JP2006317562A - Heat-developable image recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-developable image recording material having high sensitivity and high γ, and ensuring little variations in photographic performance, such as a character line width due to variations in the environmental humidity during storage. <P>SOLUTION: The heat-developable image recording material has on a support an image forming layer, containing a non-photosensitive organic silver salt, a reducing agent for the organic silver salt, a photosensitive silver halide having a silver iodide content of 40-100 mol%, and a halogen precursor in an amount ≤0.1 mol per mol of the non-photosensitive organic silver salt, wherein a binder containing a polymer prepared by copolymerizing 10-70 mass% of a monomer represented by Formula (M): CH<SB>2</SB>=CR<SB>01</SB>-CR<SB>02</SB>=CH<SB>2</SB>is used as a binder in the image forming layer. In the Formula, R<SB>01</SB>represents H, a 1-6C alkyl, halogen or cyano, and R<SB>02</SB>represents a 1-6C alkyl, halogen or cyano. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat-developable image recording material, and more particularly to a heat-developable image recording material suitable for printing plate making. More specifically, the present invention relates to a heat-developable image recording material that is ultra-high contrast, high sensitivity, and improved in processing humidity dependency.

Conventionally, in the fields of printing plate making and medical treatment, waste liquids resulting from wet processing of image forming materials have been a problem in terms of workability. In recent years, reduction of processing waste liquids has been strongly desired from the viewpoint of environmental conservation and space saving. ing. Therefore, there is a need for a technique related to photothermographic materials for photographic applications that can be used for efficient exposure and can form a clear black image with high resolution using a laser image setter, a laser imager, or the like. . As this technique, for example, a photothermographic material containing an organic silver salt, photosensitive silver halide grains, a reducing agent and a binder on a support as described in Non-Patent Document 1 or the like is known. Yes.
These heat-developable photosensitive materials form photographic images by heat-development processing, and the reducible silver source (organic silver salt), photosensitive silver halide, reducing agent, and the color tone of silver are adjusted as necessary. Toning agents and the like are usually contained in a dispersed state in an (organic) binder matrix. The photothermographic material is stable at normal temperature, but is developed by heating to a high temperature (for example, 80 ° C. to 140 ° C.) after exposure. That is, by heating, silver is generated through an oxidation-reduction reaction between an organic silver salt (functioning as an oxidizing agent) and a reducing agent. This redox reaction is promoted by the catalytic action of the latent image generated in the silver halide upon exposure. The silver produced by the reaction of the organic silver salt in the exposed areas provides a black image that contrasts with the unexposed areas and forms an image. This reaction process proceeds without supplying a treatment liquid such as water from the outside.
Such photothermographic materials have been widely used for microfilms and X-ray photosensitive materials, but are only partially used as printing photosensitive materials. One reason for the lack of widespread use of heat-developable photosensitive materials in the field of printing photosensitive materials is that the maximum density of images obtained for printing photosensitive materials is low and the gradation is soft. The resulting image quality is significantly lower.
On the other hand, due to rapid progress of lasers and light emitting diodes in recent years, development of photosensitive materials having high sensitivity, maximum density (Dmax), and high gradation is strong due to suitability for scanners having an oscillation wavelength of 700 to 1000 nm. It was desired. In addition to that, there is a growing demand for simple processing and drying.
Since the development of the photothermographic material is performed without supplying a processing solution such as water from the outside, the progress of the development is greatly influenced by the amount of moisture contained in the photothermographic material.
The photothermographic material is stored in various temperature and humidity environments. If the storage environment is different, the amount of water contained in the photothermographic material is also different, so that the photographic performance obtained as a result of development varies depending on the storage environment.

With respect to the above situation, Patent Document 1 describes that a photothermographic material having excellent image storage stability, sensitivity, and processing brittleness can be obtained by using a binder containing a polymer having a specific monomer as a copolymerization component. However, the use of the polymer alone cannot prevent photographic performance fluctuations due to changes in the storage environment, and a technique for providing a photothermographic material that has little photographic performance fluctuations due to changes in the storage environment is desired. ing.
In Patent Document 2, a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol% is used for the image forming layer, a halogen precursor is included, and a specific dye is included in the back layer. It is described that an image having a gamma of 7 or more can be formed by heat development at a temperature of 100 ° C. to 150 ° C. after exposure with light having a wavelength of 500 nm or less, and storage stability is improved. However, even with this technique, it has not been possible to prevent fluctuations in photographic performance due to fluctuations in the storage environment.
D. “Dry Silver Photographic Materials” by Morgan (Handbook of Imaging Materials, marcel Dekker. Inc. 48. 1991). JP 2004-184663 A JP 2003-14964 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to achieve high sensitivity, high gamma, and heat with little variation in photographic performance, such as character line width, due to fluctuations in environmental humidity to be stored. It is to provide a developed image recording material.

(1) On a support, a non-photosensitive organic silver salt, a reducing agent for the organic silver salt, a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol%, and 1 mol of non-photosensitive organic silver It has an image forming layer containing a halogen precursor of 0.1 mol or less, and contains a polymer obtained by copolymerization of 10% by mass or more and 70% by mass or less of a monomer represented by the following general formula (M) as a binder of the image forming layer. A heat-developable image recording material using a binder.
General formula (M)
CH ₂ = CR ₀₁ -CR ₀₂ = CH ₂
(In the formula, R ₀₁ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group, and R ₀₂ represents an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group.)
(2) The heat-developable image recording material as described in (1) above, which contains a halogen precursor in an amount of 1.0 × 10 ⁻⁴ mol to 0.05 mol per mol of non-photosensitive organic silver.
(3) A back layer containing a dye represented by the following general formula (1) or (2) is provided and exposed to light having a wavelength of 500 nm or less, followed by heat development at a temperature of 100 ° C. to 150 ° C. Thus, an image having a gamma of 7 or more is formed. The heat-developable image recording material as described in (1) or (2) above.

(Wherein R ¹ is a hydrogen atom, an aliphatic group, an aromatic group, —NR ²¹ R ²⁶ , —OR ²¹ or —SR ²¹ (wherein R ²¹ and R ²⁶ are each independently a hydrogen atom, an aliphatic group, Or an aromatic group, and R ²¹ and R ²⁶ may form a nitrogen-containing heterocycle in cooperation with each other.
R ² represents a hydrogen atom, an aliphatic group or an aromatic group. L ¹ and L ² each independently represents a substituted or unsubstituted methine group. Moreover, the substituent of the substituted methine group represented by L ¹ and L ² may be one in which the substituents are bonded to each other to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. Z ¹ represents an atomic group necessary for completing a 5-membered or 6-membered nitrogen-containing heterocyclic ring. The nitrogen-containing heterocycle may have an aromatic ring as a condensed ring. Further, the nitrogen-containing heterocycle and its condensed ring may have a substituent.
A represents an acidic nucleus, and B represents an aromatic group, an unsaturated heterocyclic group, or a group represented by the following general formula (3). n and m each represent 1 or 2.

(In the formula, L ³ represents a substituted or unsubstituted methine group. L ³ may be bonded to L ² to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. R ³ represents a fatty acid. Z ² represents an atomic group necessary to complete a 5- or 6-membered nitrogen-containing heterocycle, and the nitrogen-containing heterocycle has an aromatic ring as a condensed ring. In addition, the nitrogen-containing heterocycle and its condensed ring may have a substituent.))
(4) The heat-developable image recording material according to any one of (1) to (3) above, wherein a back layer containing a base precursor is provided.

  The heat-developable image recording material of the present invention has a super-high contrast, high sensitivity, and improved environmental humidity dependency.

The present invention is described in detail below.
The heat-developable image recording material of the present invention comprises, on a support, a non-photosensitive organic silver salt, a reducing agent for the organic silver salt, a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol%, and A binder containing a polymer obtained by copolymerizing 10% by mass or more and 70% by mass or less of the monomer represented by the general formula (M) as a binder, containing 0.1 mol or less of halogen precursor per 1 mol of non-photosensitive organic silver. It has the image forming layer used. In the heat-developable image recording material of the present invention, a back layer is preferably provided on the surface of the support opposite to the side on which the image forming layer is provided. It is preferable that the dye represented by Formula (1) or (2) and a base precursor are contained. Further, when the back layer contains the dye represented by the above general formula (1) or (2) (hereinafter sometimes referred to as the dye of the present invention), it is exposed to light having a wavelength of 500 nm or less. It is preferable that an image having a gamma of 7 or more is formed by heat development at a temperature of 100 ° C. to 150 ° C.
The heat-developable image recording material of the present invention preferably further has a non-photosensitive protective layer on the image forming layer.

In the heat-developable image recording material of the present invention, the image forming layer may be a single layer or a plurality of layers. When the image forming layer is formed into a plurality of layers, the respective materials of the image forming layer can be added to different layers, and the image forming layer can be melted and interacted with each other during heat development. Alternatively, one material may be distributed and added to different layers.
When an image forming layer is formed by a coating method, when using an aqueous coating solution, it is preferable to adjust the pH of the coating solution to 5.5 to 7.8, and the acid used when adjusting the pH of the aqueous coating solution is It is preferable not to contain a halogen. When using a coating solution containing an organic solvent as a main solvent, it is important to adjust the viscosity. Specifically, it is necessary to adjust the viscosity within the range of 1 mPa · s to 100 mPa · s so that the viscosity is lower than that of the protective layer. preferable. Whether using an aqueous coating solution or a coating solution containing an organic solvent as a main solvent, it is preferable to simultaneously coat a plurality of layers including a protective layer.

First, the photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol% used in the image forming layer of the present invention will be described.
In the present invention, a high silver iodide emulsion having a silver iodide content of 40 mol% to 100 mol% is used as the photosensitive silver halide grains. Silver halide other than silver iodide is not particularly limited, and silver chloride, silver bromide The silver bromide is preferable. By using such a high silver iodide emulsion, it is possible to design a preferable heat-developable image recording material in which image storage stability after development processing, in particular, an increase in fog due to light irradiation is remarkably suppressed.
From the viewpoint of image storability after processing, the silver iodide content is more preferably 70 mol% to 100 mol%, further preferably 80 mol% to 100 mol%, and particularly preferably 90 mol% to 100 mol%. preferable. 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 core high silver iodide structure or a shell high silver iodide structure can also be preferably used. A technique for localizing silver bromide on the surface of the grains can also be preferably used.
The grain formation of the photosensitive silver halide emulsion is described in paragraph Nos. 0217 to 0224 of JP-A No. 11-119374, and the grains can be formed by the method described above. It is not something.

Examples of the shape of the silver halide grains include cubes, octahedrons, tetradecahedrons, tabular shapes, spherical shapes, rod shapes, potato shapes, and the like. In the present invention, cubic grains or tabular grains are particularly preferred. The characteristics of the particle shape such as the aspect ratio of the particles and the plane index are the same as those described in paragraph No. 0225 of JP-A-11-119374.
The grain size distribution of the silver halide grains used in the present invention preferably has a monodispersity value of 30% or less, more preferably 1 to 20%, and further preferably 5 to 15%. Here, the monodispersity is defined as a percentage (%) (coefficient of variation) of a value obtained by dividing the standard deviation of the particle size distribution by the average particle size. The grain size of silver halide grains is a ridge length in the case of cubic grains, and the other grains (octahedral, tetradecahedral, flat, etc.) are values represented by a projected area circle equivalent diameter.
The grain size of the high silver iodide grains used in the present invention is preferably 5 nm to 90 nm. A large silver halide grain size increases the amount of silver halide coating required to achieve the required maximum concentration.
When the silver iodide emulsion is applied in a large amount, development is remarkably suppressed, sensitivity is lowered, and density stability with respect to development time is deteriorated. For this reason, the maximum density cannot be obtained in a predetermined development time when the particle size exceeds a certain level. On the other hand, it was also found that if the addition amount is limited, the silver iodide has sufficient developability. In order to achieve a sufficient maximum optical density with a limited addition amount, the size of the silver halide grains needs to be sufficiently small.
The preferred silver halide grain size is 5 nm to 70 nm, more preferably 5 nm to 55 nm. Especially preferably, it is 10 nm-45 nm. The term “particle size” as used herein refers to a straight line when a projected area observed with an electron microscope is converted into a circular image of the same area.
The coating amount of the silver halide grains is preferably 0.001 mol to 1.0 mol, more preferably 0.005 mol to 0.50 mol, still more preferably 0.01 mol to 1 mol of silver of the non-photosensitive organic acid silver salt described later. 0.20 mol.
In order to suppress significant development inhibition by the high silver iodide emulsion, the selection of the addition weight is extremely important.

The silver halide grains used in the present invention are preferably silver halide grains in which a hexacyano metal complex is present on the outermost surface of the grains. 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, and alkylammonium ions (for example, tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, tetra (n-butyl) ammonium ions). .
The addition amount of the hexacyano metal complex is preferably 1 × 10 ⁻⁵ mol to 1 × 10 ⁻² mol, more preferably 1 × 10 ⁻⁴ mol to 1 × 10 ⁻³ mol, per mol of silver.

The photosensitive silver halide grains used in the present invention may contain a metal or metal complex of Group 8 to Group 10 of the Periodic Table (showing Groups 1 to 18). Preferred as the central metal of Group 8 to Group 10 metals or metal complexes of the periodic table are rhodium, ruthenium and iridium. 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. A preferable content is 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol with respect to 1 mol of silver. About these heavy metals and metal complexes and their addition methods, they are described in JP-A-7-225449, JP-A-11-65021, paragraphs 0018 to 0024, and JP-A-11-119374, paragraphs 0227 to 0240. Has been.

Furthermore, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a silver halide emulsion desalting method, and a sensitizing method that can be contained in the silver halide grains used in the present invention, JP-A-11 (1999). Paragraph Nos. 0046 to 0050 of JP-A-84574, paragraph Nos. 0025 to 0031 of JP-A-11-65021, and paragraphs 0242 to 0250 of JP-A-11-119374.
In the present invention, it is preferable to chemically sensitize and use photosensitive silver halide. As a method of chemical sensitization, known methods such as sulfur sensitization method, selenium sensitization method, tellurium sensitization method and noble metal sensitization method can be used, and these can be used alone or in combination. When used in combination, for example, sulfur sensitizing method and gold sensitizing method, sulfur sensitizing method and selenium sensitizing method and gold sensitizing method, sulfur sensitizing method and tellurium sensitizing method and gold sensitizing method, sulfur sensitizing method. It is preferable to combine a sensitizing method, a selenium sensitizing method, a tellurium sensitizing method, a gold sensitizing method, and the like. The amount of selenium sensitizer and tellurium sensitizer used in the selenium sensitization method and tellurium sensitization method can be appropriately selected according to the photosensitive silver halide grains, chemical ripening conditions, etc. About 10 ⁻⁸ to 10 ⁻² mol, preferably about 10 ⁻⁷ to 10 ⁻³ mol can be used per 1 mol of silver. Examples of the noble metal sensitizer used in the noble metal sensitization method include gold sensitizers, platinum sensitizers, palladium sensitizers, iridium sensitizers, and the like, and gold sensitizers are particularly preferable. Specific examples of the gold sensitizer include chloroauric acid, potassium chloroaurate, potassium aurithiocyanate, gold sulfide and the like.
In general, the gold sensitizer can be used in an amount of about 10 ⁻⁷ to 10 ⁻² mol per mol of silver halide.

The photosensitive silver halide can be subjected to reduction sensitization. Specific examples of the compounds used for reduction sensitization include ascorbic acid, thiourea dioxide, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds, and the like. Further, reduction sensitization can be carried out by maintaining the pH of the photosensitive silver halide emulsion at 7 or higher or by ripening with the pAg maintained at 8.3 or lower. Furthermore, reduction sensitization can be performed by introducing a single addition portion of silver ions during grain formation.
The photosensitive silver halide may coexist with a cadmium salt, a sulfite salt, a lead salt, a thallium salt or the like in the process of silver halide grain formation or physical ripening. Moreover, you may add a thiosulfonic acid compound by the method as described in European Patent Publication EP293,917A.
In the present invention, only one kind of photosensitive silver halide may be used, or two or more kinds (for example, those having different average grain sizes, those having different halogen compositions, those having different crystal habits, and conditions for chemical sensitization). Different ones may be used in combination. The amount of the photosensitive silver halide used is preferably 0.1 to 100 mol%, more preferably 0.5 to 50 mol%, and particularly preferably 1.0 to 30 mol% with respect to the molar amount of the organic silver salt.
Various gelatins can be used as the gelatin contained in the photosensitive silver halide emulsion used in the present invention. In order to maintain a good dispersion state of the photosensitive silver halide emulsion in the organic silver salt-containing coating solution, it is preferable to use a low molecular weight gelatin having a molecular weight of 500 to 60,000. These low molecular weight gelatins may be used at the time of particle formation or dispersion after desalting, but are preferably used at the time of dispersion after desalting.

  The reducing agent used in the present invention is a reducing agent for reducing the non-photosensitive organic silver salt. The reducing agent used in the present invention is preferably a hindered phenol compound having at least one phenolic hydroxyl group and having an ortho position substituted with a substituent other than hydrogen. There may be one or more phenol rings in the molecule, but a bis-type hindered phenol compound in which two hindered phenol groups are linked by a methylene group, a methine group, or a thio group is preferred. is there. Specific examples of preferable reducing agents include general formulas (Ia), (Ib), (IIa), (IIb), (III), described in paragraphs 0062 to 0074 of JP-A-9-274274. It is a compound represented by (IVa), (IVb). Specific examples are given below, but the reducing agent that can be used in the present invention is not limited thereto.

The reducing agent may be added to the image forming layer in any state such as a solution, a powder, a solid fine particle dispersion, an emulsion, and an oil protect dispersion. In the case of an aqueous coating solution, it is preferably added as fine particles dispersed in water with an average particle size of 0.01 μm to 10 μm. The solid fine particle dispersion can be performed by a known finer means (ball mill, vibrating ball mill, sand mill, colloid mill, jet mill, roller mill, etc.). A dispersion aid may be used when dispersing the solid fine particles. In the case of an organic solvent coating solution, a reducing agent is dissolved in an organic solvent and used. The reducing agent is desirably used in an amount of 0.01 to 100 mol, more preferably 0.1 to 10 mol, per mol of the organic silver salt in the image forming layer.
In the present invention, a reducing agent may be added to the protective layer in addition to the image forming layer. The reducing agent may be a so-called precursor that is derivatized so as to function effectively only during development.
In the present invention, a non-reducing compound (hereinafter referred to as a hydrogen bonding compound) having a group capable of forming a hydrogen bond with an aromatic hydroxyl group (—OH) is used in combination with a reducing agent. preferable. Examples of the group that forms a hydrogen bond with a hydroxyl group include a phosphoryl group, a sulfoxide group, a sulfonyl group, a carbonyl group, an amide group, an ester group, a urethane group, a ureido group, a tertiary amino group, and a nitrogen-containing aromatic group. 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 a hydrogen atom)), urethane. A group (provided that it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than a hydrogen atom)), a ureido group (provided that it does not have a> N—H group) ,> N-Ra (wherein Ra is a substituent other than a hydrogen atom).
In the present invention, particularly preferably used hydrogen bonding compounds are compounds 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 unsubstituted or substituted. 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, a phosphoryl group, and the like. Preferred as a substituent is an alkyl group or an aryl group, such as a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, -An octyl group, a phenyl group, 4-alkoxyphenyl group, 4-acyloxyphenyl group, etc. are mentioned. Specific examples of the alkyl group represented by 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 tert-butyl group, a tert-amyl group, a tert-octyl group, and a cyclohexyl group. 1-methylcyclohexyl group, benzyl group, phenethyl group, 2-phenoxypropyl group and the like.
Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-tert-butylphenyl group, a 4-tert-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group. As the alkoxy group, methoxy group, ethoxy group, butoxy group, octyloxy group, 2-ethylhexyloxy group, 3,5,5-trimethylhexyloxy group, dodecyloxy group, cyclohexyloxy group, 4-methylcyclohexyloxy group, A benzyloxy group etc. are mentioned.
Examples of the aryloxy group include phenoxy group, cresyloxy group, isopropylphenoxy group, 4-tert-butylphenoxy group, naphthoxy group, biphenyloxy group and the like.
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 the present invention, in order to sufficiently obtain the effect of using a hydrogen bonding compound, at least one of R ^{21 to} R ²³ is preferably an alkyl group or an aryl group, and two or more are an alkyl group or an aryl group. More preferably, it is a group. Further, from the viewpoint that it can be inexpensively available, compound R ²¹ to R ²³ are of the same group are preferred.
Specific examples of the hydrogen bonding compound including the compound of the general formula (D) that can be used in the present invention are shown below, but the hydrogen bonding compound that can be used in the present invention is not limited thereto. .

  Specific examples of the hydrogen bonding compound include those described in JP-A No. 2001-281793 and Japanese Patent Application No. 2000-19481 in addition to the above.

The compound represented by the general formula (D) can be applied in the form of a solution, an emulsified dispersion, or a solid fine particle dispersion in the same manner as the reducing agent.
The hydrogen bonding compound including the compound represented by the general formula (D) forms a hydrogen bonding complex with the compound having a phenolic hydroxyl group in a solution state. Depending on the combination with the compound, it can be isolated in the crystalline state as a complex. The use of the crystal powder isolated in this way as a solid fine particle dispersion is particularly preferable for obtaining stable performance.
Further, a method in which the reducing agent and the compound represented by the general formula (D) are mixed in a powder form and complexed at the time of dispersion with a sand grinder mill or the like using an appropriate dispersant can be preferably used.
The compound represented by the general formula (D) is preferably used in the range of 1 to 200 mol%, more preferably in the range of 10 to 150 mol%, still more preferably 30 to 100 mol based on the molar amount of the reducing agent. % Range.

The non-photosensitive organic silver salt used in the present invention is usually relatively stable to light, and in the presence of a development nucleus (such as a latent image generated by exposure of photosensitive silver halide) and a reducing agent. When heated to about 80 ° C. or higher, a silver image is formed.
The organic silver salt is not particularly limited as long as it is an organic substance containing a reducible silver ion source, but is preferably a silver salt of an organic acid, more preferably a silver salt of an organic compound having a carboxyl group. An organic or inorganic silver complex having a stability constant of 4.0 to 10.0 can also be preferably used.
As a silver salt of an organic compound having a carboxyl group, a silver salt of an aliphatic carboxylic acid, a silver salt of an aromatic carboxylic acid, or the like can be used. The aliphatic carboxylic acid silver salt preferably has 10 to 30 carbon atoms, more preferably 15 to 28 carbon atoms. Preferred examples thereof include silver behenate, silver arachidate, silver stearate, silver oleate, and lauric acid. Examples thereof include silver, silver caproate, silver myristate, silver palmitate, silver maleate, silver fumarate, silver tartrate, silver linoleate, silver butyrate and silver camphorate, and mixtures thereof.
As the organic silver salt, a silver salt of a compound containing a mercapto group or a thione group and derivatives thereof can also be used. Preferred examples of such a silver salt include a silver salt of 3-mercapto-4-phenyl-1,2,4-triazole, a silver salt of 2-mercaptobenzimidazole, and a silver salt of 2-mercapto-5-aminothiadiazole. Silver salt of 2- (ethylglycolamido) benzothiazole, silver salt of thioglycolic acid such as silver salt of S-alkylthioglycolic acid (the alkyl group preferably has 12 to 22 carbon atoms), silver salt of dithioacetic acid, etc. Silver salt of dithiocarboxylic acid, silver salt of thioamide, silver salt of 5-carboxyl-1-methyl-2-phenyl-4-thiopyridine, silver salt of mercaptotriazine, silver salt of 2-mercaptobenzoxazole, US Patent No. 4, 123, 274 silver salts (for example, 1, amino such as 3-amino-5-benzylthio-1,2,4-thiazole silver salt) Silver salt of 2,4-mercaptothiazole derivative), silver salt of 3- (3-carboxyethyl) -4-methyl-4-thiazoline-2-thione described in US Pat. No. 3,301,678, etc. And silver salts of thione compounds.

A compound containing an imino group can also be used as the organic silver salt. Preferred examples thereof include silver salts of benzotriazole and derivatives thereof, silver salts of benzotriazole such as silver methylbenzotriazole, silver salts of halogen-substituted benzotriazole such as silver 5-chlorobenzotriazole, US Pat. No. 4,220. , 709, silver salt of 1,2,4-triazole or 1H-tetrazole, silver salt of imidazole and imidazole derivatives, and the like. In addition, silver acetylide compounds described in US Pat. Nos. 4,761,361 and 4,775,613 can also be used.
The shape of the organic silver salt is not particularly limited, and may be various shapes such as a needle shape, a scale shape, and a lump shape, but is preferably a needle shape or a scale shape. The shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion. In the case of acicular crystals, the minor axis is preferably 0.01 to 0.20 μm, the major axis is preferably 0.10 to 5.0 μm, the minor axis is 0.01 to 0.15 μm, and the major axis is Is more preferably 0.10 to 4.0 μm. The particle size distribution of the organic silver salt is preferably monodispersed.
The organic silver salt is preferably used after desalting. The method for performing the desalting is not particularly limited, and a known filtration method such as circular filtration, suction filtration, ultrafiltration, and floc-forming water washing by a coagulation method can be preferably used.
The amount of the organic silver salt, the area of the image forming layer may preferably be 0.1 to 5.0 g / m ² as silver amount, that the 0.3~2.5g / m ² More preferred.

In the present invention, the binder of the image forming layer is a binder containing a polymer obtained by copolymerizing 10% by mass or more and 70% by mass or less of a monomer represented by the following general formula (M).
General formula (M)
CH ₂ = CR ⁰¹ -CR ⁰² = CH ₂
In the formula, R ⁰¹ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group, and R ⁰² represents an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group.
First, a polymer obtained by copolymerizing 10% by mass or more and 70% by mass or less of the monomer represented by the general formula (M) contained in the binder of the image forming layer of the invention will be described.
In General Formula (M), the alkyl group having 1 to 6 carbon atoms represented by R ⁰¹ and R ⁰² is a preferable alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms. is there. As a halogen atom, a fluorine atom, a chlorine atom, and a bromine atom are preferable, and a chlorine atom is more preferable.
R ⁰¹ and R ⁰² are particularly preferably R ⁰¹ is a hydrogen atom and R ⁰² is a methyl group or a chlorine atom.
Specific examples of the monomer represented by the general formula (M) include 2-ethyl-1,3-butadiene, 2-n-propyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-fluoro-1,3-butadiene, 2,3-dichloro-1,3- Examples thereof include butadiene and 2-cyano-1,3-butadiene.
The copolymerization ratio of the monomer represented by the general formula (M) in the polymer obtained by copolymerizing the monomer represented by the general formula (M) contained in the binder of the present invention is 10 to 70% by mass, preferably Is 15 to 65 mass%, more preferably 20 to 60 mass%.
When the copolymerization ratio of the monomer represented by the general formula (M) is less than 10% by mass, the fusion component of the binder decreases, and the work brittleness deteriorates. On the other hand, when the copolymerization ratio of the monomer represented by the general formula (M) exceeds 70% by mass, the fusion component of the binder is increased and the mobility of the binder is increased, so that the image storage stability is deteriorated.

In the present invention, the other monomer that can be copolymerized with the monomer represented by the general formula (M) is not particularly limited, and any monomer that can be polymerized by a normal radical polymerization or ionic polymerization method is preferably used. It is out. The monomers that can be preferably used can be selected independently and freely in combination from the monomer groups (a) to (j) shown below.
(A) Conjugated dienes: 1,3-butadiene, 1,3-pentadiene, 1-phenyl-1,3-butadiene, 1-α-naphthyl-1,3-butadiene, 1-β-naphthyl-1,3 -Butadiene, 1-bromo-1,3-butadiene, 1-chloro-1,3-butadiene, 1,1,2-trichloro-1,3-butadiene, cyclopentadiene and the like.
(B) Olefin: ethylene, propylene, vinyl chloride, vinylidene chloride, 6-hydroxy-1-hexene, 4-pentenoic acid, methyl 8-nonenoate, vinylsulfonic acid, trimethylvinylsilane, trimethoxyvinylsilane, 1,4- Divinylcyclohexane, 1,2,5-trivinylcyclohexane, etc. (c) α, β-unsaturated carboxylic acid and salts thereof: acrylic acid, methacrylic acid, itaconic acid, maleic acid, sodium acrylate, ammonium methacrylate, itaconic acid Potassium and the like.
(D) α, β-unsaturated carboxylic acid esters: alkyl acrylate (eg, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, etc.), substituted alkyl acrylate (eg, 2-chloro Ethyl acrylate, benzyl acrylate, 2-cyanoethyl acrylate, etc.), alkyl methacrylate (eg, methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, etc.), substituted alkyl methacrylate (eg, 2-hydroxyethyl methacrylate, Glycidyl methacrylate, glycerin monomethacrylate, 2-acetoxyethyl methacrylate, tetrahydrofurfuryl meta Chryrate, 2-methoxyethyl methacrylate, polypropylene glycol monomethacrylate (number of added polyoxypropylene = 2 to 100), 3-N, N-dimethylaminopropyl methacrylate, chloro-3-N, N, N-trimethyl Ammoniopropyl methacrylate, 2-carboxyethyl methacrylate, 3-sulfopropyl methacrylate, 4-oxysulfobutyl methacrylate, 3-trimethoxysilylpropyl methacrylate, allyl methacrylate, 2-isocyanatoethyl methacrylate, etc.), unsaturated dicarboxylic acid derivatives (Eg, monobutyl maleate, dimethyl maleate, monomethyl itaconate, dibutyl itaconate, etc.), polyfunctional esters (eg, ethylene glycol diacrylate) Ethylene glycol dimethacrylate, 1,4-cyclohexanediacrylate, pentaerythritol tetramethacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, dipentaerythritol pentamethacrylate, pentaerythritol hexaacrylate, 1,2, 4-cyclohexanetetramethacrylate and the like.

(E) Amides of β-unsaturated carboxylic acids: acrylamide, methacrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-methyl-N-hydroxyethylmethacrylamide, N-tertbutylacrylamide, N-tert Octyl methacrylamide, N-cyclohexyl acrylamide, N-phenyl acrylamide, N- (2-acetoacetoxyethyl) acrylamide, N-acryloylmorpholine, diacetone acrylamide, itaconic acid diamide, N-methylmaleimide, 2-acrylamido-methylpropane (F) Unsaturated nitriles: acrylonitrile, methacrylonitrile, etc., such as sulfonic acid, methylenebisacrylamide, dimethacryloylpiperazine and the like.
(G) Styrene and its derivatives: styrene, vinyl toluene, p-tertbutyl styrene, vinyl benzoic acid, methyl vinyl benzoate, α-methyl styrene, p-chloromethyl styrene, vinyl naphthalene, p-hydroxymethyl styrene, p- Styrene sulfonic acid sodium salt, p-styrene sulfinic acid potassium salt, p-aminomethylstyrene, 1,4-divinylbenzene and the like.
(H) Vinyl ethers: methyl vinyl ether, butyl vinyl ether, methoxyethyl vinyl ether, and the like.
(I) Vinyl esters: vinyl acetate, vinyl propionate, vinyl benzoate, vinyl salicylate, vinyl chloroacetate and the like.
(J) Other polymerizable monomers: N-vinylimidazole, 4-vinylpyridine, N-vinylpyrrolidone, 2-vinyloxazoline, 2-isopropenyloxazoline, divinylsulfone, and the like.

In the present invention, preferred examples of the polymer obtained by copolymerizing the monomer represented by the general formula (M) include copolymers with styrene (for example, random copolymers, block copolymers, etc.), styrene and butadiene. Copolymer (eg, random copolymer, butadiene-isoprene-styrene block copolymer, styrene-butadiene-isoprene-styrene block copolymer), copolymer with ethylene-propylene, copolymer with acrylonitrile Polymers, copolymers with isobutylene, copolymers with acrylic esters (eg, acrylic esters such as ethyl acrylate and butyl acrylate), and copolymers with acrylic esters and acrylonitrile (The same acrylic ester can be used as mentioned above) Among this, a copolymer of styrene are most preferred.
Further, the polymer of the present invention is preferably a copolymer obtained by copolymerizing a monomer having an acid group with these compositions. As the acid group, carboxylic acid, sulfonic acid, and phosphoric acid are preferable. The copolymerization ratio of the acid group is preferably 1 to 20% by mass, more preferably 1 to 10% by mass.
Specific examples of the monomer having an acid group include acrylic acid, methacrylic acid, itaconic acid, p-styrenesulfonic acid sodium salt, isoprenesulfonic acid, phosphorylethyl methacrylate and the like.

  In the binder of the present invention, any polymer may be used in combination with a polymer obtained by copolymerizing the monomer represented by the general formula (M). The polymer that can be used in combination is preferably transparent or translucent and colorless. Natural resins, polymers and copolymers, synthetic resins, polymers and copolymers, and other media forming films such as gelatins, poly ( Vinyl alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride) , Poly (methacrylic acid) s, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, poly (vinyl acetal) s (for example, poly (vinyl formal), Poly (vinyl butyral)), poly (d Ter), poly (urethane), phenoxy resin, poly (vinylidene chloride), poly (epoxide), poly (carbonate), poly (vinyl acetate), poly (olefin), poly (amide) There is.

The binder of the present invention preferably has a glass transition temperature (Tg) in the range of −30 ° C. to 70 ° C., more preferably in the range of −10 ° C. to 50 ° C., more preferably in view of processing brittleness and image storage stability. It is in the range of 0 ° C to 40 ° C. Two or more kinds of polymers can be blended and used as the binder. In this case, it is preferable that the weighted average Tg falls within the above range in consideration of the composition. In the case of phase separation or having a core-shell structure, the weighted average Tg is preferably in the above range.
The glass transition temperature (Tg) of a polymer in which n monomer components from i = 1 to n are copolymerized can be calculated by the following formula.
1 / Tg = Σ (Xi / Tgi)
Here, Xi is the weight fraction (ΣXi = 1) of the i-th monomer, and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ means taking the sum from i = 1 to n.
The glass transition temperature value (Tgi) of the homopolymer of each monomer was the value of polymer handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

The polymer used in the binder of the present invention can be easily obtained by a solution polymerization method, suspension polymerization method, emulsion polymerization method, dispersion polymerization method, anionic polymerization method, cationic polymerization method, etc. Legal is most preferred. The emulsion polymerization method uses, for example, water or a mixed solvent of water and an organic solvent miscible with water (for example, methanol, ethanol, acetone, etc.) as a dispersion medium, and is 5 to 150% by mass with respect to the dispersion medium. Using a monomer mixture, an emulsifier and a polymerization initiator, polymerization is carried out with stirring at about 30 to 100 ° C., preferably 60 to 90 ° C. for 3 to 24 hours. Moreover, it is also preferable to use a dispersing agent etc. as needed.
In the emulsion polymerization, various conditions such as a dispersion medium, a monomer concentration, a polymerization initiator amount, an emulsifier amount, a dispersant amount, a reaction temperature, and a monomer addition method are appropriately set in consideration of the type of monomer to be used.
The emulsion polymerization method can be generally performed according to the following literature.
"Synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki, published by Polymer Press (1978))", "Application of Synthetic Latex (Takaaki Sugimura, Tatsuo Kataoka, Junichi Suzuki, Keiji Kasahara, Published by Polymer Press (1993) ) "
“Synthetic Latex Chemistry (by Soichi Muroi, published by Kobunshi Shuppankai (1970))”.
In the emulsion polymerization method, a batch polymerization method, a monomer (continuous / divided) addition method, an emulsion addition method, a seed polymerization method, etc. can be selected. From the viewpoint of latex productivity, the batch polymerization method, monomer (continuous / divided) ) The addition method and the emulsion addition method are preferred.

The polymerization initiator to be used is not limited as long as it has radical generating ability, such as inorganic peroxides such as persulfate and hydrogen peroxide, peroxides described in the organic peroxide catalog of Nippon Oil & Fats, and Wako Pure Chemical Industries, Ltd. The azo compounds described in the catalog of azo polymerization initiators, etc. can be used. Among them, water-soluble peroxides such as persulfate and water-soluble azo compounds described in the azo polymerization initiator catalog of Wako Pure Chemical Industries, Ltd. are preferable. Ammonium persulfate, sodium persulfate, potassium persulfate, azobis (2-Methylpropionamidine) hydrochloride, azobis (2-methyl-N- (2-hydroxyethyl) propionamide), azobiscyanovaleric acid is more preferable, and in particular, persulfate such as ammonium persulfate, sodium persulfate, potassium persulfate and the like. Oxides are preferred from the viewpoints of image storage stability, solubility, and cost.
The addition amount of the polymerization initiator is preferably 0.3% by mass to 2.0% by mass, more preferably 0.4% by mass to 1.75% by mass with respect to the total amount of monomers. 5 mass%-1.5 mass% are especially preferable.

As the emulsifier, any of an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used, but the anionic surfactant is used from the viewpoint of dispersibility and image preservability. Preferably, a sulfonic acid type anionic surfactant is more preferable because polymerization stability is ensured in a small amount and hydrolysis resistance is obtained, and a long-chain alkyldiphenyl ether disulfone represented by Perex SS-H (Kao Co., Ltd.). Acid salts are more preferable, and a low electrolyte type such as Pionine A-43-S (Takemoto Yushi Co., Ltd.) is particularly preferable.
When the sulfonic acid type anionic surfactant is used as the emulsifier, it is preferably used in an amount of 0.1% by mass to 10.0% by mass with respect to the total amount of monomers, and 0.2% by mass to 7.5% by mass. It is more preferable that 0.3% by mass to 5.0% by mass is used.
In the synthesis of the polymer latex used in the present invention, it is preferable to use a chelating agent. A chelating agent is a compound capable of coordinating (chelating) multivalent ions such as metal ions such as iron ions and alkaline earth metal ions such as calcium ions. Japanese Patent Publication No. 6-8956, US Pat. No. 5,053,322 JP-A-4-73645, JP-A-4-127145, JP-A-4-247703, JP-A-4-305572, JP-A-6-11805, JP-A-5-173712, JP-A-5-66527, JP-A-5-158195, JP-A-6-118580, JP-A-6-110168, JP-A-6-161054, JP-A-6-175299, JP JP-A-6-214352, JP-A-7-114161, JP-A-7-114154, JP-A-7-120894. JP-A-7-199433, JP-A-7-306504, JP-A-9-43792, JP-A-8-314090, JP-A-10-182571, JP-A-10-182570, The compounds described in JP-A-11-190892 can be used.

  Examples of the chelating agent include inorganic chelate compounds (sodium tripolyphosphate, sodium hexametaphosphate, sodium tetrapolyphosphate, etc.), aminopolycarboxylic acid chelate compounds (nitrilotritriacetic acid, ethylenediaminetetraacetic acid, etc.), organic phosphonic acid chelate compounds ( Research Disclosure (hereinafter also referred to simply as RD) No. 18170, JP-A-52-102726, 53-42730, 56-97347, 54-121127 55-4024, 55-4025, 55-29883, 55-126241, 55-65555, 55-65956, 57-179843, 54-6 125 and JP West German compounds such as those described in Patent No. 1,045,373), polyphenol-based chelating agent is preferably such as polyamine-based chelate compounds, with aminopolycarboxylic acid derivatives being particularly preferred.

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

The addition amount of the chelating agent is preferably 0.01% by mass to 0.4% by mass, more preferably 0.02% by mass to 0.3% by mass, and 0.03% by mass to 0.00% by mass with respect to the total amount of monomers. 15% by mass is particularly preferred.
A chain transfer agent is preferably used for the synthesis of the polymer latex used in the present invention. As the chain transfer agent, those described in polymer handbook, 3rd edition, (Wiley-Interscience, 1989) are preferable. Sulfur compounds are more preferred because they have a high chain transfer ability and can be used in small amounts. Hydrophobic mercaptan-based chain transfer agents such as tert-dodecyl mercaptan and n-dodecyl mercaptan are particularly preferred.
The amount of the chain transfer agent is preferably 0.2% by mass to 2.0% by mass, more preferably 0.3% by mass to 1.8% by mass, and 0.4 mass% to 1.% by mass based on the total amount of monomers. 6% by mass is particularly preferred.
In emulsion polymerization, in addition to the above compounds, electrolytes, stabilizers, thickeners, antifoaming agents, antioxidants, vulcanizing agents, antifreezing agents, gelling agents, vulcanization accelerators and the like described in synthetic rubber handbooks, etc. These additives may be used.
Specific examples of the polymer used in the present invention include the following exemplary compounds (P-1) to (P-29), but the polymer used in the present invention is not limited to these exemplary compounds.
X, y, z, and z ′ in the chemical formula indicate a mass ratio of the polymer composition, and the total sum of x, y, z, and z ′ is 100%. Tg represents the glass transition temperature of the dry film obtained from the polymer.

Although the synthesis example of the polymer used for this invention is shown below, this synthesis example does not limit the synthesis method of the polymer used for this invention.
Other exemplary compounds can also be synthesized by the same synthesis method.
(Synthesis Example 1-Synthesis of Exemplified Compound P-1)
Add 1500g of distilled water to the polymerization kettle of the gas monomer reactor (Pressure Glass Industry Co., Ltd. TAS-2J type), heat at 90 ° C for 3 hours, and passivate to the stainless steel surface of the polymerization kettle and members of the stainless steel stirrer A film is formed. In this polymerization kettle, 584.86 g of distilled water bubbled with nitrogen gas for 1 hour, 9.45 g of surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)), 1 mol / L NaOH 20.25 g, ethylenediaminetetraacetic acid tetrasodium salt 0.216 g, styrene 332.1 g, isoprene 191.7 g, acrylic acid 16.2 g, tert-dodecyl mercaptan 4.32 g, the polymerization kettle was sealed, and the stirring speed was 225 rpm. The mixture was stirred and heated to an internal temperature of 60 ° C. A solution prepared by dissolving 2.7 g of ammonium persulfate in 50 ml of water was added thereto, and the mixture was stirred as it was for 7 hours. The temperature was further raised to 90 ° C. and the mixture was stirred for 3 hours. After the reaction was completed, the internal temperature was lowered to room temperature, and the obtained polymer was filtered with a filter cloth (mesh: 225). 1145 g (45% by mass solid content, particle size 112 nm) was obtained.

(Synthesis Example 2-Synthesis of Exemplified Compound P-2)
In a gas monomer reaction apparatus (TAS-2J type manufactured by Pressure Glass Co., Ltd.), a passive film was formed in the same manner as in Synthesis Example 1 above, and 350.92 g of distilled water in which nitrogen gas was bubbled for 1 hour, a surfactant (Pionine) A-43-S (manufactured by Takemoto Yushi Co., Ltd.)) 3.78 g, 20.25 g of 1 mol / L NaOH, 0.216 g of ethylenediaminetetraacetic acid tetrasodium salt, 34.02 g of styrene, 18.36 g of isoprene, acrylic acid 1.62 g and 2.16 g of tert-dodecyl mercaptan were added, the polymerization kettle was sealed, stirred at a stirring speed of 225 rpm, and the temperature was raised to an internal temperature of 65 ° C. A solution prepared by dissolving 1.35 g of ammonium persulfate in 50 ml of water was added thereto and stirred as it was for 2 hours. Separately, 233.94 g of distilled water, 5.67 g of a surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)), 306.18 g of styrene, 165.24 g of isoprene, 14.58 g of acrylic acid, tert-dodecyl 2.16 g of mercaptan and 1.35 g of ammonium persulfate were added and stirred to prepare an emulsion, which was added to the reaction vessel over 8 hours. After completion of the addition, the mixture was further stirred for 2 hours. The temperature was further raised to 90 ° C. and stirred for 3 hours. After the reaction was completed, the internal temperature was lowered to room temperature, and the obtained polymer was filtered with a filter cloth (mesh: 225). (Solid content 45% by mass, particle size 121 nm) was obtained.

(Synthesis Example 3-Synthesis of Exemplified Compound P-4)
In a gas monomer reaction apparatus (TAS-2J type manufactured by Pressure Glass Industry Co., Ltd.), a passive film was formed in the same manner as in Synthesis Example 1 above, and 578.11 g of distilled water in which nitrogen gas was bubbled for 1 hour, a surfactant (Perex) SS-H (manufactured by Kao Corporation)) 16.2 g, 20.25 g of 1 mol / L NaOH, 0.216 g of ethylenediaminetetraacetic acid tetrasodium salt, 321.3 g of styrene, 202.5 g of isoprene, 16.2 g of acrylic acid Then, 4.32 g of tert-dodecyl mercaptan was added, the polymerization kettle was sealed and stirred at a stirring speed of 225 rpm, and the temperature was raised to an internal temperature of 60 ° C. A solution prepared by dissolving 2.7 g of ammonium persulfate in 25 ml of water was added thereto and stirred as it was for 5 hours. Further, a solution prepared by dissolving 1.35 g of ammonium persulfate in 25 ml of water was added, and the mixture was heated to 90 ° C. and stirred for 3 hours. After the completion of the reaction, the internal temperature was lowered to room temperature, and then the obtained polymer was filtered with a filter cloth (mesh: 225), and 1139 g of Exemplified Compound P-4 (solid content: 45 mass%, particle size: 105 nm) was obtained. Obtained.

An aqueous solvent can be used for the polymer latex used in the present invention, but a water-miscible organic solvent may be used in combination.
Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethyl acetate and dimethylformamide. The amount of these organic solvents added is preferably 50% or less, more preferably 30% or less of the solvent.
The polymer concentration of the polymer latex of the present invention is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and particularly preferably 30 to 55% by mass.
The binder polymer of the present invention preferably has an equilibrium water content of 2% by mass or less at 25 ° C. and 60% RH. More preferably, the equilibrium moisture content is 0.01% by mass or more and 1.5% by mass or less, and further preferably 0.02% by mass or more and 1.0% by mass or less.
“Equilibrium water content at 25 ° C. and 60% RH” means the weight W1 of the polymer in the humidity-controlled equilibrium under the atmosphere of 25 ° C. and 60% RH and the weight W0 of the polymer in the absolutely dry state at 25 ° C. The moisture content calculated in this way is said.
Equilibrium moisture content at 25 ° C. and 60% RH = [(W1-W0) / W0] × 100 (mass%)
For the definition and measurement method of the equilibrium moisture content, for example, Polymer Engineering Course 14, Polymer Material Testing Method (Edited by the Society of Polymer Science, Jinjin Books) can be referred to.

In the present invention, a polymer dispersible in an aqueous solvent is particularly preferred. The dispersion state may be any of latex in which fine particles of a water-insoluble hydrophobic polymer are dispersed and polymer molecules are dispersed in a molecular state or in the form of micelles, but latex-dispersed particles are more preferable. The average particle diameter of the dispersed particles is 1 to 50000 nm, preferably 5 to 1000 nm, more preferably 10 to 500 nm, and still more preferably 50 to 200 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution. Mixing two or more types having a monodispersed particle size distribution is also a preferable method for controlling the physical properties of the coating solution.
If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose may be added to the image forming layer of the present invention. The amount of these hydrophilic polymers added is 30% by mass or less, more preferably 20% by mass or less, based on the total binder of the image forming layer.
The image forming layer of the present invention is preferably formed using a polymer latex. The amount of binder in the image forming layer is such that the weight ratio of total binder / organic silver salt is 1/10 to 10/1, more preferably 1/3 to 5/1, and still more preferably 1/1 to 3/1. Range.
The weight ratio of the total binder / photosensitive silver halide in the image forming layer is in the range of 400 to 5, more preferably 200 to 10.
The total binder amount in the image forming layer of the present invention is preferably in the range of 0.2 to 30 g / m ² , more preferably 1 to 15 g / m ² , and still more preferably ² to 10 g / m ² . The image forming layer of the present invention may contain a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like.

The halogen precursor used in the present invention is a compound capable of releasing halogen by heat, light or the like.
The halogen precursor used in the present invention is preferably an organic polyhalide having two or more halogen atoms on the same carbon atom. Examples thereof include JP-A-50-119624 and JP-A-50-120328. 51-121332, 54-58022, 56-70543, 56-99335, 59-90842, 61-129642, 62-129845, Special No. 6-208191, No. 6-208193, No. 7-5621, No. 7-2781, No. 8-15809, US Pat. No. 5,340,712, No. 5 No. 3,369,000, No. 5,464,737, and the like.
Two or more types of halogen precursors may be used in combination.

The halogen precursor can be dissolved in water or a suitable organic solvent, added to the coating solution, dried, and then allowed to exist in a microcrystalline state in the film. As the organic solvent, alcohols (methanol, ethanol, propanol, fluorinated alcohol, etc.), ketones (acetone, methyl ethyl ketone, etc.), dimethylformamide, dimethyl sulfoxide, methyl cellosolve, etc. can be used.
Further, according to the well-known emulsion dispersion method, the halogen precursor is dissolved directly in oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate, diethyl phthalate or in an auxiliary solvent such as ethyl acetate or cyclohexanone. It may be added and mechanically dispersed to prepare an emulsified dispersion and added to the coating solution. In addition, using a dispersion medium such as glass beads, zirconia beads, zircon silicate beads, or the like with a known dispersion machine such as a ball mill, a colloid mill, or a sand mill, or a dispersion machine using ultrasonic waves, the halogen precursor is appropriately mixed with water or the like. A fine solid dispersion may be prepared by dispersing in an appropriate solvent and added to the coating solution.

The halogen precursor is preferably added as fine particles dispersed in water. When a fine solid dispersion is prepared and added in advance, it can be stably added with a uniform particle size, so that aggregation does not occur in the coating liquid and performance does not fluctuate. When an aqueous dispersion of a thermoplastic resin is used as a binder, it is particularly preferable to add it as a solid dispersion. The average particle size of the halogen precursor particles in the solid dispersion is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm.
In the case of high-contrast image formation, the addition amount of the halogen precursor is an important factor, and it is preferably added in an amount of 0.1 mol or less with respect to 1 mol of the non-photosensitive organic silver salt of the image forming layer, particularly 1 × 10 ^{−4 to} 0 .05 mol is more preferred. If the amount added exceeds this range, a high-contrast image cannot be obtained, and if it is too small, fogging of the image tends not to be sufficiently suppressed.
The halogen precursor may be added not only to the image forming layer but also to an undercoat layer, an intermediate layer and a protective layer described later.

A silver carrier is preferably used for the heat-developable image recording material of the present invention. The silver carrier has been referred to as a “coloring agent” that has been conventionally used to promote development in the field of a thermally developed image recording system called a dry silver system. These “toning agents” act on non-photosensitive organic silver during thermal development to form a diffusible silver complex, which is transported to the latent image nucleus and assists in the physical development using the latent image nucleus as a catalyst. It is called a silver carrier because it has.
The silver carrier is added to any layer on the side having the image forming layer of the support. The addition amount is preferably 0.1 to 50 mol%, more preferably 0.5 to 20 mol%, based on the molar amount of the non-photosensitive organic silver. Further, the silver carrier may be added as a precursor derivatized so as to have an effective function only during development.
Silver carriers are disclosed in JP-A-46-6077, JP-A-47-10282, JP-A-49-5019, JP-A-49-5020, JP-A-49-91215, JP-A-50-2524, JP-A-50. No. -32927, No. 50-67132, No. 50-67641, No. 50-114217, No. 51-3223, No. 51-27923, No. 52-14788, No. 52-. No. 99813, No. 53-1020, No. 53-76020, No. 54-156524, No. 54-156525, No. 61-183642, JP-A-4-56848, Japanese Patent Publication No. 49. No. -10727, 54-20333, US Pat. No. 3,080,254, US Pat. No. 3,446,648, US Pat. No. 3,782,941, No. 4,123,282, No. 4,510,236, British Patent No. 1,380,795, Belgian Patent No. 841,910 It is disclosed as a toning agent in the specification and the like.

  Specific examples of the silver carrier include phthalimide and N-hydroxyphthalimide; succinimide, pyrazolin-5-one, quinazolinone, 3-phenyl-2-pyrazolin-5-one, 1-phenylurazole, quinazoline, 2,4- Cyclic imides such as thiazolidinedione; naphthalimides such as N-hydroxy-1,8-naphthalimide; cobalt complexes such as cobalt hexamine trifluoroacetate; 3-mercapto-1,2,4-triazole, 2,4-dimercapto Mercaptans such as pyrimidine, 3-mercapto-4,5-diphenyl-1,2,4-triazole, 2,5-dimercapto-1,3,4-thiadiazole; (N, N-dimethylaminomethyl) phthalimide, N, N- (dimethylaminomethyl) -naphthalene-2,3 N- (aminomethyl) aryl dicarboximide such as dicarboximide; photobleaching agents such as blocked pyrazole and isothiuronium derivatives (N, N′-hexamethylenebis (1-carbamoyl-3,5-dimethylpyrazole), 1 , 8- (3,6-diazaoctane) bis (isothiuronium trifluoroacetate), 2- (tribromomethylsulfonyl) -benzothiazole, etc.); 3-ethyl-5-[(3-ethyl-2-thiazolinylidene) -1-methylethylidene] -2,2,4-oxazolidinedione; 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone, 2,3-dihydro-1,4- Phthalazine dione. Phthalazinones and their derivatives or metal salts such as derivatives thereof; combinations of phthalazinone and phthalic acid derivatives (phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride, etc.); 4- (1-naphthyl) Phthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine, 6-isopropylphthalazine, 6-isobutylphthalazine, 6-tert-butylphthalazine, 5,7-dimethylphthalazine, 2,3-dihydrophthal Phthalazines such as azine and derivatives or metal salts thereof; combinations of phthalazine or its derivatives and phthalic acid derivatives (phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride, etc.); quinazolinedione, benzoxazine and Naphthoxazine derivatives; hexachlorolodium Rhodium complexes that function not only as color control agents, but also as halide ion sources for the formation of silver halides, such as ammonium (III) oxalate, rhodium bromide, rhodium nitrate and potassium hexachlororhodium (III); Inorganic peroxides and persulfates such as ammonium disulfide and hydrogen peroxide; 1,3-benzoxazine 2,4-dione, 8-methyl-1,3-benzoxidine-2,4-dione, 6-nitro- Benzoxazine-2,4-diones such as 1,3-benzxazine-2,4-dione; Pyrimidines and asymmetric triazines such as 2,4-dihydroxypyrimidine and 2-hydroxy-4-aminopyrimidine; 3,6-dimercapto -1,4-diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene, 1,4-di (o-chloroph Yl) -3,6-dimercapto -1H, 4H-2,3a, 5,6a- tetraaza Bae azauracil and tetraazapentalene derivatives such Ntaren like.

Particularly preferred is a combination of phthalazine or a derivative thereof and a phthalic acid derivative (phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride, etc.).
These silver carriers are preferably added as an aqueous solution, but in the case of being insoluble in water, they may be added in any state such as a methanol solution, powder, solid fine particle dispersion or the like. The solid fine particle dispersion can be performed by a known finer means (ball mill, vibrating ball mill, sand mill, colloid mill, jet mill, roller mill, etc.). A dispersion aid may be used when dispersing the solid fine particles.

Hereinafter, other additives that can be used in the heat-developable image recording material of the present invention will be described. These additives can be added to, for example, an intermediate layer, a protective layer, a back layer, and an undercoat layer other than the image forming layer and the image forming layer.
(A) Dispersion stabilizer Normally, a dispersion stabilizer is added at the time of preparation of a dispersion, and is further added at the time of preparation of a coating solution. An example of the dispersion stabilizer is a hydrophilic polymer, and preferable hydrophilic polymers include polyvinyl alcohol, methylcellulose, hydroxypropylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose and the like. The addition amount of the hydrophilic polymer is preferably 70% by mass or less, and more preferably 50% by mass or less, based on the solid content of the dispersion. The lower limit of the addition amount is not particularly limited, but is usually about 1% by mass.
A surfactant can also be used as a dispersion stabilizer. The addition amount of the surfactant is preferably 50% by mass or less, and more preferably 30% by mass or less, based on the solid content of the dispersion. The lower limit of the addition amount is not particularly limited, but is usually about 1% by mass.
(B) Surfactant for improving coatability When preparing the heat-developable image recording material of the present invention, a surfactant for improving coatability can be used. These surfactants may be any of nonionic surfactants, anionic surfactants, fluorosurfactants and the like. Specifically, fluoropolymer surfactants described in JP-A-62-170950, US Pat. No. 5,380,644, etc., JP-A-60-244945, JP-A-63. -188135, etc., polysiloxane surfactants described in US Pat. No. 3,885,965, etc., polyalkylene oxides described in JP-A-6-301140, etc. Or an anionic surfactant can be used.

(C) Fluorine-containing surfactant It is preferable to add a fluorine-containing surfactant to the heat-developable image recording material of the present invention because good antistatic properties can be obtained. Although it can add to arbitrary layers, adding to an outermost layer is especially preferable.
Examples of preferred fluorine-containing surfactants include a fluoroalkyl group, a fluoroalkenyl group or a fluoroaryl group having 4 or more (usually 15 or less) carbon atoms, and an anionic group (sulfonic acid group, sulfuric acid group, Carboxylic acid groups, phosphoric acid groups, salts derived therefrom, etc.), cationic groups (amine salts, ammonium salts, aromatic amine salts, sulfonium salts, phosphonium salts, etc.), betaine groups (carboxyamine salts, carboxyammonium salts, And a surfactant having a nonionic group (such as a substituted or unsubstituted polyoxyalkylene group, polyglyceryl group or sorbitan residue). Examples of the fluorine-containing surfactant that can be used in the present invention include JP-A-49-10722, British Patent 1,330,356, US Pat. No. 4,335,201, No. 347.308, British Patent No. 1,417.915, Japanese Patent Laid-Open Nos. 55-149938, 58-196544, British Patent 1.439,402, etc. Has been.
Two or more kinds of fluorine-containing surfactants may be mixed and used. The amount of the fluorine-containing surfactant used is preferably 0.0001 to 1 g, more preferably 0.0002 to 0.25 g, particularly preferably 0.0003 to 0.1 g per 1 m ² of the image recording material.

(D) Dye and Material In addition to the dye of the present invention, a dye or a pigment may be added to any layer of the heat-developable image recording material of the present invention for the purpose of adjusting the color tone or preventing irradiation. Although these dyes and pigments are not particularly limited, for example, those described in the color index can be used. Specific examples thereof include pyrazoloazole dyes, anthraquinone dyes, azo dyes, azomethine dyes, oxonol dyes, carbocyanine dyes, styryl. Examples include dyes, triphenylmethane dyes, indoaniline dyes, indophenol dyes, phthalocyanine and other organic facials, and inorganic facials. Among them, anthraquinone dyes (compounds 1 to 9 described in JP-A-5-341441, compounds 3-6 to 18 and 3-23 to 38 described in JP-A-5-165147), azomethine dyes (JP Compounds 17 to 47 described in JP-A-5-341441), indoaniline dyes (compounds 11 to 19 described in JP-A-5-289227, compound 47 described in JP-A-5-341441, and JP-A-5 And compounds 2-10 to 11 described in JP-A No. 165147) and azo dyes (compounds 10 to 16 described in JP-A No. 5-341441) can be preferably used.
The amount of dye and facial used may be selected so as to obtain the desired amount of light absorption, but generally the optical absorption density at the exposure wavelength is 0.1 to 2.0, preferably 0.8. It is added so that it may become 2-1.0. The dye and pigment may be added in any state, such as in the form of a solution, emulsion, solid fine particle dispersion, or mordanted in a polymer mordant. If the dye and pigment are water-soluble substances, they may be added as an aqueous solution. If it is a water-insoluble substance, it is preferably added as a solid fine particle dispersion using water as a dispersion medium, and added to the image forming layer, the layer between the image forming layer and the support, or the protective layer. .

(E) Sensitizing dye A sensitizing dye can be used in the present invention. The sensitizing dye is not particularly limited as long as it can spectrally sensitize the photosensitive silver halide grains in a desired wavelength region when adsorbed on the photosensitive silver halide grains. A cyanine dye, a merocyanine dye, a complex cyanine dye, Complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes and the like can be used.
Sensitizing dyes described in RESEARCH DISCLOSURE ITem 17643 IVA (December 1978, page 23), Item 1831X (August 1979, page 437) and the references cited therein can also be used in the present invention. A preferred sensitizing dye is one capable of spectrally sensitizing silver halide grains in a wavelength region of 500 nm or less when adsorbed on silver halide grains, and a sensitizing dye having spectral sensitivity suitable for the spectral characteristics of the exposure light source. It can be advantageously selected. These sensitizing dyes may be used alone or in combination of two or more.
Of these sensitizing dyes, sensitizing dyes represented by the general formula [1] and the general formula [2] are preferably used.

In general formula [1], Z ¹ and Z ² are each independently unsubstituted or pyrroline substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group. Ring, thiazoline ring, thiazole ring, benzothiazole ring, naphthothiazole ring, selenazole ring, benzoselenazole ring, naphthoselenazole ring, oxazole ring, benzoxazole ring, naphthoxazole ring, imidazole ring, benzoimidazole ring or pyridine Represents a group of non-metallic atoms necessary to form a ring, R ¹¹ and R ¹² each independently represents an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, a carboxyalkyl group or a sulfoalkyl group, and n1 and n2 Represents 0 or 1, X represents an anion, and n represents 1 or 2.
The nonmetallic atom groups represented by Z ¹ and Z ² may be the same or different from each other. Examples of the benzothiazole ring formed by the nonmetallic atom groups of Z ¹ and Z ² include benzo Thiazole, 5-chlorobenzothiazole, 5-methylbenzothiazole, 5-methoxybenzozothiazole, 5-hydroxybenzothiazole, 5-hydroxy-6-methylbenzothiazole, 5,6-dimethylbenzothiazole, 5-ethoxy-6 Examples thereof include methyl benzothiazole, 5-henyl benzothiazole, 5-carboxy benzothiazole, 5-ethoxycarbonylbenzothiazole, 5-dimethylamino benzothiazole, and 5-acetylamino benzothiazole.
Examples of the benzoselenazole ring include benzoselenazole, 5-chlorobenzozoselenazole, 5-methylbenzozolenazole, 5-methoxybenzozoselenazole, 5-hydroxybenzozoselazole, 5,6-dimethylbenzoselenazole, and 5,6-dimethoxy. Examples include benzoselenazole, 5-ethoxy-6-methylbenzoselenazole, 5-hydroxy-6-methylbenzoselenazole, and 5-henylbenzoselenazole. Examples of the naphthothiazole ring include β-naphthothiazole, β, β -Naphthothiazole etc. are mentioned, As a naphthoselenazole ring, (beta) -naphthoselenazole etc. are mentioned, for example.

  Examples of the pyrroline ring include pyrroline and 1-methylpyrroline. Examples of the thiazoline ring include thiazoline and 4-methylthiazoline. Examples of the thiazole ring include thiazole and 4-methyl. Thiazole, 4-phenylthiazole, 4,5-dimethylthiazole, 4-methyl-5-phenylthiazole and the like. Examples of the selenazole ring include selenazole, 4-methylselenazole, 4-phenylselenazole, 4, Examples of the oxazole ring include oxazole, 4-methyl oxazole, 5-methyl oxazole, 4,5-dimethyl oxazole, 4-p-tolyl oxazole, and the like, and benzoxazole ring. For example, Nzooxazole, 5-fluorobenzoxazole, 5-chlorobenzoxazole, 5-bromobenzoxazole, 5-trifluoromethylbenzoxazole, 5-methylbenzoxazole, 5-methyl-8- Phenylbenzoxazole, 5,6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5,6-dimethoxybenzoxazole, 5-phenylbenzoxazole, 5-carboxybenzoxazole, 5-methoxycarbonylbenzoxazole, 5-acetyl Examples of the naphthoxazole ring include β-naphthoxazole, and examples of the imidazole ring include 1-methylimidazole, 1-ethylimidazole, and 1-phenylimidazole. Examples of the benzimidazole ring include 1-methylbenzimidazole, 1-phenylbenzimidazole, 5-chloro-1-ethylbenzimidazole, 5-trichloromethyl-1-ethylbenzimidazole, 5,6- Dichloro-1-ethylbenzimidazole, 5,6-dichloro-1-phenylbenzimidazole, 5-methoxycarbonyl-1-ethylbenzimidazole, 5-N, N-dimethylcarbamoyl-1-methylbenzimidazole, 5-N, N-diethylsulfamoyl-1-phenylbenzimidazole, 5-cyano-1-ethylbenzimidazole, 5-cyano-1-β-hydroxyethylbenzimidazole and the like can be mentioned. Examples of the pyridine ring include pyridine, 5 -Methylpyridine, etc. And the like.

Specific examples of the alkyl group having 1 to 4 carbon atoms, the hydroxyalkyl group, the carboxyalkyl group, or the sulfoalkyl group represented by R ¹¹ and R ¹² include, for example, a methyl group, an ethyl group, and an n-propyl group. Examples include alkyl groups, β-hydroxyethyl groups, β-carboxyethyl groups, γ-carboxypropyl groups, γ-sulfopropyl groups, γ-sulfobutyl groups, δ-sulfobutyl groups, and δ-sulfoethoxyethyl groups. be able to.
Specific examples of the anion represented by X include halogen ions, perchlorate ions, thiocyanate ions, benzenesulfonate ions, p-toluenesulfonate ions, methylsulfate ions, and the like.

In the general formula [2], Z ³ is each independently unsubstituted or substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group, benzoxazole Z ⁴ represents a group of nonmetallic atoms necessary to form a ring, a thiazole ring, a benzothiazole ring, a selenazole ring, a benzoselenazole ring or a pyridine ring, Z ⁴ represents a 2-thiohydratoin ring, 2-thiooxazolidine-2,4 ′ -Represents a group of nonmetallic atoms necessary to form a dione ring or a rhodanine ring, R ¹⁴ represents an alkyl group having 1 to 4 carbon atoms, a carboxyalkyl group or a hydrogen atom, and R ¹⁵ represents one having 1 to 4 carbon atoms. Represents an alkyl group or a hydrogen atom, and n3 represents 0 or 1;

Specific examples of the ring formed by the nonmetallic atom group represented by Z ³ include oxazole, 4-methyloxazole, 5-methyloxazole, 4,5-dimethyloxazole, 4-p-tolyloxazole, benzoate. Oxazole, 5-fluorobenzoxazole, 5-chlorobenzoxazole, 5-promonzooxazole, 5-trifluoromethylbenzoxazole, 5-methylbenzoxazole, 5-methyl-6-phenylben Zoxazole, 5,6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5,6-dimethoxybenzoxazole, 5-phenylbenzoxazole, 5-carboxybenzoxazole, 5-methoxycarbonylbenzene Nzooxazole, 5-acetylbenzoxazole, selenazo 4-methylselenazole, 4-phenylselenazole, 4,5-dimethylselenazole, benzoselenazole, 5-chlorobenzoselenazole, 5-bromobenzoselenazole, 5-methylbenzoselenazole, 5-methoxybenzoselenazole, 5 , 6-Dimethylbenzoselenazole, thiazole, 4-methylthiazole, 4-phenylthiazole, 4,5-dimethylthiazole, 4-methyl-5-phenylthiazole, benzothiazole, 5-chlorobenzothiazole, 5-bromobenzothiazole, 5-methylbenzothiazole, 5-methoxybenzothiazole, 5-ethoxybenzothiazole, 6-methylbenzothiazole, 6-chlorobenzothiazole, 5-carboxybenzothiazole, 5-acetylbenzothiazole, 5- Methoxycarbonyl benzothiazole, 5-hydroxy benzothiazole, 5-trifluoromethyl benzothiazole, 5-cyano benzothiazole, 5,6-dimethyl benzothiazole, 5-acetylamino benzothiazole, 6-methoxy benzothiazole, 5,6- Examples include dimethoxybenzothiazole, 5,6-dichlorobenzothiazole, and naphtho [1,2-d] thiazole.
Next, specific examples of the compounds represented by the general formulas [1] and [2] used in the present invention are shown. The compounds represented by the general formulas [1] and [2] that can be used in the present invention are those It is not limited to.

These sensitizing dyes can be added by the method described in paragraph No. 0106 of JP-A-11-119374, but are not limited to this method.
The addition amount of the sensitizing dye can be set to a desired amount according to the sensitivity and fogging performance, but is preferably 10 ^{−5 to} 1 mol, more preferably 10 ⁻⁴ to 10 ⁻ per 1 mol of the photosensitive silver halide. ¹ mol.
In the present invention, a supersensitizer can be used to improve spectral sensitization efficiency. Supersensitizers that can be used in the present invention are disclosed in European Patent Publication Nos. EP 587,338, U.S. Pat. Nos. 3,877,943 and 4,873,184. And a compound selected from the group consisting of heteroaromatic or aliphatic mercapto compounds, heteroaromatic disulfide compounds, stilbene, hydrazine, and triazine. Particularly preferred supersensitizers are heteroaromatic mercapto compounds, heteroaromatic disulfide compounds disclosed in JP-A-5-341432, and general formula (I) or (II) in JP-A-4-18239. A stilbene compound represented by general formula (I) of JP-A-10-111543, and a compound represented by general formula (I) of JP-A-11-109547. Specifically, compounds of M-1 to M-24 of JP-A-5-341432, compounds of d-1 to d-14 of JP-A-4-18239, SS- of JP-A-10-111543. The compound of 01-SS-07, the compound of 31, 32, 37, 38, 41-45, 51-53 of Unexamined-Japanese-Patent No. 11-109547. The amount of these supersensitizers added is preferably in the range of 10 ^{−4 to} 1 mol per mol of photosensitive silver halide, more preferably in the range of 0.001 to 0.3 mol per mol of silver halide.

(F) Antifoggant, Stabilizer and Stabilizer Precursor In the present invention, the use of an antifoggant, stabilizer or stabilizer precursor can further suppress the formation of fog and stabilize the heat-developable image recording material. And a decrease in sensitivity during inventory storage can be suppressed.
Antifoggants, stabilizers and stabilizer precursors may be used alone or in combination, examples of which include US Pat. Nos. 2,131,038 and 2,694, A thiazonium salt described in US Pat. No. 716; azaindene described in US Pat. Nos. 2,886,437 and 2,444,605; described in US Pat. No. 2,728,663 Mercury salts thereof; Urazole as described in US Pat. No. 3,287,135; Sulfocatechol as described in US Pat. No. 3,235,652; Oxime as described in British Patent 623,448 , Nitroso and nitroindazole; polyvalent metal salts described in US Pat. No. 2,839,405; thiuonium salts described in US Pat. No. 3,220,839; Palladium salts, platinum salts and gold salts described in US Pat. Nos. 2,566,263 and 2,597,915; US Pat. Nos. 4,108,665 and 4,442 No. 4,128,557, US Pat. No. 4,137,079, US Pat. No. 4,138,365, and US Pat. No. 4,138,365. , 459,350; and the phosphorus compounds described in US Pat. No. 4,411,985.

(G) Mercapto compound, disulfide compound and thione compound In the present invention, for the purpose of controlling development by suppressing or accelerating development, improving spectral sensitization efficiency, improving storage stability before and after development, etc. Mercapto compounds, disulfide compounds or thione compounds can be used.
As the mercapto compound, a compound represented by Ar-SM or Ar-SS-Ar is preferable. Here, M is a hydrogen atom or an alkali metal atom, and Ar is a group containing an aromatic ring or condensed aromatic ring having one or more nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms or tellurium atoms.
Ar is preferably a benzimidazole ring, naphthimidazole ring, benzothiazole ring, naphthothiazole ring, benzoxazole ring, naphthoxazole ring, benzoselenazole ring, benzotelrazole ring, imidazole ring, oxazole ring, pyrazole ring, triazole ring, Including thiadiazole ring, tetrazole ring, triazine ring, pyrimidine ring, pyridazine ring, pyrazine ring, pyridine ring, purine ring, quinoline ring or quinazolinone ring. These rings are halogen atoms (Br, Cl, etc.), hydroxyl groups, amino groups, carboxyl groups, alkyl groups (preferably those having 1 to 4 carbon atoms), alkoxy groups (preferably 1 to 4 carbons). It may have a substituent selected from the group consisting of those having an atom) and an aryl group (which may further have a substituent).
Specific examples of mercapto compounds include 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-mercapto-5-methylbenzimidazole, 6-ethoxy-2-mercaptobenzothiazole, 2, 2′-dithiobis- (benzothiazole), 3-mercapto-1,2,4-triazole, 4,5-diphenyl-2-imidazolethiol, 2-mercaptoimidazole, 1-ethyl-2-mercaptobenzimidazole, 2- Mercaptoquinoline, 8-mercaptopurine, 2-mercapto-4 (3H) -quinazolinone, 7-trifluoromethyl-4-quinolinethiol, 2,3,5,6-tetrachloro-4-pyridinethiol, 4-amino- 6-hydroxy-2-mercaptopyrimidine Monohydrate, 2-amino-5-mercapto-1,3,4-thiadiazole, 3-amino-5-mercapto-1,2,4-triazole, 4-hydroxy-2-mercaptopyrimidine, 2-mercaptopyrimidine, 4, 6-diamino-2-mercaptopyrimidine, 2-mercapto-4-methylpyrimidine hydrochloride, 3-mercapto-5-phenyl-1,2,4-triazole, 1-phenyl-5-mercaptotetrazole, 3- (5- Mercaptotetrazole) -sodium benzenesulfonate, N-methyl-N ′-(3- (5-mercaptotetrazolyl) phenyl) urea, 2-mercapto-4-phenyloxazole, 2- [3- (9-carbazolyl) Propylimino] -3- (2-mercaptoethyl) benzothiazoline, etc. However, the present invention is not limited to these.
The amount of these mercapto compounds used is preferably 0.0001 to 1.0 mol, more preferably 0.001 to 0.3 mol, per mol of silver in the image forming layer.

(H) Plasticizer In the present invention, a polyhydric alcohol (such as glycerin and diol described in US Pat. No. 2,960,404) may be used as a plasticizer.
(I) Hardener A hardener may be used in the present invention. The hardener may be added to the image forming layer, protective layer, back layer, undercoat layer and the like. Examples of the hardener include polyisocyanates described in U.S. Pat. No. 4,281,060, JP-A-6-208193, and U.S. Pat. No. 4,791,042. Examples thereof include epoxy compounds, vinyl sulfone compounds and oxazoline compounds described in JP-A No. 62-89048.
(J) Benzoic acids The present invention may contain benzoic acids for the purpose of increasing sensitivity and preventing fogging. Benzoic acids may be added to any layer of the heat-developable image recording material of the present invention, but are preferably added to the layer provided on the image forming layer side of the support, and are added to the image forming layer or the protective layer. Is preferred.
Benzoic acids used in the present invention are not particularly limited, but preferred examples include U.S. Pat. Nos. 4,784,939, 4,152,160, JP-A-9-329865, and U.S. Pat. -329864 gazette, 9-291737 gazette, etc. are mentioned.
Benzoic acids may be added at any step of the coating solution preparation, and when added to the image forming layer, they may be added at any step of the organic silver salt preparation step to the coating solution preparation step, preferably an organic silver salt. Add from after preparation to just before application. Benzoic acids may be added in any state such as powder, solution, or fine particle dispersion. Benzoic acids may be added as a solution mixed with additives such as sensitizing dyes, dyes, reducing agents, and color toning agents (silver carriers). The amount of benzoic acid added is preferably 1 μmol to 2 mol, more preferably 1 millimol to 0.5 mol, per 1 mol of total silver of the non-photosensitive organic silver and the photosensitive silver halide.

(K) Sliding agent In the present invention, it is preferable to contain a slipping agent in the surface of the support having the image forming layer and / or the outermost surface layer on the opposite surface.
The slip agent used in the present invention is not particularly limited as long as it is a compound that reduces the coefficient of friction of the surface when it is present on the surface of the object.
Specific examples of the slip agent include U.S. Pat. No. 3,042,522, British Patent 955,061, U.S. Pat. No. 3,080,317, and 4,004,927. Silicone slipping agent described in the specification, US Pat. No. 4,047,958, US Pat. No. 3,489,567, British Patent 1,143,118, etc .; US Pat. No. 454,043, No. 2,732,305, No. 2,976,148, No. 3,206,311 and German Patent No. 1,284,295. Higher fatty acid-based slip agent, alcohol-based slip agent and acid amide-based slip agent described in the specification, US Pat. No. 1,284,294, etc .; British Patent 1,263,722, US Pat. , 933, 516 specification, etc .; Ester-based and ether-based slip agents described in Japanese Patent Nos. 2,588,765, 3,121,060, British Patent 1,198,387, etc .; US Patent The taurine type | system | group sliding agent etc. which are described in the 3,502,473 specification, the 3,042,222 specification etc. are mentioned. Specific examples of the slip agent preferably used include cellosol 524 (main component carnauba wax), polylon A, 393 and H-481 (main component polyethylene wax), high micron G-110 (main component ethylene bis stearic acid amide), Hymicron G-270 (main component stearic acid amide) (manufactured by Chukyo Yushi Co., Ltd.) and the like.
The amount of the slip agent used is preferably 0.1 to 50% by mass, more preferably 0.5 to 30% by mass, based on the amount of binder in the layer to be added.

The material of the support used in the present invention is not particularly limited, and typical examples thereof include polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), cellulose nitrate, cellulose ester, polyvinyl acetal, polycarbonate and the like. Among these, biaxially stretched polyester, particularly polyethylene terephthalate (PET), is preferable from the viewpoint of strength, dimensional stability, chemical resistance, and the like.
The thickness of the support is preferably 90 to 500 μm in base thickness excluding an undercoat layer described later.
The support may be transparent or translucent or a white reflective support. As the white reflective support, one made of a polyester film kneaded with a white inorganic facial medicine can be used.
It is preferable to provide an undercoat layer or a moisture-proof layer made of vinylidene chloride copolymer on both sides of the support. The vinylidene chloride copolymers may be used alone or in combination of two or more. The undercoat layer may contain a crosslinking agent, a matting agent or the like, and SBR, polyester, gelatin or the like may be added as a binder as necessary. Further, the undercoat layer may contain the fluorine-containing surfactant. The thickness of the undercoat layer is preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm. The thickness of the vinylidene chloride copolymer in the undercoat layer is preferably 0.3 μm or more, more preferably 0.3 to 4 μm.
When using the above-mentioned biaxially stretched polyester as a support, the polyester is heated at 130 to 185 ° C. in order to alleviate internal strain remaining in the film during biaxial stretching and eliminate thermal shrinkage strain generated during heat development. It is preferable to perform the heat treatment. The heat treatment may be performed at a constant temperature or while raising the temperature, or may be performed in a roll form or while being conveyed in a web form. When heat-treating while transporting in a web shape, the transport tension of the support during processing is preferably relatively low, specifically, preferably 7 kg / cm ² or less, and 4.2 kg / cm ² or less. More preferably. Although there is no restriction | limiting in particular in the minimum of the conveyance tension at this time, Usually, it is about 0.5 kg / cm < ² >. The heat treatment is preferably performed after the support is subjected to a treatment for improving the adhesion to the image forming layer and the back layer, the formation of an undercoat layer, and the like. The heat shrinkage rate of the support after heat treatment is -0.03 to + 0.01% in the machine direction (MD) and 0 to 0.04 in the transverse direction (TD) in the case of 120 ° C. and 30 seconds of heating conditions. % Is preferred.

In the present invention, the back layer preferably contains a dye and a base precursor. Furthermore, the following additives can be added as necessary. Further, the back layer may contain the fluorine-containing surfactant.
In the present invention, as the dye to be contained in the back layer, a dye represented by the following general formula (1) or (2) is preferable.

（式中、Ｒ¹は水素原子、脂肪族基、芳香族基、−ＮＲ²¹Ｒ²⁶、−ＯＲ²¹または−ＳＲ²¹（ここでＲ²¹およびＲ²⁶はそれぞれ独立に水素原子、脂肪族基、または芳香族基を表す。また、Ｒ²¹とＲ²⁶は協同して含窒素複素環を形成するものであってもよい。）を表す。
Ｒ²は水素原子、脂肪族基または芳香族基を表す。Ｌ¹およびＬ²は、それぞれ独立に置換または無置換のメチン基を表す。また、Ｌ¹およびＬ²で表される置換メチン基の置換基は、置換基同士が結合して不飽和脂肪族環または不飽和複素環を形成するものであってもよい。Ｚ¹は５員または６員の含窒素複素環を完成するのに必要な原子団を表す。また、該含窒素複素環は芳香族環を縮合環として有していてもよい。また、該含窒素複素環およびその縮合環は置換基を有していてもよい。
Ａは酸性核を表し、Ｂは芳香族基、不飽和へテロ環基、もしくは、下記一般式（３）で表される基を表す。ｎ、ｍは、それぞれ１または２を表す。

(Wherein R ¹ is a hydrogen atom, an aliphatic group, an aromatic group, —NR ²¹ R ²⁶ , —OR ²¹ or —SR ²¹ (wherein R ²¹ and R ²⁶ are each independently a hydrogen atom, an aliphatic group, Or an aromatic group, and R ²¹ and R ²⁶ may form a nitrogen-containing heterocycle in cooperation with each other.
R ² represents a hydrogen atom, an aliphatic group or an aromatic group. L ¹ and L ² each independently represents a substituted or unsubstituted methine group. Moreover, the substituent of the substituted methine group represented by L ¹ and L ² may be one in which the substituents are bonded to each other to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. Z ¹ represents an atomic group necessary for completing a 5-membered or 6-membered nitrogen-containing heterocyclic ring. The nitrogen-containing heterocycle may have an aromatic ring as a condensed ring. Further, the nitrogen-containing heterocycle and its condensed ring may have a substituent.
A represents an acidic nucleus, and B represents an aromatic group, an unsaturated heterocyclic group, or a group represented by the following general formula (3). n and m each represent 1 or 2.

（式中、Ｌ³は置換または無置換のメチン基を表す。また、Ｌ³はＬ²と結合して不飽和脂肪族環または不飽和複素環を形成していてもよい。Ｒ³は脂肪族基または芳香族基を表す。Ｚ²は５員または６員の含窒素複素環を完成するのに必要な原子団を表す。また、該含窒素複素環は芳香族環を縮合環として有していてもよい。また、該含窒素複素環およびその縮合環は置換基を有していてもよい。））

(In the formula, L ³ represents a substituted or unsubstituted methine group. L ³ may be bonded to L ² to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. R ³ represents a fatty acid. Z ² represents an atomic group necessary to complete a 5- or 6-membered nitrogen-containing heterocycle, and the nitrogen-containing heterocycle has an aromatic ring as a condensed ring. In addition, the nitrogen-containing heterocycle and its condensed ring may have a substituent.))

In the general formulas (1) and (2), R ¹ is preferably —NR ²¹ R ²⁶ , —OR ²¹ , or —SR ²¹ .
R ²¹ is preferably an aliphatic group or an aromatic group, more preferably an alkyl group, a substituted alkyl group, an aralkyl group, a substituted aralkyl group, an aryl group or a substituted aryl group, and R ²⁶ is a hydrogen atom Or it is preferably an aliphatic group, more preferably a hydrogen atom, an alkyl group or a substituted alkyl group.
The nitrogen-containing heterocycle formed by R ²¹ and R ²⁶ in cooperation is preferably a 5-membered or 8-membered nitrogen-containing heterocycle. The nitrogen-containing heterocycle may have a hetero atom other than nitrogen (eg, oxygen atom, sulfur atom).

Here, the aliphatic group means an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, a substituted alkynyl group, an aralkyl group or a substituted aralkyl group. In the present invention, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an aralkyl group or a substituted aralkyl group is preferred, and an alkyl group, a substituted alkyl group, an aralkyl group or a substituted aralkyl group is more preferred. A chain aliphatic group is preferred to a cyclic aliphatic group. The chain aliphatic group may have a branch. The number of carbon atoms in the alkyl group is preferably 1-30, more preferably 1-20, and even more preferably 1-15. The alkyl part of the substituted alkyl group is the same as in the case of the alkyl group.
The number of carbon atoms in the alkenyl group and alkynyl group is preferably 2-30, more preferably 2-20, and even more preferably 2-15. The alkenyl part of the substituted alkenyl group and the alkynyl part of the substituted alkynyl group are the same as the alkenyl group and alkynyl group, respectively. The number of carbon atoms in the aralkyl group is preferably 7 to 35, more preferably 7 to 25, and still more preferably 7 to 20. The aralkyl part of the substituted aralkyl group is the same as the aralkyl group. Examples of substituents for aliphatic groups (substituted alkyl groups, substituted alkell groups, substituted alkynyl groups, substituted aralkyl groups) include halogen atoms (fluorine atoms, chlorine atoms, bromine atoms), hydroxyl groups, alkoxy groups, aryloxy groups Silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, nitro group, sulfo group, carboxyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group Alkylthiocarbonyl group, heterocyclic group, cyano group, amino group (including anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl group and Arylsulfonylamino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, alkyl group and arylsulfinyl group, alkyl group and arylsulfonyl group, alkoxycarbonyl group, imide group, phosphino group, phosphinyl group , A phosphinyloxy group, a phosphinylamino group, and a silyl group. The carboxyl group and the sulfo group may be in a salt state. The cation that forms a salt with the carboxyl group and the sulfo group is preferably an alkali metal ion (eg, sodium ion, potassium ion).

Here, the aromatic group means an aryl group or a substituted aryl group. The number of carbon atoms in the aryl group is preferably 6-30, more preferably 6-20, and even more preferably 6-15. The aryl part of the substituted aryl group is the same as the aryl group. Examples of the substituent of the aromatic group (substituted aryl group) include the aliphatic group and those exemplified in the examples of the substituent of the aliphatic group.
In the general formulas (1) and (2), R ² represents a hydrogen atom, an aliphatic group, or an aromatic group, and the definition of the aliphatic group and the aromatic group is as described above.
R ² is preferably a hydrogen atom or an aliphatic group, more preferably a hydrogen atom or an alkyl group, further preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, Most preferably it is.
In the general formulas (1), (2) and (3), examples of the substituent of substituted methine represented by L ¹ , L ² and L ³ include a halogen atom, an aliphatic group and an aromatic group. It is done. Here, the definition of the aliphatic group and the aromatic group is as described above.
The substituents of methine may be bonded to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. An unsaturated aliphatic ring is preferred over an unsaturated heterocyclic ring. The ring to be formed is preferably a 5-membered ring or a 6-membered ring, and more preferably a cyclopentene ring or a cyclohexene ring.
L ¹ , L ² , and L ³ are particularly preferably unsubstituted methylene groups or those that form a cyclopentene ring or a cyclohexene ring.
In the general formula (1), n represents 1 or 2, but is preferably 1. When n is 2, the methine group is repeated but they need not be identical. In the general formula (2), m represents 1 or 2, but is preferably 1. When m is 2, the methine group is repeated but they need not be identical.

In the general formulas (1) and (2), Z ¹ is an atomic group that forms a 5-membered or 6-membered nitrogen-containing heterocycle. Examples of the nitrogen-containing heterocycle formed include oxazole ring, thiazole ring, selenazole ring, pyrrole ring, pyrroline ring, imidazole, and pyridine ring. The nitrogen-containing heterocycle formed by Z ¹ is preferably a 5-membered ring rather than a 6-membered ring. The nitrogen-containing heterocycle may be condensed with an aromatic ring (benzene ring or naphthalene ring). Further, the nitrogen-containing heterocycle and its condensed ring may have a substituent. Examples of the locating group include the substituents shown in the description of the substituent for the aromatic group, preferably a halogen atom (fluorine atom, chlorine atom, bromine atom), hydroxyl group, nitro group. , Carboxyl group, sulfo group, alkoxy group, aryl group and alkyl group. The carboxyl group and the sulfo group may be in a salt state. The cation that forms a salt with the carboxyl group and the sulfo group is preferably an alkali metal ion (eg, sodium ion, potassium ion).
In the general formula (1), B represents an aromatic group, an unsaturated heterocyclic group, or a group represented by the general formula (3). The definition of the aromatic group is as described above. As the aromatic group represented by B, a substituted or unsubstituted phenyl group is preferable, and as the ring-setting group, a halogen atom, amino group, acylamino group, alkoxy group, aryloxy group, alkyl group, alkylthio group, aryl A group is preferred, and an amino group, an acylamino group, an alkoxy group and an alkyl group are particularly preferred at the 4-position. The unsaturated heterocyclic ring represented by B is preferably a 5-membered or 6-membered heterocyclic group composed of carbon, oxygen, nitrogen and sulfur atoms. Of these, a 5-membered ring is particularly preferred. Preferred examples include substituted, unsubstituted pyrrole, indole, thiophene, and furan.

Z ² in the general formula (3) is an atomic group that forms a 5-membered or 6-membered nitrogen-containing heterocycle, and may be the same as or different from Z ¹ . Examples of the nitrogen-containing heterocycle formed by Z ² can include the same ring as the ring formed by Z ¹ described above.
R ³ represents an aliphatic group or an aromatic group, but is preferably an aliphatic group, and most preferably —CHR ² (COR ¹ ), which is a substituent on the nitrogen atom of the general formula (1). .
In the general formula (2), the acidic nucleus represented by A is preferably a cyclic ketomethylene compound or an acidic nucleus having a methylene group sandwiched between electron-withdrawing groups. Examples of cyclic ketomethylene acidic nuclei include 2-pyrazolin-5-one, rhodanine, hydantoin, thiohydantoin, 2,4-oxazolidinedione, isoxazolone, barbituric acid, indandione, dioxopyrazolopyridine, melodrum acid And acidic nuclei such as hydroxypyridine, pyrazolidinedione, 2,5-dihydrofuran-2-one and pyrrolin-2-one. These may have a substituent.
An acidic nucleus having a methylene group sandwiched between electron-withdrawing groups can be represented as Z ¹¹ CH ₂ Z ²¹ . Here Z ^11, Z ²¹ are each ^{_{-CN, -SO 2 R 11, -COR}} 11, -COOR 21, -CONHR 21, -SO 2 NHR 21, -C (= C (CN) 2) R 11, - represents _{C (= C (CN) 2} ) NHR 11, R 11 represents an alkyl group, an aryl group, a heterocyclic group, R ²¹ represents a group represented by a hydrogen atom and R ^11, and R ^11, R Each ²¹ may have a substituent.
Among these acidic nuclei, 2-pyrazolidine-5-one, isoxazolone, barbituric acid, indandione, hydroxypyridine, pyrazolidinedione, and dioxopyrazolopyridine are more preferable.

The dye represented by the general formula (1) preferably forms a salt with an anion. When the dye represented by formula (1) has an anionic group such as carboxyl or sulfo as a substituent, the dye can form an inner salt. In other cases, the dye preferably forms a salt with the extramolecular anion. The anion is preferably monovalent or divalent, and more preferably monovalent. Examples of anions include halogen ions (Cl ⁻ , Br ⁻ , I ⁻ ), p-toluenesulfonic acid ions, ethyl sulfate ions, 1,5-disulfonaphthalene dianions, PF ₅ ⁻ , BF ₄ ⁻ and ClO ₄ ^−. Is mentioned.
Specific examples of the dyes represented by the general formulas (1) and (2) (the base decoloring dye of the present invention) are shown below.

Next, the base precursor used in the present invention will be described.
The dye represented by the general formula (1) or (2) or a salt thereof can be decolored by acting a base under heating conditions. In the decoloring of the dye, a base acts on the dye, the active methylene group in the dye is deprotonated, and the nucleophilic species generated thereby nucleophilically attacks the methylene chain in the molecule to form an intramolecular closed ring. It is thought to happen by doing. Accordingly, the base used for decoloring the dye utilizing this reaction may be any base that can deprotonate the active methylene group in the dye. The number of ring members newly formed by the intramolecular ring-closing reaction is not limited, but is preferably a 5- to 7-membered ring, and more preferably a 5- to 6-membered ring. The substantially colorless compound formed in this way is a stable compound and does not return to the original dye. Therefore, there is no problem in the color recovery of the dye decolored by this reaction.
The heating temperature causing the decoloring reaction is preferably 40 ° C to 200 ° C, more preferably 80 ° C to 150 ° C, and further preferably 100 ° C to 130 ° C. The heating time is preferably 1 to 120 seconds, more preferably 5 to 60 seconds, and further preferably 10 to 30 seconds.
If a base is added to the back layer together with the above dyes, they will react with each other during storage and lose their halation-preventing function. Therefore, the base does not act as a base at room temperature, and is thermally decomposed during heat development. It is desirable to use it as a thermal decomposition type precursor that produces. Accordingly, the heat development temperature and time are determined in consideration of the time required for image formation and the time required for base generation and decoloration.

The base necessary for the decoloring reaction is a broad base, and includes a nucleophile (Lewis base) in addition to a narrow base. When the base coexists with the dye, the decoloring reaction proceeds slightly even at room temperature. Therefore, it is desirable to keep the base physically or chemically isolated from the dye and to contact (react) the base and the dye during heating. Physical separation of the base includes methods such as using microcapsules, encapsulating in hot-melt fine particles, or adding a dye and a base to different layers.
Microcapsules include those that burst by pressure and those that burst by heating. Since the decoloring reaction is carried out under heating conditions, it is convenient to use microcapsules that burst when heated (thermally responsive microcapsules). For isolation, either the base or the dye is encapsulated in microcapsules. When the outer shell of the microcapsule is opaque, it is preferable to enclose a base in the microcapsule. The heat-responsive capsules are described in Hiroyuki Moriga, Introductory / Special Paper Chemistry (Showa 50), and JP-A-1-150575. In addition, a base or a dye can be added to the fine particles of a hot-melt material such as wax.
In this case, the melting point of the heat-meltable substance is between room temperature and the aforementioned heat development heating temperature. In the light-sensitive material, when a layer containing a dye and a layer containing a base are separated, it is preferable to provide a barrier layer containing a hot-melt material between these layers.

  The chemical isolation means are easier to implement and are preferred than the physical isolation means. The chemical isolation means is typically the use of a base precursor. There are various types of base precursors, but since the decoloring reaction is carried out under heating conditions, it is convenient to use a type of precursor that generates (or releases) a base by heating. As a precursor that generates a base by heating, a thermal decomposition (decarboxylation type) base precursor comprising a carboxylic acid and a base salt is representative. When the decarboxylated base precursor is heated, the carboxyl group of the carboxylic acid is decarboxylated to release the organic base. As the carboxylic acid, sulfonylacetic acid or propiolic acid which is easily decarboxylated is used. The sulfonylacetic acid and propiolic acid preferably have an aromatic group that promotes decarboxylation (aryl or saturated double ring ring group) as a substituent. The base precursor of sulfonyl acetate is described in JP-A-59-168441, and the base precursor of propiolic acid is described in JP-A-59-180537. The base side component of the decarboxylated base precursor is preferably an organic base, more preferably amidine, guanidine or a derivative thereof. The organic base is preferably a diacid base, a triacid base, or a tetraacid base, more preferably a diacid base, and most preferably an amidine derivative or a guanidine derivative.

The precursor of diacid base, triacid base or tetraacid base of amidine derivatives is described in JP-B-7-59545. A precursor of a dioxygen base, triacid base or tetraacid base of a guanidine derivative is described in JP-B-8-10321. The diacid base of an amidine derivative or guanidine derivative is a divalent group combining (A) two amidine or guanidine moieties, (B) a substituent of the amidine or guanidine moiety, and (C) two amidine or guanidine moieties. Consisting of a linking group.
Examples of the substituent of (B) include an alkyl group (including a cycloalkyl group), an alkenyl group, an alkynyl group, an aralkyl group, and a heterocyclic residue. Two or more substituents may combine to form a nitrogen-containing heterocycle. The linking group in (C) is preferably an alkylene group or a phenylene group.
Specific examples of amidine-induced rest or diacid base precursors of guanidine derivatives are shown below, but base precursors that can be used in the present invention are not limited to these.

The dye can be contained in the heat-developable image recording material in the form of a molecule, emulsion dispersion or solid fine particle dispersion. In the case of dispersing in a molecular form, a dye solution is added to the coating solution. When dispersed and added in the form of solid fine particles, a dispersion of solid fine particles of the dye is prepared and then added to the coating solution.
The dye is generally added so that the optical density (absorbance) exceeds 0.1 when measured at a target wavelength. Practically, the addition amount is adjusted so that the optical density is in the range of 0.3 to 3.0, more preferably in the range of 0.3 to 2.0, and still more preferably in the range of 0.3 to 1.5. It is good to adjust.
The amount of the base precursor used is preferably 1 to 100 times, more preferably 3 to 30 times that of the dye, in terms of mol ratio. The base precursor is preferably added in the form of solid fine particles.
Two or more dyes and base precursors may be used in combination. In particular, in order to adjust the melting point to a desired region, it is preferable to mix those having different melting points.

A binder can be used for the back layer. The binder used for the back layer is preferably transparent or translucent and colorless. The binder may be a natural polymer, a synthetic resin, a synthetic polymer, a synthetic copolymer, a medium for forming a film, and examples thereof include gelatin, gum arabic, polyvinyl alcohol, hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, Polyvinylpyrrolidone, casein, starch, polyacrylic acid, polymethylmethacrylic acid, polyvinyl chloride, polymethacrylic acid, copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), polyvinylacetals (Polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resins, polyvinylidene chloride, polyepoxides, polycarbonates, polyvinyl acetate Cellulose esters, polyamides, and the like. The back layer may contain a polymer latex used for the image forming layer described above.
The glass transition temperature of the polymer latex polymer used for the back layer (particularly the outermost layer) is preferably 25 to 100 ° C. The binder amount of the back layer is preferably 0.01 to 10 g / m ^2, more preferably from 0.5 to 5 g / m ^2.
In order to reduce the Beck seconds, it is preferable to add a matting agent to the back layer. The Beck smoothness is preferably 10 to 2000 seconds, more preferably 50 to 1500 seconds, and the particle size and addition amount of the matting agent may be changed in order to obtain such Beck smoothness. The Beck smoothness is obtained according to JIS P8119 or TAPPIT479.

The heat-developable image recording material of the present invention may have non-photosensitive layers such as an intermediate layer and a protective layer in addition to the image forming layer.
In addition to the above back layer, various auxiliary layers may be provided on the side of the support opposite to the image forming layer.
In the heat-developable image recording material of the present invention, it is preferable to provide an intermediate layer in order to solve the problems that occur when a protective layer is provided on the image forming layer.
For example, when the pH difference between the protective layer and the image forming layer is large, if the protective layer is directly provided on the image forming layer, an interface failure may occur, but an intermediate layer is provided to avoid this coating failure. be able to.
Further, an intermediate layer can be provided in order to include a part of an additive that exhibits a disadvantageous interaction when added simultaneously to the image forming layer. Agents that can be added include reducing agents, halogen precursors, silver carriers, dyes, facials, development accelerators, development inhibitors, image stabilizers, dispersion stabilizers, crosslinking agents, plasticizers, benzoic acids, etc. Can be mentioned. As the binder for the intermediate layer, the binder described above can be preferably used. As the binder, gelatin, polyvinyl alcohol, other synthetic polymers, and the like can be used in addition to polymers soluble in organic solvents and aqueous polymer latexes. The thickness of the intermediate layer is preferably 0.01 to 30 μm, more preferably 0.05 to 10 μm.
The heat-developable image recording material of the present invention is preferably provided with a protective layer comprising a polymer binder or the like in order to protect the surface of the material. The protective layer is provided on the outer layer of the surface having the image forming layer of the support.
As the polymer binder, the binder described above can be preferably used. When polymer latex is used, the glass transition temperature of the polymer is preferably 25 to 100 ° C. In addition to the polymer latex, gelatin, polyvinyl alcohol, other synthetic polymers, and the like can also be used as a binder for the protective layer. The usage-amount of a binder becomes like this. Preferably it is 0.2-10 g / m < ² > with respect to the area of a protective layer, More preferably, it is 1-5 g / m < ² >.

The protective layer may contain additives such as a reducing agent, a halogen precursor, a dispersion stabilizer, a crosslinking agent, a surfactant for improving coating properties and adjusting the chargeability, benzoic acids, a hardener, and a slip agent. . Preferred embodiments of these additives are basically the same as those in the case of the image forming layer. The thickness of the protective layer is preferably 0.01 to 30 μm, more preferably 0.05 to 10 μm.
It is desirable to add an inorganic or organic matting agent to the protective layer in order to prevent adhesion failure caused when the heat-developable image recording material is overlaid. Examples of matting agents include US Pat. Nos. 1,939,213, 2,701,245, 2,322,037, and 3,262,782. , No. 3,539,344, No. 3,767,448, etc., No. 1,260,772, No. 2,192,241 No. 3,257,206, No. 3,370,951, No. 3,523,022, No. 3,769,020, etc. And inorganic matting agents. Specifically, water-dispersible vinyl polymers (polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, acrylonitrile-α-methylstyrene copolymer, polystyrene, styrene-divinylbenzene copolymer, polyvinyl acetate, polyethylene carbonate, poly Tetrafluoroethylene, etc.), cellulose derivatives (methyl cellulose, cellulose acetate, cellulose acetate propionate, etc.), starch derivatives (carboxy starch, carboxynitrophenyl starch, urea-formaldehyde-starch reactant, etc.), cured with known curing agents Gelatin and coacervate hardened organic compounds such as hardened gelatin into microcapsule hollow particles, silicon dioxide, titanium dioxide, magnesium dioxide, aluminum oxide, sulfuric acid Beam can be preferably used calcium carbonate, desensitized silver chloride and silver bromide in a known manner, a glass, an inorganic compound of diatomaceous earth as a matting agent. The matting agents may be used alone or in combination. Various shapes such as a spherical shape, a rod shape, a needle shape, a scale shape, and an indefinite shape can be selected.

The matting agent has an effect of preventing adhesion failure by forming irregularities on the surface of the protective layer to reduce the contact area. Accordingly, it is preferable that the average particle size is larger than the thickness of the protective layer, but it is sufficient if it is small as long as it forms an aggregate and protrudes from the surface. The average particle size of the matting agent is preferably 1 to 20 μm. If the average particle size is less than 1 μm, it is not practical, and if it exceeds 20 μm, the risk of sinking into the image forming layer and hindering image formation to give pinholes increases. Further, the particle size distribution of the matting agent is desirably narrow, and the monodispersity is preferably 10% or less. When there are a plurality of protective layers, the matting agent is preferably added to the outermost surface layer or a layer as close as possible to the outer surface.
The protective layer preferably contains the fluorine-containing surfactant. Even when the matting agent and the fluorine-containing surfactant are added to the back layer, a desired effect can be obtained. These may be added to either or both of the protective layer and the back layer, but at least the fluorine-containing surface activity is preferably added to the image forming layer side. A fluorine-containing surfactant can be overcoated on the protective layer.
The pH of the protective layer varies depending on the additive, but is relatively low, 2-7. In the case of forming a plurality of protective layers, it is preferred that the layer close to the image forming layer has a pH of 4 to 7, and the far layer has a pH of 2 to 5. The protective layer may be composed of a plurality of layers. For example, from a protective lower layer for covering an image mainly composed of an organic polymer, and a protective upper layer for preventing adhesion including matting agent, slip agent, fluorine-containing surfactant, etc. May be configured.
The heat-developable image recording material of the present invention may have an undercoat layer described in US Pat. No. 5,051,335.
For the coating formation of each constituent layer of the heat-developable image recording material of the present invention, coating operations such as dip coating, air knife coating, flow coating, extrusion coating using a hopper described in US Pat. No. 2,681,294, etc. Is used. Two or more layers can be coated simultaneously by the methods described in US Pat. No. 2,761,791 and British Patent 837,095.

The heat-developable image recording material of the present invention can form an image by, for example, exposing to light having a wavelength of 500 nm or less, particularly 360 to 500 nm, followed by heat development. Preferably, the exposure is performed by a scanning laser exposure apparatus, and thermal development is performed at a temperature of 100 ° C. to 150 ° C. By such an image forming method, it is possible to perform medical image formation and printing plate making image formation.
When the heat-developable image recording material of the present invention is used as a mask when producing a printing plate using a PS plate, the heat-developable image recording material after heat development is information for setting exposure conditions for the PS plate in a plate making machine. In general, information for setting the plate making conditions such as the conveying conditions of the mask original and the PS plate is carried as image information. Therefore, normally, the concentration (amount used) of the above-mentioned irradiation dye, halation dye, and filter dye is limited in order to read these information. Since these pieces of information are read by an LED or a laser, it is necessary that the Dmin (minimum concentration) in the wavelength range of the sensor be low, and usually the absorbance is required to be 0.3 or less. For example, when a light source having a wavelength of 670 nm is used as a detector for detecting a registration mark and a barcode reader, if the Dmin (minimum density) near 670 nm is high, information on the film cannot be detected accurately, and conveyance failure and exposure failure are detected. A work error occurs. For this reason, Dmin around 670 nm needs to be low, and the absorbance at 660 to 680 nm after heat development is set to 0.3 or less. In this case, the absorbance is more preferably 0.25 or less. Although there is no restriction | limiting in particular in the lower limit, Usually, it is about 0.10.

Generally, in an exposure apparatus used for imagewise exposure, a laser diode (LD) and a light emitting diode (LED) are used as a light source. In particular, LD is more preferable in terms of high output and high resolution.
The light source of the exposure apparatus may be any light source as long as it can generate an electromagnetic spectrum light in the target wavelength range, but a dye laser, a gas laser, a solid laser, a semiconductor laser, or the like can be used as long as it is an LD. . Of particular interest are modules or blue semiconductor lasers in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated. The exposure is performed at a high illuminance, generally with a short exposure time of 10 ⁻⁷ seconds or less.
The exposure is performed by overlapping the light beams of the light sources. Overlap means that the sub-scanning pitch width is smaller than the beam diameter. The degree of overlap can be quantitatively expressed by, for example, sub-scanning pitch width / FWHM (overlap coefficient) when the beam diameter is expressed by the half-value width (FWHM) of the beam intensity. In the case of exposure with overlapping, it is preferable that the overlapping coefficient is 0.2 or more.
For example, a cylindrical outer surface scanning method, a cylindrical inner surface scanning method, or a planar scanning method can be used for the exposure, but there is no limitation. The light source channel may be a single channel or a multi-channel, and a multi-channel equipped with two or more laser heads is preferable from the viewpoint of obtaining a high output and shortening the writing time. In particular, in the case of the cylindrical outer surface type, a multichannel equipped with several to several tens of laser heads is preferably used.
As a technique for preventing the generation of interference fringes at the time of exposure, it is disclosed in Japanese Patent Application Laid-Open No. 5-113548 or the like, in which a laser beam is obliquely incident on a photosensitive material, or in International Publication WO95 / 31754 Known methods using multimode lasers are known, and these techniques are preferably used.

The heat development method for forming an image using the heat-developable image recording material of the present invention may be any method. Usually, the heat-developable image recording material exposed imagewise is heated and developed. As a preferred embodiment of the heat developing machine to be used, as a type in which the heat-developable image recording material is brought into contact with a heat source such as a heat roller or a heat drum, JP-B-5-56499, JP-A-9-292695 and JP-A-9- As a non-contact type heat developing machine described in Japanese Patent No. 297385 and International Publication No. WO95 / 30934, JP-A-7-13294, International Publication Nos. WO97 / 28489, 97/28488, and 97 / There is a heat developing machine described in Japanese Patent No. 28487. A particularly preferred embodiment is a non-contact type heat developing machine. The preferred development temperature is 80 to 250 ° C, more preferably 100 to 150 ° C. The development time is preferably 1 to 180 seconds, more preferably 5 to 90 seconds. The line speed is preferably 140 cm / min or more, more preferably 150 cm / min or more.
In order to prevent processing unevenness due to dimensional change of the heat-developable image recording material during heat development, after heating for 5 seconds or more so as not to produce an image at a temperature of 80 ° C. or higher and lower than 115 ° C., 110 ° C. to 140 ° C. It is effective to adopt a method (so-called multi-step heating method) in which an image is formed by heat development with the above method.

When the heat-developable image recording material is subjected to heat development processing, it is exposed to a high temperature of 100 ° C. or higher, and therefore, a part of the components contained in the material or a part of the decomposition components due to heat development is volatilized. These volatile components cause development unevenness, corrode the components of the heat developing machine, precipitate as foreign matter at low temperatures, cause deformation of the screen, and make it dirty. It is known that there is. As a method for removing these influences, it is known to install a filter in the heat developing machine and optimally adjust the air flow in the heat developing machine. These methods can be used effectively in combination.
In International Publication Nos. WO95 / 30933, 97/21150, and Japanese National Publication No. 10-500496, a filter cartridge having a first opening for introducing volatile components and a second opening for discharging is provided. It is described that it is used in a heating device that heats in contact with a film. In addition, International Publication WO 96/12213 and Japanese Patent Publication No. 10-507403 describe that a filter in which a heat-conducting condensing collector and a gas-absorbing fine particle filter are combined is used. In the present invention, these can be preferably used. In US Pat. No. 4,518,845 and Japanese Patent Publication No. 3-54331, a device for removing steam from a film, a pressure device for pressing the film against a heat transfer member, and a heat transfer member are heated. A device having a device to perform is described. In addition, International Publication No. WO98 / 27458 describes that a component that increases fogging volatilization from a film is removed from the film surface. These can also be preferably used for the heat development processing of the heat-developable image recording material of the present invention.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, materials, reagents, ratios, repetitives and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Accordingly, the scope of the present invention is not limited by the following examples.
Example 1
1. Preparation of support (preparation of undercoat support)
After each corona discharge treatment is performed on both surfaces of a biaxially stretched polyethylene terephthalate support having a thickness of 120 μm, a coating solution of the following formulation 1 is applied on one surface (image forming layer surface) with a wire bar to a wet coating amount of 6. Apply at 6 ml / m ² (per side) and dry at 180 ° C. for 5 minutes to form an image forming layer side undercoat layer, and then apply the coating solution of Formula 2 below on the opposite side (back side) Apply with a wire bar so that the wet coating amount is 5.7 ml / m ² and dry at 180 ° C. for 5 minutes to form the first layer on the back surface side. The undercoat support was prepared by applying the coating amount to 7.7 ml / m ² and drying at 180 ° C. for 6 minutes to form a second layer on the back surface side.

Formula 1 (for image forming layer side undercoat)
Takamatsu Yushi Co., Ltd., pesresin A-520 (30% by mass solution) 59 g
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number 8.5, 10% by mass solution) 5.4 g
MP-1000 (polymer fine particle, average particle size 0.4 μm), manufactured by Soken Chemical Co., Ltd.
0.91g
935 ml of distilled water
Formula 2 (for back side 1st layer)
Styrene-butadiene copolymer latex (solid content 40% by mass, styrene / butadiene weight ratio = 68/32) 158 g
2,4-Dichloro-6-hydroxy-S-triazine sodium salt (8% by mass aqueous solution) 20 g
Sodium laurylbenzenesulfonate (1% by weight aqueous solution) 10 ml
854 ml of distilled water
Formula 3 (for back layer 2nd layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion) 84 g
Gelatin (10 mass% aqueous solution) 89.2g
8.6 g, manufactured by Shin-Etsu Chemical Co., Ltd., Metroz TC-5 (2% by weight aqueous solution)
Made by Soken Chemical Co., Ltd., MP-1000 0.01 g
Sodium dodecylbenzenesulfonate (1% by weight aqueous solution) 10 ml
NaOH (1% by mass) 6 ml
Proxel (ICI) 1ml
805 ml of distilled water

(Heat relaxation treatment of undercoat support)
The undercoat support obtained above was subjected to a first heat treatment for 10 minutes while being conveyed at a tension of 5 kg / cm ² under the condition of a temperature of 130 ° C., followed by a tension of 10 kg / cm ² at a temperature of 40 ° C. The second heat treatment was performed for 15 seconds while being conveyed.

2. Formation of Back Layer and Back Protective Layer (2-1) Preparation of Dispersion Used (Preparation of Solid Fine Particle Dispersion of Dye (1))
19.6 g of the dye (1) and 5.8 g of sodium p-dodecylbenzenesulfonate were mixed with 305 ml of distilled water, and the mixture was beads using a sand mill (manufactured by IMEX Co., Ltd., 1/4 Gallon sand grinder mill). Dispersion gave a dye solid fine particle dispersion having an average particle size of 0.2 μm.
(Preparation of solid fine particle dispersion of comparative yellow dye A)
19.6 g of the following yellow dye A and 5.8 g of sodium p-dodecylbenzenesulfonate were mixed with 305 ml of distilled water, and the mixture was used with a sand mill (manufactured by IMEX Co., Ltd., 1/4 Gallon sand grinder mill). The beads were dispersed to obtain a solid fine particle dispersion having an average particle size of 0.2 μm.

(2-2) Preparation of coating solution (Preparation of back layer coating solution of Sample-1 of the present invention)
Gelatin 17 g, polyacrylamide 9.6 g, solid fine particle dispersion 56 g of the above dye (1), monodisperse polymethyl methacrylate particles (average particle size 8 μm) 1.5 g as matting agent, preservative benzoisothiazolinone 0.03 g Then, 2.2 g of sodium polyethylene sulfonate and 844 ml of water were mixed to prepare a back layer coating solution of Sample-1 of the present invention.
(Preparation of Back Layer Coating Solution for Comparative Sample-A)
The present invention was used except that the solid fine particle dispersion of the comparative yellow dye A was used in place of the dye in the same molar amount instead of the solid fine particle dispersion of dye (1) in the back layer coating solution of Sample-1 of the present invention. A back layer coating solution of Comparative Sample-A was prepared in the same manner as the back layer coating solution of Sample-1 of the invention.
(Preparation of back protective layer coating solution)
The container was kept at 40 ° C., 50 g of gelatin, 0.2 g of sodium polystyrenesulfonate, 2.4 g of N, N-ethylenebis (vinylsulfoneacetamide), 1 g of sodium tert-octylphenoxyethoxyethanesulfonate, 30 mg of benzoisothiazolinone , Fluorine-based surfactant (F-1: N-perfluorooctylsulfonyl-N-propylalanine potassium salt) 37 mg, fluorine-based surfactant (F-2: polyethylene glycol mono (N-perfluorooctylsulfonyl-N-) propyl-2-aminoethyl) ether (ethylene oxide average polymerization degree 15)) 0.15 g, a fluorine-based surfactant _{(F-3: C 8 F} 17 SO 2 -N (C 3 H 7 (n)) - ( _{CH 2 CH 2 O) -CH 2} CH 2 CH 2 CH 2 SO 3 Na) 64mg, fluorine-based Industry Surfactant (F-4: C ₈ F ₁₇ SO ₃ K) 32 mg, acrylic acid / ethyl acrylate copolymer (copolymerization weight ratio 5/95) 8.8 g, aerosol OT (manufactured by American Cyanamid Co., Ltd.) 0.6 g, 1.8 g of liquid paraffin emulsion as liquid paraffin, and 950 ml of water were mixed.

(2-3) Application (Formation of application of back layer and back protective layer of Sample-1 of the present invention)
On the back surface side of the undercoat support, the back layer coating solution of Sample-1 of the present invention was applied so that the solid coating amount of the base decoloring dye (1) was 0.04 g / m ^2. The protective layer coating solution was applied simultaneously to form a gelatin coating amount of 1.7 g / m ² and dried to form the back layer and the back protective layer of Sample-1 of the present invention.
(Coating formation of back layer and back protective layer of Comparative Sample-A)
Comparison was made in the same manner as the coating formation of the back layer and the back protective layer of Sample-1 of the present invention except that the back layer coating solution of Comparative Sample-A was used instead of the back layer coating solution of Sample-1 of the present invention. The back layer and the back protective layer of Sample-A were formed.

3. Formation of image forming layer and protective layer thereof (3-1) Preparation of dispersion and solution used (Preparation of silver halide emulsion A)
Silver iodide grains a prepared as described below were dissolved by heating at 38 ° C., and 7 × 10 −3 mol of benzothiazolium iodide was added as a 1% by mass aqueous solution per mol of silver. Further, water was added to adjust the amount of silver contained in 1 kg to 38.2 g to prepare a silver halide emulsion A.
(Preparation of silver iodide grains a)
To a solution of 1420 ml of distilled water was added 4.3 ml of a 1% by weight potassium iodide solution, 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., a solution A in which distilled water was diluted to 22.56 g of silver nitrate and diluted to 195.6 ml and solution B in which 21.8 g of potassium iodide was diluted with distilled water to a volume of 218 ml 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 with distilled water to a volume of 600 ml, Solution C is the total amount over 12 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 hexachloroiridate (III) was added 10 minutes after the start of the addition of Solution C and Solution D to 1 × 10 ⁻⁴ mol per mol of silver. Further, 5 seconds after the completion of the addition of the solution C, a total amount of 3 × 10 ⁻⁴ mol of iron (II) hexacyanide aqueous solution per 1 mol of silver was added. 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 iodide dispersion having a pAg of 8.0.

While maintaining the silver iodide dispersion at 47 ° C. with stirring, 5 ml of a methanol solution of 0.34% by mass of 1,2-benzisothiazolin-3-one was added, and 20 minutes later, sodium benzenethiosulfonate was added to methanol. 7.6 × 10 ⁻⁵ mol was added to 1 mol of silver in the solution, and further 5 minutes later, 6.2 × 10 ⁻⁵ mol of sodium thiosulfate was added per 1 mol of silver, followed by aging for 91 minutes. 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-mercaptoben ヅ imidazole was added to the methanol solution at 4 per mol of silver. 8 × 10 ⁻³ mol and 1-phenyl-2-hebutyl-5-mercapto-1,3,4-triazole were added with methanol solution in an amount of 5.4 × 10 ⁻³ mol with respect to 1 mol of silver. Silver particles a were produced.
The obtained silver iodide grains a were pure silver iodide grains having an average sphere equivalent diameter of 0.040 μm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

(Preparation of silver behenate dispersion A)
Behenic acid (manufactured by Henkel, product name Edenor C22-85R) 87.6 kg, distilled water 423 L, 5 mol / L NaOH aqueous solution 49.2 L, tert-butanol 120 L were mixed, and the reaction was stirred at 75 ° C. for 1 hour. To obtain a sodium behenate solution. Separately, 206.2 L (pH 4.0) of an aqueous solution containing 40.4 kg of silver nitrate was prepared and kept warm at 10 ° C. A reaction vessel containing 635 L of distilled water and 30 L of tert-butanol was kept at 30 ° C., and with sufficient stirring, the total amount of the previous sodium behenate solution and the total amount of silver nitrate aqueous solution were 93 minutes and 15 seconds at a constant flow rate, respectively. Added over 90 minutes. At this time, only the silver nitrate aqueous solution is added for 11 minutes after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution is started. After the addition of the aqueous silver nitrate solution is completed, only the sodium behenate solution is added for 14 minutes and 15 seconds. To be added. At this time, the temperature in the reaction vessel was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant. The piping of the sodium behenate solution addition system was prepared by keeping warm water by circulating hot water outside the double pipe so that the liquid temperature at the outlet of the addition nozzle tip was 75 ° C. Moreover, the piping of the addition system of silver nitrate aqueous solution was kept cold by circulating cold water outside the double pipe. The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically around the stirring axis, and were adjusted so as not to contact the reaction solution.

After completion of the addition of the sodium behenate solution, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm. Thus, silver behenate was obtained. The obtained solid content was stored as a wet cake without drying.
When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, it was a scaly crystal having an average projected area of 0.52 μm, an average particle thickness of 0.14 μm, and a sphere equivalent diameter variation coefficient of 15%.
19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to a wet cake corresponding to a dry solid content of 260 kg to make a total amount of 1000 kg, and then slurried with a dissolver blade. , PM-10 type).
Next, the pre-dispersed undiluted solution was adjusted three times by adjusting the pressure of the disperser (manufactured by Microfluidics International Corporation, trade name: Microfluidizer M-610, using Z-type interaction chamber) to 1260 kg / cm ^2. Processing was carried out to obtain a silver behenate dispersion A. The cooling operation was carried out by installing a serpentine heat exchanger before and after the interaction chamber, and adjusting the temperature of the refrigerant to a dispersion temperature of 18 ° C.

(Preparation of reducing agent dispersion A)
10 kg of reducing agent A (1,1-bis (2-hydroxy-3-tert-butyl-5-methylphenyl) -butane) and 10% by mass aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) To 16 kg, 7.2 kg of water was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed in a horizontal bead mill (IMM Co., Ltd., UVM-2) filled with zirconia beads having an average diameter of 0.5 mm for 4 hours 30 minutes, and then benzoisothiazolinone sodium salt 0.2 g and water were added to prepare a reducing agent A concentration of 25% by mass to obtain a reducing agent dispersion A. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.46 μm and a maximum particle size of 1.6 μm or less. The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of solid fine particle dispersion of organic polyhalogen compound A)
10 kg of organic polyhalogen compound A, 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203), 639 g of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, Surfynol 104E (Nissin) Chemical Co., Ltd.) 400 g, methanol 640 g and water 16 kg were added and mixed well to obtain a slurry. The slurry was fed with a diaphragm pump, dispersed in a horizontal bead mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then added with water to add organic polyhalogen compound A. Was prepared so as to have a concentration of 25% by mass to obtain a solid fine particle dispersion of organic polyhalogen compound A. The organic polyhalogen compound particles contained in the dispersion thus obtained had a median diameter of 0.36 μm, a maximum particle size of 2.0 μm or less, and an average particle size variation coefficient of 18%. The obtained dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of solid fine particle dispersion of organic polyhalogen compound B)
5 kg of organic polyhalogen compound B, 2.5 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203), 213 g of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, and 10 kg of water were added. Mix well to make a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal bead mill filled with zirconia beads having an average diameter of 0.5 mm (manufactured by Imex Co., Ltd., UVM-2), and then benzoisothiazolinone sodium salt2. 5 g and water were added so that the concentration of the organic polyhalogen compound B was 23.5% by mass to obtain a solid fine particle dispersion of the organic polyhalogen compound B. The organic polyhalogen compound particles contained in the dispersion thus obtained had a median diameter of 0.38 μm, a maximum particle size of 2.0 μm or less, and an average particle size variation coefficient of 20%. The obtained dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of 6-isopropylphthalazine compound dispersion)
While stirring 62.35 g of water at room temperature, 2.0 g of modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., Poval MP203) was added so as not to be agglomerated, and mixed with stirring for 10 minutes. Thereafter, the mixture was heated and heated up until the internal temperature reached 50 ° C., and then stirred for 90 minutes in the range of the internal temperature of 50 to 60 ° C. to be uniformly dissolved. The internal temperature was lowered to 40 ° C. or lower, 25.5 g of a 10% by weight aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., PVA-217), 3.0 g of a 20% by weight aqueous solution of sodium tripropylnaphthalenesulfonate, and 6- 7.15 g of isopropyl phthalazine (70% by mass aqueous solution) was added and stirred for 30 minutes to obtain 100 g of a transparent dispersion. The obtained dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of solid fine particle dispersion of development accelerator W)
10 kg of development accelerator W, 10 kg of a 20% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and 20 kg of water were added and mixed well to obtain a slurry. The slurry was fed with a diaphragm pump, dispersed in a horizontal bead mill (IMM Co., Ltd., UVM-2) filled with zirconia beads having an average diameter of 0.5 mm for 5 hours, and then water was added to add the development accelerator W. The concentration was adjusted to 20% by mass to obtain a solid fine particle dispersion of development accelerator W. The development accelerator particles contained in the dispersion thus obtained had a median diameter of 0.5 μm, a maximum particle size of 2.0 μm or less, and an average particle size variation coefficient of 18%. The obtained dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of binder liquid)
(Binder of the present invention)
Each of the polymer latexes of the exemplary compounds (P-1), (P-8), (P-16), (P-22), and (P-28) is pH 8.35 using 25% NH ₄ OH. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored to prepare a binder liquid having a solid content concentration of 44 mass%.
(Comparative binder RP-1) (SBR)
As a binder of a comparative sample, an exemplary compound (P-1) described in JP-A-2002-229149 was synthesized and prepared in the same manner as above to obtain a comparative binder RP-1 (styrene / butadiene / acrylic acid = 68 / 29/3 mass%, Tg = 17 ° C., solid content 44 mass%, average particle size 80 nm).
(Comparative binder RP-2)
In Synthesis Example 1 described in JP-A-2002-229149, a polymer latex was synthesized by changing the monomer to 496.8 g of styrene, 27 g of isoprene, and 16.2 g of acrylic acid, and was prepared in the same manner as described above. The binder was RP-2 (styrene / isoprene / acrylic acid = 92/5/3 mass%, Tg = 86 ° C., solid content 44 mass%, average particle diameter 115 nm).
(Comparative binder RP-3)
In Synthesis Example 2 described in JP-A-2002-229149, a polymer latex was synthesized by changing the monomer to 118.8 g of styrene, 405 g of isoprene, and 16.2 g of acrylic acid, and was prepared in the same manner as described above. Binder RP-3 was obtained (styrene / isoprene / acrylic acid = 22/75/3 mass%, Tg = −40 ° C., solid content 44 mass%, particle size 108 nm).

(3-2) Preparation of coating solution (preparation of image forming layer coating solution)
Using the material prepared above, with respect to 1 mol of silver of silver behenate dispersion A, the material was added as follows, and water was added to obtain an image forming layer coating solution. After completion, vacuum degassing was performed at a pressure of 0.54 atm for 45 minutes. The coating solution had a pH of 7.7 and a viscosity of 50 mPa · s at 25 ° C.
Binder (described in Table 1) 397g
Reducing agent A As solid content 149.5g
Organic polyhalogen compound A 3.1 g as solid content
Organic polyhalogen compound B 1.9 g as solid content
Sodium ethylthiosulfonate 0.47g
Benzotriazole 1.02g
Polyvinyl alcohol (Kuraray Co., Ltd., PVA-235) 10.8 g
6-isopropylphthalazine 15.0 g
Silver halide emulsion A 0.06 mol as Ag amount
Compound A as preservative
40ppm in coating solution (2.5mg / m ² as coating amount)
1% by mass as the total amount of solvent in the methanol coating solution
2% by mass as the total amount of solvent in the ethanol coating solution
(Preparation of protective layer coating solution)
Polymer latex of copolymer having a structure of methyl methacrylate / styrene / 2-ethylhexyl acrylate / 2-hydroxyethyl methacrylate / acrylic acid = 58.9 / 8.6 / 25.4 / 5.1 / 2 (mass%) Solution (copolymer glass transition temperature 46 ° C. (calculated value), solid content concentration 21.5% by mass, compound A containing 100 ppm, and compound B as a film-forming aid of 15% by mass with respect to the solid content of the latex The glass transition temperature of the coating solution was 24 ° C. Water was added to 943 g of an average particle size of 116 nm, 1.62 g of Compound C, and sodium dihydrogen orthophosphate dihydrate as a solid content of 0.03 g. 69 g, 11.55 g of development accelerator W as solid content, matting agent (polystyrene particles, average particle size 7 μm, variation in particle size distribution) 8%) 1.58 g of polyvinyl alcohol (Kuraray Co., Ltd., added PVA-235) 29.3 g, was prepared further coating solution by adding water to (a methanol solvent containing 0.8% by mass of). After completion, vacuum degassing was performed at a pressure of 0.47 atm for 60 minutes. The coating solution had a pH of 5.5 and a viscosity of 45 mPa · s at 25 ° C.

(Preparation of overcoat first layer coating solution)
Polymer latex of copolymer having a structure of methyl methacrylate / styrene / 2-ethylhexyl acrylate / 2-hydroxyethyl methacrylate / acrylic acid = 58.9 / 8.6 / 25.4 / 5.1 / 2 (mass%) Solution (copolymer glass transition temperature 46 ° C. (calculated value), solid content concentration 21.5% by mass, compound A containing 100 ppm, and compound B as a film-forming aid of 15% by mass with respect to the solid content of the latex The glass transition temperature of the coating solution was 24 ° C. Water was added to 625 g of an average particle size of 74 nm, 11.7 g of compound D, 2.7 g of compound F, and polyvinyl alcohol (manufactured by Kuraray Co., Ltd.). 11.5 g of PVA-235) was added, and water was further added to prepare a coating solution (containing 0.1% by mass of methanol solvent). After completion, vacuum degassing was performed at a pressure of 0.47 atm for 60 minutes. The coating solution had a pH of 2.6 and a viscosity of 30 mPa · s at 25 ° C.
(Preparation of overcoat second layer coating solution)
Polymer latex of copolymer having a structure of methyl methacrylate / styrene / 2-ethylhexyl acrylate / 2-hydroxyethyl methacrylate / acrylic acid = 58.9 / 8.6 / 25.4 / 5.1 / 2 (mass%) Solution (copolymer glass transition temperature 46 ° C. (calculated value), solid content concentration 21.5% by mass, compound A containing 100 ppm, and compound B as a film-forming aid of 15% by mass with respect to the solid content of the latex Water was added to 649 g of an average particle size of 116 nm with a glass transition temperature of 24 ° C. of the coating solution, and 30 mass of carnauba wax (manufactured by Chukyo Yushi Co., Ltd., Cellosol 524: silicone content less than 5 ppm). % Solution 18.4 g, compound C 1.85 g, compound E 1.0 g, matting agent (polystyrene particles, average particle size) 7 μm, particle size distribution coefficient of variation 8%) 3.45 g and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-235) 26.5 g were added, water was further added, and the coating liquid (methanol solvent was 1.1 mass). % Content) was prepared. After completion, vacuum degassing was performed at a pressure of 0.47 atm for 60 minutes. The coating solution had a pH of 5.3 and a viscosity of 25 mPa · s at 25 ° C.

(3-3) Coating (1) Preparation of Sample Nos. 4 to 8 of the Present Invention Using a slide beat coating method on the opposite side of the back layer of the support provided with the back layer of Sample-1 of the present invention. Then, the image forming layer coating solution is applied so that the silver coating amount is 1.5 g / m ² , and the protective layer coating solution is further coated thereon with a polymer latex solid content coating amount of 1.29 g / m ^2. The image forming layer coating solution and the protective layer coating solution were simultaneously applied in a multilayer manner. Thereafter, the overcoat first layer coating solution is applied onto the protective layer so that the solid content of the polymer latex is 1.97 g / m ² , and the overcoat second layer coating solution is further polymerized thereon. The overcoat first layer coating solution and the overcoat second layer coating solution were simultaneously applied in layers such that the solid content coating amount of the latex was 1.07 g / m ² to prepare a heat-developable image recording material. Drying at the time of coating is performed in the horizontal drying zone (coating machine) until the drying point near the point where the flow rate of the coating liquid almost disappears in the range of the dew point 14 to 25 ° C. and the liquid film surface temperature 35 to 40 ° C. The support was carried out at an angle of 1.5 ° to 3 ° with respect to the horizontal direction. Winding after drying is performed under conditions of a temperature of 23 ± 5 ° C. and a relative humidity of 45 ± 5%, and the winding shape is adjusted to the subsequent processing mode (image forming layer side outer winding), with the image forming layer side facing outward. did. The relative humidity of the heat-developable photosensitive material package is 20 to 40% (measured at 25 ° C.), the film surface pH of the obtained heat-developable image recording material is 5.0, and the Beck smoothness is 850. Second, the film pH on the opposite side was 5.9, and the Beck smoothness was 560 seconds.

(2) Preparation of Comparative Samples Nos. 1 to 3 A heat-developable image was obtained in the same manner as Samples Nos. 4 to 8 of the present invention except that the support provided with the back layer of Comparative Sample-A was used. A recording material was prepared.
In Comparative Sample No. 1, 5 g of the following nucleating agent was added during the preparation of the image forming layer coating solution.

4). Evaluation of Photographic Performance (4-1) Photographic Performance The obtained sample is a single-channel cylindrical inner surface type equipped with a semiconductor laser having a beam diameter (FWHM of 1/2 of the beam intensity) of 12.56 μm, a laser output of 30 mW, and an output wavelength of 410 nm. Were used, and the exposure was performed at a mirror rotational speed of 60,000 rpm and an exposure time of 1.2 × 10 ⁻⁸ seconds. The overlap coefficient at this time was 0.449, and the laser energy density on the surface of the heat-developable image recording material was 45 μJ / cm ² .
Using the above laser exposure apparatus, a test step was output while changing the amount of light at 175 lines / inch. As an index (gamma) indicating the contrast of an image, a point of fog + density 1.5 to a point of fog + density 1.5 of the characteristic curve are connected by a straight line, and the slope of this straight line is represented as a gamma value. Density measurement was performed with a Macbeth TD904 densitometer (visible density). Sensitivity represents with the exposure amount of the logarithm of giving a density 1.5 and the S _1.5. The higher the value, the higher the sensitivity.
(4-2) Processing Humidity Dependence Using the above-described exposure apparatus, a photothermographic material left for 16 hours in an environment of 23 ° C. and a relative humidity of 80% was subjected to a line width exposure of 27 μm at 909 LPI, and 23 ° C. The above heat development processing was performed in an 80% relative humidity environment. The photothermographic material left for 16 hours in an environment of 23 ° C. and a relative humidity of 20% is drawn with a character line width of 909 LPI, and subjected to the above heat development processing in an environment of 23 ° C. and a relative humidity of 20%. Variation was measured with a 100X loupe.
A smaller line width variation is better.
(4-3) UV density The film was subjected to a heat development treatment at 115 ° C. for 20 seconds without exposure, and then the UV density of the film was measured. The measurement is a UV density by a Macbeth densitometer.
Table 1 shows the results evaluated as described above.

  As is apparent from Table 1, the photothermographic material of the present invention has super high contrast and high sensitivity, and has improved environmental humidity dependency.

Example 2
In place of the back layer coating solution used in the preparation of Sample No. 8 in Example 1, gelatin 17 g, polyacrylamide 9.6 g, solid fine particle dispersion 100 g of the following base precursor, and solid fine particle dispersion of the dye (1) described above Back layer prepared by mixing 56 g of liquid, 1.5 g of monodispersed polymethyl methacrylate particles (average particle size 8 μm) as a matting agent, 0.03 g of preservative benzoisothiazolinone, 2.2 g of sodium polyethylenesulfonate, and 844 ml of water Samples Nos. 9 to 13 were produced in the same manner as Sample No. 8, except that the coating solution was used.
(Preparation of solid fine particle dispersion of base precursor)
64 g of a base precursor compound (described in Table 2), 28 g of diphenylsulfone, and 10 g of a surfactant (manufactured by Kao Corporation, Demol N) are mixed with 220 ml of distilled water, and the mixture is mixed with a sand mill (manufactured by Imex Corporation, 1/4 Gallon). Using a sand grinder mill), beads were dispersed to obtain a solid fine particle dispersion of a base precursor compound having an average particle size of 0.2 μm.
About obtained sample No. 9-13, it carried out similarly to Example 1, and evaluated UV concentration. The obtained results are shown in Table 2. For reference, the results of Sample No. 8 are also shown.

Claims (4)

On the support, a non-photosensitive organic silver salt, a reducing agent for the organic silver salt, a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol%, and 0.1 mol per mol of non-photosensitive organic silver A binder containing an image forming layer containing the following halogen precursor, and containing a polymer obtained by copolymerizing 10% by mass or more and 70% by mass or less of a monomer represented by the following general formula (M) as a binder of the image forming layer is used. A heat-developable image recording material.
General formula (M)
CH ₂ = CR ₀₁ -CR ₀₂ = CH ₂
(In the formula, R ₀₁ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group, and R ₀₂ represents an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group.) 2. The heat-developable image recording material according to claim 1, wherein the halogen precursor is contained in an amount of 1.0 × 10 ⁻⁴ mol to 0.05 mol per mol of non-photosensitive organic silver. A back layer containing a dye represented by the following general formula (1) or (2) is provided, and is exposed to light having a wavelength of 500 nm or less and then thermally developed at a temperature of 100 ° C. to 150 ° C. The heat-developable image recording material according to claim 1 or 2, wherein an image having a gamma of 7 or more is formed.

(Wherein R ¹ is a hydrogen atom, an aliphatic group, an aromatic group, —NR ²¹ R ²⁶ , —OR ²¹ or —SR ²¹ (wherein R ²¹ and R ²⁶ are each independently a hydrogen atom, an aliphatic group, Or an aromatic group, and R ²¹ and R ²⁶ may form a nitrogen-containing heterocycle in cooperation with each other.
R ² represents a hydrogen atom, an aliphatic group or an aromatic group. L ¹ and L ² each independently represents a substituted or unsubstituted methine group. Moreover, the substituent of the substituted methine group represented by L ¹ and L ² may be one in which the substituents are bonded to each other to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. Z ¹ represents an atomic group necessary for completing a 5-membered or 6-membered nitrogen-containing heterocyclic ring. The nitrogen-containing heterocycle may have an aromatic ring as a condensed ring. Further, the nitrogen-containing heterocycle and its condensed ring may have a substituent.
A represents an acidic nucleus, and B represents an aromatic group, an unsaturated heterocyclic group, or a group represented by the following general formula (3). n and m each represent 1 or 2.

(In the formula, L ³ represents a substituted or unsubstituted methine group. L ³ may be bonded to L ² to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. R ³ represents a fatty acid. Z ² represents an atomic group necessary to complete a 5- or 6-membered nitrogen-containing heterocycle, and the nitrogen-containing heterocycle has an aromatic ring as a condensed ring. In addition, the nitrogen-containing heterocycle and its condensed ring may have a substituent.))   The heat-developable image recording material according to any one of claims 1 to 3, wherein a back layer containing a base precursor is provided.