JP2006171612A - Heat-developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-developable photosensitive material that is superior in humidity dependence in development and in raw stock preservability. <P>SOLUTION: The heat developable photosensitive material has on a support an image forming layer, containing a photosensitive silver halide having a silver iodide content of 40-100 mol%, a non-photosensitive organic silver salt other than the silver salts of carboxylic acids, a reducing agent and a hydrophilic binder, and has a back layer, containing a dye represented by Formula (1) or Formula (2) on a side of the support opposite to the image forming layer, wherein an image whose gamma is ≥7 can be formed, by heat-developing the heat developable photosensitive material at 100-150°C after exposure with a light having a wavelength ≤500 nm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material, and more particularly to a photothermographic material having improved raw storage stability and processing humidity dependency.

  Silver halide photosensitive materials that have been widely used in the past are used in the field of image formation as a broader and higher quality material due to their excellent photographic properties, but development, fixing, The process of washing with water and drying is necessary, and the processing steps are wet, so that the work is complicated. For this reason, a photothermographic material in which the development process is performed by heat treatment has been developed and put into practical use, and in recent years, it has been rapidly spread mainly in the printing industry or the medical industry.

  As such a technique, a photothermographic material having an organic silver salt, photosensitive silver halide grains and a reducing agent on a support is known. Since this photothermographic material does not use any solution processing chemicals, a simpler system can be provided to the user.

  In particular, in the field of printing plate making, waste liquids resulting from wet processing of image-forming photosensitive materials have become operational problems. In recent years, reduction of processing waste liquids is strongly desired from the viewpoint of environmental conservation and space saving.

  In the photothermographic material, as described above, all chemical substances necessary for development are incorporated in the photosensitive material, and an image can be formed by simply applying heat without using a processing solution. It has characteristics. Therefore, with respect to the development processing humidity dependency, raw storage stability (storage stability before exposure and development) of unused photothermographic material, and storage stability of the image after processing, it is compared with photosensitive materials that require conventional processing solutions. Have a lot of handicap and a lot of effort has been put into improving it.

In particular, in the photothermographic material, it is well known that the photographic performance fluctuates depending on the environmental humidity during development and raw storage, and various techniques have been disclosed to improve this, but none of them is sufficient. (For example, see Patent Documents 1, 2, 3, and 4).
JP 2002-258436 A JP 2002-229153 A JP 2002-90935 A JP 2002-55409 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photothermographic material that is excellent in development processing humidity dependency and excellent in raw storage stability.

  The above object of the present invention can be achieved by the following constitution.

(Claim 1)
An image forming layer containing a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol% on the support, a non-photosensitive organic silver salt other than the silver carboxylate, a reducing agent, and a hydrophilic binder. And having a back layer containing a dye represented by the following general formula (1) or (2) on the surface opposite to the image forming layer and exposing with light having a wavelength of 500 nm or less A photothermographic material, wherein an image having a gamma of 7 or more can be formed by heat development at a temperature of 100 ° C to 150 ° C.

(In the formula, R ¹ is a hydrogen atom, an aliphatic group, an aromatic group, —NR ²¹ R ²⁶ , —OR ²¹ , or —SR ²¹ , and R ²¹ and R ²⁶ are each independently a hydrogen atom or an aliphatic group. Or R ²¹ and R ²⁶ are combined to form a nitrogen-containing heterocyclic ring; R ² is a hydrogen atom, an aliphatic group or an aromatic group; and L ¹ and L ² are Each independently a substituted or unsubstituted methine group, and the substituents of the methine group may be bonded to each other to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring; Z ¹ is a 5-membered or 6-membered group Is an atomic group necessary for completing the nitrogen-containing heterocycle, and the nitrogen-containing heterocycle may be condensed with an aromatic ring, and the nitrogen-containing heterocycle and the condensed ring have a substituent. A represents an acidic nucleus, and B represents an aromatic group, an unsaturated heterocyclic group, or the following general formula (3). , M represents 1 or 2, respectively.

In the formula, L ³ is a substituted or unsubstituted methine group, and may combine with L ² to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. R ³ represents an aliphatic group or an aromatic group. Z ² is an atomic group necessary to complete a 5-membered or 6-membered nitrogen-containing heterocyclic ring, and the nitrogen-containing heterocyclic ring may be condensed with an aromatic ring, and the nitrogen-containing heterocyclic ring and its condensed The ring may have a substituent. )
(Claim 2)
2. The photothermographic material according to claim 1, wherein the reducing agent is a reducing agent represented by the following general formula (A).

(In the formula, R ^{1 to} R ⁴ each independently represent a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group. R ⁵ represents a hydrogen atom or an aliphatic group. X ¹ , X ² Each independently represents a hydrogen atom or a group that can be substituted on the benzene ring, provided that R ¹ and R ² are not simultaneously hydrogen atoms, and R ³ and R ⁴ are not simultaneously hydrogen atoms. .)

  According to the present invention, it is possible to provide a photothermographic material excellent in development processing humidity dependency and excellent in raw storability.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

  The photothermographic material of the present invention comprises a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol%, a non-photosensitive organic silver salt other than a silver carboxylate, a reducing agent, and a hydrophilic agent on a support. Having a back layer containing a dye represented by the general formula (1) or (2) on the surface opposite to the image forming layer. Is exposed to light having a wavelength of 500 nm or less, and is then thermally developed at a temperature of 100 ° C. to 150 ° C., whereby an image having a gamma of 7 or more can be formed.

  Moreover, it is preferable that the said reducing agent is a reducing agent represented by the said general formula (A).

(Photosensitive silver halide)
In the present invention, a high silver iodide emulsion having an iodine content of 40 mol% to 100 mol% is used as the silver halide grains. The remaining 60 mol% is not particularly limited and can be selected from silver chloride and silver bromide, but silver bromide is particularly preferable. By using such a high silver iodide emulsion, it is possible to design a preferable photothermographic 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 optical image storage stability after processing, the silver iodide content is more preferably 70 mol% to 100 mol%, still more preferably 80 mol% to 100 mol%, and 90 mol% to 100 mol%. Particularly preferred. The distribution of the halogen composition in the grain may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Further, silver halide grains having a core / shell structure can be preferably used. A preferable structure is a 2- to 5-fold structure, and more preferably 2- to 4-fold core / shell particles can be used. A 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 size of the high silver iodide emulsion used in the present invention is preferably 5 nm to 90 nm. Larger silver halide sizes increase the amount of silver halide coating required to achieve the required maximum density. The silver iodide emulsion preferably used in the present invention is not preferred when the coating amount is large, because development is remarkably suppressed and the sensitivity is lowered, and density stability with respect to development time is deteriorated. For this reason, the maximum density cannot be obtained within a predetermined development time when the particle size exceeds a certain level. On the other hand, if the amount of addition is limited, it has sufficient developability despite silver iodide. Thus, it is preferable that the size of the silver halide grains is sufficiently small in order to achieve a sufficient maximum optical density while adding silver iodide. Further preferable silver halide grain sizes are 5 nm to 70 nm, and more preferably 5 nm to 55 nm. Especially preferably, it is 10 nm-45 nm. The term “particle size” as used herein means an average diameter when converted into a circular image having the same area as the projected area observed with an electron microscope. The coating amount of such silver halide grains is preferably 0.001 mol to 1.0 mol, more preferably 0.005 mol to 0.50 mol, and still more preferably 0, per 1 mol of silver of the non-photosensitive organic acid silver salt described later. 0.01 mol to 0.20 mol. In order to suppress the remarkable development inhibition by the high silver iodide emulsion, selection of this addition amount is important.

  Methods for forming photosensitive silver halide are well known in the art, such as those described in Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458. Specifically, a method in which a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound to gelatin or another polymer solution and then mixed with an organic silver salt is used. . Moreover, the method described in paragraph Nos. 0217 to 0224 of JP-A-11-119374, JP-A-11-252627, and JP-A-2000-347335 are also preferable.

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

  The hexacyano metal complex is present in the form of ions in aqueous solution, so the counter cation is not important, but it is easy to mix with water and is suitable for precipitation of silver halide emulsions. Sodium ion, potassium ion, rubidium It is preferable to use alkali metal ions such as ions, cesium ions, and lithium ions, ammonium ions, 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. These heavy metals and metal complexes and methods for adding them are described in JP-A-7-225449, JP-A-11-65021, paragraphs 0018 to 0024, and JP-A-11-119374, paragraphs 0227 to 0240. Yes.

Further, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a desalting method and a sensitizing method of a silver halide emulsion which can be contained in the silver halide grains used in the present invention, JP-A No. 11-101. No. 84574, paragraph numbers 0046 to 0050, JP-A-11-65021, paragraph numbers 0025 to 0031, and JP-A-11-119374, paragraph numbers 0242 to 0250. 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 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 depending on the photosensitive silver halide grains, chemical ripening conditions, etc., but generally 1 mol of silver halide Per 10 ⁻⁸ to 10 ⁻² mol, preferably about 10 ⁻⁷ to 10 ⁻³ mol. 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 may be used after reduction sensitization. Specific examples of compounds used for reduction sensitization include ascorbic acid, thiourea dioxide, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, and polyamine compounds. Further, reduction sensitization can be carried out by maintaining the pH of the photosensitive silver halide emulsion at 7 or higher, or by ripening while maintaining the pAg 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 forming silver halide grains 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 different conditions for chemical sensitization). Etc.) 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 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.

(Non-photosensitive organic silver salt (non-photosensitive non-carboxylic acid silver salt))
The non-photosensitive organic silver salt (non-photosensitive reducible silver ion source) used in the photothermographic material of the present invention does not contain a carboxylate group but contains reducible silver (1+) ions. Any organic compound may be used. Preferably, the silver ion source is relatively stable to light and forms a silver image when heated to 50 ° C. or higher in the presence of an exposed photocatalyst (eg, silver halide) and a reducing composition. It is an organic silver salt.

  A silver salt of a compound containing an imino group is particularly preferred in the (aqueous) photothermographic material used in the practice of the present invention. Preferred examples of these compounds include silver salts of benzotriazole and substituted derivatives thereof (eg, silver methylbenzotriazole and silver 5-chlorobenzotriazole), 1,2,4-triazole or 1-H-tetrazole, such as Silver salts of phenylmercaptotetrazole as described in US Pat. No. 4,220,709 (deMauriac) and described in US Pat. No. 4,260,677 (Winslow et al.) Examples thereof include silver salts of imidazole and imidazole derivatives. Particularly preferred are silver salts of benzotriazole and substituted derivatives thereof. Most preferred is a silver salt of benzotriazole.

  Silver salts of compounds containing a mercapto group or thione group, and silver salts of these derivatives can also be used. Preferred compounds of this type contain a heterocyclic nucleus having 5 or 6 ring atoms. Of these atoms, at least one is a nitrogen atom and the other atoms are carbon, oxygen or sulfur atoms. Examples of such heterocyclic nuclei include triazole, oxazole, thiazole, thiazoline, imidazole, diazole, pyridine and triazine.

  The non-photosensitive organic silver salt according to the present invention can also be provided as a core-shell type silver salt as described in US Pat. No. 6,355,408 (Whitcomb et al.). These silver salts include a core composed of one or more silver salts and a shell having one or more different silver salts.

  Yet another non-photosensitive organic silver salt useful in the practice of the present invention is a silver dimer compound. These silver dimer compounds include two different silver salts as described in US Pat. No. 6,472,131 (Whitcomb). Such a non-photosensitive silver dimer compound contains two different silver salts, provided that these two different silver salts contain a linear saturated hydrocarbon group as a silver ligand. These ligands are different in the number of carbon atoms by 6 or more.

  The non-photosensitive organic silver salt according to the present invention can contain various mixtures of various silver salt compounds described herein in any desired ratio. However, when a mixture of silver salts is used, it is preferred that at least 50 mole percent of the total silver salt consists of the silver salt of the compound containing the imino group described above.

The non-photosensitive organic silver salt according to the present invention is preferably used in an amount of 5% to 70% by weight, more preferably 10% to 50% by weight, based on the total dry weight of the emulsion layer. . That is, it is generally used in an amount of 0.001 to 0.2 mol / m ² of the photothermographic material, preferably 0.01 to 0.05 mol / m ² of the material.

The total amount of silver (obtained from all silver sources) in the photothermographic material is generally at least 0.002 mol / m ² , preferably 0.01 to 0.05 mol / m ² .

(Reducing agent)
A reducing agent (or a reducing agent composition comprising two or more components) for a non-photosensitive organic silver salt (reducible silver ion source) is an arbitrary capable of reducing silver (I) ions to metallic silver Or an organic material.

  Reducing agents include conventional photographic developers such as aromatic di- and tri-hydroxy compounds (eg hydroquinone, gallic acid and gallic acid derivatives, catechol and pyrogallol), aminophenols (eg N-methylaminophenol), sulfones. Amidophenol, p-phenylenediamine, alkoxy naphthol (for example, 4-methoxy-1-naphthol), pyrazolidin-3-one type reducing agent (for example, PHENIDONE (registered trademark)), pyrazolin-5-one, polyhydroxyspiro-bis- Indan, indan-1,3-dione derivatives, hydroxytetronic acid, hydroxytetronimide, hydroxylamine derivatives (eg, US Pat. No. 4,082,901 (Laridon et al.)), Hydrazine derivatives, hindered Phenol, amidoxime, azines, reductones (e.g., ascorbic acid and ascorbic acid derivatives), leuco dyes, and other materials readily apparent to those skilled in the art may be used.

  Ascorbic acid reducing agent is preferred when silver benzotriazole is used as the non-photosensitive organic silver salt. “Ascorbic acid” reducing agent (also called developer or developing agent) means ascorbic acid, complexes thereof and derivatives thereof. Ascorbic acid developing agents are described in a number of publications in the photographic process, such as US Pat. No. 5,236,816 (Purol et al.) And references cited therein.

  The reducing agent composition includes two or more components, such as a hindered phenol developer, and a co-developer that can be selected from the various classes of reducing agents described below. Ternary developer mixtures that also take into account the addition of contrast accelerators are also useful. Such contrast promoters can be selected from the following various classes of reducing agents.

  The reducing agent (or mixture thereof) described herein is generally present as 1-10% (dry weight) of the emulsion layer. In a multilayer structure, when the reducing agent is added to a layer other than the emulsion layer, it is more desirable that the reducing agent is present in a slightly higher ratio of 2 to 15% by mass. Any co-developer may generally be present in an amount from 0.001% to 1.5% (dry weight) of the emulsion layer coating.

In the present invention, the reducing agent represented by the general formula (A) can be preferably used as the reducing agent for the organic silver salt. In the photothermographic material of the invention, only one type of compound represented by the general formula (A) may be used, or two or more types may be used in combination. In the formula, R ^{1 to} R ⁴ each independently represent a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group. R ⁵ represents a hydrogen atom or an aliphatic group. X ¹ and X ² each independently represent a hydrogen atom or a group that can be substituted on a benzene ring. However, R ¹ and R ² are not simultaneously hydrogen atoms, and R ³ and R ⁴ are not simultaneously hydrogen atoms.

Examples of the aliphatic group for R ^{1 to} R ⁴ include a substituted or unsubstituted alkyl group or an allyl group. These preferable carbon number is 1-20, and as a substituent, aryl group, hydroxy group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl Preferred examples include a group, a carbamoyl group, an ester group, a ureido group, a urethane group, and a halogen atom. Particularly preferred is an unsubstituted alkyl group or a benzyl group. Examples of the aromatic group of R ^{1 to} R ⁴ include a substituted or unsubstituted phenyl group and naphthyl group. Preferable substituents include those listed as examples of the above-described aliphatic group substituents. A particularly preferred aromatic group is a phenyl group. The heterocyclic group of R ^{1 to} R ⁴ is a saturated or unsaturated heterocyclic group, and includes nitrogen, oxygen, or sulfur as a hetero atom. Preferable examples include a pyridyl group, a pyrrole group, a pyrimidyl group, a furan group, a thiophene group, a morpholino group, and an imidazole group. Particularly preferred is a pyridyl group.

R ⁵ represents a hydrogen atom or an aliphatic group. Preferred examples of the aliphatic group represented by R ⁵ are selected from those exemplified as the aliphatic groups represented by R ^{1 to} R ⁴ . R ⁵ is particularly preferably a hydrogen atom.

X ¹ and X ² each independently represent a hydrogen atom or a group that can be substituted on a benzene ring. Examples of preferred substituents include an alkyl group having 1 to 30 carbon atoms, an aryl group having 1 to 30 carbon atoms, a halogen atom, an alkoxy group having 1 to 30 carbon atoms, and an acylamino group having 1 to 30 carbon atoms. Is mentioned. X ¹ and X ² are particularly preferably a hydrogen atom and an alkyl group having 1 to 30 carbon atoms.

  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 addition amount of the reducing agent is preferably 0.01 to 100 mol, more preferably 0.1 to 10 mol, per mol of the organic silver salt in the image forming layer. The reducing agent used in the present invention 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, it is preferable to use together with a reducing agent a non-reducing compound having a group capable of forming a hydrogen bond with an aromatic hydroxyl group (—OH) (hereinafter referred to as a hydrogen bonding compound). . 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 H)), a urethane group. (However, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a ureido group (however, it does not have a> N—H group, N-Ra (Ra is a substituent other than H).)

  In the present invention, 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 R21 to R23 have a substituent, examples of the substituent include a halogen atom, alkyl group, aryl group, alkoxy group, amino group, acyl group, acylamino group, alkylthio group, arylthio group, sulfonamide group, acyloxy group, oxy Examples include a carbonyl 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, a tert-butyl group. Examples include an octyl group, a phenyl group, a 4-alkoxyphenyl group, and a 4-acyloxyphenyl group.

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. Alkoxy groups include methoxy, ethoxy, butoxy, octyloxy, 2-ethylhexyloxy, 3,5,5-trimethylhexyloxy, dodecyloxy, cyclohexyloxy, 4-methylcyclohexyloxy, benzyl An oxy group etc. are mentioned. Examples of the aryloxy group include a phenoxy group, a cresyloxy group, an isopropylphenoxy group, a 4-tert-butylphenoxy group, a naphthoxy group, and a biphenyloxy group. Examples of the amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, a dioctylamino group, an N-methyl-N-hexylamino group, a dicyclohexylamino group, a diphenylamino group, and an N-methyl-N-phenylamino group. It is done.

R ^{21 to} R ²³ are preferably an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. In terms of the effects of the present invention, at least one of R ^{21 to} R ²³ is preferably an alkyl group or an aryl group, and more preferably two or more are an alkyl group or an aryl group. Moreover, the case where R < ²¹ > -R < ²³ > is the same group from the point that it can obtain cheaply.

  Specific examples of the hydrogen bonding compound including the compound of the general formula (D) in the present invention are shown below, but the hydrogen bonding compound that can be used in the present invention is not limited to these.

  Specific examples of the hydrogen bonding compound include those described in Japanese Patent Application Nos. 2000-192191 and 2000-19481 in addition to those described above.

  The compound of the general formula (D) can be applied by being contained in a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersion fine particle dispersion, as with the reducing agent. The compound of the general formula (D) forms a hydrogen-bonding complex with the compound having a phenolic hydroxyl group in a solution state, and depending on the combination of the reducing agent and the compound of the general formula (D) of the present invention, It can be isolated in the crystalline state. The use of the crystal powder isolated in this way as a solid-dispersed fine particle dispersion is particularly preferable for obtaining stable performance. Further, a method in which a reducing agent and a compound of the general formula (D) are mixed as a powder and complexed at the time of dispersion with a sand grinder mill or the like using an appropriate dispersant can be preferably used. It is preferable to use the compound of General formula (D) in the range of 1-200 mol% with respect to a reducing agent, More preferably, it is the range of 10-150 mol%, More preferably, it is the range of 30-100 mol%.

  In the photothermographic material of the invention, other reducing agents may be used in combination with the reducing agent represented by the general formula (A) as a reducing agent. As another reducing agent, it is preferable to use a hindered phenol compound which has at least one phenolic hydroxyl group and whose ortho position is 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 JP-A-9-274274, [0062] to [0074], It is a compound represented by (IVa), (IVb).

  When a hindered phenol compound is used in combination, the amount used is preferably 1/100 to 10 times, more preferably 1/50 to 5 times in terms of moles with respect to the reducing agent represented by the general formula (A). More preferably, it is 1/20 to 2 times.

  The photothermographic material of the invention may further be protected against fog formation and may be stabilized against loss of sensitivity during storage.

  The photothermographic material may contain one or more polyhalo antifoggants. The antifoggant contains one or more polyhalo substituents such as dichloro, dibromo, trichloro and tribromo groups. Antifoggants may be aliphatic, alicyclic or aromatic compounds including aromatic heterocyclic compounds and carbocyclic compounds.

Particularly useful antifoggants of this type are polyhalo antifoggants, such as polyhalo antifoggants having —SO ₂ C (X ′) 3 groups, where X ′ represents the same or different halogen atoms.

US patent application Ser. No. 10 / 014,961 describes another class of useful antifoggants. These compounds are generally defined as compounds having a pKa of 8 or less and are represented by the following general formula G:
General formula G
_{^{R 1 -SO 2 -C (R 2}} ) R 3 - (CO) m - (L 1) n -SG
In the general formula G, R ¹ is an aliphatic group or a cyclic group, and R ² and R ³ are each independently hydrogen or bromine, but at least one of these is bromine, and L ¹ is It is an aliphatic divalent linking group, m and n are independently 0 or 1, and SG is a solubilizing group having a pKa of 8 or less.

  In order to improve the reaction speed of the silver development oxidation-reduction reaction at a high temperature, the photothermographic material of the invention also contains one or more thermal solvents (“heat solvent”, “thermosolvent”, “melt former”, It is advantageous to include "melt modifiers", "eutectic formers", "development modifiers", "waxes" or "plasticizers").

  The term “thermal solvent” in the present invention means an organic material that becomes a plasticizer or a liquid solvent for at least one of the image forming layers when heated at a temperature above 60 ° C. Useful for such purposes are polyethylene glycols having an average molecular weight in the range of 1,500 to 20,000 described in US Pat. No. 3,347,675. In addition, U.S. Pat. No. 3,667,959 describes compounds such as urea, methylsulfonamide and ethylene carbonate as thermal solvents, Research Disclosure, December 1976, paragraph 15027, paragraph 26. On page -28, tetrahydro-thiophene-1,1-dioxide, methyl anisate and 1,10-decanediol are described as hot solvents. Other representative examples of such compounds include niacinamide, hydantoin, 5,5-dimethylhydantoin, salicylanilide, phthalimide, N-hydroxyphthalimide, N-potassium-phthalimide, succinimide, N-hydroxy-1,8- Naphthalimide, phthalazine, 1- (2H) -phthalazinone, 2-acetylphthalazinone, benzanilide, 1,3-dimethylurea, 1,3-diethylurea, 1,3-diallylurea, meso-erythritol, D-sorbitol , Tetrahydro-2-pyrimidone, glycoluril, 2-imidazolidone, 2-imidazolidone-4-carboxylic acid and benzenesulfonamide. A combination of these compounds, for example, a combination of succinimide and 1,3-dimethylurea can also be used. For example, U.S. Patent Nos. 6,013,420 (Windender), 3,438,776 (Yudelson), 5,368,979 (Freedman et al.), 5,716. , 772 (Taguch et al.), 5,250,386 (Aono et al.), And Research Disclosure, December 1976, paragraph 15022, disclose known thermal solvents.

(toner)
“Toner” is a compound that improves the image color by participating in the formation of a black image during development. The toner also increases the optical density of the developed image. Without toner, the image is often pale and yellow or brown. Therefore, it is preferable to use “toners” or derivatives thereof that improve black and white images. Generally, one or more of the toners described herein are in an amount of 0.01 wt% to 10 wt%, more preferably 0.1 wt%, based on the total dry weight of the layer containing the toner. It is preferably used in an amount of 10% to 10% by weight. The toner may be incorporated in one or more of the heat-developable image forming layers and in an adjacent layer such as a protective overcoat layer or undercoat layer.

  As the toner used in the present invention, mercaptotriazole represented by the following general formula I is preferable.

In the above general formula, R ₁ and R ₂ are each independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 7 carbon atoms (for example, methyl, ethyl, isopropyl, t-butyl, n-hexyl, Hydroxymethyl and benzyl), substituted or unsubstituted alkenyl groups having 2 to 5 carbon atoms in the hydrocarbon chain (for example, ethenyl, 1,2-propenyl, methallyl and 3-buten-1-yl), ring formation A substituted or unsubstituted cycloalkyl group having 5 to 7 carbon atoms (for example, cyclopentyl, cyclohexyl, and 2,3-dimethylcyclohexyl), of carbon, nitrogen, oxygen, or sulfur forming the aromatic or non-aromatic ring A substituted or unsubstituted aromatic or non-aromatic heterocyclic group having 5 to 6 atoms (for example, pyridyl, furanyl, thiazolyl, and thie Nyl), amino group or amide group (for example amino or acetamide), substituted or unsubstituted aryl group having 6 to 10 carbon atoms forming the aromatic ring (for example, phenyl, tolyl, naphthyl and 4-ethoxyphenyl) Represents.

R ₁ and R ₂ are substituted or unsubstituted Y ¹ — (CH ₂ ) _k — groups, wherein Y ¹ is a C 6-10 substitution as defined for R ₁ and R ₂ above. A substituted or unsubstituted aryl group or a substituted or unsubstituted aromatic or non-aromatic heterocyclic group defined for R ₁ , and k is 1 to 3; It may be.

Alternatively, by combining R ₁ and R ₂ , a substituted or unsubstituted saturated or unsaturated aromatic or non-aromatic system containing a carbon, nitrogen, oxygen or sulfur atom in the ring 5-7 membered nitrogen-containing heterocycles (for example, pyridyl, diazinyl, triazinyl, piperidine, morpholine, pyrrolidine, pyrazolidine and thiomorpholine).

Furthermore, R ₁ or R ₂ can represent a divalent linking group (for example, phenylene, methylene, or ethylene group) that connects two mercaptotriazole groups, and R ₂ can represent carboxy or a salt thereof.

  M is hydrogen or a monovalent cation (for example, alkali metal cation, ammonium ion or pyridinium ion). Preferably M is hydrogen.

  Typical compounds represented by the general formula I and useful as a toner in the practice of the present invention include the following compounds T-1 to T-59.

  Compounds T-1, T-2, T-3, T-11, T-12, T-16, T-37, T-41 and T-44 are preferred in the present invention, and compounds T-1, T-2 And T-3 are most preferred.

  The mercaptotriazole toner described herein can be readily prepared using well-known synthetic methods. For example, Compound T-1 can be prepared as described in US Pat. No. 4,628,059 (Finkelstein et al.). Additional preparations of various mercaptotriazoles are described in US Pat. Nos. 3,769,411 (Greenfield et al.), 4,183,925 (Baxter et al.), 6,074,813. (Asanuma et al.), DE 160604 (Korosi), and Chem Abstr. 1968, 69, 52114j. Several mercaptotriazole compounds are commercially available.

  Two or more mercaptotriazole toners of the mercaptotriazole represented by the general formula I can be used in the practice of the present invention, and a plurality of toners can be disposed in the same or different layers of the photothermographic material.

  Additional conventional toners can also be included with one or more mercaptotriazoles described above. Such compounds are well known materials in the photothermographic art.

  Phthalazine and phthalazine derivatives (such as those described in US Pat. No. 6,146,822 (noted above)) are particularly useful as additional conventional toners. These conventional toners can be used as a mixture with the mercaptotriazole represented by the general formula I described herein. Phthalazine and phthalazine derivatives can be used in any layer of the photothermographic material on either side of the support.

(binder)
The photocatalyst (e.g., photosensitive silver halide), non-photosensitive source of reducible silver ions, reducing agent composition, toner, and other additives used in the present invention can be combined with one or more hydrophilic binders. Added and coated. Accordingly, an aqueous formulation is used to prepare the photothermographic material of the present invention. Mixtures of different types of hydrophilic binders can be used.

  Examples of useful hydrophilic binders include proteins and protein derivatives, gelatin and gelatin derivatives (hardened or unhardened gelatin including alkali-treated and acid-treated gelatin, and deionized gelatin), cellulosic materials such as hydroxymethylcellulose and Cellulose ester, acrylamide / methacrylamide polymer, acrylic / methacrylic polymer, polyvinyl pyrrolidone, polyvinyl alcohol, poly (vinyl lactam), sulfoalkyl acrylate or methacrylate polymer, hydrolyzed polyvinyl acetate, polyamide, polysaccharide (eg dextran and starch ether) , And other naturally occurring or synthetic vehicles well known for use in aqueous photographic emulsions [eg Research Disc Osure, Item 38957 (described above) Reference can be mentioned. For emulsions containing tabular grain silver halide, as described in US Pat. No. 5,620,840 (Maskasky) and US Pat. No. 5,667,955 (Maskasky). Cationic starch can also be used as a peptizer.

  Particularly useful hydrophilic binders are gelatin, gelatin derivatives, polyvinyl alcohol and cellulosic materials. Gelatin and gelatin derivatives are most preferred, and when a binder mixture is used, it comprises more than 75% by weight of the total binder.

  A small amount of hydrophobic binder may be present as long as more than 50% (of the total binder mass) consists of hydrophilic binder. Examples of typical hydrophobic binders include polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, cellulose acetate, cellulose acetate butyrate, polyolefin, polyester, polystyrene, polyacrylonitrile, polycarbonate, methacrylate copolymer, maleic anhydride ester copolymer, butadiene- Styrene copolymers, and other materials readily apparent to those skilled in the art. Copolymers (including terpolymers) are also included in the definition of polymers. Particularly preferred are polyvinyl acetals (eg polyvinyl butyral and polyvinyl formal) and vinyl copolymers (eg polyvinyl acetate and polyvinyl chloride). Particularly suitable binders are polyvinyl butyral resins available as BUTVAR® B79 (Solutia, Inc), PIOLOFORM® BS-18 or PIOLOFORM® BL-16 (Wacker Chemical Company). An aqueous dispersion (or latex) of a hydrophobic binder can also be used.

  The polymer binder is used in an amount sufficient to support the components dispersed in the binder. The effective range can be appropriately determined by those skilled in the art. Preferably, the binder is used at a level of 10% to 90% by weight, more preferably at a level of 20% to 70% by weight, based on the total dry weight of the layer containing the binder. The amount of the binder in the double-sided photothermographic material may be the same or different.

(Additive)
The photothermographic material of the present invention may contain the additives described below. These additives may be added to layers other than the image forming layer, such as an intermediate layer, a protective layer, a back layer, and an undercoat layer.

(A) Dispersion stabilizer Usually, a dispersion stabilizer is added at the time of preparation of a dispersion, and is additionally added at the time of preparation of a coating solution. An example of the dispersion stabilizer is a hydrophilic polymer, and preferred 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, more preferably 30% by mass or less, based on the solid content of the dispersion. The lower limit of this addition amount is not particularly limited, but is usually about 1% by mass.

(B) Surfactant for improving coatability The photothermographic material of the invention may contain a surfactant for improving coatability. The surfactant may be any of a nonionic surfactant, an anionic surfactant, a fluorine surfactant, 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 photothermographic material of the 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). As for the fluorine-containing surfactant, JP-A-49-10722, British Patent 1,330,356, US Pat. No. 4,335,201, and 4,347,308 are disclosed. British Patent 1,417,915, JP-A-55-149938, 58-196544, British Patent 1,439,402, and the like.

You may use the said fluorine-containing surfactant in mixture of 2 or more types. The amount of the fluorine-containing surfactant used is preferably 0.0001 to 1 g, more preferably 0.0002 to 0.25 g, and particularly preferably 0.0003 to 0.1 g per 1 m ² of the image recording material.

(D) Dye and Pigment A dye or pigment may be added to an arbitrary layer of the photothermographic material of the invention for the purpose of adjusting the color tone or preventing irradiation. 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, and styryl dyes. , Triphenylmethane dyes, indoaniline dyes, indophenol dyes, organic pigments including phthalocyanine, inorganic pigments, and the like. 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 pigment used may be selected according to the target absorption amount, but generally the optical absorption density at the exposure wavelength is 0.1 to 2.0, preferably 0.2 to 1.0. To be added. The dye and pigment may be added in any state, such as a solution, emulsion, solid fine particle dispersion, or mordanted in a polymer mordant. However, if the dye and pigment are water-soluble substances, they are 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 is 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 may be added to the image forming layer. 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 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. , Thiazoline ring, thiazole ring, benzothiazole ring, naphthothiazole ring, selenazole ring, benzoselenazole ring, naphthselenazole ring, oxazole ring, benzoxazole ring, naphthoxazole ring, imidazole ring, benzimidazole ring or pyridine 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 are 0 or 1 X represents an anion, and m represents 1 or 2.

The Z ¹ and Z ² nonmetallic atom groups may be the same or different from each other as long as they can complete the above-described benzothiazole ring. Examples of the benzothiazole ring include benzothiazole and 5-chlorobenzothiazole. , 5-methylbenzothiazole, 5-methoxybenzothiazole, 5-hydroxybenzothiazole, 5-hydroxy-6-methylbenzothiazole, 5,6-dimethylbenzothiazole, 5-ethoxy-6-methylbenzothiazole, 5-henyl Examples include benzothiazole, 5-carboxybenzothiazole, 5-ethoxycarbonylbenzothiazole, 5-dimethylaminobenzothiazole, and 5-acetylaminobenzothiazole. Examples of the benzoselenazole ring include benzoselenazole, 5-chlorobenzoselenazole, 5-methylbenzoselenazole, 5-methoxybenzoselenazole, 5-hydroxybenzoselenazole, 5,6-dimethylbenzoselenazole, Examples include 5,6-dimethoxybenzoselenazole, 5-ethoxy-6-methylbenzoselenazole, 5-hydroxy-6-methylbenzoselenazole, and 5-henylbenzoselenazole. Further examples of the naphthothiazole ring include β-naphthothiazole, β, β-naphthothiazole and the like can be mentioned, and examples of the naphthoselenazole ring include β-naphthoselenazole.

  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, 4-methylthiazole, and 4-phenyl. Examples include thiazole, 4,5-dimethylthiazole, 4-methyl-5-phenylthiazole and the like. Examples of the selenazole ring include selenazole, 4-methylselenazole, 4-phenylselenazole, 4,5-dimethylselenazole and the like. Examples of the oxazole ring include oxazole, 4-methyl oxazole, 5-methyl oxazole, 4,5-dimethyl oxazole, and 4-p-tolyl oxazole. Examples of the benzoxazole ring include benzoxazole. 5-fluorobenzoxazole, 5-chlorobenzoxazole, 5-bromobenzoxazole, 5-trifluoromethylbenzoxazole, 5-methylbenzoxazole, 5-methyl-6-phenylbenzoxazole, 5,6-dimethylbenzoxazole, Examples include 5-methoxybenzoxazole, 5,6-dimethoxybenzoxazole, 5-phenylbenzoxazole, 5-carboxybenzoxazole, 5-methoxycarbonylbenzoxazole, and 5-acetylbenzoxazole. Examples of the naphthoxazole ring include β-naphthoxazole and the like, and examples of the imidazole ring include 1-methylimidazole, 1-ethylimidazole, 1-phenylimidazole and the like. Examples of the imidazole ring include 1-methylbenzimidazole, 1-phenylbenzimidazole, 5-chloro-1-ethylbenzimidazole, 5-trichloromethyl-1-ethylbenzimidazole, and 5,6-dichloro-1-ethylbenzimidazole. 5,6-dichloro-1-phenylbenzimidazole, 5-methoxycarbonyl-1-ethylbenzimidazole, 5-N, N-dimethylcarbamoyl-1-methylbenzimidazole, 5-N, N-diethylsulfamoyl- Examples include 1-phenylbenzimidazole, 5-cyano-1-ethylbenzimidazole, 5-cyano-1-β-hydroxyethylbenzimidazole, and examples of the pyridine ring include pyridine and 5-methylpyridine.

Specific examples of R ¹¹ and R ¹² include alkyl groups such as methyl group, ethyl group and n-propyl group, β-hydroxyethyl group, β-carboxyethyl group, γ-carboxypropyl group, and γ-sulfopropyl. And substituted alkyl groups such as γ-sulfobutyl group, δ-sulfobutyl group and δ-sulfoethoxyethyl group.

  Specific examples of the anion represented by X include a halogen ion, a perchlorine ring ion, a thiocyanate ion, a benzenesulfonate ion, a p-toluenesulfonate ion, and a methylsulfate ion.

In the general formula [2], Z ³ is 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, thiazole ring, respectively. Represents a group of nonmetallic atoms necessary to form a benzothiazole ring, a selenazole ring, a benzoselenazole ring or a pyridine ring, and Z ⁴ represents a 2-thiohydratoin ring, a 2-thiooxazolidine-2,4′-dione ring or a rhodanine Represents a group of non-metallic atoms necessary to form a ring, R ¹⁴ represents an alkyl group having 1 to 4 carbon atoms, a carboxyalkyl group or a hydrogen atom, and R ¹⁵ represents an alkyl group or hydrogen atom having 1 to 4 carbon atoms. N3 represents 0 or 1.

Specifically, Z ³ is oxazole, 4-methyloxazole, 5-methyloxazole, 4,5-dimethyloxazole, 4-p-tolyloxazole, benzoxazole, 5-fluorobenzoxazole, 5-chlorobenzoxazole, 5- Bromobenzoxazole, 5-trifluoromethylbenzoxazole, 5-methylbenzoxazole, 5-methyl-6-phenylbenzoxazole, 5,6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5,6-dimethoxybenzoxazole, 5-phenylbenzoxazole, 5-carboxybenzoxazole, 5-methoxycarbonylbenzoxazole, 5-acetylbenzoxazole, selenazole, 4-methylselenazole, 4-phenylselena 4,4-dimethylselenazole, benzoselenazole, 5-chlorobenzoselenazole, 5-bromobenzoselenazole, 5-methylbenzoselenazole, 5-methoxybenzoselenazole, 5,6-dimethylbenzoselena Sol, 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-methoxycarbonylbenzothiazole, 5-hydro Xylbenzothiazole, 5-trifluoromethylbenzothiazole, 5-cyanobenzothiazole, 5,6-dimethylbenzothiazole, 5-acetylaminobenzothiazole, 6-methoxybenzothiazole, 5,6-dimethoxybenzothiazole, 5,6 -Dichlorobenzothiazole, naphtho [1,2-d] thiazole and the like.

  Next, specific examples of the compounds represented by the general formulas [1] and [2] used in the present invention will be shown. The compounds represented by the general formulas [1] and [2] that can be used in the present invention are these. It is not limited to.

The addition of these sensitizing dyes can be carried out by the method described in paragraph No. 0106 of JP-A No. 11-119374, but is not particularly limited to this method. The addition amount of the sensitizing dye in the present invention can be set to a desired amount in accordance with the sensitivity and fogging performance, but is preferably 10 ^{−6 to} 1 mol, more preferably 10 ⁻⁴ per mol of the photosensitive silver halide. -10 ^-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 compounds selected from heteroaromatic or aliphatic mercapto compounds, heteroaromatic disulfide compounds, stilbenes, hydrazines, and triazines. 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, and JP-A-10-111543. Compounds of SS-01 to SS-07, compounds of 31, 32, 37, 38, 41 to 45, 51 to 53 of JP-A-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 photothermographic material. The decrease in sensitivity during stock storage can be suppressed. Antifoggants, stabilizers and stabilizer precursors may be used alone or in combination, examples of which are described in U.S. Pat. Nos. 2,131,038 and 2,694,716. Thiazonium salts described in US Pat. No. 2,886,437 and azaindene described in US Pat. No. 2,444,605; mercury described in US Pat. No. 2,728,663 Salt; urazole described in US Pat. No. 3,287,135; sulfocatechol described in US Pat. No. 3,235,652; oxime described in British Patent 623,448, nitroso And nitroindazole; a polyvalent metal salt described in US Pat. No. 2,839,405; a thiuonium salt 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 4,442,202 Halogen-substituted organic compounds described in the specification: U.S. Pat. Nos. 4,128,557, 4,137,079, 4,138,365 and 4,459,350 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 may be used. The mercapto compound is preferably represented by Ar-SM or Ar-SS-Ar. 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-mercaptopyrimidi 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 acid may be added to any layer of the photothermographic material of the present invention, but it is preferably added to the layer provided on the image forming layer side of the support, and is 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 9- And the compounds described in JP-A Nos. 329864 and 9-291737.

  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. Moreover, you may add benzoic acid as a solution mixed with additives, such as a sensitizing dye, a reducing agent, and a color toning agent. 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 slipping agent include U.S. Pat. No. 3,042,522, British Patent 955,061, U.S. Pat. Nos. 3,080,317 and 4,004,927. No. 4,047,958, 3,489,567, British Patent 1,143,118, etc .; US Pat. No. 2,454,043 No. 2,732,305, No. 2,976,148, No. 3,206,311, German Patent No. 1,284,295, No. 1, Higher fatty acid-based slip agents, alcohol-based slip agents and acid amide-based slip agents described in US Pat. No. 284,294; British Patent 1,263,722; US Pat. No. 3,933,516 Metal soap as described in US Pat. 88,765, 3,121,060, British Patent 1,198,387, and the like; ester-based and ether-based slip agents described in US Pat. No. 3,502,473; And taurine-based slip agents described in US Pat. No. 3,042,222. 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.

(Support)
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 as the base thickness excluding the 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 pigment 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 and the like, and SBR, polyester, gelatin and the like may be added as a binder as necessary. Furthermore, the undercoat layer may contain the above-mentioned 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, it is preferable that the transport tension of the support during processing is relatively low. Specifically, it is preferably 7 kg / cm ² or less, and 4.2 kg / cm 2 or less. Is more preferable. 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.

(Back layer)
The back layer is formed by adding the dye represented by the general formula (1) or (2), a base generator, and, if necessary, the following additives to the polymer binder. Further, the back layer may contain the fluorine-containing surfactant.

(1) Dye In the present invention, the back layer contains the dye represented by the general formula (1) or (2) according to the present invention. In the general formulas (1) and (2), R ¹ is a hydrogen atom, an aliphatic group, an aromatic group, —NR ²¹ R ²⁶ , —OR ²¹ , or —SR ²¹ , and R ²¹ and R ²⁶ are each independently Are a hydrogen atom, an aliphatic group, or an aromatic group, or R ²¹ and R ²⁶ are combined to form a nitrogen-containing heterocyclic ring; R ² is a hydrogen atom, an aliphatic group, or an aromatic group Each of L ¹ and L ² is independently a substituted or unsubstituted methine group, and the substituents of the methine group may be bonded to each other to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring; ¹ is an atomic group necessary for completing a 5-membered or 6-membered nitrogen-containing heterocyclic ring, and the nitrogen-containing heterocyclic ring may be condensed with an aromatic ring, and the nitrogen-containing heterocyclic ring and its condensed ring May have a substituent; A represents an acidic nucleus, B represents an aromatic group, an unsaturated heterocyclic group, or the above general formula Represents (3). n and m each represent 1 or 2.

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

R ¹ is preferably —NR ²¹ R ²⁶ , —OR ²¹ , or —SR ²¹ . R ²¹ is preferably an aliphatic group or an aromatic group, and more preferably an alkyl group, a substituted alkyl group, an aralkyl group, a substituted aralkyl group, an aryl group or a substituted aryl group. R ²⁶ is preferably a hydrogen atom or an aliphatic group, more preferably a hydrogen atom, an alkyl group or a substituted alkyl group. The nitrogen-containing heterocyclic ring formed by combining R ²¹ and R ²⁶ is preferably a 5-membered ring or a 6-membered ring. The nitrogen-containing heterocycle may have a hetero atom other than nitrogen (eg, oxygen atom, sulfur atom).

  In the present specification, 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 preferable, and an alkyl group, a substituted alkyl group, an aralkyl group or a substituted aralkyl group is more preferable. 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 alkenyl 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 and Reelsulfonylamino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, alkyl and arylsulfinyl group, alkyl and arylsulfonyl group, alkoxycarbonyl group, imide group, phosphino group, phosphinyl group, phosphinyl group An oxy group, a phosphinylamino group, and a silyl group are included. 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 present specification, 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 is a hydrogen atom, an aliphatic group, or an aromatic group. 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), L ¹ , L ² , and L ³ are each independently methine that may be substituted. Examples of the methine substituent include a halogen atom, an aliphatic group, and an aromatic group. The definition of the aliphatic group and the aromatic group is as described above. A methine substituent 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. It is particularly preferred that the methine is unsubstituted or forms a cyclopentene ring or a cyclohexene ring. In the formula (1), n represents 1 or 2, but is preferably 1. When n is 2, the methine group is repeated but need not be identical. In the formula (2), m represents 1 or 2, but is preferably 1. When m is 2, the methine group is repeated but 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 include an oxazole ring, a thiazole ring, a selenazole ring, a pyrrole ring, a pyrroline ring, an imidazole ring, and a pyridine ring. A 5-membered ring is preferred over a 6-membered ring. The nitrogen-containing heterocycle may be condensed with an aromatic ring (benzene ring or naphthalene ring). The nitrogen-containing heterocycle and its condensed ring may have a substituent. Examples of the substituent include the above-mentioned aromatic substituents, preferably halogen atoms (fluorine atoms, chlorine atoms, bromine atoms), hydroxyl, nitro, carboxyl, sulfo, alkoxy, aryl groups, And an alkyl group. Carboxyl and sulfo may be in a salt state. The cation that forms a salt with carboxyl and sulfo 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 the following general formula (3). The definition of the aromatic group is as described above. The aromatic group represented by B is preferably a substituted or unsubstituted phenyl group, and the substituent is a halogen atom, amino group, acylamino group, alkoxy group, aryloxy group, alkyl group, alkylthio group, aryl group. And an amino group, an acylamino group, an alkoxy group, and an alkyl group are particularly preferable at the 4-position. The unsaturated heterocycle represented by B is preferably a 5- 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 . The same thing as said Z1 can be mentioned as an example of a nitrogen-containing heterocyclic ring. 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), A represents an acidic nucleus. As the acidic nucleus, a cyclic ketomethylene compound or a compound having a methylene group sandwiched between electron-withdrawing groups is preferable. Examples of cyclic ketomethylene compounds include 2-pyrazolin-5-one, rhodanine, hydantoin, thiohydantoin, 2,4-oxazolidinedione, isoxazolone, barbituric acid, indandione, dioxopyrazolopyridine, melodrum acid, Examples thereof include hydroxypyridine, pyrazolidinedione, 2,5-dihydrofuran-2-one, and pyrrolin-2-one. These may have a substituent.

A compound having a methylene group sandwiched between electron-withdrawing groups can be represented as Z ¹ CH ₂ Z ² , where Z ¹ and Z ² are —CN, —SO ₂ R ¹ , —COR ¹ and —COOR, respectively. ² , —CONHR ² , —SO ₂ NHR ² , —C {═C (CN) ₂ } R ¹ , —C {═C (CN) ₂ } NHR ¹ , where R ¹ represents an alkyl group, an aryl group, a complex It represents a cyclic group, R ² represents a group wherein a hydrogen atom, represented by R ^1, and R ^1, R ² 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 the anion include halogen ion (Cl, Br, I), p-toluenesulfonic acid ion, ethyl sulfate ion, 1,5-disulfonaphthalene dianion, PF ₆ , BF ₄ , and ClO ₄ . Specific examples of the dyes represented by the general formulas (1) and (2) are shown below.

(2) Base Precursor The above dye or salt thereof can be decolored by allowing a base to act under heating conditions. According to the study by the present inventors, in the above dye, the active methylene group in the dye is deprotonated by the action of a base, and the nucleophilic species generated thereby nucleophilically attacks the methylene chain in the molecule, thereby causing an intramolecular ring-closed product. It was found that the color disappears by forming. Accordingly, any base that can be used for this reaction can 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 that the color erased by this color erasing method is restored.

  The heating temperature in 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 dye, they react with each other during storage and lose their halation-preventing function, so it is desirable to use the base as a thermal decomposition precursor. 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. Examples of the physical separation of the base include the use of microcapsules, encapsulating a hot-melt material in fine particles, or addition 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. The heat-responsive capsule is described in Hiroyuki Moriga, Introductory / Special Paper Chemistry (Showa 50), and JP-A-1-150575. A base or a dye may be added to the fine particles of a hot-melt material such as wax. The melting point of the hot-melt material 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. A typical precursor that generates a base by heating is a pyrolytic (decarboxylation) base precursor comprising a salt of a carboxylic acid and a base. When the decarboxylated base precursor is heated, the carboxyl group of the carboxylic acid undergoes a decarboxylation reaction, and the organic base is released. 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 (aryl or saturated heterocyclic group) that promotes decarboxylation 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 component of the decarboxylation type 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 diacid base, triacid base or tetraacid base precursor of the amidine derivative is described in JP-B-7-59545. A precursor of a dioxygen base, a triacid base or a tetraacid base of a guanidine derivative is described in JP-B-8-10321. The diacid base of an amidine derivative or guanidine derivative comprises (A) a diamidine moiety or guanidine moiety, (B) a substituent of the amidine moiety or guanidine moiety, and (C) a divalent group that combines two amidine moieties 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 (C) is preferably an alkylene group or a phenylene group. Specific examples of the diacid base precursor of the amidine derivative or guanidine derivative are shown below, but the base precursor that can be used in the present invention is not limited thereto.

  The dye can be contained in the photothermographic material in the form of a molecule, emulsion, or solid fine particles. In the case of molecular dispersion, a dye solution is added to the coating solution. When dispersed in the form of solid fine particles, a dispersion of solid fine particles of dye is prepared and then added to the coating solution.

  The amount of dye added is generally such that the optical density (absorbance) exceeds 0.1 when measured at the target wavelength. In practice, the optical density is preferably from 0.3 to 3.0, more preferably from 0.3 to 2.0, and even more preferably from 0.3 to 1.5. .

  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 kinds of compounds may be used in combination for the dye and the base precursor. In particular, in order to adjust the melting point to a desired region, it is preferable to mix those having different melting points.

(3) Back layer binder The back layer may contain a binder, and the binder used in 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 DOO, cellulose esters, polyamides, and the like. The back layer may contain a polymer latex used for the image forming layer, and the glass transition temperature of the polymer latex 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.

(4) Back layer matting agent It is preferable to add a matting agent to the back layer in order to lower the Beck second. 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.

(Other)
The photothermographic 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. Various auxiliary layers such as a back layer may be provided on the side of the support opposite to the image forming layer.

(1) Intermediate layer In the photothermographic material of the invention, it is preferable to provide an intermediate layer in order to solve the problem in the case where a protective layer is directly provided on the image forming layer. Intermediate layer to avoid coating failures that disturb the interface due to a large pH difference between the protective layer and the image forming layer, or to include some of the additives that interact adversely when added to the image forming layer Can be preferably formed. Examples of agents that can be added include additives such as reducing agents, halogen precursors, silver carriers, dyes, pigments, development accelerators, development inhibitors, image stabilizers, dispersion stabilizers, crosslinking agents, plasticizers, and benzoic acids. Can be mentioned. As the binder for the intermediate layer, gelatin, polyvinyl alcohol, other synthetic polymers and the like can be used in addition to the polymer soluble in the organic solvent used in the image forming layer and the aqueous polymer latex. The thickness of the intermediate layer is preferably 0.01 to 30 μm, more preferably 0.05 to 10 μm.

(2) Protective layer The photothermographic material of the 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, an organic solvent-soluble polymer or an aqueous polymer latex used in the image forming layer can be used. In the case of a polymer latex, 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 addition amount of the binder is preferably the area of the protective layer is 0.2 to 10 g / m ^2, more preferably 1 to 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 when the photothermographic material is overlaid. Examples of matting agents include U.S. Pat. Nos. 1,939,213, 2,701,245, 2,322,037, 3,262,782, 3,539,344, 3,767,448, etc., 1,260,772, 1,192,241, 3, Examples thereof include inorganic matting agents described in Nos. 257,206, 3,370,951, 3,523,022, and 3,769,020. 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, calcium carbonate, desensitized silver chloride and silver bromide in a known manner, glass, inorganic compounds such as diatomaceous earth can be preferably used 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 one or both of the protective layer and the back layer, but at least the fluorine-containing surfactant 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, it is composed of a protective lower layer for protecting images mainly composed of organic polymers, and a protective upper layer for preventing adhesion including matting agent, slip agent, fluorine-containing surfactant, etc. and improving surface slipperiness. You can do it.

(3) Undercoat layer The photothermographic material of the invention may have an undercoat layer described in US Pat. No. 5,051,335.

(4) Coating The photothermographic material of the present invention may be coated by a coating operation such as dip coating, air knife coating, flow coating, extrusion coating using a hopper described in US Pat. No. 2,681,294. Good. Two or more layers can be coated simultaneously by the methods described in US Pat. No. 2,761,791 and British Patent 837,095.

(Heat developed image forming method)
In order to form an image using the photothermographic material of the present invention, it is preferable to carry out heat development after exposure with light having a wavelength of 500 nm or less, particularly 360 to 500 nm. Preferably, the photothermographic material of the present invention is exposed by a scanning laser exposure apparatus and thermally developed 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 photothermographic material of the present invention is used as a mask for producing a printing plate with a PS plate, the photothermographic material after heat development is information for setting exposure conditions for the PS plate in a plate making machine, In general, information for setting plate-making conditions such as conveyance conditions for mask originals and PS plates 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, the plate making machine S-FNRIII manufactured by Fuji Photo Film Co., Ltd. uses a light source having a wavelength of 670 nm as a detector and a barcode reader for detecting a registration mark. A light source of 670 nm is used as a barcode reader of the plate making machine APML series manufactured by Shimizu Manufacturing Co., Ltd. That is, when the Dmin (minimum density) near 670 nm is high, information on the film cannot be accurately detected, and work errors such as poor conveyance and poor exposure occur. Therefore, in order to read information with a light source of 670 nm, Dmin near 670 nm needs to be low, and the absorbance at 660 to 680 nm after heat development is required to be 0.3 or less. 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.

  In the present invention, as an exposure apparatus used for imagewise exposure, an exposure apparatus using a laser diode (LD) or a light emitting diode (LED) as a light source is preferably used. In particular, LD is more preferable in terms of high output and high resolution. Any of these light sources may be used as long as they can generate light having an electromagnetic spectrum in a target wavelength range. For example, in the case of LD, a dye laser, a gas laser, a solid laser, a semiconductor laser, or the like can be used. Of particular interest are modules or blue semiconductor lasers in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated. High illuminance is generally performed with a short exposure time of 10-7 seconds or less.

  The exposure in the present invention 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 overlap can be expressed quantitatively by FWHM / sub-scanning pitch width (overlap coefficient), for example, when the beam diameter is expressed by the half width (FWHM) of the beam intensity. In the present invention, this overlap coefficient is preferably 0.2 or more.

  The scanning method of the light source of the exposure apparatus used in the present invention is not particularly limited, and a cylindrical outer surface scanning method, a cylindrical inner surface scanning method, a planar scanning method, or the like can be used. The channel of the light source may be a single channel or a multi-channel, but a multi-channel equipped with two or more laser heads is preferable in that a high output is obtained and a writing time is shortened. 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.

  The photothermographic material of the present invention has a low haze upon exposure and tends to generate interference fringes. This interference fringe generation prevention technique is disclosed in Japanese Laid-Open Patent Application No. 5-113548 and the like, in which a laser beam is incident obliquely on the photosensitive material, and in International Publication WO95 / 31754. There are known methods using multimode lasers, and these techniques are preferably used.

  The heat development step of the image forming method used in the present invention may be any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. As a preferred embodiment of the heat developing machine to be used, as a type in which the photothermographic material is brought into contact with a heat source such as a heat roller or a heat drum, Japanese Patent Publication No. 5-56499, Japanese Patent Application Laid-Open No. 9-292695, Japanese Patent Application Laid-Open No. 9-297385. And a non-contact type heat developing machine described in International Publication No. WO 95/30934, Japanese Patent Application Laid-Open No. 7-13294, International Publication Nos. WO 97/28489, 97/28488, and 97/28487. There is a heat developing machine described in the Gazette. 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, and more preferably 5 to 90 seconds. The line speed is preferably 140 cm / min or more, more preferably 150 cm / min or more.

  As a method for preventing processing unevenness due to dimensional change of the photothermographic 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 of image development by heat development (so-called multistage heating method).

  When the photothermographic material of the present invention is subjected to heat development processing, it is exposed to a high temperature of 100 ° C. or higher, so that a part of the components contained in the material or a part of the decomposition component by heat development volatilizes. come. These volatile components can cause uneven development, corrode heat developing machine components, precipitate at low temperatures, cause deformation of the screen as foreign matter, and adhere to the screen and become dirty. It is known that there are bad effects. 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. International Publication Nos. WO95 / 30933, 97/21150, and Japanese National Publication No. 10-500496 include a first opening for introducing volatile components and a second opening for discharging volatile matter. Is used in a heating device that heats the filter cartridge in contact with the film. In addition, International Publication WO 96/12213 and Japanese National Publication No. 10-507403 disclose that a filter in which a heat-conducting condensation 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. WO 98/27458 describes that a component that increases fog that volatilizes from a film is removed from the film surface. These can also be preferably used in the present invention.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
1. Preparation of undercoated PET support 1 Plasma treatment 1 is performed on both surfaces of a 125 μm thick PET film that has been biaxially stretched and heat-set under the following conditions, and then the undercoating liquid a-1 is dried on one surface. After coating to a film thickness of 0.8 μm, drying is performed to form an undercoat layer A-1, and on the opposite side, an undercoat coating solution b-1 subjected to the following antistatic treatment is applied to a dry film thickness of 0.8 μm. After being coated so as to become an undercoat layer B-1 as a conductive layer. Next, plasma treatment 2 was performed on the surface of each undercoat layer under the following conditions.

<< Plasma treatment conditions >>
Using a batch type atmospheric pressure plasma processing apparatus (EC-I-H-340, manufactured by EC Chemical Co., Ltd.), the high frequency output is 4.5 kW, the frequency is 5 kHz, the processing time is 5 seconds, and the gas conditions are argon, Plasma treatment 1 and plasma treatment 2 were performed at a volume ratio of nitrogen and hydrogen of 90%, 5%, and 5%, respectively.

<Undercoat coating liquid a-1>
Butyl acrylate (30% by mass)
t-Butyl acrylate (20% by mass)
Styrene (25% by mass)
2-Hydroxyethyl acrylate (25% by mass)
270 g of copolymer latex liquid (solid content 30%)
Hexamethylene-1,6-bis (ethylene urea) 0.8g
Polystyrene fine particles (average particle size 3 μm) 0.05 g
Colloidal silica (average particle size 90μm) 0.1g
Finish to 1 liter with water <Undercoat coating solution b-1>
Tin oxide (average particle size 36nm doped with 0.1% indium)
Amount to be 0.26 g / m ² Butyl acrylate (30% by mass)
Styrene (20% by mass)
Glycidyl acrylate (40% by mass)
270 g of copolymer latex liquid (solid content 30%)
Hexamethylene-1,6-bis (ethylene urea) 0.8g
Finish to 1 liter with water <Heat treatment of support>
In the undercoating drying step of the obtained undercoated support, the support was heated at 140 ° C. and then gradually cooled. In that case, it conveyed with the tension | tensile_strength of 1 * 10 < ⁵ > Pa.
2. Formation of back layer and back protective layer (Preparation of solid fine particle dispersion (a) of base precursor)
64 g of the base precursor compound (exemplary compound BT-41 of the base precursor), 28 g of diphenylsulfone and 10 g of a surfactant (Demol N, manufactured by Kao Corporation) were mixed with 220 ml of distilled water, and the mixture was mixed with a sand mill (IMEX ( Co., Ltd., 1/4 Gallon Sand Grinder Mill) was used to disperse the beads to obtain a solid fine particle dispersion (a) of a base precursor compound having an average particle size of 0.2 μm.

(Preparation of anti-halation dye solid fine particle dispersion (b))
19.6 g of a basic decoloring type dye (exemplary compound (1) of the dye represented by the general formula (1) or (2) of the present invention) and 5.8 g of sodium p-dodecylbenzenesulfonate were added to 305 ml of distilled water. The mixture was dispersed with beads using a sand mill (Aimex Co., Ltd., 1/4 Gallon sand grinder mill) to obtain an antihalation dye solid fine particle dispersion (b) having an average particle size of 0.2 μm. .

(Preparation of back layer coating solution)
Gelatin 17g, polyacrylamide 9.6g, solid fine particle dispersion (a) of the above-mentioned base precursor 70g, solid fine particle dispersion (b) of the above antihalation dye 56g, monodisperse polymethyl methacrylate particles ( 1.5 g of average particle size 8 μm), 0.03 g of benzoisothiazolinone as a preservative, 2.2 g of sodium polyethylene sulfonate, and 844 ml of water were mixed.

(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, fluorosurfactant (F-3) 64 mg, fluorosurfactant (F-4) 32 mg, acrylic acid / ethyl acrylate Copolymer (copolymerization mass ratio 5/95) .8G, Aerosol OT (manufactured by American Cyanamid Co.) 0.6 g, was 1.8g liquid paraffin emulsion as liquid paraffin, water and mixed 950 ml.
(Application of back layer and back protective layer)
On the back surface side of the undercoat support, the back layer coating solution is coated with a solid fine particle dye in a solid content of 0.04 g / m ^2, and the back protective layer coating solution is coated with a gelatin coating amount of 1.7 g / m ^2. A multilayer was simultaneously applied so as to be m ² and dried to produce a back layer.

(Preparation of silver halide emulsion A (comparative))
In 900 ml of pure water, 7.5 g of gelatin and 10 mg of potassium bromide were dissolved, adjusted to a temperature of 35 ° C. and a pH of 3.0, and then brominated at a molar ratio of (96/4) with 370 ml of an aqueous solution containing 74 g of silver nitrate. An aqueous solution containing 5 × 10 ⁻⁶ mol / liter of potassium, potassium iodide and iridium chloride was added over 10 minutes by the controlled double jet method while maintaining pAg 7.7. Thereafter, 0.3 g of 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene was added, the pH was adjusted to 5 with NaOH, the average particle size was 0.06 μm, and the variation coefficient of the projected diameter area was 8%. , {100} face ratio 86% silver cubic silver iodobromide grains were obtained. This emulsion was coagulated and precipitated using a gelatin flocculant, desalted and then 0.1 g phenoxyethanol was added to adjust the pH to 5.9 and pAg 7.5. This is designated as silver halide emulsion A ′.

(Preparation of silver halide emulsion B)
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. This is designated as silver halide emulsion B '.

(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 silver iodide grains a (silver iodide dispersion) having a pAg of 8.0.

Each of the two silver halide emulsions A ′ and B ′ was maintained at 47 ° C. with stirring, and 5 ml of a 0.34% by weight methanol solution of 1,2-benzisothiazolin-3-one was added for 20 minutes. Later, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol with respect to 1 mol of silver, and further 5 minutes later, sodium thiosulfate was added to 6.2 × 10 ⁻⁵ mol per mol of silver and aged for 91 minutes. . Thereafter, 1 × 10 ⁻⁵ mol of sensitizing dye A and 1.3 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ′, N′-diethylmelamine were added, and after 4 minutes, 5-methyl 2-mercaptoben ヅ imidazole in methanol solution with 4.8 × 10 ⁻³ mol per mol of silver and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole with 1 mol of silver in methanol solution 5.4 × 10 ⁻³ mol was added to prepare silver halide emulsions A and B, respectively.

<< Preparation of benzotriazole silver dispersion A >>
A reactor equipped with a stirrer was charged with 85 g of lime-processed gelatin, 25 g of phthalate-processed gelatin, and 2 liters of deionized water (solution A). A solution (Solution B) containing 185 g of benzotriazole, 1405 ml of deionized water, and 680 g of 2.5 molar sodium hydroxide was prepared. The reactor solution was adjusted to pAg 7.25 and pH 8.0 by adding solution B and 2.5M sodium hydroxide solution as needed and maintained at a temperature of 36 ° C. A solution containing 228.5 g of silver nitrate and 1222 ml of deionized water (Solution C) is added to the reactor at an accelerated flow rate (t is time) with a flow rate = 16 (1 + 0.002 t ² ) ml / min, The pAg was maintained at 7.25 by adding solution B simultaneously.

  When solution C was used up, the process was terminated, at which point a 40 ° C. solution (solution D) consisting of 80 g of phthalated gelatin and 700 ml of deionized water was added to the reaction vessel. The resulting solution was stirred in the reaction vessel and the silver salt emulsion was coagulated by adjusting its pH to 2.5 with 2 molar sulfuric acid. The coagulum was washed twice with 5 liters of deionized water and redispersed by adjusting the pH to 6.0 and 2.5 pAg to 7.0 with 2.5 M sodium hydroxide solution and solution B. The resulting silver salt dispersion contained fine particles of silver benzotriazole salt. This is designated as benzotriazole silver dispersion A.

<< Preparation of silver carboxylate dispersion B >>
40 g of behenic acid, 7.3 g of stearic acid, and 500 ml of distilled water were mixed at 90 ° C. for 15 minutes, 187 ml of 1N sodium hydroxide aqueous solution was added over 15 minutes with vigorous stirring, and 61 ml of 1M nitric acid aqueous solution was added. Cooled to ° C. Next, 124 ml of 1M silver acid aqueous solution was added and stirred as it was for 30 minutes. Thereafter, the solid content was filtered by suction filtration, and washed with deionized water and drained until the electric conductivity of the filtrate reached 30 μS / cm. The solid content thus obtained was handled as a wet cake without being dried, and 12 g of polyvinyl alcohol and 150 ml of water were added to the wet cake corresponding to 34.8 g of the dry solid content and mixed well to obtain a slurry. Prepare 840 g of zirconia beads having an average diameter of 0.5 mm, put them in a vessel together with the slurry, and disperse them for 5 hours with a disperser (1/4 G-sand grinder mill: manufactured by IMEX Co., Ltd.). An organic acid silver crystallite dispersion of .5 μm was obtained. This is designated as silver carboxylate dispersion B.

[Preparation of photothermographic material]
Photosensitive layers A to D are respectively coated on the undercoat layer A-1 on the side opposite to the support and the side on which the back protective layer is applied so as to be a photosensitive layer having the following composition. Then, photothermographic material samples 1 to 4 were prepared.

(Photosensitive layer)
Photosensitive layer A
Silver halide emulsion A 0.4 g / m ²
Benzotriazole silver dispersion A 1.8 g / m ²
Sodium benzotriazole 0.14 g / m ²
3-Methylbenzothiazolium iodide 3-0.07 g / m ²
Succinimide 0.27 g / m ²
1,3-dimethylurea 0.24 g / m ²
Toner compound 0.08 g / m ²
Ascorbic acid 1.1 g / m ²
Lime-processed gelatin 3g / m ²
Photosensitive layer B
Silver halide emulsion B 0.4 g / m ²
Benzotriazole silver dispersion A 1.8 g / m ²
Sodium benzotriazole 0.14 g / m ²
3-Methylbenzothiazolium iodide 3-0.07 g / m ²
Succinimide 0.27 g / m ²
1,3-dimethylurea 0.24 g / m ²
Toner compound 0.08 g / m ²
Ascorbic acid 1.1 g / m ²
Lime-processed gelatin 3g / m ²
Photosensitive layer C
Silver halide emulsion A 0.4 g / m ²
Carboxylic acid silver dispersion B 1.8 g / m ²
Sodium benzotriazole 0.14 g / m ²
3-Methylbenzothiazolium iodide 3-0.07 g / m ²
Succinimide 0.27 g / m ²
1,3-dimethylurea 0.24 g / m ²
Toner compound 0.08 g / m ²
Ascorbic acid 1.1 g / m ²
Lime-processed gelatin 3g / m ²
Photosensitive layer D
Silver halide emulsion B 0.4 g / m ²
Carboxylic acid silver dispersion B 1.8 g / m ²
Sodium benzotriazole 0.14 g / m ²
3-Methylbenzothiazolium iodide 3-0.07 g / m ²
Succinimide 0.27 g / m ²
1,3-dimethylurea 0.24 g / m ²
Toner compound 0.08 g / m ²
Ascorbic acid 1.1 g / m ²
Lime-processed gelatin 3g / m ²

[Evaluation methods]
<Evaluation of photographic performance>
(Exposure processing)
The photothermographic material is mirror rotated using a single channel cylindrical inner surface type laser exposure device equipped with a semiconductor laser with a beam diameter (FWHM of 1/2 of the beam intensity) of 12.56 μm, laser output of 50 mW, and output wavelength of 430 nm. Exposure was performed at several 60000 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 photothermographic material was 75 μJ / cm ² . Thermal development was performed at 121 ° C. for 20 seconds. Density measurement was performed with a Macbeth TD904 densitometer (visible density).

  Sensitivity is expressed as a logarithm of exposure amount giving a density of 1.5, and is expressed as a relative value (relative sensitivity) where S1.5 is taken and the sensitivity of sample 1 is 100 (reference). The higher the value, the higher the sensitivity.

  Gamma was obtained as the gamma value of the slope of a straight line connecting the point of fog + density 0.5 to the point of fog + density 1.5 of the characteristic curve (exposure amount (logarithmic value) and image density).

(Evaluation of development processing humidity dependency)
For the photothermographic material, a sample conditioned at 23 ° C. and 80% RH for 12 hours and a sample conditioned at 23 ° C. and 20% RH for 12 hours were prepared, and subjected to heat development processing by performing 50 μm line width exposure in the same environment. It was.

  The development processing humidity dependency was evaluated by measuring the difference in line width after each processing according to the following equation.

Line width difference (μm) = (Line width of a 23 ° C. 80% RH 12 hour humidity control sample) − (Line width of a 23 ° C. 20% RH 12 hour humidity control sample)
Further, the difference in fog (the density of the unexposed area) in each environment was also obtained and evaluated by the following formula.

Difference in fog (density of unexposed area) = (fogging of 23 ° C. and 80% RH 12 hour humidity control sample) − (fogging of 23 ° C. and 20% RH 12 hour humidity control sample)
The results are shown in Table 1.

  From Table 1, it can be seen that the photothermographic material sample of the present invention has high sensitivity and high gamma, excellent development processing humidity dependency, and excellent raw storage stability.

Example 2
In the same manner as in Example 1, except that a photosensitive layer was provided as shown in Table 2, and instead of ascorbic acid as shown in Table 2, the reducing agent represented by the general formula (A) according to the present invention, Alternatively, using 1,1′-bis (2-hydroxy-3-tert-butyl-5-methylphenyl) butane (amount used is 1.7 g / m ² ) and heat development as described in Table 2 Photosensitive material samples 5 to 10 were prepared.

  Although the reducing agent was used as a reducing agent dispersion, the reducing agent was dispersed as follows.

(Preparation of reducing agent dispersion)
7.2 kg of water was added to 10 kg of the reducing agent shown in Table 2 and 16 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 4 hours 30 minutes in a horizontal sand mill filled with zirconia beads having an average diameter of 0.5 mm (manufactured by Imex Co., Ltd., UVM-2), and then benzoisothiazolinone sodium salt 0.2 g and water were added to prepare a reducing agent 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.

(Evaluation of raw preservation)
The obtained photothermographic material sample was divided into 2 minutes, one was forcedly deteriorated (55 ° C., 20% RH for 3 days), and the other was allowed to stand at room temperature (23 ° C., 20% RH for 3 days). Each exposure development was performed, and fog (unexposed area density) and sensitivity (similar to Example 1) were measured, respectively, and a fog difference and a sensitivity difference were respectively obtained by the following equations.

Difference in fog = [forced deterioration (55 ° C., 20% RH for 3 days) sample fog] − [normal temperature standing (23 ° C., 20% RH for 3 days) sample fog]
Difference in sensitivity = [sensitivity of sample left at room temperature (23 ° C., 20% RH for 3 days)]-[sensitivity of sample for forced deterioration (55 ° C., 20% RH for 3 days)]
The results are shown in Table 2.

  From Table 2, it can be seen that the photothermographic material sample of the present invention is excellent in development processing humidity dependency and excellent in preservability.

Claims (2)

An image forming layer containing a photosensitive silver halide having a silver iodide content of 40 mol% to 100 mol% on the support, a non-photosensitive organic silver salt other than the silver carboxylate, a reducing agent, and a hydrophilic binder. And having a back layer containing a dye represented by the following general formula (1) or (2) on the surface opposite to the image forming layer and exposing with light having a wavelength of 500 nm or less A photothermographic material, wherein an image having a gamma of 7 or more can be formed by heat development at a temperature of 100 ° C to 150 ° C.

(In the formula, R ¹ is a hydrogen atom, an aliphatic group, an aromatic group, —NR ²¹ R ²⁶ , —OR ²¹ , or —SR ²¹ , and R ²¹ and R ²⁶ are each independently a hydrogen atom or an aliphatic group. Or R ²¹ and R ²⁶ are combined to form a nitrogen-containing heterocyclic ring; R ² is a hydrogen atom, an aliphatic group or an aromatic group; and L ¹ and L ² are Each independently a substituted or unsubstituted methine group, and the substituents of the methine group may be bonded to each other to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring; Z ¹ is a 5-membered or 6-membered group Is an atomic group necessary for completing the nitrogen-containing heterocycle, and the nitrogen-containing heterocycle may be condensed with an aromatic ring, and the nitrogen-containing heterocycle and the condensed ring have a substituent. A represents an acidic nucleus, and B represents an aromatic group, an unsaturated heterocyclic group, or the following general formula (3). , M represents 1 or 2, respectively.

In the formula, L ³ is a substituted or unsubstituted methine group, and may combine with L ² to form an unsaturated aliphatic ring or an unsaturated heterocyclic ring. R ³ represents an aliphatic group or an aromatic group. Z ² is an atomic group necessary to complete a 5-membered or 6-membered nitrogen-containing heterocyclic ring, and the nitrogen-containing heterocyclic ring may be condensed with an aromatic ring, and the nitrogen-containing heterocyclic ring and its condensed The ring may have a substituent. ) 2. The photothermographic material according to claim 1, wherein the reducing agent is a reducing agent represented by the following general formula (A).

(In the formula, R ^{1 to} R ⁴ each independently represent a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group. R ⁵ represents a hydrogen atom or an aliphatic group. X ¹ , X ² Each independently represents a hydrogen atom or a group that can be substituted on the benzene ring, provided that R ¹ and R ² are not simultaneously hydrogen atoms, and R ³ and R ⁴ are not simultaneously hydrogen atoms. .)