JP2007137858A - Method for producing nitrogen-containing heterocyclic compound silver salt particle and heat-developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing particles of a nitrogen-containing heterocyclic compound silver salt of new structure, and to provide a heat-developable photosensitive material excellent in direct storage stability and image storage stability using the particles. <P>SOLUTION: The method for producing the nitrogen-containing heterocyclic compound silver salt particles comprises the following process. The nitrogen-containing heterocyclic compound and a water-soluble silver compound are mixed together to form particles followed by removing a byproduct salt formed at a temperature of 30°C or higher. The heat-developable photosensitive material is such that at least one surface of a substrate is borne with at least a photosensitive silver halide, a nonphotosensitive organosilver salt and a reducing agent, wherein the nonphotosensitive organosilver salt consists of the nitrogen-containing heterocyclic compound silver salt particles produced by the method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a silver salt particle of a nitrogen-containing heterocyclic compound, particularly a silver salt particle of a nitrogen-containing heterocyclic compound that does not contribute to the image density immediately after heat development, and a nitrogen-containing heterocyclic compound produced thereby. The present invention relates to a photothermographic material containing silver salt particles.

  In recent years, in the medical diagnostic film field and the photoengraving film field, it is strongly desired to reduce the amount of processing waste liquid from the viewpoint of environmental protection and space saving. Therefore, heat as a medical diagnostic film and a photoengraving film that can be efficiently exposed by a laser image setter or a laser imager and can form a clear black image having high resolution and sharpness. There is a need for techniques relating to developed image recording materials. According to these heat-developable image recording materials, a heat-development processing system that does not require solution-based processing chemicals and that is simpler and does not impair the environment can be supplied to customers.

  There are similar requirements in the field of general image recording materials, but medical diagnostic images in particular require fine depiction, so they require high image quality with excellent sharpness and graininess, and ease of diagnosis. From the viewpoint, a cool black image is preferred. At present, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed as general image forming systems, but none of them are satisfactory as a medical image output system.

On the other hand, thermal imaging systems using organic silver salts are disclosed in, for example, the specifications of U.S. Pat. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials), 8th edition, J. Sturge. (Walworth, edited by A. Shepp, Chapter 9, page 279, 1989).
In particular, the photothermographic material generally contains a catalytically active amount of a photocatalyst (for example, silver halide), a reducing agent, a reducible silver salt (for example, an organic silver salt), and, if necessary, a toning agent that controls the color tone of silver. And an image forming layer dispersed in a binder matrix. The photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, and a black silver image is formed by an oxidation-reduction reaction between a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure. Therefore, a black silver image is formed in the exposure area.

The reducible silver salt is non-photosensitive and functions as a source of silver ions to form developed silver. As the non-photosensitive organic silver salt, fatty acid silver has been generally used.
Further, it is disclosed that a silver salt of a heterocyclic compound such as mercapto silver or benzotriazole silver is also used as a non-photosensitive silver salt in a photothermographic material (for example, see Patent Document 1).

  On the other hand, it is disclosed that a non-photosensitive silver salt is used for a color photothermographic material. A color photothermographic material is an image in which a photosensitive silver halide, a non-photosensitive organic silver salt, a color developing agent, and a coupler that reacts with an oxidation product of the color developing agent to form a dye are dispersed in a binder matrix. It has a formation layer. The use of a silver salt of a heterocyclic compound as a non-photosensitive organic silver salt in such a color photothermographic material is disclosed (for example, see Patent Document 2). However, the non-photosensitive silver salt disclosed above is a silver salt as a so-called silver ion source necessary for causing the image density obtained immediately after heat development to appear, and contributes to the intended image density of the present application. The purpose and effect were completely different from the silver salt.

  Many conventional photothermographic materials are produced by using an organic solvent such as toluene, methyl ethyl ketone, or methanol as a solvent. However, using an organic solvent as a solvent is disadvantageous in terms of cost not only due to the influence on the human body in the manufacturing process but also due to other factors such as recovery of the solvent.

  Therefore, as a method for producing a photothermographic material using an aqueous medium coating solution that does not cause such a concern, a production method using an aqueous dispersion of a hydrophobic polymer as a binder has been proposed (for example, see Patent Document 3). ). In the aqueous coating method, multilayer multilayer coating is easy, and it has a feature that a layered structure can be configured individually by introducing necessary materials into each layer (see, for example, Patent Document 4).

  A photothermographic material using such an organic silver salt contains all the components necessary for image formation in advance in the film and has a great advantage that an image can be formed only by heating. On the other hand, since these components remain as unreacted components or reaction products even after image formation, there is a problem of deteriorating image storage stability.

It is disclosed that image storage stability is improved by providing a non-photosensitive layer containing a non-photosensitive silver salt as an upper layer of the image forming layer separately from the image forming layer (see, for example, Patent Document 5). ). Organic acid silver salts such as fatty acid silver salts are particularly preferred as the non-photosensitive silver salt added to the non-photosensitive layer, other silver salts of compounds having a mercapto group or thione group, silver salts of compounds having an imino group, etc. Can also be used.
JP 2005-221646 A JP 2003-43648 A Japanese Patent Laid-Open No. 10-10670 JP 11-84573 A JP-A-11-352624

  An object of the present invention is to provide a method for producing silver salt particles of a nitrogen-containing heterocycle compound with high productivity, and particularly a method for producing silver salt particles of a nitrogen-containing heterocycle compound that does not contribute to the image density immediately after development. The present invention further provides a photothermographic material containing silver salt particles of a nitrogen-containing heterocyclic compound produced thereby.

The above problems have been solved by the following means.
<1> A method for producing silver salt particles of a nitrogen-containing heterocyclic compound, wherein the nitrogen-containing heterocyclic compound and a water-soluble silver compound are mixed to form particles, and then particles at a temperature of 30 ° C. or higher. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound, wherein the water-soluble salts produced as a by-product are removed.
<2> A step of removing water-soluble salts by-produced by at least one means selected from a centrifugal filtration method, an ultrafiltration method, a suction filtration method, electrodialysis, and a decantation method at a temperature of 30 ° C. or higher. The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to <1>, wherein one desalting step is performed.
<3> Following the first desalting step, water is added and washed, and the particles are subjected to centrifugal filtration, ultrafiltration, suction filtration, electrodialysis, and decane at a temperature of 30 ° C. or higher. The method for producing silver salt particles of a nitrogen-containing heterocyclic compound as described in <2>, wherein the second desalting step is performed by at least one means selected from the nitration method.
<4> The silver salt of the nitrogen-containing heterocyclic compound according to any one of claims 1 to 3, wherein the silver salt of the nitrogen-containing heterocyclic compound is silver benzotriazole. Production method.
<5> The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to any one of claims 1 to 4, wherein a temperature at which the particles are precipitated is 35 ° C or higher.
<6> The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to any one of <1> to <5>, wherein the temperature for precipitating the particles is 40 ° C. or higher.
<7> The process according to any one of <1> to <5>, wherein the step of mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound to form particles includes at least two steps. The manufacturing method of the silver salt particle | grains of the nitrogen-containing heterocyclic compound of description.
<8> The addition rate of the water-soluble silver compound in the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound is faster in the second step than in the first step. The method for producing silver salt particles of the nitrogen-containing heterocyclic compound according to <7>.
<9> Any one of <1> to <8>, wherein the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound is performed in the presence of a water-soluble binder. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound as described in 1.
<10> The process according to any one of <1> to <9>, wherein the step of mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound to form particles is performed at a temperature of 60 ° C. or higher. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound.
<11> Any one of <1> to <10>, wherein the pH change in the step of mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound to form particles is 3 or less. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound as described in 1.
<12> The nitrogen-containing heterocycle compound and a water-soluble silver compound are mixed to form a seed crystal, and then the seed crystal is grown by adding silver salt particles of the nitrogen-containing heterocycle compound. <1>-<11> The manufacturing method of the silver salt particle | grains of the nitrogen-containing heterocyclic compound of any one of <11>.
<13> The method according to any one of <1> to <12>, wherein an oxidizing agent is added in the step of mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound to form particles. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound.
<14> Any one of <1> to <13>, wherein the nitrogen-containing heterocyclic compound and the water-soluble silver compound are mixed to form particles, and then an adsorbing compound is added to the particles. The manufacturing method of the silver salt particle | grains of the nitrogen-containing heterocyclic compound of item.
<15> A photothermographic material containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent on at least one surface of a support, wherein at least one of the non-photosensitive organic silver salts A photothermographic material, wherein 1 part is silver salt particles of a nitrogen-containing heterocyclic compound produced by the production method according to any one of <1> to <14>.
<16> The photothermographic material according to <15>, wherein the silver salt particles of the nitrogen-containing heterocyclic compound do not substantially contribute to the photothermographic image density.
<17> An image forming layer containing at least the photosensitive silver halide, the fatty acid silver salt, the reducing agent, and a binder on at least one surface of the support, and the image forming layer of the support The photothermographic material according to <15> or <16>, further comprising a non-photosensitive layer containing silver salt particles of the nitrogen-containing heterocyclic compound on the same side.
<18> The ratio of the silver salt of the nitrogen-containing heterocyclic compound to the fatty acid silver salt is 0.5 mol% or more and 50 mol% or less in terms of silver molar ratio. <15> to <17> The photothermographic material according to claim 1.

Silver halide grains used in photographic materials are usually produced by forming water-insoluble silver salt grains by the reaction of a water-soluble silver supply compound and a water-soluble halogen compound in a gelatin solution, and then removing the by-product salts. Is done. This is because when by-product salts are brought into the light-sensitive material, there are adverse effects such as storage stability of the light-sensitive material, photographic performance, or film adhesion failure. As desalting methods, gelatin is gelled by lowering the temperature, then the noodle washing method is performed by extruding into cold water in noodle form and washing with water. Separation methods such as a decantation method (also referred to as a flocculation method) are known which are precipitated by agglomeration of gelatin adsorbed on silver halide, a method of suction filtration, electrodialysis, and silver halide. In the washing process, the protective colloid action of silver halide grains by gelatin functions effectively and conveniently in the washing process, reducing costs in the manufacturing process, and suppressing the aggregation of grains and the occurrence of fogging of silver halide. Washing water is often used as it is without being heated to raise its temperature, including the purpose of maintaining it, and is generally carried out at a low temperature of room temperature or lower.
JP-A-2003-43648 describes a method for preparing a silver salt of a heterocyclic compound that is used in a color photothermographic material and contributes to the image density immediately after development. Similar to the above photosensitive silver halide, a heterocyclic compound aqueous solution and a silver nitrate aqueous solution are mixed in an aqueous gelatin solution to form silver salt particles of the heterocyclic compound. Since the heterocyclic compound has low solubility in water, an aqueous heterocyclic compound solution is prepared by increasing the temperature of the solution to 60 ° C. Here, the temperature and conditions in the water washing step are not specified in detail, but it is common for those skilled in the art to perform desalting and water washing at a temperature as low as room temperature after the grain formation, as in the case of the silver halide grains described above. Understanding. Note that the silver salt particles of the nitrogen-containing heterocyclic compound of the present application do not substantially contribute to the image density immediately after development, and are completely different in use purpose and effect from the above silver salt particles.

As a result of analyzing the problem of the production method for producing silver salt particles of a heterocyclic compound more efficiently, the present inventors have found that the desalting step after the formation of particles reduces the production efficiency. As a result of the analysis of the cause, the silver salt grains of the heterocyclic compound have a lower specific gravity than the silver halide grains. Therefore, the desalting methods generally used in the conventional silver halide require a long time for separation. Turned out to be. Further, for the purpose of suppressing the occurrence of fogging of silver halide and maintaining high sensitivity, the desalting process generally keeps the temperature at a low temperature below room temperature.
As a result of diligent search for a method for desalting silver salt particles of a heterocyclic compound, the inventors of the present invention rapidly settled particles formed by maintaining a high temperature of 30 ° C. or higher after particle formation, and shortened the separation time. As a result, the inventors have reached the invention of the production method of the present invention. Further, it has been found that the silver salt grains of the heterocyclic compound do not have a problem of deterioration of photographic performance due to fogging as in the conventional silver halide even when desalting at such a high temperature. The invention of the development photosensitive material has been reached. In particular, it is excellent as a production method in terms of the time required for the method of the present application in water washing of silver salt particles of the nitrogen-containing heterocyclic compound of the present application that does not contribute to the image density immediately after development, and at the same time, the photosensitive material to which the present application is intended. It has been found that silver salt particles of nitrogen-containing heterocyclic compounds suitable for improving so-called storability such as suppressing fogging changes and developed image changes over time, are provided to the conventional image density involved in development. The silver salt particles of the nitrogen-containing heterocyclic compound that contributed had different effects in terms of cost, fogging or aggregation, and this effect was not easily expected.

  The present invention provides a method for producing silver salt particles of a nitrogen-containing heterocyclic compound and a photothermographic material containing the silver salt particles of a nitrogen-containing heterocyclic compound produced thereby.

Hereinafter, the present invention will be described in detail.
The photothermographic material of the present invention is a photothermographic material containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent on at least one surface of a support, and is non-photosensitive. The organic silver salt contains silver salt particles of the aforementioned nitrogen-containing heterocyclic compound.
Preferably, it has an image forming layer containing at least the photosensitive silver halide, fatty acid silver salt, the reducing agent and a binder, and the above nitrogen-containing heterocycle is formed on the same side of the support as the image forming layer. It has a non-photosensitive layer containing silver salt particles of the compound.

1. Silver salt particles of nitrogen-containing heterocyclic compounds (nitrogen-containing heterocyclic compounds)
The silver salt of the nitrogen-containing heterocyclic compound used in the present invention is a silver salt formed by the combination of nitrogen and silver ion of the nitrogen-containing heterocyclic compound. Examples of the nitrogen-containing heterocyclic compound include azoles and oxazoles. , Thiazoles, thiazolines, imidazoles, diazoles, pyridines, indolizines and triazines, but are not limited thereto. More preferred are indolizines, imidazoles and azoles. Preferred as azoles are triazole, tetrazole, and derivatives thereof. More preferred are benzimidazole and derivatives thereof, and benzotriazole and derivatives thereof. As the indolizines, triazaindolizine derivatives are preferred.
Further, typical nitrogen-containing heterocyclic compounds are listed below, but are not limited to these compounds. For example, 1,2,4-triazole, or benzotriazole and derivatives thereof, benzotriazole, methylbenzotriazole, and 5-chlorobenzotriazole are preferable. Further, 1H-tetrazole compounds such as phenylmercaptotetrazole described in US Pat. No. 4,220,709 (de Mauriac), imidazoles and imidazoles described in US Pat. No. 4,260,677 (Windslow et al.) Derivatives, etc., and benzimidazole and nitrobenzimidazole are preferred. The triazaindolizine derivative is preferably 5-methyl-7-hydroxy-1,3,5-triazaindolizine, but is not limited thereto.
The silver salt particles of the nitrogen-containing heterocyclic compound in the present invention are preferably a silver salt of a benzotriazole compound or a derivative thereof, more preferably a silver salt of benzotriazole.

(Method for preparing silver salt particles of nitrogen-containing heterocyclic compound)
As a preparation process of this invention, you may consist of a base | substrate part formation process ((a) process) and the outline part formation process ((b) process) which follows it. Basically, only step (a) may be performed, but it is more preferable to perform step (b) following step (a). (B) A process is a core-shell structure and an epitaxial joining process, and any process may be used.
First, the base part will be described. The base portion may be 100% with respect to the total silver amount used for grain formation, but is preferably 50% to 100%, and more preferably 60% to 100%. The base portion may have a core / shell structure as necessary. At this time, the core part of the base part is preferably 50% to 90% with respect to the total silver amount of the base part. The nitrogen-containing heterocyclic silver compound of the core part is preferably a benzotriazole compound or a derivative thereof. The average benzotriazole content is preferably 50 mol% or more, more preferably 70 mol%. Next, step (a), which is a step of forming the base portion, will be described.
The formation process of the base part can be produced through processes generally well known in the art for silver halides, that is, a nucleation process-ripening process-growth process, and they are not controlled and are simply mixed. However, in the present invention, it is preferable to form particles through two stages of nucleation and growth. Hereinafter, nucleation, growth, and each process will be described.

<Nucleation process>
Nucleation is generally carried out by adding a silver salt aqueous solution and a nitrogen-containing heterocyclic aqueous solution to a reaction vessel holding an aqueous solution of the protective colloid, or a silver solution in a protective colloid solution containing a nitrogen-containing heterocyclic alkaline solution. A single jet method in which a salt solution is added is used. Moreover, the method of adding the alkaline aqueous solution of a nitrogen-containing heterocyclic compound to the protective colloid solution containing a silver salt as needed can also be used. Moreover, the method of adding silver salt aqueous solution, nitrogen-containing heterocyclic alkali aqueous solution, and a protective colloid solution simultaneously by a triple jet method as needed can be used.
At this time, if necessary, a protective colloid component may be contained in the nitrogen-containing heterocyclic alkaline aqueous solution. Further, if necessary, a protective colloid solution, a silver salt solution and an aqueous benzotriazole solution are added to a mixer disclosed in JP-A-2-44335 and immediately transferred to a reaction vessel for nucleation. It can also be done. Nucleation can also be performed by passing an aqueous solution containing a nitrogen-containing heterocyclic alkali and a protective colloid solution through a pipe and adding an aqueous silver salt solution thereto.

Particle formation may be performed simply in a single solvent such as water or methanol, but it is preferable to include a compound having a protective colloid as a dispersion medium during particle formation as described above. However, natural polymers and synthetic polymers other than gelatin are also used in the same manner. The types of gelatin include alkali-treated gelatin, oxidized gelatin obtained by oxidizing methionine groups in gelatin molecules with hydrogen peroxide, etc. (methionine content 40 μmol / g or less), amino group-modified gelatin (eg, phthalated gelatin, trimellitized) Any of gelatin, succinylated gelatin, maleated gelatin, or esterified gelatin) and low molecular weight gelatin (mass average molecular weight: 3000 to 40,000) may be used. Japanese Patent Publication No. 5-12696 can be referred to for the oxidized gelatin, and Japanese Patent Application Laid-Open Nos. 8-82883 and 11-143002 can be referred to for the amino group-modified gelatin.
The total gelatin concentration in the dispersion medium is preferably 20% by mass or less, more preferably 10% by mass or less.
Moreover, you may use the lime processing bone gelatin which contains 30% or more of components of molecular weight 280,000 or more in the molecular weight distribution measured by the paggy method described in Unexamined-Japanese-Patent No. 11-237704 as needed. Further, for example, starches described in European Patent Publication EP758758A and US Pat. No. 5,733,718 may be used. In addition, natural polymers are disclosed in Japanese Patent Publication No. 7-11550, Research Disclosure Vol. 17643 (December 1978).
The pH of the dispersion medium is preferably 4-12

<Growth process>
When the concentration of the protective colloid in the dispersion medium solution before entering the growth step subsequent to the nucleation step is low (1% by mass or less), the protective colloid may be additionally added. In addition, protective colloids may be added during the growth process. The timing of additional addition may be any time during the growth process. The protective colloid concentration in the dispersion medium solution is preferably 1% by mass to 10% by mass. As the protective colloid used at this time, the aforementioned alkali-treated gelatin, amino group-modified gelatin, oxidized gelatin, natural polymer, or synthetic polymer may be used. Moreover, you may use the lime processing bone gelatin which contains 30% or more of components of molecular weight 280,000 or more in the molecular weight distribution measured by the paggy method described in Unexamined-Japanese-Patent No. 11-237704 as needed. Further, for example, starches described in European Patent Publication EP758758A and US Pat. No. 5,733,718 may be used. The pH during growth is preferably 4 to 8 or less when amino group-modified gelatin is present, and 2 to 8 is preferable otherwise. The addition rate of Ag ⁺ and nitrogen-containing heterocyclic ions during the crystal growth period is preferably 20% to 100%, preferably 30% to 100% of the crystal critical growth rate. In this case, the addition rate of silver ions and nitrogen-containing heterocyclic ions increases with crystal growth, but in that case, the addition rate of silver salt and nitrogen-containing heterocyclic aqueous solution may be increased, and the concentration of the aqueous solution increases. You may let them.

When performing the double jet method in which the silver salt aqueous solution and the nitrogen-containing heterocyclic aqueous solution are added at the same time, it is preferable to improve the stirring of the reaction vessel or dilute the concentration of the added solution.
In this case, it is also possible to preferably use a growth silver ion addition flow rate faster than the nucleation silver ion addition flow rate. From the formation of silver halide grains, it was not expected that the second stage flow rate would be preferable, but in the case of silver halide, the Ostwald ripening occurred during the growth and the grains became polydispersed. On the other hand, the nitrogen-containing heterocyclic silver salt seems to be less affected.

  A method of adding nitrogen-containing heterocyclic fine particles prepared outside the reaction vessel simultaneously with the addition of the silver salt aqueous solution and the nitrogen-containing heterocyclic aqueous solution can also be used. By this method, grain growth of at least 50% or more of the total silver amount is performed. Can also be The nitrogen-containing heterocyclic silver salt to be added may be prepared in advance or may be added while continuously preparing. The nitrogen-containing hetero silver salt used at this time may be different from or the same as the nitrogen-containing hetero ring salt used in the nucleation.

The average particle size of the nitrogen-containing heterocyclic salt to be added is 0.01 μm to 0.1 μm, preferably 0.02 μm to 0.08 μm.
Furthermore, the above ion addition method and fine particle addition method may be combined.

Next, (b) the epitaxial bonding step will be described.
Regarding the epitaxial formation on the base grain, for example, as described in US Pat. No. 4,435,501, it is a well-known method for silver halide grains, and a similar method is used in a nitrogen-containing heterocyclic salt. Is obtained in the same way.
Furthermore, an epitaxial nitrogen-containing heterocycle may be converted by adding a nitrogen-containing heterocycle solution different from the epitaxial composition. Epitaxial formation and subsequent growth or anion conversion may be carried out subsequently after the formation of the host nitrogen-containing heterocyclic silver salt base particles, or may be carried out after the substrate particles are formed and once washed / redispersed.
When forming the particles of the present invention, it is particularly preferable to prepare the particles while controlling the pH as described in JP-A-1-1000197 at all stages of nucleation and growth. In addition, it is also preferable to perform particle formation while controlling pAg.

  In the formation of the particles of the present invention, for example, JP-A-5-173268, JP-A-5-173269, JP-A-5-173270, JP-A-5-173271, JP-A-6-202258, JP-A-7-175147. The polyalkylene oxide block copolymer described in JP-A No. 3095578 or the polyalkylene oxide copolymer described in JP-A No. 3089578 may be present. The time when the compound is present may be any time during the preparation of the particles, but the effect is great when used at an early stage of particle formation.

Depending on the purpose, it is preferable that a metal ion salt is present before forming the nitrogen-containing heterocyclic particles of the present invention, for example, during the particle formation, before the desalting step and coating. When the particles are doped, it is preferably added at the time of grain formation, after modification of the grain surface and after grain formation. A method of doping the entire particle and a method of doping only the core or only the shell of the particle can be selected. For example, Mg, Ca, Sr, Ba, Al, Sc, Y, La, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ru, Rh, Pd, Re, Os, Ir, Pt, Au, Cd, Hg, Tl, In, Sn, Pb, and Bi can be used. These metals can be added in the form of a salt that can be dissolved during particle formation, such as ammonium salt, acetate salt, nitrate salt, sulfate salt, phosphate salt, hydrate salt, hexacoordinated complex salt, and tetracoordinated complex salt. For _{example, CdBr 2, CdCl 2, Cd} (NO 3) 2, Pb (NO 3) 2, Pb (CH 3 COO) 2, K 4 [Fe (CN) 6], (NH 4) 4 [Fe (CN) _6], K ₂ IrCl _6, include _(NH 4) 3 RhCl _6, and _K 4 Ru _{(CN) 6.}
The ligand of the coordination compound can be selected from halo, aco, cyano, cyanate, thiocyanate, nitrosyl, thionitrosyl, oxo, or carbonyl. These may use only one kind of metal compound, but may be used in combination of two or more kinds.

It is preferable to use an oxidizing agent for silver during the production process of the nitrogen-containing heterocyclic particles of the present invention. The oxidizing agent for silver refers to a compound having an action of acting on metallic silver and converting it into silver ions. Particularly effective are compounds that convert very fine silver particles by-produced in the formation process and chemical sensitization process of nitrogen-containing heterocyclic silver particles into silver ions. The silver ions generated here may form, for example, a silver salt that is hardly soluble in water such as silver halide, silver sulfide, or silver selenide, or a silver salt that is easily soluble in water such as silver nitrate. May be formed. The oxidizing agent for silver may be an inorganic substance or an organic substance. Examples of the inorganic oxidizing agent include ozone, hydrogen peroxide and adducts thereof (for example, NaBO ₂ .H ₂ O ₂ .3H ₂ O, 2NaCO ₃ .3H ₂ O ₂ , Na ₄ P ₂ O ₇ .2H _{2). O 2, 2Na 2 SO 4 ·} H 2 O 2 · 2H 2 O), peroxy acid salt _{(e.g., K 2 S 2 O 8,} K 2 C 2 O 6, K 2 P 2 O 8), peroxy complex compound ( For _{example, K 2 [Ti (O 2} ) C 2 O 4] · 3H 2 O, 4K 2 SO 4 · Ti (O 2) OH · SO 4 · 2H 2 O, Na 3 [VO (O 2) (C 2 H ₄ ) ₂ ] · 6H ₂ O), permanganate (eg, KMnO ₄ ), chromate (eg, K ₂ Cr ₂ O ₇ ), oxyacid salts, and halogen elements such as iodine and bromine Perhalogenates (eg potassium periodate), high atoms Metal salts (e.g., hexacyanoferrate potassium ferric acid) is, and thiosulfonate salts.

Examples of organic oxidizing agents include quinones such as p-quinone, organic peroxides such as peracetic acid and perbenzoic acid, and compounds that release active halogens (for example, N-bromosuccinimide, chloramine T, An example is chloramine B).
Preferred oxidizing agents in the present invention are ozone, hydrogen peroxide and its adducts, halogen elements, inorganic oxidizers of thiosulfonates, and organic oxidizers of quinones. This method can be used at any stage from before particle formation to just before coating.
The nitrogen-containing heterocyclic silver salt of the present invention can contain various compounds for the purpose of preventing fogging during the production process, storage or photographic processing, or stabilizing the photographic performance. In the silver halide, thiazoles such as benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles, mercaptothiazoles, mercaptobenzothiazoles, mercaptobenzimidazoles, Mercaptothiadiazoles, aminotriazoles, benzotriazoles, nitrobenzotriazoles, mercaptotetrazoles (especially 1-phenyl-5-mercaptotetrazole); mercaptopyrimidines; mercaptotriazines; Azaindenes such as triazaindenes, tetraazaindenes (especially 4-hydroxy substituted (1,3,3a, 7) titraazaindenes), Known as antifoggants or stabilizers such as Taazainden acids, it can be added as many compounds and silver halide grains even in a nitrogen-containing heterocyclic silver salts of the present invention. For example, those described in US Pat. Nos. 3,954,474, 3,982,947, and Japanese Patent Publication No. 52-28660 can be used. One preferred compound is the compound described in JP-A-63-212932. Antifogging agents and stabilizers can be added according to the purpose before forming particles, during forming particles, after forming particles, washing with water, dispersing after washing with water, and at various times before coating. Besides adding the original fog prevention and stabilizing effect during silver salt preparation, it can be used for various purposes such as controlling the crystal wall of the particles, reducing the particle size, and reducing the solubility of the particles. .

(Method for desalting silver salt particles of nitrogen-containing heterocyclic compound)
The silver salt particles of the nitrogen-containing heterocyclic compound of the present invention may be desalted by any method as long as it is at a temperature of 30 ° C. or higher, but in particular, centrifugal filtration, ultrafiltration, suction filtration, electrodialysis, Further, desalting is preferably performed by a method such as a decantation method (flocculation method).
The flocculation method of the present invention includes various methods, and any method can be used. For example, in the desalting method of a silver salt prepared with a gelatin dispersion medium, for example, (1) a coagulating sedimentation agent is added to an emulsion. Adding, adjusting the pH of the emulsion, flocculating and precipitating the emulsion, and removing the supernatant, (2) using a derivative gelatin (eg acylated gelatin), the pH of the emulsion is below the isoelectric point (usually The emulsion aggregates and settles only by adjusting to 3.3 to 4.7). (3) An enzyme is added to the emulsion, the dispersion medium is enzymatically decomposed to lower the viscosity of the emulsion, and the emulsion is precipitated. (4) When gelatin containing 60% by mass or more of low molecular weight gelatin having a content of 60,000 or less is used as a dispersion medium, It becomes easy to settle. In this method, the emulsion is allowed to settle, and then the supernatant is removed. (5) When a water-soluble organic solvent such as an aliphatic alcohol is added to gelatin, the gelatin loses its hydrophilicity and precipitates. (6) When salts such as ammonium sulfate, particularly polyvalent salts, are added at a pH (3 to 5) below the isoelectric point, salting out occurs and precipitation occurs. Moreover, these two or more combined use can be mention | raise | lifted. For details of the method of washing the emulsion with water, Grafkide, chemistry and physics of photography (Chimie et Physiquephotographs), 5th edition, Edition de 1 ′ Usine Novele, Paris, Part 3 (1987), Research Disclosure ( Research Disclosure), Volume 176, Item 17643 (December, 1978), Volume 307 (Item 307105, November, 1989), and the description of the following literature can be referred to. In any of the above cases, precipitation is most accelerated when the pH of the emulsion is adjusted to the vicinity of the isoelectric point of the emulsion (pH 3 to 5). Particularly in the case of (1), (2), (5) and (6), it is necessary to adjust the pH of the emulsion to the vicinity of the isoelectric point to cause aggregation and flocification. However, if the pH is lowered too much, it dissolves again due to the presence of hydrophilic groups.

  Low molecular weight gelatin is obtained by hydrolyzing normal photographic gelatin under enzymatic, thermal, acid or alkaline conditions. With respect to the details thereof, the description in JP-A-4-340539 can be referred to. The added enzyme is preferably inactivated by heating to 55 ° C or higher, more preferably 60 ° C to 80 ° C, still more preferably 65 ° C to 75 ° C, preferably 5 minutes or longer, more preferably 10 minutes or longer. it can. Specific examples of the enzyme include pronase, trypsin, papain, phytin, renin, and chymotrypsin.

Examples of the derivative gelatin include gelatin in which the amino group of gelatin is acetylated, phthalated, maleated, succinated, and the like. Since the amino group —NH 4 ⁺ is invalidated by acylation, it is flooded and coagulated. Even if the amino group is protected with aryl sulfochloride, aryl isocyanate, 1,4-diketone, etc., the same effect can be obtained. Specific examples of the coagulating sedimentation agent include organic sulfonic acids (eg naphthalene-disulfonic acid and benzenesulfonyl chloride, long-chain alkyl sulfates, sulfonated polymers such as sulfonated polyethylene, sulfonated polyacryl, or sulfonated polystyrene), males Examples include acid + dextran derivatives. Also in this case, the negatively charged sulfone group is ionically bonded to the amino group of the gelatin having a positive charge below the isoelectric point to be hydrophobized, and the gelatin molecule is crosslinked by a plurality of sulfone groups.

  The ultrafiltration dehydration and desalting techniques of the present invention are described in Research Disclosure, Vol. 102, 10298 and Vol. 131, 13122. In addition, U.S. Pat. Nos. 4,334,012, 5,164,092, 5,242,597, European Patents 79455, 843206, JP-A-8-278580, JP-A-11-231449, etc. It is disclosed.

As the membrane module in which the membrane used for the ultrafiltration membrane of the present invention is incorporated in a container, a tubular module, a hollow fiber module, a pleat module, a spiral module, a flat membrane module, and a plate & frame module can be used. Of these, hollow fiber modules and flat membrane modules are preferably used.
Various materials can be used for the ultrafiltration membrane of the present invention. For example, polyacrylonitrile, polysulfone, polyimide, polyethersulfone, cellulose acetate, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, or ceramics such as aluminum oxide are preferably used as main materials of useful ultrafiltration membranes. It is done.

  A fractional molecular weight is an example of the performance of the ultrafiltration membrane of the present invention. The molecular weight cut off is a molecular weight that is 90% or more of the blocking rate (percentage of the difference between the concentration of the feed solution and the concentration of the permeate divided by the concentration of the feed solution). The silver halide grains do not permeate and are not required. And the dispersion preferably has a molecular weight cut through. In addition, if the molecular weight cut off is reduced, the flow rate of the liquid that passes through the ultrafiltration membrane decreases, so it is necessary to select the optimum molecular weight cut off. Useful molecular weight cut off is 1,000 to 1,000,000, preferably 3,000 to 100,000. The pore diameter of the ultrafiltration membrane is preferably 0.005 μm to 10 μm, more preferably 0.01 μm to 1 μm.

  In the electrodialysis of the present invention, a solution containing ions is put between an anion exchange membrane and a cation exchange membrane, and a direct current is applied from both sides, whereby the anion is passed through the anion exchange membrane to the anode side and through the cation exchange membrane. In this method, positive ions are moved to the cathode side to remove ions from the solution between the membranes. The desalting method in the present invention is based on this principle.

Furthermore, at this time, ions move with water molecules hydrated to the ions. Therefore, moisture is also removed in proportion to the amount of mobile ions contained in the solution to remove the salt, and electrodialysis has the feature that a solution with a higher salt concentration can remove more water molecules. Have. Using this principle, the concentration can be increased by adding a large amount of salt to the emulsion for concentration.
Here, considering the change in solubility in the system due to the increase in salt concentration, if salt is added at any time during electrodialysis, the salt is removed from the emulsion with water in the emulsion at any time, resulting in the emulsion. The emulsion can be concentrated without increasing the salt concentration. The desalting and concentration method in the present invention is based on this principle.

The effect of the present invention is obtained when the desalting temperature is 30 ° C. or higher, but is preferably 35 ° C. or higher, and the effect of the present invention is more obtained when it is 40 ° C. or higher. This is an area where silver halide grains generally known in the industry are subject to performance degradation such as agglomeration of grains and increased fog in the desalting process in addition to an increase in manufacturing cost due to the high temperature. In nitrogen-containing heterocyclic silver salts, it was not easily imagined that washing with water at a relatively high temperature would improve performance.
Moreover, in this invention, it is a more preferable manufacturing method to perform a desalting process once or more. By using the desalting method of the present invention, the amount of silver loss is reduced, so that desalting can be performed with high efficiency even if more salt is removed, and less water washing can be achieved by separating the desalting process. Highly efficient desalting with water.

(Shape of nitrogen-containing heterocyclic silver salt)
(Strip-shaped particles)
One aspect of the silver salt particles of the nitrogen-containing heterocyclic compound of the present invention is a strip-like particle, and the major axis (denoted as a), medium diameter (denoted as b), and minor axis (c) of the strip. A), and the ratio (b / c) of the medium diameter b to the short diameter c is 1.1 or more and 10 or less. The ratio of b / c is preferably 1.5 or more, more preferably 2 or more, and preferably 10 or less, more preferably 8 or less.
Preferably, the major axis a of the strip is 0.01 μm or more and 20 μm or less, more preferably 0.02 μm or more and 5 μm or less.
Preferably, the inner diameter b of the strip is 0.003 μm or more and 10 μm or less, and the minor axis c of the strip is 0.001 μm or more and 1 μm or less, more preferably, the b is 0.005 μm or more and 2 μm or less. The short axis c of the strip is 0.005 μm or more and 0.2 μm or less.
Preferably, the ratio a / b between the major axis a and the middle diameter b is 1.5 or more and 100 or less.

(Rod-like particles)
Another embodiment of the silver salt particle of the nitrogen-containing heterocyclic compound of the present invention is a rod-like particle, the rod has a circular or oval cross section, the major axis of the rod (denoted as d), and the rod The equivalent circle diameter (denoted as e) of the cross section of d is d / e> 2.
Preferably, the ratio d / e> 4.
Preferably, the silver salt particle of the nitrogen-containing heterocyclic compound is a silver salt of a benzotriazole compound. “e” is preferably 0.003 μm or more and 10 μm or less, and more preferably 0.005 μm or more and 2 μm or less. d is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.02 μm or more and 2 μm or less.
(Shape observation method)
The method for measuring the shape of the silver salt particles of the nitrogen-containing heterocyclic compound can be performed by observation with an electron microscope.
<Definition of a, b, c, d, e>
In the present application, a strip-like crystal is apparently a case where it is observed as a rectangular parallelepiped, but even if it is close to an indeterminate shape, it corresponds to this if the major axis, the middle axis, and the minor axis can be distinguished and determined. In other words, the strip-shaped crystal is a lateral surface corresponding to a cross section and has a shape in which the medium diameter b and the short diameter c can be measured. Note that the surfaces surrounded by the major axis a and the medium diameter b, and the medium diameter b and the minor axis c are not limited to squares or rectangles, but may include deformed polygons, curved surfaces, or irregularities, and the longest of the respective surfaces. The portion was measured to be a long diameter a, a medium diameter b, and a short diameter c.
On the other hand, a circle or ellipse where the cross section is rounded and the medium diameter b and the minor diameter c cannot be measured with a significant distinction is defined as a rod-like crystal, and in this case, the equivalent circle diameter is defined as e. The major axis d is the longest part of the surface.
(Tabular grains)
The silver salt particles of the nitrogen-containing heterocyclic compound of the present invention are tabular grains, and the major axis (denoted as a), medium diameter (denoted as b), and minor axis (denoted as c) of the flat plate. However, a ≧ b, and the ratio (b / c) of the medium diameter b to the short diameter c exceeds 10.
Preferably, the ratio b / c is 11 or more and 50 or less.
When the ratio b / c is 10 or less, it is not preferable in that the photographic performance is likely to change when the coating solution containing the silver salt is aged for a long time. This is not preferable in terms of development delay.
Preferably, the major axis a is 0.01 μm or more and 20 μm or less, more preferably 0.02 μm or more and 5 μm or less.
Preferably, the minor axis c is 0.005 μm or more and 5 μm or less, and more preferably 0.01 μm or more and 2 μm or less.
The medium diameter b is preferably 0.01 μm or more and 10 μm or less, more preferably 0.02 μm or more and 5 μm.

(Method for dispersing silver salt particles of nitrogen-containing heterocyclic compound)
In order to obtain a fine dispersion, the silver salt particles of the nitrogen-containing heterocyclic compound in the present invention are preferably dispersed in a wet slurry state after crystal preparation. It is desirable to use an appropriate dispersant for dispersion. As the dispersing means, various dispersing methods described in the explanation of the reducing agent of the present application can be used, and a solid dispersing method is particularly preferable. A specific synthesis method is described in JP-A-1-100197.

2. Photothermographic material The photothermographic material of the present invention is a photothermographic material containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent on at least one surface of a support. The silver salt particles of the nitrogen-containing heterocyclic compound described above are contained as the non-photosensitive organic silver salt.
Preferably, it has an image forming layer containing at least the photosensitive silver halide, fatty acid silver salt, the reducing agent and a binder, and the above nitrogen-containing heterocycle is formed on the same side of the support as the image forming layer. It has a non-photosensitive layer containing silver salt particles of the compound.
The silver salt of the nitrogen-containing heterocyclic compound used in the photothermographic material of the present invention does not substantially contribute to the image density. The fact that it does not substantially contribute to image performance is the ratio of increase in the total silver amount of the light-sensitive material when the nitrogen-containing heterocyclic silver salt of the present invention is used compared to the case where the nitrogen-containing heterocyclic silver salt is not used. In contrast, the ratio of the density difference of the highest density after heat development is less than 5%.
In the heat-developable material of the present invention, preferably, the ratio of the silver salt of the nitrogen-containing heterocyclic compound to the fatty acid silver salt is 0.5 mol% or more and 50 mol% or less in terms of silver molar ratio. When the amount is 0.5 mol% or less, the effect of the present invention cannot be exhibited sufficiently. If it is 50% or more, the coating surface condition and Dmax will be adversely affected.

(Non-photosensitive organic silver salt contained in the image forming layer)
Next, non-photosensitive organic silver salts other than the nitrogen-containing heterocycle used in the present invention will be described.
1) Composition The organic silver salt that can be 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 organic silver salt may be any organic substance that can supply silver ions that can be reduced by a reducing agent. As for such non-photosensitive organic silver salt, paragraph numbers 0048 to 0049 of JP-A-10-62899, page 18 line 24 to page 19 line 37 of European Patent Publication No. 0803764A1, European Patent Publication. No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, and the like. Silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30 carbon atoms, preferably 15 to 28 carbon atoms) are preferred. Preferred examples of the fatty acid silver salt include silver lignocerate, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver erucate and the like. Including a mixture of In the present invention, among these fatty acid silvers, the silver behenate content is preferably 50 mol% to 100 mol%, more preferably 85 mol% to 100 mol%, and still more preferably 95 mol% to 100 mol%. The following fatty acid silver is preferably used. Furthermore, it is preferable to use fatty acid silver 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.

  Moreover, it is preferable that silver stearate content rate is 1 mol% or less. By making the stearic acid content 1 mol% or less, a silver salt of an organic acid having a low Dmin, high sensitivity and excellent image storage stability can be obtained. As said stearic acid content rate, 0.5 mol% or less is preferable and it is especially preferable not to contain substantially.

  Furthermore, when silver arachidate is included as the silver salt of the organic acid, the silver arachidate content is 6 mol% or less to obtain a low Dmin and an organic acid silver salt excellent in image storability. It is preferable at a point and it is still more preferable that it is 3 mol% or less.

2) Shape The shape of the organic silver salt that can be used in the present invention is not particularly limited, and may be any of a needle shape, a rod shape, a flat plate shape, and a flake shape.
In the present invention, scaly organic silver salts are preferred. In addition, short needle-like, rectangular parallelepiped, cubic or potato-like amorphous particles having a major axis / uniaxial length ratio of less than 5 are also preferably used. These organic silver particles have a feature that the fog at the time of heat development is less than that of long needle-like particles having a ratio of the long axis to the single axis of 5 or more. In particular, particles having a major axis / uniaxial ratio of 3 or less are preferable because the mechanical stability of the coating film is improved. In the present specification, the scaly organic silver salt is defined as follows. The organic acid silver salt was observed with an electron microscope, and the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped. Then, calculation is performed with the shorter numerical values a and b, and x is obtained as follows.
x = b / a

  In this way, x is obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of x (average) ≧ 1.5 are defined as flakes. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 15 ≧ x (average) ≧ 1.5. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

  In the flake shaped particle, a can be regarded as a thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 μm or more and 0.3 μm or less, and more preferably 0.1 μm or more and 0.23 μm or less. The average c / b is preferably 1 or more and 9 or less, more preferably 1 or more and 6 or less, still more preferably 1 or more and 4 or less, and most preferably 1 or more and 3 or less.

By setting the equivalent sphere diameter to 0.05 μm or more and 1 μm or less, aggregation is hardly caused in the photothermographic material, and image storability is improved. The sphere equivalent diameter is preferably 0.1 μm or more and 1 μm or less. In the present invention, the method for measuring the equivalent sphere diameter is obtained by directly photographing a sample using an electron microscope and then image-processing the negative.
In the flake shaped particles, the spherical equivalent diameter / a of the particles is defined as the aspect ratio. The aspect ratio of the flake shaped particles is preferably 1.1 or more and 30 or less, and preferably 1.1 or more and 15 or less, from the viewpoint of preventing aggregation in the photothermographic material and improving the image storage stability. More preferred.

  The particle size distribution of the organic silver salt is preferably monodispersed. Monodispersion is preferably 100% or less, more preferably 80% or less, and even more preferably 50% of the value obtained by dividing the standard deviation of the lengths of the short and long axes by the short and long axes. It is as follows. The method for measuring the shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion. As another method for measuring monodispersity, there is a method for obtaining the standard deviation of the volume weighted average diameter of the organic silver salt, and the percentage (variation coefficient) of the value divided by the volume weighted average diameter is preferably 100% or less, more Preferably it is 80% or less, More preferably, it is 50% or less. As a measuring method, for example, it is obtained from the particle size (volume weighted average diameter) obtained by irradiating an organic silver salt dispersed in a liquid with laser light and obtaining an autocorrelation function with respect to the temporal change of the fluctuation of the scattered light. Can do.

3) Preparation Known methods and the like can be applied to the production and dispersion method of the organic acid silver used in the present invention. For example, the above-mentioned JP-A-10-62899, European Patent Publication No. 0803763A1, European Patent Publication No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, JP-A-2001-163889, 2001-163890, 2001-163825, 2001-33907, 2001-188313, 2001-83651, 2002-6442, 2002-49117, 2002-31870, 2002-107868 You can refer to the issue.

  In addition, when the photosensitive silver salt is allowed to coexist at the time of dispersion of the organic silver salt, the fog rises and the sensitivity is remarkably lowered. Therefore, it is more preferable that the photosensitive silver salt is not substantially contained at the time of dispersion. In the present invention, the amount of the photosensitive silver salt in the aqueous dispersion to be dispersed is preferably 1 mol% or less, more preferably 0.1 mol% or less with respect to 1 mol of the organic acid silver salt in the liquid. Further, it is more preferable that no positive photosensitive silver salt is added.

  In the present invention, a photothermographic material can be produced by mixing an organic silver salt aqueous dispersion and a photosensitive silver salt aqueous dispersion, but the mixing ratio of the organic silver salt and the photosensitive silver salt can be selected according to the purpose. However, the ratio of the photosensitive silver salt to the organic silver salt is preferably in the range of 1 mol% to 30 mol%, more preferably 2 mol% to 20 mol%, and particularly preferably 3 mol% to 15 mol%. Mixing two or more organic silver salt aqueous dispersions and two or more photosensitive silver salt aqueous dispersions when mixing is a method preferably used for adjusting photographic characteristics.

4) Addition amount Although the organic silver salt in the present invention can be used in a desired amount, the total coating silver amount including silver halide is preferably 0.1 g / m ² or more and 5.0 g / m ² or less, more preferably. It is 0.3 g / m ² or more and 3.0 g / m ² or less, more preferably 0.5 g / m ² or more and 2.0 g / m ² or less.
In particular, in order to improve image storability, the total coated silver amount is preferably 1.8 g / m ² or less, more preferably 1.6 g / m ² or less.

(Description of reducing agent)
The photothermographic material of the present invention preferably contains a heat developer which is a reducing agent for the organic silver salt. The reducing agent for the organic silver salt may be any substance (preferably an organic substance) that reduces silver ions to metallic silver. Examples of such reducing agents are described in JP-A No. 11-65021, paragraphs 0043 to 0045, and European Patent Publication No. 0803764A1, page 7, line 34 to page 18, line 12.
In the present invention, the reducing agent is preferably a so-called hindered phenol-based reducing agent or bisphenol-based reducing agent having a substituent at the ortho position of the phenolic hydroxyl group, and more preferably a compound represented by the following general formula (R).

In the general formula (R), R ¹¹ and R ¹¹ ′ each independently represents an alkyl group having 1 to 20 carbon atoms. R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent that can be substituted on a benzene ring. L represents a —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring.

The general formula (R) will be described in detail.
In the following, when referred to as an alkyl group, a cycloalkyl group is also included in this unless otherwise specified.
1) R ¹¹ and R ¹¹ '
R ¹¹ and R ¹¹ ′ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms.
The substituent of the alkyl group is not particularly limited, but preferably an aryl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acylamino group, a sulfonamido group, a sulfonyl group, a phosphoryl group, Examples include an acyl group, a carbamoyl group, an ester group, a ureido group, a urethane group, and a halogen atom.

2) R ¹² and R ¹² ′, X ¹ and X ¹ ′
R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent that can be substituted on a benzene ring, and X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring. Preferred examples of the group that can be substituted on the benzene ring include an alkyl group, an aryl group, a halogen atom, an alkoxy group, and an acylamino group.

3) L
L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and the alkyl group may have a substituent. Specific examples of the unsubstituted alkyl group for R ¹³ are methyl group, ethyl group, propyl group, butyl group, heptyl group, undecyl group, isopropyl group, 1-ethylpentyl group, 2,4,4-trimethylpentyl group, cyclohexyl. Group, 2,4-dimethyl-3-cyclohexenyl group, 3,5-dimethyl-3-cyclohexenyl group and the like. Examples of the substituent of the alkyl group are the same as the substituent of R ¹¹ , and are a halogen atom, alkoxy group, alkylthio group, aryloxy group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, oxycarbonyl group, A carbamoyl group, a sulfamoyl group, etc. are mentioned.

4) Preferred substituents R ¹¹ and R ¹¹ ′ are preferably primary, secondary or tertiary alkyl groups having 1 to 15 carbon atoms, specifically methyl, isopropyl, t-butyl, t -Amyl group, t-octyl group, cyclohexyl group, cyclopentyl group, 1-methylcyclohexyl group, 1-methylcyclopropyl group and the like. R ¹¹ and R ¹¹ ′ are more preferably an alkyl group having 1 to 4 carbon atoms, and among them, a methyl group, a t-butyl group, a t-amyl group, or a 1-methylcyclohexyl group is more preferable, and a methyl group, t- A butyl group is most preferred.

R ¹² and R ¹² ′ are preferably an alkyl group having 1 to 20 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a t-butyl group, a t-amyl group, a cyclohexyl group. Group, 1-methylcyclohexyl group, benzyl group, methoxymethyl group, methoxyethyl group and the like. More preferred are a methyl group, an ethyl group, a propyl group, an isopropyl group, or a t-butyl group, and particularly preferred are a methyl group and an ethyl group.
X ¹ and X ¹ ′ are preferably a hydrogen atom, a halogen atom, or an alkyl group, and more preferably a hydrogen atom.

L is preferably a —CHR ¹³ — group.
R ¹³ is preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms. As the alkyl group, a cyclic alkyl group is also preferably used in addition to a chain alkyl group. Moreover, what has a C = C bond in these alkyl groups can also be used preferably. Examples of the alkyl group include a methyl group, ethyl group, propyl group, isopropyl group, 2,4,4-trimethylpentyl group, cyclohexyl group, 2,4-dimethyl-3-cyclohexenyl group, or 3,5-dimethyl-3. -A cyclohexenyl group and the like are preferable. R ¹³ is particularly preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a 2,4-dimethyl-3-cyclohexenyl group.

When R ¹¹ and R ¹¹ ′ are tertiary alkyl groups and R ¹² and R ¹² ′ are methyl groups, R ¹³ is a primary or secondary alkyl group having 1 to 8 carbon atoms (methyl group, ethyl group, propyl group). Group, isopropyl group, or 2,4-dimethyl-3-cyclohexenyl group).
When R ¹¹ and R ¹¹ ′ are tertiary alkyl groups and R ¹² and R ¹² ′ are alkyl groups other than methyl groups, R ¹³ is preferably a hydrogen atom.
When R ¹¹ and R ¹¹ ′ are not a tertiary alkyl group, R ¹³ is preferably a hydrogen atom or a secondary alkyl group, and particularly preferably a secondary alkyl group. Preferred groups as the secondary alkyl group for R ¹³ are isopropyl group and 2,4-dimethyl-3-cyclohexenyl group.
The reducing agent has different heat developability, developed silver tone, and the like depending on the combination of R ¹¹ , R ¹¹ ′, R ¹² , R ¹² ′, and R ¹³ . Since these can be prepared by combining two or more reducing agents, it is preferable to use a combination of two or more depending on the purpose.

  Although the specific example of the reducing agent in this invention including the compound represented by general formula (R) below is shown, this invention is not limited to these.

Examples of preferable reducing agents in the present invention other than the above are the compounds described in JP-A Nos. 2001-188314, 2001-209145, 2001-350235, 2002-156727, and EP1278101A2.
In the present invention, the addition amount of the reducing agent is preferably 0.1 g / m ² or more and 3.0 g / m ² or less, more preferably 0.2 g / m ² or more and 2.0 g / m ² or less, and still more preferably. Is 0.3 g / m ² or more and 1.0 g / m ² or less. 5 mol% or more and 50 mol% or less is preferably contained with respect to 1 mol of silver on the surface having the image forming layer, more preferably 8 mol% or more and 30 mol% or less, and 10 mol% or more and 20 mol% or less. More preferably, it is contained.
The reducing agent is preferably contained in the image forming layer.

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.
Well-known emulsification and dispersion methods include oils such as dibutyl phthalate, tricresyl phosphate, dioctyl sebacate or tri (2-ethylhexyl) phosphate, and dissolution using an auxiliary solvent such as ethyl acetate or cyclohexanone, and dodecylbenzene. Examples thereof include a method of mechanically preparing an emulsified dispersion by adding a surfactant such as sodium sulfonate, oleoyl-N-methyl taurate, sodium di (2-ethylhexyl) sulfosuccinate. At this time, it is also preferable to add a polymer such as α-methylstyrene oligomer or poly (t-butylacrylamide) for the purpose of adjusting the viscosity and refractive index of the oil droplets.

In addition, as a solid fine particle dispersion method, a reducing agent powder is dispersed in an appropriate solvent such as water by a ball mill, a colloid mill, a vibration ball mill, a sand mill, a jet mill, a roller mill, or an ultrasonic wave to produce a solid dispersion. A method is mentioned. In this case, a protective colloid (for example, polyvinyl alcohol) or a surfactant (for example, an anionic surfactant such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used. Good. In the mills, beads such as zirconia are usually used as a dispersion medium, and Zr and the like eluted from these beads may be mixed in the dispersion. Although it depends on the dispersion conditions, it is usually in the range of 1 ppm to 1000 ppm. If the Zr content in the light-sensitive material is 0.5 mg or less per 1 g of silver, there is no practical problem.
The aqueous dispersion preferably contains a preservative (for example, benzoisothiazolinone sodium salt).
Particularly preferred is a solid particle dispersion method of a reducing agent, which is added as fine particles having an average particle size of 0.01 μm to 10 μm, preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 2 μm. Is preferred. In the present application, it is preferable to use other solid dispersions dispersed in a particle size within this range.

(Description of development accelerator)
In the photothermographic material of the invention, a development accelerator is preferably used. As development accelerators, sulfonamide phenol compounds represented by the general formula (A) described in JP-A Nos. 2000-267222 and 2000-330234, and general formulas described in JP-A No. 2001-92075 Hindered phenol compounds represented by (II), general formula (I) described in JP-A-10-62895 and JP-A-11-15116, and general formulas of JP-A 2002-156727 (D), a hydrazine-based compound represented by the general formula (1) described in JP-A-2002-278017, and a general formula (2) described in JP-A-2001-264929. Phenol-based or naphthol-based compounds are preferably used. Moreover, the phenol type compound described in Unexamined-Japanese-Patent No. 2002-311533 and Unexamined-Japanese-Patent No. 2002-341484 is also preferable. In particular, naphthol compounds described in JP-A No. 2003-66558 are preferable. These development accelerators are used in the range of 0.1 mol% or more and 20 mol% or less, preferably 0.5 mol% or more and 10 mol% or less, more preferably 1 mol% or more with respect to the reducing agent. The range is 5 mol% or less. The introduction method to the light-sensitive material includes the same method as the reducing agent, but it is particularly preferable to add as a solid dispersion or an emulsified dispersion. When added as an emulsified dispersion, it is added as an emulsified dispersion dispersed using a high-boiling solvent that is solid at room temperature and a low-boiling auxiliary solvent, or as a so-called oilless emulsified dispersion that does not use a high-boiling solvent. It is preferable to add.
In the present invention, among the above development accelerators, hydrazine compounds described in JP-A Nos. 2002-156727 and 2002-278017 and naphthol compounds described in JP-A No. 2003-66558 are used. Is more preferable.

Particularly preferred development accelerators in the invention are compounds represented by the following general formulas (A-1) and (A-2).
Formula (A-1)
Q ₁ -NHNH-Q ₂
In the formula, Q ₁ represents an aromatic group or a heterocyclic group bonded to —NHNH—Q ₂ at a carbon atom, and Q ₂ represents a carbamoyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group, or Represents a sulfamoyl group.

In the general formula (A-1), the aromatic group or heterocyclic group represented by Q ₁ is preferably a 5- to 7-membered unsaturated ring. Preferred examples include benzene ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, 1,2,4-triazine ring, 1,3,5-triazine ring, pyrrole ring, imidazole ring, pyrazole ring, 1,2 , 3-triazole ring, 1,2,4-triazole ring, tetrazole ring, 1,3,4-thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,3,4 -Oxadiazole ring, 1,2,4-oxadiazole ring, 1,2,5-oxadiazole ring, thiazole ring, oxazole ring, isothiazole ring, isoxazole ring, or thiophene ring are preferred, A condensed ring in which these rings are condensed with each other is also preferable.

  These rings may have a substituent, and when they have two or more substituents, these substituents may be the same or different. Examples of substituents include halogen atoms, alkyl groups, aryl groups, carbonamido groups, alkylsulfonamido groups, arylsulfonamido groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, carbamoyl groups, sulfamoyl groups, cyano Groups, alkylsulfonyl groups, arylsulfonyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, and acyl groups. When these substituents are substitutable groups, they may further have substituents. Examples of preferred substituents include halogen atoms, alkyl groups, aryl groups, carbonamido groups, alkylsulfonamido groups, aryls. Sulfonamide group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, cyano group, sulfamoyl group, alkylsulfonyl group, arylsulfonyl group, and acyloxy group Can be mentioned.

The carbamoyl group represented by Q ₂ is preferably a carbamoyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms. For example, unsubstituted carbamoyl, methylcarbamoyl, N-ethylcarbamoyl, N-propylcarbamoyl N-sec-butylcarbamoyl, N-octylcarbamoyl, N-cyclohexylcarbamoyl, N-tert-butylcarbamoyl, N-dodecylcarbamoyl, N- (3-dodecyloxypropyl) carbamoyl, N-octadecylcarbamoyl, N- {3 -(2,4-tert-pentylphenoxy) propyl} carbamoyl, N- (2-hexyldecyl) carbamoyl, N-phenylcarbamoyl, N- (4-dodecyloxyphenyl) carbamoyl, N- (2-chloro-5 Dodecyloxycarbo Nylphenyl) carbamoyl, N-naphthylcarbamoyl, N-3-pyridylcarbamoyl, and N-benzylcarbamoyl.

The acyl group represented by Q ₂ is preferably an acyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms. For example, formyl, acetyl, 2-methylpropanoyl, cyclohexylcarbonyl, octanoyl, 2 -Hexyldecanoyl, dodecanoyl, chloroacetyl, trifluoroacetyl, benzoyl, 4-dodecyloxybenzoyl, and 2-hydroxymethylbenzoyl. The alkoxycarbonyl group represented by Q ₂ is preferably an alkoxycarbonyl group having 2 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, isobutyloxycarbonyl, cyclohexyloxycarbonyl, Examples include dodecyloxycarbonyl and benzyloxycarbonyl.

The aryloxycarbonyl group represented by Q ₂ is preferably an aryloxycarbonyl group having 7 to 50 carbon atoms, more preferably 7 to 40 carbon atoms, such as phenoxycarbonyl, 4-octyloxyphenoxycarbonyl, 2-hydroxy Examples include methylphenoxycarbonyl and 4-dodecyloxyphenoxycarbonyl. The sulfonyl group represented by Q ₂ is preferably a sulfonyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as methylsulfonyl, butylsulfonyl, octylsulfonyl, 2-hexadecylsulfonyl, 3- Dodecyloxypropylsulfonyl, 2-octyloxy-5-tert-octylphenylsulfonyl, and 4-dodecyloxyphenylsulfonyl.

The sulfamoyl group represented by Q ₂ is preferably a sulfamoyl group having 0 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as an unsubstituted sulfamoyl group, an N-ethylsulfamoyl group, N- (2- Ethylhexyl) sulfamoyl, N-decylsulfamoyl, N-hexadecylsulfamoyl, N- {3- (2-ethylhexyloxy) propyl} sulfamoyl, N- (2-chloro-5-dodecyloxycarbonylphenyl) sulfamoyl, And N- (2-tetradecyloxyphenyl) sulfamoyl. The group represented by Q ₂ may further have a group listed as an example of the substituent of the 5-membered to 7-membered unsaturated ring represented by Q ₁ at a substitutable position, When it has two or more substituents, these substituents may be the same or different.

Next, preferred range for the compound represented by formula (A-1) is to be described. Q ₁ is preferably a 5- to 6-membered unsaturated ring, such as a benzene ring, pyrimidine ring, 1,2,3-triazole ring, 1,2,4-triazole ring, tetrazole ring, 1,3,4-thiadiazole ring. 1,2,4-thiadiazole ring, 1,3,4-oxadiazole ring, 1,2,4-oxadiazole ring, thiazole ring, oxazole ring, isothiazole ring, isoxazole ring, and these rings Is more preferably a ring fused with a benzene ring or an unsaturated heterocycle. Q ₂ is preferably a carbamoyl group, particularly preferably a carbamoyl group having a hydrogen atom on the nitrogen atom.

In General Formula (A-2), R ₁ represents an alkyl group, an acyl group, an acylamino group, a sulfonamide group, an alkoxycarbonyl group, or a carbamoyl group. R ₂ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acyloxy group, or a carbonate group. R ₃ and R ₄ each represents a group that can be substituted on the benzene ring mentioned in the example of the substituent of formula (A-1). R ₃ and R ₄ may be connected to each other to form a condensed ring.
R ₁ is preferably an alkyl group having 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, an isopropyl group, a butyl group, a tert-octyl group, or a cyclohexyl group), an acylamino group (for example, an acetylamino group, a benzoylamino group, Methylureido group or 4-cyanophenylureido group), carbamoyl group (n-butylcarbamoyl group, N, N-diethylcarbamoyl group, phenylcarbamoyl group, 2-chlorophenylcarbamoyl group, 2,4-dichlorophenylcarbamoyl group, etc.) ) Is more preferably an acylamino group (including a ureido group and a urethane group). R ₂ is preferably a halogen atom (more preferably chlorine atom, bromine atom), an alkoxy group (e.g. methoxy group, a butoxy group, n- hexyloxy group, n- decyloxy group, a cyclohexyl group or a benzyl group), An aryloxy group (such as a phenoxy group or a naphthoxy group);
R ₃ is preferably a hydrogen atom, a halogen atom, or an alkyl group having 1 to 20 carbon atoms, and most preferably a halogen atom. R ₄ is preferably a hydrogen atom, an alkyl group, or an acylamino group, and more preferably an alkyl group or an acylamino group. Examples of these preferable substituents are the same as those for R ₁ . When R ₄ is an acylamino group, R ₄ is preferably linked to R ₃ to form a carbostyryl ring.

In the general formula (A-2), when R ₃ and R ₄ are connected to each other to form a condensed ring, the condensed ring is particularly preferably a naphthalene ring. The same substituent as the example of a substituent quoted by general formula (A-1) may couple | bond with the naphthalene ring. When general formula (A-2) is a naphthol compound, R ₁ is preferably a carbamoyl group. Of these, a benzoyl group is particularly preferable. R ₂ is preferably an alkoxy group or an aryloxy group, and particularly preferably an alkoxy group.

  Hereinafter, preferred specific examples of the development accelerator in the present invention will be given. The present invention is not limited to these.

(Description of hydrogen bonding compound)
When the reducing agent in the present invention has an aromatic hydroxyl group (—OH) or amino group (—NHR, R is a hydrogen atom or an alkyl group), particularly in the case of the aforementioned bisphenols, these groups and hydrogen bonds It is preferable to use together a non-reducing compound having a group capable of forming.
Examples of groups that form hydrogen bonds with hydroxyl groups or amino groups include phosphoryl groups, sulfoxide groups, sulfonyl groups, carbonyl groups, amide groups, ester groups, urethane groups, ureido groups, tertiary amino groups, and nitrogen-containing aromatic groups. Is mentioned. Among them, preferred are a phosphoryl group, a sulfoxide group, an amide group (however, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a urethane group. (However, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a ureido group (however, it does not have a> N—H group, N-Ra (Ra is a substituent other than H).)
In the present invention, a particularly preferred hydrogen bonding compound is a compound represented by the following general formula (D).

In the general formula (D), R ²¹ to R ²³ each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group or a heterocyclic group, and these groups may be substituted even if they are unsubstituted. You may have.
When R ²¹ to R ²³ have a substituent, the substituent is a halogen atom, alkyl group, aryl group, alkoxy group, amino group, acyl group, acylamino group, alkylthio group, arylthio group, sulfonamide group, acyloxy group, Examples thereof include an oxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, and a phosphoryl group. Preferred examples of the substituent include an alkyl group or an aryl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a t-butyl group. Examples thereof include an octyl group, a phenyl group, a 4-alkoxyphenyl group, and a 4-acyloxyphenyl group.
Specific examples of the alkyl group of R ²¹ to R ²³ include a methyl group, an ethyl group, a butyl group, an octyl group, a dodecyl group, an isopropyl group, a t-butyl group, a t-amyl group, a t-octyl group, a cyclohexyl group, Examples thereof include 1-methylcyclohexyl group, benzyl group, phenethyl group, and 2-phenoxypropyl group.
Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-t-butylphenyl group, a 4-t-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group.
Alkoxy groups include methoxy, ethoxy, butoxy, octyloxy, 2-ethylhexyloxy, 3,5,5-trimethylhexyloxy, dodecyloxy, cyclohexyloxy, 4-methylcyclohexyloxy, and A benzyloxy group etc. are mentioned.
Examples of the aryloxy group include phenoxy group, cresyloxy group, isopropylphenoxy group, 4-t-butylphenoxy group, naphthoxy group, and biphenyloxy group.
Examples of the amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, a dioctylamino group, an N-methyl-N-hexylamino group, a dicyclohexylamino group, a diphenylamino group, and an N-methyl-N-phenylamino group. It is done.

R ²¹ to R ²³ are preferably an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. From the viewpoint of the effect of the present invention, at least one of R ²¹ to R ²³ is preferably an alkyl group or an aryl group, and more preferably two or more are an alkyl group or an aryl group. Further, it is preferable that R ²¹ to R ²³ are the same group in that they can be obtained at low cost.
Specific examples of the hydrogen bonding compound including the compound of the general formula (D) in the present invention are shown below, but the present invention is not limited thereto.

Specific examples of the hydrogen bonding compound include those described in European Patent No. 1096310, JP-A No. 2002-156727, and JP-A No. 2002-318431 in addition to the above.
The compound of the general formula (D) in the present invention can be used in a photothermographic material by being incorporated in a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersion fine particle dispersion in the same manner as the reducing agent. It is preferably used as a solid dispersion. These compounds form a hydrogen-bonding complex with a compound having a phenolic hydroxyl group or an amino group in a solution state, and depending on the combination of the reducing agent and the compound of the general formula (D) in the present invention, the compound may be crystallized as a complex. It can be isolated in the state.
The use of the crystal powder isolated in this way as a solid dispersed fine particle dispersion is particularly preferable for obtaining stable performance. Further, a method in which the reducing agent and the compound of the general formula (D) in the present invention are mixed in a powder and complexed at the time of dispersion with a sand grinder mill or the like using an appropriate dispersant can be preferably used.
The compound of the general formula (D) in the present invention is preferably used in the range of 1 mol% to 200 mol%, more preferably in the range of 10 mol% to 150 mol%, based on the reducing agent. More preferably, it is the range of 20 mol% or more and 100 mol%.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose may be added to the image forming layer of the photothermographic material of the invention. The amount of these hydrophilic polymers added is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total binder of the image forming layer.

  The organic silver salt-containing layer (that is, the image forming layer) in the present invention is preferably formed using a polymer latex. The amount of binder in the image forming layer is such that the total binder / organic silver salt mass ratio is 1/10 to 10/1, more preferably 1/3 to 5/1, and still more preferably 1/1 to 3/1. Range.

  Further, such an organic silver salt-containing layer is usually a photosensitive layer (image forming layer) containing a photosensitive silver halide that is a photosensitive silver salt. The mass ratio of silver halide is 400-5, more preferably 200-10.

The total binder amount of the image forming layer in the present invention is preferably 0.2 g / m ² or more and 30 g / m ² or less, more preferably 1 g / m ² or more and 15 g / m ² or less, and further preferably 2 g / m ² or more and 10 g. / M ² or less. In the image forming layer of the present invention, a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like may be added.

(Preferable solvent for coating solution)
In the present invention, the solvent of the image forming layer coating solution of the photothermographic material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is preferably an aqueous solvent containing 50% by mass or more of water. As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, and ethyl acetate may be used. The water content of the solvent of the coating solution is preferably 50% by mass or more, more preferably 70% by mass or more. Examples of preferred solvent compositions include water, water / methyl alcohol = 90/10, water / methyl alcohol = 70/30, water / methyl alcohol / dimethylformamide = 80/15/5, water / methyl alcohol / Ethyl cellosolve = 85/10/5, water / methyl alcohol / isopropyl alcohol = 85/10/5, etc. (numerical values are mass%).

(Description of silver halide)
1) Halogen composition The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and is silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide, or iodide. Silver can be used. Of these, silver bromide, silver iodobromide and silver iodide are preferred. The distribution of the halogen composition in the grain may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Further, silver halide grains having a core / shell structure can be preferably used. A preferable structure is a 2- to 5-fold structure, and more preferably 2- to 4-fold core / shell particles can be used. A technique for localizing silver bromide or silver iodide on the surface of silver chloride, silver bromide or silver chlorobromide grains can also be preferably used.

2) Grain Forming Methods Methods for forming photosensitive silver halide are well known in the art and are described, for example, in Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458. In particular, a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound into gelatin or another polymer solution, and then mixed with an organic silver salt. Use the method. In addition, the method described in paragraph Nos. 0217 to 0224 of JP-A No. 11-119374, and the methods described in JP-A Nos. 11-352627 and 2000-347335 are also preferable.

3) Grain size The grain size of the photosensitive silver halide is preferably small for the purpose of keeping the cloudiness after image formation low, specifically 0.20 μm or less, more preferably 0.01 μm or more and 0.15 μm or less. More preferably, it is 0.02 μm or more and 0.12 μm or less. The grain size here means the diameter when converted into a circular image having the same area as the projected area of silver halide grains (in the case of tabular grains, the projected area of the main plane).

4) Grain shape Examples of the shape of the silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-like grains, and potato-like grains. In the present invention, cubic grains are particularly preferred. Grains with rounded corners of silver halide grains can also be preferably used.
The surface index (Miller index) of the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the {100} plane having high spectral sensitization efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The ratio is preferably 50% or more, more preferably 65% or more, and still more preferably 80% or more. The ratio of the Miller index {100} plane is a T.K. based on the adsorption dependency of {111} plane and {100} plane in the adsorption of sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

5) Heavy Metal The photosensitive silver halide grain of the present invention may contain a metal or metal complex of Group 6 to Group 13 of the Periodic Table (showing Groups 1 to 18). More preferably, a metal or metal complex of Group 6 to Group 10 can be contained. As the central metal of the Group 6 to Group 10 metal or metal complex of the periodic table, rhodium, ruthenium, iridium, and iron are preferable. One kind of these metal complexes may be used, or two or more kinds of complexes of the same metal and different metals may be used in combination. The preferred content is in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol with respect to 1 mol of silver. These heavy metals and metal complexes and methods of adding them are described in JP-A-7-225449, JP-A-11-65021, paragraphs 0018 to 0024, and JP-A-11-119374, paragraphs 0227 to 0240.

In the present invention, silver halide grains in which a hexacyano metal complex is present on the outermost surface of the grains are preferred. Examples of the hexacyano metal complex include [Fe (CN) ₆ ] ⁴⁻ , [Fe (CN) ₆ ] ³⁻ , [Ru (CN) ₆ ] ⁴⁻ , [Os (CN) ₆ ] ⁴⁻ , [Co ( CN) ₆ ] ³⁻ , [Rh (CN) ₆ ] ³⁻ , [Ir (CN) ₆ ] ³⁻ , [Cr (CN) ₆ ] ³⁻ , and [Re (CN) ₆ ] ^3−. It is done. In the present invention, a hexacyano Fe complex is preferred.

  The hexacyano metal complex is present in the form of ions in aqueous solution, so the counter cation is not important, but it is easy to mix with water and is suitable for precipitation of silver halide emulsions. Sodium ion, potassium ion, rubidium It is preferable to use alkali metal ions such as ions, cesium ions and lithium ions, ammonium ions, alkylammonium ions (for example, tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, or tetra (n-butyl) ammonium ions). .

  In addition to water, the hexacyano metal complex is miscible with a mixed solvent or gelatin with an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters, or amides). Can be added.

The addition amount of the hexacyano metal complex is preferably 1 × 10 ⁻⁵ mol or more and 1 × 10 ⁻² mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻³ mol or less per mol of silver.

  In order for the hexacyano metal complex to be present on the outermost surface of the silver halide grain, the chalcogen sensitization of sulfur sensitization, selenium sensitization and tellurium sensitization is completed after the addition of the silver nitrate aqueous solution used for grain formation. It is added directly before the completion of the preparation step before the chemical sensitization step for performing noble metal sensitization such as sensitization and gold sensitization, during the washing step, during the dispersion step, or before the chemical sensitization step. In order to prevent the silver halide fine grains from growing, it is preferable to add the hexacyano metal complex immediately after the grain formation, and it is preferable to add it before the completion of the preparation step.

  The addition of the hexacyano metal complex may be started after adding 96% by mass of the total amount of silver nitrate to be added to form grains, more preferably starting after adding 98% by mass, The addition of 99% by mass is particularly preferable.

  When these hexacyanometal complexes are added after the addition of the aqueous silver nitrate solution just before the completion of grain formation, they can be adsorbed on the outermost surface of the silver halide grains, and most of them form slightly soluble salts with silver ions on the grain surface. To do. Since this silver salt of hexacyanoiron (II) is a less soluble salt than AgI, it is possible to prevent re-dissolution by fine particles and to produce silver halide fine particles having a small particle size. .

Further, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a silver salt emulsion desalting method and a chemical sensitization method which can be contained in the silver halide grains used in the present invention, JP-A-11- No. 84574, paragraph numbers 0046 to 0050, JP-A No. 11-65021, paragraph numbers 0025 to 0031, and JP-A No. 11-119374, paragraph numbers 0242 to 0250.

6) Gelatin As the gelatin contained in the photosensitive silver halide emulsion used in the present invention, various gelatins can be used. It is necessary to maintain a good dispersion state of the photosensitive silver halide emulsion in the coating solution containing an organic silver salt, and gelatin having a molecular weight of 10,000 to 1,000,000 is preferably used. It is also preferable to phthalate the gelatin substituent. These gelatins may be used at the time of grain formation or at the time of dispersion after desalting, but are preferably used at the time of grain formation.

7) Sensitizing Dye Sensitizing dyes applicable to the present invention are those that can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed on silver halide grains, and are suitable for the spectral characteristics of the exposure light source. Sensitizing dyes with sensitivity can be advantageously selected. Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A-11-65021, compounds represented by the general formula (II) of JP-A-10-186572, and general formulas (I) of JP-A-11-119374 ) And the dye described in Example 5 of U.S. Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59-48753. No. 19, line 38 to page 20, line 35 of JP-A-0803764A1, JP-A No. 2001-272747, JP-A No. 2001-290238, JP-A No. 2002-23306, etc. It is described in. These sensitizing dyes may be used alone or in combination of two or more. In the present invention, the time when the sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from desalting to the end of chemical ripening.
The addition amount of the sensitizing dye in the present invention can be set to a desired amount in accordance with sensitivity and fogging performance, but is preferably 10 ⁻⁶ mol to 1 mol per mol of silver halide in the image forming layer, and Preferably it is 10 ^<-4> mol-10 < ^{-1 >} mol.

  In the present invention, a supersensitizer can be used to improve spectral sensitization efficiency. As the supersensitizer used in the present invention, European Patent Publication No. 587,338, US Pat. Nos. 3,877,943, 4,873,184, JP-A-5-341432, 11- 109547, 10-111543, etc. are mentioned.

8) Chemical Sensitization The photosensitive silver halide grain in the invention is preferably chemically sensitized by sulfur sensitizing method, selenium sensitizing method or tellurium sensitizing method. As compounds that are preferably used in the sulfur sensitization method, selenium sensitization method, or tellurium sensitization method, known compounds, for example, compounds described in JP-A-7-128768 can be used. In the present invention, tellurium sensitization is particularly preferred. The compounds described in the literature described in paragraph No. 0030 of JP-A-11-65021, and the general formulas (II), (III), (IV) described in JP-A-5-313284 The compound shown by is more preferable.

The photosensitive silver halide grains in the present invention are preferably chemically sensitized by the gold sensitization method alone or in combination with the chalcogen sensitization. As the gold sensitizer, the gold valence is preferably +1 or +3, and the gold sensitizer is preferably a commonly used gold compound.
Typical examples include chloroauric acid, bromoauric acid, potassium chloroaurate, potassium bromoaurate, auric trichloride, potassium aurothiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, or pyridyltrichloro. Gold or the like is preferable. In addition, gold sensitizers described in US Pat. No. 5,858,637 and Japanese Patent Application No. 2002-278016 are also preferably used.

In the present invention, chemical sensitization can be performed at any time after particle formation and before coating. After desalting, (1) before spectral sensitization, (2) simultaneously with spectral sensitization, (3) spectral After sensitization, there may be (4) immediately before application.
The amount of sulfur, selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but from 10 ⁻⁸ mol to 10 ⁻² mol per mol of silver halide Preferably, about 10 ⁻⁷ mol or more and 10 ⁻³ mol or less is used.
The amount of the gold sensitizer added varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol or more and 10 ⁻³ mol or less, more preferably 10 ⁻⁶ mol or more and 5 × 10 ⁻⁴ mol or less per mol of silver halide. It is.
The conditions for chemical sensitization in the present invention are not particularly limited, but the pH is 5 to 8, the pAg is 6 to 11, and the temperature is about 40 ° C to 95 ° C.
A thiosulfonic acid compound may be added to the silver halide emulsion used in the present invention by the method described in European Patent Publication No. 293,917.

  A reducing agent is preferably used for the photosensitive silver halide grains in the present invention. As specific compounds of the reduction sensitization method, ascorbic acid and aminoiminomethanesulfinic acid are preferable. In addition, it is preferable to use stannous chloride, a hydrazine derivative, a borane compound, a silane compound, or a polyamine compound. The reduction sensitizer may be added at any stage in the photosensitive emulsion production process from crystal growth to the preparation process immediately before coating. Further, reduction sensitization is preferable by ripening while maintaining the pH of the emulsion at 7 or more or pAg at 8.3 or less, and reduction sensitization is achieved by introducing a single addition portion of silver ions during grain formation. It is also preferable to do.

9) Compound in which 1-electron oxidant produced by 1-electron oxidation can emit 1 electron or more electrons In the photothermographic material of the present invention, 1-electron oxidant produced by 1-electron oxidation is 1 electron or 1 electron or more. It is preferable to contain a compound capable of emitting more electrons. The compound can be used alone or in combination with the above-described various chemical sensitizers, and can increase the sensitivity of silver halide.

The one-electron oxidant formed by one-electron oxidation contained in the silver halide photographic light-sensitive material of the present invention is a compound selected from the following types 1 and 2 as the compound capable of emitting one electron or more. It is.
(Type 1)
A compound in which a one-electron oxidant formed by one-electron oxidation can further emit one or more electrons with a subsequent bond cleavage reaction.
(Type 2)
A compound capable of emitting one or more electrons after a one-electron oxidant produced by one-electron oxidation undergoes a subsequent bond formation reaction.

First, the compound of type 1 will be described.
JP-A-9-211769 (specific example: page 28) is a compound of type 1 that can be further released by one-electron oxidant produced by one-electron oxidation with subsequent bond cleavage reaction. Compounds PMT-1 to S-37 described in Table E and Table F on page 32), JP-A-9-211774, JP-A-11-95355 (specific examples: compounds INV1-36), JP 2001-500996 No. (specific examples: compounds 1 to 74, 80 to 87, 92 to 122), US Pat. No. 5,747,235, US Pat. No. 5,747,236, European Patent No. 786692A1 (specific examples: compounds INV 1 to 35) European Patent No. 893732A1, US Pat. No. 6,054,260, US Pat. No. 5,994,051, etc. Compound called donor sensitizer "and the like. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

  Further, as a compound of type 1 that can be emitted by one-electron oxidant formed by one-electron oxidation and further undergoing bond cleavage reaction, one or more electrons can be emitted from the general formula (1) ( General formula (1) described in JP-A-2003-114487), general formula (2) (synonymous with general formula (2) described in JP-A-2003-114487), general formula (3) (JP-A-2003-114487) General formula (1) described in 2003-114488), general formula (4) (synonymous with general formula (2) described in Japanese Patent Application Laid-Open No. 2003-114488), and general formula (5) (Japanese Patent Application Laid-Open No. 2003-114488). 114488 (synonymous with general formula (3)), general formula (6) (synonymous with general formula (1) described in JP-A-2003-75950), and general formula (7) (JP-A-2003-75950). In the general formula (2)), the general formula (8) (Synonymous with the general formula (1) described in JP-A-2004-239934) or the reaction represented by the chemical reaction formula (1) (synonymous with the chemical reaction formula (1) described in JP-A-2004-245929) Among these compounds, compounds represented by the general formula (9) (synonymous with the general formula (3) described in JP-A No. 2004-245929) can be given. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the general formulas (1) and (2), RED ₁ and RED ₂ represent a reducing group. R ₁ represents a non-metallic atomic group capable of forming a cyclic structure corresponding to a tetrahydro form of a 5- or 6-membered aromatic ring (including an aromatic heterocycle) or a hexahydro form together with the carbon atom (C) and RED _1. To express. R ₂ , R ₃ and R ₄ represent a hydrogen atom or a substituent. Lv ₁ and Lv ₂ represent a leaving group. ED represents an electron donating group.

In the general formulas (3), (4) and (5), Z ₁ represents an atomic group capable of forming a 6-membered ring with a nitrogen atom and two carbon atoms of the benzene ring. R ₅ , R ₆ , R ₇ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ , R ₁₈ , and R ₁₉ represent a hydrogen atom or a substituent. R ₂₀ represents a hydrogen atom or a substituent. When R ₂₀ represents a group other than an aryl group, R ₁₆ and R ₁₇ are bonded to each other to form an aromatic ring or an aromatic heterocycle. R ₈ and R ₁₂ represent a substituent that can be substituted on the benzene ring, m1 represents an integer of 0 to 3, and m2 represents an integer of 0 to 4. Lv ₃ , Lv ₄ , and Lv ₅ represent a leaving group.

In general formulas (6) and (7), RED ₃ and RED ₄ represent a reducing group. R _{21 to} R ₃₀ represent a hydrogen atom or a substituent. Z ₂ represents —CR ₁₁₁ R ₁₁₂ —, —NR ₁₁₃ —, or —O—. R ₁₁₁ and R ₁₁₂ each independently represents a hydrogen atom or a substituent. R ₁₁₃ represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

In the general formula (8), RED ₅ is a reducing group and represents an arylamino group or a heterocyclic amino group. R ₃₁ represents a hydrogen atom or a substituent. X represents an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylamino group, an arylamino group, or a heterocyclic amino group. Lv ₆ is a leaving group and represents a carboxy group or a salt thereof, or a hydrogen atom.

The compound represented by the general formula (9) is a compound that undergoes a bond formation reaction represented by the chemical reaction formula (1) by being further oxidized after two-electron oxidation accompanied by decarboxylation has occurred. In chemical reaction formula (1), R ₃₂ and R ₃₃ represent a hydrogen atom or a substituent. Z ₃ represents a group which forms a 5-membered or 6-membered heterocycle with C═C. Z ₄ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation. In the general formula (9), R ₃₂ , R ₃₃ and Z ₃ have the same meanings as those in the chemical reaction formula (1). Z ₅ represents a group which forms a 5- or 6-membered cyclic aliphatic hydrocarbon group or heterocyclic group together with C—C.

Next, the type 2 compound will be described.
As a compound in which a one-electron oxidant produced by one-electron oxidation with a type 2 compound can further emit one or more electrons with a subsequent bond formation reaction, a compound represented by the general formula (10) A compound capable of causing a reaction represented by the general formula (1) described in 2003-140287) and the chemical reaction formula (1) (synonymous with the chemical reaction formula (1) described in JP-A-2004-245929). And a compound represented by the general formula (11) (synonymous with the general formula (2) described in JP-A No. 2004-245929). The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the general formula (10), RED ₆ represents a reducing group that is one-electron oxidized. Y is a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site capable of forming a new bond by reacting with a one-electron oxidant formed by one-electron oxidation of RED _6. Reactive group containing a non-aromatic heterocyclic moiety of a benzo-fused ring. Q represents a linking group that connects RED ₆ and Y.

The compound represented by the general formula (11) is a compound that causes a bond formation reaction represented by the chemical reaction formula (1) by being oxidized. In chemical reaction formula (1), R ₃₂ and R ₃₃ represent a hydrogen atom or a substituent. Z ₃ represents a group which forms a 5-membered or 6-membered heterocycle with C═C. Z ₄ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. Z ₅ represents a group which forms a 5- or 6-membered cyclic aliphatic hydrocarbon group or heterocyclic group together with C—C. M represents a radical, a radical cation, or a cation. In general formula (11), R ₃₂ , R ₃₃ , Z ₃ , and Z ₄ have the same meanings as in chemical reaction formula (1).

  Of the compounds of types 1 and 2, “a compound having an adsorptive group to silver halide in the molecule” or “a compound having a partial structure of a spectral sensitizing dye in the molecule” is preferable. Typical examples of the adsorptive group to silver halide are those described in JP-A No. 2003-156823, page 16, right line 1 to page 17, right line 12. The partial structure of the spectral sensitizing dye is a structure described on page 17, right line 34 to page 18, left line 6 of the same specification.

  More preferably, the compound of type 1 or 2 is “a compound having at least one adsorptive group to silver halide in the molecule”. More preferred is “a compound having two or more adsorptive groups to silver halide in the same molecule”. When two or more adsorptive groups are present in a single molecule, these adsorptive groups may be the same or different.

  The adsorptive group is preferably a mercapto-substituted nitrogen-containing heterocyclic group (for example, 2-mercaptothiadiazole group, 3-mercapto-1,2,4-triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4). -Oxadiazole group, 2-mercaptobenzoxazole group, 2-mercaptobenzthiazole group, or 1,5-dimethyl-1,2,4-triazolium-3-thiolate group), or imino silver (> NAg) A nitrogen-containing heterocyclic group having a —NH— group that can be formed as a partial structure of the heterocyclic ring (for example, a benzotriazole group, a benzimidazole group, or an indazole group). Particularly preferred are 5-mercaptotetrazole group, 3-mercapto-1,2,4-triazole group, and benzotriazole group, most preferred are 3-mercapto-1,2,4-triazole group, and 5 -Mercaptotetrazole group.

  It is also particularly preferred that the adsorptive group has two or more mercapto groups as a partial structure in the molecule. Here, the mercapto group (—SH) may be a thione group if it can be tautomerized. Preferred examples of the adsorptive group having two or more mercapto groups as a partial structure (such as a dimercapto-substituted nitrogen-containing heterocyclic group) include 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, and 3 , 5-dimercapto-1,2,4-triazole group.

A quaternary salt structure of nitrogen or phosphorus is also preferably used as the adsorptive group. Specific examples of the quaternary salt structure of nitrogen include an ammonio group (such as a trialkylammonio group, a dialkylaryl (or heteroaryl) ammonio group, an alkyldiaryl (or heteroaryl) ammonio group) or a quaternized nitrogen atom. A group containing a nitrogen-containing heterocyclic group containing
The quaternary salt structure of phosphorus includes a phosphonio group (trialkylphosphonio group, dialkylaryl (or heteroaryl) phosphonio group, alkyldiaryl (or heteroaryl) phosphonio group, triaryl (or heteroaryl) phosphonio group, etc.). Can be mentioned. More preferably, a quaternary salt structure of nitrogen is used, and more preferably, a 5-membered or 6-membered nitrogen-containing aromatic heterocyclic group containing a quaternized nitrogen atom is used. Particularly preferably, a pyridinio group, a quinolinio group, or an isoquinolinio group is used. These nitrogen-containing heterocyclic groups containing a quaternized nitrogen atom may have an arbitrary substituent.

Examples of quaternary salt counter anions include halogen ions, carboxylate ions, sulfonate ions, sulfate ions, perchlorate ions, carbonate ions, nitrate ions, BF ₄ ⁻ , PF ₆ ⁻ , and Ph ₄ B ^{− and the} like. Can be mentioned. When a group having a negative charge in a carboxylate group or the like is present in the molecule, an inner salt may be formed together with the group. As a counter anion not present in the molecule, a chlorine ion, a bromo ion, or a methanesulfonate ion is particularly preferable.

  A preferred structure of the compound represented by type 1 or 2 having a quaternary salt structure of nitrogen or phosphorus as the adsorptive group is represented by the general formula (X).

In general formula (X), P and R each independently represent a quaternary salt structure of nitrogen or phosphorus that is not a partial structure of a sensitizing dye. Q ₁ and Q ₂ each independently represent a linking group, specifically a single bond, an alkylene group, an arylene group, a heterocyclic group, —O—, —S—, —NR _N —, —C (═O ) —, —SO ₂ —, —SO—, —P (═O) — each independently or a combination of these groups. Here, _RN represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. S is a residue obtained by removing one atom from a compound represented by type (1) or (2). i and j are integers of 1 or more, and i + j is selected from the range of 2-6. Preferably, i is 1 to 3, and j is 1 to 2, more preferably i is 1 or 2, and j is 1, and particularly preferably i is 1 and j is 1. The compound represented by the general formula (X) preferably has a total carbon number of 10 to 100. More preferably, it is 10-70, More preferably, it is 11-60, Most preferably, it is 12-50.

  The compounds of type 1 and type 2 in the present invention may be used at any time during the preparation of the photosensitive silver halide emulsion and during the process of producing the photothermographic material. For example, at the time of photosensitive silver halide grain formation, desalting step, chemical sensitization, before coating. Moreover, it can also add in several steps in these processes. The addition position is preferably from the end of formation of the photosensitive silver halide grains to before the desalting step, at the time of chemical sensitization (immediately after the start of chemical sensitization to immediately after completion), and before application, more preferably from the time of chemical sensitization. Until before mixing with the non-photosensitive organic silver salt.

  The compounds of type 1 and type 2 in the present invention are preferably added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. When the compound is dissolved in water, the compound having higher solubility when the pH is raised or lowered may be dissolved at a higher or lower pH and added.

The compounds of type 1 and type 2 in the present invention are preferably used in an image forming layer containing a photosensitive silver halide and a non-photosensitive organic silver salt, but the photosensitive silver halide and the non-photosensitive organic silver salt are used. It may be added to the protective layer or intermediate layer together with the image forming layer containing, and diffused during coating. The timing of addition of these compounds is preferably 1 × 10 ⁻⁹ mol to 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁸ mol, per mol of silver halide, regardless of before and after the sensitizing dye. It is contained in a silver halide emulsion layer (image forming layer) at a ratio of ˜5 × 10 ⁻² mol.

10) Adsorbing redox compound having an adsorbing group and a reducing group In the present invention, it is preferable to contain an adsorbing redox compound having an adsorbing group and a reducing group for silver halide in the molecule. The adsorptive redox compound is preferably a compound represented by the following formula (I).

Formula (I) A- (W) n-B
In the formula (I), A represents a group capable of adsorbing to silver halide (hereinafter referred to as an adsorbing group), W represents a divalent linking group, n represents 0 or 1, and B represents a reducing group. To express.

  In the formula (I), the adsorption group represented by A is a group that directly adsorbs to silver halide, or a group that promotes adsorption to silver halide, and specifically, a mercapto group (or a salt thereof). , A thione group (—C (═S) —), a heterocyclic group, a sulfide group, a disulfide group, a cationic group, or an ethynyl group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom, and a tellurium atom Etc.

The mercapto group (or salt thereof) as the adsorptive group means the mercapto group (or salt thereof) itself, and more preferably, a heterocyclic group or aryl group substituted with at least one mercapto group (or salt thereof) or Represents an alkyl group. Here, the heterocyclic group is at least a 5- to 7-membered monocyclic or condensed aromatic or non-aromatic heterocyclic group such as an imidazole ring group, a thiazole ring group, an oxazole ring group, or a benzimidazole ring. Group, benzothiazole ring group, benzoxazole ring group, triazole ring group, thiadiazole ring group, oxadiazole ring group, tetrazole ring group, purine ring group, pyridine ring group, quinoline ring group, isoquinoline ring group, pyrimidine ring group, And triazine ring group. Further, it may be a heterocyclic group containing a quaternized nitrogen atom. In this case, the substituted mercapto group may be dissociated to form a meso ion. When the mercapto group forms a salt, the counter ion includes a cation such as alkali metal, alkaline earth metal, heavy metal (Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ag ⁺ , or Zn ²⁺ ), ammonium ion, Examples thereof include a heterocyclic group containing a quaternized nitrogen atom, and a phosphonium ion.
Further, the mercapto group as the adsorptive group may be tautomerized into a thione group.

The thione group as an adsorbing group also includes a chain or cyclic thioamide group, thioureido group, thiourethane group, or dithiocarbamate group.
A heterocyclic group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom and a tellurium atom as the adsorptive group is a -NH- group capable of forming imino silver (> NAg) as a partial structure of the heterocyclic ring. A nitrogen-containing heterocyclic group, or a “—S—” group, a “—Se—” group, a “—Te—” group, or a “═N—” group that can be coordinated to a silver ion by a coordination bond. A heterocyclic group having a partial structure of benzotriazole group, triazole group, indazole group, pyrazole group, tetrazole group, benzimidazole group, imidazole group, purine group, etc. , Thiazole group, oxazole group, benzothiophene group, benzothiazole group, benzoxazole group, thiadiazole group, oxadiazole group, tri Jin group, seleno azole group, benzoselenazole group, tellurium azole group, and the like benzo tellurium azole group.
Examples of the sulfide group or disulfide group as the adsorptive group include all groups having a partial structure of -S- or -SS-.
The cationic group as the adsorptive group means a group containing a quaternized nitrogen atom, specifically, an ammonio group or a group containing a nitrogen-containing heterocyclic group containing a quaternized nitrogen atom. Examples of the nitrogen-containing heterocyclic group containing a quaternized nitrogen atom include a pyridinio group, a quinolinio group, an isoquinolinio group, and an imidazolio group.
An ethynyl group as an adsorptive group means a —C≡CH group, and the hydrogen atom may be substituted.
The adsorbing group may have an arbitrary substituent.

  Further, specific examples of the adsorbing group are further described in JP-A-11-95355, p. 4-p. 7 are mentioned.

  In the formula (I), preferred as the adsorptive group represented by A is a mercapto-substituted heterocyclic group (for example, 2-mercaptothiadiazole group, 2-mercapto-5-aminothiadiazole group, 3-mercapto-1,2,4). -Triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4-oxadiazole group, 2-mercaptobenzimidazole group, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, 3,5-dimercapto-1,2,4-triazole group, or 2,5-dimercapto-1,3-thiazole group), Alternatively, a nitrogen-containing heterocyclic group having a —NH— group that can form imino silver (> NAg) as a heterocyclic partial structure (for example, benzoto) Azole group, benzimidazole group, an indazole group), more preferable as an adsorptive group is a 2-mercaptobenzimidazole group, a 3,5-dimercapto-1,2,4-triazole group.

In formula (I), W represents a divalent linking group. Any linking group may be used as long as it does not adversely affect photographic properties. For example, a divalent linking group composed of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom can be used. Specifically, an alkylene group having 1 to 20 carbon atoms (for example, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, etc.), an alkenylene group having 2 to 20 carbon atoms, and an alkynylene group having 2 to 20 carbon atoms. , An arylene group having 6 to 20 carbon atoms (eg, phenylene group, naphthylene group, etc.), —CO—, —SO ₂ —, —O—, —S—, —NR ₁ —, combinations of these linking groups, and the like. It is done. Here, R ₁ represents a hydrogen atom, an alkyl group, a heterocyclic group, or an aryl group.
The linking group represented by W may have an arbitrary substituent.

  In formula (I), the reducing group represented by B represents a group capable of reducing silver ions. For example, a triple bond group such as formyl group, amino group, acetylene group or propargyl group, mercapto group, hydroxylamines. Hydroxamic acids, hydroxyureas, hydroxyurethanes, hydroxysemicarbazides, reductones (including reductone derivatives), anilines, phenols (chroman-6-ols, 2,3-dihydrobenzofuran-5-ols, (Including aminophenols, sulfonamidophenols, and hydroquinones, catechols, resorcinols, polyphenols such as benzenetriols, bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. Residue with one removed And the like. Of course, these may have an arbitrary substituent.

In the formula (I), the reducing group represented by B shows its oxidation potential, Akira Fujishima “Electrochemical Measurement Method” (pages 150-208, published by Gihodo Publishing) and the Chemical Society of Japan “Experimental Chemistry Course” 4th edition. It can be measured using the measuring method described in (Vol. 9, pages 282-344, Maruzen). For example, by a rotating disk voltammetry technique, specifically, a sample is dissolved in a solution of methanol: pH 6.5 Briton-Robinson buffer (10%: 90% (volume%)) and nitrogen gas is used for 10 minutes. , A glassy rotating disk electrode (RDE) is used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, 25 ° C., 1000 rev / min, 20 mV / sec. Can be measured at sweep speed. A half-wave potential (E1 / 2) can be obtained from the obtained voltammogram.
In the present invention, the reducing group represented by B preferably has an oxidation potential in the range of about -0.3 V to about 1.0 V when measured by the above measurement method. More preferably, it is in the range of about -0.1V to about 0.8V, and particularly preferably in the range of about 0V to about 0.7V.

  In the formula (I), the reducing group represented by B is preferably selected from hydroxylamines, hydroxamic acids, hydroxyureas, hydroxysemicarbazides, reductones, phenols, acylhydrazines, carbamoylhydrazines, and 3-pyrazolidones. A residue obtained by removing one hydrogen atom.

  The compound of the formula (I) in the present invention may be one in which a ballast group or polymer chain commonly used in an immobile photographic additive such as a coupler is incorporated. Examples of the polymer include those described in JP-A-1-100530.

  The compound of the formula (I) in the present invention may be a bis form or a tris form. The molecular weight of the compound of formula (I) in the present invention is preferably between 100 and 10000, more preferably between 120 and 1000, particularly preferably between 150 and 500.

  Examples of the compound of formula (I) in the present invention are shown below, but the present invention is not limited thereto.

  Furthermore, specific compounds 1 to 30 and 1 ″ -1 to 1 ″ -77 described in European Patent No. 1308776A2 p73 to p87 are also preferable examples of the compound having an adsorbing group and a reducing group in the present invention.

  These compounds can be easily synthesized according to known methods. As the compound of the formula (I) in the present invention, one kind of compound may be used alone, but it is also preferred to use two or more kinds of compounds at the same time. When two or more kinds of compounds are used, they may be added in the same layer or in different layers, and the addition method may be different.

The compound of formula (I) in the present invention is preferably added to the silver halide image forming layer, and more preferably added during the preparation of the emulsion. When added at the time of emulsion preparation, it can be added at any time during the process. For example, silver halide grain formation process, before desalting process start, desalting process, chemical ripening Examples include a step before starting, a chemical ripening step, and a step before preparing a finished emulsion. Moreover, it can also add in several steps in these processes. Although it is preferably used for the image forming layer, it may be added to the adjacent protective layer or intermediate layer together with the image forming layer and diffused during coating.
The preferred addition amount largely depends on the above-mentioned addition method and the kind of compound to be added, but generally 1 × 10 ⁻⁶ mol to 1 mol, preferably 1 × 10 ⁻⁵ mol per mol of photosensitive silver halide. The amount is 5 × 10 ⁻¹ mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻¹ mol or less.

  The compound of the formula (I) in the present invention can be added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. At this time, the pH may be appropriately adjusted with an acid or a base, and a surfactant may be allowed to coexist. Furthermore, it can also be dissolved in a high boiling point organic solvent and added as an emulsified dispersion. It can also be added as a solid dispersion.

11) Combination of a plurality of silver halides The photosensitive silver halide emulsion in the photothermographic material used in the invention may be only one kind, or two or more kinds (for example, those having different average grain sizes or different halogen compositions). Those having different crystal habits, those having different chemical sensitization conditions) may be used in combination. The gradation can be adjusted by using a plurality of types of photosensitive silver halides having different sensitivities. As techniques relating to these, there are JP-A-57-119341, 53-106125, 47-3929, 48-55730, 46-5187, 50-73627, 57-150841, and the like. Can be mentioned. The sensitivity difference is preferably 0.2 log E or more for each emulsion.

12) Application amount The addition amount of the photosensitive silver halide is preferably 0.03 g / m ² or more and 0.6 g / m ² or less, expressed as the amount of silver applied per 1 m ² of the light-sensitive material. / M ² or more and 0.4 g / m ² or less is more preferable, and 0.07 g / m ² or more and 0.3 g / m ² or less is most preferable. The functional silver halide is preferably from 0.01 mol to 0.5 mol, more preferably from 0.02 mol to 0.3 mol, and still more preferably from 0.03 mol to 0.2 mol.

13) Mixing of photosensitive silver halide and organic silver salt Regarding the mixing method and mixing conditions of separately prepared photosensitive silver halide and organic silver salt, the silver halide grains and the organic silver salt that were prepared are respectively stirred at high speed. Prepare an organic silver salt by mixing with a machine, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc., or by mixing photosensitive silver halide that has been prepared at any time during the preparation of the organic silver salt However, there is no particular limitation as long as the effects of the present invention are sufficiently exhibited. In addition, mixing two or more organic silver salt aqueous dispersions and two or more photosensitive silver salt aqueous dispersions when mixing is a preferred method for adjusting photographic characteristics.

14) Mixing of silver halide into coating solution The preferred addition time of silver halide into the image forming layer coating solution is from 180 minutes before application, preferably from 60 minutes to 10 seconds before application. The method and mixing conditions are not particularly limited as long as the effects of the present invention are sufficiently exhibited. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is a desired time. Harnby, M.M. F. Edwards, A.D. W. There is a method of using a static mixer described in Chapter 8 of Nienow's Koji Takahashi's “Liquid mixing technology” (published by Nikkan Kogyo Shimbun, 1989).

(Anti-fogging agent)
Antifogging agents, stabilizers and stabilizer precursors that can be used in the present invention are paragraph No. 0070 of JP-A-10-62899, page 20 line 57 to page 21, line 7 of EP-A-0803764. And the compounds described in JP-A-9-281737 and JP-A-9-329864, and the compounds described in US Pat. No. 6,083,681 and European Patent 1048875.

1) Organic polyhalogen compound Hereinafter, preferred organic polyhalogen compounds that can be used in the present invention will be described in detail. A preferred polyhalogen compound in the present invention is a compound represented by the following general formula (H).
General formula (H)
Q- (Y) n-C (Z ₁ ) (Z ₂ ) X
In General Formula (H), Q represents an alkyl group, an aryl group, or a heterocyclic group, Y represents a divalent linking group, n represents 0 to ₁ , Z ₁ and Z ₂ represent a halogen atom, X represents a hydrogen atom or an electron withdrawing group.
In general formula (H), Q is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heterocyclic group containing at least one nitrogen atom (pyridine, quinoline group, etc.).
In the general formula (H), when Q is an aryl group, Q preferably represents a phenyl group substituted with an electron-attracting group having a positive Hammett's substituent constant σp. For Hammett's substituent constants, see Journal of Medicinal Chemistry, 1973, Vol. 16, no. 11, 1207-1216 etc. can be referred to.
Examples of such an electron withdrawing group include a halogen atom, an alkyl group substituted with an electron withdrawing group, an aryl group substituted with an electron withdrawing group, a heterocyclic group, an alkyl or arylsulfonyl group, acyl Group, alkoxycarbonyl group, carbamoyl group, sulfamoyl group and the like. Particularly preferred as the electron withdrawing group is a halogen atom, a carbamoyl group, or an arylsulfonyl group, and a carbamoyl group is particularly preferred.
X is preferably an electron withdrawing group. Preferred electron withdrawing groups are halogen atoms, aliphatic / aryl or heterocyclic sulfonyl groups, aliphatic / aryl or heterocyclic acyl groups, aliphatic / aryl or heterocyclic oxycarbonyl groups, carbamoyl groups, sulfamoyl groups, More preferred are a halogen atom and a carbamoyl group, and particularly preferred is a bromine atom.
Z ₁ and Z ₂ are preferably a bromine atom or an iodine atom, and more preferably a bromine atom.
Y preferably represents _{-C (= O) -, -} SO -, - SO 2 -, - C (= O) N (R) -, - SO 2 N (R) - , more preferably -C ( ═O) —, —SO ₂ —, —C (═O) N (R) —, and particularly preferably —SO ₂ —, —C (═O) N (R) —. R here represents a hydrogen atom, an aryl group or an alkyl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.
n represents 0 or 1, and is preferably 1.
In General Formula (H), when Q is an alkyl group, preferred Y is —C (═O) N (R) —, and when Q is an aryl group or a heterocyclic group, preferred Y is —SO ₂ —. is there.
In the general formula (H), a form in which residues obtained by removing a hydrogen atom from the compound are bonded to each other (generally referred to as a bis type, a tris type, or a tetrakis type) can also be preferably used.
In the general formula (H), a dissociable group (for example, a COOH group or a salt thereof, a SO ₃ H group or a salt thereof, a PO ₃ H group or a salt thereof), a group containing a quaternary nitrogen cation (for example, an ammonium group or a pyridinium group) Etc.), those having a polyethyleneoxy group, a hydroxyl group or the like as a substituent are also preferred forms.

  Specific examples of the compound represented by formula (H) in the present invention are shown below.

  Polyhalogen compounds that can be used in the present invention other than those described above include US Pat. No. 3,874,946, US Pat. No. 4,756,999, US Pat. No. 5,340,712, US Pat. No. 5,369,000, US Pat. No. 5,464,537, US Pat. 119624, 59-57234, JP-A-7-2781, 7-5621, 9-160164, 9-244177, 9-244178, 9-160167, 9- 319022, 9-258367, 9-265150, 9-319022, 10-197988, 10-197989, 11-242304, JP 2000-2963, JP 2000-11270 , JP2000-284410, JP2 The compounds listed as exemplary compounds of the invention in 00-284212, JP-A-2001-33911, JP-A-2001-31644, JP-A-2001-312027, and JP-A-2003-50441 are preferably used. In particular, compounds specifically exemplified in JP-A-7-2781, JP-A-2001-33911, and JP-A-2001-312027 are preferred.

The compound represented by formula (H) in the present invention is preferably used in the range of 10 ⁻⁴ mol to 1 mol, more preferably 10 ⁻³ , per mol of the non-photosensitive silver salt in the image forming layer. It is preferable to use in the range of not less than 0.5 mol and not more than 0.5 mol, more preferably not less than 1 × 10 ⁻² mol and not more than 0.2 mol.
In the present invention, examples of the method for incorporating the antifoggant into the photothermographic material include the methods described in the method for containing a reducing agent, and the organic polyhalogen compound is also preferably added as a solid fine particle dispersion.

2) Other antifoggants Other antifoggants include mercury (II) salts described in paragraph No. 0113 of JP-A No. 11-65021, benzoic acids described in paragraph No. 0114 of the same, salicylic acid derivatives of JP-A No. 2000-206642, A formalin scavenger compound represented by the formula (S) in JP-A-2000-221634, a triazine compound according to claim 9 in JP-A-11-352624, and a compound represented by the general formula (III) in JP-A-6-11791 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene and the like.

The photothermographic material in the invention may contain an azolium salt for the purpose of preventing fogging. Examples of the azolium salt include compounds represented by general formula (XI) described in JP-A-59-193447, compounds described in JP-B-55-12581, and general formula (II) described in JP-A-60-153039. And the compounds represented. The azolium salt may be added to any part of the photothermographic material, but the addition layer is preferably added to the layer having the image forming layer, and more preferably to the image forming layer. The azolium salt may be added at any step during the preparation of the coating solution, and when added to the image forming layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. Immediately before is preferable. The azolium salt may be added by any method such as powder, solution, fine particle dispersion.
Moreover, you may add as a solution mixed with other additives, such as a sensitizing dye, a reducing agent, and a color toning agent.
In the present invention, the azolium salt may be added in any amount, but preferably 1 × 10 ⁻⁶ mol to 2 mol, and more preferably 1 × 10 ⁻³ mol to 0.5 mol, per mol of silver.

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used for the purpose of controlling development by suppressing or promoting development, improving spectral sensitization efficiency, and improving storage stability before and after development. And thione compounds, paragraphs 0067 to 0069 of JP-A-10-62899, compounds represented by formula (I) of JP-A-10-186572, and specific examples thereof include paragraph numbers 0033 to 0052. , European Patent Publication No. 0803764A1, page 20, lines 36-56. Of these, mercapto-substituted heteroaromatic compounds described in JP-A-9-297367, JP-A-9-304875, JP-A-2001-100388, JP-A-2002-303954, JP-A-2002-303951, and the like are preferable. .

2) Toning Agent In the photothermographic material of the present invention, it is preferable to add a toning agent. For the toning agent, paragraph Nos. 0054 to 0055 of JP-A No. 10-62899, page 21 to No. 23 of European Patent Publication No. 0803764A1. Line 48, described in JP-A No. 2000-356317 and JP-A No. 2000-187298, and in particular, phthalazinones (phthalazinone, phthalazinone derivatives or metal salts; for example, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone. 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione); phthalazinones and phthalic acids (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, diammonium phthalate) , Sodium phthalate, potassium phthalate and tetrachlorophthalic anhydride) Combination; Phthalazine (phthalazine, phthalazine derivative or metal salt; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine And 2,3-dihydrophthalazine); a combination of phthalazines and phthalic acids is preferable, and a combination of phthalazines and phthalic acids is particularly preferable. Among them, a particularly preferable combination is a combination of 6-isopropylphthalazine and phthalic acid or 4-methylphthalic acid.

3) Plasticizers and lubricants In the present invention, known plasticizers and lubricants can be used to improve film physical properties. In particular, it is preferable to use a lubricant such as liquid paraffin, a long chain fatty acid, a fatty acid amide, and a fatty acid ester in order to improve handling during production and scratch resistance during thermal development. Particularly preferred are liquid paraffin from which low-boiling components have been removed and fatty acid esters having a branched structure and having a molecular weight of 1000 or more.
Regarding the plasticizer and lubricant that can be used in the image forming layer and the non-photosensitive layer, JP-A No. 11-65021, paragraph No. 0117, JP-A No. 2000-5137, JP-A No. 2004-219794, JP-A No. 2004-219802, The compounds described in JP-A-2004-334077 are preferred.

4) Dye and Pigment In the image forming layer of the present invention, various dyes and pigments (for example, CI Pigment Blue 60, CI, etc.) are used from the viewpoints of color tone improvement, prevention of interference fringes during laser exposure, and prevention of irradiation. Pigment Blue 64, CI Pigment Blue 15: 6) can be used. These are described in detail in WO 98/36322, JP-A Nos. 10-268465 and 11-338098, and the like.

5) Nucleating Agent In the photothermographic material of the invention, it is preferable to add a nucleating agent to the image forming layer. Regarding the nucleating agent, the addition method and the addition amount thereof, paragraph No. 0118 of JP-A No. 11-65021, paragraph Nos. 0136 to 0193 of JP-A No. 11-223898, and formula (H) of JP-A No. 2000-284399. , Compounds of formulas (1) to (3), formulas (A) and (B), compounds of general formulas (III) to (V) described in JP-A 2000-347345 (specific compounds: The nucleation promoter is described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

  In order to use formic acid or formate as a strong fogging substance, it is preferably contained in an amount of 5 mmol or less, more preferably 1 mmol or less per mol of silver on the side having an image forming layer containing photosensitive silver halide.

When a nucleating agent is used in the photothermographic material of the present invention, it is preferable to use an acid formed by hydrating diphosphorus pentoxide or a salt thereof in combination. Acids or salts thereof formed by hydration of diphosphorus pentoxide include metaphosphoric acid (salt), pyrophosphoric acid (salt), orthophosphoric acid (salt), triphosphoric acid (salt), tetraphosphoric acid (salt), hexametalin An acid (salt) etc. can be mentioned. Examples of the acid or salt thereof formed by hydrating diphosphorus pentoxide particularly preferably include orthophosphoric acid (salt) and hexametaphosphoric acid (salt). Specific examples of the salt include sodium orthophosphate, sodium dihydrogen orthophosphate, sodium hexametaphosphate, and ammonium hexametaphosphate.
The amount of acid or salt thereof formed by hydration of diphosphorus pentoxide (the coating amount per 1 m ^{2 of} photosensitive material) may be a desired amount according to the performance such as sensitivity and fogging, but 0.1 mg / m ² It is preferably 500 mg / m ² or less, more preferably 0.5 mg / m ² or more and 100 mg / m ² or less.

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution in the invention is preferably from 30 ° C. to 65 ° C., more preferably from 35 ° C. to less than 60 ° C., and more preferably from 35 ° C. to 55 ° C. Moreover, it is preferable that the temperature of the image forming layer coating liquid immediately after the addition of the polymer latex is maintained at 30 ° C. or higher and 65 ° C. or lower.

(Layer structure and components)
The photothermographic material of the present invention can have a non-photosensitive layer in addition to the image forming layer. The non-photosensitive layer includes (a) a surface protective layer provided on the image forming layer (on the side farther than the support) from the arrangement thereof, and (b) an intermediate layer provided between the image forming layer and the surface protective layer. (C) an undercoat layer provided between the image forming layer and the support, and (d) a back layer provided on the opposite side of the support from the image forming layer.

  In addition, although a layer acting as an optical filter can be provided, it is provided as the layer (a) or (b). The antihalation layer is provided in the photothermographic material as the layer (c) or (d).

  In the present invention, preferably, the silver salt of the aforementioned heterocyclic compound is contained in (a), (b), or (c), that is, the non-photosensitive layer on the same side as the image forming layer. More preferably, it is contained in (a) or (b). More preferably, (b) contains a silver salt of the aforementioned heterocyclic compound (this layer may be referred to as an intermediate layer A in the following description). A second non-photosensitive layer (which may be referred to as an intermediate layer B in the following description) may be disposed between the image forming layer and the (b) layer.

1) Binder of Intermediate Layer A and Intermediate Layer B In the present invention, at least 50% by mass of the binder of the intermediate layer A and the intermediate layer B is preferably a polymer latex. As the remaining binder component, a hydrophilic polymer described later is preferably used. In addition to the binder, additives such as a development accelerator or an antifogging agent, a dye or pigment, a plasticizer or a lubricant, a crosslinking agent, and a surfactant may be contained.

  A preferred polymer latex is a polymer latex having a monomer component represented by the following general formula (M) of 10% by mass or more and 70% by mass or less.

General formula (M)
CH ₂ = CR ⁰¹ -CR ⁰² = CH ₂
In the formula, R ⁰¹ and R ⁰² are groups selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, and a cyano group. More preferably, R ⁰¹ and R ⁰² are both hydrogen atoms, or one is a hydrogen atom and the other is a methyl group.

The preferred alkyl group for R ⁰¹ and R ^{02 is} an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms. The halogen atom for R ⁰¹ and R ⁰² is preferably a fluorine atom, a chlorine atom or a bromine atom, and more preferably a chlorine atom.
R ⁰¹ and R ⁰² are preferably both hydrogen atoms, one is a hydrogen atom and the other is a methyl group or a chlorine atom, more preferably both are hydrogen atoms, or one is a hydrogen atom and the other is a methyl group.

  Specific examples of the monomer represented by the general formula (M) of the present invention include 2-ethyl-1,3-butadiene, 2-n-propyl-1,3-butadiene, and 2,3-dimethyl-1,3. -Butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-fluoro-1,3-butadiene, 2,3-dichloro- Examples include 1,3-butadiene and 2-cyano-1,3-butadiene.

The copolymerization ratio of the monomer represented by the general formula (M) in the present invention is 10% by mass to 70% by mass, preferably 15% by mass to 65% by mass, and more preferably 20% by mass to 60% by mass. %. When the copolymerization ratio of the monomer represented by the general formula (M) is less than 10% by mass, the fusion component of the binder decreases, and the work brittleness deteriorates.
On the other hand, when the copolymerization ratio of the monomer represented by the general formula (M) exceeds 70% by mass, the fusion component of the binder is increased and the mobility of the binder is increased, so that the image storage stability is deteriorated.

  As the acid group, carboxylic acid, sulfonic acid, or phosphoric acid is preferable, and carboxylic acid is particularly preferable. The copolymerization ratio of the acid group is preferably 1% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass. Specific examples of the monomer having an acid group include acrylic acid, methacrylic acid, itaconic acid, p-styrenesulfonic acid sodium salt, isoprenesulfonic acid, and phosphorylethyl methacrylate, and acrylic acid and methacrylic acid are preferable. Acid is particularly preferred.

  The binder of the present invention preferably has a glass transition temperature (Tg) in the range of −30 ° C. to 70 ° C., more preferably in the range of −10 ° C. to 50 ° C., more preferably in terms of film formability and image storage stability. Is in the range of 0 ° C to 40 ° C. It is also possible to use a blend of two or more polymers as the binder, and in this case, it is preferable that the weighted average Tg in consideration of the composition falls within the above range. Moreover, when phase-separating or having a core-shell structure, the weighted average Tg is preferably within the above range.

This glass transition temperature (Tg) can be calculated by the following formula.
1 / Tg = Σ (Xi / Tgi)
Here, it is assumed that n monomer components from i = 1 to n are copolymerized in the polymer.
Xi is the mass fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. In addition, the value (Tgi) of the homopolymer glass transition temperature of each monomer employ | adopted the value of Polymer Handbook (3rd Edition) (J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

  The polymer used for the binder of the present invention can be easily obtained by a solution polymerization method, suspension polymerization method, emulsion polymerization method, dispersion polymerization method, anionic polymerization method, cationic polymerization, etc., but the emulsion polymerization method obtained as a latex Is most preferred. In the emulsion polymerization method, for example, water or a mixed solvent of water and an organic solvent miscible with water (for example, methanol, ethanol, acetone, etc.) is used as a dispersion medium, and 5 mass% to 150 mass% with respect to the dispersion medium. The polymerization is carried out by stirring at 30 ° C. to 100 ° C., preferably 60 ° C. to 90 ° C. for 3 hours to 24 hours, using an emulsifier and a polymerization initiator with respect to the total monomer amount. Various conditions such as the dispersion medium, the monomer concentration, the initiator amount, the emulsifier amount, the dispersant amount, the reaction temperature, and the monomer addition method are appropriately set in consideration of the type of monomer used. Moreover, it is preferable to use a dispersing agent as needed.

The emulsion polymerization method can be generally performed according to the following literature. "Synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki, published by Polymer Press (1978))", "Application of Synthetic Latex (Takaaki Sugimura, Tatsuo Kataoka, Junichi Suzuki, Keiji Kasahara, Published by Polymer Press (1993) ) ”,“ Synthetic Latex Chemistry (Muroichi Muroi, published by Kobunshi Shuppankai (1970)) ”.
In the emulsion polymerization method for synthesizing the polymer latex of the present invention, a batch polymerization method, a monomer (continuous and divided) addition method, an emulsion addition method, a seed polymerization method, and the like can be selected. From the viewpoint of latex productivity, A polymerization method, a monomer (continuous / divided) addition method, and an emulsion addition method are preferred.

  The polymerization initiator only needs to have radical generating ability, such as inorganic peroxides such as persulfate and hydrogen peroxide, peroxides described in Nippon Oil & Fats Co., Ltd. organic peroxide catalog, and Wako Pure Chemical Industries, Ltd. The azo compounds described in the azo polymerization initiator catalog can be used. Among these, water-soluble peroxides such as persulfate and water-soluble azo compounds described in the Wako Pure Chemical Industries, Ltd. Azo Polymerization Initiator Catalog are preferable. Ammonium persulfate, sodium persulfate, potassium persulfate, azobis ( 2-methylpropionamidine) hydrochloride, azobis (2-methyl-N- (2-hydroxyethyl) propionamide), azobiscyanovaleric acid is more preferable, and in particular, peroxidation such as ammonium persulfate, sodium persulfate, potassium persulfate and the like. The product is preferable from the viewpoint of image preservability, solubility, and cost.

  As the addition amount of the polymerization initiator, the polymerization initiator is preferably 0.3% by mass to 2.0% by mass, and 0.4% by mass to 1.75% by mass with respect to the total amount of monomers. Is more preferable, and 0.5% by mass to 1.5% by mass is particularly preferable. When the amount of the polymerization initiator is less than 0.3% by mass, the image storability is lowered, and when it exceeds 2.0%, the latex tends to aggregate and the coatability is lowered.

  As the polymerization emulsifier, any of an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used, but the anionic surfactant has dispersibility and image storability. From the viewpoint, it is preferable to use a sulfonic acid type anionic surfactant because polymerization stability can be secured in a small amount and it has hydrolysis resistance, and long-chain alkyl diphenyl ether disulfone represented by Perex SS-H (Kao Co., Ltd.). Acid salts are more preferable, and a low electrolyte type such as Pionine A-43-S (Takemoto Yushi Co., Ltd.) is particularly preferable.

  As the polymerization emulsifier, a sulfonic acid type anionic surfactant is preferably used in an amount of 0.1% by mass to 10.0% by mass with respect to the total amount of monomers, and 0.2% by mass to 7.5% by mass is used. It is more preferable that 0.3% by mass to 5.0% by mass is used. If the polymerization emulsifier is less than 0.1% by mass, stability during emulsion polymerization cannot be ensured, and if it exceeds 10.0%, the image storage stability decreases.

  In the synthesis of the polymer latex used in the present invention, it is preferable to use a chelating agent. The chelating agent is a compound capable of coordinating (chelating) multivalent ions such as metal ions such as iron ions and alkaline earth metal ions such as calcium ions. Japanese Patent Publication No. 6-8956, US Pat. JP-A-73645, JP-A-4-127145, JP-A-4-247703, JP-A-4-305572, JP-A-6-11805, JP-A-5-173712, JP-A-5-66527, JP-A-5-66527. 158195, JP-A-6-118580, JP-A-6-110168, JP-A-6-161054, JP-A-6-175299, JP-A-6-214352, JP-A-7-114161, JP-A-7-114154 JP-A-7-120894, JP-A-7-199433, JP-A-7-306504, JP-A-9-43792 , JP-A-8-314090, JP-A-10-182571, JP-A-10-182570, can be employed compounds described in JP-A-11-190892.

  Examples of the chelating agent include inorganic chelate compounds (sodium tripolyphosphate, sodium hexametaphosphate, sodium tetrapolyphosphate, etc.), aminopolycarboxylic acid chelate compounds (nitrilotritriacetic acid, ethylenediaminetetraacetic acid, etc.), organic phosphonic acid chelate compounds ( Research Disclosure 18170, JP-A-52-102726, 53-42730, 56-97347, 54-121127, 55-4024, 55-4025, 55-29883, 55 -126241, 55-65955, 55-65956, 57-17943, 54-61125, and West German Patent No. 1045373), polyphenol-based chelating agents, polyamine-based chelates Preferably such DOO compounds, with aminopolycarboxylic acid derivatives being particularly preferred.

  Preferable examples of the aminopolycarboxylic acid derivatives include the compounds listed in the appendix of “EDTA (-Complexane Chemistry)” (Nanedo, 1977), and some of the carboxyl groups of these compounds are sodium or potassium. Alkali metal salts and ammonium salts such as may be substituted. Particularly preferred aminocarboxylic acid derivatives include iminodiacetic acid, N-methyliminodiacetic acid, N- (2-aminoethyl) iminodiacetic acid, N- (carbamoylmethyl) iminodiacetic acid, nitrilotriacetic acid, ethylenediamine-N, N '-Diacetic acid, ethylenediamine-N, N'-di-α-propionic acid, ethylenediamine-N, N'-di-β-propionic acid, N, N'-ethylene-bis (α-o-hydroxyphenyl) glycine N, N′-di (2-hydroxybenzyl) ethylenediamine-N, N′-diacetic acid, ethylenediamine-N, N′-diacetic acid-N, N′-diacethydroxamic acid, N-hydroxyethylethylenediamine-N , N ′, N′-triacetic acid, ethylenediamine-N, N, N ′, N′-tetraacetic acid, 1,2-propylenediamine-N, N, N ′ N′-tetraacetic acid, d, l-2,3-diaminobutane-N, N, N ′, N′-tetraacetic acid, meso-2,3-diaminobutane-N, N, N ′, N′-four Acetic acid, 1-phenylethylenediamine-N, N, N ′, N′-tetraacetic acid, d, l-1,2-diphenylethylenediamine-N, N, N ′, N′-tetraacetic acid, 1,4-diaminobutane -N, N, N ', N'-tetraacetic acid, trans-cyclobutane-1,2-diamine-N, N, N', N'-tetraacetic acid, trans-cyclopentane-1,2-diamine-N, N, N ′, N′-tetraacetic acid, trans-cyclohexane-1,2-diamine-N, N, N ′, N′-tetraacetic acid, cis-cyclohexane-1,2-diamine-N, N, N ′ , N′-tetraacetic acid, cyclohexane-1,3-diamine-N, N, N ′, N′-four Acid, cyclohexane-1,4-diamine-N, N, N ′, N′-tetraacetic acid, o-phenylenediamine-N, N, N ′, N′-tetraacetic acid, cis-1,4-diaminobutene- N, N, N ′, N′-tetraacetic acid, trans-1,4-diaminobutene-N, N, N ′, N′-tetraacetic acid, α, α′-diamino-o-xylene-N, N, N ′, N′-tetraacetic acid, 2-hydroxy-1,3-propanediamine-N, N, N ′, N′-tetraacetic acid, 2,2′-oxy-bis (ethyliminodiacetic acid), 2,2 '-Ethylenedioxy-bis (ethyliminodiacetic acid), ethylenediamine-N, N'-diacetic acid-N, N'-di-α-propionic acid, ethylenediamine-N, N'-diacetic acid-N, N'- Di-β-propionic acid, ethylenediamine-N, N, N ′, N′-tetrapropionic acid Diethylenetriamine-N, N, N ′, N ″, N ″ -pentaacetic acid, triethylenetetramine-N, N, N ′, N ″, N ′ ″, N ′ ″-hexaacetic acid, 1, 2,3-triaminopropane-N, N, N ′, N ″, N ′ ″, N ′ ″-hexaacetic acid, and some of the carboxyl groups of these compounds include sodium and potassium. Substituted ones such as alkali metal salts and ammonium salts can also be mentioned.

  The addition amount of the chelating agent is preferably 0.01% by mass to 0.4% by mass, more preferably 0.02% by mass to 0.3% by mass with respect to the total amount of monomers. It is especially preferable that it is 03 mass%-0.15 mass%. When the amount of the chelating agent is less than 0.01% by mass, capture of metal ions mixed in the production process of the polymer latex becomes insufficient, stability against aggregation of the latex is lowered, and applicability is deteriorated. On the other hand, if it exceeds 0.4%, the viscosity of the latex increases and the coatability is lowered.

  A chain transfer agent is preferably used for the synthesis of the polymer latex used in the present invention. The gelation rate can be controlled by the amount of chain transfer agent added. As the chain transfer agent, those described in Polymer Handbook, 3rd edition, (Wiley-Interscience, 1989) are preferable. Sulfur compounds are more preferred because they have high chain transfer ability and can be used in small amounts. Hydrophobic mercaptan-based chain transfer agents such as tert-dodecyl mercaptan and n-dodecyl mercaptan are particularly preferred.

  The amount of the chain transfer agent is preferably 0.2% by mass to 2.0% by mass, more preferably 0.3% by mass to 1.8% by mass, and 0.4% by mass to 1.6% by mass with respect to the total amount of monomers. Mass% is particularly preferred.

  In emulsion polymerization, in addition to the above compounds, electrolytes, stabilizers, thickeners, antifoaming agents, antioxidants, vulcanizing agents, antifreezing agents, gelling agents, vulcanization accelerators, etc. are described in synthetic rubber handbooks, etc. These additives may be used.

<Specific examples of polymer latex>
Specific examples of the preferred polymer latex include the following. Below, it represents using a raw material monomer, and in exemplary compound (P-1)-(P-29), x, y, z, and z 'in a chemical formula show mass ratio of a polymer composition, x, y, The sum of z and z ′ is 100%. In the exemplified compounds (P-31) to (P-42), the numerical value in parentheses is% by mass, and the molecular weight is a number average molecular weight. When a polyfunctional monomer was used, the concept of molecular weight was not applicable because a crosslinked structure was formed, so it was described as crosslinkable and the molecular weight description was omitted. Tg represents the glass transition temperature of the dry film obtained from the polymer.

  Examples of commercially available latexes of styrene-butadiene copolymers that are preferably used in the present invention include LACSTAR-3307B and 7132C (manufactured by Dainippon Ink & Chemicals, Inc.), Nipol Lx416 (manufactured by Nippon Zeon Co., Ltd.), and the like. Is mentioned.

  These polymer latexes may be used alone or in combination of two or more as required.

  In the polymer latex used in the present invention, an aqueous solvent can be used as a solvent in the coating solution, but a water-miscible organic solvent may be used in combination. Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethyl acetate and dimethylformamide. The amount of these organic solvents added is preferably 50% or less, more preferably 30% or less of the solvent.

  The polymer latex used in the present invention preferably has a polymer concentration of 10% by mass to 70% by mass, more preferably 20% by mass to 60% by mass, particularly 30% by mass to 55% by mass with respect to the latex liquid. Preferably there is.

  The polymer latex in the present invention preferably has an equilibrium water content of 2% by mass or less at 25 ° C. and 60% RH. More preferably, the equilibrium water content is 0.01% by mass or more and 1.5% by mass or less, and further preferably 0.02% by mass or more and 1.0% by mass or less.

  The average particle size of the latex particles in the present invention is in the range of 1 nm to 50000 nm, preferably in the range of 5 nm to 1000 nm, more preferably in the range of 10 nm to 500 nm, still more preferably in the range of 50 nm to 200 nm. The particle size distribution is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution. Mixing two or more types having a monodispersed particle size distribution is also a preferable method for controlling the physical properties of the coating solution.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose may be added to the non-photosensitive intermediate layer in the invention. The amount of these hydrophilic polymers added is preferably 50% by mass or less, more preferably 20% by mass or less, based on the total binder of the non-photosensitive intermediate layer A.

Total binder coating amount of the non-photosensitive intermediate layer in the invention is preferably ^{0.5g / m 2 ~3.0g / m 2} , more preferably in the range of 1.0g ^{/ m 2} ~2.0g ^/ m 2 is there.

2) Outermost layer The non-photosensitive layer constituting the outermost layer on the surface having the image forming layer in the invention will be described.
Usually, the role of the outermost layer is to form the outermost surface of the image forming surface of the photothermographic material, so that the transportability of the photothermographic material is improved and the surface is protected. It is to prevent image damage. Therefore, it is more preferable that additives such as a matting agent, a slipping agent, and a surfactant be added to the outermost layer in addition to the binder.

  The outermost binder in the present invention preferably contains 50% by mass or more of a hydrophilic polymer. A more preferable content of the hydrophilic polymer is 60% by mass or more.

The hydrophilic polymer in the present invention is preferably a hydrophilic polymer derived from animal protein. The hydrophilic polymer derived from animal protein refers to a water-soluble polymer that is naturally or chemically modified, such as glue, casein, gelatin, and egg white. Gelatin is preferred, and acid-treated gelatin and alkali-treated gelatin (such as lime treatment) are available depending on the synthesis method, and both can be preferably used. It is preferable to use gelatin having a molecular weight of 10,000 to 1,000,000. In addition, modified gelatin modified by utilizing the amino group or carboxyl group of gelatin can be used (for example, phthalated gelatin). As gelatin, inert gelatin (for example, Nitta gelatin 750), phthalated gelatin (for example, Nitta gelatin 801), and the like can be used.
The gelatin aqueous solution becomes sol when heated to a temperature of 30 ° C. or higher, and gels and loses fluidity when lowered to a temperature lower than 30 ° C. Since such a sol-gel change occurs reversibly with temperature, the gelatin aqueous solution which is a coating solution has a set property of losing fluidity when cooled to a temperature lower than 30 ° C.

  Moreover, the following hydrophilic polymer and hydrophobic polymer which are not derived from animal protein can be used together with the hydrophilic polymer derived from animal protein.

The hydrophilic polymer not derived from animal protein in the present invention is a natural polymer (polysaccharide, microbial, animal) other than animal protein such as gelatin, semi-synthetic polymer (cellulose, starch, alginic acid). ) And synthetic polymers (vinyl-based, etc.), which are synthetic polymers such as polyvinyl alcohol described below, and natural or semi-synthetic polymers made from plant-derived cellulose or the like. Polyvinyl alcohols and acrylic acid-vinyl alcohol copolymer polymers are preferable.
A hydrophilic polymer not derived from animal protein does not have setability, but when used together with a gelling agent, it has setability and good coating performance.

  As the hydrophobic polymer, a polymer dispersible in an aqueous solvent is preferable. A particularly preferred hydrophobic polymer is a polymer latex containing a fluorine atom described below.

<< Description of Polymer Latex Containing Fluorine Atoms >>
The polymer latex containing a fluorine atom in the present invention has at least the following monomer component (M2).
(M2) A monomer having an unsaturated bond capable of radical polymerization and containing a fluorine atom.
Preferably, it is a polymer containing 5% by mass or more and 100% by mass or less of the monomer component (M2), more preferably a polymer containing 20% by mass or more and 100% by mass or less.
More preferably, the fluoropolymer further contains a monomer component represented by the following (M1).
(M1) A monomer having a group capable of forming a salt or a polyalkylene oxide group and having an unsaturated bond capable of radical polymerization.
Furthermore, it is preferable to have a monomer component (M3) that does not fall under any of the above (M1) and (M2).

The content of the monomer component represented by (M1) in the fluoropolymer is preferably 0.1% by mass to 20% by mass, and more preferably 0.5% by mass to 10% by mass. The content of the monomer component represented by (M3) having an unsaturated bond capable of radical polymerization that does not correspond to any of (M1) and (M2) in the fluoropolymer is 0.5% by mass or more and 95% by mass. %, More preferably 5.0% by mass to 80% by mass.
(M1) :( M2) :( M3) = 0 to 20% by mass: 5 to 100% by mass: 0 to 95% by mass in the fluoropolymer, more preferably (M1) :( M2) :( M3) = 0-10 mass%: 20-100 mass%: 0-80 mass%.

  Examples of the monomer having a salt-forming group in (M1) include an anionic monomer, a cationic monomer, and an amphoteric monomer, and the monomer having a polyalkylene oxide group in (M1) is a nonionic monomer. A monomer is mentioned. More specifically, examples of the anionic monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer. Examples of the cationic monomer include an unsaturated tertiary amine-containing monomer and an unsaturated ammonium. Salt-containing monomers and the like, and as amphoteric monomers, N- (3-sulfopropyl) -N-methacrylyloxyethyl-N, N-dimethylammonium betaine, N- (3-sulfopropyl) -N-methacryl Rylamidopropyl-N, N-dimethylammonium betaine, 1- (3-sulfopropyl) -2-vinylpyridinium betaine, nonionic monomer includes unsaturated polyoxyethylene oxide monomer, unsaturated polyoxypropylene oxide monomer Etc.

Specifically, among the anionic monomers, unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, or their anhydrides and their mono There are vinyl ethers having a carboxyl group such as alkyl esters, carboxyethyl vinyl ether, and carboxypropyl vinyl ether.
Examples of unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acyclic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. And its salts. In addition, there are sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and salts thereof.
Unsaturated phosphoric acid monomers include vinyl phosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate Diphenyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.

  Examples of the cationic monomer include unsaturated tertiary amine-containing monomers and unsaturated ammonium salt-containing monomers. Specific examples include vinylpyridine, 2-methyl-5-vinylpyridine, 2-ethyl-5- Monovinylpyridines such as vinylpyridine; styrenes having a dialkylamino group such as N, N-dimethylaminostyrene and N, N-dimethylaminomethylstyrene; N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminoethyl Acrylate, N, N-diethylaminoethyl methacrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminopropyl methacrylate, N, N-dimethylaminopropyl acrylate, N, N-diethylaminopropyl methacrylate, N, N-diethylaminopro Esters having a dialkylamino group of acrylic acid or methacrylic acid such as acrylate; vinyl ethers having a dialkylamino group such as 2-dimethylaminoethyl vinyl ether; N- (N ′, N′-dimethylaminoethyl) methacrylamide; N- (N ′, N′-Cymethylaminoethyl) acrylamide, N- (N ′, N′-diethylaminoethyl) methacrylamide, N- (N ′, N′-diethylaminoethyl) acrylamide, N- (N ′ , N'-dimethylaminopropyl) methacrylamide, N- (N ', N'-dimethylaminopropyl) acrylamide, N- (N', N'-diethylaminopropyl) methacrylamide, N- (N ', N'- Dialkylamino group such as diethylaminopropyl) acrylamide Acrylamide or methacrylamides, or alkyl halides thereof (alkyl group having 1 to 18 carbon atoms, halogen as chlorine, bromine, iodine), benzyl halides such as benzyl chloride or benzyl bromide, alkyl or aryl sulfonic acid, For example, quaternary quaternizing agents such as methanesulfonic acid, benzenesulfonic acid or toluenesulfonic acid alkyl ester (alkyl group having 1 to 18 carbon atoms) and dialkyl sulfate (alkyl group having 1 to 4 carbon atoms) can be used. Graded ones are listed.

  Nonionic monomers include esters of unsaturated carboxylic acid monomers and polyoxyalkylene glycols or polyoxyalkylene oxide adducts of lower alcohols, or glycidyl ethers of unsaturated carboxylic acid monomers or polyoxyalkylenes. There are reactants of polyoxyalkylene oxide adducts of glycols or lower alcohols, and for example, those represented by the following formula can be used.

In the present invention, examples of the monomer (M2) include known compounds such as (meth) acrylates having a polyfluoroalkyl group and a perfluoroalkyl group, vinyl esters, vinyl ethers, malates, fumarate, and α-olefins. . More preferable fluorine-containing monomers include those having a polyfluoroalkyl group or perfluoroalkyl group having 4 or more carbon atoms.
Examples of these compounds are listed below, but the present invention is not limited thereto.

There are also macromonomers of the monomers shown above. The production of this macromonomer is easily synthesized by formulations known in the art.
For example, the above monomers are radically polymerized with thioglycolic acid and 2-mercaptoethanol in the presence of an initiator, and the resulting reaction product is reacted with glycidyl (meth) acrylate and isocyanate ethyl (meth) acrylate. It can be obtained by introducing a radically polymerizable unsaturated bond at one end.
The number average molecular weight of the macromonomer is desirably 10,000 or less, and preferably the number average molecular weight is 5,000 or less.

  In addition, as the monomer (M3) having an unsaturated bond capable of radical polymerization other than (M1) and (M2), known compounds such as (meth) acrylate, vinyl ester, vinyl ether, malate, fumarate, and α-olefin may be used. Can be mentioned.

  Specific examples of these compounds include vinyl acetates such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl laurate, vinyl versatate, vinyl cyclohexanecarboxylate, methyl vinyl ether, ethyl vinyl ether. , N-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, lauryl vinyl ether, and other vinyl ethers Monoolefins such as ethylene and propylene, dimethyl maleate, diethyl maleate, male Malates such as dioctyl acid, diolefins such as butadiene and isoprene, allyls such as allyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, (meth) (Meth) acrylates such as isobutyl acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, styrene, vinyltoluene, etc. In addition to the styrenic monomers and acrylonitrile monomers, there are macromonomers of the monomers shown above.

The production of this macromonomer is easily synthesized by formulations known in the art.
For example, radical polymerization of the above monomers with thioglycolic acid and 2-mercaptoethanol and the like in the presence of an initiator, and the resulting reaction product is reacted with glycidyl (meth) acrylate, isocyanate ethyl (meth) acrylate, and the like, It can be obtained by introducing a radically polymerizable unsaturated bond at one end.
As a monomer, it can select from 1 type, or 2 or more types of these monomers shown above.

  The monomer (M2) preferably contains a repeating unit A derived from an acrylate or methacrylate monomer containing a fluorine atom.

More specifically, the repeating unit A is derived from a fluoro (meth) acrylate or a mixture of fluoro (meth) acrylates represented by the following general formula (P).
Formula (P) (Rf) pL-OCOC (R) = CH ₂
In the above formula, the substituent Rf is a monovalent aliphatic organic group containing 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and containing a fluorine atom. The skeleton chain of Rf may be a straight chain, a branched chain, or a cyclic chain, and may contain a catenary divalent oxygen atom or a trivalent nitrogen atom bonded only to a carbon atom. Rf is preferably completely fluorinated, but a hydrogen atom or a chlorine atom bonded to carbon may be present as a substituent on the skeleton chain of Rf. Rf preferably contains at least a perfluoromethyl end group. p is preferably 1 or 2.

  The linking group L is a linking group containing 1 to 12 carbon atoms, and is optionally substituted and / or interrupted by a substituted or unsubstituted form of a heteroatom such as O, P, S, and N. It is. R is H or methyl. The fluoro (meth) acrylate monomer preferably contains 30% by mass or more of fluorine.

Examples of the fluoro (meth) acrylate useful in the present invention include the following.
_{CF 3 (CF 2) x (} CH 2) yOCOC (R) = CH 2
In the above formula, x is 0 to 20, preferably 2 to 10, y is 1 to 10, and R is H or methyl.
_{HCF 2 (CF 2) x (} CH 2) yOCOC (R) = CH 2
In the above formula, x is 0 to 20, preferably 2 to 10, y is 1 to 10, and R is H or methyl.

  In the above formula, x is an integer of 0 to 20, preferably 2 to 10, y is an integer of 1 to 10, z is an integer of 1 to 4, and R 'Is alkyl or arylalkyl, and R ″ is H or methyl.

  In the above formula, x is an integer of 1 to 7, y is an integer of 1 to 10, and R is H or methyl.

_{CF 3 (CF 2 CF 2 O} ) x (CF 2 O) y (CH 2) zOCOCR = CH 2
In the above formula, x + y is an integer of 1 to 20, z is an integer of 1 to 10, and R is H or methyl.

  The copolymer in the present invention may be any of a random copolymer, a graft copolymer, or a block copolymer. The molecular weight of the copolymer is preferably in the range of about 5000 to about 10,000,000 in terms of mass average molecular weight. More preferably, it is the range of 5000-1,000,000.

  Specific examples of the polymer composition of the polymer latex containing a fluorine atom in the present invention are shown below, but are not limited thereto.

A synthesis example is described from the above specific examples.
-Synthesis of FL-1-
A reactor equipped with a stirrer, reflux condenser, dropping funnel, thermometer, nitrogen inlet tube, 64 parts of isopropyl alcohol, 4 parts of ion-exchanged water, 14.8 parts of methyl methacrylate, 1H, 1H, 2H, 2H-heptadecafluoro 41.2 parts of decyl methacrylate and 8 parts of 2-acrylamido-2-methylpropanesulfonic acid are charged, and dissolved oxygen is removed by flowing nitrogen gas.
Meanwhile, 36 parts of isopropyl alcohol, 36 parts of methyl methacrylate and 0.07 part of azobisisobutyronitrile from which dissolved oxygen has been removed are charged into a dropping funnel. The reactor is heated to 83 ± 3 ° C., 0.13 part of azobisisobutylnitrile dissolved in 2 parts of methyl ethyl ketone is added, and the monomer is dropped from the dropping funnel in accordance with the consumption rate of methyl methacrylate. After the addition of the monomer was completed, 0.2 parts of azobisisobutyronitrile dissolved in 3 parts of methyl ethyl ketone was added, and the reaction was continued for another 2 hours. Again, 0.1 part of azobisisobutyronitrile was added to 2 parts of methyl ethyl ketone. The dissolved product was added and the reaction was continued again for 6 hours to obtain a homogeneous copolymer.
Next, the copolymer was neutralized by adding 15.5 parts of a 10% by weight aqueous sodium hydroxide solution, and subsequently 300 parts of ion-exchanged water was added. Then, methyl ethyl ketone was removed under reduced pressure, and the polymer of the present invention was removed. An aqueous dispersion FL-1 was obtained.

-Synthesis of FL-7-
450 parts of methyl ethyl ketone from which dissolved oxygen was removed and 5 parts of acrylic acid were placed in a 1 L stainless steel autoclave equipped with a stirrer, and the inside gas was replaced with nitrogen. Next, after substitution with tetrafluoroethylene, a mixed monomer of propylene / tetrafluoroethylene = 60/40 mol% is injected to bring the internal pressure to 4.9 MPa.
After the stirring was started, the temperature was raised, and when the internal temperature reached 70 ° C., a mixture of 0.9 part of benzoyl peroxide dissolved in 10 parts of methyl ethyl ketone was injected, and the mixed monomer having the above composition so that the internal pressure became 13.7 MPa 145 parts of acrylic acid is injected in about 8 hours. The reaction is maintained at an internal temperature of 75 ° C., each monomer is replenished according to the consumption rate of propylene and tetrafluoroethylene, and the internal pressure is maintained in the range of 12.7 MPa to 13.7 MPa. Further, 3 hours and 6 hours later, 0.9 part of benzoyl peroxide dissolved in 10 parts of methyl ethyl ketone was added, and after reacting for 12 hours, the autoclave was cooled to evaporate volatile substances. The consumption amount of the mixed monomer during this period was about 150 parts.
As a result of obtaining the composition of the obtained copolymer by NMR, it was tetrafluoroethylene / propylene / acrylic acid = 25/25/50 mass%.
Next, 100 parts of a copolymer (solid content: 38.5 parts) was taken, 27 parts of triethylamine and 160 parts of ion-exchanged water were added, methyl ethyl ketone was removed under reduced pressure, and an aqueous dispersion FL- 7 was obtained.

  The method for synthesizing the polymer latex in the present invention is not limited to the above two examples, and a known method can be applied. Details are described in JP-A-2-147601, JP-A-5-17538, JP-A-8-208936, and JP-A-11-288061.

The solvent of the outermost coating solution may be an organic solvent or an aqueous solvent, but an aqueous solvent is preferred. In the case of an aqueous solvent, the copolymer in the present invention is a polymer latex and can be easily added to a coating solution.
The average particle diameter and the particle system distribution of the dispersed particles of the polymer latex are the same as those described in “Latex polymer description” below.
The aqueous solvent is water or water mixed with 70% by mass or less of a water miscible organic solvent. Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol, cellosolvs such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethyl acetate and dimethylformamide.

  The copolymer in the present invention may be used in combination with a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose or a latex polymer described later as a binder.

When the polymer latex is used, the content of the polymer is preferably 20% by mass or more and 100% by mass or less, and more preferably 30% by mass or more and 100% by mass or less with respect to the entire binder.
The coating weight of the polymer, is preferably 0.05 g / ^{m 2} or more 2.0 g / ^{m 2} or less, more preferably 0.1 g / ^{m 2} or more 1.0 g / ^{m 2} or less.

3) Auxiliary additives The intermediate layer and the outermost layer in the present invention can contain various auxiliary additives in addition to the binder depending on the purpose.

<Gelling agent>
The gelling agent in the present invention is a substance that causes gelation of a solution when added to a hydrophilic polymer aqueous solution or a hydrophobic polymer latex aqueous solution that is not derived from animal protein in the present invention and is cooled, or a gelation promoting substance. It is a substance that causes gelation when used in combination. By causing gelation, the fluidity is significantly reduced.

  Specific examples of the gelling agent include the following water-soluble polysaccharides. That is, agar, κ-carrageenan, ι-carrageenan, alginic acid, alginate, agarose, furceleran, gellan gum, glucono delta lactone, azotobacter vineland gum, xanthan gum, pectin, guar gum, locust bean gum, tara gum, cassia gum, gluco It is at least one selected from mannan, gum tragacanth, karaya gum, pullulan, gum arabic, arabinogalactan, dextran, carboxymethylcellulose sodium salt, methylcellulose, silium sheet gum, starch, chitin, chitosan and curdlan.

  Examples of the substance that gels by cooling after being heated and dissolved include substances such as agar, carrageenan, and julan gum.

  Among these gelling agents, κ-carrageenan (eg: K-9F, manufactured by Taisho Co., Ltd .: Nitta Gelatin Co., Ltd .: K-15: K-21-24, I— 3), iota-carrageenan and agar are mentioned, and κ-carrageenan is particularly preferred.

  The gelling agent is 0.01% by mass or more and 10.0% by mass or less, preferably 0.02% by mass or more and 5.0% by mass or less, more preferably 0.05% by mass or more and 2.% by mass or more with respect to the binder polymer. It is preferable to use 0% by mass or less.

<Geling accelerator>
The gelling agent is preferably used together with a gelling accelerator. The gelation accelerator in the present invention is a compound that promotes gelation by contact with the gelling agent, and its function is exhibited by a specific combination with the gelling agent. In the present invention, the following combinations can be used as the combination of the gelling agent and the gelation accelerator.

  ・ Alkaline metal ions such as potassium, or alkaline earth metal ions such as calcium and magnesium as gelling accelerators, and carrageenan, alginate, gellan gum, azotobacter vineland gum, pectin, carboxymethylcellulose sodium salt as gelling agents Combination of etc.

  ・ A combination of boric acid and other boron compounds as gelling accelerators and guar gum, locust bean gum, tara gum, cassia gum, etc. as gelling agents.

  -A combination of acid or alkali as a gelling accelerator and alginate, glucomannan, pectin, chitin, chitosan, curdlan, etc. as a gelling agent.

  A water-soluble polysaccharide that reacts with a gelling agent to form a gel is used as a gelation accelerator. Specifically, a combination using xanthan gum as the gelling agent, using cassia gum as the gelling agent, using carrageenan as the gelling agent, and using locust bean gum as the gelling agent can be exemplified.

The following a) -g) can be illustrated as a specific example of the combination of these gelling agents and gelation accelerators.
a) Combination of kappa-carrageenan and potassium b) Combination of iota-carrageenan and calcium c) Combination of ro-methoxyl pectin and calcium d) Combination of sodium alginate and calcium e) Combination of gellan gum and calcium f) Combination of gellan gum and acid g) Combination of Locust Bingham and Xanthan Gum A plurality of such combinations may be used simultaneously.

  These gelation accelerators may be added to the same layer to which the gelling agent is added, but it is preferable to add them to different layers and act. More preferably, it is added to a layer not directly adjacent to the layer to which the gelling agent is added. That is, it is more preferable to have a layer containing neither a gelling agent nor a gelling accelerator between a layer containing a gelling agent and a layer containing a gelling accelerator.

  The gelling accelerator is used in an amount of 0.1 to 200% by mass, preferably 1.0 to 100% by mass, based on the gelling agent.

  In addition, additives can be appropriately added to the hydrophilic polymer 2-containing layer. Examples of such additives include surfactants, pH adjusters, preservatives, antifungal agents, dyes, pigments, color tone adjusters, and the like.

<Filming aid>
In order to control the minimum film forming temperature of the aqueous dispersion of the hydrophobic polymer, a film forming aid may be added. A film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of a polymer latex. For example, “Synthetic latex chemistry (written by Soichi Muroi, published by Polymer Publishing Co., Ltd.) (1970)) Preferred film-forming aids are the following compounds, but the compounds that can be used in the present invention are not limited to the following specific examples.
Z-1: benzyl alcohol Z-2: 2,2,2,4-trimethylpentanediol-1,3-monoisobutyrate Z-3: 2-dimethylaminoethanol Z-4: diethylene glycol

<Crosslinking agent>
In the present invention, it is preferable to incorporate a crosslinking agent in any layer on the image forming layer surface. More preferably, it is a case where it is added to the hydrophilic polymer 1-containing layer or the hydrophilic polymer 2-containing layer such as the non-photosensitive intermediate layer B. By adding a crosslinking agent, the hydrophobicity and water resistance of the non-photosensitive intermediate layer are increased, and an excellent photothermographic material is obtained.

  As a crosslinking agent, what is necessary is just to contain two or more groups which react with an amino group or a carboxyl group in a molecule | numerator, and it does not specifically limit about the kind of crosslinking agent. Examples of cross-linking agents include T.W. H. "THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION" by James (published by Macmillan Publishing Co., Inc., 1977), pages 77-87, and inorganic compound cross-linking agents (for example, chromium alum) Any of the compound crosslinking agents is preferred, but organic compound crosslinking agents are more preferred.

The crosslinking agent for the hydrophobic polymer-containing layer such as the non-photosensitive intermediate layer A of the present invention may contain a plurality of groups that react with carboxyl groups in the molecule, and the type of the crosslinking agent is not particularly limited. .
Preferred examples of the organic compound crosslinking agent include carboxylic acid derivatives, carbamic acid derivatives, sulfonic acid ester compounds, sulfonyl compounds, epoxy compounds, aziridine compounds, isocyanate compounds, carbodiimide compounds, and oxazoline compounds. More preferred are epoxy compounds, isocyanate compounds, carbodiimide compounds and oxazoline compounds. These crosslinking agents may be used alone or in combination of two or more.

<Thickener>
It is preferable to add a thickener to the coating solution for forming the non-photosensitive intermediate layer A. It is preferable to add a thickener since a hydrophobic layer having a uniform thickness can be formed. As the thickener, for example, an alkali metal salt of polyvinyl alcohol, hydroxyethyl cellulose, or carboxymethyl cellulose is used, but a thixotropic one is preferable in consideration of ease of handling. Therefore, hydroxyethyl cellulose, sodium hydroxymethylcarboxylate, Carboxymethyl-hydroxyethylcellulose is used.
The viscosity of the non-photosensitive intermediate layer A coating solution to which a thickener is added is preferably 1 mPa · s or more and 200 mPa · s or less at 40 ° C., and preferably 10 mPa · s or more and 100 mPa · s or less. More preferably, it is 15 mPa · s or more and 60 mPa · s or less.

<Polymer latex>
The polymer latex used for the outermost layer binder in the present invention will be described. Preferably, the content of the polymer latex is 50% by mass or more and 100% by mass or less, and more preferably 50% by mass or more and 75% by mass or less.

A polymer latex having an equilibrium water content of 5% by mass or less at 25 ° C. and 60% RH is preferred. “Equilibrium moisture content at 25 ° C. and 60% RH” means the following equation using the mass W1 of the polymer in the humidity-controlled equilibrium under the atmosphere of 25 ° C. and 60% RH, Can be expressed as:
Equilibrium moisture content at 25 ° C. and 60% RH = {(W1−W0) / W0} × 100 (mass%)

  The equilibrium moisture content in the present invention is preferably 2% by mass or less, more preferably 0.01% by mass or more and 1.5% by mass or less, and further preferably 0.02% by mass or more and 1% by mass or less.

  The glass transition temperature of the polymer latex in the present invention is preferably 0 ° C. or higher and 80 ° C. or lower, more preferably 10 ° C. or higher and 70 ° C. or lower, and further preferably 15 ° C. or higher and 60 ° C. or lower.

Specific examples of the polymer latex that can be used in the present invention include polyacrylate, polyurethane, polymethacrylate, or a latex of a copolymer containing these.
Two or more polymer latexes that can be used in the present invention may be used in combination as required. Further, a glass transition temperature of 20 ° C. or higher and a glass transition temperature of less than 20 ° C. may be used in combination. When two or more types of polymers having different Tg are blended, the mass average Tg is preferably within the above range.

In this invention, it is preferable to apply | coat and dry using the coating liquid whose 30 mass% or more of a solvent is water, and to form a hydrophobic polymer content layer.
A preferred embodiment of the polymer latex in the present invention is one prepared so as to have an ionic conductivity of 2.5 mS / cm or less. As such a preparation method, a method of purifying using a separation functional membrane after polymer synthesis. Is mentioned.

  The coating solvent is preferably water or a mixture of 70% by mass or less of a water-miscible organic solvent in water. Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, cellosolvs such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, ethyl acetate, and dimethylformamide.

  In the present invention, the average particle size of the polymer latex is preferably 1 nm or more and 50000 nm or less, more preferably 10 nm or more and 500 nm or less, and further preferably 50 nm or more and 200 nm or less. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution. Mixing two or more types having a monodispersed particle size distribution is also a preferable method for controlling the physical properties of the coating solution.

  Polymers include acrylic polymers, poly (esters), rubbers (eg SBR resins), poly (urethanes), poly (vinyl chloride) s, poly (vinyl acetate) s, poly (vinylidene chloride) s, and Hydrophobic polymers such as poly (olefin) s can be preferably used. The polymer may be a linear polymer, a branched polymer, a crosslinked polymer, a so-called homopolymer obtained by polymerizing a single monomer, or a copolymer obtained by polymerizing two or more types of monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of these polymers is 5,000 to 1,000,000, preferably 10,000 to 200,000 in terms of number average molecular weight. When the molecular weight is too small, the mechanical strength of the image forming layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable. A crosslinkable polymer latex is particularly preferably used.

<Specific examples of latex>
Specific examples of the preferred polymer latex include the following. Below, it represents using a raw material monomer, the numerical value in a parenthesis is the mass%, and molecular weight is a number average molecular weight. When a polyfunctional monomer was used, the concept of molecular weight was not applicable because a crosslinked structure was formed, so it was described as crosslinkable and the molecular weight description was omitted. Tg represents the glass transition temperature.

NP-1; -MMA (70) -EA (27) -MAA (3)-latex (molecular weight 37000, Tg 61 ° C.)
NP-2; latex of MMA (70) -2EHA (20) -St (5) -AA (5)-(molecular weight 40000, Tg 59 ° C.)
NP-3; Latex of -St (55) -Bu (42) -MAA (3)-(crosslinkability, Tg 5 ° C.)
-NP-4; -St (68) -Bu (29) -AA (3)-latex (crosslinkable, Tg 17 ° C)
NP-5; Latex of -St (71) -Bu (26) -AA (3)-(crosslinkability, Tg 24 ° C.)
NP-6; Latex (crosslinkable) of -St (70) -Bu (27) -IA (3)-
NP-7; latex of -St (75) -Bu (24) -AA (1)-(crosslinkability, Tg 29 ° C.)
NP-8; Latex (crosslinkable) of -St (60) -Bu (35) -DVB (3) -MAA (2)-
NP-9; Latex (crosslinkability) of -St (70) -Bu (25) -DVB (2) -AA (3)-
NP-10; latex of -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-(molecular weight 80,000)
NP-11; latex of -VDC (85) -MMA (5) -EA (5) -MAA (5)-(molecular weight 67000)
NP-12; -Et (90) -MAA (10)-latex (molecular weight 12000)
NP-13; -St (70) -2EHA (27) -AA (3) latex (molecular weight 130,000, Tg 43 ° C.)
NP-14; latex of MMA (63) -EA (35) -AA (2) (molecular weight 33,000, Tg 47 ° C.)
-NP-15; -St (70.5) -Bu (26.5) -AA (3) -latex (crosslinkability, Tg 23 ° C.)
NP-16; latex of -St (69.5) -Bu (27.5) -AA (3)-(crosslinkability, Tg 20.5 ° C)
-NP-17; latex of -St (61.3) -isoprene (35.5) -AA (3)-(crosslinkability, Tg17 ° C)
NP-18; latex of -St (67) -isoprene (28) -Bu (2) -AA (3)-(crosslinkability, Tg 27 ° C.)

  The abbreviations for the above structures represent the following monomers. MMA; Methyl methacrylate, EA; Ethyl acrylate, MAA; Methacrylic acid, 2EHA; 2-Ethylhexyl acrylate, St; Styrene, Bu; Butadiene, AA; Acrylic acid, DVB; Divinylbenzene, VC; Vinyl chloride, AN; Acrylonitrile, VDC Vinylidene chloride, Et; ethylene, IA; itaconic acid.

  The polymer latex described above is also commercially available, and the following polymers can be used. Examples of the acrylic polymer include Sebian A-4635, 4718, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.), etc. Examples of poly (esters) include poly (urethane) such as FINETEX ES650, 611, 675, 850 (above, manufactured by Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (above, manufactured by Eastman Chemical). Examples of rubbers include HYDRAN AP10, 20, 30, 40 (manufactured by Dainippon Ink Chemical Co., Ltd.), and examples of rubbers include LACSTAR 7310K, 3307B, 4700H, 7132C (above, Dainippon Ink Chemical Co., Ltd.). (Made by Co., Ltd.), Nipol Lx416, 410, 438C, 2507 (above, Nippon Zeo) As examples of poly (vinyl chloride) such as G351 and G576 (above, manufactured by Nippon Zeon Co., Ltd.), examples of poly (vinylidene chloride) such as L502, L513 (above Examples of poly (olefin) s such as Asahi Kasei Kogyo Co., Ltd. include Chemipearl S120 and SA100 (above Mitsui Petrochemical Co., Ltd.).

  These polymer latexes may be used alone or in combination of two or more as required.

  The polymer latex used in the hydrophobic polymer layer of the present invention is particularly preferably an acrylic polymer copolymer, polyester, polyurethane or the like. Moreover, it is preferable that the polymer latex used for the hydrophobic polymer layer of this invention contains 1-6 mass% of acrylic acid or methacrylic acid, More preferably, it contains 2-5 mass%. The polymer latex used in the hydrophobic polymer layer of the present invention preferably contains acrylic acid.

The application amount of the hydrophobic polymer (per 1 m ^{2 of} support) is preferably 0.1 g / m ² or more and 10 g / m ² or less, more preferably 0.3 g / m ² or more and 5 g / m ² or less.
The concentration in the coating solution is preferably adjusted so that the viscosity becomes a value suitable for simultaneous multilayer coating when added, but is not particularly limited. In general, the concentration in the liquid is 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less, and particularly preferably 15% by mass or more and 30% by mass or less.

<Matting agent>
In the present invention, it is preferable to add a matting agent for improving transportability, and the matting agent is described in paragraph Nos. 0126 to 0127 of JP-A No. 11-65021. The matting agent is preferably 1 mg / m ² or more and 400 mg / m ² or less, more preferably 5 mg / m ² or more and 300 mg / m ² or less when expressed in terms of the coating amount per 1 m ² of the photosensitive material.
In the present invention, the shape of the matting agent may be either a regular shape or an irregular shape, but is preferably a regular shape, and a spherical shape is preferably used.
The volume weighted average of the equivalent sphere diameters of the matting agent used for the image forming layer surface is preferably from 0.3 μm to 10 μm, and more preferably from 0.5 μm to 7 μm. The variation coefficient of the size distribution of the matting agent is preferably 5% or more and 80% or less, and more preferably 20% or more and 80% or less. Here, the coefficient of variation is a value represented by (standard deviation of particle size) / (average value of particle size) × 100. Further, two or more kinds of matting agents having different average particle sizes can be used as the matting agent on the image forming layer surface. In that case, the difference in particle size between the matting agent having the largest average particle size and the smallest matting agent is preferably 2 μm or more and 8 μm or less, and more preferably 2 μm or more and 6 μm or less.
The volume weighted average of the equivalent sphere diameters of the matting agent used for the back surface is preferably 1 μm or more and 15 μm or less, and more preferably 3 μm or more and 10 μm or less. The variation coefficient of the size distribution of the matting agent is preferably 3% or more and 50% or less, and more preferably 5% or more and 30% or less. Further, two or more types of matting agents having different average particle sizes can be used as the matting agent for the back surface. In this case, the difference in particle size between the matting agent having the largest average particle size and the smallest matting agent is preferably 2 μm or more and 14 μm or less, and more preferably 2 μm or more and 9 μm or less.

  The matting degree of the image forming layer surface may be any as long as no stardust failure occurs, but the Beck smoothness is preferably 30 seconds or more and 2000 seconds or less, particularly preferably 40 seconds or more and 1500 seconds or less. The Beck smoothness can be easily determined by Japanese Industrial Standard (JIS) P8119 “Smoothness test method using Beck tester for paper and paperboard” and TAPPI standard method T479.

  In the present invention, the matte degree of the back layer is preferably a Beck smoothness of 1200 seconds or less and 10 seconds or more, preferably 800 seconds or less and 20 seconds or more, and more preferably 500 seconds or less and 40 seconds or more.

  In the present invention, the matting agent is preferably contained in a layer functioning as the outermost layer or surface protective layer of the photothermographic material or a layer close to the outermost layer.

<Slip agent>
In order to improve handling at the time of manufacture and scratch resistance at the time of heat development, it is preferable to use a sliding agent such as liquid paraffin, long chain fatty acid, fatty acid amide, fatty acid ester and the like. Particularly preferred are liquid paraffin from which low-boiling components have been removed and fatty acid esters having a branched structure and having a molecular weight of 1000 or more.

As the slipping agent, compounds described in paragraph No. 0117 of JP-A No. 11-65021, JP-A No. 2000-5137, JP-A No. 2004-219794, JP-A No. 2004-21802, and JP-A No. 2004-334077 are preferable.
The amount of the slip agent used is in the range of 1 mg / m ^{2 to} 200 mg / m ² , preferably 10 mg / m ^{2 to} 150 mg / m ² , more preferably 20 mg / m ^{2 to} 100 mg / m ^2. .

  The layer to which the slip agent is added may be either an image forming layer or a non-image forming layer, but is preferably added to the outermost layer for the purpose of improving transportability and scratch resistance.

<Surfactant>
JP-A No. 11-65021 paragraph No. 0132 for surfactants applicable to the present invention, paragraph No. 0133 for solvents, paragraph No. 0134 for supports, paragraph No. for antistatic or conductive layers In paragraph 0136, the method for obtaining a color image is described in paragraph No. 0136 of the same number, and in Japanese Patent Application Laid-Open No. 11-84573, paragraph numbers 0061 to 0064 and paragraph number 0049 to 0062 of Japanese Patent Application Laid-Open No. 2001-83679 are described.
In the present invention, it is preferable to use a fluorosurfactant. Specific examples of the fluorosurfactant include compounds described in JP-A Nos. 10-197985, 2000-19680, 2000-214554 and the like. Further, a polymeric fluorine-based surfactant described in JP-A-9-281636 is also preferably used. In the photothermographic material of the invention, it is preferable to use a fluorine-based surfactant described in JP-A Nos. 2002-82411, 2003-057780, and 2003-149766. In particular, the fluorosurfactants described in JP-A-2003-057780 and JP-A-2003-149766 are preferable in terms of charge adjustment ability, stability of the coated surface, and smoothness when coating and production is performed with an aqueous coating solution. The fluorosurfactants described in JP-A No. 2003-149766 are most preferable in that they have a high charge adjusting ability and can be used in a small amount.
In the present invention, the fluorosurfactant can be used on either the image forming layer surface or the back surface, and is preferably used on both surfaces. Further, it is particularly preferable to use in combination with a conductive layer containing the above-described metal oxide. In this case, sufficient performance can be obtained even if the amount of the fluorosurfactant used on the surface having the conductive layer is reduced or removed.
The preferred amount of the fluorocarbon surfactant is an image forming layer side, the range to the back surface each ^{0.1mg / m 2 ~100mg / m 2} , more preferably 0.3mg ^{/ m 2} ~30mg ^/ m 2 range, even more preferably from ^{1mg / m 2 ~10mg / m 2} . In particular JP fluorocarbon surfactant described in JP-A No. 2001-264110 is ^effective, and preferably in the range of ^{0.01mg / m 2 ~10mg / m 2} , more in the range of 0.1mg / ^{m 2} ~5mg / m 2 preferable.

(Image forming method)
1) Exposure The photothermographic material of the invention may be subjected to image exposure by any means. Scanning exposure with laser light is preferred.
The laser used is a red to infrared emitting He—Ne laser, a red semiconductor laser, or a blue to green emitting Ar ⁺ , He—Ne, He—Cd laser, or a blue semiconductor laser. Preferred is a red to infrared semiconductor laser, and the peak wavelength of the laser light is 600 nm to 900 nm, preferably 620 nm to 850 nm.
On the other hand, in recent years, in particular, a module in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated and a blue semiconductor laser have been developed, and a laser output device in a short wavelength region has been closed up. The blue semiconductor laser is expected to increase in demand in the future because high-definition image recording is possible, the recording density is increased, and a stable output is obtained with a long lifetime. The peak wavelength of the blue laser light is preferably 300 nm to 500 nm, particularly preferably 400 nm to 500 nm.
It is also preferable that the laser light is oscillated in a vertical multi by a method such as high frequency superposition.

2) Photothermographic development The photothermographic material of the present invention may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. A preferred development temperature is 80 ° C to 250 ° C, preferably 100 ° C to 140 ° C, and more preferably 110 ° C to 130 ° C.
The development time is 3 to 20 seconds, more preferably 4 to 18 seconds, and still more preferably 5 to 15 seconds.

  Either a drum type heater or a plate type heater may be used as the thermal development method, but the plate type heater method is more preferable. The heat development method using the plate type heater method is preferably a method described in JP-A-11-133572, and a visible image is obtained by bringing a photothermographic material having a latent image formed thereon into contact with a heating means in a heat developing unit. In the heat development apparatus, the heating unit includes a plate heater, and a plurality of press rollers are disposed to face each other along one surface of the plate heater, and the press roller is disposed between the press roller and the plate heater. A heat development apparatus characterized in that heat development is performed by passing a photothermographic material. It is preferable to divide the plate heater into two to six stages and lower the temperature at the tip by about 1 ° C. to 10 ° C. For example, there are examples in which four sets of plate heaters that can be independently controlled are used and controlled so as to be 112 ° C., 119 ° C., 121 ° C., and 120 ° C., respectively. Such a method is also described in JP-A-54-30032, which can exclude moisture and organic solvents contained in the photothermographic material out of the system, and rapidly develop the photothermographic material. It is also possible to suppress a change in the shape of the support of the photothermographic material due to the heating.

  In order to reduce the size of the heat developing machine and shorten the heat development time, it is preferable to be able to control the heater more stably. In addition, the exposure of one sheet of photosensitive material is started from the top and the exposure is finished to the back end. It is desirable to start the heat development before the time. Imagers capable of rapid processing preferable for the present invention are described in, for example, Japanese Patent Application No. 2002-289804 and Japanese Patent Application Laid-Open No. 2003-285455. If this imager is used, for example, heat development can be performed in 14 seconds with a three-stage plate heater controlled at 107 ° C.-121 ° C.-121 ° C., and the output time of the first sheet is reduced to about 60 seconds. be able to.

3) System As a medical laser imager provided with an exposure part and a heat development part, Fuji Medical Dry Laser Imager FM-DPL and DRYPIX7000 can be exemplified. Regarding FM-DPL, Fuji Medical Review No. 8, pages 39 to 55, and it goes without saying that these techniques are applied as a laser imager of the photothermographic material of the present invention. Further, it can also be applied as a photothermographic material for a laser imager in “AD network” proposed by Fuji Film Medical Co., Ltd. as a network system adapted to the DICOM standard.

(Use of the present invention)
The photothermographic material of the present invention forms a black and white image by a silver image, and is used as a photothermographic material for medical diagnosis, a photothermographic material for industrial photography, a photothermographic material for printing, and a photothermographic material for COM. It is preferably used.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Example 1
(Preparation of PET support)
1) Film formation Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured in phenol / tetrachloroethane = 6/4 (mass ratio) at 25 ° C.) is obtained. It was. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to prepare an unstretched film.

This was longitudinally stretched 3.3 times using rolls with different peripheral speeds, and then stretched 4.5 times with a tenter. The temperatures at this time were 110 ° C. and 130 ° C., respectively. Thereafter, the film was heat-fixed at 240 ° C. for 20 seconds and relaxed by 4% in the lateral direction at the same temperature. Thereafter, the chuck portion of the tenter was slit and then knurled at both ends, and wound at 4 kg / cm ² to obtain a roll having a thickness of 175 μm.

2) Surface corona treatment Using a solid state corona treatment machine 6KVA model manufactured by Pillar, both surfaces of the support were treated at 20 m / min at room temperature. From the current and voltage readings at this time, it was found that the support was processed at 0.375 kV · A · min / m ² . The treatment frequency at this time was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

3) Undercoat <Preparation of undercoat layer coating solution>
Formula (1) (for image forming layer side undercoat layer)
・ Pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd. 46.8 g
・ Toyobo Co., Ltd. Bironal MD-1200 10.4 g
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 1% by weight solution 11.0 g
・ MP-1000 (PMMA polymer fine particles, average particle size 0.4 μm) manufactured by Soken Chemical Co., Ltd.
0.91g
・ Distilled water 931mL

Formula (2) (for back layer 1st layer)
・ Styrene-butadiene copolymer latex 130.8 g
(Solid content 40% by mass, styrene / butadiene mass ratio = 68/32)
・ 2,4-Dichloro-6-hydroxy-S-triazine sodium salt (8% by mass aqueous solution) 5.2 g
・ 10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
・ Polystyrene particle dispersion (average particle size 2 μm, 20 mass%) 0.5 g
-854 mL of distilled water

Formula (3) (for back side second layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.5 μm, 17 mass% dispersion)
84g
・ Gelatin 7.9g
・ Shin-Etsu Chemical Co., Ltd. Metros TC-5 (2 mass% aqueous solution) 10g
・ 10% 1% aqueous solution of sodium dodecylbenzenesulfonate
・ NaOH (1% by mass) 7 g
・ Proxel (ICI) 0.5g
・ 881mL distilled water

After both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm are subjected to the corona discharge treatment, the undercoat coating solution formulation (1) is applied on one side (image forming layer surface) with a wire bar with a wet coating amount of 6. .6mL / m 2 was applied ^(per one side) and dried for 5 minutes at 180 ° C., then the amount of wet coating the coating solution for the undercoat was coated (2) by a wire bar on the rear surface (back surface) 5. was applied so as to 7 mL / ^{m 2} and dried 5 minutes at 180 ° C., wet coating amount is 8.4 mL / ^{m 2} further backside (the back face) the coating solution for the undercoat was coated (3) with a wire bar It was applied as described above and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

(Back layer)
1) Preparation of coating solution for back layer 1-1) Preparation of coating solution for antihalation layer The container was kept at 40 ° C. and gelatin (PZ gelatin manufactured by Miyagi Chemical Industry Co., Ltd.) having an isoelectric point of 4.8 was obtained. Gelatin was dissolved by adding 0.1 g of azolinone and water. Furthermore, 55 mL of 5% by mass aqueous solution of blue dye compound-2, 60 mL of 25% by mass aqueous solution of the following polymer B as a dye fixing agent, ethyl acrylate / acrylic acid copolymer (copolymerization mass ratio 95/5, ammonia water) The pH was adjusted to 7.0) 50 mL of a latex 20% by mass solution was mixed to prepare an antihalation layer coating solution having a finished solution amount of 600 mL. The pH value of the finished liquid was 7.3.

1-2) Preparation of coating solution for lower layer of back surface anti-halation layer Keeping container at 40 ° C., 50 g of isoelectric point 4.8 gelatin (PZ gelatin manufactured by Miyagi Chemical Co., Ltd.), benzoisothiazolinone 0 0.1 g and 950 mL of water were added to dissolve the gelatin. Furthermore, 2.3 mL of 1 mol / L sodium hydroxide aqueous solution was mixed. Immediately before coating, 80 mL of a 4% by mass aqueous solution of N, N-ethylenebis (vinylsulfone acetamide) was mixed. An antihalation layer lower layer coating solution having a finished solution amount of 1000 mL was used. The pH value of the finished liquid was 6.3.

1-3) Preparation of coating solution for back surface protective layer The container was kept at 40 ° C., 43 g of gelatin having an isoelectric point of 4.8 (PZ gelatin manufactured by Miyagi Chemical Co., Ltd.), 0.21 g of benzoisothiazolinone, water Was added to dissolve gelatin. Furthermore, 8.1 mL of 1 mol / L sodium acetate aqueous solution, 0.93 g of monodisperse poly (ethylene glycol dimethacrylate-co-methyl methacrylate) fine particles (average particle size 7.7 μm, particle size standard deviation 0.3 μm), liquid paraffin 5 g of 10 mass% emulsion, 10 g of 10 mass% emulsion of hexapentaisostearate dipentaerythritol, 2.3 mL of 1 mol / L sodium hydroxide aqueous solution were mixed. Furthermore, 10 mL of 5% by mass aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate, 17 mL of 3% by mass aqueous sodium polystyrenesulfonate, 2.4 mL of 2% by mass of fluorosurfactant (F-1), and fluorosurfactant Agent (F-2) 2% by mass solution 2.4 mL, ethyl acrylate / acrylic acid copolymer (copolymerization mass ratio 95/5, adjusted to pH 7.0 with ammonia water) Latex 20% by mass solution 30 mL was mixed. . Immediately before coating, 50 mL of a 4% by weight aqueous solution of 2,4-dichloro-6-hydroxy-s-triazine sodium salt was mixed to obtain a back surface protective layer coating solution having a finished liquid amount of 855 mL. The pH value of the finished liquid was 7.2.

2) Application of the back layer The antihalation layer coating solution is applied to the back surface of the undercoat support so that the gelatin coating amount of the antihalation layer lower layer coating solution is 0.5 g / m ^{2 in} order from the support. The back surface protective layer coating solution was simultaneously applied in a multilayer so that the amount was 0.9 g / m ² and the gelatin coating amount was 1.1 g / m ^2, and dried to prepare a back layer.

(Image forming layer, intermediate layer, and surface protective layer)
1. Preparation of coating materials 1) Silver halide emulsion << Preparation of silver halide emulsion 1 >>
To a solution of 1421 mL of distilled water, 3.1 mL of a 1% by mass potassium bromide solution was added, and a solution containing 3.5 mL of 0.5 mol / L sulfuric acid and 31.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 30 ° C., the solution A diluted with 92.2 mL of distilled water added to 22.22 g of silver nitrate, 15.3 g of potassium bromide and 0.8 g of potassium iodide in a distilled water volume of 97.4 mL The whole amount of the solution B diluted to 1 was added at a constant flow rate over 45 seconds. Thereafter, 10 mL of a 3.5% by mass aqueous hydrogen peroxide solution was added, and further 10.8 mL of a 10% by mass aqueous solution of benzimidazole was added. Further, a solution C in which distilled water was added to 51.86 g of silver nitrate and diluted to 317.5 mL, a solution D in which 44.2 g of potassium bromide and 2.2 g of potassium iodide were diluted with distilled water to a volume of 400 mL were added to solution C. Was added at a constant flow rate over 20 minutes, and solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of the solution C and the solution D so as to be 1 × 10 ⁻⁴ mol per mol of silver. Further, 5 seconds after the completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

The silver halide dispersion was maintained at 38 ° C. with stirring, 5 mL of a 0.34 mass% 1,2-benzisothiazolin-3-one methanol solution was added, and the temperature was raised to 47 ° C. after 40 minutes. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per mol of silver, and further 5 minutes later, tellurium sensitizer C was added in a methanol solution to a ratio of 2. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes. Thereafter, a methanol solution having a molar ratio of the spectral sensitizing dye A to the sensitizing dye B of 3: 1 was added in an amount of 1.2 × 10 ⁻³ mol as a total of the sensitizing dyes A and B per mol of silver, and N , N′-dihydroxy-N ″ -diethylmelamine in 1.3 mL of a 0.8 wt% methanol solution was added, and after an additional 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the methanol solution at a rate of 4.8 per mole of silver. × 10 ⁻³ mol, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in methanol solution is 5.4 × 10 ⁻³ mol and 1- (3-methyl) with respect to 1 mol of silver. A silver halide emulsion 1 was prepared by adding 8.5 × 10 ⁻³ mol of ureidophenyl) -5-mercaptotetrazole in an aqueous solution to 1 mol of silver.

  The grains in the prepared silver halide emulsion were silver iodobromide grains containing 3.5 mol% of iodine having an average sphere equivalent diameter of 0.042 μm and a sphere equivalent diameter variation coefficient of 20%. The particle size and the like were determined from an average of 1000 particles using an electron microscope. The {100} face ratio of the particles was determined to be 80% using the Kubelka-Munk method.

<< Preparation of silver halide emulsion 2 >>
In the preparation of silver halide emulsion 1, the liquid temperature 30 ° C. at the time of grain formation was changed to 47 ° C., and solution B was changed to diluting 15.9 g of potassium bromide to a volume of 97.4 mL with distilled water, Solution D was changed to diluting 45.8 g of potassium bromide with distilled water to a volume of 400 mL, and the addition time of solution C was changed to 30 minutes to remove potassium hexacyanoiron (II) in the same manner. A silver halide emulsion 2 was prepared. Precipitation / desalting / washing / dispersion was carried out in the same manner as silver halide emulsion 1. Further, the addition amount of tellurium sensitizer C is 1.1 × 10 ⁻⁴ mol per mol of silver, and the addition amount of methanol solution of 3: 1 in the molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is silver. The total of sensitizing dye A and sensitizing dye B per mole is 7.0 × 10 ⁻⁴ mole, and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole is added to 1 mole of silver. Same as Emulsion 1 except that 3.3 × 10 ⁻³ mol and 1- (3-methylureidophenyl) -5-mercaptotetrazole were changed to 4.7 × 10 ⁻³ mol added to 1 mol of silver. Spectral sensitization, chemical sensitization, and addition of 5-methyl-2-mercaptobenzimidazole and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole were carried out to obtain silver halide emulsion 2. . The emulsion grains of the silver halide emulsion 2 were pure silver bromide cubic grains having an average sphere equivalent diameter of 0.080 μm and a sphere equivalent diameter variation coefficient of 20%.

<< Preparation of silver halide emulsion 3 >>
In the preparation of silver halide emulsion 1, silver halide emulsion 3 was prepared in the same manner except that the liquid temperature at the time of grain formation was changed from 30 ° C. to 27 ° C. Further, precipitation / desalting / washing / dispersion was performed in the same manner as silver halide emulsion 1. The molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is 1: 1 as a solid dispersion (gelatin aqueous solution), and the addition amount is 6 × 10 ⁻ as the total of sensitizing dye A and sensitizing dye B per mole of silver. ³ moles, the amount of tellurium sensitizer C added was changed to 5.2 × 10 ⁻⁴ moles per mole of silver, and bromoauric acid was added 5 × 10 ⁻⁴ moles per silver 3 minutes after the addition of tellurium sensitizers. A silver halide emulsion 3 was obtained in the same manner as Emulsion 1 except that 2 × 10 ⁻³ mol of mol and potassium thiocyanate were added per mol of silver. The emulsion grains of the silver halide emulsion 3 were silver iodobromide grains containing 3.5 mol% of iodine having an average sphere equivalent diameter of 0.034 μm and a sphere equivalent diameter variation coefficient of 20%.

<< Preparation of mixed emulsion A for coating solution >>
70% by weight of silver halide emulsion 1, 15% by weight of silver halide emulsion 2 and 15% by weight of silver halide emulsion 3 were dissolved, and 7% by mole of silver in a 1% by weight aqueous solution of benzothiazolium iodide. × 10 ⁻³ mol was added.
Further, the amount of the one-electron oxidant produced by one-electron oxidation is 2 × 10 ⁻³ moles per mole of silver halide of each of compounds 1, 2, and 3 capable of emitting one electron or more. Added.
The adsorbing redox compounds 1 and 2 having an adsorbing group and a reducing group were each added in an amount of 5 × 10 ⁻³ mol per mol of silver halide.

  Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver. 1- (3-Methylureidophenyl) -5-mercaptotetrazole was added so as to give 0.34 g per kg of the mixed emulsion for coating solution.

2) Preparation of fatty acid silver dispersion <Preparation of fatty acid silver dispersion>
88 kg of recrystallized behenic acid, 422 L of distilled water, 49.2 L of NaOH aqueous solution having a concentration of 5 mol / L, and 120 L of t-butyl alcohol were mixed and stirred at 75 ° C. for 1 hour to obtain a sodium behenate solution. Separately, 206.2 L (pH 4.0) of an aqueous solution containing 40.4 kg of silver nitrate was prepared and kept warm at 10 ° C. A reaction vessel containing 635 L of distilled water and 30 L of t-butyl alcohol was kept at 30 ° C., and with sufficient agitation, the total amount of the previous sodium behenate solution and the total amount of silver nitrate aqueous solution were kept at a constant flow rate of 93 minutes and 15 seconds, respectively. And added over 90 minutes. At this time, only the silver nitrate aqueous solution is added for 11 minutes after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution is started. After the addition of the aqueous silver nitrate solution, only the sodium behenate solution is added for 14 minutes and 15 seconds. It was made to be. At this time, the temperature in the reaction vessel was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant. The pipe of the addition system for the sodium behenate solution was kept warm by circulating hot water outside the double pipe so that the liquid temperature at the outlet at the tip of the addition nozzle was 75 ° C. Moreover, the piping of the addition system of the silver nitrate aqueous solution was kept warm by circulating cold water outside the double pipe. The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically around the stirring axis, and were adjusted so as not to contact the reaction solution.

After completion of the addition of the sodium behenate solution, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm. Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying.
When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average values were a = 0.21 μm, b = 0.4 μm, c = 0.4 μm, average aspect ratio 2.1, and equivalent sphere diameter. It was a crystal with a variation coefficient of 11% (a, b, and c are defined in the text).

  19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to a wet cake corresponding to a dry solid content of 260 kg to make a total amount of 1000 kg, and then slurried with a dissolver blade, and a pipeline mixer (manufactured by Mizuho Kogyo Co., Ltd.). : PM-10 type).

Next, the pre-dispersed stock solution is adjusted to a pressure of 1150 kg / cm ² in a disperser (trade name: Microfluidizer M-610, manufactured by Microfluidics International Corporation, using a Z-type interaction chamber) three times. Treatment gave a silver behenate dispersion. The cooling operation was carried out by installing a serpentine heat exchanger before and after the interaction chamber, and adjusting the temperature of the refrigerant to a dispersion temperature of 18 ° C.

3) Preparation of benzotriazole silver dispersion << Preparation of benzotriazole silver dispersion A >>
A 0.4 mol / L silver nitrate aqueous solution is referred to as solution A, and an aqueous solution containing 0.8 mol / L benzotriazole and 0.84 mol / L sodium hydroxide is referred to as solution B. To 700 mL of an aqueous solution containing 30 g of gelatin maintained at 65 ° C., 300 mL of solution A and solution B were added over 10 minutes while maintaining the silver potential at 0 mV with respect to the saturated calomel electrode. After 5 minutes, 300 mL of solution A and solution B were added over 20 minutes while maintaining the same silver potential. The particles of the benzotriazole silver dispersion prepared here were strip-shaped particles having an average major axis of 0.82 μm, an average medium diameter of 0.23 μm, and an average minor axis of 0.06 μm. The particle size was determined from the average of 300 particles using an electron microscope.
After dropping the temperature to 25 ° C., 92 mL of Demol N (10% by mass aqueous solution, manufactured by Kao Corporation) was added with stirring, the pH was adjusted to 4.1 using 1 mol / L sulfuric acid, and stirring was performed. The particles were settled by stopping and standing. Thereafter, 1000 cc of the supernatant water was removed, and after that, 1500 ml of washing water at room temperature was added, and then the solution was settled again to remove the supernatant water. All the desalting and washing steps were performed at 25 ° C. It took 48 minutes after the first stirring was stopped to drain the first time. Thereafter, the temperature was raised to 50 ° C., 40 mL of 1 mol / L sodium hydroxide was added with stirring, 10 mL of a methanol solution of benzoisothiazolinone (3.5% by mass), and sodium benzenethiosulfonate was added. 7.7 mL of a methanol solution (1% by mass) was added, and after stirring for 80 minutes, the pH was adjusted to 7.8 using 1 mol / L sulfuric acid to prepare benzotriazole silver dispersion A.

<< Preparation of Silver Benzotriazole Dispersions BF >>
Preparation of silver benzotriazole was carried out in exactly the same manner as dispersion A, except that the temperature of the washing water used after the preparation of the particles (water washing temperature) and the temperature of the desalting step were 30 ° C. (dispersion B) and 35 ° C. (dispersion). F were prepared from benzotriazole silver dispersion B in the same manner except that the product C), 40 ° C. (dispersion D), 45 ° C. (dispersion E) and 50 ° C. (dispersion F) were used.

  When the time required for the first desalting and the amount of silver lost in all desalting / washing steps were measured, the following values were obtained with respect to the amount of silver nitrate added.

Dispersion Demineralized washing temperature Time (minutes) Silver lost by demineralized washing (%) Remarks A 25 ° C 48 minutes 7.5% Comparison
B 30 ° C 39 minutes 3.9% Invention C 35 ° C 35 minutes 3.5% Invention D 40 ° C 28 minutes 3.0% Invention E 45 ° C 25 minutes 2.2% Invention F 50 ° C 25 minutes 2 .2% The present invention

  From the above results, when the desalting / water washing step was performed at a low temperature around 25 ° C. such as 25 ° C., the time required for this step was long, and a large amount of silver was lost in the step. This is different from what is normally experienced during the preparation of silver halide grains, because when the specific gravity of the benzotriazole silver salt is low and the temperature is low, it is difficult to settle and the supernatant water is cloudy. In contrast, when the washing temperature is 30 ° C. or higher, preferably 35 ° C. or higher, more preferably 40 ° C. or higher, the time required for the process is reduced and the amount of silver lost is reduced. This was an effect that could not be predicted from previous knowledge.

4) Preparation of reducing agent dispersion << Preparation of reducing agent-1 dispersion >>
10 kg of water was added to 16 kg of a 10% by weight aqueous solution of reducing agent-1 (2,2′-methylenebis- (4-ethyl-6-tert-butylphenol)) and denatured polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203). Add and mix well to make a slurry. This slurry was fed with a diaphragm pump, dispersed for 3 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0. 2 g and water were added to adjust the concentration of the reducing agent to 25% by mass. This dispersion was heat-treated at 60 ° C. for 5 hours to obtain a reducing agent-1 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.4 μm or less. The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

<< Preparation of Reducing Agent-2 Dispersion >>
10 masses of reducing agent-2 (6,6′-di-t-butyl-4,4′-dimethyl-2,2′-butylidenediphenol) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 16 kg of% aqueous solution and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump, dispersed in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm for 3 hours 30 minutes, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the reducing agent to 25% by mass. This dispersion was heated at 40 ° C. for 1 hour, and then further heated at 80 ° C. for 1 hour to obtain a reducing agent-2 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.50 μm and a maximum particle diameter of 1.6 μm or less. The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

5) Preparation of Development Accelerator-1 Dispersion 10 kg of Development Accelerator-1 and 20 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) were added with 10 kg of water and mixed well. To make a slurry. This slurry was fed with a diaphragm pump and dispersed in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm for 3 hours 30 minutes, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the development accelerator to 20% by mass to obtain a development accelerator-1 dispersion. The development accelerator particles contained in the development accelerator dispersion thus obtained had a median diameter of 0.48 μm and a maximum particle diameter of 1.4 μm or less. The obtained development accelerator dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.
6) Preparation of Development Accelerator-2 Dispersion The solid dispersion of Development Accelerator-2 was also dispersed in the same manner as in Development Accelerator-1, and a 23% by mass dispersion was obtained.

7) Preparation of polyhalogen compound << Preparation of organic polyhalogen compound-1 dispersion >>
10 kg of organic polyhalogen compound-1 (tribromomethanesulfonylbenzene), 10 kg of a 20% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), 0.4 kg of a 20% by weight aqueous solution of sodium triisopropylnaphthalenesulfonate, Then, 14 kg of water was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 26% by mass to obtain an organic polyhalogen compound-1 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of organic polyhalogen compound-2 dispersion >>
10 kg of an organic polyhalogen compound-2 (N-butyl-3-tribromomethanesulfonylbenzoamide), 20 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and 20 of sodium triisopropylnaphthalenesulfonate 0.4 kg of a mass% aqueous solution was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 30% by mass. This dispersion was heated at 40 ° C. for 5 hours to obtain an organic polyhalogen compound-2 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.3 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

8) Preparation of Phthalazine Compound-1 Solution 8 kg of modified polyvinyl alcohol MP203 manufactured by Kuraray Co., Ltd. was dissolved in 174.57 kg of water, and then 3.15 kg of a 20% by weight aqueous solution of sodium triisopropylnaphthalenesulfonate and phthalazine compound-1 ( 14.28 kg of a 70% by weight aqueous solution of 6-isopropylphthalazine) was added to prepare a 5% by weight solution of phthalazine compound-1.

9) Preparation of mercapto compound << Preparation of aqueous solution of mercapto compound-1 >>
7 g of mercapto compound-1 (1- (3-sulfophenyl) -5-mercaptotetrazole sodium salt) was dissolved in 993 g of water to obtain a 0.7% by mass aqueous solution.

<< Preparation of Mercapto Compound-2 Aqueous Solution >>
20 g of mercapto compound-2 (1- (3-methylureidophenyl) -5-mercaptotetrazole) was dissolved in 980 g of water to obtain a 2.0 mass% aqueous solution.

10) Preparation of isoprene latex liquid Isoprene latex (TP-2) was prepared as follows.
Add 1500g of distilled water to the polymerization kettle of the gas monomer reactor (Pressure Glass Industry Co., Ltd. TAS-2J type), heat at 90 ° C for 3 hours, and passivate to the stainless steel surface of the polymerization kettle and members of the stainless steel stirrer A film is formed. In this polymerized kettle, 582.28 g of distilled water bubbled with nitrogen gas for 1 hour, 9.49 g of surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)), 1 mol / L NaOH Of ethylenediaminetetraacetic acid tetrasodium salt 0.20 g, styrene 314.99 g, isoprene 190.87 g, acrylic acid 10.43 g, tert-dodecyl mercaptan 2.09 g, and the reaction vessel was sealed and stirred at 225 rpm. The mixture was stirred and heated to an internal temperature of 65 ° C. A solution prepared by dissolving 2.61 g of ammonium persulfate in 40 mL of water was added thereto, and the mixture was stirred as it was for 6 hours. The polymerization conversion rate at this time was 90% from the solid content measurement. Here, a solution in which 5.22 g of acrylic acid was dissolved in 46.98 g of water was added, 10 g of water was subsequently added, and a solution in which 1.30 g of ammonium persulfate was dissolved in 50.7 mL of water was further added. After the addition, the temperature was raised to 90 ° C. and stirred for 3 hours. After the reaction was completed, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion was used using 1 mol / L NaOH and NH ₄ OH. = 1: 5.3 (molar ratio) was added and adjusted to pH 8.4. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored, and 1248 g of isoprene latex TP-2 was obtained. When the halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 142 ppm.

  The latex has an average particle size of 113 nm, Tg = 15 ° C., solid content concentration of 41.3 mass%, equilibrium water content at 25 ° C. and 60% RH of 0.4 mass%, ionic conductivity of 5.23 mS / cm (of ionic conductivity). Measurement was conducted at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.).

11) Preparation of SBR latex liquid (TP-1) In a polymerization kettle of a gas monomer reactor (TAS-2J type manufactured by Pressure Glass Industrial Co., Ltd.), 287 g of distilled water and a surfactant (Pionin A-43-S (Takemoto) (Oil & Fats Co., Ltd.): solid content 48.5% by mass) 7.73 g, 1 mol / L, NaOH 14.06 mL, ethylenediaminetetraacetic acid tetrasodium salt 0.15 g, styrene 255 g, acrylic acid 11.25 g, tert-dodecyl mercaptan 3.0 g was added, and the reaction vessel was sealed and stirred at a stirring speed of 200 rpm.
After degassing with a vacuum pump and repeating nitrogen gas replacement several times, 108.75 g of 1,3-butadiene was injected to raise the internal temperature to 60 ° C. A solution prepared by dissolving 1.875 g of ammonium persulfate in 50 mL of water was added thereto and stirred as it was for 5 hours. The temperature was further raised to 90 ° C. and stirred for 3 hours. After completion of the reaction, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion = 1 using 1 mol / L NaOH and NH ₄ OH = 1. Addition treatment was performed so that the molar ratio was 5.3 (molar ratio), and the pH was adjusted to 8.4. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored, and 774.7 g of SBR latex TP-1 was obtained.
When the halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 145 ppm.

  The latex has a gelation rate of 73% by mass, an average particle size of 90 nm, Tg = 17 ° C., a solid content concentration of 44% by mass, an equilibrium water content of 0.6% by mass at 25 ° C. and 60% RH, and an ionic conductivity of 4.80 mS / cm (Ion conductivity was measured at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Radio Industry Co., Ltd.).

12) Preparation of Magenta Dye-1 Dispersion 1.0 kg of magenta dye-1 and 3.0 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.) and a surfactant (Pionin A-43) 42 g of S (48% by mass aqueous solution of Takemoto Yushi Co., Ltd.) and 3.0 g of antifoaming agent (Surfinol 104E (Shin-Etsu Chemical Co., Ltd.)) were added and mixed well to obtain a slurry.
This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 1. 0 g and water were added to adjust the concentration of the water-insoluble azomethine dye to 10% by mass. This dispersion was heated at 40 ° C. for 2 hours to obtain a magenta dye-1 dispersion. The magenta dye-1 dispersion thus obtained had a median diameter of 0.49 μm and a maximum particle diameter of 2.6 μm or less. The obtained dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

2. Preparation of coating solution

1) Preparation of image forming layer coating liquid-1 1000 g of fatty acid silver dispersion A obtained above, 264 mL of water, 4.7 g of magenta dye-1 dispersion, 25 g of 5% by weight aqueous solution of blue dye compound-2, organic polyhalogen compound -1 dispersion 28 g, organic polyhalogen compound-2 dispersion 47 g, phthalazine compound-1 solution 177 g, SBR latex (TP-1) liquid 500 g, isoprene latex (TP-2) liquid 570 g, reducing agent-1 dispersion 80 g , 75 g of reducing agent-2 dispersion, 4.8 g of development accelerator-1 dispersion, 2.2 g of development accelerator-2 dispersion, 4 mL of mercapto compound-1 aqueous solution, and 4 mL of mercapto compound-2 aqueous solution were sequentially added and coated. Immediately before, 118 g of silver halide mixed emulsion A was added and mixed well, and the image forming layer coating solution was directly fed to the coating die and coated.

The viscosity of the image forming layer coating solution was 25 [mPa · s] at 40 ° C. (No. 1 rotor, 60 rpm) as measured with a B-type viscometer of Tokyo Keiki.
The viscosity of the coating solution at 38 ° C. using a Haake RheoStress RS150 is 35, 37, 34, 25, 16 [mPa · s at shear rates of 0.1, 1, 10, 100, 1000 [1 / second], respectively. s].

  The amount of zirconium in the coating solution was 0.22 mg per 1 g of silver.

2) Preparation of intermediate layer coating solution A Polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.) 1000 g, sulfosuccinic acid di (2-ethylhexyl) sodium salt 5 mass% aqueous solution 42 mL, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / Acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) 19 mass% latex 9800 mL 27% 5% aqueous solution of aerosol OT (American Cyanamid Co., Ltd.) Add 215 mL of a 20% by mass aqueous solution of ammonium salt and 4000 mL of water, adjust with NaOH so that the pH is 7.0, and use it as an intermediate layer coating solution, and send it to the coating die so that it becomes 7.8 mL / m ^2. did.
The viscosity of the coating solution was 25 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3) Preparation of surface protective layer first layer coating solution 100 g of inert gelatin and 10 mg of benzoisothiazolinone were dissolved in 704 mL of water, and a methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio) 57/8/28/5/2) 180 g of latex 19 wt% solution, 46 mL of 15 wt% methanol solution of phthalic acid, and 5.4 mL of 5 wt% aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate The mixture was mixed, and immediately before coating, 40 mL of 4% by weight chromium alum was mixed with a static mixer, and the mixture was fed to the coating die so that the coating liquid amount was 33.9 mL / m ² . When adding the benzotriazole silver dispersion, 146 g of each was added.
The viscosity of the coating solution was 20 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

4) Preparation of surface protective layer second layer coating solution 100 g of inert gelatin and 10 mg of benzoisothiazolinone are dissolved in 785 mL of water, 10 g of 10% by weight emulsion of liquid paraffin, 10% by weight of dipentaerythritol hexaisostearate 30 g of emulsion, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) latex 19% by weight liquid 180 g, phthalic acid 15% by weight methanol 40 mL of a solution, 11 mL of a 1% by mass solution of a fluorosurfactant (F-1), 11 mL of a 1% by mass aqueous solution of a fluorosurfactant (F-2), and di (2-ethylhexyl) sodium sulfosuccinate 28 mL of 5 mass% aqueous solution, polymethyl methacrylate fine particles (average particle diameter A mixture of 25 g (3.6 μm, volume weighted average distribution 60%) was used as the surface protective layer coating solution, and the solution was fed to the coating die so as to be 4.2 mL / m ² .
The viscosity of the coating solution was 19 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3. Production of photothermographic material 1) Production of photothermographic material-101 In the order of the image forming layer, the intermediate layer A, the first surface protective layer, and the second surface protective layer from the undercoat surface to the surface opposite to the back surface. Samples of the photothermographic material were prepared by simultaneous multilayer coating by the slide bead coating method. At this time, the coating solution for the image forming layer and the intermediate layer A was adjusted to 31 ° C., the coating solution for the first surface protective layer was adjusted to 36 ° C., and the coating solution for the second surface protective layer was adjusted to 37 ° C.
The coating amount (g / m ² ) of each compound in the image forming layer is as follows.

・ Fatty acid silver 6.00
-Magenta dye-1 0.11
Blue dye compound-2 0.029
-Polyhalogen compound-1 0.17
・ Polyhalogen compound-2 0.33
-Phthalazine compound-1 0.20
-Isoprene latex 5.50
-SBR latex 5.10
・ Reducing agent-1 0.46
・ Reducing agent-2 0.43
Development accelerator-1 0.022
Development accelerator-2 0.012
Mercapto compound-1 0.001
Mercapto compound-2 0.002
Silver halide (as Ag) 0.15

The coating and drying conditions are as follows.
The coating was performed at a speed of 140 m / min, the gap between the coating die tip and the support was set to 0.10 mm to 0.30 mm, and the pressure in the decompression chamber was set to be 196 Pa to 882 Pa lower than the atmospheric pressure. The support was neutralized with an ion wind before coating.
In the subsequent chilling zone, the coating liquid is cooled with a wind at a dry bulb temperature of 10 ° C. to 20 ° C., then transported in a non-contact manner, and dried at a dry bulb temperature of 23 ° C. to 45 ° C. It dried with the drying wind of 15 degreeC and the wet-bulb temperature of 15 to 21 degreeC.
After drying, the humidity was adjusted at 25 ° C. and humidity of 40% RH to 60% RH, and then the film surface was heated to 70 ° C. to 90 ° C. After heating, the film surface was cooled to 25 ° C.
The photothermographic material thus prepared had a Beck smoothness of 550 seconds on the image forming layer surface side and 130 seconds on the back surface. Further, the pH of the film surface on the image forming layer surface side was measured and found to be 6.0.

2) Preparation of photothermographic material 102 to 107 Photothermographic material 102-107 was the same as photothermographic material 101 except that benzotriazole silver salt was added to the first surface protective layer as shown in Table 5. Thus, photothermographic materials -102 to 107 were prepared.

  The chemical structures of the compounds used in the examples of the present invention are shown below.

4). Evaluation of photographic performance 1) Preparation Each sample was cut into half-cut size (43 cm length x 35 cm width), packaged in the following packaging materials in an environment of 25 ° C. and 50% RH, stored at room temperature for 2 weeks, and then Was evaluated.
Laminate film consisting of PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% by mass of carbon:
Oxygen permeability: 0.02 mL / atm · m ² · 25 ° C · day;
Moisture permeability: 0.10 g / atm · m ² · 25 ° C · day.

2) Exposure / development of photothermographic material Each sample was exposed and heat-developed (107 ° C.-121 ° C.) with a dry laser imager DRYPIX 7000 (equipped with a 660 nm semiconductor laser with a maximum output of 50 mW (IIIB)). The heat development time was modified with three panel heaters set at −121 ° C. so that the heat development time could be varied and tested.) The resulting image was evaluated with a densitometer.

3) Evaluation conditions (photographability)
Fog: The density of the unexposed area was taken as fog.
Sensitivity: Reciprocal of the exposure amount necessary to obtain a density of 1.2.
Dmax: the maximum density that saturates when the exposure is increased.

(Fingerprint traces)
In a dark room at 25 ° C. and 60% RH, 10 examiners touched the image forming layer surface of the unexposed photosensitive material with bare hands, and then exposed and developed to a density of 1.2. The obtained sample was evaluated for fingerprint trace contamination before exposure by sensory evaluation.
(Double-circle): Dirt is hardly recognized.
○: Traces of fingerprints from one to two people are observed, but the degree is slight.
Δ: Traces of fingerprints of 3 or more people are observed, and the degree is strong.
X: Traces of fingerprints of 5 or more people are observed, and the degree is extremely strong.

(Raw preservation)
After storing for 20 days in an environment of 45 ° C. and 40% RH, the film was exposed and developed to determine photographic sensitivity and fog.

4) Evaluation results The results obtained are shown in Table 5.
As is apparent from Table 5, even when the benzotriazole silver salt of the present invention is added, the maximum density immediately after development does not change at all, and it is clear that the silver salt does not contribute to the image density. By using benzotriazole silver salt, fingerprint desensitization is improved and raw storage stability is also improved. However, compared with silver salt A, silver salts B to F of the present invention have less sensitivity reduction and are preferred. won.
Although this cause is uncertain, it is considered that adverse effects such as agglomeration at the time of demineralized water washing of the benzotriazole silver salt are relatively small in the present invention, and the effect becomes clearer. In this way, the demineralized water washing method of the present application has a shorter process time, a small amount of silver loss, and an effective benzotriazole silver salt can be prepared. In the preparation of conventional nitrogen-containing heterocyclic silver salts, It was a positive result that was not suggested at all.

Example 2
1) Preparation of Samples 201 to 206 In Samples 102 and 106 of Example 1, the addition layer of the benzotriazole silver salt dispersion was changed as shown in Table 6.

2) Performance evaluation results Table 6 shows the results evaluated in the same manner as in Example 1.
When the benzotriazole silver salt of the present invention was added to any of the image forming layer, the surface protective second layer, the intermediate layer and the surface protective first layer, a preferable result was obtained as compared with the comparative compound.

Example 3
In the sample 105 of the present invention of Example 1, the coating amount of the fluorine-based polymer latex FL-1 to FL-5 described in the present specification was 0.1 g / m ² in the surface protective layer second layer coating solution. Samples 301 to 305 were added so as to satisfy the same evaluation as in Example 1. As a result, the same preferable results as in Sample 105 of Example 1 were obtained.

Example 4
Similar to the preparation of benzotriazole silver dispersion A, except that the silver potential was changed to +100 mV, the grain formation temperature 65 ° C. was changed to 45 ° C., and the total addition time of silver nitrate and benzotriazole liquid was changed to ½, Otherwise, a benzotriazole silver dispersion G was prepared in the same manner. The particles of the obtained benzotriazole silver dispersion were rod-like particles having an average major axis of 0.48 μm, a slightly elliptical cross section, and an average equivalent circle diameter of 0.07 μm in cross section.

Diafiltration / ultrafiltration apparatus (Osmonics model 21-HZ20-S8J osmotic membrane having an effective surface area of 0.34 m ² and a nominal molecular weight cut-off of 50,000 under the condition that the obtained benzotriazole silver salt was kept at 45 ° C. Equipped with a cartridge). This apparatus was operated so that the pressure applied to the osmotic membrane was 3.5 kg / cm ² (50 lb / in ² ), and the pressure on the downstream side of the osmotic membrane was 20 kg / cm ² (50 lb / in ² ). The permeate was replaced with deionized until 24 kg of permeate was removed from the dispersion. At that stage, the substitution water was stopped, and the apparatus was operated until the dispersion reached a concentration of 28% by weight of solid content, whereby a benzotriazole silver salt dispersion G was obtained. The amount of silver lost in the process was 2.1%. After preparing in the same manner as benzotriazole silver salt G, the above ultrafiltration was performed at 28 ° C. to obtain benzotriazole silver salt H. The amount of silver lost in this process was 5.2%.
It was found that the amount of silver lost in the desalting water washing by the ultrafiltration step at 45 ° C. is less than 28 ° C. and the present invention is preferable.

Claims (18)

  A method for producing silver salt particles of a nitrogen-containing heterocyclic compound, wherein the nitrogen-containing heterocyclic compound and a water-soluble silver compound are mixed to form particles, and then formed as a by-product at a temperature of 30 ° C. or higher. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound, wherein the salt is removed.   The first removal of water-soluble salts by-produced by at least one means selected from the centrifugal filtration method, ultrafiltration method, suction filtration method, electrodialysis, and decantation method at a temperature of 30 ° C. or higher. The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to claim 1, wherein a salt process is performed.   Following the first desalting step, water is added and washed, and at least one selected from centrifugal filtration, ultrafiltration, suction filtration, electrodialysis, and decantation at a temperature of 30 ° C. or higher. The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to claim 2, wherein a second desalting step is performed by two means.   The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to any one of claims 1 to 3, wherein the silver salt of the nitrogen-containing heterocyclic compound is benzotriazole silver.   The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to any one of claims 1 to 4, wherein a temperature at which the particles are precipitated is 35 ° C or higher.   The method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to any one of claims 1 to 5, wherein a temperature at which the particles are precipitated is 40 ° C or higher.   The inclusion according to any one of claims 1 to 5, wherein the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound includes at least two steps. A method for producing silver salt particles of a nitrogen heterocyclic compound.   The addition rate of the water-soluble silver compound in the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound is faster in the second step than in the first step. Item 8. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound according to Item 7.   9. The method according to claim 1, wherein the step of mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound to form particles is performed in the presence of a water-soluble binder. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound.   The nitrogen-containing composition according to any one of claims 1 to 9, wherein the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound is performed at a temperature of 60 ° C or higher. A method for producing silver salt particles of a heterocyclic compound.   The change in pH in the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound is 3 or less, according to any one of claims 1 to 10, A method for producing silver salt particles of a nitrogen-containing heterocyclic compound.   The nitrogen-containing heterocycle compound and a water-soluble silver compound are mixed to form a seed crystal, and thereafter the seed crystal is grown by adding silver salt particles of the nitrogen-containing heterocycle compound. The manufacturing method of the silver salt particle | grains of the nitrogen-containing heterocyclic compound of any one of Claims 1-11.   13. The nitrogen-containing composition according to claim 1, wherein an oxidizing agent is added in the step of forming particles by mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound. A method for producing silver salt particles of a heterocyclic compound.   The adsorbing compound is added to the particles after mixing the nitrogen-containing heterocyclic compound and the water-soluble silver compound to form particles. A method for producing silver salt particles of a nitrogen-containing heterocyclic compound.   A photothermographic material containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent on at least one surface of a support, wherein at least one part of the non-photosensitive organic silver salt is A photothermographic material comprising silver salt particles of a nitrogen-containing heterocyclic compound produced by the production method according to any one of claims 1 to 14.   16. The photothermographic material according to claim 15, wherein the silver salt particles of the nitrogen-containing heterocyclic compound do not substantially contribute to the heat-developable image density.   The image forming layer containing at least the photosensitive silver halide, the fatty acid silver salt, the reducing agent and the binder is provided on at least one surface of the support, and the same surface side as the image forming layer of the support. 17. The photothermographic material according to claim 15, further comprising a non-photosensitive layer containing silver salt particles of the nitrogen-containing heterocyclic compound.   18. The ratio of the silver salt of the nitrogen-containing heterocyclic compound to the fatty acid silver salt is 0.5 mol% or more and 50 mol% or less in terms of silver molar ratio. The photothermographic material according to Item.