 and the heat retaining unit 53.

  The temperature raising part 50 and the heat retaining part 53 constitute a heating part, and the film F is heated to the heat development temperature and maintained at the heat development temperature. The temperature raising unit 50 includes a first heating zone 51 that heats the film F on the upstream side, and a second heating zone 52 that heats the film F on the downstream side.

  The first heating zone 51 includes a planar heating guide 51b made of a metal material such as aluminum and fixed, a planar heating heater 51c made of a silicon rubber heater or the like in close contact with the back surface of the heating guide 51b, and a heating A plurality of opposing rollers 51a made of silicon rubber or the like, which is arranged to maintain a gap narrower than the film thickness so that the film can be pressed against the fixed guide surface 51d of the guide 51b and whose surface is more thermally insulating than metal or the like; Have

  The second heating zone 52 includes a planar heating guide 52b made of a metal material such as aluminum and fixed, a planar heating heater 52c made of a silicon rubber heater or the like in close contact with the back surface of the heating guide 52b, A plurality of opposed rollers 52a made of silicon rubber or the like, which is arranged to maintain a gap narrower than the film thickness so that the film can be pressed against the fixed guide surface 52d of the guide 52b and whose surface is more thermally insulating than metal or the like, and Have

  The heat retaining section 53 is configured on the surface of the heating guide 53b, a heating guide 53b made of a metal material such as aluminum, a planar heating heater 53c made of a silicon rubber heater or the like closely adhered to the back surface of the heating guide 53b, and the like. And a guide portion 53a made of a heat insulating material or the like disposed so as to face the fixed guide surface 53d so as to have a predetermined gap (slit) d. The heat retaining unit 53 is configured in a planar manner on the temperature raising unit 50 side continuously with the second heating zone 52, and is configured in a curved surface with a predetermined curvature from the middle toward the upper part of the apparatus.

  In the first heating zone 51 of the temperature raising unit 50, the film F conveyed by the conveyance roller pairs 49a and 49b from the upstream side of the temperature raising unit 50 is fixed to the fixed guide surface 51d by each counter roller 51a that is rotationally driven. By being pressed, the BC surface comes into close contact with the fixed guide surface 51d and is conveyed while being heated.

  Similarly, in the second heating zone 52, the BC surface is fixed by the film F conveyed from the first heating zone 51 being pressed against the fixed guide surface 52d by the rotationally driven counter rollers 52a. It is conveyed while being in close contact with the guide surface 51d and being heated.

  It should be noted that a concave portion opened in a V shape may be provided between the second heating zone 52 and the heat retaining portion 53 of the temperature raising portion 50, and foreign matter from the temperature raising portion 50 may be contained in the concave portion. It is possible to prevent foreign matter from the temperature raising unit 50 from being brought into the heat retaining unit 53 by dropping into the heat retaining unit 53.

  In the heat retaining section 53, the film F conveyed from the second heating zone 52 is heated by the heat from the heating guide 53b in the gap d between the fixed guide surface 53d of the heating guide 53b and the guide section 53a (heat retaining). ) Is passed through the gap d by the conveying force of the opposing roller 52a on the second heating zone 52 side. At this time, the film F is conveyed while gradually changing the direction from the horizontal direction to the vertical direction in the gap d, and heads toward the cooling unit 54.

  In the cooling unit 54, the film F conveyed from the heat retaining unit 53 in the substantially vertical direction is brought into contact with the cooling guide surface 54c of the cooling plate 54b made of a metal material or the like by the opposing roller 54a and cooled from the vertical direction. The direction of the film F is gradually changed to the film mounting portion 58 and conveyed in an oblique direction. The cooling effect can be increased by making the cooling plate 54b into a heat sink structure with fins. A part of the cooling plate 54b may have a heat sink structure with fins.

  The cooled film F coming out of the cooling unit 54 is subjected to density measurement by a densitometer 56, conveyed by a conveyance roller pair 57, and discharged to a film placement unit 58. The film placing unit 58 can temporarily place and place a plurality of films F.

  As described above, in the heat development apparatus 40 of FIG. 1, the film F has the BC surface facing the fixed guide surfaces 51d, 52d, 53d in the heated state in the temperature raising portion 50 and the heat retaining portion 53, and the photothermographic material. The coated EC surface is conveyed in an open state. In the cooling unit 54, the film F is conveyed with the BC surface contacting the cooling guide surface 54c and cooled, and the EC surface coated with the heat developing material is opened. Moreover, the film F is conveyed by the opposing rollers 51a and 52a so that the passage time of the temperature raising unit 50 and the heat retaining unit 53 is 10 seconds or less. Therefore, the heating time from temperature increase to heat retention is also 10 seconds or less.

  As described above, according to the heat development apparatus 40 of FIG. 1, the heating guides 51 b and 52 b and the plurality of opposed rollers that press the film F against the heating guides 51 b and 52 b in the temperature raising unit 50 that requires uniform heat transfer. Since the film F is conveyed while ensuring contact heat transfer by bringing the film F into close contact with the fixed guide surfaces 51d and 52d by 51a and 52a, the entire surface of the film is heated uniformly and the temperature rises uniformly. A high quality image with reduced density unevenness.

  In addition, after the temperature is raised to the heat development temperature, the heat retaining portion 53 conveys the film to the gap d between the fixed guide surface 53d of the heating guide 53b and the guide portion 53a, and in particular without closely contacting the fixed guide surface 53d. Even if heating is performed in the gap d (direct heat contact with the fixed guide surface 53d and / or heat transfer by contact with the surrounding high-temperature air), the film temperature is predetermined with respect to the developing temperature (for example, 123 ° C.). Within the range (for example, 0.5 ° C.). Thus, regardless of whether the film is conveyed along the wall surface of the heating guide 53b or the curved surface guide 53a in the gap d, the film temperature difference is less than 0.5 ° C., and a uniform heat retaining state can be maintained. There is almost no possibility of density unevenness in the finished film. For this reason, since it is not necessary to provide driving parts, such as a roller, in the heat retention part 53, score reduction can be achieved.

  Furthermore, since the heating time of the film F is 10 seconds or less, a rapid heat development process can be realized, and the heat retaining portion 53 extending in the horizontal direction from the temperature raising portion 50 becomes a curved surface in the middle and vertically. Since the film F is discharged to the film mounting unit 58 with the direction of the film F being substantially reversed by the cooling unit 54, the cooling unit 54 has a predetermined curvature according to the apparatus layout. It is possible to cope with downsizing of the installation area and downsizing of the entire device.

  In conventional large machines, the film was heated to the developing temperature and the heat-retaining function after the temperature was raised had the same heating and transport mechanism as the temperature-raising part. As a result, unnecessary parts were used. However, the increase in the number of parts and cost increases, and in the conventional small machines, it is difficult to guarantee heat transfer at the time of temperature rise, so there is a problem of uneven density, and it is difficult to guarantee high image quality. According to a preferred embodiment, both of the problems can be solved by separately performing the heat development process in the temperature raising unit 50 and the heat retaining unit 53.

  In addition, the film F is heated from the BC side with the temperature developing unit 50 and the heat retaining unit 53 with the EC surface coated with the photothermographic material open, so that the thermal development process can be performed in a rapid process of 10 seconds or less. When performing, since the solvent (moisture, organic solvent, etc.) contained in the film F to be heated and volatilized (evaporated) is dispersed at the shortest distance by opening the EC surface side, the heating time (volatilization time) is short. However, even if there is a part where the contact between the film F and the fixed guide surfaces 51d and 52d is partially poor, the thermal diffusion effect due to the PET base on the BC surface causes a contact property. The temperature difference from the good portion is relaxed, and as a result, the density difference hardly occurs, so that the density can be stabilized and the image quality is stabilized. In general, considering the heating efficiency, the EC surface side heating was considered to be better, but the thermal conductivity of PET of the support substrate of the film F was 0.17 W / m ° C., and the thickness of the PET base was 170 μm. Considering the fact that it is before and after, it is preferable that the time delay is slight and can be easily offset by increasing the capacity of the heater and the like, and the effect of reducing the contact unevenness can be expected.

  Further, the solvent (water, organic solvent, etc.) in the film F is going to volatilize (evaporate) even after leaving the heat retaining part 53 and reaching the cooling part 54. Since the EC surface is in an open state, the solvent (moisture, organic solvent, etc.) is not trapped and is volatilized for a longer time, so the image quality is more stable. Thus, the cooling time cannot be ignored during the rapid processing, and is particularly effective for the rapid processing with a heating time of 10 seconds or less.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. Unless otherwise specified, “part” in the examples represents “part by mass” and “%” represents “mass%”.

<Preparation of underdrawn support>
Corona discharge treatment is performed on both sides of a biaxially stretched PET film with a blue dye concentration of 0.113 under the condition of 10 W / m 2 · min. It was coated to 0.06 μm and dried at 140 ° C. Subsequently, a back surface side undercoat upper layer coating solution having the following composition was coated to a dry film thickness of 0.2 μm and then dried at 140 ° C. . On the other side, an image forming surface side undercoat lower layer coating solution having the following composition is coated to a dry film thickness of 0.25 μm, followed by an image forming surface side undercoat upper layer having the following composition. The coating solution was applied to a dry film thickness of 0.06 μm and then dried at 140 ° C. These were heat-treated at 140 ° C. for 2 minutes to obtain an underdrawn support.
(Back surface side undercoat lower layer coating solution)
Copolymer polymer latex of styrene / glycidyl methacrylate / butyl acrylate (20/20/40) (solid content 30%) 16.0 g
Copolymer polymer latex of styrene / butyl acrylate / hydroxymethyl methacrylate (25/45/30) (solid content 30%) 4.0 g
91 g of tin oxide sol (solid content 10%, synthesized by the method described in JP-A-10-059720)
Surfactant for undercoat layer 0.5g
Distilled water was added to make 1000 ml, and a coating solution was obtained.
(Back surface side undercoat upper layer coating solution)
Modified water-based polyester for back layer * (solid content 18%) 215.0 g
0.4 g of surfactant for undercoat layer
Spherical silica matting agent (Seahoster KE-P50: manufactured by Nippon Shokubai Co., Ltd.) 0.3 g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

Surfactant for undercoat layer: 2,4- (C ₉ H ₁₉ ) ₂ —C ₆ H ₃ — (CH ₂ CH ₂ O) ₁₂ SO ₃ Na
<Synthesis of modified aqueous polyester for back layer>
In a polymerization reaction vessel, dimethyl terephthalate 35.4, dimethyl isophthalate 33.63 parts, 5-sulfo-isophthalic acid dimethyl sodium salt 17.92 parts, ethylene glycol 62 parts, calcium acetate monohydrate 0.065 parts, After adding 0.022 parts of manganese acetate tetrahydrate and conducting a transesterification reaction while distilling methanol at 170-220 ° C. under a nitrogen stream, 0.04 parts of trimethyl phosphate and trioxide as a polycondensation catalyst 0.04 parts of antimony and 6.8 parts of 1,4-cyclohexanedicarboxylic acid were added, and an approximately theoretical amount of water was distilled off at a reaction temperature of 220 to 235 ° C. for esterification. Thereafter, the reaction system was further depressurized and heated for about 1 hour and finally subjected to polycondensation at 280 ° C. and 133 Pa or less for about 1 hour to obtain a modified aqueous polyester precursor. The intrinsic viscosity of the precursor was 0.33.

  850 ml of pure water was put into a 2 L three-necked flask equipped with a stirring blade, a reflux condenser, and a thermometer, and 150 g of the precursor was gradually added while rotating the stirring blade. The mixture was stirred at room temperature for 30 minutes, heated to an internal temperature of 98 ° C. over 1.5 hours, and heated and dissolved at this temperature for 3 hours. After completion of the heating, the mixture was cooled to room temperature over 1 hour and allowed to stand overnight to prepare a precursor solution having a solid concentration of 15%.

1900 ml of the precursor solution was placed in a 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer, and a dropping funnel, and the internal temperature was heated to 80 ° C. while rotating the stirring blade. Into this, 6.52 ml of a 24% aqueous solution of ammonium peroxide was added, and a monomer mixture (28.5 g of glycidyl methacrylate, 21.4 g of ethyl acrylate, 21.4 g of methyl methacrylate) was dropped over 30 minutes. The reaction was continued for another 3 hours. Then, it cooled to 30 degrees C or less, and filtered, and prepared the solution of the modified aqueous | water-based polyester for back layers with a solid content concentration of 18%.
(Coating solution for undercoat on the image forming side)
Copolymer latex of styrene / acetoacetoxyethyl methacrylate / glycidyl methacrylate / butyl acrylate (40/40/20 / 0.5) (solid content 30%) 70 g
Surfactant for undercoat layer 0.3g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

(Image forming surface side undercoat upper layer coating solution)
Modified water-based polyester for image forming surface * (solid content 18%) 80.0 g
0.4 g of surfactant for undercoat layer
Spherical silica matting agent (Seahoster KE-P50: manufactured by Nippon Shokubai Co., Ltd.) 0.3 g
Distilled water was added to make 1000 ml, and a coating solution having a solid content concentration of 0.5% was obtained.

<Synthesis of modified aqueous polyester for image forming surface>
A modified aqueous polyester for a back layer, except that the modified aqueous polyester precursor solution was 1,800 ml, the monomer mixture composition was 31 g of styrene, 31 g of acetoacetoxyethyl methacrylate, 61 g of glycidyl methacrylate, and 7.6 g of butyl acrylate. Similarly, a solution of a modified aqueous polyester for image forming surface having a solid content concentration of 18% was prepared.

<Preparation of silver halide-containing aliphatic carboxylic acid silver salt emulsion for photosensitive layer>
<Preparation of silver halide emulsion>
(Solution A)
Phthalated gelatin (phthalated modification rate 99%) 66.2g
Surfactant AO-1 (10% methanol aqueous solution) 10 ml
Potassium bromide 0.32g
Water finish 5429ml AO-1: HO (CH 2 CH 2 O) n (CH (CH 3) CH 2 O) 17 (CH 2 CH 2 O) m H (m + n = 5~7)
(Solution B)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(Solution C)
Potassium bromide 51.55g
Potassium iodide 1.47g
Finish to 660 ml with water (Solution D)
Potassium bromide 154.9g
4.41 g of potassium iodide
15 ml of iron (II) hexacyanide (0.5% solution)
0.93 ml potassium hexachloroiridate (III) (1% solution)
Finish to 1982 ml with water (Solution E)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount (solution F)
Potassium hydroxide 0.71g
Finish to 20 ml with water (Solution G)
56% aqueous acetic acid solution 10.0ml
(Solution H)
Anhydrous sodium carbonate 1.16g
Finish to 107 ml with water Using a mixing stirrer shown in Japanese Patent Publication No. 58-58288, while mixing 1/4 of solution B in solution A and the total amount of solution C at 35 ° C. and pAg 8.09, simultaneous mixing The nucleation was performed by adding 4 minutes and 45 seconds by the method. After 1 minute, the entire amount of Solution F was added. During this time, the solution E was used appropriately for the adjustment of pAg. After the elapse of 6 minutes, 3/4 amount of the solution B and the whole amount of the solution D were added over 14 minutes and 15 seconds by the simultaneous mixing method while controlling the temperature at 35 ° C. and pAg 8.09. After stirring for 5 minutes, the temperature was lowered to 30 ° C., the entire amount of Solution G was added, and the silver halide emulsion was allowed to settle. The supernatant was removed leaving 2000 ml of the sediment, 10 liters of water was added, and after stirring, the silver halide emulsion was sedimented again. The remaining portion of 1500 ml was left, the supernatant was removed, 10 liters of water was further added, and after stirring, the silver halide emulsion was precipitated. After leaving 1500 ml of the sedimented portion and removing the supernatant, solution H was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 100 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount was 1161 g per mole of silver to obtain a photosensitive silver halide emulsion.

  This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 0.043 μm and a [100] face ratio of 92%.

<Preparation of organic polymer for dispersion>
A 0.5 liter four-necked separable flask is equipped with a dropping device, thermometer, nitrogen gas inlet tube, stirring device and reflux condenser, and 50 g of methyl ethyl ketone (MEK), 16 g of diacetone acrylamide, methoxypolyethylene glycol monomethacrylate (Nippon Yushi Co., Ltd .: Blenmer PME-400) 23 g, stearoxy polyethylene glycol monomethacrylate (Nippon Yushi Co., Ltd .: Blenmer PSE-400) 23 g, and further lauryl peroxide 0.12 g were charged and heated to 80 ° C. Further, a solution obtained by dissolving 38 g of Ni-propyl acrylamide in 43 g of MEK was dropped into a separable flask over 2 hours. Thereafter, the temperature was raised over 1 hour, and when the mixture was refluxed, a solution obtained by dissolving 0.17 g of lauryl peroxide in 33 g of MEK was dropped into the flask over 2 hours and reacted at the same temperature for further 3 hours. . Thereafter, a solution obtained by dissolving 0.33 g of methylhydroquinone in 107 g of MEK was added, and after cooling, an organic polymer solution for dispersion of 30% polymer was obtained. The molecular weight was about 55,000 in terms of polystyrene-equivalent weight average molecular weight by GPC (gel permeation chromatography). Subsequently, the polymer solution was dropped into a sufficient amount of water, the supernatant was removed, and the polymer solid content was taken out.

<Preparation of hydrophobic silver halide grain dispersion>
67 g of methanol was added to 7.5 g of the organic polymer solid content for dispersion and dissolved with stirring at 45 ° C. for 30 minutes. Thereto, 25 g of the silver halide emulsion adjusted to 45 ° C. was added dropwise over 2 minutes, and the mixture was further stirred for 30 minutes. After the temperature of this liquid is lowered to 30 ° C., the liquid left for 30 minutes is separated into two layers. The supernatant of the liquid was removed, 230 g of MEK was added to the remaining liquid, and distilled under reduced pressure until the water content in the liquid became less than 10%. Finally, MEK was added so that the total amount was 157 g. Further, 50 g of a solution obtained by dissolving 5 g of polyvinyl butyral resin A having a polymerization degree shown in Table 1 in MEK was added to obtain 207 g of a hydrophobic silver halide grain dispersion. When the polyvinyl butyral resin A was not added, 50 g of MEK was added to obtain 207 g of a hydrophobic silver halide grain dispersion.

<Preparation of powdered aliphatic carboxylic acid silver salt>
An aliphatic carboxylic acid silver salt was prepared using the mixing apparatus described in JP-A-2000-198757. In 4,720 ml of pure water, 130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved at 80 ° C. Next, 540.2 ml of a 1.5 mol / L potassium hydroxide aqueous solution was added and 6.9 ml of concentrated nitric acid was added, followed by cooling to 55 ° C. to obtain a fatty acid potassium solution. While maintaining the temperature of the fatty acid potassium solution at 55 ° C., 45.3 g of the photosensitive silver halide emulsion and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 702.6 ml of a 1 mol / L silver nitrate aqueous solution was added over 2 minutes, and the mixture was stirred for 10 minutes to obtain an aliphatic carboxylic acid silver salt dispersion. Thereafter, the obtained aliphatic carboxylic acid silver salt dispersion was transferred to a water-washing vessel, deionized water was added and stirred, and then allowed to stand to float and separate the aliphatic carboxylic acid silver salt dispersion. Was removed. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 2 μS / cm, and centrifugal dehydration was carried out. The resulting cake-like aliphatic carboxylic acid silver salt was then used as an airflow dryer flashjet. Using a dryer (manufactured by Seishin Enterprise Co., Ltd.), a dried powdered aliphatic carboxylic acid silver salt was obtained by drying until the water content became 0.1% according to the operating conditions of nitrogen gas atmosphere and dryer inlet hot air temperature. An infrared moisture meter was used to measure the water content of the aliphatic carboxylic acid silver salt composition.

<Preparation of aliphatic carboxylic acid silver salt dispersion emulsion>
49 g of polyvinyl butyral (Sekisui Chemical Co., Ltd .: ESREC B / BL-SHP) dissolved in 1,300 g of MEK and stirred with a dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN 500 g of powdered aliphatic carboxylic acid silver salt Was added gradually and mixed well to prepare a preliminary dispersion. After the total amount of powdered aliphatic carboxylic acid silver salt was added, stirring was performed at 1,500 rpm for 15 minutes. This pre-dispersed liquid is a media type disperser DISPERMAT filled with 80% of the internal volume of 0.5 mm zirconia beads (Toray Industries, Inc .: Treceram) so that the residence time in the mill is 1.2 minutes using a pump. An aliphatic carboxylic acid silver salt dispersion emulsion was prepared by supplying to SL-C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 9 m / s. The solid content concentration of the obtained aliphatic carboxylic acid silver salt dispersion emulsion was about 27%.

<Coating of photosensitive layer, surface protective layer, and back layer>
A photosensitive layer is provided on the undercoat of the undercoated support on the photosensitive layer side so that the total silver amount is 1.6 g / m ² , and the wet weight is 23 g / m ² on the photosensitive layer. A surface protective layer was applied in multiple layers. Subsequently, a back layer was applied on the opposite photosensitive layer surface undercoat so that the wet weight was 25 g / m ² . The drying was performed at 60 ° C. for 15 minutes. A heat-developable photosensitive material was obtained by carrying out heat treatment at 79 ° C. for 10 minutes while conveying the sample coated on both sides.

<Preparation of photosensitive layer coating solution>
The same amount of MEK is added to 1,647 g of the aliphatic carboxylic acid silver salt dispersion emulsion, and the mixture is kept at 18 ° C. with stirring, and 1.2 g of bis (dimethylacetamide) dibromobromate (11% methanol solution) is added. And stirred for 1 hour. Subsequently, 15.1 g of calcium bromide (11% methanol solution) was added and stirred for 30 minutes. Further, an infrared sensitizing dye solution was added and stirred for 1 hour, and then the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While keeping the temperature at 13 ° C., 240 g of polyvinyl butyral resin B and C powder shown in Table 1 were added and dissolved. After confirming dissolution, 19.8 g of tetrachlorophthalic acid (13% MEK solution) was added, and the following additives were added at intervals of 15 minutes while continuing stirring to obtain a photosensitive layer coating solution.

Phthalazine 12.4g
Desmodur N3300 (manufactured by Mobay: polyfunctional aliphatic isocyanate)
17.6g
Leuco dye-1 1.4g
0.6 g of leuco dye-2
Antifoggant solution below Developer solution below <Preparation of infrared sensitizing dye solution>
400 mg of infrared sensitizing dye-1, 400 mg of infrared sensitizing dye-2, 130 mg of 5-methyl-2-mercaptobenzimidazole, 21.5 g of 2-chloro-benzoic acid, 2.5 g of sensitizing dye solubilizer An infrared sensitizing dye solution was prepared by dissolving in 135 g of MEK.

<Preparation of developer solution>
0.35 mol of the reducing agent shown in Table 1, 9 g of l, 4-methylphthalic acid, and 0.7 g of dye-A were dissolved in MEK and finished to 800 g to obtain a developer solution.

<Preparation of antifoggant solution>
11.6 g of tribromomethylsulfonylpyridine was dissolved in MEK and finished to 180 g to obtain an antifoggant solution.

(Surface protective layer coating solution)
MEK 1056g
Cellulose acetate propionate (Eastman Chemical Co .: CAP141-
20) 148g
6 g of polymethyl methacrylate (Rohm and Haas, Paraloid A21)
170 g of mat dispersion (silica having an average particle size of 4 μm with a dispersion degree of 10%, solid content concentration of 1.7%)
Crosslinking agent (CH ₂ ═CHSO ₂ CH ₂ ) ₂ CH (OH) 3.6 g
Benzotriazole 2g
Fluorine-based surfactant C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₃ C ₉ F ₁₇ 5.4 g
Fluorine-based surfactant LiO ₃ S (CF ₂ ) ₃ SO ₃ Li 0.12 g
(Back layer coating solution)
MEK 1350g
121 g of cellulose acetate propionate (manufactured by Eastman Chemical Co .: CAP482-20)
Dye-A 0.23g
Dye-B 0.62g
Fluorine-based acrylic copolymer (Daikin Kogyo Co., Ltd .: Optoflon FM450) 1.21 g
Amorphous saturated copolyester (Toyobo Co., Ltd .: Byron 240P) 18.1 g
Ethylenediamine bis stearamide 2.0g
Surfactant C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₃ C ₉ F ₁₇ 5.21 g
Surfactant LiO ₃ S (CF ₂ ) ₃ SO ₃ Li 0.81 g

<Evaluation of sample>
Evaluation is performed with the laser imager shown in FIG. 1 (mounted with a 786 nm semiconductor laser having a maximum output of 50 mW) and thermal development (51, 52, and 53 in FIG. 1 are temperatures shown at 100 ° C., 127 ° C., and 127 ° C., respectively). And transported so that they contact each other for 2 seconds, 2 seconds, and 6 seconds for a total of 10 seconds), and the obtained images were evaluated with a densitometer. Here, “thermal development at the same time as exposure” is a sheet of photosensitive material made of a photothermographic material, and development is started on a part of the sheet that has already been exposed while being partially exposed. Means that. The distance between the exposed part and the developing part was 12 cm, and the linear velocity at this time was 30 mm / second. Further, the conveyance speed from the photosensitive material supply unit to the image exposure unit, the conveyance rate at the image exposure unit, and the conveyance rate at the heat development unit were each 30 mm / second. The exposure was performed in a stepped manner while reducing the exposure energy amount by log E0.05 step by step from the maximum output.

《Fog density, highest density》
The density of the formed image obtained as described above was measured using a densitometer, and a characteristic curve consisting of a horizontal axis—exposure amount and a vertical axis—density was created. In the characteristic curve, the fog density (minimum density) and the maximum density were measured. Note that the sensitivity and the maximum density are expressed as relative values with each of the samples 1 being 100.

<Raw preservation>
The difference between the fog density value after the unexposed sample was stored in an environment of 40 ° C. for 20 days and the fog density value of the evaluation sample was shown. The image storability showed the range of decrease in the maximum density portion when the developed evaluation sample was stored at 50 ° C. for 5 days in a light-shielded state.

<Application stability>
The amount of coated silver in the sample is measured by X-ray diffraction measurement. An arbitrary portion of each level was measured at five locations, and the standard deviation was calculated from the following formula. A sample having a standard deviation of less than 1 was evaluated as having sufficiently good coating stability.

Standard deviation = [{- sum of (coated silver amount coated silver amount average value) 2} / 5] ^1/2

  As shown in Table 1, by using the configuration of the present invention, the maximum density of 3.5 or more can be obtained even by short-time heat development while the fog density is low fog of 0.16 or less, and at the time of storage Thus, it is possible to provide a photothermographic material which is almost free from fogging and excellent in stability of a silver image after heat development.

It is a side view which shows roughly the principal part of the heat development apparatus suitable for using for this invention.

Explanation of symbols

40a Device housing 45 Film storage unit 46 Pickup roller 47 Conveying roller pair 48 Curved guide 49a, 49b Conveying roller pair 50 Temperature rising unit 51 First heating zone 52 Second heating zone 53 Heat retaining unit 54 Cooling unit 51a, 52a Opposing Rollers 51b, 52b, 53b Heating guides 51c, 52c Heating heaters 51d, 52d, 53d Fixed guide surface 53a Curved surface guide 53b Heating guide 54b Cooling plate 54c Cooling guide surface 55 Optical scanning exposure unit 56 Densitometer 57 Transport roller pair 58 Film placement Part 59 Substrate part F Film (photothermographic material)
d Gap (slit part)

Claims (6)

In a photothermographic material having a photosensitive layer containing a photosensitive emulsion, a reducing agent, and a binder on a support, the photosensitive layer contains silver halide fine particles in which a hydrophilic natural polymer dispersant is dispersed as a protective colloid. Hydrophobic protective colloid fine particle dispersion prepared by adding a dispersant having a functional group having an affinity for the hydrophilic group of the protective colloid to an aqueous dispersion, and a photosensitive layer having a polymerization degree of 600 to A photothermographic material comprising a 3,000 binder and a binder having a polymerization degree of 100 to 400. 2. The photothermographic material according to claim 1, wherein the binder contains two or more binders having a polymerization degree of 600 to 3,000. 3. The photothermographic material according to claim 1, wherein the binder is a polyvinyl acetal resin. The photothermographic material according to claim 1, wherein the dispersant is an organic polymer. The hydrophobic protective colloid fine particle dispersion was prepared by adding a dispersant to an aqueous dispersion of silver halide fine particles to precipitate the silver halide fine particles, and dispersing the precipitate in a hydrophobic solvent. The photothermographic material according to claim 1, wherein the photothermographic material is a photothermographic material. The photothermographic material according to claim 1, wherein the reducing agent is represented by the following general formula (1).

[Wherein, R ₁ represents a hydrogen atom or a substituent, and R ₂ and R ₃ each represents a branched alkyl group having 3 to 8 carbon atoms. A ₁ and A ₂ each represent a hydroxyl group or a group that can be deprotected to form a hydroxyl group, and n and m each represents an integer of 3 to 5. ]

Images