JP2005146064A - Dispersion of microcapsuled dye dispersion, its manufacturing process, and photosensitive material for thermal development photography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish a technology to disperse an organic solvent-soluble dye in an organic solvent by microcapsuling the dye and improve the sensitivity, clarity and remaining color by applying the technology to photosensitive materials for thermal development photography. <P>SOLUTION: The manufacturing process for the microcasuled dye dispersion comprises dissolving a dye and a binder in an organic solvent, dispersing the solution in an aqueous solution containing a water-soluble resin, evaporating the organic solvent to form a film on the wall (shell), evaporating the water to dryness and dispersing the microcapsules obtained in an organic solvent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dye microcapsule dispersion in which a dye dissolved in an organic solvent is microencapsulated and dispersed in an organic solvent, and a method for producing the same, and further, a photothermographic photograph containing the dye microcapsule dispersion in any layer. The present invention relates to a photosensitive material.

  In general, when a dye is used in a light-sensitive material, it is dissolved in an organic solvent, mixed with at least a binder and coated to form a layer. However, since the dye dissolves in the organic solvent, the coating liquid containing the organic solvent is applied on the layer coated with the dye to form another layer, or two or more layers are formed at once. Then, there existed a problem that dye will move between layers.

  In order to solve the problem of dye transfer between layers, studies have been made in the field of silver halide photographic light-sensitive materials (hereinafter referred to as conventional light-sensitive materials) that output images by wet development.

  That is, in conventional photosensitive materials, a number of technical developments have been made to color photographic emulsion layers and other hydrophilic colloid layers for the purpose of absorbing light in a specific wavelength range. For example, incident light is transmitted through the photographic emulsion layer, or light scattered after transmission is reflected at the interface between the emulsion layer and the support, or the surface of the conventional photosensitive material opposite to the emulsion layer across the support. One side of the technique is to provide a colored layer to prevent blurring of the image, that is, to prevent halation, or to an X-ray conventional photosensitive material having emulsion layers on both sides. In other words, a technique for providing a colored layer in order to prevent deterioration of sharpness due to so-called crossover light in which light emitted from the intensifying screen reaches the emulsion surface on the opposite side.

  In such a technique, the hydrophilic colloid layer is colored with a dye. This dye has spectral absorption according to the purpose of use, is inactive with respect to the silver halide emulsion, and is decolorized in the development processing step. In addition, it has performances such as not contaminating the processing solution and excellent stability over time. Among these, since the dye has an absorption that overlaps with the intrinsic absorption region of the silver halide emulsion, a performance that does not affect the sensitivity of the silver halide is required. As one of the techniques, a technique in which a dye is solid-dispersed and fixed in a dye-containing layer to avoid the coexistence of the dye and a silver halide emulsion has been extensively studied and put into practical use in the field of conventional photosensitive materials.

  However, from the viewpoints of workability, environmental protection, and space saving, the waste liquid from wet processing of conventional photosensitive materials can be efficiently exposed with a laser imager or laser image setter in recent years and developed with high sensitivity. The technology relating to the heat-developable photographic light-sensitive material excellent in the storage stability of the silver image and the running characteristics at the time of heat development was reviewed and advanced rapidly.

  Such techniques include U.S. Pat. Nos. 3,152,904, 3,487,075 and D.C. Morgan, “Dry Silver Photographic Materials” (Handbook of Imaging Materials, Marcel Dekker, Inc., page 48, 1991), etc. Photothermographic materials containing photosensitive silver halide grains and a reducing agent are known. These heat-developable photographic light-sensitive materials can provide the user with an image forming system that does not generate waste liquid.

  Such a photothermographic material is exposed to a laser to expose silver halide grains. However, since the refractive index is different between the photosensitive layer and the plastic film as the support, at the interface between the support and the photosensitive layer, A part of the incident laser beam is reflected, or the laser beam that has passed through is further reflected by the support and back layer, the back layer and air, the machine cover, etc. There is a problem similar to that of the conventional photosensitive material as described above in which the unexposed part is exposed to light and the sharpness of the image is deteriorated. However, the dye that absorbs laser light, the so-called antihalation dye, is most effective in the layer immediately below the photosensitive layer in view of its function. However, the antihalation dye is added to methyl ethyl ketone, which is the coating solvent for the photothermographic material. Because it melts, it cannot be fixed to the desired layer, and the photosensitive layer oozes out when it is applied simultaneously or sequentially, and the silver halide and the incident light are held together, so the sensitivity becomes low. There was a problem.

  In short, there has been a demand for a technique capable of fixing a dye to a layer when applied with a solvent. On the other hand, techniques (for example, refer to Patent Documents 1 and 2) intended to prevent halation by laser light using a dye that is soluble in an organic solvent have been disclosed, but the above-mentioned problems have been sufficiently overcome. It's hard to say.

In addition, in order to achieve this immobilization, a person skilled in the art has studied to microencapsulate the dye, but immobilization of the dye to a specific layer by microencapsulation has not been successful.
JP-A-8-201959 JP 2001-83655 A

  Accordingly, the present invention has been made in view of the above circumstances, and is to establish a technique for microencapsulating a dye dissolved in an organic solvent and dispersing it in the organic solvent. This technique is applied to a photothermographic material. Application is to improve sensitivity, sharpness, and residual color.

The above object of the present invention has been achieved by the following constitution.
(Claim 1)
A micro-particle obtained by dissolving a dye and a binder in an organic solvent and dispersing it in an aqueous solution containing a water-soluble resin, evaporating the organic solvent to form a wall film (shell), and evaporating and drying the water. A method for producing a dye microcapsule dispersion comprising dispersing capsules in an organic solvent.
(Claim 2)
Dissolve the dye and binder in an organic solvent and disperse it in an aqueous solution containing a water-soluble resin, then evaporate the organic solvent to form a wall film (shell), add colloidal silica, and evaporate the water. A method for producing a dye microcapsule dispersion, characterized in that microcapsules obtained by drying are dispersed in an organic solvent.
(Claim 3)
3. The dye microcapsule dispersion according to claim 1, wherein when the dye and the binder are dissolved in the organic solvent and dispersed in an aqueous solution containing a water-soluble resin, ultrasonic dispersion is performed at a frequency of 19 to 22 kHz. Manufacturing method.
(Claim 4)
The method for producing a dye microcapsule dispersion according to claim 2 or 3, wherein the concentration of the salt contained in the colloidal silica is 1 ppm or less based on the solid content of the colloidal silica.
(Claim 5)
After forming the said wall film (shell), the compound which reacts with the hydrophilic group of water-soluble resin is added, The manufacturing of the dye microcapsule dispersion of any one of Claims 1-4 characterized by the above-mentioned. Method.
(Claim 6)
The dye microcapsule dispersion according to claim 5, wherein a compound that reacts with the hydrophilic group of the water-soluble resin is added so as to have a solid content concentration of 5 to 20% of the aqueous dispersion of the dye microcapsule. Manufacturing method.
(Claim 7)
The method for producing a dye microcapsule dispersion according to any one of claims 1 to 6, wherein the water-soluble resin is gelatin and gum arabic.
(Claim 8)
The method for producing a dye microcapsule dispersion according to any one of claims 1 to 6, wherein the water-soluble resin is gelatin.
(Claim 9)
A dye microcapsule dispersion produced by the method for producing a dye microcapsule dispersion according to any one of claims 1 to 8.
(Claim 10)
The dye microcapsule dispersion according to claim 9, wherein an average particle diameter of the dye microcapsules in the dye microcapsule dispersion is 100 nm or more and 1 µm or less.
(Claim 11)
A photothermographic material, wherein a coating liquid containing the dye microcapsule dispersion according to claim 9 or 10 is coated on either side of a support to form a layer.
(Claim 12)
12. The photothermographic material according to claim 11, wherein the layer is located between the photosensitive layer and the support or on the opposite side of the photosensitive layer through the support.

  According to the present invention, it is possible to establish a technology for microencapsulating a dye dissolved in an organic solvent and dispersing it in the organic solvent. By applying the technology to a photothermographic material, sensitivity, sharpness, and residual color properties are established. Could be improved.

  Hereinafter, the present invention will be described in detail.

  First, the dye microcapsule of the present invention will be described.

  The microcapsule of the present invention means “a fine container”, and is a generic name for those having a diameter in the nanometer region to a millimeter region (not necessarily referring to a container in the micrometer region, which is the word source). The microcapsule is composed of a core (core) and a wall film (shell) of the container. In addition, both mononuclear and binuclear cores are microcapsules in the present invention. The core portion of the dye microcapsule contains a dye and a binder. The ratio of the dye and the binder may be arbitrary, but is 0.1 / 99.9 to 99/1.

  As described in JP-A-2001-83655, a filter layer is formed on the same side as or opposite to the photosensitive layer in order to control the amount of light transmitted through the photosensitive layer or the wavelength distribution, or a dye is added to the photosensitive layer. It is included. In the present invention, such a dye is added after being processed (microencapsulated) into a form that does not dissolve in the coating solvent, and known dyes can be used. That is, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the photosensitive material.

  Examples of the dye used in the present invention include the structures shown below.

In the formula, each of Z ¹ and Z ² represents a group of nonmetallic atoms necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring which may be condensed, and R ¹ and R ² are each an alkyl group or an alkenyl group. Or an aralkyl group, R ³ and R ⁵ each represent a hydrogen atom or a group of nonmetallic atoms necessary to form a 5- or 6-membered ring by bonding to each other, R ⁴ represents a hydrogen atom, an alkyl group, a halogen atom, An aryl group, —N (R ⁶ ) R ⁷ , —SR ⁸ or —OR ⁹ ; R ⁶ represents a hydrogen atom, an alkyl group or an aryl group; R ⁷ represents an alkyl group, an aryl group, a sulfonyl group or an acyl group; R ⁸ and R ⁹ each represents an alkyl group or an aryl group, and R ⁶ and R ⁷ may be linked to each other to form a 5- or 6-membered ring. a and b each represents 0 or 1, and X ⁻ represents an anion.

In the general formula (I), the 5- or 6-membered nitrogen-containing heterocyclic ring represented by Z ¹ or Z ² may be an oxazole ring, an isoxazole ring, a benzoxazole ring, a naphthoxazole ring or a thiazole ring. Benzothiazole ring, naphthothiazole ring, indolenine ring, benzoindolenine ring, imidazole ring, benzimidazole ring, naphthimidazole ring, quinoline ring, pyridine ring, pyrrolopyridine ring, fluropyrrole ring and the like. A 5-membered nitrogen-containing heterocyclic ring condensed with a benzene ring or a naphthalene ring is preferred, and an indolenine ring is most preferred. These rings may be substituted. As a substituent, a lower alkyl group (for example, methyl group, ethyl group), an alkoxy group (for example, methoxy group, ethoxy group), a phenoxy group (for example, unsubstituted phenoxy group, p-chlorophenoxy group), a carboxy group , Halogen atoms (Cl, Br, F), alkoxycarbonyl groups (for example, ethoxycarbonyl group), cyano groups, nitro groups, hydroxyl groups, and the like.

The alkyl group represented by R ¹ , R ² , R ⁴ , R ⁸ and R ⁹ is an alkyl group having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group). Group, isobutyl group, pentyl group, hexyl group). Further, it may be substituted with a hydroxyl group, a carboxy group, a halogen atom (Cl, Br) or the like. The alkyl group represented by R ⁶ and R ⁷ is an alkyl group or alkoxycarbonylalkyl group represented by R ¹ , R ² , R ⁴ , R ⁸ and R ⁹ (for example, methoxycarbonylmethyl group, ethoxycarbonylmethyl group). Ethoxycarbonylethyl group). Examples of the 5- or 6-membered ring formed by connecting R ³ and R ⁵ to each other include cyclopentene and cyclohexene, and these rings have substituents (for example, a methyl group, a t-butyl group, and a phenyl group). You may have.

Examples of the halogen atom represented by R ⁴ include F, Cl, and Br. The aryl group represented by R ⁴ , R ⁶ , R ⁷ , R ⁸ and R ⁹ preferably has 6 to 12 carbon atoms, and examples thereof include a phenyl group and naphthyl. The aryl group may be substituted with the substituent described in the substituent that the ring of Z ¹ may have. The aralkyl group represented by R ¹ and R ² is preferably an aralkyl group having 7 to 12 carbon atoms (eg, benzyl group, phenylethyl group), and a substituent (eg, methyl group, alkoxy group, chloro atom). You may have. The alkenyl group represented by R ¹ and R ² is preferably an alkenyl group having 2 to 6 carbon atoms, for example, 2-pentenyl group, vinyl group, allyl group, 2-butenyl group, 1-propenyl. The group can be mentioned. The sulfonyl group represented by R ⁷ is preferably a sulfonyl group having 1 to 10 carbon atoms, and examples thereof include a mesyl group, a tosyl group, a benzenesulfonyl group, and an ethanesulfonyl group. The acyl group represented by R ⁷ is preferably an acyl group having 2 to 10 carbon atoms, and examples thereof include an acetyl group, a propionyl group, and a benzoyl group. R ⁶ and R ⁷ may be connected to each other to form a heterocycle. Examples of the heterocycle include piperidine, morpholine, piperazine and the like, and these rings may have a substituent (for example, methyl group, phenyl group, ethoxycarbonyl group). More preferably, R ¹ and R ² are alkyl groups, R ³ and R ⁴ are linked to form a 5- or 6-membered ring, and R ⁴ is —N (R ⁶ ) R ⁷ . More preferably, at least one of R ⁶ or R ⁷ is a phenyl group.

Examples of the anion represented by X ⁻ include halogen ions (Cl ⁻ , Br ⁻ , I ⁻ ), p-toluenesulfonic acid ions, ethyl sulfate ions, PF ₆ ⁻ , BF ₄ ⁻ , ClO ₄ ^{− and the} like.

  In the present invention, the dye represented by the following general formula (II) is more preferable.

In the formula, Z ³ and Z ⁴ each represent a nonmetallic atom group necessary for forming a benzo or naphtho fused ring, R ¹⁰ and R ¹¹ each represent an alkyl group, an aralkyl group or an alkenyl group, and R ¹² and R ¹⁴ Each represents a hydrogen atom or a group of nonmetallic atoms necessary to form a 5- or 6-membered ring linked to each other, and R ¹³ represents a hydrogen atom, an alkyl group, a halogen atom, an aryl group, —N (R ¹⁹ ) R ²⁰ represents -SR ²¹ or -OR ^22, R ^19, R ^20, R ²¹ and R ²² represent each an alkyl group or an aryl group, may be linked R ¹⁹ and R ²⁰ with each other to form a ring. R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ each represent an alkyl group, and R ¹⁵ and R ¹⁶ or R ¹⁷ and R ¹⁸ may be linked to form a ring. X ⁻ represents an anion.

The general formula (II) will be described in detail. The benzo or naphth fused ring formed by Z ³ and Z ⁴ may be substituted with the substituent described for Z ¹ . The alkyl groups represented by R ¹⁰ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ²¹ and R ²² are R ¹ , R ² , R ⁴ described in the general formula (I). , R ⁸ and R ^{9 have the same} meaning as the alkyl group. R ¹⁵ and R ¹⁶ , R ¹⁷ and R ¹⁸ may be connected to each other to form a ring (eg, a cyclohexane ring). The alkyl group represented by R ¹⁹ and R ²⁰ has the same meaning as the alkyl group in R ⁶ and R ⁷ described in formula (I). The alkenyl group and aralkyl group represented by R ¹⁰ and R ¹¹ are synonymous with the alkenyl group and aralkyl group of R ¹ and R ² . The aryl group represented by R ¹³ , R ¹⁹ , R ²⁰ , R ²¹ and R ²² is synonymous with the aryl group of R ⁴ , R ⁶ , R ⁷ , R ⁸ and R ⁹ in formula (I). The halogen atom of R ^{13 has} the same meaning as the halogen atom of R ⁴ . The ring formation by R ¹⁹ and R ²⁰ is synonymous with the ring formation of R ⁶ and R ⁷ . X ^- represents the general formula (I) X ^- as synonymous. Preferably, R ¹⁰ and R ¹¹ are each an alkyl group, R ¹² and R ¹⁴ are linked to form a 5- or 6-membered ring, and R ¹³ is a compound represented by —N (R ¹⁹ ) R ^20. is there. Particularly preferred is a compound having a phenyl group in at least one of R ^{19 and} R ²⁰ .

  In the present invention, the dye represented by the general formula (III) is particularly preferable.

In the formula, Z ³ and Z ⁴ each represents a nonmetallic atom necessary for forming a benzo or naphtho fused ring, R ¹⁰ and R ¹¹ each represents an alkyl group, an aralkyl group or an alkenyl group, and R ²³ and R ²⁴ represents an alkyl group or an aryl group, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ each represent an alkyl group, and R ¹⁵ and R ¹⁶ or R ¹⁷ and R ¹⁸ may be linked to form a ring. Good. X ⁻ represents an anion.

The general formula (III) will be described in detail. The benzo or naphth fused ring formed by Z ³ and Z ⁴ may be substituted with the substituent described for Z ¹ . The alkyl groups represented by R ¹⁰ , R ¹¹ , R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ are the same as the alkyl groups in R ¹ , R, R ⁴ , R ⁸ and R ⁹ described in formula (I). It is synonymous. R ¹⁵ and R ¹⁶ , R ¹⁷ and R ¹⁸ may be connected to each other to form a ring (eg, a cyclohexane ring). The alkyl group represented by R ²³ and R ²⁴ has the same meaning as the alkyl group in R ⁶ and R ⁷ described in formula (I). The alkenyl group and aralkyl group represented by R ¹⁰ and R ¹¹ are synonymous with the alkenyl group and aralkyl group of R ¹ and R ² . The aryl group represented by R ²³ and R ²⁴ has the same meaning as the aryl group of R ⁶ and R ⁷ in formula (I). Ring formation by R ²³ and R ²⁴ is synonymous with the ring formation of R ⁶ and R ⁷ . X ^- represents the general formula (I) X ^- as synonymous. More preferably, R ¹⁰ and R ¹¹ are each an alkyl group, and R ²³ and R ²⁴ are each a phenyl group. Specific examples of the dye used in the present invention are shown below, but the scope of the present invention is not limited thereto.

  The above dyes can be synthesized with reference to US Pat. No. 3,671,648 and the following synthesis examples.

Synthesis Example (Synthesis of Compound 2)
1,1.4 g of 1,2,3,3-tetramethyl-5-chloroindolenium-p-toluenesulfonate, 7.2 g of N- (2,5-dianilinomethylenecyclopentylidene) -diphenylaluminum perchlorate 100 ml of ethyl alcohol, 6 ml of acetic anhydride, and 12 ml of triethylamine were stirred at an external temperature of 100 ° C. for 1 hour, and the precipitated crystals were separated by filtration. Recrystallization with 100 ml of methyl alcohol gave 7.3 g of compound 2. Melting point: 270 ° C. or higher, λmax: 800.8 nm, ε: 2.14 × 10 ⁵ (chloroform). Other dyes can be synthesized similarly.

  Further, the dye used in the present invention includes a squarylium dye having a thiopyrylium nucleus (referred to as a thiopyrylium squarylium dye), a squarylium dye having a pyrylium nucleus (referred to as a pyrylium squarylium dye), and a thiopyrilium similar to a squarylium dye. Examples thereof include a lithium croconium dye and a pyrylium croconium dye.

  The compound having a squarylium nucleus is a compound having 1-cyclobuten-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy-4 in the molecular structure. , 5-dione-containing compounds. Here, the hydroxyl group may be dissociated. Hereinafter, in the present specification, these pigments are collectively referred to as squarylium dyes for convenience.

  First, the squarylium dye represented by the general formula (1) used in the present invention will be described.

In the general formula (1), R ₁ and R ₂ each represent a monovalent substituent. The monovalent substituent is not particularly limited, but may be an alkyl group (for example, methyl group, ethyl group, isopropyl group, t-butyl group, methoxyethyl group, methoxyethoxyethyl group, 2-ethylhexyl group, 2-hexyldecyl). Group, benzyl group, etc.) and aryl groups (for example, phenyl group, 4-chlorophenyl group, 2,6-dimethylphenyl group, etc.), alkyl groups are more preferred, and t-butyl groups are preferred. It is particularly preferred. R ₁ and R ₂ may form a ring together. m and n each represents an integer of 0 to 4, preferably 2 or less.

  Examples of the dye used in the present invention are shown below.

  About these squarylium dyes, it is compoundable by the method described in Unexamined-Japanese-Patent No. 2000-160042.

  The core-forming binder that can be used in the present invention is a colorless and transparent or translucent natural polymer synthetic resin, polymer and copolymer, and other film-forming media such as cellulose acetate, cellulose acetate butyrate, poly (vinyl chloride) , Copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethanes), phenoxy There are resins, poly (vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, and poly (amides), and it is preferable to use a hydrophobic transparent binder. Preferable binders include polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, polyester, polycarbonate, polyacrylic acid, polyurethane and the like. Among these, polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, and polyester are particularly preferably used.

  Subsequently, components constituting the shell portion of the microcapsule of the present invention will be described.

  A water-soluble resin is used as the binder for the shell portion. The water-soluble resin functions as a protective colloid when the core component is dispersed in water and as a barrier so that the core portion does not dissolve in the organic solvent when dispersed in the organic solvent. Therefore, from this point of view, it is preferable to use polyvinyl alcohol or a derivative thereof, gelatin, or both gelatin and gum arabic, and albumin among water-soluble resins. Among them, gelatin, both gelatin and gum arabic are used. It is preferable.

  The most preferred water-soluble resin of the present invention includes gelatin and gum arabic, and examples of gelatin include lime-processed gelatin, acid-processed gelatin and Bull Society Science Photography Japan (Bull. Soc. Sci. Phot.Japan), No. 16, 30 (1966), an oxygen-treated gelatin may be used, and a hydrolyzate or oxygen-decomposed product of gelatin can also be used. Furthermore, gelatin derivatives and graft polymers of gelatin and other polymers can also be used. A commercially available gum arabic can be used as it is. Further, when gum arabic and gelatin are used in combination, the gelatin is preferably alkali-treated gelatin.

  Such a water-soluble resin has a hydrophilic group in the molecule, and when dispersed in an organic solvent, the dispersion is hindered by water carried by the hydrophilic group, or when the coating is dried. There is a concern that the film may be brushed. Therefore, in this invention, it is preferable to contain the inorganic or organic compound which can react with water-soluble resin. Examples of such compounds include chromium salts, aldehydes (formaldehyde, glutaraldehyde, etc.), N-methylol compounds (dimethylol urea, etc.), active vinyl compounds (1,3,5-triacryloyl-hexahydro-s-). Triazine, bis (vinylsulfonyl) methyl ether, N, N′-methylenebis- [β- (vinylsulfonyl) propionamide] and the like), active halogen compounds (such as 2,4-dichloro-6-hydroxy-s-triazine), Mucohalogen acids (such as mucochloric acid), N-carbamoylpyridinium salts (such as (1-morpholinocarbonyl-3-pyridinio) methanesulfonate), haloamidinium salts (1- (1-chloro-1-pyridinomethylene) pyrrolidinium, 2 -Naphthalenesulfonate In particular, the active vinyl compounds described in JP-B-53-41220, 53-57257, 59-162546, and 60-80846 and U.S. Pat. No. 3,325,287 The active halides described can be used alone or in combination.

  In addition, since the pore diameter of the shell can be reduced by this reaction, it is effective for controlling the release of the dye in the core in the organic solvent. In order to prevent the dye in the core from being released in the organic solvent in the microcapsule having a particle size of submicron order, the water-soluble resin can be used at a concentration (solid content) of 5 to 20% of the microcapsule aqueous dispersion. It is necessary to add an inorganic or organic compound that can react. If this concentration is higher than 20%, the compound reacting with the water-soluble resin itself may cause agglomeration or may react between the capsule particles and agglomerate. Conversely, if the concentration is lower than 5%, the barrier property against the solvent deteriorates. And affects the dispersion state.

  The surface of the shell preferably has colloidal silica having a salt concentration of 1 ppm or less. Of course, the salt concentration may be zero. Colloidal silica usually has a primary particle size as an average particle containing an inorganic alkali component such as sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonia or an organic alkali component such as tetramethylammonium ion as a stabilizer. This refers to an aqueous dispersion of silicon dioxide fine particles having a diameter of 5 nm to several tens of nm. In the present invention, colloidal silica having an alkali component content of 1 ppm or less is preferred from the viewpoint of effects. Since such colloidal silica is not dispersed by an ionic compound, it can be dispersed in either an aqueous solvent or an organic solvent, so that core-shell particles prepared in an aqueous solvent are redispersed in an organic solvent. It plays an important role. Such colloidal silica is commercially available from Fuso Chemical Industry Co., Ltd. under trade names such as PL-1, PL-2, and PL-3, and is easily available.

  The ratio of the core and shell of such a dye microcapsule is preferably 1/99 to 99/1.

  Whether or not the finished particles have a core-shell structure is actually evaluated as follows.

  First, the obtained particles are dispersed in an organic solvent in which the dye is dissolved. When this dispersion liquid coated and dried on an ITO film is observed with an electron microscope, if the desired core-shell particles are obtained, the shape of the particles is seen, and the dissolved and dried dye (stain-like) is not observed. . In addition, since the absorption of the dye in the solid state is shifted to the shorter wavelength side than the absorption in the dissolved state, the desired core-shell particles can be formed by measuring the spectrophotometry of the above dispersion and the dissolved solution of the dye. Then, since the dye does not dissolve, it can be determined whether or not the desired core-shell particles are obtained by whether the absorption shifts to the long wavelength side.

  In other words, in order to store for a long time and suppress the soaking of the dye as much as possible, the shell portion may be designed to be thick, and in order to increase the absorbability of the dye, the shell portion may be designed to be thin. Considering the absorption of the dye, it is preferable that 1/3 or more of the particle diameter is the core component.

  Next, a method for producing the dye microcapsule dispersion of the present invention will be described.

  First, the required dye and binder are dissolved in an organic solvent. The organic solvent to be used preferably dissolves the dye and the binder and has a solubility in pure water of 1% or less. Here, it is difficult to finely pulverize the dye and the binder because they are hard in water because the dye and the binder are hard in water, so that it is easy to disperse by dissolving in the solvent, or the shell-forming material at the time of encapsulation or This is to facilitate the adsorption of the shell-forming pre-material to the interface (can be achieved by selecting an organic solvent regardless of the dye and binder type).

  The organic solvent that can dissolve the dye and binder of the present invention has a boiling point of 120 ° C. or lower and can dissolve the core component by 1% of its own weight. Any known material can be used as long as it satisfies this condition, but the solubility in water is preferably 10% or less. Examples of organic solvents include esters such as ethyl acetate and butyl acetate, alicyclic groups such as cyclohexane, aliphatic groups such as heptane and hexane, ketones such as cyclohexanone, alcohols, ethers such as dimethyl ether and diethyl ether, benzene, There are aromatics such as toluene and xylene, halogenated hydrocarbons such as carbon tetrachloride, chloroform and dichloromethane, diethyl sulfoxide methyl cellosolve, etc., and these may be used alone or in combination of two or more as required.

  At least a dye and a binder are dissolved in such an organic solvent, and then dispersed in an aqueous solution of a water-soluble resin. For dispersion, there are dispersion using a magnetic stirrer, dispersion using a high-speed dissolver, dispersion using ultrasonic waves, and dispersion using high pressure such as Manton Gorin and Nanomizer, and these may be properly used depending on the desired particle size. Among these, in order to obtain submicron-order dispersed droplets, the dispersion must be performed by ultrasonic dispersion or nanomizer. In particular, ultrasonic dispersion, which is said to be able to create a kind of supercritical state, is preferable. The frequency of the ultrasonic wave to be used is preferably 19 to 22 kHz. At frequencies higher than this, it does not become a submicron order capsule, and at frequencies lower than this, the output is too large and difficult to handle, conversely causing droplet aggregation. May increase the particle size. In order to improve the stability, known anionic surfactants, cationic surfactants, betaine surfactants, nonionic surfactants, and fluorosurfactants are added as necessary so as not to contradict the purpose of the present invention. It doesn't matter.

  The organic solvent is first removed from the dispersion thus obtained. Although the method for removing the organic solvent is not particularly defined, it is preferable to remove the dispersion under reduced pressure by an evaporator or the like so that heat is not so much applied from the viewpoint of preventing the decomposition of the dye.

  After removing the organic solvent, a wall film is formed. If the wall film is not formed prior to the subsequent drying operation, and the wall film is formed at the same time as drying by spray drying or the like, the capsule becomes a multinuclear capsule and the particle size becomes large. Can't get. As a method for forming the wall film, a known method of microencapsulation can be used, but it is particularly preferable to use a simple coacervation method or a complex coacervation method. When gelatin is used as a shell material, a simple core is used. If the shell is made of gelatin and gum arabic, the coacervation method may be used.

  Then, colloidal silica is added. At this time, taking into account the removal after drying due to the submicron particles and the deterioration of the handleability, loose aggregates of the submicron particles may be formed by pH control or the like.

  Thereafter, drying and taking out the dye microcapsules are performed, but also in drying, drying is preferably performed so that heat is not applied from the viewpoint of preventing decomposition of the dye, and drying with a spray dryer is preferable. It is made to dry, controlling the temperature of the powder at the time of drying so that it may become 40 degrees C or less.

  In order to use for coating, it is dispersed in an organic solvent used for coating. The fine particles having colloidal silica on the surface can be dispersed by stirring in an organic solvent using a magnetic stirrer or the like, or dispersed by ultrasonic waves.

  The coating solution of the dye microcapsule dispersion thus prepared is applied to any layer of the support of the photothermographic material of the present invention. Examples of the layer to be coated include a layer between the photosensitive layer and the support or a layer on the back surface side.

  Next, techniques relating to the heat-developable photographic material of the present invention will be described.

  The material of the support (hereinafter referred to as the support according to the present invention) that can be used in the photothermographic material of the present invention includes various polymer materials, glass, wool cloth, cotton cloth, paper, metal such as aluminum, etc. However, plastic films (for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyethylene naphthalate film, polyamide film, polyimide film, cellulose triacetate are preferable because they can be processed into flexible sheets or rolls. It is preferable to use a film or a polycarbonate film.

In order to use the photothermographic material of the present invention for medical image recording, a blue-colored biaxially stretched heat-fixed polyethylene terephthalate film having a thickness of 70 to 250 μm is preferable. Further, the techniques described in paragraph numbers “0030” to “0034” of JP-A-2001-22026 can be used in the present invention. The support according to the present invention is preferably subjected to corona discharge treatment. The discharge amount condition is preferably 5 to 30 W / m ² · min. The support subjected to the corona treatment is preferably coated with the undercoat layer according to the present invention within 1 to 2 months after the corona treatment.

The support according to the present invention can be subjected to plasma surface treatment in addition to corona discharge treatment. In particular, plasma treatment near atmospheric pressure is preferable. As a processing gas in the case of performing plasma discharge, a gas capable of imparting a polar functional group such as an amino group, a carboxyl group, a hydroxyl group, or a carbonyl group is preferable. For example, nitrogen (N ₂ ) gas, hydrogen (H ₂ ) gas, Examples include oxygen (O ₂ ) gas, carbon dioxide (CO ₂ ) gas, ammonia (NH ₃ ) gas, and water vapor. In addition to the reactive gas, an inert gas such as helium or argon may be used, and stable discharge conditions can be obtained by setting it to 60% or more of the gas composition. However, as long as plasma is generated with a pulsed electric field, the inert gas is not necessarily required to be 60% or more, and the reaction gas concentration can be increased. A frequency range of 1 to 100 kHz of the pulse electric field is preferable. The time during which one pulse electric field is applied is preferably 1 to 1000 μs, and the magnitude of the voltage applied to the electrode is preferably in the range where the electric field strength is 1 to 100 kV / cm.

  The organic silver salt that can be used in the photothermographic material of the present invention (hereinafter referred to as the organic silver salt according to the present invention) is a reducible silver source, and is a silver salt of an organic acid or heteroorganic acid, particularly a long chain. (C10-30, preferably 15-25) aliphatic carboxylic acid and a silver salt of a nitrogen-containing heterocyclic compound are preferred. Preference is also given to organic or inorganic complexes described in Research Disclosure 17029, 29963, in which the ligand has a value of 4.0 to 10.0 as the total stability constant for silver ions. Examples of these suitable silver salts include silver salts of organic acids such as gallic acid, succinic acid, behenic acid, stearic acid, arachidic acid, palmitic acid, and lauric acid. Other examples include organic silver salts described in paragraph number “0193” of JP-A-2001-83659. Moreover, the description of paragraph number "0194"-"0197" of the same gazette can also be referred to for the preparation method of organic silver salt and the particle size of organic silver salt. Further, as the organic silver salt according to the present invention, the techniques described in paragraph numbers “0028” to “0033” of JP-A No. 2001-48902, paragraph numbers “0025” to “0041” of JP-A No. 2000-72777, etc. are used. be able to.

  The photosensitive silver halide that can be used in the heat-developable photographic light-sensitive material of the present invention (hereinafter referred to as the photosensitive silver halide according to the present invention) is intrinsic or artificial as an intrinsic property of silver halide crystals. In particular, it can absorb visible or infrared light by physicochemical methods, and physicochemical changes can occur in the silver halide crystal or on the crystal surface when visible or infrared light is absorbed. The silver halide crystal grains processed and prepared as described above.

  The photosensitive silver halide according to the present invention is disclosed in P.I. Chifie et Physique Photographic (published by Paul Montel, 1967) by Glafkides. F. Duffin's Photographic Emission Chemistry (published by The Focal Press, 1966), V.C. L. It can be prepared as a silver halide grain emulsion using the method described in Making and Coating Photographic Emulsion (published by The Focal Press, 1964) by Zelikman et al. Among these, the so-called controlled double jet method for preparing silver halide grains while controlling the formation conditions is preferable. The halogen composition is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide. In addition, the formation of silver halide grains according to the present invention is usually divided into two stages: silver halide seed grain (nucleus) generation and grain growth. The method described in paragraph number “0063” of JP-A-2001-83659 may be used.

  The photosensitive silver halide according to the present invention preferably has a small average grain size in order to keep the cloudiness after image formation low and to obtain good image quality. The average particle size is 0.2 μm or less, more preferably 0.01 to 0.17 μm, and particularly preferably 0.02 to 0.14 μm. The grain size here refers to the length of the edge of the silver halide grain when the silver halide grain is a so-called normal crystal of a cube or octahedron. Further, when the silver halide grain is a tabular grain, it means a diameter when converted into a circular image having the same area as the projected area of the main surface.

  The particle size is preferably monodisperse, and in particular, the techniques described in JP-A-2001-83659, paragraph numbers “0064” to “0066” can be used. The shape of the grains may be any of cubic, octahedral, tetrahedral and tabular silver halide grains. In the case of tabular silver halide grains, the average aspect ratio is generally from 1.5 to 100, preferably from 2 to 50. The techniques described in US Pat. Nos. 5,264,337, 5,314,798, and 5,320,958 can be applied to these. Further, as the particle forming technique, the technique described in paragraph Nos. “0068” to “0090” of Japanese Patent Laid-Open No. 2001-83659 can be applied.

The photosensitive silver halide according to the present invention preferably contains ions of transition metals belonging to Groups 6 to 11 of the Periodic Table of Elements for improving illuminance failure. A preferred content is in the range of 1 × 10 ⁻⁹ to 1 × 10 ⁻² mol, more preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ mol per mol of silver. A preferred transition metal complex or complex ion is represented by the general formula [ML ₆ ] ^m (where M is a transition metal selected from Group 6 to 11 elements of the periodic table, L represents a ligand, m is 0, -Represents 2-, 3- or 4-). Specific examples of the ligand represented by L include halogen ions (fluorine ion, chlorine ion, etc.), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aco ligands, nitrosyl, A thionitrosyl etc. are mentioned, Ako, nitrosyl, and thionitrosyl are preferable. When an acoligand is present, it preferably occupies one or two of the ligands. As transition metal coordination complex ions, those described in JP-A-2001-83659, paragraph numbers “0094” to “0095” can be used.

  The photosensitive silver halide according to the present invention is preferably chemically sensitized. Regarding preferred chemical sensitization, chemical sensitizers and techniques described in JP-A No. 2000-112057, paragraph numbers “0044” to “0045” can be used. The photosensitive silver halide according to the present invention is preferably spectrally sensitized. Regarding preferred spectral sensitization, sensitizing dyes and techniques described in JP-A-2001-83659, paragraph numbers “00099” to “0144” can be used.

  The photosensitive silver halide according to the present invention, together with a sensitizing dye, is a dye that does not itself have a spectral sensitizing action or a substance that does not substantially absorb visible light, and exhibits a strong sensitizing effect. A color sensitizer may be used. As the supersensitizer, compounds described in paragraph numbers “0148” to “0152” of JP-A-2001-83659 can be used. In the present invention, in addition to the supersensitizer described above, compounds represented by general formulas (1) to (4) described in paragraph numbers “0017” to “0019” of JP 2000-250166 A and Macrocycles having at least one heteroatom can be used as supersensitizers. Specific examples of the compound represented by the general formula (1) are described in paragraph numbers “0020” to “0028” of JP-A No. 2000-250166.

  The reducing agent that can be used in the photothermographic material of the present invention (hereinafter referred to as the reducing agent according to the present invention) is appropriately selected from known reducing agents in the technical field of photothermographic materials. can do. In particular, when an aliphatic carboxylic acid silver salt is used as the organic silver salt, polyphenols in which two or more hydroxyphenyl groups are linked by an alkylene group or sulfur, particularly a position adjacent to the hydroxyl group substitution position of the hydroxyphenyl group. Two or more hydroxyphenyl groups substituted with at least one alkyl group (eg, methyl group, ethyl group, propyl group, t-butyl group, cyclohexyl group, etc.) or acyl group (eg, acetyl group, propionyl group, etc.) Are preferably bisphenols linked by an alkylene group or sulfur.

For example, hindered phenol type reducing agents described in paragraph numbers “0047” to “0048” of JP-A No. 2000-112057 are preferably used in the present invention. Specific exemplary compounds thereof are described in paragraph numbers “0050” to “0051” of JP-A No. 2000-112057. The amount of the reducing agent used is 1 × 10 ⁻² to 10 mol, preferably 1 × 10 ^{−2 to} 1.5 mol, per mol of silver.

  The binder that can be used in the photothermographic material of the present invention is transparent or translucent, generally colorless, and is a natural polymer or a synthetic polymer. Examples of the binder include natural or synthetic polymers described in JP-A No. 2001-66725, paragraph number “0193”. As the binder, polyvinyl acetals are preferable, and polyvinyl butyral is particularly preferable. As a usage-amount of a binder, the ratio of a binder and organic silver salt has the preferable range of 15: 1 to 1: 2, especially 8: 1 to 1: 1. Moreover, a polymer latex can also be preferably used as the binder according to the present invention. Regarding the polymer latex, the compounds and techniques described in paragraph numbers “0194” to “0203” of JP-A No. 2001-66725 can be applied.

  By using a cross-linking agent, the binder is improved in film formation, development unevenness is reduced, and an effect of suppressing fogging during storage and suppressing generation of printout silver after development can be expected. Aldehyde-type, epoxy-type, ethyleneimine-type, vinylsulfone-type, sulfonate-type, acryloyl-type, carbodiimide-type, and silane-compound-type crosslinking agents described in JP-A-50-96216 can be used. Preferred crosslinking agents are isocyanate compounds, silane compounds, epoxy compounds or acid anhydrides. As for the isocyanate compound, compounds and techniques described in JP-A-2001-83659, paragraph numbers “0159” to “0168” can be applied. For the epoxy compound, the compounds and techniques described in JP-A-2001-83659, paragraph numbers “0170” to “0180” can be applied. For the acid anhydride, compounds and techniques described in JP-A-2001-83659, paragraph numbers “0182” to “0187” can be applied. As for the silane compound, compounds and techniques described in JP-A No. 2001-264930, paragraph numbers “0022” to “0028” can be applied.

  In the heat-developable photographic light-sensitive material of the present invention, a color toner can be used as necessary. As the toning agent that can be used in the present invention, compounds and techniques described in paragraph numbers “0064” to “0066” of JP-A-2000-198757 can be applied.

  Since the photothermographic material of the present invention uses a reducing agent having a proton such as bisphenols or sulfonamidophenols as a reducing agent, it generates active species capable of extracting these hydrogens. It is preferable that a compound capable of inactivating the reducing agent is contained. As the colorless photo-oxidizing substance, a compound capable of generating free radicals as reactive species upon exposure is preferable. As these compounds, biimidazolyl compounds disclosed in paragraphs “0065” to “0069” of JP-A-2000-57004 and iodonium compounds disclosed in paragraphs “0071” to “0082” of the same publication are used. Can be used.

  In the photothermographic material of the present invention, a compound that releases a halogen atom as an active species can be used as a compound that deactivates the reducing agent and prevents the reducing agent from reducing the organic silver salt to silver. As specific examples of the compound that generates an active halogen atom, compounds disclosed in paragraphs “0086” to “0102” of JP-A No. 2000-57004 can be used.

  The photothermographic material of the present invention can use a silver saving agent. The silver saving agent refers to a compound that can reduce the amount of silver necessary to obtain a certain silver image density. Various action mechanisms of the function of decreasing can be considered, but a compound having a function of improving the covering power of developed silver is preferable. Here, the covering power of developed silver refers to the optical density per unit amount of silver. Examples of silver saving agents that can be used in the present invention include hydrazine derivative compounds disclosed in paragraphs “0075” to “0081” of JP-A No. 2001-66725, paragraph numbers “0109” to “0132” of the publication. And quaternary onium compounds disclosed in paragraph numbers “0150” to “0158” of the publication.

  The photothermographic material of the present invention is obtained by providing a photosensitive layer containing an organic silver salt, a photosensitive silver halide, a reducing agent, and a binder on a support provided with an undercoat layer according to the present invention. However, it is preferable to form a non-photosensitive layer on the photosensitive layer. For example, it is preferable that a backing layer is provided on the photosensitive layer for the purpose of protecting the photosensitive layer by the protective layer and for preventing sticking on the opposite surface of the support. As the binder used in these protective layers and backing layers, polymers having a glass transition point higher than that of the photosensitive layer and less likely to be scratched or deformed, for example, polymers such as cellulose acetate and cellulose acetate butyrate are among the above binders. To be elected. In order to adjust the gradation, two or more photosensitive layers may be provided on one side of the support or one or more layers on both sides of the support.

  The photothermographic material of the present invention is formed by preparing a coating solution obtained by dissolving or dispersing the above-mentioned constituent layers in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment. Is preferred. Here, “multiple simultaneous multi-layer coating” means that a coating solution for each constituent layer (for example, photosensitive layer, protective layer) is prepared, and each layer is repeatedly coated and dried when it is coated on a support. Rather, it means that each constituent layer can be formed in a state in which multiple layers can be simultaneously applied and dried. That is, it is preferable to provide the upper layer before the remaining amount of the total solvent in the lower layer becomes, for example, 70% by mass or less.

  There are no particular restrictions on the method of applying multiple layers of each constituent layer simultaneously. For example, a known method such as a bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, or extrusion coating method may be used. it can. Of these, a pre-weighing type coating method called an extrusion coating method is more preferable. The extrusion coating method is suitable for precision coating and organic solvent coating because the solvent does not volatilize on the slide surface unlike the slide coating method. Although this coating method has been described on the side having the photosensitive layer, the same applies to the case of coating with undercoating when providing the backcoat layer. Of course, the photothermographic material of the present invention may be an aqueous solvent.

  The development conditions of the photothermographic material of the present invention will be described. Development conditions vary depending on the equipment, apparatus, or means used, but typically involve heating the imagewise exposed photothermographic dry imaging material at a suitable high temperature. The latent image obtained after the exposure can be developed, for example, by heating at about 80 to 200 ° C., preferably about 100 to 200 ° C. for about 1 second to 2 minutes. When the heating temperature is 80 ° C. or lower, sufficient image density cannot be obtained in a short time. When the heating temperature is 200 ° C. or higher, the binder is melted and transferred to a roller, which affects not only the image itself but also the transportability and the developing machine. . By heating, a silver image is generated by an oxidation-reduction reaction between an organic silver salt (which functions as an oxidizing agent) and a reducing agent.

  This reaction process proceeds without supplying a treatment liquid such as water from the outside. The apparatus, device, or means for heating may be performed by a heating means typical as a heat generator using a hot plate, an iron, a hot roller, carbon, white titanium, or the like. If the photothermographic material of the present invention has a protective layer, the surface having the protective layer is brought into contact with the heating means for heat treatment in order to achieve uniform heating, thermal efficiency, and workability. It is preferable from the above points, and it is preferable that the surface is conveyed while being in contact with a heat roller, heated and developed.

During development, the photothermographic material of the present invention is 5 to 1000 mg / m ² of the solvent, preferably prepared such that 100 to 500 mg / m ^2. As a result, a photothermographic material having high sensitivity, low fog and high maximum density is obtained.

  Solvents include ketones such as acetone, methyl ethyl ketone, isophorone, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, hexylene glycol, etc. Glycols, ether alcohols such as ethylene glycol monomethyl ether and diethylene glycol monoethyl ether, ethers such as isopropyl ether, esters such as ethyl acetate and butyl acetate, chlorides such as methylene chloride and dichlorobenzene, hydrocarbons Etc. Other examples include water, formamide, dimethylformamide, toluidine, tetrahydrofuran, and acetic acid. However, it is not limited to these. These solvents can be used alone or in combination.

  The content of the solvent in the photothermographic material can be adjusted by changing conditions such as temperature conditions in the drying step after the coating step. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

  The exposure conditions of the photothermographic material of the present invention will be described.

  In the exposure of the photothermographic material of the present invention, it is desirable to use a light source suitable for the color sensitivity imparted to the photothermographic material. For example, when it can be felt by infrared light, it can be applied to any light source as long as it is in the infrared light range, but the laser power is high or the photothermographic material of the present invention is transparent. From the viewpoint of being able to be made, an infrared semiconductor laser (780 nm, 820 nm) is preferably used.

  The exposure of the photothermographic material of the present invention is preferably performed by laser scanning exposure, and various methods can be adopted as the exposure method.

  As a first preferred method, there is a method using a laser scanning exposure machine in which the angle formed between the exposure surface of the photothermographic material and the scanning laser beam is not substantially perpendicular. Here, “substantially not perpendicular” means the angle that is closest to the vertical during laser scanning, preferably 55 degrees or more and 88 degrees or less, more preferably 60 degrees or more and 86 degrees or less, and even more preferably. Means 65 degrees or more and 84 degrees or less, and most preferably 70 degrees or more and 82 degrees or less. The beam spot diameter on the exposed surface of the photosensitive material when the laser beam is scanned onto the photothermographic material is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the angle of deviation of the laser incident angle from the vertical. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

  As a second method, it is also preferable to perform exposure using a laser scanning exposure machine that emits scanning laser light that is a vertical multi. Compared with a single longitudinal mode scanning laser beam, image quality degradation such as generation of interference fringe-like unevenness is reduced. In order to make it vertically multi-ply, methods such as using return light by multiplexing and applying high-frequency superposition are preferable. Here, the vertical multi means that the exposure wavelength is not single, and the distribution of the exposure wavelength is usually 5 nm or more, preferably 10 nm or more. The upper limit of the exposure wavelength distribution is not particularly limited, but is usually about 60 nm.

  As a third aspect, it is also preferable to form an image by scanning exposure using two or more lasers. An image recording method using a plurality of lasers is a technique used in image writing means of laser printers and digital copying machines that write images line by line in a single scan due to the demand for higher resolution and higher speed. For example, it is known from JP-A-60-166916. This is a method in which laser light emitted from a light source unit is deflected and scanned by a polygon mirror and imaged on a photoconductor via an fθ lens or the like. In principle, this is the same laser scanning as a laser imager. It is an optical device. Laser image formation on the photothermographic material for image development of laser printers and digital copiers is based on the application of writing multiple lines of images in one scan, from the position where one laser beam is imaged. The next laser beam is imaged with a shift of one line. Specifically, the two light beams are close to each other in the sub-scanning direction on the image plane with an interval of the order of several tens of μm, and the print density is 400 dpi (here, one dot per inch, ie, 2.54 cm). The printing density is defined as dpi (dot per inch), and the sub-scanning direction pitch of the two beams is 63.5 μm, and 600 dpi is 42.3 μm.

  Unlike the method in which the resolution is shifted in the sub-scanning direction, it is also preferable to form an image by condensing two or more lasers at the same place on the exposure surface while changing the incident angle. At this time, when the exposure energy on the exposure surface when writing with one normal laser (wavelength λ [nm]) is E, N lasers used for exposure have the same wavelength (wavelength λ [nm]). When the same exposure energy (En) is used, it is preferable that the range is 0.9 × E ≦ En × N ≦ 1.1 × E. By doing so, energy is secured on the exposure surface, but the reflection of each laser beam to the image forming layer is reduced because the exposure energy of the laser is low, and thus the occurrence of interference fringes is suppressed. In the above description, a plurality of lasers having the same wavelength as λ are used. However, lasers having different wavelengths may be used. In this case, it is preferable that (λ−30) <λ1, λ2,... Λn ≦ (λ + 30) with respect to λ [nm].

In the exposure methods of the first, second, and third aspects described above, as lasers used for scanning exposure, generally known solid lasers such as ruby lasers, YAG lasers, and glass lasers; He—Ne lasers, Ar ion laser, Kr ion laser, CO ₂ laser, CO laser, He—Cd laser, N ₂ laser, excimer laser and other gas lasers; InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP ₂ laser, Semiconductor lasers such as GaSb lasers; chemical lasers, dye lasers, etc. can be selected and used in a timely manner, but among these, semiconductor lasers with wavelengths of 600 to 1200 nm are used due to maintenance and light source size problems. Preferred.

  In the laser used in a laser imager or laser image setter, the beam spot diameter on the exposure surface when scanned with a photothermographic material is generally 5 to 75 μm as the minor axis diameter, and the major axis diameter. The laser beam scanning speed can be set to an optimum value for each photothermographic material by the sensitivity and laser power at the laser oscillation wavelength inherent to the photothermographic material.

  Hereinafter, the present invention will be described in detail with reference to examples.

Example 1
[Preparation of microcapsule fine particles 3]
It was confirmed that the compound 1-1 and 0.11 g were added to 23.88 g of ethyl acetate with stirring, and the precipitate disappeared even when the stirring was stopped. Thereafter, 1.01 g of butyral resin (Butbar B-79) was added to completely dissolve the butyral resin.

  On the other hand, 1.25 g of gelatin (Konica gelatin: 01LU-90) was dissolved in 47.5 g of pure water, and 1.25 g of a 10% solution of a surfactant (Sanyo Kasei: Sanmorin OT-70) was added. And an ethyl acetate solution of butyral resin were slowly added, and dispersion was continued for 10 minutes with an ultrasonic disperser to obtain a slightly turbid dispersion. To this, 50 g of a 2.5% aqueous solution of gum arabic is added and stirred for 2 minutes. When the obtained dispersion was distilled off under reduced pressure until no odor of ethyl acetate was produced using a rotary evaporator, a clear aqueous dispersion was obtained. It was 200 nm when the particle size of the obtained water dispersion was measured. Thereafter, 5% acetic acid was added to the aqueous dispersion to adjust the pH to 3.5, causing coacervation, and microencapsulation. Further, while stirring well, a compound that reacts with gelatin (glutaraldehyde) was added so as to be 10% (solid content) of the whole, and reacted at 50 ° C. for 4 hours. Thereafter, decantation and washing with water were performed three times, and after adding 10 g of colloidal silica (PL-2 manufactured by Fuso Chemical Co., Ltd.) having a salt concentration of 1 ppm or less and stirring well, the particles were dried with a spray drier. 3 powder was obtained.

  Similarly, as shown in Table 1, dyes, water-soluble resins, reactive compounds, colloidal silica, and dispersion conditions were changed, and powders of fine particles 1, 2, 4 to 9, and 11 to 20 were obtained.

[Preparation of microcapsule fine particles 10]
It was confirmed that the compound 1-1 and 0.11 g were added to 23.88 g of ethyl acetate with stirring, and the precipitate disappeared even when the stirring was stopped. Thereafter, 1.01 g of butyral resin (Butbar B-79) was added to completely dissolve the butyral resin.

  On the other hand, 1.25 g of gelatin (Konica gelatin: 01LU-90) was dissolved in 47.5 g of pure water, and 1.25 g of a 10% solution of a surfactant (Sanyo Kasei: Sanmorin OT-70) was added. And an ethyl acetate solution of butyral resin were slowly added, and dispersion was continued for 10 minutes with an ultrasonic disperser to obtain a slightly turbid dispersion. To this, 50 g of a 2.5% aqueous solution of gum arabic is added and stirred for 2 minutes. When the obtained dispersion was distilled off under reduced pressure until no odor of ethyl acetate was produced using a rotary evaporator, a clear aqueous dispersion was obtained. The particle size of the obtained aqueous dispersion was measured and found to be 5000 nm. Thereafter, 10 g of colloidal silica (PL-2 manufactured by Fuso Chemical Industry Co., Ltd.) having a salt concentration of 1 ppm or less was added and stirred well, followed by drying with a spray dryer to obtain a fine particle 10 powder.

  The obtained fine particle powders 1 to 20 were dispersed in MEK at a concentration of 1%, and the dispersibility was visually evaluated. In addition, since the absorption of the dye is longer in the solid state than in the dissolved state, it is determined that the dye absorption shifted to the longer wavelength side is dispersed and the unchanged one is dissolved compared to the spectral absorption of the raw material. .

5: Dispersed by stirring with a magnetic stirrer 4: Dispersed when ultrasonic waves are applied for 1 minute 3: Dispersed when ultrasonic waves are applied for 5 minutes 2: Dispersed when ultrasonic waves are applied for 30 minutes or more 1: Dissolution

  Table 1 shows that the dye microcapsule dispersion of the present invention has good dispersibility.

  Next, a method for preparing a photothermographic material will be described.

<Production of support>
One side of a polyethylene terephthalate film base (thickness: 175 μm) colored blue with a concentration of 0.170 was subjected to a corona discharge treatment of 0.5 kV · A · min / m ² , and then the following undercoat coating solution was applied thereon. Using A, the undercoat layer a was applied so that the dry film thickness was 0.2 μm. Further, the other surface is similarly subjected to a corona discharge treatment of 0.5 kV · A · min / m ² , and then the undercoat coating solution B described below is used thereon to form the undercoat layer b with a dry film thickness. It coated so that it might be set to 0.1 micrometer. Thereafter, heat treatment was performed at 130 ° C. for 15 minutes in a heat treatment type oven having a film transport device composed of a plurality of roll groups.

<Undercoat coating liquid A>
270 g of copolymer latex liquid (solid content 30%) of 30% by mass of n-butyl acrylate, 20% by mass of t-butyl acrylate, 25% by mass of styrene and 25% by mass of 2-hydroxyethyl acrylate, sodium dodecylbenzenesulfonate 6 g and 0.5 g of methylcellulose were mixed. Further, 1.3 g of silica particles (Syloid 350, manufactured by Fuji Silysia) was added to 100 g of water, and the dispersion was subjected to a dispersion treatment for 30 minutes with an ultrasonic dispersing machine (manufactured by ALEX Corporation, Ultrasonic Generator, frequency 25 kHz, 600 W). Was finally made up to 1000 ml with water, and this was used as the undercoat coating solution A.

(Preparation of colloidal tin oxide dispersion)
A homogeneous solution was prepared by dissolving 65 g of stannic chloride hydrate in 2000 ml of a water / ethanol mixed solution. Subsequently, this was boiled and the coprecipitate was obtained. The generated precipitate was taken out by decantation and washed several times with distilled water. Silver nitrate is dropped into distilled water from which the precipitate has been washed, and after confirming that there is no reaction of chlorine ions, distilled water is added to the washed precipitate to make a total volume of 2000 ml. Furthermore, 40 ml of 30% aqueous ammonia was added, the aqueous solution was heated, and concentrated to a volume of 470 ml to prepare a colloidal tin oxide dispersion.

<Undercoat coating solution B>
A copolymer latex liquid (solid content 30) of 37.5 g of the above colloidal tin oxide dispersion, 20% by mass of n-butyl acrylate, 30% by mass of t-butyl acrylate, 27% by mass of styrene and 28% by mass of 2-hydroxyethyl acrylate. %) 3.7 g, n-butyl acrylate 40 mass%, styrene 20 mass%, glycidyl methacrylate 40 mass% copolymer latex liquid (solid content 30%) 14.8 g and sodium dodecylbenzenesulfonate 0.1 g And it was made into 1000 ml with water, and it was set as the undercoat coating liquid B.

<Back side application>
While stirring 830 g of methyl ethyl ketone (MEK), 84.2 g of cellulose acetate butyrate (manufactured by Eastman Chemical, CAB381-20) and 4.5 g of polyester resin (manufactured by Boston, VitelPE2200B) were added and dissolved. Next, 4.5 g of F-type active agent (Surflon KH40, manufactured by Asahi Glass Co., Ltd.) and 2.3 g of F-type active agent (manufactured by Dainippon Ink Co., Ltd., Megafag F120K) dissolved in 43.2 g of methanol are added to the dissolved solution. The mixture was sufficiently stirred until dissolved. Finally, 75 g of silica dispersed in a dissolver type homogenizer at a concentration of 1% by mass in methyl ethyl ketone (WR Grace, Syloid 64X6000) was added and stirred to prepare a coating solution for the back surface side.

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

<Preparation of coating solutions 1-20 for the layer between the photosensitive layer and the support>
While stirring 955 g of methyl ethyl ketone (MEK), 88.7 g of butyral resin was added and dissolved. Next, the fine particle powder of 1 to 20 is added to the dissolved solution so that the dye content is 6.0 g, and the mixture is sufficiently stirred to apply the coating solutions 1 to 20 between the photosensitive layer and the support. Was prepared.

<Preparation of photosensitive silver halide emulsion 1>
Solution (A1)
Phenylcarbamoylated gelatin 88.3g
Compound (K) (10% aqueous methanol solution) 10 ml
Potassium bromide 0.32g
Finish to 5429 ml with water Solution (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
Solution (C1)
Potassium bromide 51.55g
Potassium iodide 1.47g
Finish to 660 ml with water Solution (D1)
Potassium bromide 154.9g
4.41 g of potassium iodide
Osmium chloride (1% solution) 0.93ml
Finish to 1982ml with water Solution (E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount solution (F1)
Potassium hydroxide 0.71g
Finish to 20 ml with water Solution (G1)
56% acetic acid aqueous solution 18.0 ml
Solution (H1)
Anhydrous sodium carbonate 1.72 g
Finish to 151 ml with water Compound (K):
_{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)
Using the mixing stirrer disclosed in Japanese Patent Publication Nos. 58-58288 and 58-58289, a 1/4 amount of the solution (B1) and a total amount of the solution (C1) were added to the solution (A1) at a temperature of 40 ° C., pAg8 While controlling at 0.09, nucleation was performed by adding 4 minutes and 45 seconds by the simultaneous mixing method. After 1 minute, the entire amount of the solution (F1) was added, followed by 20 ml of a 5% aqueous solution of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene. During this time, the pAg was adjusted as appropriate using the aqueous solution (E1). After 6 minutes, 3/4 amount of the solution (B1) and the total amount of the solution (D1) were added over 14 minutes and 15 seconds by the simultaneous mixing method while controlling the temperature at 40 ° C. and pAg 8.09. After stirring for 5 minutes, the entire amount of the solution (G1) was added to precipitate the silver halide emulsion. The supernatant was removed leaving 2000 ml of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was sedimented again. The remaining portion of 1500 ml was left, the supernatant was removed, 10 L of water was further added, and after stirring, the silver halide emulsion was allowed to settle. After leaving 1500 ml of the sedimented portion and removing the supernatant, the solution (H1) was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount was 1161 g per mole of silver to obtain an emulsion. This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 0.050 μm, a grain size variation coefficient of 14%, and a [100] face ratio of 93%.

  Next, 240 ml of triphenylphosphine selenide (0.5% methanol solution) was added to the above emulsion, and a chloroauric acid sensitizer equivalent to 1/20 mol of this sensitizer was added, and the mixture was added at 55 ° C. for 120 minutes. Stir to give chemical sensitization. This is designated as photosensitive silver halide emulsion 1.

<Preparation of powdered aliphatic carboxylic acid silver salt 1>
130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved in 4720 ml of pure water at 80 ° C. Next, 540.2 ml of 1.5M sodium hydroxide aqueous solution was added, 6.9 ml of concentrated nitric acid was added, and then cooled to 55 ° C. to obtain a fatty acid sodium solution. While maintaining the temperature of the fatty acid sodium solution at 55 ° C., 45.3 g of the above photosensitive silver halide emulsion 1 and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 702.6 ml of 1M silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an aliphatic carboxylic acid silver salt dispersion. Thereafter, the obtained aliphatic carboxylic acid silver salt dispersion was transferred to a water-washing vessel, deionized water was added and stirred, and then allowed to stand to float and separate the aliphatic carboxylic acid silver salt dispersion. Was removed. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 50 μS / cm, and centrifugal dehydration was carried out. Using a dryer (manufactured by Seishin Enterprise Co., Ltd.), powdery aliphatic carboxylic acid silver salt 1 was obtained by drying until the water content became 0.1% under the operating conditions of nitrogen gas atmosphere and dryer inlet hot air temperature. An infrared moisture meter was used to measure the water content of the aliphatic carboxylic acid silver salt composition.

<Preparation of Preliminary Dispersion 1>
Dissolve 14.57 g of polyvinyl butyral resin in 1457 g of methyl ethyl ketone, and gradually add 500 g of powdered aliphatic carboxylic acid silver salt 1 while stirring with a dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN. By doing so, Preliminary Dispersion 1 was prepared.

<Preparation of photosensitive emulsion dispersion 1>
Media type disperser DISPERMAT SL filled with 80% of the internal volume of 0.5 mm zirconia beads (manufactured by Treceram Toray) so that the residence time in the mill is 1.5 minutes using a pump. Photosensitive emulsion dispersion 1 was prepared by supplying to -C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 8 m / s.

<Preparation of additive solution A>
1.0 g of macrocyclic compound S-19 and 0.31 g of potassium acetate were dissolved in 4.97 g of methanol to prepare additive solution A.

<Preparation of infrared sensitizing dye liquid A>
19.2 mg of the following infrared sensitizing dye 1-3, 1.488 g 2-chloro-benzoic acid, 2.7779 g stabilizer 2 and 365 mg 5-methyl-2-mercaptobenzimidazole Infrared sensitizing dye solution A was prepared by dissolving in MEK in the dark.

<Preparation of additive liquid a1>
As a developer, 14.0 g of 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane and 1.54 g of 4-methylphthalic acid, 0.48 g of the above compound 1 was dissolved in 110 g of MEK to obtain an additive solution a1.

<Preparation of additive liquid b>
3.43 g of phthalazine was dissolved in 40.9 g of MEK to obtain additive solution b.

<Preparation of additive liquid c>
3.56 g of antifoggant 2 and 0.25 g of sodium p-toluenethiosulfonate were dissolved in 40.9 g of MEK to obtain additive liquid c.

<Preparation of photosensitive layer coating solution 1>
In an inert gas atmosphere (nitrogen 97%), the photosensitive emulsion dispersion 1 (50 g) and 15.11 g of MEK were kept at 21 ° C. with stirring, and 390 μl of antifoggant 1 (10% methanol solution) was added, Stir for 1 hour. Next, a methanol solution of iridium chloride was added so as to be 1.0 × 10 ⁻⁵ mol per mol of silver halide, and 494 μl of calcium bromide (10% methanol solution) was further added, followed by stirring for 30 minutes. Subsequently, 0.21 g of the additive solution A and 1.32 g of the infrared sensitizing dye solution A were added and stirred for 1 hour. Thereafter, the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While keeping the temperature at 13 ° C., 13.31 g of polyvinyl acetal resin as a binder resin was added and stirred for 30 minutes, and then 1.084 g of tetrachlorophthalic acid (9.4 mass% MEK solution) was added and stirred for 15 minutes. . While continuing to stir, 12.43 g of additive liquid a1, 1.6 ml of Desmodur N3300 / Moby aliphatic isocyanate (10% MEK solution), 4.27 g of additive liquid b, 10.0 g of additive liquid c By sequentially adding and stirring, a photosensitive layer coating solution 1 was obtained.

(Preparation of matting agent dispersion)
Cellulose acetate butyrate (Eastman Chemical, 7.5 g CAB171-15) is dissolved in 42.5 g of MEK, and 5 g of calcium carbonate (Speciality Minerals, Super-Pflex200) is added to it and dissolved in a dissolver type homogenizer. Then, a matting agent dispersion was prepared by dispersing at 8000 rpm for 30 minutes.

<Preparation of surface protective layer coating solution>
While stirring 865 g of MEK (methyl ethyl ketone), 96 g of cellulose acetate butyrate (manufactured by Eastman Chemical, CAB171-15), 4.5 g of polymethylmethacrylic acid (Rohm & Haas, Paraloid A-21), VSC 1.5 g, 1.0 g of benztriazole, and 1.0 g of F-based activator (Asahi Glass Co., Surflon KH40) were added and dissolved. Next, 30 g of the above matting agent dispersion was added and stirred to prepare a surface protective layer coating solution.

[Preparation of Photothermographic Photosensitive Materials 101-120]
Samples 101 to 120 are coated by simultaneously applying the coating solutions 1 to 20 for the layer between the photosensitive layer and the support, the photosensitive layer coating solution 1 and the surface protective layer coating solution using a known extrusion coater. Produced. The layer between the photosensitive layer and the support is 3.7 μm, the silver in the photosensitive layer is 1 × 10 ⁻⁴ g / m ³ per unit volume, and the surface protective layer is 2.5 μm in dry film thickness. It was. 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.

<Exposure and development processing>
From the photosensitive layer side of the sample produced as described above, exposure by laser scanning was given by an exposure machine using a semiconductor laser having a longitudinal multimode wavelength of 800 to 820 nm by high frequency superposition as an exposure source. At this time, an image was formed by setting the angle of the exposure surface of the sample and the exposure laser beam to 75 degrees. Thereafter, using an automatic developing machine having a heat drum, the sample was thermally developed at 110 ° C. for 15 seconds so that the protective layer of the sample was in contact with the drum surface. At that time, exposure and development were performed in a room adjusted to 23 ° C. and 50% RH.

<Evaluation of sensitivity>
The obtained image was evaluated with a densitometer. As a result of the measurement, the sensitivity (reciprocal of the ratio of the exposure amount giving a density higher by 1.0 than the unexposed portion) was evaluated, and the relative value when the comparison samples 101, 113, and 116 of the respective dyes were set to 100 was used. The results are shown in Table 2.

<Evaluation of sharpness>
Sharpness was evaluated using an MTF value of 15 / mm at an optical density of 1.0.

<Evaluation of residual color>
The residual color of the sample was visually evaluated according to the evaluation criteria shown below on a light source table for photographic observation.

A: There is no pigment residue B: There is a little pigment residue, but it does not interfere with the diagnosis C: The pigment residue is present to the extent that the diagnosis is anxious D: The pigment residue is apparent and the diagnosis is hindered Sexual evaluation>
An overall evaluation of coating unevenness and streak failure of the unexposed samples 101 to 120 was visually evaluated in five stages according to the following evaluation criteria.

A: Good finish without occurrence of coating unevenness and streaks B: Very little coating unevenness and streaks C: There is slight coating unevenness and streaks D: There are uneven coating and streaks E: Uneven coating , Streaks are intense and the finish is very bad.

  The applicability ranks D and E cannot be used as products. If it is at least C or more, the productivity is poor and the product cannot be produced.

  From Table 2, it can be seen that the photothermographic material of the present invention is clearly superior to the comparison when the sensitivity, sharpness, residual color property and coating property are comprehensively evaluated.

Claims (12)

A micro-particle obtained by dissolving a dye and a binder in an organic solvent and dispersing it in an aqueous solution containing a water-soluble resin, evaporating the organic solvent to form a wall film (shell), and evaporating and drying the water. A method for producing a dye microcapsule dispersion comprising dispersing capsules in an organic solvent. Dissolve the dye and binder in an organic solvent and disperse it in an aqueous solution containing a water-soluble resin, then evaporate the organic solvent to form a wall film (shell), add colloidal silica, and evaporate the water. A method for producing a dye microcapsule dispersion, characterized in that microcapsules obtained by drying are dispersed in an organic solvent. 3. The dye microcapsule dispersion according to claim 1, wherein when the dye and the binder are dissolved in the organic solvent and dispersed in an aqueous solution containing a water-soluble resin, ultrasonic dispersion is performed at a frequency of 19 to 22 kHz. Manufacturing method. The method for producing a dye microcapsule dispersion according to claim 2 or 3, wherein the concentration of the salt contained in the colloidal silica is 1 ppm or less based on the solid content of the colloidal silica. After forming the said wall film (shell), the compound which reacts with the hydrophilic group of water-soluble resin is added, The manufacturing of the dye microcapsule dispersion of any one of Claims 1-4 characterized by the above-mentioned. Method. The dye microcapsule dispersion according to claim 5, wherein a compound that reacts with the hydrophilic group of the water-soluble resin is added so as to have a solid content concentration of 5 to 20% of the aqueous dispersion of the dye microcapsule. Manufacturing method. The method for producing a dye microcapsule dispersion according to any one of claims 1 to 6, wherein the water-soluble resin is gelatin and gum arabic. The method for producing a dye microcapsule dispersion according to any one of claims 1 to 6, wherein the water-soluble resin is gelatin. A dye microcapsule dispersion produced by the method for producing a dye microcapsule dispersion according to any one of claims 1 to 8. The dye microcapsule dispersion according to claim 9, wherein an average particle diameter of the dye microcapsules in the dye microcapsule dispersion is 100 nm or more and 1 µm or less. A photothermographic material, wherein a coating liquid containing the dye microcapsule dispersion according to claim 9 or 10 is coated on either side of a support to form a layer. 12. The photothermographic material according to claim 11, wherein the layer is located between the photosensitive layer and the support or on the opposite side of the photosensitive layer through the support.