JP2007057708A - Heat developable sensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable sensitive material having low fogging, high sensitivity and high image density. <P>SOLUTION: The heat developable sensitive material comprises an image forming layer at least comprising photosensitive silver halide, a nonsensitive organic silver salt, a reducing agent for silver ions and a binder on at least either face in a support. As the binder, polyvinyl acetal is comprised, and, as the reducing agent, a coupler containing a compound expressed by formula (1), and capable of forming pigment by being reacted with an oxidized product in the reducing agent is comprised: in the formula (1), R<SB>1</SB>, R<SB>2</SB>, R<SB>3</SB>and R<SB>4</SB>independently denotes a hydrogen atom or a substituent substitutable into a benzene ring, respectively; and R<SB>5</SB>denotes an alkyl group, an aryl group or a heterocycle group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photothermographic material suitably used in the field of medical diagnostic films, the field of photoengraving films, and the like.

  In recent years, in the medical field and the printing plate making field, dry development of photographic development processing is strongly desired from the viewpoint of environmental protection and space saving. In these fields, digitization has progressed, and image information is taken into a computer, stored, processed if necessary, and photothermographic material is developed by laser image setter or laser imager at the required place by communication. Systems that produce images on the spot and develop images on the spot are rapidly spreading. As a photothermographic material, it is necessary to form a clear black image having high resolution and sharpness that can be recorded by laser exposure with high illuminance. As such digital imaging recording materials, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed, but for medical imaging applications, image quality (sharpness, It is unsatisfactory in terms of graininess, gradation, and image color tone) and recording speed (sensitivity), and has not reached a level that can replace conventional wet-development medical silver halide films.

  A photothermographic material using an organic silver salt is already known. The photothermographic material contains a reducible silver salt (for example, organic silver salt), a photosensitive silver halide, and, if necessary, a toning agent for controlling the color tone of silver dispersed in a binder matrix. have.

When the photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, an oxidation-reduction reaction occurs between the silver halide or reducible silver salt (functioning as an oxidizing agent) and the reducing agent, resulting in black A silver image is formed. This oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by image exposure. As a result, a black silver image is formed in the exposed area.
It is known to use polyvinyl butyral as a binder for an image forming layer (for example, see Non-Patent Document 1).

  On the other hand, photothermographic materials containing a color developer and a coupler are also known (see, for example, Patent Documents 1 to 4). The photosensitive silver halide used was silver chloride, silver bromide, silver chlorobromide, silver iodobromide, or silver iodochlorobromide. However, the turbidity and opacity of the film increase due to light scattering and absorption by silver halide, so that the fog becomes extremely high at 0.58 to 1.2 as described in the examples. Therefore, as described in Patent Documents 2 and 3, the obtained image is a primary document and is not an image that can be directly observed, but is digitized based on this image and further subjected to image processing for fogging. An image that can be observed is obtained only after obtaining a reprocessed image with reduced gradation and color tone.

A photothermographic material using an organic silver salt has a great feature in that all elements necessary for image formation are previously contained in the film, and an image can be formed only by heating after exposure. On the other hand, however, the fog is high, and in particular, an increase in fog is a big problem when trying to obtain a high image density or high sensitivity, and reduction of the fog has always been a demanded issue.
Japanese Patent Application Laid-Open No. 2001-312026 JP 2003-215767 A Japanese Patent Application Laid-Open No. 2003-215564 US Pat. No. 6,242,166 D. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials), 8th Edition, Sturge (Stuart) (Walworth), edited by A. Shepp, Chapter 9, 273, 1989.

  An object of the present invention is to provide a photothermographic material having low fog, high sensitivity and high image density.

The above problems have been solved by the following means.
<1> A photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions and a binder on at least one surface of a support. And a polyvinyl acetal as the binder, a compound represented by the following general formula (1) as the reducing agent, and a coupler capable of forming a dye by reacting with an oxidation product of the reducing agent. Photothermographic material characterized by:

(In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom or a substituent which can be substituted on a benzene ring, and R ₅ represents an alkyl group, an aryl group or a heterocyclic group. To express.).
<2> The photothermographic material according to <1>, wherein the polyvinyl acetal is a compound represented by the following general formula (VA):

(In the formula, R represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or an aryl group. X is 10 mol% to 50 mol%, Y is 0 mol% to 10 mol%, Z is 50 mol% to 90 mol%).
<3> The photothermographic material according to <2>, wherein in the general formula (VA), R is a butyl group.
<4> The photothermographic material according to any one of <1> to <3>, which contains at least two types of the couplers.
<5> The photothermographic material according to <4>, wherein hues of color images formed from the at least two types of couplers are complementary to each other.
<6> The coupler is represented by the following general formulas (C-1), (C-2), (C-3), (M-1), (M-2), (M-3), (Y-1). The photothermographic material according to any one of <1> to <5>, wherein the photothermographic material is a compound selected from the group consisting of: (Y-2) and (Y-3):

(Wherein X ₁ represents a hydrogen atom or a leaving group, Y ₁ and Y ₂ represent an electron-withdrawing substituent, and R ₁ represents an alkyl group, an aryl group, or a heterocyclic group);

(Wherein X ₂ represents a hydrogen atom or a leaving group, R ₂ represents an acylamino group, a ureido group or a urethane group, R ₃ represents a hydrogen atom, an alkyl group or an acylamino group, R ₄ represents a hydrogen atom, or Represents a substituent, R ₃ and R ₄ may be linked to each other to form a ring);

(Wherein X ₃ represents a hydrogen atom or a leaving group, R ₅ represents a carbamoyl group or a sulfamoyl group, and R ₆ represents a hydrogen atom or a substituent);

(Wherein X ₄ represents a hydrogen atom or a leaving group, R ₇ represents an alkyl group, an aryl group or a heterocyclic group, and R ₈ represents a substituent);

(Wherein X ₅ represents a hydrogen atom or a leaving group, R ₉ represents an alkyl group, an aryl group or a heterocyclic group, and R ₁₀ represents a substituent);

(Wherein X ₆ represents a hydrogen atom or a leaving group, R ₁₁ represents an alkyl group, an aryl group, an acylamino group or an anilino group, and R ₁₀ represents an alkyl group, an aryl group or a heterocyclic group);

(Wherein X ₇ represents a hydrogen atom or a leaving group, R ₁₃ represents an alkyl group, an aryl group or an indoleenyl group, and R ₁₄ represents an aryl group or a heterocyclic group);

(Wherein X ₈ represents a hydrogen atom or a leaving group, Z represents a divalent group necessary to form a 5- to 7-membered ring, and R ₁₅ represents an aryl group or a heterocyclic group. );

(In the formula, X ₉ represents a hydrogen atom or a leaving group, R ₁₆ , R ₁₇ and R ₁₈ each represent a substituent, n represents an integer of 0 to 4, and m represents an integer of 0 to 5. When n or m is 2 or more, the plurality of R ₁₆ and R ₁₇ may be the same group or different groups.
<7> The photothermographic material according to any one of <1> to <6>, wherein the coated silver amount is from 0.3 g / m ^{2 to} 1.3 g / m ² .
<8> The photothermographic material according to any one of <1> to <7>, wherein methyl ethyl ketone is contained in an amount of from 0.1 mg / m ^{2 to} 150 mg / m ² .
<9> The photothermographic material according to any one of <1> to <8>, wherein an average grain size of the photosensitive silver halide is 0.01 μm or more and 0.2 μm or less.
<10> 50% or more of the total projected area of the photosensitive silver halide is a tabular grain having an average aspect ratio of 2 or more, and the average grain size is 0.3 μm or more and 8.0 μm or less. <1> to <8> The photothermographic material according to any one of <1> to <8>.
<11> The photothermographic material according to <9> or <10>, wherein the photosensitive silver halide has a silver iodide content of 35% or less.
<12> The photothermographic material according to <9> or <10>, wherein the photosensitive silver halide has a silver iodide content of 40% or more.

  According to the present invention, a photothermographic material having low fog, high sensitivity and high image density can be provided.

  The photothermographic material of the present invention has an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions and a binder on at least one surface of a support. A photothermographic material comprising polyvinyl acetal as the binder, a compound represented by the general formula (1) as the reducing agent, and reacting with an oxidation product of the reducing agent to form a dye. Contains the resulting coupler.

The present invention is described in detail below.
The reducing agent contained in the photothermographic material of the present invention is a compound that hardly absorbs in the visible region. However, when the photothermographic material of the present invention is thermally developed, it itself acts as a reducing agent or is reduced. The release of the agent contributes to the formation of a silver image, producing its own oxidant or the oxidant of the released reducing agent. When these oxidants react with the coupler compound, a dye is formed, and an image-wise dye image corresponding to the silver image is obtained.

(Reducing agent: compound represented by general formula (1))
The compound represented by the general formula (1) is a developer capable of reducing an organic silver salt, and its oxidized form can form a dye by coupling reaction with a coupler.
In the general formula (1), R ₁ and R ₂ represent a hydrogen atom or a substituent that can be substituted on the benzene ring, preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy Group, acyloxy group, sulfonyloxy group, alkylthio group, arylthio group, amino group, anilino group, acylamino group, sulfonamido group, ureido group, urethane group, acyl group, alkoxycarbonyl group, carbamoyl group, sulfonyl group, sulfoxide group, A sulfamoyl group, a cyano group, a nitro group, or a phosphoryl group.
R ₁ and R ₂ are more preferably a halogen atom, an alkyl group, an alkoxy group, an acyl group, an oxycarbonyl group, a carbamoyl group, a sulfonyl group, or a sulfamoyl group, and a halogen atom, an alkyl group, a carbamoyl group, or a sulfamoyl group is Further preferred. When R ₁ and R ₂ are alkyl groups, at least one of them is preferably a secondary or tertiary alkyl group, and more preferably a tertiary alkyl group. When R ₁ and R ₂ are halogen atoms, they are preferably chlorine atoms or bromine atoms, and more preferably chlorine atoms. R ₁ and R ₂ each preferably have 16 or less carbon atoms, more preferably 12 or less, and still more preferably 8 or less.

R ₃ and R ₄ represent a hydrogen atom or a substituent that can be substituted on the benzene ring, and preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an acyloxy group, a sulfonyloxy Group, alkylthio group, arylthio group, amino group, anilino group, acylamino group, sulfonamido group, ureido group, urethane group, acyl group, alkoxycarbonyl group, carbamoyl group, sulfonyl group, sulfoxide group, sulfamoyl group, cyano group, nitro group Group or phosphoryl group. R ₃ and R ₄ are more preferably a hydrogen atom, a halogen atom, or an alkyl group, and even more preferably a hydrogen atom or a halogen atom.

R ₅ represents an alkyl group, an aryl group, or a heterocyclic group, and these groups optionally have a substituent. Substituents include halogen atoms, alkyl groups, aryl groups, heterocyclic groups, alkoxy groups, aryloxy groups, acyloxy groups, sulfonyloxy groups, alkylthio groups, arylthio groups, amino groups, anilino groups, acylamino groups, sulfonamido groups, A ureido group, urethane group, acyl group, alkoxycarbonyl group, carbamoyl group, sulfonyl group, sulfoxide group, sulfamoyl group, cyano group, or nitro group are preferred. R ₅ is more preferably an aryl group or a heterocyclic group, and an aryl group is particularly preferable. The heterocyclic group is preferably a 5- to 6-membered ring containing a nitrogen atom and / or a sulfur atom, and more preferably a 5- to 6-membered aromatic heterocyclic ring containing a nitrogen atom. The aryl group is preferably an electron-withdrawing substituent or an aryl group substituted with a sterically bulky substituent. The electron-withdrawing group may be a group having a high electron-withdrawing property with respect to a hydrogen atom, but preferably a halogen atom, an acyl group, an oxycarbonyl group, a carbamoyl group, a sulfonyl group, a sulfoxide group, an oxysulfonyl group, a sulfamoyl group, A cyano group, a nitro group, or a heterocyclic group is more preferably a halogen atom, an acyl group, an oxycarbonyl group, a carbamoyl group, a sulfonyl group, a sulfamoyl group, or a cyano group. It is preferable that at least one of the electron-withdrawing groups is substituted at the ortho position or the para position. The sterically bulky group may be any group that is bulkier than the methyl group, but is preferably an alkyl group having 2 or more carbon atoms, more preferably a secondary or tertiary alkyl group, and a tertiary alkyl group. Further preferred. The sterically bulky group is preferably substituted at at least one ortho position, and more preferably substituted at both ortho positions. An aryl group having both an electron-withdrawing group and a sterically bulky group is a particularly preferred group. R5 preferably has 30 or less carbon atoms, more preferably 20 or less, and still more preferably 16 or less.
The preferred molecular weight of the compound of the general formula (1) is in the range of 300 to 700, more preferably in the range of 300 to 600, still more preferably in the range of 350 to 550.

  Specific examples of the compound represented by the general formula (1) of the present invention are given below, but the present invention is not limited thereto.

  Other than the above, specific examples represented by the general formula (1) of the present invention include compounds D-1 to D-28 represented by the general formula (7) in JP-A-11-265044.

<Reducing agent addition method>
In the present invention, the reducing agent is preferably contained in the photothermographic material as a microcrystalline particle dispersion.

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.

  The photothermographic material of the invention has a reducing agent on the same surface as the photosensitive silver halide and the reducible silver salt on the support. The reducing agent of the present invention may be added in a wide range, preferably 0.01 mol to 100 mol, more preferably 0.1 mol to 10 mol, and still more preferably 0.1 mol to 1 mol of the coupler compound. It is 5 mol-3.0 mol.

(coupler)
Hereinafter, the coupler of the present invention will be described in detail.
The coupler of the present invention may have any structure as long as it is a compound capable of forming a dye having absorption in the visible region by coupling with an oxidized form of the reducing agent of the present invention. Such compounds are well known in color photographic systems, and typical examples thereof include pyrrolotriazole couplers, phenol couplers, naphthol couplers, pyrazolotriazole couplers, pyrazolone couplers, acylacetanilide couplers, and the like. Can be mentioned. In color photographic light-sensitive materials, it is necessary to fix a coupler in a photosensitive layer having a multilayer structure, and a coupler having a relatively large molecular weight in which a large oil-solubilizing group is added to the coupler skeleton has been used. In the present invention, the immobilization of the coupler is not so important, and a low molecular weight coupler is advantageous from the viewpoint of increasing the image density. In particular, when used in a solid dispersion state, the reaction efficiency is significantly hindered if a large oil-solubilizing group is attached. The substituent substituted on the mother nucleus is particularly preferably a smaller group as long as water solubility can be reduced.
Preferred couplers in the present invention are represented by the general formulas (C-1), (C-2), (C-3), (M-1), (M-2), (M-3), (Y-1), A coupler having a structure represented by (Y-2) or (Y-3).

In the formula, X ₁ represents a hydrogen atom or a leaving group, Y ₁ and Y ₂ represent an electron-withdrawing substituent, and R ₁ represents an alkyl group, an aryl group, or a heterocyclic group.

In the formula, X ₂ represents a hydrogen atom or a leaving group, R ₂ represents an acylamino group, a ureido group or a urethane group, R ₃ represents a hydrogen atom, an alkyl group or an acylamino group, and R ₄ represents a hydrogen atom or a substituent. Represents a group. R ₃ and R ₄ may be connected to each other to form a ring.

In the formula, X ₃ represents a hydrogen atom or a leaving group, R ₅ represents a carbamoyl group or a sulfamoyl group, and R ₆ represents a hydrogen atom or a substituent.

In the formula, X ₄ represents a hydrogen atom or a leaving group, R ₇ represents an alkyl group, an aryl group or a heterocyclic group, and R ₈ represents a substituent.

In the formula, X ₅ represents a hydrogen atom or a leaving group, R ₉ represents an alkyl group, an aryl group or a heterocyclic group, and R ₁₀ represents a substituent.

In the formula, X ₆ represents a hydrogen atom or a leaving group, R ₁₁ represents an alkyl group, an aryl group, an acylamino group or an anilino group, and R ₁₂ represents an alkyl group, an aryl group or a heterocyclic group.

In the formula, X ₇ represents a hydrogen atom or a leaving group, R ₁₃ represents an alkyl group, an aryl group, or an indoleenyl group, and R ₁₄ represents an aryl group or a heterocyclic group.

In the formula, X ₈ represents a hydrogen atom or a leaving group, Z represents a divalent group necessary for forming a 5- to 7-membered ring, and R ₁₅ represents an aryl group or a heterocyclic group.

In the formula, X ₉ represents a hydrogen atom or a leaving group, R ₁₆ , R ₁₇ and R ₁₈ each represent a substituent, n represents an integer of 0 to 4, and m represents an integer of 0 to 5. When n or m is 2 or more, the plurality of R ₁₆ and R ₁₇ may be the same group or different groups.

In General Formula (C-1), X ₁ represents a hydrogen atom or a leaving group, Y ₁ and Y ₂ represent an electron-withdrawing substituent, and R ₁ represents an alkyl group, an aryl group, or a heterocyclic group. These groups may have a substituent.
X ₁ is a hydrogen atom or a leaving group, preferably a hydrogen atom.
The leaving group referred to in the present invention means a group capable of leaving from the mother nucleus when it is coupled with an oxidant of a reducing agent to form a dye. Examples of the leaving group include halogen atoms, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, acyloxy groups, carbamoyloxy groups, imide groups, methylol groups, and heterocyclic groups. Y ₁ and Y ₂ represent an electron withdrawing group. Specific examples include a cyano group, a nitro group, an acyl group, an oxycarbonyl group, a carbamoyl group, a sulfonyl group, a sulfoxide group, an oxysulfonyl group, a sulfamoyl group, a heterocyclic group, a trifluoromethyl group, and a halogen atom. Among these, a cyano group, an oxycarbonyl group, and a sulfonyl group are preferable, and a cyano group and an oxycarbonyl group are more preferable. It is more preferable that either Y ₁ or Y ₂ is a cyano group, and it is particularly preferable that Y ₁ is a cyano group. Y ₂ is preferably an oxycarbonyl group, particularly preferably an oxycarbonyl group substituted with a bulky group (for example, 2,6-di-t-butyl-4-methylpiperazinyloxycarbonyl group). R ₁ is preferably an alkyl group or an aryl group, and these groups optionally have a substituent. The alkyl group is preferably a secondary or tertiary alkyl group, more preferably a tertiary alkyl group. As an alkyl group, it is preferable that the sum of carbon number is the range of 3-12, and it is more preferable that it is the range of 4-8. The aryl group is preferably a phenyl group and may have a substituent, but the sum of the carbon numbers is preferably in the range of 6 to 16, more preferably in the range of 6 to 12. The coupler of the general formula (C-1) preferably has a molecular weight of 700 or less, more preferably 650 or less, and even more preferably 600 or less.

In the general formula (C-2), X ₂ represents a hydrogen atom or a leaving group, R ₂ represents an acylamino group, a ureido group or a urethane group, R ₃ represents a hydrogen atom, an alkyl group or an acylamino group, R ₄ Represents a hydrogen atom or a substituent. R ₃ and R ₄ may be connected to each other to form a ring.
X ₂ is a hydrogen atom or a leaving group similar to X ₁ , and a hydrogen atom is more preferable. R ₂ is preferably an acylamino group or a ureido group. R ₂ preferably has a total carbon number of 2 to 12, more preferably 2 to 8. R ₃ is preferably an alkyl group having 1 to 4 carbon atoms or an acylamino group having 2 to 12 carbon atoms, more preferably an alkyl group having 2 to 4 carbon atoms or an acylamino group having 2 to 8 carbon atoms. R ₄ is preferably a halogen atom, an alkoxy group, an acylamino group or an alkyl group, more preferably a halogen atom or an acylamino group, and particularly preferably a chlorine atom. The coupler of the general formula (C-2) preferably has a molecular weight of 500 or less, more preferably 450 or less, and even more preferably 400 or less.
In the general formula (C-3), X ₃ is a hydrogen atom or a leaving group similar to X ₁ , but X ₃ is preferably a hydrogen atom. R ₅ is preferably an acyl group, an oxycarbonyl group, a carbamoyl group or a sulfamoyl group, more preferably a carbamoyl group or a sulfamoyl group. R ₅ is preferably a group having 1 to 12 carbon atoms, more preferably 2 to 10 carbon atoms. R ₆ is a hydrogen atom or a substituent, and the substituent is preferably an amide group, a sulfonamide group, a urethane group or a ureido group, more preferably an amide group or a urethane group. The substitution position is preferably the 5th or 8th position of the naphthol ring, and more preferably the 5th position. R ₆ is preferably a group having 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms. The coupler of the general formula (C-2) preferably has a molecular weight of 550 or less, more preferably 500 or less, and even more preferably 450 or less.

In formula (M-1), X ₄ is a hydrogen atom or a leaving group similar to X ₁ , but X ₄ is preferably a hydrogen atom. The heterocyclic group is preferably an azole group such as a pyrazole group, an imidazole group, a triazole group, a tetrazole group, a benzimidazole group, or a benzotriazole group, and more preferably a pyrazole group. R ₇ is an alkyl group, an aryl group or a heterocyclic group, and these groups optionally have a substituent. A secondary or tertiary alkyl group or an aryl group is preferred. The alkyl group is preferably a group having 2 to 14 carbon atoms, more preferably a group having 3 to 10 carbon atoms. The aryl group is preferably a group having 6 to 18 carbon atoms, more preferably a group having 6 to 14 carbon atoms. R ₈ is preferably an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, or a heterocyclic ring, and these groups optionally have a substituent. The alkyl group is preferably a secondary or tertiary alkyl group, more preferably a tertiary alkyl group. As an alkyl group, it is preferable that the sum of carbon number is the range of 3-12, and it is more preferable that it is the range of 4-8. The aryl group is preferably a phenyl group and may have a substituent, but the sum of the carbon numbers is preferably in the range of 6 to 16, more preferably in the range of 6 to 12. As an alkoxy group, a C1-C8 alkoxy group is preferable, More preferably, it is a C1-C4 alkoxy group. As the aryloxy group, an aryloxy group having 6 to 14 carbon atoms is preferable, and a group having 6 to 10 carbon atoms is more preferable. The alkylthio group and the arylthio group are preferably groups having the same carbon number as the alkoxy group and the aryloxy group, respectively. The coupler of general formula (M-1) preferably has a molecular weight of 600 or less, more preferably 550 or less, and even more preferably 500 or less. R ₁₁ represents an alkyl group, an aryl group, an acylamino group or an anilino group, R ₁₀ represents an alkyl group, an aryl group or a heterocyclic group.

The groups represented by X ₅ , R ₉ and R ₁₀ of the coupler of the general formula (M-2) are the same as the groups represented by X ₄ , R ₇ and R ₈ of the coupler of the general formula (M-1), respectively. The preferred range of each group is the same as that of the coupler of general formula (M-1).
In general formula (M-3), X ₆ is a hydrogen atom or a leaving group similar to X ₁ , but X ₆ is preferably a hydrogen atom. R ₁₁ is preferably an alkyl group, an aryl group, an acylamino group or an anilino group, more preferably an acylamino group or an anilino group. Most preferred is an anilino group. The alkyl group is preferably an alkyl group having 1 to 8 carbon atoms, and the aryl group is preferably an aryl group having 6 to 14 carbon atoms. The acylamino group is preferably a group having 2 to 14 carbon atoms, and more preferably a group having 2 to 10 carbon atoms. The anilino group is preferably a group having 6 to 16 carbon atoms, and more preferably a group having 6 to 12 carbon atoms. As the substituent of the anilino group, a halogen atom and an acylamino group are preferable. The coupler of general formula (M-3) preferably has a molecular weight of 700 or less, more preferably 650 or less, and even more preferably 600 or less.
In general formula (Y-1), X ₇ is a hydrogen atom or a leaving group similar to X ₁ , but X ₇ is preferably a hydrogen atom. R ₁₃ is preferably a secondary or tertiary alkyl group, an aryl group or a heterocyclic group. The alkyl group may be a cycloalkyl group or a bicycloalkyl group, and a tertiary alkyl group is more preferable. A 1-alkylcyclopropyl group, a bicycloalkyl group, and an adamantyl group are particularly preferable. R ₁₄ is an aryl group or a heterocyclic group, more preferably an aryl group. Of these, a phenyl group substituted with a halogen atom, an alkoxy group, an aryloxy group, an alkylthio group or an arylthio group at the 2-position is particularly preferred. The total carbon number of R ₁₄ is preferably in the range of 6 to 18, more preferably in the range of 7 to 16, and still more preferably in the range of 8 to 14. The coupler of general formula (Y-1) preferably has a molecular weight of 700 or less, more preferably 650 or less, and even more preferably 600 or less.

The groups represented by X ₈ and R ₁₅ of the coupler of general formula (Y-2) are the same groups as the groups represented by X ₇ and R ₁₄ of the coupler of general formula (Y-1), respectively. The preferred range of the group is the same as that of the coupler of the general formula (Y-1). Z represents a divalent group necessary for forming a 5- to 7-membered ring, and this ring may have a substituent, or another ring may be condensed.
Of the general formula (Y-2), a coupler represented by the general formula (Y-3) is preferable. In the coupler of the general formula (Y-3), X ₉ is synonymous with X _{7 in the} general formula (Y-1), and the preferred range is also the same. R ₁₆ is preferably a halogen atom, alkyl group, alkoxy group, acyl group, acyloxy group, acylamino group, alkoxycarbonyl group, sulfonamido group, cyano group, sulfonyl group, sulfamoyl group, carbamoyl group or alkylthio group, 4 is more preferable. n is preferably an integer of 0 to 3, more preferably 0 to 2, still more preferably 0 to 1, and most preferably 0. R ₁₇ is preferably the same group as R ₁₆ , more preferably a halogen atom, an alkyl group, an alkoxy group, an acylamino group, a sulfonamide group, an alkoxycarbonyl group, a sulfamoyl group or a sulfonyl group. In particular, it is more preferable that R ₁₇ which is a halogen atom, an alkoxy group or an alkylthio group is substituted in the ortho position with respect to the NH group. Most preferred is an alkylthio group. The coupler of general formula (Y-3) preferably has a molecular weight of 750 or less, more preferably 700 or less, and even more preferably 650 or less.
Specific examples of the coupler of the present invention are given below, but the present invention is not limited thereto.

  The coupler of the invention can be added as a solution dissolved in a suitable solvent such as methanol, as an emulsified dispersion emulsified and dispersed with a homogenizer or the like using a surfactant, an auxiliary solvent and a protective colloid, or as a solid dispersion. Among them, it is preferable to add to a light-sensitive emulsion layer (image forming layer) or a non-photosensitive layer adjacent to the image forming layer after being dispersed in solid fine particles.

  The dispersion of solid fine particles is obtained by mixing the powder particles into an aqueous solution containing a dispersant or a surfactant under stirring, and then using a bead mill, ball mill, colloid mill, vibrating ball mill, sand mill, jet mill, roller mill or ultrasonic. It can be produced by a dispersing method. Dispersing agents include water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide and gelatin, alkali metal salts such as alkylbenzene sulfonic acid, alkyl naphthalene sulfonic acid, sulfosuccinic acid, oleoyl-N-methyl taurine sulfonic acid, and ammonium salts. Nonionic surfactants such as anionic surfactants, alkylbenzene polyethoxylates, alkyl polyethoxylates, pluronics, alkyl glucoxylates, and the like are used. Among them, alkylthio-modified polyvinyl alcohol and polyvinylpyrrolidone are preferable as the water-soluble polymer, and dodecylbenzenesulfonate, triisopropylnaphthalenesulfonate, and alkyldiphenylether disulfonate are preferable as the anionic surfactant surfactant. It is particularly preferable to use the water-soluble polymer in combination with an anionic surfactant. Preservatives are preferably added for long-term storage of the dispersion, and isothiazolinone-based preservatives, particularly benzoisothiazolinone sodium salt. Moreover, it is preferable to use an antifoamer in order to prevent foaming at the time of dispersion, and acetylene alcohols are particularly preferable in terms of the antifoaming effect.

The average size of the solid fine particles is preferably in the range of 0.05 μm to 5 μm, more preferably in the range of 0.1 to 2 μm, still more preferably in the range of 0.2 to 1 μm. When the particle size is too large, problems such as filtration clogging and deterioration of the coated surface state are caused, and when the particle size is too small, the stability of the dispersion is impaired. From these problems, it is preferable to set the average size within the above range, and it is preferable to keep the particle size distribution low.
In order for the solid particulate compound to function efficiently during thermal development, the coupler of the present invention preferably has a melting point of 220 ° C. or lower, more preferably 200 ° C. or lower, and even more preferably 180 ° C. or lower. The coupler of the present invention preferably has a melting point of 70 ° C. or higher, more preferably 90 ° C. or higher, and further preferably 110 ° C. or higher in order to keep the storage stability of the unused photothermographic material good. In order to improve the long-term storability of the photosensitive material after heat development, the coupler of the present invention preferably has a melting point of 100 ° C. or higher, more preferably 120 ° C. or higher, more preferably 140 ° C. or higher. . In order to improve the stability of the fine particle solid dispersion, the solubility of the coupler of the present invention in water is preferably 1000 ppm or less, more preferably 200 ppm or less, and even more preferably 50 ppm or less. When a dispersant or a surfactant is contained, the solubility of the coupler in the solution containing these is preferably in the above range.

Couplers of the present invention can be used in a range of ^{0.1mmol / m 2 ~5.0mmol / m 2} , preferably in the range of ^{0.2mmol / m 2 ~3.0mmol / m 2} , more preferably 0.5 mmol / m It is to be used in the range of ^{2 to} 2.0 mmol / m ² . The coupler of the present invention is selected from one selected from general formulas (C-1), (C-2), and (C-3), (M-1), (M-2), and (M-3). It is preferable to use 2 or more types in combination of 1 type selected from (1), (Y-1), (Y-2), and (Y-3), and it is more preferable to use 3 types in combination. Formula (C-1), is preferably in a range amount used of 0.05mmol / m ² ~2.0mmol / m ² of coupler selected from (C-2), and (C-3), more preferably in the range of 0.1 to 1.0, more preferably in the range of ^{0.15mmol / m 2 ~0.6mmol / m 2} . The amount of the coupler selected from the general formulas (M-1), (M-2), and (M-3) is preferably in the range of 0.1 mmol / m ^{2 to} 2.0 mmol / m ² , more preferably in the range of 0.15 to 1.5, more preferably in the range of ^{0.2mmol / m 2 ~0.8mmol / m 2} . Formula (Y-1), preferably in the range of (Y-2), and the amount of the coupler selected from (Y-3) is ^{0.2mmol / m 2 ~4.0mmol / m 2} , more preferably in the range of 0.3 to 3.0, more preferably in the range of ^{0.4mmol / m 2 ~2.0mmol / m 2} .

(Non-photosensitive organic silver salt)
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 setting the silver stearate content to 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 silver stearate 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 5 or less 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 in which the ratio of the long axis to the single axis exceeds 5. 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% relative to 1 mol of the organic acid silver salt in the liquid. The following is more preferable, and positive addition of photosensitive silver salt is not performed.

  In the present invention, it is possible to prepare an organic silver salt aqueous dispersion and a photosensitive silver salt aqueous dispersion, respectively, and mix them later to produce a photothermographic material. Further, mixing two or more organic silver salt aqueous dispersions or two or more photosensitive silver salt aqueous dispersions is a method preferably used for adjusting photographic characteristics.

  The organic silver salt is prepared by forming particles in an aqueous solvent and then dispersing in a solvent such as methyl ethyl ketone (MEK). Drying is preferably performed at an oxygen partial pressure of 15% by volume or less, more preferably 15% by volume or less and 0.01% by volume or more in an airflow type flash jet dryer, and 10% by volume or less and 0.01% by volume or more. More preferably.

4) Addition Amount organic silver salt in the invention can be used in a desired amount, preferably 0.05g / m ² ~3.0g / m ² as the total amount of coated silver halide silver was also included, and more preferably 0 ^{.1g / m 2 ~1.8g / m 2} , more preferably from ^{0.2g / m 2 ~1.2g / m 2} .

(Auxiliary reducing agent)
In the photothermographic material of the invention, an auxiliary reducing agent is preferably used together with the above-mentioned reducing agent. The auxiliary reducing agent in the present invention 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 auxiliary 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 an —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.
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, and the substituent of the alkyl group is not particularly limited, but is preferably an aryl group, a hydroxy group, Examples include alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, acylamino groups, sulfonamido groups, sulfonyl groups, phosphoryl groups, acyl groups, carbamoyl groups, ester groups, ureido groups, urethane groups, and halogen atoms.

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 capable of substituting for a benzene ring, and X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group capable of substituting for 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. 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 , such as a halogen atom, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an acylamino group, a sulfonamide group, a sulfonyl group, a phosphoryl group, an 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 color 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.

  Specific examples of the auxiliary reducing agent including the compound represented by the general formula (R) of the present invention are shown below, but the present invention is not limited thereto.

The addition amount of the auxiliary reducing agent is preferably a ^{0.1g / m 2 ~3.0g / m 2} , more preferably ^{0.2g / m 2 ~1.5g / m 2} , more preferably is the ^{0.3g / m 2 ~1.0g / m 2} . It is preferably contained in an amount of 5 mol% to 50 mol%, more preferably 8 mol% to 30 mol%, and more preferably 10 mol% to 20 mol%, based on 1 mol of silver on the surface having the image forming layer. More preferably. The auxiliary reducing agent is preferably contained in the image forming layer.

(Photosensitive 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. The hexacyano metal complexes 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⁻ , [Re (CN) ₆ ] ^{3− and the} like. . 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 halide emulsion desalting method and a chemical sensitization method that can be contained in the silver halide grains used in the present invention, JP-A-11-11 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, page 38 to line 20, page 35 of European Patent Publication No. 0803764A1, JP 2001-272747, JP 2001-290238, JP 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 the sensitivity and the fogging performance, but is preferably 10 ⁻⁶ mol to 1 mol per mol of silver halide in the image forming layer. The amount is preferably 10 ^-4 mol to 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 the compound preferably used in the sulfur sensitization method, selenium sensitization method, and tellurium sensitization method, known compounds such as 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 gold sensitization alone or in combination with the chalcogen sensitization described above. As the gold sensitizer, the valence of gold 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 auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, or pyridyltrichloro. Gold or the like is preferable. Further, gold sensitizers described in US Pat. No. 5,858,637 and JP-A 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 to 10 ⁻³ mol 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 is 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 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 together with the nitrogen atom and the 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. _R113 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 the 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 that 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 general formula (9), R ₃₂ , R ₃₃ , or Z ₃ has the same meaning as in 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 reacts with a one-electron oxidant formed by one-electron oxidation of RED ₆ to form a new bond, a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site, or Reactive group containing a non-aromatic heterocyclic moiety of a benzo-fused ring. Q represents a linking group linking 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 the 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 that 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 the general formula (11), R ₃₂ , R ₃₃ , Z ₃ and Z ₄ have the same meanings as those in the 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, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group, etc.) or imino silver (> NAg) And a nitrogen-containing heterocyclic group having a —NH— group as a heterocyclic partial structure (for example, a benzotriazole group, a benzimidazole group, an indazole group, etc.). 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 ⁻ , Ph ₄ B ^{− and the} like. Can be mentioned. When a group having a negative charge in the 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 addition timing 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 the 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 (Rd).

Formula (Rd) A- (W) n-B
In the formula (Rd), A represents a group that can be adsorbed 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 (Rd), the adsorptive group represented by A is a group that directly adsorbs to silver halide or a group that promotes adsorption to silver halide. 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 is a cation such as alkali metal, alkaline earth metal, or heavy metal (such as Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ag ⁺ , or Zn ²⁺ ), ammonium Examples thereof include an ion, 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 adsorptive group 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 an 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 having a heterocyclic ring, or a "-S-" group, a "-Se-" group, a "-Te-" group or a "= N-" group capable of coordinating 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, oxadiazo Group, a triazine 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 adsorbing group include all groups having a partial structure of “—S—” or “—S—S—”.

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 include those described in the specifications p4 to p7 of JP-A No. 11-95355.

  In the formula (Rd), 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 an —NH— group that can form imino silver (> NAg) as a partial structure of the heterocyclic ring (for example, ben Triazole 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 (Rd), 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 (such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, or a hexamethylene group), an alkenylene group having 2 to 20 carbon atoms, and an alkynylene having 2 to 20 carbon atoms. Group, an arylene group having 6 to 20 carbon atoms (eg, phenylene group, naphthylene group, etc.), —CO—, —SO ₂ —, —O—, —S—, —NR ₁ —, a combination of these linking groups, and the like. can give.
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 the formula (Rd), 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, Aminophenols, sulfonamidophenols, and hydroquinones, catechols, resorcinols, benzenetriols, polyphenols such as bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. Removed one Group, and the like. Of course, these may have an arbitrary substituent.

  In the formula (Rd), the reducing group represented by B indicates 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 measurement method described in (Vol. 9, pages 282 to 344, Maruzen). For example, by rotating disk voltammetry, specifically, a sample is dissolved in a solution of methanol: pH 6.5, Briton-Robinson buffer (Britton-Robinson buffer) = 10%: 90% (volume%), and nitrogen is added for 10 minutes. After aeration of gas, a rotating disc electrode (RDE) made of glassy carbon 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. It can be measured at the sweep speed. A half-wave potential (E1 / 2) can be obtained from the obtained voltammogram.

  The reducing group represented by B of the present invention preferably has an oxidation potential in the range of about -0.3 V to about 1.0 V when measured by the above-described 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 (Rd), 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 (Rd) of 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 (Rd) of the present invention may be a bis form or a tris form. The molecular weight of the compound of formula (I) of the present invention is preferably between 100 and 10,000, more preferably between 120 and 1000, particularly preferably between 150 and 500.

  Examples of the compound of the formula (Rd) of 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 of the present invention.

  The compounds of the present invention can be easily synthesized according to known methods. As the compound of the formula (Rd) of 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 the formula (Rd) of the present invention is preferably added to the silver halide emulsion layer (image forming layer), and more preferably added during 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 to 1 mol of photosensitive silver halide. 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁴ mol to 1 × 10 ⁻¹ mol.

  The compound of the formula (Rd) of 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) Coating 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 coating silver amount 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 respectively were stirred at high speed. Organic silver salt is prepared by mixing with a machine, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc. Although there is a method of preparation, 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 dispersions and two or more photosensitive silver halide 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).

(Description of development accelerator)
In the photothermographic material of the present invention, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, or the like as a development accelerator, Hindered phenol compounds represented by general formula (II) described in JP-A-2001-92075, general formula (I) described in JP-A-10-62895, JP-A-11-15116, and the like, A hydrazine-based compound represented by general formula (D) of JP-A No. 2002-156727 or general formula (1) described in JP-A No. 2002-278017, and described in JP-A No. 2001-264929 A phenolic or naphtholic compound represented by the general formula (2) is preferably used. These development accelerators are used in the range of 0.1 mol% to 20 mol% with respect to the reducing agent, preferably in the range of 0.5 mol% to 10 mol%, more preferably 1 mol% to 5 mol. % Range. 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 and a low-boiling auxiliary solvent that are solid at room temperature, 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 development accelerators described above, hydrazine compounds represented by the general formula (D) described in JP-A No. 2002-156727 and those described in JP-A No. 2001-264929 A phenol-based or naphthol-based compound represented by the formula (2) is more preferable.

Particularly preferred development accelerators of the present invention are compounds represented by the following general formulas (A-1) and (A-2).
Formula (A-1)
Q ₁ -NHNH-Q ₂
(Wherein 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 Butylphenyl) 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, such as 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 More preferred are rings in which the ring is 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 a nitrogen atom.

In the 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 a chlorine atom or a bromine atom), an alkoxy group (such as a methoxy group, a butoxy group, an n-hexyloxy group, an n-decyloxy group, a cyclohexyloxy group, or a benzyloxy 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, 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, a naphthalene ring is particularly preferable as the condensed 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-based 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 of 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 bisphenols described above, 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, examples of the substituent include a halogen atom, an alkyl group, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamide group, an 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, and a t-octyl group. Group, phenyl group, 4-alkoxyphenyl group, 4-acyloxyphenyl group and the like.

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. In view 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. In addition, 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) of the present invention can be used in a photothermographic material after being incorporated into a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersed fine particle dispersion, in the same manner as the reducing agent. The compound of the present invention forms 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) of the present invention, It can be isolated in the crystalline state.

  The compound of the general formula (D) of 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%, still more preferably relative to the reducing agent. It is in the range of 20 mol% to 100 mol%.

(Description of binder)
The polyvinyl acetal in the present invention is preferably a compound represented by the following general formula (VA).

In the formula, R represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or an aryl group. X is 10 mol% to 50 mol%, Y is 0 mol% to 10 mol%, and Z is 50 mol% to 90 mol%. The alkyl group, cycloalkyl group, and aryl group may have a substituent.
Preferably, X is 20 mol% to 40 mol%, Y is 0 mol% to 5 mol%, and Z is 60 mol% to 80 mol%.
Specifically, R includes, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a cyclohexyl group, and a phenyl group.
Containing.
The average degree of polymerization of polyvinyl alcohol which is a raw material for producing polyvinyl acetal in the present invention is preferably 500 to 3000.

  The polyvinyl acetal used in the present invention is synthesized by an acetalization reaction between polyvinyl alcohol and various aldehydes, and is preferably acetalized with butyraldehyde and / or acetaldehyde. In particular, the proportion of the acetalized portion of the acetalized portion of polyvinyl acetal is preferably in the range of 30% by mass to 100% by mass, more preferably 50% by mass with respect to the total acetalized portion. % To 100% by mass. When the portion acetalized by acetaldehyde is less than 30% by mass, the glass transition point of the obtained polyvinyl acetal resin is 80 ° C. or less, the nucleation of the organic silver salt proceeds excessively, and the dispersibility of the silver salt is also preferable. And the resolution and definition of the image may be inferior.

  Specific examples of the polyvinyl acetal used in the present invention are shown below.

<R: butyl group>
・ Z / X / Y = 68/30/2 (Mw: about 100,000, Tg = 68 ° C.)
・ 66/30/4 (Mw: approx. 100,000, Tg = 66 ° C.)
69/30/1 (Mw: approx. 100,000, Tg = 69 ° C.)
・ 66/26/8 (Mw: approx. 100,000, Tg = 65 ° C.)
74/24/2 (Mw: approx. 100,000, Tg = 71 ° C.)
79/19/2 (Mw: approx. 100,000, Tg = 73 ° C.)
・ 64/34/2 (Mw: approx. 100,000, Tg = 75 ° C.)
・ 68/30/2 (Mw: about 30,000, Tg = 66 ° C.)
・ 68/30/2 (Mw: approx. 60,000, Tg = 67 ° C.)
・ 68/30/2 (Mw: about 150,000, Tg = 70 ° C.)
<R: methyl group>
・ Z / X / Y = 61/37/2 (Mw: about 100,000, Tg = 78 ° C.)

For the polyvinyl acetal in the present invention, various commercially available brands can be selected, and these can be used alone or in combination with a plurality of types to prepare preferable characteristics.
Commercially available registered brands include Butor Bars B-72, B-76, B-79, and B-98 of Sorcia, Inc., Denkabutyral # 3000-1, # 3000-2, # of Electrochemical Industry Co., Ltd., # 3000-4, # 3000-K, and # 4000-2, Sleksui BL-1, BL-2, BL-2H, BL-5, BL-10, BM-2, BM-5 from Sekisui Chemical Co., Ltd. Examples include BM-S, BM-SH, BH-3, BH-6, BH-A, BX-3 (polyvinyl acetal), and BX-L (polyvinyl acetal).

  In the present invention, other natural or synthetic polymers may be used in combination with polyvinyl butyral. For example, any of gelatin, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, cellulose acetate, polyolefin, polyester, polystyrene, polyacrylonitrile, polycarbonate, butylethylcellulose, methacrylate copolymer, maleic anhydride ester copolymer, polystyrene and butadiene-styrene copolymer, etc. Things can be used. In the present invention, it is preferable to use 50% by mass or more of polyvinyl butyral with respect to the total composition of the binder in the image forming layer. Of course, copolymers and terpolymers are also included. The preferable total amount of polyvinyl butyral is 50% by mass or more and 100% by mass or less, and more preferably 70% by mass or more and 100% by mass or less, based on the total composition of the binder in the image forming layer. The Tg of the binder is preferably in the range of 40 ° C to 90 ° C, more preferably 50 ° C to 80 ° C. Here, Tg is a glass transition temperature.

  The total amount of the binder is used, for example, in an amount sufficient to keep the components of the image forming layer in the layer. That is, it is used in an effective range to function as a binder. The effective range can be appropriately determined by those skilled in the art. As a guide when at least the organic silver salt is retained, the ratio of the binder to the organic silver salt is preferably in the range of 15: 1 to 1: 3, particularly 8: 1 to 1: 2 in terms of mass ratio.

  The total binder / silver halide mass ratio is in the range of 400-5, more preferably 200-10.

The total binder amount of the image forming layer of the present invention is preferably 0.2 g / m ^{2 to} 30 g / m ² , more preferably 1 g / m ^{2 to} 15 g / m ² , and still more preferably 2 g / m ^{2 to} 10 g / m ^2. Range. The image forming layer of the present invention may contain a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like.

(Anti-fogging agent)
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 of 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 the 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 electron withdrawing groups include halogen atoms, alkyl groups substituted with electron withdrawing groups, aryl groups substituted with electron withdrawing groups, heterocyclic groups, alkyl or arylsulfonyl groups, 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 of the general formula (H) of 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. No. 6,506,548, JP-A-50-137126, 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 the general formula (H) of the present invention is preferably used in the range of 10 ⁻⁴ mol to 1 mol, more preferably 10 ⁻³ mol, per mol of the non-photosensitive silver salt in the image forming layer. It is preferable to use in the range of ˜0.5 mol, more preferably in the range of 1 × 10 ⁻² mol to 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.

2) Other antifoggants Other antifoggants include mercury (II) salts described in paragraph No. 0113 of JP-A No. 11-65021, benzoic acids of paragraph No. 0114 of the same, salicylic acid derivatives disclosed in 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 added layer is preferably added to the layer having the image forming layer, and more preferably added to the organic silver salt-containing layer. The azolium salt may be added at any step in the coating solution preparation. When added to the organic silver salt-containing layer, any step from the preparation of the organic silver salt to the coating solution preparation may be performed. To immediately before coating. 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 it is preferably 1 × 10 ⁻⁶ mol or more and 2 mol or less, more preferably 1 × 10 ⁻³ mol or more and 0.5 mol or less per 1 mol of silver.

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used to control development by suppressing or accelerating development, to improve spectral sensitization efficiency, and to improve 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-2002-303955, JP-A-2002-303951, and the like are preferable.

2) Toning agent In the photothermographic material of the invention, it is preferable to add a toning agent. For the toning agent, paragraph numbers 0054 to 0055 of JP-A-10-62899, page 21 to 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) Phthalazines (phthalazine, phthalazine derivatives or metal salts; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxy Phthalazine and 2,3-dihydrophthalazine); a combination of phthalazines and phthalic acids is preferred, and a combination of phthalazines and phthalic acids is particularly preferred. Among them, a particularly preferable combination is a combination of 6-isopropylphthalazine and phthalic acid or 4-methylphthalic acid.

3) Plasticizers and lubricants The plasticizers and lubricants that can be used in the image forming layer of the invention are described in paragraph No. 0117 of JP-A No. 11-65021. The slip agent is described in JP-A No. 11-84573, paragraph numbers 0061 to 0064 and Japanese Patent Application No. 11-106881, paragraph numbers 0049 to 0062.

4) Dye, Pigment In the image-forming layer of the present invention, in addition to the phthalocyanine compound, various dyes and pigments (for example, CI Pigment Blue) are used from the viewpoints of color tone improvement, prevention of interference fringe generation during laser exposure, and prevention of irradiation. 60, C.I. Pigment Blue 64, C.I. Pigment Blue 15: 6). 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 and its addition method and addition amount, paragraphs No. 0118 of JP-A No. 11-65021, paragraph Nos. 0136 to 0193 of JP-A No. 11-223898, and formulas (H of JP-A No. 2000-284399) ), Formulas (1) to (3), compounds of formulas (A) and (B), compounds of general formulas (III) to (V) described in Japanese Patent Application No. 11-91652 (specific compounds: 21 to 24) and the nucleation promoter are 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 preferable to contain 5 mmol or less, more preferably 1 mmol or less, per mol of silver on the side having the image forming layer containing photosensitive silver halide.
When a nucleating agent is used in the photothermographic material of the 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 is 0.1 mg / m ² ˜500 mg / m ² is preferable, and 0.5 mg / m ^{2 to} 100 mg / m ² is more preferable.

6) Benzoic acids The photothermographic material of the invention may contain benzoic acids for the purpose of increasing sensitivity and preventing fogging. Although any benzoic acid derivative can be used as the benzoic acid, examples of preferred structures include U.S. Pat. Nos. 4,784,939, 4,152,160, and JP-A-9-281687. And the compounds described in JP-A-9-329864, JP-A-9-329865, and the like. The benzoic acids used in the present invention 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 added to the organic silver salt-containing layer. Is more preferable. The benzoic acid may be added at any step in the coating solution preparation, and when added to the organic silver salt-containing layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be performed. To immediately before coating. The benzoic acid may be added by any method such as powder, solution, or 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. The amount of benzoic acid added may be any amount, but is preferably 1 μmol or more and 2 mol or less, and more preferably 1 mmol or more and 0.5 mol or less, per 1 mol of silver.

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution of the present 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 image forming layer of the present invention is composed of one or more layers on a support. In the case of a single layer, it consists of an organic silver salt, a photosensitive silver halide, a reducing agent and a binder, and optionally contains additional materials such as toning agents, coating aids and other auxiliary agents. In the case of two or more layers, an organic silver salt and a light-sensitive silver halide are contained in the first image forming layer (usually a layer adjacent to the support), and some in the second image forming layer or both layers. Other components may be included.

  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), (b) between the plurality of image forming layers and between the image forming layer and the protective layer. It can be classified into an intermediate layer provided therebetween, (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 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 on the photothermographic material as the layer (c) or (d).

1) Surface protective layer The photothermographic material according to the invention may be provided with a surface protective layer for the purpose of preventing adhesion of the image forming layer. The surface protective layer may be a single layer or a plurality of layers.
The surface protective layer is described in JP-A No. 11-65021, paragraph numbers 0119 to 0120 and JP-A No. 2000-171936.
As the binder for the surface protective layer of the present invention, gelatin is preferable, but it is also preferable to use polyvinyl alcohol (PVA) or a combination thereof. As gelatin, inert gelatin (for example, Nitta gelatin 750), phthalated gelatin (for example, Nitta gelatin 801), and the like can be used. Examples of PVA include those described in paragraph Nos. 0009 to 0020 of JP-A No. 2000-171936. Completely saponified PVA-105, partially saponified PVA-205, PVA-335, and modified polyvinyl alcohol MP- Preferred is 203 (trade name, manufactured by Kuraray Co., Ltd.). Preferably 0.3g / m ² ~4.0g / m ² as a polyvinyl alcohol coating amount (per support 1 m ²⁾ of the protective layer (per one ^{layer), 0.3g / m 2 ~2.0g /} m 2 Is more preferable.

All (including water-soluble polymer and latex polymer) binder preferably 0.3g / m ² ~5.0g / m ² as a coating amount (per support 1 m ²⁾ of the surface protective layer (per one layer), 0. 3g / m ² ~2.0g / m ² is more preferable.

2) Antihalation layer In the photothermographic material of the invention, the antihalation layer can be provided on the side farther from the light source than the image forming layer. Preferably, it is a layer between the back layer or the image forming layer and the support.

As for the antihalation layer, paragraphs 0123 to 0124 of JP-A-11-65021, JP-A-11-223898, 9-230531, 10-36695, 10-104779, 11-231457, 11 -352625, 11-352626 and the like.
The antihalation layer contains an antihalation dye having absorption at the exposure wavelength. When the exposure wavelength is in the infrared region, an infrared absorbing dye may be used, and in that case, a dye having no absorption in the visible region is preferable.
In the photothermographic material of the invention, the metal phthalocyanine dye is preferably used as an antihalation dye.

The amount of the dye added is generally such that the optical density (absorbance) exceeds 0.1 when measured at the target wavelength. The optical density is preferably 0.15 to 2, and more preferably 0.2 to 1. The amount of the dye for obtaining such an optical density is generally 0.001g / m ² ~1g / m ² approximately.

3) Back Layer Back layers that can be applied to the present invention are described in paragraph Nos. 0128 to 0130 of JP-A No. 11-65021.
The photothermographic material of the invention is preferably a layer containing the metal phthalocyanine compound as an antihalation layer.

In the present invention, a colorant having an absorption maximum at 300 nm to 450 nm can be added for the purpose of improving the silver tone and the temporal change of the image. Such colorants are disclosed in JP-A-62-210458, JP-A-63-104046, JP-A-63-103235, JP-A-63-208846, JP-A-63-306436, JP-A-63-141435, and JP-A-01-61745. No. 1, Japanese Patent Laid-Open No. 2001-100363, and the like.
Such a colorant is usually added in the range of 0.1 mg / m ^{2 to 1} g / m ² , and the back layer provided on the opposite side of the image forming layer is preferable as the layer to be added.

4) 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. Matting agent case shown in the coating amount per photothermographic material 1 m ^2, preferably from ^{1mg / m 2 ~400mg / m 2} , more preferably ^{5mg / m 2 ~300mg / m 2} .

  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 average particle size is preferably 0.5 μm to 10 μm, more preferably 1.0 μm to 8.0 μm, and still more preferably 2.0 μm to 6.0 μm. The variation coefficient of the size distribution is preferably 50% or less, more preferably 40% or less, and still more preferably 30% or less. Here, the coefficient of variation is a value represented by (standard deviation of particle size) / (average value of particle size) × 100. It is also preferable to use two types of matting agents having a small variation coefficient and having an average particle size ratio larger than 3.

  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 obtained 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 the outermost surface layer, the layer functioning as the outermost surface layer of the photothermographic material, or a layer close to the outer surface, and also contained in a layer acting as a so-called protective layer. It is preferred that

5) Polymer Latex When the photothermographic material of the present invention is used for printing applications in which dimensional change is a problem, it is preferable to use a polymer latex for the surface protective layer or the back layer. For such polymer latex, “Synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki, published by Kobunshi Publishing (1978))”, “Application of synthetic latex (Takaaki Sugimura, Ikuo Kataoka, Junichi Suzuki, Keiji Kasahara, Takashi "Molecular Publications (1993))" and "Synthetic Latex Chemistry (Muroichi Muroi, published by High Polymers Publication (1970))", specifically, methyl methacrylate (33.5% by mass) / Ethyl acrylate (50 wt%) / Methacrylic acid (16.5 wt%) copolymer latex, Methyl methacrylate (47.5 wt%) / Butadiene (47.5 wt%) / Itaconic acid (5 wt%) copolymer Latex, latex of ethyl acrylate / methacrylic acid copolymer, methyl methacrylate (58.9% by mass) / 2-ethyl Latex of xyl acrylate (25.4 mass%) / styrene (8.6 mass%) / 2-hydroxyethyl methacrylate (5.1 mass%) / acrylic acid (2.0 mass%) copolymer, methyl methacrylate (64. 0 mass%) / styrene (9.0 mass%) / butyl acrylate (20.0 mass%) / 2-hydroxyethyl methacrylate (5.0 mass%) / acrylic acid (2.0 mass%) copolymer latex, etc. Is mentioned.

  Furthermore, as a binder for the surface protective layer, a combination of polymer latex described in Japanese Patent Application No. 11-6872 and a technique described in Paragraph Nos. 0021 to 0025 of Japanese Patent Application Laid-Open No. 2000-267226, Japanese Patent Application No. 11-6872 The technology described in paragraph numbers 0027 to 0028 of the specification and the technology described in paragraph numbers 0023 to 0041 of JP 2000-19678 may be applied. The ratio of the polymer latex in the surface protective layer is preferably 10% by mass or more and 90% by mass or less, and particularly preferably 20% by mass or more and 80% by mass or less of the total binder.

6) Membrane pH
The photothermographic material of the present invention preferably has a film surface pH of 7.0 or less, more preferably 6.6 or less before heat development. The lower limit is not particularly limited, but is about 3. The most preferred pH range is in the range of 4 to 6.2. The film surface pH is preferably adjusted using an organic acid such as a phthalic acid derivative, a non-volatile acid such as sulfuric acid, or a volatile base such as ammonia from the viewpoint of reducing the film surface pH. In particular, ammonia is volatile and is preferable for achieving a low film surface pH because it can be removed before the coating process or heat development.
In addition, it is also preferable to use ammonia in combination with a nonvolatile base such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. A method for measuring the film surface pH is described in paragraph No. 0123 of JP-A No. 2000-284399.

7) Hardener A hardener may be used for each layer such as the image forming layer, protective layer, and back layer of the present invention. Examples of hardeners include T.W. H. There are various methods described in "THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION" by James (published by Macmillan Publishing Co., Inc., published in 1977), pages 77 to 87, Chrome Alum, 2,4-dichloro-6 In addition to hydroxy-s-triazine sodium salt, N, N-ethylenebis (vinylsulfoneacetamide), N, N-propylenebis (vinylsulfoneacetamide), polyvalent metal ions described on page 78 of the same document, US Pat. No. 4,281 , 060, and JP-A-6-208193, epoxy compounds such as US Pat. No. 4,791,042, and vinylsulfone compounds such as JP-A-62-289048 are preferably used.

  The hardening agent is added as a solution, and the addition time of this solution into the protective layer coating solution is from 180 minutes before to immediately before application, preferably from 60 minutes to 10 seconds before application. As long as the effects of the present invention are sufficiently exhibited, there is no particular limitation. 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, and N.I. Harnby, M.M. F. Edwards, A.D. W. There is a method using a static mixer described in Chapter 8 of Nienow's “Liquid Mixing Technology” (Nikkan Kogyo Shimbun, 1989), translated by Koji Takahashi.

8) Surfactant As for the surfactant applicable to the present invention, paragraph No. 0132 of JP-A No. 11-65021, paragraph No. 0133 of the solvent, paragraph No. 0134 of the support, antistatic or conductive layer Paragraph No. 0135 for the method of obtaining a color image, paragraph No. 0136 for JP-A No. 11-84573 and paragraph Nos. 0049 to 0062 of Japanese Patent Application No. 11-106881 for the slip agent. Has been.

  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. In addition, a polymeric fluorine-based surfactant described in JP-A-9-281636 is also preferably used. In the photothermographic material of the present invention, it is preferable to use fluorine-based surfactants described in JP-A Nos. 2002-82411, 2003-57780, and 2001-264110. In particular, the fluorosurfactants described in JP-A-2003-57780 and JP-A-2001-264110 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 fluorine-based surfactant described in JP-A No. 2001-264110 is most preferable because it has a high charge adjusting ability and requires a small amount of use.

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.

9) Antistatic agent In this invention, it is preferable to have a conductive layer containing a metal oxide or a conductive polymer. The antistatic layer may serve as an undercoat layer, a back layer surface protective layer, or the like, or may be provided separately. As the conductive material for the antistatic layer, a metal oxide in which conductivity is improved by introducing oxygen defects and different metal atoms into the metal oxide is preferably used. Examples of metal oxides include ZnO, TiO ₂ and SnO _2. Addition of Al and In to ZnO, addition of Sb, Nb, P and halogen elements to SnO ₂ , and addition to TiO ₂ For example, addition of Nb, Ta or the like is preferable.
In particular, SnO ₂ added with Sb is preferable. The amount of different atoms added is preferably in the range of 0.01 mol% to 30 mol%, more preferably in the range of 0.1 mol% to 10 mol%. The shape of the metal oxide may be spherical, acicular, or plate-like, but in terms of the effect of imparting conductivity, acicular particles having a major axis / uniaxial ratio of 2.0 or more, preferably 3.0 to 50 are used. Good. Range amount preferably of 1mg / m ² ~1000mg / m ² of metal oxide, more preferably 10mg / m ² ~500mg / m ² range, more preferably at 20mg / m ² ~200mg / m ² It is a range.

The antistatic layer of the present invention may be disposed on either the image forming layer surface side or the back surface side, but is preferably disposed between the support and the back layer.
Specific examples of the antistatic layer of the present invention include paragraph No. 0135 of JP-A No. 11-65021, JP-A Nos. 56-143430, 56-143431, 58-62646, No. 56-120519, JP-A No. 11-120. No. 84573, paragraph numbers 0040 to 0051, US Pat. No. 5,575,957, and JP-A No. 11-223898, paragraph numbers 0078 to 0084.

10) Coating solvent Examples of the solvent used for coating the photothermographic material of the present invention include New Edition Solvent Pocket Book (Ohm, published in 1994), but the present invention is not limited thereto. The boiling point of the solvent used in the present invention is preferably 40 ° C. or higher and 180 ° C. or lower. Specific examples of the solvent include hexane, cyclohexane, toluene, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, ethyl acetate, 1,1,1-trichloroethane, tetrahydrofuran, triethylamine, thiophene, trifluoroethanol, perfluoropentane, Xylene, n-butanol, phenol, methyl isobutyl ketone, cyclohexanone, butyl acetate, diethyl carbonate, chlorobenzene, dibutyl ether, anisole, ethylene glycol diethyl ether, N, N-dimethylformamide, morpholine, perfluorotributylamine, and water Can be mentioned. Among these, methyl ethyl ketone is preferably used because it has an appropriate boiling point, a uniform surface shape of the coating film is obtained, the drying load is light, and the residual amount of the solvent can be reduced.

  It is preferable to reduce the amount of the solvent used for coating remaining in the film after coating and drying. Residual solvents generally cause development photosensitive materials to volatilize in the environment during exposure or heat development, making them uncomfortable, and are undesirable for health.

In addition, the residual solvent may affect photographic performance and storage stability, and it is preferable to keep the residual solvent amount within a certain range in a small region. If the amount of residual solvent is large, high sensitivity can be obtained immediately after the production of the photothermographic material, but fog increases during storage and sensitivity decreases. In the photothermographic material of the present invention, the residual solvent amount is preferably in an amount of ^{MEK 0.1mg / m 2 ~150mg / m} 2, more preferably ^{0.1mg / m 2 ~80mg / m 2} , more preferably it is ^{0.1mg / m 2 ~40mg / m 2} .

11) Support The transparent support is subjected to heat treatment in a temperature range of 130 ° C to 185 ° C in order to alleviate internal strain remaining in the film during biaxial stretching and to eliminate heat shrinkage strain generated during heat development processing. Polyester, especially polyethylene terephthalate, is preferably used. In the case of a photothermographic material for medical use, the transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored. Examples of the support include water-soluble polyesters disclosed in JP-A-11-84574, styrene-butadiene copolymers described in JP-A-10-186565, and vinylidene chloride described in JP-A-2000-39684 and Japanese Patent Application No. 11-106881, paragraph numbers 0063 to 0080. It is preferable to apply an undercoating technique such as a copolymer. When the image forming layer or the back layer is applied to the support, the water content of the support is preferably 0.5% by mass or less.

12) Other additives The photothermographic material may further contain an antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber or a coating aid. Various additives are added to either the image forming layer or the non-photosensitive layer. Regarding these, WO 98/36322, EP 803764A1, JP-A-10-186567, 10-18568 and the like can be referred to.

13) Coating method The photothermographic material in the invention may be coated by any method. Specifically, various coating operations including extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating, or extrusion coating using a hopper of the type described in US Pat. No. 2,681,294. And Stephen F. Kistler, Peter M. et al. The extrusion coating described in “LIQUID FILM COATING” (CHAPMAN & HALL, 1997) by Schweizer (1997), pages 399 to 536 is preferably used, and slide coating is particularly preferably used. An example of the shape of a slide coater used for slide coating is shown in FIG. 11b. 1 If desired, two or more layers can be coated simultaneously by the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761,791 and British Patent No. 837,095. . In the present invention, particularly preferred coating methods are those described in JP-A Nos. 2001-194748, 2002-153808, 2002-153803, and 2002-182333.

The organic silver salt-containing layer coating solution in the present invention is preferably a so-called thixotropic fluid. Regarding this technique, JP-A-11-52509 can be referred to. The viscosity of the organic silver salt-containing layer coating solution in the present invention is preferably 400 mPa · s or more and 100,000 mPa · s or less, more preferably 500 mPa · s or more and 20,000 mPa · s or less, at a shear rate of 0.1 S ⁻¹ . In addition, at a shear rate of 1000 S- ^1, it is preferably 1 mPa · s or more and 200 mPa · s or less, and more preferably 5 mPa · s or more and 80 mPa · s or less.

In the case of preparing the coating liquid of the present invention, a known in-line mixer or implant mixer is preferably used when mixing two kinds of liquids. A preferred in-line mixer of the present invention is described in JP-A No. 2002-85948, and an implant mixer is described in JP-A No. 2002-90940.
The coating solution in the present invention is preferably subjected to defoaming treatment in order to keep the coated surface state good. A preferable defoaming treatment method of the present invention is the method described in JP-A No. 2002-66431.

When applying the coating solution of the present invention, it is preferable to perform static elimination in order to prevent adhesion of dust, dust, and the like due to electric resistance of the support. An example of a preferable static elimination method in the present invention is described in JP-A No. 2002-143747.
In the present invention, it is important to precisely control the drying air and the drying temperature in order to dry the non-setting image forming layer coating solution. The preferred drying method of the present invention is described in detail in JP-A Nos. 2001-194749 and 2002-139814.

  The photothermographic material of the present invention is preferably subjected to a heat treatment immediately after coating and drying in order to improve film formability. The temperature of the heat treatment is preferably in the range of 60 ° C. to 100 ° C. as the film surface temperature, and the heating time is preferably in the range of 1 second to 60 seconds. A more preferable range is a film surface temperature of 70 ° C. to 90 ° C. and a heating time of 2 seconds to 10 seconds. A preferable heat treatment method of the present invention is described in JP-A No. 2002-107872.

In order to stably and continuously produce the photothermographic material of the present invention, the production methods described in JP-A Nos. 2002-156728 and 2002-182333 are preferably used.
The photothermographic material is preferably a mono-sheet type (a type capable of forming an image on the photothermographic material without using another sheet such as an image receiving material).

14) Packaging material The photothermographic material of the present invention is a packaging material having a low oxygen permeability and / or moisture permeability in order to suppress fluctuations in photographic performance during raw storage or to improve curling, curling, etc. It is preferable to package. The oxygen permeability is preferably 50 mL / atm · m ² · day or less at 25 ° C., more preferably 10 mL / atm · m ² · day or less, more preferably 1.0 mL / atm · m ² · day or less. is there. The moisture permeability is preferably 10 g / atm · m ² · day or less, more preferably 5 g / atm · m ² · day or less, and still more preferably 1 g / atm · m ² · day or less.
Specific examples of the packaging material having a low oxygen permeability and / or moisture permeability are disclosed in, for example, JP-A-8-254793. This is a packaging material described in JP-A-2000-206653.

15) Other technologies that can be used Techniques that can be used in the photothermographic material of the present invention include EP80364A1, EP883022A1, WO98 / 36322, JP-A-56-62648, JP-A-58-62644, and JP-A-5-62644. 9-43766, 9-281737, 9-297367, 9-304869, 9-31405, 9-329865, 10-10669, 10-62899, 10-69023 10-186568, 10-90823, 10-171603, 10-186565, 10-186567, 10-186567 to 10-186572, 10-197974, Nos. 10-197982, 10-197983, 10-197985 to 1 No. 0-197987, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10-307365, No. 10- No. 312038, No. 10-339934, No. 11-7100, No. 11-15105, No. 11-24200, No. 11-24201, No. 11-30832, No. 11-84574, No. 11-65021 11-109547, 11-125880, 11-129629, 11-133536 to 11-133539, 11-133542, 11-133543, 11-223898, 11-352627, 11-305377, 11-305378, 11-305 84, 11-305380, 11-316435, 11-327076, 11-338096, 11-338098, 11-338099, 11-343420, JP 2000-187298 , 2000-10229, 2000-47345, 2000-206642, 2000-98530, 2000-98531, 2000-112059, 2000-112060, 2000-112104, Examples thereof include 2000-112064 and 2000-171936.

(Image forming method)
1) Exposure The photothermographic material of the invention may be subjected to image exposure by any means. The photothermographic material of the present invention is preferably subjected to scanning exposure with a laser beam.
Preferred lasers that can be used in the present invention are red to infrared light emitting He—Ne lasers, red semiconductor lasers, blue to green light emitting Ar ⁺ , He—Ne, He—Cd lasers, and blue semiconductor lasers. 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 preferably 1 second to 60 seconds, more preferably 3 seconds to 30 seconds, and even more preferably 5 seconds to 25 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 2 to 6 stages and lower the temperature about 1 ° C. to 10 ° C. at the tip. 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 rear end. It is desirable to start the heat development before the time.
Imagers capable of rapid processing preferred in the present invention are described in, for example, JP-A Nos. 2002-289804 and -287668.

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
1. Production of PET support (1) Film formation Using terephthalic acid and ethylene glycol, according to a conventional method, intrinsic viscosity IV = 0.66 (phenol / tetrachloroethane = 6/4 (mass ratio)) at 25 ° C. PET) was obtained. 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 discharge treatment Using a solid state corona discharge treatment machine 6KVA model manufactured by Pillar, both surfaces of the support were treated at room temperature at 20 m / min. 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 1) Preparation formulation of undercoat layer coating solution (1) (for photosensitive layer side undercoat layer)
59 g of pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 10% by mass solution 5.4 g
MP-1000 manufactured by Soken Chemical Co., Ltd. (polymer fine particles, average particle size 0.4 μm)
0.91g
935 mL of distilled water

Formula (2) (for back layer 1st layer)
Styrene-butadiene copolymer latex 158g
(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)
20g
10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
854 mL of distilled water

Formula (3) (for back side second layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion)
84g
Gelatin (10 mass% aqueous solution) 89.2g
8.6 g of Metroise TC-5 (2% by mass aqueous solution) manufactured by Shin-Etsu Chemical Co., Ltd.
MP-1000 0.01g manufactured by Soken Chemical Co., Ltd.
10 mL of 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 6 mL
Proxel (ICI) 1mL
805 mL of distilled water

2) Undercoat After the corona discharge treatment is performed on both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm, the undercoat coating solution formulation (1) is wet-coated with a wire bar on one side (image forming layer side). Apply to an amount of 6.6 mL / m ² (per side) and dry at 180 ° C. for 5 minutes, then wet coat the above-mentioned undercoat coating formulation (2) on the back side (back side) with a wire bar. Was applied at a temperature of 5.7 mL / m ² , dried at 180 ° C. for 5 minutes, and the undercoat coating solution formulation (3) was further applied to the back surface (back surface) with a wire bar at a wet coating amount of 7.7 mL / m 2. ² was applied and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

2. Preparation and Application of Back Layer Coating Solution While stirring 830 g of MEK, 84.2 g of cellulose acetate butyrate (manufactured by Eastman Chemical, CAB381-20) and 4.5 g of polyester resin (manufactured by Boston, Vitel PE2200B) were added. Dissolved. To this dissolved liquid, 0.30 g of dye B was added, and 4.5 g of a fluorine-based activator (Surflon KH40, manufactured by Asahi Glass Co., Ltd.) dissolved in 43.2 g of methanol and a fluorine-based activator (Dainippon Ink, Inc.) Co., Ltd., MegaFuck F120K) 2.3 g was added and sufficiently stirred until dissolved. Finally, 75 g of silica (WR Grace, Syloid 64X6000) dispersed in methyl ethyl ketone at a concentration of 1% by mass with a dissolver type homogenizer was added and stirred to prepare a back layer coating solution.

  The back layer coating solution prepared in this manner was applied and dried by an extrusion coater on a support so that the dry film thickness was 3.5 μm. It dried for 5 minutes using the drying air with a drying temperature of 100 degreeC, and dew point temperature of 10 degreeC.

3. 3. Image forming layer, intermediate layer, and surface protective layer 3-1. Preparation of coating materials 1) Preparation of 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 Solution C and Solution D so that it would be 1 × 10 ⁻⁴ mole per mole 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 1 mol of silver, and 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. After 1 minute, 1.3 mL of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ -diethylmelamine was added, and after another 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to 1 mol of silver with a methanol solution. 4.8 × 10 ⁻³ mol per mol, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in methanol solution with 5.4 × 10 ⁻³ mol and 1− Silver halide emulsion 1 was prepared by adding (3-methylureidophenyl) -5-mercaptotetrazole in an aqueous solution to 8.5 × 10 ⁻³ mol per 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 Mixed Emulsion-1 for Coating Solution >>
The silver halide emulsion 1 was dissolved, and 7 × 10 ⁻³ mol of benzothiazolium iodide was added as a 1% by mass aqueous solution per mol of silver. Further, the amount of the one-electron oxidant produced by one-electron oxidation is 2 × 10 ⁻³ mol per mol of silver halide, each of compounds 1, 2 and 3 capable of emitting one electron or more. Added. Further, compounds 1 and 2 having an adsorbing group and a reducing group were added in an amount of 8 × 10 ⁻³ mol per mol of silver halide. Further, water was added so that the silver halide content per 1 L of the mixed emulsion for coating solution was 15.6 g as silver.

2) Preparation of silver halide / organic silver salt dispersion 688 g of fatty acid having a composition of 42 mol% behenic acid, 34 mol% arachidic acid and 24 mol% stearic acid was dissolved in 13 L of water at 80 ° C and mixed for 15 minutes. Then, 89.18 g NaOH dissolved in 1.5 L of 80 ° C. water was added and mixed for 5 minutes to form a dispersion. At 80 ° C., a solution obtained by diluting 19 mL of concentrated nitric acid with 50 mL of water was added to this dispersion. The dispersion was cooled to 55 ° C. and stirred for 25 minutes, and then kept at 55 ° C. to obtain mixed emulsion-1 for coating solution. An amount equivalent to 1 mol of silver halide was added to the dispersion and mixed for 5 minutes. Further, 336.5 g of silver nitrate was dissolved in 2.5 L of water and added at 55 ° C. over 10 minutes. Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage are repeated until the electrical conductivity of the drainage reaches 2 μS / cm, and after centrifugal dehydration, circulation with warm air with an oxygen partial pressure capacity of 10% is performed at 45 ° C. until there is no mass loss. Drying was performed with a dryer.

3) Redispersion of organic silver salt containing photosensitive silver halide in organic solvent 209 g of the above powdered organic silver salt and 11 g of polyvinyl butyral powder (Monsant Butvar B-79) were dissolved in 780 g of methyl ethyl ketone (MEK), and VMA was dissolved. -It stirred with the dissolver DISPERMAT CA-40M type | mold made from GETZMANN, and it was left to stand at 7 degreeC overnight, and obtained the slurry form.

  The slurry was dispersed in two passes with a GM-2 pressure homogenizer manufactured by SMT Co., thereby preparing a dispersion of an organic silver salt containing a photosensitive silver halide emulsion. At this time, the processing pressure during one pass was 6000 psi.

4) Preparation of image forming layer coating solution 507 g of the above-described organic silver salt containing photosensitive silver halide in an organic solvent was stirred at 13 ° C. for 15 minutes, and 10% by mass of pyridinium hydrobromide perbromide (PHP). ) 3.9 mL of methanol solution was added. After stirring for 2 hours, 5.2 mL of a 11 mass% calcium bromide methanol solution was added. Stirring was continued for 30 minutes, after which 117 g Butvar B-79 was added. After stirring for another 30 minutes, 27.3 g of 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -2-methylpropane was added and stirring was continued for another 15 minutes. Thereafter, 2.73 g of 2- (tribromomethylsulfonyl) quinoline was added and stirred for 15 minutes. Subsequently, a solution prepared by dissolving 1.39 g of Desmodur N3300 (manufactured by Mobay, aliphatic isocyanate) in 12.3 g of MEK was added, and the mixture was further stirred for 15 minutes, and then heated at 21 ° C. for 15 minutes.

  To 100 g of this dispersion, 1 mg of sensitizing dye-1, 0.47 g of 4-chlorobenzophenone-2-carboxylic acid, and 0.043 g of 5-methyl-2-mercaptobenzimidazole are added and stirred at 21 ° C. for 1 hour. did. Next, 0.368 g of phthalazine, 0.123 g of tetrachlorophthalic acid and 2 g of dye-1 were added to complete the image forming layer coating solution.

5) Preparation of surface protective layer coating solution While stirring MEK865g, cellulose acetate butyrate (manufactured by Eastman Chemical Co., CAB171-15) 96g, polymethylmethacrylic acid (Rohm & Haas Co., Paraloid A-21) 4.5g 1,3-di (vinylsulfonyl) -2-propanol 1.5 g, benzotriazole 1.0 g, and fluorosurfactant (Asahi Glass Co., Surflon KH40) 1.0 g were added and dissolved. % Cellulose acetate butyrate (Eastman Chemical, CAB171-15) and 9% by weight calcium carbonate (Speciality Minerals, Super-Pflex200) in MEK for 30 minutes at 8000 rpm with a dissolver type homogenizer 30 g of the dispersed powder was added and stirred to prepare a surface protective layer coating solution.

3-2. Preparation of photothermographic material-1 The photothermographic material 1 is produced by simultaneously applying the image forming layer coating solution 1 and the surface protective layer application fatigue on the surface opposite to the back layer of the support with an extrusion coater. did. The coating was performed so that the image forming layer had an applied silver amount of 1.0 g / m ² and the surface protective layer had a dry film thickness of 2.5 μm. Then, it dried for 10 minutes using the drying air with a drying temperature of 75 degreeC and a dew point temperature of 10 degreeC.

3-3. Preparation of photothermographic material-2 to 11 Photothermographic material-2 to 11 were prepared by adding a reducing agent of general formula (1) and a coupler to photothermographic material-1 as shown in Table 1. Was made.

  The compounds used in the examples are shown below.

4). Performance Evaluation An exposure machine using a semiconductor laser having a high frequency mass and a wavelength of 800 nm to 820 nm as a multi-mode semiconductor laser as an exposure source was prototyped, and image exposure by laser scanning was given by this exposure machine. At this time, an image was recorded by setting the incident angle of the scanning laser beam to the exposed surface of the photothermographic material at 75 degrees. Thereafter, using an automatic developing machine having a heat drum, the back layer of the photothermographic material and the drum surface were in contact with each other, and heat development was performed at 124 ° C. for 24 seconds, and the obtained image was evaluated with a densitometer. .

Sensitivity: Using the reciprocal of the exposure amount giving a density of 1.0 as the sensitivity, sample no. The value relative to 1 is shown.
Fog: The density of the unexposed area was defined as fog (Dmin).
Dmax: the maximum density that is saturated when the exposure amount is increased.

  The results are shown in Table 1. The sample of the present invention had high sensitivity and high Dmax. In particular, by using two couplers, a black and white image having a good color tone was obtained. In particular, a preferable black-and-white image was obtained when they were complementary to each other. Further favorable results were obtained when three couplers were used in combination.

Example 2
In the preparation of Emulsion 1 of Example 1, instead of ripening by adding tellurium sensitizer C, the temperature was raised to 47 ° C., and then 0.15 mmol of triethylthiourea per mol of silver was added with a methanol solution for 80 minutes. Emulsion 2 was prepared in the same manner as Emulsion 1 except that it was aged and all subsequent steps were carried out at 47 ° C. The grain shape was the same as emulsion 1.
A sample was prepared in the same manner as in Example 1 except that the silver halide emulsion 2 was used instead of the silver halide emulsion 1 in Example 1, and the performance was evaluated. As a result, all of the compounds of the present invention showed excellent performance as in Example 1.

Example 3
<Preparation of silver halide emulsion 3>
<Particle formation>
To a solution of 1420 mL of distilled water, 4.3 mL of a 1% by mass potassium iodide solution was added, and a solution containing 3.5 mL of 0.5 mol / L sulfuric acid and 36.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 42 ° C., solution A in which distilled water was added to 22.22 g of silver nitrate and diluted to 195.6 mL and solution B in which 21.8 g of potassium iodide was diluted to 218 mL with distilled water were added at a constant flow rate. The whole amount was added over 9 minutes. 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, Solution C obtained by adding distilled water to 51.86 g of silver nitrate and diluting to 317.5 mL and Solution D obtained by diluting 60 g of potassium iodide to a volume of 600 mL with distilled water were added in a total amount over 120 minutes at a constant flow rate. 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 Solution C and Solution D so that it would be 1 × 10 ⁻⁴ mole per mole 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.

《Chemical sensitization》
While maintaining the silver halide dispersion at 38 ° C. with stirring, 5 mL of a 0.34 mass% methanol solution of 1,2-benzisothiazolin-3-one was added, and the temperature was raised to 47 ° C. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per 1 mol of silver, and further 5 minutes later, tellurium sensitizer C was added in a methanol solution at a rate of 2. per mol of silver. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes.
Add 1.3 mL of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″, N ″ -diethylmelamine, and after another 4 minutes, add 5-methyl-2-mercaptobenzimidazole to 1 mol of silver with methanol solution. 8 × 10 ⁻⁴ mol and 5.4 × 10 ⁻⁴ mol of 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole per 1 mol of silver were added in a methanol solution.
The grains in the silver halide emulsion thus prepared were pure silver iodide grains having an average sphere equivalent diameter of 0.040 μm and a sphere equivalent diameter variation coefficient of 18%. Moreover, it is a tetrahedral particle | grain which has (001), {100}, {101} face, The ratio of the (gamma) phase was 30% when measured using the X-ray powder diffraction analysis. The particle size and the like were determined from an average of 1000 particles using an electron microscope.
Further, the compounds 1 and 2 having an adsorbing group and a reducing group were added in an amount of 8 × 10 ⁻⁴ mol per mol of silver halide.
<Preparation of silver halide emulsion 3 for coating solution>
Silver halide emulsion 3 was heated and dissolved, and benzothiazolium iodide was added in a 1% by mass aqueous solution at 7 × 10 ⁻³ mol per mol of silver. Further, the compounds 1 and 2 having an adsorbing group and a reducing group were added in an amount of 8 × 10 ⁻⁴ mol per mol of silver halide. Further, water is added so that the content of silver halide per 1 kg of the mixed emulsion for coating liquid is 15.6 g as silver, and 1- (3-methylureidophenyl) is adjusted to 0.17 g per 1 kg of the mixed emulsion for coating liquid. -5-mercaptotetrazole was added.

<Preparation of coated sample>
A coating sample shown in Table 2 was prepared in the same manner as the sample of Example 1, using silver halide emulsion 3 for coating solution instead of emulsion 1 for coating solution, but without adding sensitizing dye-1. did.

<Evaluation>
1) Exposure and thermal development The semiconductor laser of 800 nm to 820 nm in Example 1 was changed to a blue semiconductor laser manufactured by Nichia, and the others were exposed and thermally developed in the same manner as in Example 1.
2) Evaluation item and result Evaluation similar to Example 1 was performed. The results are shown in Table 3.
As a result, the sample of the present invention showed excellent performance as in Example 1.

Example 4
1. Preparation of silver halide emulsion << Preparation of silver halide emulsion A >>
4.3 mL of 1% by mass potassium iodide solution was added to 1421 mL of distilled water, and 3.5 mL of 0.5 mol / L sulfuric acid, 36.5 g of phthalated gelatin, and 5 mass of 2,2 ′-(ethylenedithio) diethanol. The solution to which 160 mL of methanol solution was added was kept in a stainless steel reaction vessel while maintaining the liquid temperature at 75 ° C., and the solution A diluted with 218 mL by adding distilled water to 22.22 g of silver nitrate and potassium iodide 36. Solution B, in which 6 g was diluted to 366 mL with distilled water, was added in a total amount over 16 minutes at a constant flow rate, and Solution B was added by the control double jet method while maintaining pAg at 10.2. 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 508.2 mL and a solution D in which 63.9 g of potassium iodide was diluted to 639 mL with distilled water were used. Solution C was added at a constant flow rate over 80 minutes. The entire amount was added, and Solution D was added by the control double jet method while maintaining pAg at 10.2. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so that it would be 1 × 10 ⁻⁴ mole per mole 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 11.0.

The silver halide emulsion A is a pure silver iodide emulsion, and has a plate shape having an average projected area diameter of 0.93 μm, an average projected area diameter variation coefficient of 17.7%, an average thickness of 0.057 μm, and an average aspect ratio of 16.3. The grains accounted for over 80% of the total projected area. The equivalent sphere diameter was 0.42 μm.
As a result of analysis by X-ray powder diffraction analysis, 30% of silver iodide was present in the γ phase.

<< Preparation of silver halide emulsion B >>
One mole of tabular grain AgI emulsion prepared with silver halide emulsion A was placed in a reaction vessel. The pAg was 10.2 measured at 38 ° C. Then, by double jet addition, 0.5 mol / L KBr solution and 0.5 mol / L AgNO ₃ solution were added at 10 mL / min over 20 minutes, and substantially 10 mol% silver bromide was added to the AgI host. Epitaxially precipitated on the emulsion. During operation, pAg was maintained at 10.2. Furthermore, 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 11.0.

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 moles per 1 mole of silver. 9 × 10 ⁻⁵ mol was added and aged for 91 minutes. Thereafter, 1.3 mL of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ -diethylmelamine was added, and after 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the methanol solution per mol of silver. 4.8 × 10 ⁻⁴ mol, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in a methanol solution with 5.0 × 10 ⁻³ mol and 1- ( 3-Methylureidophenyl) -5-mercaptotetrazole was added in an aqueous solution to 5.0 × 10 ⁻⁴ mol per mol of silver to prepare silver halide emulsion B.

<< Preparation of silver halide emulsion C >>
In the same manner as silver halide emulsion A, the addition amount of 2,2 ′-(ethylenedithio) diethanol in a 5% by weight methanol solution, the temperature at the time of grain formation, and the addition time of solution A were appropriately changed to change the silver halide. Emulsion C was prepared. Silver halide Emulsion C is a pure silver iodide emulsion, tabular grains having an average projected area diameter of 1.369 μm, an average projected area diameter variation coefficient of 19.7%, an average thickness of 0.130 μm, and an average aspect ratio of 11.1. Accounted for more than 80% of the total projected area. The equivalent sphere diameter was 0.71 μm.
As a result of analysis by X-ray powder diffraction analysis, 15% of silver iodide was present in the γ phase.

<< Preparation of silver halide emulsion D >>
Except for using the silver halide emulsion C, a silver halide emulsion D containing 10 mol% of silver bromide epitaxial was prepared in the same manner as the silver halide emulsion B.

<< Preparation of Mixed Emulsion 4 for Coating Solution >>
Dissolve silver halide emulsion B and silver halide emulsion D in a silver molar ratio of 5: 1, and add 7 × 10 ⁻³ mol of benzothiazolium iodide per mol of silver in a 1% by mass aqueous solution. did. Further, the amount of the one-electron oxidant produced by one-electron oxidation is 2 × 10 ⁻³ mol per mol of silver halide, each of compounds 1, 2 and 3 capable of emitting one electron or more. Added. Further, Compound 1 and 2 having an adsorbing group and a reducing group were added in an amount of 8 × 10 ⁻³ mol per mol of silver halide to prepare mixed emulsion 4 for coating solution.

2. Preparation of Coating Sample Using the mixed emulsion 4 for coating liquid instead of the mixed emulsion 3 for coating liquid in Example 3, the reducing agent and coupler were changed to the types and addition amounts shown in Table 4, and the others were in Example 3. In the same manner, samples 31 to 37 were prepared.

3. Evaluation Using an X-ray regular screen HI-SCREEN-B3 (using CaWO ₄ as a phosphor, emission peak wavelength 425 nm) manufactured by Fuji Film Co., Ltd. Produced.
This assembly was subjected to X-ray exposure for 0.05 seconds, and X-ray sensitometry was performed. The X-ray apparatus used was a trade name DRX-3724HD manufactured by Toshiba Corporation, and a tungsten target was used. A voltage of 80 kVp was applied with a three-phase full-wave rectification type pulse generator, and X-rays passed through a 7 cm water filter having absorption almost equivalent to that of the human body were used as a light source. The X-ray exposure was changed by the distance method, and step exposure was performed with a width of logE = 0.15. After the exposure, heat development was performed under the following heat development conditions. The obtained image was evaluated with a densitometer.

The heat development section of the Fuji Medical Dry Laser Imager FM-DPL was modified to produce a heat development machine that can be heated from both sides. In addition, the film was remodeled so that the film sheet could be conveyed by changing the conveyance roller of the heat developing unit to a heat drum. Four panel heaters were set to 127 ° C-134 ° C-136 ° C-136 ° C, and the temperature of the heat drum was set to 136 ° C. The heat development time was set so that the heat development time was 52 seconds in total by adjusting the conveyance speed.
The obtained image was subjected to density measurement with a Macbeth densitometer to produce a density characteristic curve with respect to the logarithm of the exposure amount.
Fog: The density of the non-image area was measured with a Macbeth densitometer.
Sensitivity: Sensitivity is represented by the reciprocal of the exposure amount giving a blackening density of fog + 1.0. The sensitivity of 1 is taken as 100, and the relative value is shown. A larger value indicates higher sensitivity.
The obtained results are shown in Table 5.
As a result, the sample of the present invention had high sensitivity and high Dmax. In particular, by using two couplers, a black and white image having a good color tone was obtained.

Claims (12)

A photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions and a binder on at least one surface of a support, It contains polyvinyl acetal as a binder, a compound represented by the following general formula (1) as the reducing agent, and a coupler capable of forming a dye by reacting with an oxidation product of the reducing agent. Photothermographic material:

(In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom or a substituent which can be substituted on a benzene ring, and R ₅ represents an alkyl group, an aryl group or a heterocyclic group. To express.). The photothermographic material according to claim 1, wherein the polyvinyl acetal is a compound represented by the following general formula (VA):

(In the formula, R represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or an aryl group. X is 10 mol% to 50 mol%, Y is 0 mol% to 10 mol%, Z is 50 mol% to 90 mol%).   3. The photothermographic material according to claim 2, wherein R in the general formula (VA) is a butyl group.   4. The photothermographic material according to claim 1, further comprising at least two types of the couplers.   5. The photothermographic material according to claim 4, wherein hues of color images formed from the at least two types of couplers have a complementary color relationship with each other. The coupler is represented by the following general formulas (C-1), (C-2), (C-3), (M-1), (M-2), (M-3), (Y-1), (Y The photothermographic material according to claim 1, wherein the photothermographic material is a compound selected from the group consisting of -2) and (Y-3).

(Wherein X ₁ represents a hydrogen atom or a leaving group, Y ₁ and Y ₂ represent an electron-withdrawing substituent, and R ₁ represents an alkyl group, an aryl group, or a heterocyclic group);

(Wherein X ₂ represents a hydrogen atom or a leaving group, R ₂ represents an acylamino group, a ureido group or a urethane group, R ₃ represents a hydrogen atom, an alkyl group or an acylamino group, R ₄ represents a hydrogen atom, or Represents a substituent, R ₃ and R ₄ may be linked to each other to form a ring);

(Wherein X ₃ represents a hydrogen atom or a leaving group, R ₅ represents a carbamoyl group or a sulfamoyl group, and R ₆ represents a hydrogen atom or a substituent);

(Wherein X ₄ represents a hydrogen atom or a leaving group, R ₇ represents an alkyl group, an aryl group or a heterocyclic group, and R ₈ represents a substituent);

(Wherein X ₅ represents a hydrogen atom or a leaving group, R ₉ represents an alkyl group, an aryl group or a heterocyclic group, and R ₁₀ represents a substituent);

(Wherein X ₆ represents a hydrogen atom or a leaving group, R ₁₁ represents an alkyl group, an aryl group, an acylamino group or an anilino group, and R ₁₀ represents an alkyl group, an aryl group or a heterocyclic group);

(Wherein X ₇ represents a hydrogen atom or a leaving group, R ₁₃ represents an alkyl group, an aryl group or an indoleenyl group, and R ₁₄ represents an aryl group or a heterocyclic group);

(Wherein X ₈ represents a hydrogen atom or a leaving group, Z represents a divalent group necessary to form a 5- to 7-membered ring, and R ₁₅ represents an aryl group or a heterocyclic group. );

(In the formula, X ₉ represents a hydrogen atom or a leaving group, R ₁₆ , R ₁₇ and R ₁₈ each represent a substituent, n represents an integer of 0 to 4, and m represents an integer of 0 to 5. When n or m is 2 or more, the plurality of R ₁₆ and R ₁₇ may be the same group or different groups. The photothermographic material according to claim 1, wherein the silver coating amount is 0.3 g / m ² or more and 1.3 g / m ² or less. The photothermographic material according to any one of claims 1 to 7, characterized in that it contains methyl ethyl ketone 0.1 mg / m ² or more 150 mg / m ² or less.   9. The photothermographic material according to claim 1, wherein an average grain size of the photosensitive silver halide is 0.01 [mu] m or more and 0.2 [mu] m or less.   50% or more of the total projected area of the photosensitive silver halide is a tabular grain having an average aspect ratio of 2 or more, and the average grain size is 0.3 μm or more and 8.0 μm or less. The photothermographic material according to any one of claims 1 to 8.   11. The photothermographic material according to claim 9, wherein the silver iodide content of the photosensitive silver halide is 35% or less.   11. The photothermographic material according to claim 9, wherein the silver iodide content of the photosensitive silver halide is 40% or more.