JP2008180975A - Heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic solvent coating type heat developable photosensitive material excellent in raw preservation stability and image preservation stability. <P>SOLUTION: The heat developable photosensitive material has an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for heat development and a binder on at least one surface of a support, wherein ≥50 mass% of the binder is a modified polyvinyl acetal resin containing 1-20 mol% of α-olefin units in a main chain, and the heat developable photosensitive material has an undercoat layer containing a polymer latex having a crosslinking group between the support and the image forming layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photothermographic material. In particular, the present invention relates to a photothermographic material having improved raw storage stability and image storage stability.

  In recent years, in the medical field, reduction of waste processing liquid has been strongly desired from the viewpoint of environmental protection and space saving. Therefore, the photosensitive heat for medical diagnosis and photographic technology that can be efficiently exposed by a laser image setter or a laser imager and can form a clear black image having high resolution and sharpness. There is a need for techniques relating to developed photographic materials. These photosensitive photothermographic materials can eliminate the use of solution processing chemicals and supply customers with a simpler heat development processing system that does not damage the environment.

  Although there is a similar requirement in the field of general image forming materials, medical images are required to have high image quality with excellent sharpness and graininess because they are required to be finely drawn, and are cooled from the viewpoint of ease of diagnosis. There is a feature that a black tone image is preferred. At present, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed as general image forming systems. However, there is no satisfactory output system for medical images.

  On the other hand, thermal imaging systems using organic silver salts are described in many documents. In particular, the photothermographic material generally contains a catalytically active amount of a photocatalyst (eg, silver halide), a reducing agent, a reducible silver salt (eg, an organic silver salt), and a color tone that controls the color tone of silver if necessary. And an image forming layer dispersed in a binder matrix. The photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, and is blackened by an oxidation-reduction reaction between silver halide or a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form a silver image. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure. Therefore, a black silver image is formed in the exposure area. Fuji Medical Dry Imager FM-DPL was released as a medical image forming system using a photothermographic material.

As a method for producing a thermal image photosensitive material using an organic silver salt, a method is known in which an organic solvent such as methyl ethyl ketone is applied as a solvent and dried.
Polyvinyl acetals such as polyvinyl butyral have been generally used as binders for image forming layers (see, for example, Non-Patent Document 1).

  In the image forming layer of the thermal image photosensitive material, photosensitive silver halide, reducing agent, non-photosensitive organic silver salt necessary for image formation, and a color toning agent for controlling the color tone of silver are dispersed in a binder in advance. Because of this, the total solid content ratio of these components with respect to the binder is high, the coating solution viscosity is high, and the fluidity is poor, so that the productivity of the coating process is poor. The viscosity can be lowered by increasing the coating solvent to lower the solid content, but this is not preferable because the amount of the solvent increases and the load of coating drying and solvent recovery increases.

  In order to improve the coating suitability, use of a modified polyvinyl acetal is disclosed (for example, see Patent Document 1). When polynyl acetal copolymerized with α-olefin is used as a binder, thixotropy is strengthened, fluidity when applying a coating solution is improved, and desirable properties that do not spontaneously flow when standing and drying after coating Is disclosed.

However, the binder of the image forming layer is not only a function as a matrix for forming a film, but also a protective function for stably storing each component necessary for image formation until the image formation, mainly on a latent image generated by exposure. Comprehensive functions such as providing a development reaction field, a protective function for physically storing an image after image formation, and a protective function for preventing chemical alteration such as discoloration and fading are required. These total performances cannot be achieved simply by improving the binder, but can be solved by integrating the improvements of many components of the photothermographic material.
D. H. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials), Nebelte, 8th Edition, St. Worth. ), Edited by A. Shepp, Chapter 9, page 279, published in 1989 JP 2006-17877 A

  Accordingly, an object of the present invention is to provide a photothermographic material which has an excellent coated surface shape and has improved raw storage stability and image storage stability.

The object of the present invention has been achieved by the following photothermographic materials.
<1> A photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for heat development, and a binder on at least one surface of a support. In addition, 50% by mass or more of the binder is a modified polyvinyl acetal resin containing 1 mol% to 20 mol% of an α-olefin unit in the main chain, and is crosslinkable between the support and the image forming layer. A photothermographic material comprising an undercoat layer containing a polymer latex having a group.
<2> The modified polyvinyl acetal resin has a residual acetyl group amount of 25 mol% or less, a residual hydroxyl group amount of 17 mol% or more and 35 mol% or less, and a weight average polymerization degree of 200 or more and 3000 or less. The photothermographic material according to claim 1.
<3> The photothermographic material according to <1> or <2>, wherein the modified polyvinyl acetal resin is a modified polyvinyl butyral resin.
<4> The photothermographic material according to any one of <1> to <3>, wherein the polymer latex is a polymer latex having at least two crosslinkable groups in a monomer unit.
<5> A second undercoat layer containing a water-based polyester having a crosslinkable group is provided between the undercoat layer containing the polymer latex having the crosslinkable group and the image forming layer. <1 The photothermographic material according to any one of> to <4>.
<6> The crosslinkable group of the polymer latex is at least one selected from an epoxy group, an active methylene group, an isocyanate group, and an oxazoline group. Any one of <1> to <5> The photothermographic material according to the description.
<7> The photothermographic material according to any one of <1> to <6>, wherein the α-olefin is ethylene.

  According to the present invention, a photothermographic material having an excellent coated surface shape and improved raw storage stability and image storage stability can be obtained.

The present invention is described in detail below.
The photothermographic material of the present invention comprises an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for heat development, and a binder on at least one surface of a support. A photothermographic material having 50% by mass or more of the binder is a modified polyvinyl acetal resin containing 1 mol% to 20 mol% of an α-olefin unit in the main chain, and the support and the image forming layer And an undercoat layer containing a polymer latex having a crosslinkable group.

The inventors of the present invention attempted to improve coatability by using a modified polyvinyl acetal resin containing 1 to 20 mol% of α-olefin units in the main chain as an image forming layer binder. However, the present inventors faced a problem that the raw storage stability of the photothermographic material deteriorates. Further, it has been found that the storage stability of an image after image formation is deteriorated. As a result of diligently searching for improvement means, it was unexpectedly found that it is effective to provide an undercoat layer containing a polymer latex having a crosslinkable group between the support and the image forming layer. It came to.
When the α-olefin unit is less than 1 mol%, the effect of improving the coating property is poor, and when it is 20 mol% or more, the storage stability is severely deteriorated, and even with the above-mentioned improving means, sufficient improvement cannot be expected.

Preferably, the modified polyvinyl acetal resin has a residual acetyl group amount of 25 mol% or less, a residual hydroxyl group amount of 17 mol% or more and 35 mol% or less, and a weight average polymerization degree of 200 or more and 3000 or less.
Preferably, the modified polyvinyl acetal resin is a modified polyvinyl butyral resin.
Preferably, the polymer latex is a polymer latex having at least two crosslinkable groups in the polymer unit.
Preferably, a second undercoat layer containing an aqueous polyester having a crosslinkable group is provided between the undercoat layer containing the polymer latex having the crosslinkable group and the image forming layer.
Preferably, the crosslinkable group of the modified polymer latex and the modified aqueous polyester is at least one selected from an epoxy group, an active methylene group, an isocyanate group, and an oxazoline group.
Preferably, the α-olefin is ethylene.

  In the photothermographic material of the invention, 50% by mass or more of the binder of the image forming layer is the modified polyvinyl acetal resin of the invention. If it is less than 50% by mass, sufficient thixotropy cannot be obtained and coatability is lowered. A more preferred lower limit is 75% by mass.

  A known binder can be used without limitation for less than 50% by mass of the binder of the image forming layer. As the binder used as less than 50% by mass, any polymer may be used, and suitable binders are transparent or translucent and generally colorless, and natural resins, polymers and copolymers, synthetic resins, polymers and copolymers, and other films Forming media such as gelatins, rubbers, poly (vinyl alcohol) s, hydroxyethyl celluloses, cellulose acetates, cellulose acetate butyrates, poly (vinyl pyrrolidone) s, casein, starch, poly (acrylic acid) , Poly (methyl methacrylic acid) s, poly (vinyl chloride) s, poly (methacrylic acid) s, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, Poly (vinyl acetal) s (eg, poly (Vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethane) s, phenoxy resins, poly (vinylidene chloride) s, poly (epoxides), poly (carbonates), poly (vinyl acetate) ), Poly (olefin) s, cellulose esters, and poly (amides). Of these, gelatin and poly (vinyl acetal) other than the present invention are preferably used.

(Description of modified polyvinyl acetal resin)
The modified polyvinyl acetal resin (hereinafter also simply referred to as a modified polyvinyl acetal resin) used in the image forming layer of the heat-developable photosensitive material of the present invention contains an α-olefin unit in the main chain. Although it does not specifically limit as said alpha-olefin unit, For example, what originates in a C1-C20 linear or cyclic alkyl group is suitable. If it is in the said range, you may contain both the branch and the linear site | part, and the cyclic | annular site | part. When the number of carbon atoms of the α-olefin unit exceeds 20, the solvent solubility of the modified polyvinyl alcohol resin used as a raw material is lowered, so that the acetalization reaction does not proceed sufficiently and a modified polyvinyl acetal resin cannot be obtained. In some cases, the resulting modified polyvinyl acetal resin has low solvent solubility and cannot be used as a binder resin in an image forming layer of a heat-developable photosensitive material. More preferably, it is derived from a linear or cyclic alkyl group having 1 to 10 carbon atoms, and more preferably it is derived from a linear alkyl group having 2 to 6 carbon atoms. Specifically, for example, units derived from methylene, ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, hexylene, cyclohexylene, cyclohexylethylene, or cyclohexylpropylene are suitable.

  The lower limit of the content of the α-olefin unit in the main chain of the modified polyvinyl acetal resin in the present invention is 1 mol%, and the upper limit is 20 mol%. If it is less than 1 mol%, sufficient thixotropy cannot be exhibited, and a sufficient moisture permeability reduction effect cannot be obtained. If it exceeds 20 mol%, the solvent solubility of the modified polyvinyl alcohol resin used as a raw material is lowered, so that the acetalization reaction does not proceed sufficiently and a modified polyvinyl acetal resin cannot be obtained. The solvent solubility of the acetal resin is low and it cannot be used as a binder resin for the image forming layer of the photothermographic material. The upper limit is preferably 10 mol%, more preferably 4 mol% or more and 8 mol% or less.

In the modified polyvinyl acetal resin in the present invention, the preferable lower limit of the degree of acetalization is 40 mol%, and the preferable upper limit is 78 mol%, and more preferably 60 mol% or more and 75 mol% or less. If it is less than 40 mol%, it may be insoluble in an organic solvent and cannot be used as a binder resin for the image forming layer of the heat-developable photosensitive material. The toughness of the acetal resin may be impaired and the strength of the coating film may be reduced.
In this specification, as a method for calculating the degree of acetalization, since the acetal group of the modified polyvinyl acetal resin is acetalized from two hydroxyl groups, the two acetalized hydroxyl groups are counted. The method is employed to calculate the mole percent of the degree of acetalization.

  In the modified polyvinyl acetal resin of the present invention, the preferable lower limit of the residual hydroxyl amount is 17 mol%, and the preferable upper limit is 35 mol%. When it is less than 17 mol%, the dispersibility of the silver salt is poor when used as a binder resin, and the sensitivity may be lowered. If it exceeds 35 mol%, the image forming layer of the photothermographic material obtained is highly moisture permeable, fogging may occur, storage stability may deteriorate, and image density may decrease.

  In the modified polyvinyl acetal resin of the present invention, the preferable upper limit of the amount of residual acetyl groups is 25 mol%. If it exceeds 25 mol%, the resulting heat-developable photosensitive materials may be blocked or the resulting image may not be clear. A more preferable upper limit is 15 mol%, and further preferably 0.5 mol% or more and 5 mol% or less.

  In the modified polyvinyl acetal resin in the present invention, the preferable lower limit of the weight average polymerization degree is 200, and the preferable upper limit is 3000. Within this range, it is easy to balance the dispersibility of the silver salt, the strength of the coating film when coated, the coating property, and the like. A more preferred lower limit is 300, and a more preferred upper limit is 1000. In the present specification, unless otherwise specified, the degree of polymerization refers to the weight average degree of polymerization.

The modified polyvinyl acetal resin in the present invention is a solution prepared by dissolving in methyl ethyl ketone and adjusting the viscosity measured at 25 ° C. under a shear rate of 60 s ⁻¹ with an E-type viscometer to 4.0 Pa · s. The viscosity measured at 25 ° C. under a shear rate of 600 s ⁻¹ using an E-type viscometer is 3.0 Pa · s or less. By having such a thixotropic property, the modified polyvinyl acetal resin in the present invention is dissolved in a suitable organic solvent, and a silver salt of a fatty acid, an organic reducing agent, a photosensitive silver halide, etc. are dispersed in this solution. The layer composition dispersion has a sufficiently low viscosity during coating and is easy to apply. That is, since the viscosity at the time of high shear rate is low, even if it is applied at a high speed, it can be applied uniformly, so that the productivity of the photothermographic material can be remarkably improved. On the other hand, when it is left to stand after coating and dried, the viscosity is not high enough to cause spontaneous casting.
When the viscosity of the above solution measured at 25 ° C. under a shear rate of 600 s ⁻¹ using an E-type viscometer exceeds 3.0 Pa · s, it is the same level as a normal polyvinyl acetal resin, and the productivity improvement effect I can not expect. Preferably it is 2.5 or less.

When the modified polyvinyl acetal resin of the present invention is formed into a film having a thickness of 20 μm, the moisture permeability measured by a cup method according to JIS Z 0208 is preferably 500 g / m ² · day or less, and is preferably 400 g / m. More preferably, it is ² · day or less. If it exceeds 500 g / m ² · day, more water penetrates into the image forming layer of the resulting heat-developable photosensitive material, fogging occurs, storage stability deteriorates, and the resulting image density decreases. Sometimes.

  The modified polyvinyl acetal resin of the present invention preferably has a remaining halide content of 100 ppm or less. If it exceeds 100 ppm, photosensitive silver halide is produced, and the storage stability of the resulting heat-developable photosensitive material may be reduced, or fogging or the like may be caused. More preferably, it is 50 ppm or less.

The modified polyvinyl acetal resin in the present invention can be produced by acetalizing a modified polyvinyl alcohol having a saponification degree of 75 mol% or more and containing 1 to 20 mol% of an α-olefin unit in the main chain.
The modified polyvinyl alcohol can be obtained by saponifying a copolymer obtained by copolymerizing a vinyl ester and an α-olefin. Examples of the vinyl ester used in this case include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like. Among these, vinyl acetate is preferable from an economical viewpoint. Moreover, when obtaining the modified polyvinyl acetal containing the component derived from the said ethylenically unsaturated monomer, an ethylenically unsaturated monomer is further copolymerized. In addition, a terminal-modified polyvinyl alcohol obtained by copolymerizing a vinyl ester monomer such as vinyl acetate and an α-olefin in the presence of a thiol compound such as thiol acetic acid or mercaptopropionic acid, and saponifying it. Can be used.

  The modified polyvinyl acetal resin in the present invention can be produced by acetalizing the modified polyvinyl alcohol. The method for acetalization is not particularly limited, and a conventionally known method can be used. For example, an aqueous solution, alcohol solution, water / alcohol mixed solution, dimethyl sulfoxide (DMSO) of the modified polyvinyl alcohol in the presence of an acid catalyst can be used. Examples include a method of adding various aldehydes to the solution. It can also be produced by adding an acid catalyst and an aldehyde to an alcohol solution of polyvinyl acetate.

The aldehyde used for the acetalization is not particularly limited. For example, any aldehyde that can be acetalized such as formaldehyde, acetaldehyde, butyraldehyde, propylaldehyde, and the like may be used. Of these, it is preferable to use butyraldehyde and acetaldehyde alone or to use butyraldehyde and acetaldehyde in combination.
Moreover, it is preferable that the ratio of the part acetalized by butyraldehyde in the acetalized part of the obtained modified polyvinyl acetal resin is 30% or more with respect to the total acetalized part. If it is less than 30%, the nucleation of the photosensitive silver salt may proceed excessively, or the dispersibility of the silver salt may be insufficient, resulting in insufficient resolution and sharpness of the image. More preferably, it is 50% or more.

The acid catalyst is not particularly limited, and either an organic acid or an inorganic acid can be used. Examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, and hydrochloric acid. Of these, non-halogen compounds are preferred. If a non-halogen acid catalyst is used, the residual halide amount can be easily adjusted to 100 ppm or less. Further, when a halogen acid catalyst is used, it is preferable to purify the obtained modified polyvinyl acetal resin by sufficiently washing it with water or a mixed solution of water / alcohol.
In order to stop the synthesis reaction, alkali neutralization is usually performed. Examples of the alkali used in this case include sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogen carbonate, Examples include potassium carbonate and potassium hydrogen carbonate.

The coating amount of the modified polyvinyl acetal resin in the present invention is ^preferably from ^{3.0g / m 2 ~12.0g / m 2} , more ^{preferably 4.0g / m 2 ~9.0g / m 2} .

(Description of crosslinkable polymer latex)
The photothermographic material of the invention is characterized in that it has an undercoat layer coated with an aqueous coating solution containing a polymer latex having at least one crosslinkable group between the support and the image forming layer. Yes.

  In the present invention, the polymer latex having a crosslinkable group refers to a polymer latex having, as a constituent component, an ethylenically unsaturated monomer having a crosslinkable group such as an epoxy group, an active methylene group, an isocyanate group, and an oxazoline group. . Preferably, it is an ethylenically unsaturated monomer having a monomer unit having two or more crosslinking groups as a constituent component. The plurality of crosslinking groups may be the same as or different from each other.

  The polymer latex according to the present invention refers to a polymer component in which a water-insoluble hydrophobic polymer is dispersed as fine particles in water or a water-soluble dispersion medium. As the dispersion state, the polymer is emulsified in a dispersion medium, the emulsion polymerized, the micelle dispersed, or the polymer molecule has a partially hydrophilic structure and the molecular chain itself is molecularly dispersed. Anything may be used.

  As for the polymer latex according to the present invention, “synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki, published by Kobunshi Publishing Co., Ltd. (1978))”, “application of synthetic latex (Takaaki Sugimura, Ikuo Kataoka, Junichi Suzuki, Keiji Kasahara) Edited, published by Polymer Publishing Association (1993)), "chemistry of synthetic latex (written by Soichi Muroi, published by Polymer Publishing Society (1970))", and the like.

  The average particle diameter of the dispersed particles of the polymer latex is preferably in the range of 1 to 50,000 nm, more preferably about 5 to 1000 nm. Regarding the particle size distribution of the dispersed particles, those having a wide particle size distribution or monodispersed particle size distribution may be used.

  The polymer latex according to the present invention may be a so-called core / shell type polymer latex other than a normal polymer latex having a uniform structure. In this case, it may be preferable to change the glass transition temperature between the core and the shell.

  The minimum film-forming temperature (MFT) of the polymer latex according to the present invention is preferably −30 ° C. to 90 ° C., more preferably about 0 ° C. to 70 ° C. A film-forming auxiliary may be added to control the minimum film-forming temperature. A film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of a polymer latex. For example, “Synthetic Latex Chemistry (Souichi Muroi, published by Kobunshi Shuppankai (1970)” )"It is described in.

In the present invention, examples of the monomer having an epoxy group include glycidyl acrylate and glycidyl methacrylate.
Examples of the monomer having an isocyanate group include vinyl isocyanate and allyl isocyanate.
Examples of the monomer having an active methylene group include 2-acetoacetoxyethyl methacrylate, 2-acetoacetoxyethyl acrylate, 3-acetoacetoxypropyl methacrylate, and the like.

The polymer latex having a reactive group according to the present invention can be synthesized by emulsion polymerization, and may contain an ethylenically unsaturated monomer having no reactive group as a monomer component.
The ratio of the ethylenically unsaturated monomer having a reactive group in the polymer latex according to the present invention is preferably 5% by mass or more.

  Examples of the ethylenically unsaturated monomer having no reactive group that can be used in the present invention include acrylates, vinyl esters, and diolefins.

(Description of crosslinkable aqueous polyester)
The photothermographic material of the invention preferably has a layer containing an aqueous polyester having a crosslinkable group between the image forming layer and the undercoat layer containing a polymer latex having a crosslinkable group.
In the present invention, the aqueous polyester having a crosslinkable group refers to an aqueous polyester having, as a constituent, an ethylenically unsaturated monomer having a crosslinkable group such as an epoxy group, an active methylene group, an isocyanate group, and an oxazoline group. .

  The aqueous polyester according to the present invention is a substantially linear polyester obtained by polycondensation reaction of a polybasic acid or an ester-forming derivative thereof and a polyol or an ester-forming derivative thereof, and is further aqueous. Furthermore, the polyester which introduce | transduced as a copolymerization component into the polyester the component which has a hydrophilic group, for example, the component which has a sulfonate, a diethylene glycol component, a polyalkylene ether glycol component, a polyether dicarboxylic acid component, etc. is said. As the component having a hydrophilic group, a dicarboxylic acid having a sulfonate is preferably used.

  Examples of the polybasic acid component of the aqueous polyester include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, triflic acid. Mellitic acid, pyromellitic acid, dimer acid, maleic acid, fumaric acid, itaconic acid, p-hydroxybenzoic acid, p- (β-hydroxyethoxy) benzoic acid, or the like can be used. The dicarboxylic acid having a sulfonate is particularly preferably one having an alkali metal sulfonate group, such as 4-sulfoisophthalic acid, 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid, Examples include alkali metal salts such as 4-sulfonaphthalene-2,7-dicarboxylic acid and 5- (4-sulfophenoxy) isophthalic acid, among which sodium 5-sulfoisophthalic acid is particularly preferable. The dicarboxylic acids having these sulfonates should be used in the range of 5 mol% to 15 mol%, particularly 6 mol% to 10 mol%, based on the total dicarboxylic acid component, from the viewpoint of water solubility and water resistance. Is preferred.

  As the aqueous polyester, those having terephthalic acid and isophthalic acid as main dicarboxylic acid components are preferred, and the ratio of terephthalic acid and isophthalic acid to be used is 30/70 to 70/30 in molar ratio. It is particularly preferred from the viewpoint of applicability to water and solubility in water. The terephthalic acid component and isophthalic acid component are preferably contained in an amount of 50 mol% to 80 mol% based on the total dicarboxylic acid component, and an alicyclic dicarboxylic acid is preferably used as a copolymerization component. Examples of these alicyclic dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, Mention may be made of cyclohexyldicarboxylic acid. Furthermore, dicarboxylic acids other than those described above can be used as copolymerization components in the aqueous polyester according to the present invention using terephthalic acid and isophthalic acid as the main dicarboxylic acid components. Examples of these dicarboxylic acids include aromatic dicarboxylic acids and linear aliphatic dicarboxylic acids. The aromatic dicarboxylic acid is preferably used within a range of 30 mol% or less of the total dicarboxylic acid component. Examples of these aromatic dicarboxylic acid components include phthalic acid, 2,5-dimethylterephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and biphenyldicarboxylic acid. Further, the linear aliphatic dicarboxylic acid is preferably used within a range of 15 mol% or less of the total dicarboxylic acid component. Examples of these linear aliphatic dicarboxylic acid components include adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

  Examples of the polyol component include ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, and trimethylol. Propane, poly (ethylene oxide) glycol, or poly (tetramethylene oxide) glycol can be used. It is preferable to use what has 50 mol% or more of ethylene glycol as a glycol component of the aqueous | water-based polyester based on this invention.

The aqueous polyester according to the present invention can be synthesized using a dicarboxylic acid or an ester-forming derivative thereof and glycol or an ester-forming derivative thereof as starting materials.
Various methods can be used for the synthesis. For example, it can be obtained by a known polyester production method in which an initial condensate of dicarboxylic acid and glycol is formed by transesterification or direct esterification and melt polymerized. be able to. More specifically, for example, an ester exchange reaction between an ester of a dicarboxylic acid, for example, a dimethyl ester of a dicarboxylic acid, and a glycol is performed, and after distilling methanol, the pressure is gradually reduced and polycondensation is performed under a high vacuum. Method of performing, esterification reaction of dicarboxylic acid and glycol, distilling out the generated water, then gradually depressurizing, polycondensation under high vacuum, transesterification reaction between dicarboxylic acid ester and glycol And a method of performing polycondensation under high vacuum after adding an esterification reaction by adding dicarboxylic acid.

  Known transesterification catalysts and polycondensation catalysts can be used, such as manganese acetate, calcium acetate, and zinc acetate as transesterification catalysts, and antimony trioxide, germanium oxide, and dibutyltin as polycondensation catalysts. Oxide, titanium tetrabutoxide, or the like can be used. However, various conditions such as a polymerization method and a catalyst are not limited to the above examples.

  The aqueous polyester according to the present invention disperses a vinyl monomer in an aqueous solution in which an aqueous polyester exists, which is modified with a monomer component having the same composition as the polymer latex contained in the layer (A layer) closest to the support. The dispersion is obtained by, for example, dissolving aqueous polyester in hot water, dispersing the vinyl monomer in the aqueous solution of the obtained aqueous polyester, and performing emulsion polymerization or suspension polymerization. be able to. The polymerization is preferably by emulsion polymerization.

  Examples of the polymerization initiator that can be used include ammonium persulfate, potassium persulfate, sodium persulfate, and benzoyl peroxide. Of these, ammonium persulfate is preferred. The polymerization can be carried out without using a surfactant, but a surfactant can also be used as an emulsifier for the purpose of improving the polymerization stability. In this case, both general nonionic and anionic surfactants can be used.

  The monomer that can be used for modification is not particularly limited as long as it has the same composition as the polymer latex contained in the layer (A layer) closest to the support, but it was used for the polymer latex having the reactive group described above. It is more preferable to use a monomer.

  The amount of the modified monomer used is preferably such that the aqueous polyester / modified monomer has a mass ratio of 99/1 to 5/95, more preferably 97/3 to 50/50, and 95/5. It is particularly preferred that it is in the range of ~ 80/20.

(Structure of undercoat layer)
A surfactant, swelling agent, matting agent, crossover dye, antihalation dye, pigment, antifogging agent, preservative and the like may be added to the undercoat layer according to the present invention as necessary. As the swelling agent, phenol, resorcin, cresol, chlorophenol or the like is used, and the addition amount may be 1 g to 10 g per liter of the coating liquid of the present invention. As the matting agent, silica, polystyrene sphere, methyl methacrylate sphere or the like having a particle size of 0.1 μm to 10 μm is preferable.

The coating amount of the undercoat layer coating solution according to the present invention is preferably 0.01 mL to 10 mL, more preferably 0.1 mL to 3 mL per 1 m ^{2 in} solid content volume. The drying conditions are generally 120 ° C. to 200 ° C. and about 10 seconds to 10 minutes.

  The undercoat layer according to the present invention preferably includes a step of heat-treating at a temperature of 130 ° C. or more and less than 160 ° C. for 1 minute or more and less than 3 minutes after coating and drying. When the temperature is lower than this temperature, the flatness of the base deteriorates. On the other hand, when the temperature is higher, the shrinkage becomes remarkable, which is not preferable. If it is less than 1 minute, the reaction of the reactive group of the polymer latex does not proceed sufficiently, and a desired film may not be obtained. On the other hand, if it exceeds 3 minutes, the planarity of the support may be impaired.

  The undercoat layer according to the present invention can be formed by coating and drying using a generally well-known coating method. Examples of the coating method that can be used include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, or a hopper described in US Pat. No. 2,681,294. Extrusion coating method using If necessary, US Pat. Nos. 2,761,791, 3,508,947, 2,941,898 and 3,526,528, Yuji Harasaki, “Coating Engineering”, page 253 A method of simultaneously applying two or more layers described in (published by Asakura Shoten in 1973) can also be used.

(Explanation of photosensitive silver halide)
1) Halogen composition The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and is silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver chloroiodobromide, or iodide. Silver can be used. Of these, silver bromide and silver iodobromide are preferred. The distribution of the halogen composition in the grains 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 also 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. In addition, silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver chloroiodobromide, silver iodide are silver chloride, silver chlorobromide, silver bromide, silver iodobromide, chloroiodobromide A technique for localizing silver or silver iodide can also be preferably used.

2) Grain size If the grain size of the silver halide used in the present invention is large, the transparency of the film after image formation is undesirably reduced. The preferred silver halide grain size is 0.20 μm or less, more preferably 0.01 μm to 0.15 μm, and still more preferably 0.02 μm to 0.12 μm. The term “particle size” as used herein refers to the average of diameters when observed with an electron microscope and converted into a circle having the same area as the projected area (in the case of tabular grains, the projected area of the main plane).

3) coating amount of the coating amount such silver halide ^{grains, 0.03g / m 2 ~0.6g / m} 2 shows a silver amount, preferably 0.05g ^{/ m 2} ~0.4g ^/ m 2 , more preferably from ^{0.07g / m 2 ~0.3g / m 2} . 0.01 mol or more and 0.5 mol or less, preferably 0.02 mol or more and 0.3 mol or less, more preferably 0.03 mol or more and 0 mol per 1 mol of silver of the non-photosensitive organic silver salt described later. .2 mol or less.

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

  For example, a so-called hydration method in which a part of the organic silver salt is halogenated with an organic or inorganic halide is also preferably used. The organic halide used here may be any compound that reacts with an organic silver salt to produce silver halide, but N-halogenoimide (N-bromosuccinimide, etc.), halogenated quaternary nitrogen compound (odor) And tetrabutylammonium bromide), and aggregates of halogenated quaternary nitrogen salts and halogen molecules (pyridinium perbromide). Any inorganic halogen compound may be used as long as it is a compound that reacts with an organic silver salt to produce silver halide, but alkali metal halide or ammonium (sodium chloride, lithium bromide, potassium iodide, ammonium bromide, etc.) ), Alkaline earth metal halides (calcium bromide, magnesium chloride, etc.), transition metal halides (ferric chloride, cupric bromide, etc.), metal complexes having a halogen ligand (sodium iridate bromide) , Ammonium rhodate, etc.) and halogen molecules (bromine, chlorine, iodine). Moreover, you may use desired organic inorganic halide together. The amount of halide added at the time of hydration is preferably 1 mmol to 500 mmol, more preferably 10 mmol to 250 mmol as a halogen atom per mole of the organic silver salt.

  The photosensitive silver halide grains can be desalted by washing with water known in the art, such as a noodle method or a flocculation method, but in the present invention, it may or may not be desalted.

5) Grain shape Examples of the shape of silver halide grains include cubic grains, octahedral grains, tetradecahedral grains, dodecahedron grains, tabular grains, spherical grains, rod-shaped grains, and potato grains. In particular, dodecahedral grains, tetrahedral grains, and tabular grains are preferable. The silver halide having a high silver iodide content composition of the present invention can take a complicated form. L. JENKINS et al. J of Photo. Sci. Vol. 28 (1980) p164-Fig1. FIG. Tabular grains as shown in Fig. 1 are also preferably used. Grains with rounded corners of silver halide grains can also be preferably used. The surface index (Miller index) of the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the [100] plane having high spectral sensitization efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The proportion is preferably 50% or more, more preferably 65% or more, and further preferably 80% or more. The ratio of the Miller index [100] plane is determined by T.T. Tani; Imaging Sci. 29, 165 (1985).

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

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

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

In addition to water, the hexacyano metal complex is miscible with a mixed solvent or gelatin with an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters, or amides). Can be added.
The addition amount of the hexacyano metal complex is preferably 1 × 10 ⁻⁵ mol or more and 1 × 10 ⁻² mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻³ mol or less per mol of silver.

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

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

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

  Regarding other metal atoms that can be contained in the silver halide grains used in the present invention, silver salt emulsion desalting methods and chemical sensitization methods, JP-A-11-84574, paragraph numbers 0046 to 0050, JP-A-11 No. -65021, paragraph numbers 0025 to 0031 and JP-A No. 11-119374, paragraph numbers 0242 to 0250.

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

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

The amount of sulfur, selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but is preferably 10 ⁻⁸ to 10 ⁻² mol per mol of silver halide, preferably About 10 ⁻⁷ to 10 ⁻³ mol is used.

The photosensitive silver halide grains in the present invention may be chemically sensitized by a gold sensitizing method together with the chalcogen sensitization described above. As the gold sensitizer, the valence of gold is preferably +1 or +3.
Representative examples of gold compounds include chloroauric acid, bromoauric acid, potassium chloroaurate, potassium bromoaurate, auric trichloride, potassium aurithiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, Or a pyridyl trichloro gold etc. are preferable. Further, gold sensitizers described in US Pat. No. 5,858,637 and JP-A No. 2002-278016 are also preferably used.
The amount of the gold sensitizer used in combination varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol to 10 ⁻³ mol, more preferably 10 ⁻⁶ mol to 5 × 10 ⁻⁴ mol per mol of silver halide. It is.

In the present invention, chemical sensitization can be performed at any time after particle formation and before coating. After desalting, (1) before spectral sensitization, (2) simultaneously with spectral sensitization, (3) spectral After sensitization, there may be (4) immediately before application.
The conditions for chemical sensitization in the present invention are not particularly limited, but the pH is 5 to 8, the pAg is 6 to 11, and the temperature is about 40 ° C to 95 ° C.

  A thiosulfonic acid compound may be added to the silver halide emulsion used in the present invention by the method described in European Patent Publication No. 293,917.

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

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

In the present invention, the one-electron oxidant produced by one-electron oxidation contained in the photothermographic material is a compound selected from the following types 1 and 2 that can emit one electron or more.
(Type 1)
A compound in which a one-electron oxidant produced by one-electron oxidation can further emit one or more electrons with a subsequent bond cleavage reaction.
(Type 2)
A compound capable of emitting one or more electrons after a one-electron oxidant produced by one-electron oxidation undergoes a subsequent bond formation reaction.

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

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

In the formula, RED ₁ and RED ₂ represent a reducing group. R ₁ represents a non-metallic atomic group capable of forming a cyclic structure corresponding to a tetrahydro form of a 5-membered or 6-membered aromatic ring (including an aromatic heterocycle) or an octahydro form together with the carbon atom (C) and RED _1. To express. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. L ₁ represents a leaving group. ED represents an electron donating group. Z ₁ represents an atomic group capable of forming a 6-membered ring with a nitrogen atom and two carbon atoms of a benzene ring. X ₁ represents a substituent, and m 1 represents an integer of 0 to 3. Z ₂ represents —CR ₁₁ R ₁₂ —, —NR ₁₃ —, or —O—.
R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent. R ₁₃ represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. X ₁ represents an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylamino group, an arylamino group, or a heterocyclic amino group. L ₂ represents a carboxy group or a salt thereof, or a hydrogen atom. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

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

In the formula, X represents a reducing group that is one-electron oxidized. Y reacts with a one-electron oxidant formed by one-electron oxidation of X to form a new bond, a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site, or a benzo The reactive group containing the non-aromatic heterocyclic part of a condensed ring is represented. L ₂ represents a linking group for linking X and Y. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

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

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

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

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

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

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

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

Formula _{(X) (P-Q 1} -) i -R (-Q 2 -S) j

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

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

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

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

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

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

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

The mercapto group (or salt thereof) as the adsorptive group means the mercapto group (or salt thereof) itself, and more preferably a heterocyclic group or aryl group substituted with at least one mercapto group (or salt thereof) or Represents an alkyl group. Here, the heterocyclic group is at least a 5- to 7-membered monocyclic or condensed aromatic or non-aromatic heterocyclic group such as an imidazole ring group, a thiazole ring group, an oxazole ring group, or a benzimidazole ring. Group, benzothiazole ring group, benzoxazole ring group, triazole ring group, thiadiazole ring group, oxadiazole ring group, tetrazole ring group, purine ring group, pyridine ring group, quinoline ring group, isoquinoline ring group, pyrimidine ring group, And triazine ring group. Moreover, the heterocyclic group containing the quaternized nitrogen atom may be sufficient, and in this case, the substituted mercapto group may dissociate and it may become a meso ion. When the mercapto group forms a salt, the counter ion includes a cation such as alkali metal, alkaline earth metal, heavy metal (Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ag ⁺ , or Zn ²⁺ ), ammonium ion, Examples thereof include a heterocyclic group containing a quaternized nitrogen atom, and a phosphonium ion.
Further, the mercapto group as the adsorptive group may be tautomerized into a thione group.
The thione group as an adsorptive group includes a chain or cyclic thioamide group, thioureido group, thiourethane group, or dithiocarbamate group.
A heterocyclic group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom and a tellurium atom as the adsorptive group is a -NH- group capable of forming imino silver (> NAg) as a partial structure of the heterocyclic ring. A nitrogen-containing heterocyclic group, or a heterocyclic group having a -S- group, a -Se- group, a -Te- group, or a = N- group as a partial structure of the heterocyclic ring, which can be coordinated to a silver ion by a coordination bond In the former example, benzotriazole group, triazole group, indazole group, pyrazole group, tetrazole group, benzimidazole group, imidazole group, or purine group, and the latter examples include thiophene group, thiazole group, oxazole group, Benzothiophene group, benzothiazole group, benzoxazole group, thiadiazole group, oxadiazole group, triazine group, Renoazoru group, benzoselenazole group, tellurium azole group, and the like benzo tellurium azole group.
Examples of the sulfide group or disulfide group as the adsorptive group include all groups having a partial structure of -S- or -SS-.
The cationic group as the adsorptive group means a group containing a quaternized nitrogen atom, specifically, an ammonio group or a group containing a nitrogen-containing heterocyclic group containing a quaternized nitrogen atom. Examples of the nitrogen-containing heterocyclic group containing a quaternized nitrogen atom include a pyridinio group, a quinolinio group, an isoquinolinio group, an imidazolio group, and the like.
An ethynyl group as an adsorptive group means a —C≡CH group, and the hydrogen atom may be substituted.
The adsorbing group may have an arbitrary substituent.

  Furthermore, specific examples of the adsorbing group include those described in the specifications p4 to p7 of JP-A No. 11-95355.

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

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

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

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

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

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

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

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

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

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

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

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

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

12) Mixing of silver halide and organic silver salt The photosensitive silver halide grain of the present invention can be prepared by the conversion method as described above, but is formed in the absence of a non-photosensitive organic silver salt, Particularly preferred is chemical sensitization.

  An organic silver salt is obtained by adding an alkali metal salt (for example, sodium hydroxide, potassium hydroxide, etc.) to an organic acid to make at least a part of the organic acid into an alkali metal soap of the organic acid, and then water-soluble silver salt (for example, The photosensitive silver halide can be added at any stage. The main mixing steps are: A) Add silver halide to organic acid in advance, add alkali metal salt, then add water-soluble silver salt, B) Halogenation after preparing alkali metal soap of organic acid Mix silver, then add water-soluble silver salt, C) Make an alkali metal soap of organic acid, chlorinate part of it, add silver halide, and then perform the remaining silver chloride D) There are four steps of mixing the silver halide after preparing the organic silver salt. Preference is given to B) or C).

  The organic silver salt containing silver halide is preferably used dispersed in fine particles. As a means for dispersing the fine particles, a high-speed stirrer, a ball mill, a sand mill, a colloid mill, a vibration mill, a high-pressure homogenizer, or the like can be used.

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

(Description of spectral sensitizing dye)
The photothermographic material of the invention is preferably sensitized with a spectral sensitizing dye. Preferably, spectral sensitization is performed at 700 nm to 1400 nm. In particular, spectral sensitization is preferably performed so as to have a sensitization maximum in the near infrared region of 750 nm to 900 nm.

  The spectral sensitizing dye that can be used in the heat-developable photosensitive material of the present invention may be any spectral sensitizing maximum wavelength within this range, but at least a spectral sensitizing dye selected from the general formulas (3a) to (3d). One type is preferred. Next, the details of the spectral sensitizing dyes represented by the general formulas (3a) to (3d) (hereinafter also referred to as “infrared photosensitive dyes”) will be described.

In the general formulas (3a) to (3d), the aliphatic groups represented by R ₁ , R ₂ , R ₁₁ and R ₁₂ are, for example, branched or straight chain having 1 to 10 carbon atoms. Chain alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, iso-pentyl group, 2-ethyl-hexyl group, octyl group, decyl group, etc.), 3 to 10 carbon atoms Alkenyl groups (for example, 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, etc.), 7 to 7 carbon atoms 10 aralkyl groups (for example, benzyl group, phenethyl group, etc.) can be mentioned. The above-described groups are further represented by lower alkyl groups (for example, methyl group, ethyl group, propyl group, etc.), halogen atoms (for example,

Fluorine atom, chlorine atom, bromine atom, etc.), vinyl group, aryl group (eg, phenyl group, p-tolyl group, p-bromophenyl group, etc.), trifluoromethyl group, alkoxy group (eg, methoxy group, ethoxy group) , Methoxyethoxy group, etc.), aryloxy group (eg, phenoxy group, p-tolyloxy group, etc.), cyano group, sulfonyl group (eg, methanesulfonyl group, trifluoromethanesulfonyl group, p-toluenesulfonyl group, etc.), alkoxycarbonyl Group (for example, ethoxycarbonyl group, butoxycarbonyl group, etc.), amino group (for example, amino group, biscarboxymethylamino group, etc.), aryl group (for example, phenyl group, carboxyphenyl group, etc.), heterocyclic group (for example, Tetrahydrofurfuryl, 2-pyrrolidinon-1-yl group, etc.), a Group (for example, acetyl group, benzoyl group, etc.), ureido group (for example, ureido group, 3-methylureido group, 3-phenylureido group, etc.), thioureido group (for example, thioureido group, 3-methylthioureido group, etc.) ,

An alkylthio group (for example, methylthio, ethylthio group, etc.), an arylthio group (for example, phenylthio group, etc.), a heterocyclic thio group (for example, 2-thienylthio group, 3-thienylthio, 2-imidazolylthio group, etc.), a carbonyloxy group ( For example, groups such as acetyloxy group, propanoyloxy group, benzoyloxy group), acylamino group (for example, acetylamino, benzoylamino group, etc.), thioamide group (for example, thioacetamido group, thiobenzoylamino group, etc.), Alternatively, for example, a sulfo group, a carboxy group, a phosphono group, a sulfate group, a hydroxy group,

Mercapto group, sulfino group, carbamoyl group (for example, carbamoyl group, N-methylcarbamoyl group, N, N-tetramethylenecarbamoyl group, etc.), sulfamoyl group (for example, sulfamoyl group, N, N-3-oxapentamethyleneaminosulfonyl) Group), sulfonamide group (eg, methanesulfonamide, butanesulfonamide group, etc.), sulfonylaminocarbonyl group (eg, methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl group, etc.), acylaminosulfonyl group (eg, acetamidosulfonyl) , Methoxyacetamidosulfonyl group, etc.), acylaminocarbonyl group (eg, acetamidocarbonyl, methoxyacetamidocarbonyl group, etc.), sulfinylaminocarbonyl group (eg, methanesulfuryl group) It alkylsulfonyl aminocarbonyl, or ethanesulfonic Huy arylsulfonylamino group, etc.), a hydrophilic group such may be substituted.

  Specific examples of the aliphatic group substituted with these hydrophilic groups include carboxymethyl, carboxyethyl, carboxybutyl, carboxypentyl, 3-sulfatobutyl, 3-sulfopropyl, and 2-hydroxy-3-sulfopropyl groups. 4-sulfobutyl, 5-sulfopentyl, 3-sulfopentyl, 3-sulfinobutyl, 3-phosphonopropyl, hydroxyethyl, N-methanesulfonylcarbamoylmethyl, 2-carboxy-2-propenyl, o-sulfobenzyl, Examples of each group include p-sulfophenethyl and pcarboxybenzyl.

R _3, each with _{R 4,} R ₁₃ and R _14, the lower alkyl group represented example, straight-chain having a carbon number of 5 or less as an alkyl group, a branched group, a methyl group, an ethyl group Propyl group, butyl group, pentyl group, isopropyl group and the like. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, and a cyclopentyl group. Examples of the alkenyl group include 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, and 4-hexenyl group. Examples of the aralkyl group include a benzyl group, a phenethyl group, a p-methoxyphenylmethyl group, and an o-acetylaminophenylethyl group, and the aryl group includes a substituted or unsubstituted group such as a phenyl group. , 2-naphthyl group, 1-naphthyl group, o-tolyl group, o-methoxyphenyl group, m-chlorophenyl group, m-bromophenyl group, p-tolyl group, and p-ethoxyphenyl group. And heterocyclic groups include substituted and unsubstituted groups such as 2-furyl group, 5-methyl-2-furyl group, 2-thienyl group, and 3-thienyl. , 2-imidazolyl group, 2-methyl-1-imidazolyl group, 4-phenyl-2-thiazolyl, 5-hydroxy-2-benzothiazolyl group, 2-pyridyl group, and a group such as 1-pyrrolyl group.

  Each of these groups includes a lower alkyl group (for example, methyl group, ethyl group, etc.), a lower alkoxy group (for example, methoxy group, ethoxy group, etc.), a hydroxy group, a halogen atom (for example, fluorine atom, chlorine atom, bromine atom) , Iodine atoms), aryl groups (for example, phenyl group, tolyl group, chlorophenyl group, etc.), mercapto groups, lower alkylthio groups (for example, metolthio group, ethylthio group, etc.) and the like can be substituted.

Each in _{W 1 ~W 4, W 11 ~W} 14, the substituent represented Specifically, the alkyl group (e.g., methyl group, ethyl group, butyl group, etc. isobutyl group), an aryl group (monocyclic as well as multi A ring group, for example, a phenyl group, a naphthyl group, etc., a heterocyclic group (for example, each group such as thienyl, furyl, pyridyl, carbazolyl, pyrrolyl, indolyl, etc.), a halogen atom (for example, a fluorine atom, a chlorine atom, Bromine atom, etc.), vinyl group, aryl group (eg, phenyl group, p-tolyl group, p-bromophenyl group, etc.), trifluoromethyl group, alkoxy group (eg, methoxy group, ethoxy group, methoxyethoxy group, etc.) , Aryloxy groups (for example, phenoxy group, p-tolyloxy group, etc.), sulfonyl groups (for example, methanesulfonyl group, p-toluenesulfonyl group, etc.) ), Alkoxycarbonyl groups (for example, ethoxycarbonyl group, butoxycarbonyl group, etc.), amino groups (for example, amino group, biscarboxymethylamino group, etc.), aryl groups (for example, phenyl group, carboxyphenyl group, etc.), heterocyclic rings Group (for example, tetrahydrofurfuryl, 2-pyrrolidinon-1-yl group, etc.), acyl group (for example, acetyl group, benzoyl group, etc.), ureido group (for example, ureido group, 3-methylureido group, 3-phenylureido) Groups), thioureido groups (eg, thioureido groups, 3-methylthioureido groups, etc.), alkylthio groups (eg, methylthio, ethylthio groups, etc.), arylthio groups (eg, phenylthio groups, etc.), hydroxy groups, styryl groups, etc. It is done.

These are based can replace the groups exemplified in the description of the aliphatic group represented by R ₁ or the like, specific examples of the substituted alkyl group, e.g., 2-methoxyethyl, 2-hydroxyethyl, 3-ethoxy Examples include substituted groups such as carbonylpropyl, 2-carbamoylethyl, 2-methanesulfonylethyl, 3-methanesulfonylaminopropyl, benzyl, phenethyl, carboxymethyl, carboxyethyl, allyl, and 2-furylethyl. Specific examples of the group include p-carboxyphenyl, pN, N-dimethylaminophenyl, p-morpholinophenyl, p-methoxyphenyl, 3,4-dimethoxyphenyl, and 3,4-methylenedioxyphenyl. , 3-chlorophenyl and p-nitrophenyl groups, substituted and substituted Specific examples of the cyclic group include groups such as 5-chloro-2-pyridyl, 5-ethoxycarbonyl-2-pyridyl, and 5-carbamoyl-2-pyridyl.

W ₁ and W ₂ , W ₃ and W ₄ , W ₁₁ and W ₁₂ , W ₁₃ and W ₁₄ , R ₃ and W ₁ , R ₃ and W ₂ , R ₁₃ and W ₁₁ , R ₁₃ and W ₁₂ , R ₄ And W ₃ , R ₄ and W ₄ , R ₁₄ and W ₁₃ , and R ₁₄ and W ₁₄ may be connected to each other to form a condensed ring, for example, 5-membered, 6-membered saturated or An unsaturated condensed carbocycle is mentioned. These condensed rings can be substituted at any position, and examples of the substituted group include the groups described above for the group that can be substituted with the aliphatic group.

In the general formulas (3a) to (3d), the methine groups represented by L _{1 to} L ₉ and L _{11 to} L ₁₅ each independently represent a substituted or unsubstituted methine group. Specific examples of the substituted group include a substituted or unsubstituted lower alkyl group (for example, methyl group, ethyl group, iso-propyl group, or benzyl group), alkoxy group (for example, methoxy group, ethoxy group, etc.). ), Aryloxy group (for example, phenoxy group, naphthoxy group, etc.), aryl group (for example, phenyl group, naphthyl group, p-tolyl group, o-carboxyphenyl group, etc.), -N (V ₁ , V ₂ ) , -SR or a heterocyclic group (for example, 2-thienyl group, 2-furyl group, N, N'-bis (methoxyethyl) barbituric acid group, etc.). Here, R represents a lower alkyl group, aryl group or heterocyclic group as described above, and V ₁ and V ₂ each represents a substituted or unsubstituted lower alkyl group or aryl group, and V ₁ and V ₂ Can be linked together to form a 5- or 6-membered nitrogen-containing heterocycle. In addition, methine groups can be linked to each other adjacent to each other or to a methine group separated by one to form a 5-membered or 6-membered ring.

In the compounds represented by the general formulas (3a) to (3d), when a group having a cation or anion charge is substituted, an equivalent amount of anion or cation is provided so that the charge in the molecule is offset. Thus, a counter ion is formed. For example, each in X _1, X _11, Specific examples of the cation at the ion necessary to cancel charges in the molecule shown, proton, an organic ammonium ion (e.g., triethylammonium, etc. triethanolammonium each Ions), inorganic cations (eg, cations such as lithium, sodium, and potassium), and specific examples of acid anions include, for example, halogen ions (eg, chlorine ions, bromine ions, iodine ions, etc.), p-toluenesulfone, and the like. Examples include acid ions, perchlorate ions, boron tetrafluoride ions, sulfate ions, methyl sulfate ions, ethyl sulfate ions, methanesulfonate ions, and trifluoromethanesulfonate ions.

  Specific examples of the photosensitive dyes represented by the general formulas (3a) to (3d) are shown below, but the present invention is not limited to these compounds.

  Infrared photosensitive dyes represented by the general formulas (3a) to (3d) used in the present invention include, for example, HM Hammer, The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dies and Related Compounds (A. Weissberger ed.Interscience, New York, 1964), JP-A-3-138638, JP-A-10-73900, JP-A-9-510022, US Pat. No. 2,734,900, British Patent No. 774779, JP They can be synthesized by the methods described in Kaihei 2000-095958 and Japanese Patent Application No. 11-58686.

In the present invention, the infrared photosensitive dyes represented by the general formulas (3a) to (3d) may be used alone or in combination of two or more photosensitive dyes. If the infrared-sensitive dye was used alone, and when combined, the per mol of silver halide, respectively in total, 1 × ^{10 -6} mol to 5 × ^{10 -3} mol, preferably 1 × ^{10 -5} It is contained in the silver halide emulsion in a proportion of from mol to 2.5 × 10 ⁻³ mol, more preferably from 4 × 10 ⁻⁵ mol to 1 × 10 ⁻³ mol. In the present invention, when two or more photosensitive dyes are used in combination, the photosensitive dye can be contained in the silver halide emulsion in an arbitrary ratio.

  Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A-11-65021, compounds represented by the general formula (II) of JP-A-10-186572, and general formulas (I) of JP-A-11-119374 ) And the dye described in Example 5 of U.S. Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59-48753. No. 19, page 38 to line 20, page 35 of European Patent Publication No. 0803764A1, JP 2001-272747, JP 2001-290238, JP 2002-023306, etc. It is described in. These sensitizing dyes may be used alone or in combination of two or more. In the present invention, the time when the sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from the desalting to the completion of chemical ripening.

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

  In addition to the spectral sensitizing dyes represented by the above (Da) to (Dd), other conventionally known sensitizing dyes may be used in combination with the photosensitive silver halide of the present invention. Regarding sensitizing dyes that can be used in combination and addition methods, paragraphs 0103 to 0109 of JP-A-11-65021, compounds represented by general formula (II) of JP-A-10-186572, and general formulas of JP-A-11-119374 The dye represented by (I) and paragraph number 0106, the dyes described in Example 5 of US Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59 Dyes disclosed in JP-A-48753, page 19 line 38 to page 20 line 35 of European Patent Publication No. 0803764A1, JP-A-2001-272747, JP-A-2001-290238, JP-A-2002-023306 It is described in the issue. These sensitizing dyes may be used alone or in combination of two or more. The time for adding these sensitizing dyes to the silver halide emulsion is preferably the time from the desalting step to the coating.

(Non-photosensitive organic silver salt)
1) Composition The organic silver salt that can be used in the present invention is relatively stable to light, but is heated to 80 ° C. or higher in the presence of exposed photosensitive silver halide and a reducing agent. In this case, the silver salt functions as a silver ion supplier to form a silver image. The organic silver salt may be any organic substance that can supply silver ions that can be reduced by a reducing agent. As for such non-photosensitive organic silver salt, paragraph numbers 0048 to 0049 of JP-A-10-62899, page 18 line 24 to page 19 line 37 of European Patent Publication No. 0803764A1, European Patent Publication. No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, and the like. Silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30 carbon atoms, preferably 15 to 28 carbon atoms) are preferred. Preferred examples of the fatty acid silver salt include silver lignocerate, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver erucate and the like. Including a mixture of In the present invention, among these fatty acid silvers, the silver behenate content is preferably 50 mol% to 100 mol%, more preferably 85 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%. The following fatty acid silver is preferably used. Furthermore, it is preferable to use fatty acid silver having a silver erucate content of 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0.1 mol% or less.

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

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

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

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

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

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

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

3) Preparation Known methods and the like can be applied to the production and dispersion method of the organic acid silver used in the present invention. For example, the above-mentioned JP-A-10-62899, European Patent Publication No. 0803763A1, European Patent Publication No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, JP-A-2001-163889, 2001-163890, 2001-163828, 2001-33907, 2001-188313, 2001-83651, 2002-6442, 2002-49117, 2002-31870, 2002-107868 You can refer to the issue.

  In addition, when the photosensitive silver salt is allowed to coexist at the time of dispersion of the organic silver salt, the fog rises and the sensitivity is remarkably lowered. Therefore, it is more preferable that the photosensitive silver salt is not substantially contained at the time of dispersion. In the present invention, the amount of the photosensitive silver salt in the aqueous dispersion to be dispersed is preferably 1 mol% or less, more preferably 0.1 mol% with respect to 1 mol of the organic acid silver salt in the liquid. The following is more preferable, and positive addition of photosensitive silver salt is not performed.

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

4) Addition Amount organic silver salt in the invention can be used in a desired amount, preferably 0.1g ^{/ m 2} ~3.0g ^/ m 2 as the total amount of coated silver halide silver was also included, and more preferably 0 ^{.5g / m 2 ~2.0g / m 2} , more preferably from ^{0.8g / m 2 ~1.7g / m 2} . In particular, in order to improve image storability, the total coated silver amount is preferably 1.5 g / m ² or less, more preferably 1.3 g / m ² or less.

(Reducing agent)
The photothermographic material of the present invention preferably contains a heat developer that is a reducing agent for silver ions. The reducing agent may be any substance (preferably an organic substance) that reduces silver ions to metallic silver. Examples of such reducing agents are described in JP-A No. 11-65021, paragraphs 0043 to 0045, and European Patent Publication No. 0803764A1, page 7, line 34 to page 18, line 12.

  In the present invention, the reducing agent is preferably a so-called hindered phenol-based reducing agent or bisphenol-based reducing agent having a substituent at the ortho position of the phenolic hydroxyl group, and more preferably a compound represented by the following general formula (R).

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

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

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

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

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

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

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

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

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

  Examples of preferable reducing agents of the present invention other than the above are the compounds described in JP-A Nos. 2001-188314, 2001-209145, 2001-350235, 2002-156727, and EP1278101A2.

The addition amount of the reducing agent is preferably a ^{0.1g / m 2 ~3.0g / m 2} , more preferably ^{0.2g / m 2 ~1.5g / m 2} , more preferably 0 .3 g / m ^{2 to} 1.0 g / m ² . 5 mol% to 50 mol% is preferably contained with respect to 1 mol of silver on the surface having the image forming layer, more preferably 8 mol% to 30 mol%, and 10 mol% to 20 mol%. More preferably. The reducing agent is preferably contained in the image forming layer.

The reducing agent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form or a solid fine particle dispersion form, and may be contained in the photothermographic material.
In the case of applying an organic solvent as a coating solvent, it is generally added by dissolving using an organic solvent such as methyl ethyl ketone, methanol, ethanol, acetone, or toluene.

(Development accelerator)
In the photothermographic material of the present invention, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, or the like as a development accelerator, Hindered phenol compounds represented by general formula (II) described in JP-A No. 2001-92075, general formula (I) described in JP-A No. 10-62895, JP-A No. 11-15116 and the like, A hydrazine-based compound represented by general formula (D) of JP-A No. 2002-156727 or general formula (1) described in JP-A No. 2002-278017, and described in JP-A No. 2001-264929 A phenolic or naphtholic compound represented by the general formula (2) is preferably used. These development accelerators are used in the range of 0.1 to 20 mol% with respect to the reducing agent, preferably in the range of 0.5 to 10 mol%, more preferably in the range of 1 to 5 mol%. The introduction method to the light-sensitive material includes the same method as the reducing agent, but it is particularly preferable to add as a solid dispersion or an emulsified dispersion. When added as an emulsified dispersion, it is added as an emulsified dispersion dispersed using a high-boiling solvent and a low-boiling auxiliary solvent that are solid at room temperature, or as a so-called oilless emulsified dispersion without using a high-boiling solvent It is preferable to add.
In the present invention, among the development accelerators described above, hydrazine compounds represented by the general formula (D) described in JP-A No. 2002-156727 and those described in JP-A No. 2001-264929 A phenol-based or naphthol-based compound represented by the formula (2) is more preferable.

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

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

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

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

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

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

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

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

In General Formula (A-2), R ₁ represents an alkyl group, an acyl group, an acylamino group, a sulfonamide group, an alkoxycarbonyl group, or a carbamoyl group. R ₂ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acyloxy group, or a carbonate group. R ₃ and R ₄ each represents a group that can be substituted on the benzene ring mentioned in the example of the substituent of formula (A-1). R ₃ and R ₄ may be connected to each other to form a condensed ring.

R ₁ is preferably an alkyl group having 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, an isopropyl group, a butyl group, a tert-octyl group, or a cyclohexyl group), an acylamino group (for example, an acetylamino group, a benzoylamino group, Methylureido group or 4-cyanophenylureido group), carbamoyl group (n-butylcarbamoyl group, N, N-diethylcarbamoyl group, phenylcarbamoyl group, 2-chlorophenylcarbamoyl group, 2,4-dichlorophenylcarbamoyl group, etc.) ) Is more preferably an acylamino group (including a ureido group and a urethane group). R ₂ is preferably a halogen atom (more preferably a chlorine atom or a bromine atom), an alkoxy group (such as a methoxy group, a butoxy group, an n-hexyloxy group, an n-decyloxy group, a cyclohexyloxy group, or a benzyloxy group), An aryloxy group (such as a phenoxy group or a naphthoxy group);

R ₃ is preferably a hydrogen atom, a halogen atom, or an alkyl group having 1 to 20 carbon atoms, and most preferably a halogen atom. R ₄ is preferably a hydrogen atom, an alkyl group, or an acylamino group, and more preferably an alkyl group or an acylamino group. Examples of these preferable substituents are the same as those for R ₁ . When R ₄ is an acylamino group, R ₄ is preferably linked to R ₃ to form a carbostyryl ring.

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

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

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

In the general formula (D), R ²¹ to R ²³ each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group or a heterocyclic group, and these groups may be substituted even if they are unsubstituted. You may have.
When R ²¹ to R ²³ have a substituent, the substituent is a halogen atom, alkyl group, aryl group, alkoxy group, amino group, acyl group, acylamino group, alkylthio group, arylthio group, sulfonamide group, acyloxy group, Examples thereof include an oxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, and a phosphoryl group. Preferred examples of the substituent include an alkyl group and an aryl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, Examples thereof include an octyl group, a phenyl group, a 4-alkoxyphenyl group, and a 4-acyloxyphenyl group.

Specific examples of the alkyl group of R ²¹ to R ²³ include a methyl group, an ethyl group, a butyl group, an octyl group, a dodecyl group, an isopropyl group, a t-butyl group, a t-amyl group, a t-octyl group, a cyclohexyl group, Examples thereof include 1-methylcyclohexyl group, benzyl group, phenethyl group, and 2-phenoxypropyl group.
Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-t-butylphenyl group, a 4-t-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group.

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

R ²¹ to R ²³ are preferably an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. From the viewpoint of the effect of the present invention, at least one of R ²¹ to R ²³ is preferably an alkyl group or an aryl group, and more preferably two or more are an alkyl group or an aryl group. In addition, it is preferable that R ²¹ to R ²³ are the same group in that they can be obtained at low cost.

  Specific examples of the hydrogen bonding compound including the compound of the general formula (D) in the present invention are shown below, but the present invention is not limited thereto.

Specific examples of the hydrogen bonding compound include those described in European Patent No. 1096310, JP-A No. 2002-156727, and JP-A No. 2002-318431 in addition to the above.
The compound of the general formula (D) of the present invention can be used in a photothermographic material by being incorporated in a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersion fine particle dispersion in the same manner as the reducing agent. It is preferably used as a solid dispersion. The compound of the present invention forms a hydrogen-bonding complex with a compound having a phenolic hydroxyl group or amino group in a solution state, and depending on the combination of the reducing agent and the compound of the general formula (D) of the present invention, It can be isolated in the crystalline state.

  The compound of the general formula (D) of the present invention is preferably used in the range of 1 mol% to 200 mol%, more preferably in the range of 10 mol% to 150 mol%, still more preferably relative to the reducing agent. It is in the range of 20 mol% to 100 mol%.

(Anti-fogging agent)
1) Organic polyhalogen compound Hereinafter, preferred organic polyhalogen compounds that can be used in the present invention will be described in detail. A preferred polyhalogen compound of the present invention is a compound represented by the following general formula (H).

General formula (H)
Q- (Y) n-C (Z ₁ ) (Z ₂ ) X

In General Formula (H), Q represents an alkyl group, an aryl group, or a heterocyclic group, Y represents a divalent linking group, n represents 0 to ₁ , Z ₁ and Z ₂ represent a halogen atom, X represents a hydrogen atom or an electron withdrawing group.
In general formula (H), Q is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heterocyclic group containing at least one nitrogen atom (pyridine, quinoline group, etc.).

In the general formula (H), when Q is an aryl group, Q preferably represents a phenyl group substituted with an electron-withdrawing group having a positive Hammett's substituent constant σp. For Hammett's substituent constants, see Journal of Medicinal Chemistry, 1973, Vol. 16, no. 11, 1207-1216 etc. can be referred to.
Examples of such an electron withdrawing group include a halogen atom, an alkyl group substituted with an electron withdrawing group, an aryl group substituted with an electron withdrawing group, a heterocyclic group, an alkyl or arylsulfonyl group, acyl Group, alkoxycarbonyl group, carbamoyl group, sulfamoyl group and the like. Particularly preferred as the electron withdrawing group is a halogen atom, a carbamoyl group, or an arylsulfonyl group, and a carbamoyl group is particularly preferred.

X is preferably an electron withdrawing group. Preferred electron withdrawing groups are halogen atoms, aliphatic / aryl or heterocyclic sulfonyl groups, aliphatic / aryl or heterocyclic acyl groups, aliphatic / aryl or heterocyclic oxycarbonyl groups, carbamoyl groups, sulfamoyl groups, More preferred are a halogen atom and a carbamoyl group, and particularly preferred is a bromine atom.
Z ₁ and Z ₂ are preferably a bromine atom or an iodine atom, and more preferably a bromine atom.

Y preferably represents -C (= O) -, - SO -, - SO 2 -, - C (= O) N (R) -, or _-SO 2 N (R) -, more preferably -C (═O) —, —SO ₂ —, or —C (═O) N (R) —, particularly preferably —SO ₂ —, —C (═O) N (R) —.
R here represents a hydrogen atom, an aryl group or an alkyl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.
n represents 0 or 1, and is preferably 1.

In general formula (H), when Q is an alkyl group, preferred Y is —C (═O) N (R) —, and when Q is an aryl group or a heterocyclic group, preferred Y is —SO ₂ —. is there.
In the general formula (H), a form in which residues obtained by removing a hydrogen atom from the compound are bonded to each other (generally referred to as a bis type, a tris type, or a tetrakis type) can also be preferably used.
In the general formula (H), a dissociable group (for example, a COOH group or a salt thereof, a SO ₃ H group or a salt thereof, a PO ₃ H group or a salt thereof), a group containing a quaternary nitrogen cation (for example, an ammonium group or a pyridinium group) Etc.), those having a polyethyleneoxy group, a hydroxyl group or the like as a substituent are also preferred forms.

  Specific examples of the compound of the general formula (H) of the present invention are shown below.

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

The compound represented by the general formula (H) of the present invention is preferably used in the range of 10 ⁻⁴ mol to 1 mol, more preferably 10 ⁻³ mol, per mol of the non-photosensitive silver salt of the image forming layer. It is preferable to use in the range of ˜0.5 mol, more preferably in the range of 1 × 10 ⁻² mol to 0.2 mol.
In the present invention, examples of the method for incorporating the antifoggant into the photothermographic material include the methods described in the method for containing a reducing agent, and the organic polyhalogen compound is also preferably added as a solid fine particle dispersion.

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

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

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used to control development by suppressing or accelerating development, to improve spectral sensitization efficiency, and to improve storage stability before and after development. And thione compounds, paragraphs 0067 to 0069 of JP-A-10-62899, compounds represented by formula (I) of JP-A-10-186572, and specific examples thereof include paragraph numbers 0033 to 0052. , European Patent Publication No. 0803764A1, page 20, lines 36-56. Of these, mercapto-substituted heteroaromatic compounds described in JP-A-9-297367, JP-A-9-304875, JP-A-2001-100388, JP-A-2002-303955, JP-A-2002-303951, and the like are preferable.

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

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

4) Dye, Pigment The image-forming layer of the present invention has various dyes and pigments (for example, CI Pigment Blue 60, CI) from the viewpoints of color tone improvement, prevention of interference fringes during laser exposure, and prevention of irradiation. Pigment Blue 64, CI Pigment Blue 15: 6) can be used. These are described in detail in WO98 / 36322, JP-A-10-268465, JP-A-11-338098 and the like. Moreover, it is preferable to use together the water-insoluble azomethine dye represented by the general formulas (I) to (IV) described in Japanese Patent Application No. 2005-049888.

5) Nucleating Agent In the photothermographic material of the invention, it is preferable to add a nucleating agent to the image forming layer. Regarding the nucleating agent and its addition method and addition amount, paragraphs No. 0118 of JP-A No. 11-65021, paragraph Nos. 0136 to 0193 of JP-A No. 11-223898, and formulas (H of JP-A No. 2000-284399) ), Formulas (1) to (3), compounds of formulas (A) and (B), compounds of general formulas (III) to (V) described in Japanese Patent Application No. 11-91652 (specific compounds: 21 to 24) and the nucleation promoter are described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

In order to use formic acid or formate as a strong fogging substance, it is preferably contained at 5 mmol or less, more preferably 1 mmol or less, per mol of silver on the side having the image forming layer containing photosensitive silver halide.
When a nucleating agent is used in the photothermographic material of the invention, it is preferable to use an acid formed by hydrating diphosphorus pentoxide or a salt thereof in combination. Acids or salts thereof formed by hydration of diphosphorus pentoxide include metaphosphoric acid (salt), pyrophosphoric acid (salt), orthophosphoric acid (salt), triphosphoric acid (salt), tetraphosphoric acid (salt), and Examples include hexametaphosphoric acid (salt). Examples of the acid or salt thereof formed by hydrating diphosphorus pentoxide particularly preferably include orthophosphoric acid (salt) and hexametaphosphoric acid (salt). Specific examples of the salt include sodium orthophosphate, sodium dihydrogen orthophosphate, sodium hexametaphosphate, and ammonium hexametaphosphate.
The amount of acid or salt thereof formed by hydration of diphosphorus pentoxide (the coating amount per 1 m ^{2 of} photosensitive material) may be a desired amount according to the performance such as sensitivity and fogging, but is 0.1 mg / m ^2. preferably ^{~500mg / m 2, 0.5mg / m} 2 ~100mg / m 2 is more preferable.

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

(Layer structure and components)
The photothermographic material of the present invention can have a non-photosensitive layer in addition to the image forming layer. The non-photosensitive layer includes (a) a surface protective layer provided on the image forming layer (on the side farther than the support), (b) between the plurality of image forming layers and between the image forming layer and the protective layer. It can be classified into an intermediate layer provided therebetween, (c) an undercoat layer provided between the image forming layer and the support, and (d) a back layer provided on the opposite side of the image forming layer.

  The optical filter layer is provided as the layer (a) or (b). The antihalation layer is provided in the photothermographic material as the layer (c) or (d).

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

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

2) Matting Agent In the present invention, it is preferable to add a matting agent for improving transportability. The matting agent is described in paragraph Nos. 0126 to 0127 of JP-A No. 11-65021. Matting agent case shown in the coating amount per photothermographic material 1 m ^2, preferably from ^{1mg / m 2 ~400mg / m 2} , more preferably ^{5mg / m 2 ~300mg / m 2} .

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

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

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

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

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

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

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

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

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

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

In the present invention, it is preferable to use a fluorosurfactant. Specific examples of the fluorosurfactant include compounds described in JP-A Nos. 10-197985, 2000-19680, 2000-214554 and the like. Further, a polymeric fluorine-based surfactant described in JP-A-9-281636 is also preferably used.
In the photothermographic material of the present invention, it is preferable to use fluorine-based surfactants described in JP-A Nos. 2002-82411, 2003-57780, and 2001-264110. In particular, the fluorosurfactants described in JP-A-2003-57780 and JP-A-2001-264110 are preferable in terms of charge adjustment ability, stability of the coated surface, and smoothness when coating and production is performed with an aqueous coating solution. The fluorine-based surfactant described in JP-A No. 2001-264110 is most preferable because it has a high charge adjusting ability and requires a small amount of use.

In the present invention, the fluorosurfactant can be used on either the image forming layer surface or the back surface, and is preferably used on both surfaces. Further, it is particularly preferable to use in combination with a conductive layer containing the above-described metal oxide. In this case, sufficient performance can be obtained even if the amount of the fluorosurfactant used on the surface having the conductive layer is reduced or removed.
The preferred amount of the fluorocarbon surfactant is an image forming layer side, the range to the back surface each ^{0.1mg / m 2 ~100mg / m 2} , more preferably 0.3mg ^{/ m 2} ~30mg ^/ m 2 range, even more preferably from ^{1mg / m 2 ~10mg / m 2} . In particular JP fluorocarbon surfactant described in JP-A No. 2001-264110 is ^effective, and preferably in the range of ^{0.01mg / m 2 ~10mg / m 2} , more in the range of 0.1mg / ^{m 2} ~5mg / m 2 preferable.

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

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

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

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

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

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

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

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

  In order to stably and continuously produce the photothermographic material of the present invention, the production methods described in JP-A Nos. 2002-156728 and 2002-182333 are preferably used.

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

12) Other usable techniques Examples of the technique that can be used for the photothermographic material of the present invention include EP80364A1, EP883022A1, WO98 / 36322, JP-A-56-62648, 58-62644, JP-A-5-62644. 9-43766, 9-281737, 9-297367, 9-304869, 9-31405, 9-329865, 10-10669, 10-62899, 10-69023 10-186568, 10-90823, 10-171663, 10-186565, 10-186567, 10-186567 to 10-186572, 10-197974, Nos. 10-197982, 10-197983, 10-197985 to 1 No. 0-197987, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10-307365, No. 10- No. 312038, No. 10-339934, No. 11-7100, No. 11-15105, No. 11-24200, No. 11-24201, No. 11-30832, No. 11-84574, No. 11-65021 11-109547, 11-125880, 11-129629, 11-133536 to 11-133539, 11-133542, 11-133543, 11-223898, 11-352627, 11-305377, 11-305378, 11-305 84, 11-305380, 11-316435, 11-327076, 11-338096, 11-338098, 11-338099, 11-343420, JP 2000-187298 , 2000-10229, 2000-47345, 2000-206642, 2000-98530, 2000-98531, 2000-112059, 2000-112060, 2000-112104, Examples thereof include 2000-112064 and 2000-171936.

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

2) Photothermographic development The photothermographic material of the present invention may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. A preferred development temperature is 80 ° C to 250 ° C, preferably 100 ° C to 140 ° C, and more preferably 110 ° C to 130 ° C. The development time is preferably 1 second to 60 seconds, more preferably 3 seconds to 30 seconds, and even more preferably 5 seconds to 25 seconds.

Either a drum type heater or a plate type heater may be used as the thermal development method, but the plate type heater method is more preferable. The heat development method using the plate type heater method is preferably a method described in JP-A-11-133572, and a visible image is obtained by bringing a photothermographic material having a latent image formed thereon into contact with a heating means in a heat developing unit. In the heat development apparatus, the heating unit includes a plate heater, and a plurality of press rollers are disposed to face each other along one surface of the plate heater, and the press roller is disposed between the press roller and the plate heater. A heat development apparatus characterized in that heat development is performed by passing a photothermographic material. It is preferable to divide the plate heater into 2 to 6 stages and lower the temperature about 1 ° C. to 10 ° C. at the tip. For example, there are examples in which four sets of plate heaters that can be independently controlled are used and controlled so as to be 112 ° C., 119 ° C., 121 ° C., and 120 ° C., respectively.
Such a method is also described in JP-A-54-30032, which can exclude moisture and organic solvents contained in the photothermographic material out of the system, and rapidly develop the photothermographic material. It is also possible to suppress a change in the shape of the support of the photothermographic material due to the heating.

  In order to reduce the size of the heat developing machine and shorten the heat development time, it is preferable to be able to control the heater more stably. In addition, the exposure of one sheet of photosensitive material is started from the top and the exposure is finished to the rear end. It is desirable to start the heat development before the time. Imagers capable of rapid processing preferable for the present invention are described in, for example, JP-A Nos. 2002-289804 and 091114.

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

(Use of the present invention)
The photothermographic material of the present invention forms a black and white image by a silver image, and is preferably used as a photothermographic material for medical diagnosis use, printing plate making use, microphotographic use, industrial use and the like.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
Example 1.
1. 1. Production of PET support and undercoat 1-1. Film Formation Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured at 25 ° C. in phenol / tetrachloroethane = 6/4 (mass ratio)) was obtained according to a conventional method. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., and 0.04% by mass of dye BB having the following structure was contained. Thereafter, the film was extruded from a T-die and quenched to prepare an unstretched film having a thickness such that the film thickness after heat setting was 175 μm.

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

1-2. Surface Corona Treatment Both surfaces of the support were treated at room temperature at 20 m / min using a solid state corona treatment machine 6KVA model manufactured by Pillar. From the current and voltage readings at this time, it was found that the support was processed at 0.375 kV · A · min / m ² . The treatment frequency at this time was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.
1-3. Undercoat <Preparation of undercoat layer coating solution>
《For back layer 1st layer》
Latex (solid content 30% by mass) 20g
(Styrene / n-butyl acrylate / t-butyl acrylate / hydroxymethyl methacrylate = 27/10/35/28 (monomer mass ratio%))
Colloidal silica (solid content 10% by mass) 91g
10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
Distilled water 880mL

<< For back side 2nd layer >>
Aqueous polyurethane (Daiichi Kogyo Seiyaku Superflex 820) 215g
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion)
84g
Matting agent (MP-1000, manufactured by Soken Chemical Co., Ltd.) 0.01g
10 mL of 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
Proxel (ICI) 1mL
690 mL of distilled water

<< For image formation layer surface first layer >>
Latex (solid content 30% by mass) (types shown in Tables 1 and 2) 20 g
Colloidal silica (solid content 10% by mass) 91g
10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
Distilled water 880mL

<< For image forming layer surface side second layer >>
Polymer aqueous solution (solid content 18% by mass) (types shown in Tables 1 and 2) 215 g
Matting agent (MP-1000, manufactured by Soken Chemical Co., Ltd.) 0.01g
10 mL of 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
Proxel (ICI) 1mL
774 mL of distilled water

  The polymer latex having a crosslinking group used for the first layer of the image forming layer surface and the modified aqueous polyester used for the second layer of the image forming layer surface side are prepared by the synthesis means described in Japanese Patent Application Laid-Open No. 2004-347664. did.

<Undercoat>
After the corona discharge treatment is performed on both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm, the first layer undercoat coating composition for the image forming layer surface is coated on the one surface with a wire bar with a wet coating amount of 6. the coating is a 6 mL / m 2 ^(per one side), 180 and further applying a second layer undercoating liquid formulation for the image forming layer surface, as the amount of wet coating with a wire bar is 7.7 mL / m ² Dry at 5 ° C. for 5 minutes. Next, this back surface first layer undercoat coating liquid formulation was applied with a wire bar so that the wet coating amount was 5.7 mL / m ² , dried at 180 ° C. for 5 minutes, and further the second back surface second coating. The undercoat coating solution formulation was applied with a wire bar so that the wet coating amount was 7.7 mL / m ² and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

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

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

3. 3. Image forming layer, intermediate layer, and surface protective layer 3-1. Preparation of coating materials

1) Preparation water 5429mL of silver halide emulsions, phthalated gelatin 88.3 g, PAO compound _{(HO (CH 2 CH 2 O} ) n- (CH (CH 3) CH 2 O) 17 - (CH 2 CH 2 O ) M-H; m + n = 5-7) 10 mass% methanol aqueous solution 10 mL, potassium bromide 0.32 g was added and dissolved, and kept at 40 ° C., 0.67 mol / L silver nitrate aqueous solution 659 mL and 0 per liter The solution in which 703 mol of KBr and 0.013 mol of KI were dissolved was mixed for 4 minutes 45 by the simultaneous mixing method using a mixing stirrer shown in Japanese Patent Publication Nos. 58-58288 and 58-58289 while controlling to pAg 8.09. Nucleation was performed by adding in seconds. After 1 minute, 20 mL of 0.63 N potassium hydroxide solution was added. After 6 minutes, 1976 mL of 0.67 mol / L silver nitrate aqueous solution and a solution in which 0.657 mol KBr, 0.013 mol potassium iodide and 30 μmol dipotassium hexachloroiridate were dissolved at a temperature of 40 ° C. While controlling to pAg 8.09, it was added over 14 minutes and 15 seconds by the simultaneous mixing method. After stirring for 5 minutes, the temperature was lowered to 38 ° C.

To this, 18 mL of a 56% by mass acetic acid aqueous solution was added to precipitate the silver halide emulsion. The supernatant was removed leaving 2 L of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was precipitated again. Further, 1.5 L of the sedimented portion was left, the supernatant was removed, 10 L was further added, and after stirring, the silver halide emulsion was sedimented. After leaving the sedimented portion 1.5L and removing the supernatant, a solution of 1.72 g of anhydrous sodium carbonate dissolved in 151 mL of water was added, and the temperature was raised to 55 ° C. The mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.0, and water was added to 1161 g per 1 mol of silver.
This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 40 nm, a grain size variation coefficient of 12%, a [100] face ratio of 92% and a silver iodide content of 2 mol%.

2) Preparation of powdered organic silver salt After adding 0.3776 mol of behenic acid, 0.2266 mol of arachidic acid and 0.1510 mol of stearic acid to 4720 mL of pure water and dissolving at 80 ° C., 1.5N aqueous sodium hydroxide solution 540.2 mL was added, 6.9 mL of concentrated nitric acid was added, and then cooled to 55 ° C. to obtain an organic acid sodium solution. While maintaining the temperature of the organic acid sodium solution at 55 ° C., 45.3 g of the silver halide emulsion and 450 mL of pure water were added, and 13200 rpm (mechanical vibration) was obtained using a homogenizer (ULTRA-TURRAX-25-25) manufactured by IKA JAPAN. The mixture was stirred at a frequency of 21.1 KHz for 5 minutes. Next, 702.6 mL of a 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an organic silver salt dispersion. Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage are repeated until the electrical conductivity of the drainage reaches 2 μS / cm, and after centrifugal dehydration, circulation is performed with hot air with an oxygen partial pressure capacity of 10% at 40 ° C. until there is no mass loss. Drying was performed with a drier to obtain a powdered organic silver salt containing photosensitive silver halide.

3-2. Preparation of image forming layer coating liquid 1) Preparation of image forming layer coating liquid 1 14.57 g of polyvinyl butyral powder (Monsant Butvar B-79) was dissolved in 1457 g of methyl ethyl ketone (MEK), and dissolver DISPERMAT CA- manufactured by VMA-GETZMANN. While stirring in a 40M type, 500 g of the above powdered organic silver salt was gradually added and mixed well to obtain a slurry.

A photosensitive emulsion dispersion was prepared by dispersing the slurry in two passes with a GM-2 pressure homogenizer manufactured by SMT. At this time, the processing pressure during one pass was 280 kg / cm ² , and the processing pressure during two passes was 560 kg / cm ² .

  To 50 g of the obtained organic silver salt dispersion, 15.1 g of MEK was added, and the mixture was kept at 21 ° C. while stirring at 1000 rpm with a dissolver type homogenizer. 390 μL of a 10 wt% methanol solution of the aggregate was added and mixed with stirring. Further, 494 μL of a 10% by mass methanol solution of calcium bromide was added and stirred for 20 minutes.

  Subsequently, 167 mg of a methanol solution containing 15.9% by mass of dibenzo-18-crown-6 and 4.9% by mass of potassium acetate was added and stirred for 10 minutes, and then 18.3% by mass of 2-chlorobenzoic acid. 34.2% by weight of salicylic acid-p-toluenesulfonate, sensitizing dye no. 2.6 g of 41 (0.24 mass% MEK solution) was added and stirred for 1 hour. Thereafter, the temperature was lowered to 13 ° C., and the mixture was further stirred for 30 minutes. While maintaining the temperature at 13 ° C., 13.31 g of polyvinyl butyral (Monsant Butvar B-79) was added and stirred for 30 minutes, and then 1.08 g of a 9.4 mass% tetrachlorophthalic acid solution was added for 15 minutes. Stir. While continuing stirring, 0.4 mol of reducing agent-1 was added per mol of silver.

  12.4 g of MEK solution of 1.1% by weight of 4-methylphthalic acid and dye 1 are added, followed by 1.5 g of 10% by weight of Desmodur N3300 (Mobay aliphatic isocyanate), and 7.4% by weight. 13.7 g of a MEK solution of Polyhalogen Compound-1 and 4.27 g of a 7.2% by mass fratazine MEK solution were added.

2) Preparation of image forming layer coating solutions 2 to 6 In place of polyvinyl butyral (Monsant Butvar B-79) used in the preparation of image forming layer coating solution 1, a modification having an α-olefin unit shown in (Table 3) below A polyvinyl acetal resin was used. These were synthesized by the method described in JP-A-2006-17877.

3-3. Preparation of surface protective layer coating solution While stirring MEK865g, cellulose acetate butyrate (Eastman Chemical Co., CAB171-15) 96g, polymethylmethacrylic acid (Rohm & Haas Co., Paraloid A-21) 4.5g, 1, 3 -After adding 1.5 g of di (vinylsulfonyl) -2-propanol, 1.0 g of benzotriazole, and 1.0 g of a fluorine-based activator (Asahi Glass Co., Surflon KH40), 13 and 6% by mass of cellulose acetate butyrate Dispersed rate (Eastman Chemical Co., CAB171-15) and 9% by mass of calcium carbonate (Speciality Minerals, Super-Pflex 200) in MEK with a dissolver type homogenizer at 8000 rpm for 30 minutes 30 g Was added and stirred to prepare a surface protective layer coating solution.

3-4. Preparation of photothermographic material The image development layer coating solution and the surface protective layer coating fatigue are extruded, and the photothermographic material is coated on the surface opposite to the back layer of the support on which the back layer is coated by simultaneous multilayer coating. Produced.
The coating was carried out so that the image forming layer had a coating silver amount of 1.9 g / m ² and the surface protective layer had a dry film thickness of 2.5 μm. Then, it dried for 10 minutes using the drying air with a drying temperature of 75 degreeC and a dew point temperature of 10 degreeC.

  The compounds used in the examples are shown below.

4). Performance evaluation 4-1. Image exposure and thermal development treatment An exposure machine using a semiconductor laser having a high frequency mass and a wavelength of 800 nm to 820 nm as a multi-mode semiconductor laser as an exposure source was fabricated, and from the image forming layer surface side of the prepared sample, the exposure machine Exposure by laser scanning was given. At this time, an image was recorded by setting the incident angle of the scanning laser beam to the exposed surface of the photothermographic material at 75 degrees. Thereafter, the film was thermally developed at 124 ° C. for 15 seconds using an automatic developing machine having a heat drum so that the protective layer of the photothermographic material was in contact with the drum surface, and the resulting image density was measured with a densitometer. At that time, the exposed and developed room was 23 ° C. and 50% RH.

4-2. Evaluation item (cover)
The density of the unexposed area was fogged, and sample No. It was expressed as a relative value to 1.
(sensitivity)
The sensitivity of the logarithm of the reciprocal of the exposure amount giving fog + density 1.0 is taken as the sample number. 1 and relative sensitivity (S _1.0 ).
(Raw storage stability)
Each sample was forcibly stored in a dark place at 30 ° C. and 70% RH for 7 days, and then subjected to the above image exposure and heat development treatment. The difference from the fog and sensitivity before each forced storage was determined as follows: Δfog, ΔS _1.0 . The value of each sample is assigned to sample Expressed as a relative value to the value of 1, it was used as a measure of raw storage stability. It represents that it is excellent in storage stability, so that this value is small.
△ fog = fog (after forced storage)-fog (before forced storage)
ΔS _1.0 = S _1.0 (after forced storage) − S _1.0 (before forced storage)

(Image storage stability)
Next, CR lung field images and MR tomographic images were output and two practical images processed under standard development conditions were prepared, one of which was stored in a refrigerated dark place, the other being 30 ° C. 70 RH, 1000 LUX. Stored in light for 3 days.
The refrigerated dark storage sample of each sample was compared with the above-mentioned bright storage sample, and the sensory evaluation was visually performed with a charkasten. Evaluation is made by 10 observers. When 9 or more people judge that no change in color tone is recognized, ◎, when 7-8 people judge that no change in color tone is found, ○, 4-6 people show the color tone When it was judged that no change was observed, Δ, and when there were 3 or less people judged that no change in color tone was observed, it was marked with ×.

4-3. Evaluation results The results obtained are shown in Table 4.

From Table 4, it is clear that the sample of the present invention has excellent performance.
In particular, α-olefin-modified polyvinyl acetal resin is used in the image forming layer, and a modified latex having a monomer having two or more cross-linking groups as a constituent component is used in the undercoat layer in combination with raw storage stability and image storage stability. Excellent performance was obtained. Furthermore, by combining an aqueous polyester having a crosslinkable group, the most excellent performance in raw storage stability and image storage stability was obtained.

Example 2
1) Preparation of Image Forming Layer Coating Liquid 21 In the same manner as in Example 1, 15.1 g of MEK was added to 50 g of the organic silver salt dispersion while stirring under a nitrogen stream, and the temperature was kept at 24 ° C. 2.5 mL of a 10 mass% methanol solution of the following antifoggant 1 was added and stirred for 15 minutes. Sensitizing dye no. 5 (0.24 mass% MEK solution) 2.5 g, 1.8 mL of a solution in which the dye adsorption assistant is 20 mass% in a 1: 5 mass mixture ratio of the following dye adsorption assistant and potassium acetate, 15 Stir for minutes. Next, a mixed solution of 4-chloro-2-benzoylbenzoic acid and a supersensitizer 5-methyl-2-mercaptobenzimidazole (mixing ratio = 25 by mass, total 3.0 mass% methanol solution). 7 mL and 3.5 × 10 ⁻³ mol of polyhalogen compound-1 and 0.4 mol of reducing agent-1 per mol of silver were added and stirred for 1 hour, and then the temperature was lowered to 13 ° C. for another 30 minutes. Stir. While maintaining at 13 ° C., 48 g of polyvinyl butyral was added and dissolved sufficiently, and then the following additives were added. All these operations were performed under a nitrogen stream.

Phthalazine 1.5g
Tetrachlorophthalic acid 0.5g
4-methylphthalic acid 0.5g
Hydrogen bonding compound-1 0.67g
Development accelerator-1 0.046g
Development accelerator-2 0.039g
Dye 2 2.0g
Desmodur N3300 (Mobay, aliphatic isocyanate) 1.10 g

2) Preparation of Image Forming Layer Coating Solution 22-30 Modified with the same α-olefin unit as in Example 1 instead of polyvinyl butyral (Monsant Butvar B-79) used in the preparation of image forming layer coating solution 21 Polyvinyl acetal resin was used (shown in Table 5).

3) Coating Image forming layer: On the surface opposite to the back layer of the support on which the same back layer as the support in Example 1 was coated, the above image forming layer coating solution was coated with a silver amount of 1.8 g / m. ^{2. It} was applied so that the polyvinyl butyral binder was 8.5 g / m ² .

  Surface protective layer: The following coating solution was applied so that the wet coating thickness was 100 μm.

175 mL of acetone
2-propanol 40mL
Methanol 15mL
Cellulose acetate 8g
Phthalazine 1.5g
4-Methylphthalazine 0.72g
Tetrachlorophthalic acid 0.22g
Tetrachlorophthalic anhydride 0.5g
Silica (average particle size 4 μm, coefficient of variation 20%) (1% by mass with respect to binder)
Fluoroactive agent (Asahi Glass Co., Surflon KH40) 0.5g

4) Exposure, heat development treatment, and performance evaluation The same procedure as in Example 1 was performed.
The obtained results are shown in 5.

From Table 6, it is clear that the sample of the present invention has excellent performance.
In particular, α-olefin-modified polyvinyl acetal resin is used in the image forming layer, and a modified latex having a monomer having two or more cross-linking groups as a constituent component is used in the undercoat layer in combination with raw storage stability and image storage stability. Excellent performance was obtained. Furthermore, by combining an aqueous polyester having a crosslinkable group, the most excellent performance in raw storage stability and image storage stability was obtained.

Example 3
The sensitizing dye No. 1 of Example 1 was used. 41 in No. 41. A sample was prepared in the same manner as in Example 1 except that it was changed to 20, and the performance was evaluated in the same manner. As a result, the sample of the present invention showed excellent results as in Example 1.

Example 4
The sensitizing dye No. 2 of Example 2 was used. No. 5 A sample was prepared in the same manner as in Example 2 except that the sample was changed to 54, and the performance was evaluated in the same manner. As a result, similar to Example 2, the sample of the present invention showed excellent results.

Example 5
In Example 1, the sample was prepared in the same manner as in Example 1 except that the first layer and the second layer of the undercoat layer on the back surface were changed to the first coat layer and the second layer on the image forming layer surface side according to the present invention. It produced and evaluated the performance similarly. As a result, both the raw storage stability and the image storage stability of the photothermographic material were further improved by making the undercoat layer of the back surface an undercoat layer of the composition according to the present invention.

Claims (7)

  A photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for heat development, and a binder on at least one surface of a support, 50% by mass or more of the binder is a modified polyvinyl acetal resin containing 1 mol% to 20 mol% of α-olefin units in the main chain, and has a crosslinkable group between the support and the image forming layer. A photothermographic material having an undercoat layer containing a polymer latex.   The modified polyvinyl acetal resin has a residual acetyl group amount of 25 mol% or less, a residual hydroxyl group amount of 17 mol% or more and 35 mol% or less, and a weight average degree of polymerization of 200 or more and 3000 or less. 2. The photothermographic material according to 1.   3. The photothermographic material according to claim 1, wherein the modified polyvinyl acetal resin is a modified polyvinyl butyral resin.   4. The photothermographic material according to claim 1, wherein the polymer latex is a polymer latex having at least two crosslinkable groups in a monomer unit.   The second undercoat layer containing an aqueous polyester having a crosslinkable group is provided between the undercoat layer containing the polymer latex having the crosslinkable group and the image forming layer. Item 5. The photothermographic material according to any one of Items 4 above.   The heat according to any one of claims 1 to 5, wherein the crosslinkable group of the polymer latex is at least one selected from an epoxy group, an active methylene group, an isocyanate group, and an oxazoline group. Development photosensitive material.   The photothermographic material according to claim 1, wherein the α-olefin is ethylene.