JP2005077794A - Heat developable photographic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photographic material having good moisture resistance and improved scratch resistance. <P>SOLUTION: The heat developable photographic material having a photosensitive layer containing organic silver salt grains, silver halide grains and a reducing agent on a support has a moisture-proof layer consisting of a latex, a wax emulsion, and an organic matting agent whose average particle diameter is 0.5-20 μm as an outermost layer on the photosensitive layer side of the support. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photothermographic material, and more particularly, to a photothermographic material having good humidity resistance and improved scratch resistance (hereinafter also referred to as “photothermographic material” or simply “photosensitive material”). .

  Many photosensitive materials that have a photosensitive layer on a support and perform image formation by image exposure are known. Among them, as a system that can simplify environmental preservation and image forming means, there is a technique for forming an image by heat development.

  In recent years, in the field of photoengraving, reduction of processing waste liquid is strongly desired from the viewpoint of environmental conservation and space saving. Therefore, there is a need for technology related to photothermographic materials that can be efficiently exposed by a laser scanner or a laser image setter and can form a clear black image with high resolution and sharpness. It is said that. These 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.

  For example, US Pat. Nos. 3,152,904, 3,457,075, and D.W. Morgan and B.M. “Thermally Processed Silver Systems A” (Imaging Processes and Materials), 8th edition, Sturge. V. by Shely. (Walworth, A. Shepp, 2 pages, 1969).

  When performing color printing, the photosensitive material for printing plate making usually uses a plurality of films separated for each color. They are baked on each plate and printed on top of each other. When films that are separated according to a plurality of colors are overlapped, if they do not overlap completely, a phenomenon occurs in which colors are shifted when printed. Therefore, in the photothermographic material for printing plate making, it is an important issue how to suppress the plate size change due to heat.

As a method for improving the heat-resistant dimensional stability of the photosensitive material, Japanese Patent Application Laid-Open Nos. 10-10676 and 10-10777 include a high temperature of 80 to 200 ° C. and a low temperature of 39.2 × 10 ^{2 to} 58.8 × 10 ⁴ Pa. A technique is disclosed in which heat treatment is carried out while being conveyed by tension to reduce the thermal shrinkage of the support.

  In the photothermographic material, a reducible non-photosensitive silver source (such as an organic silver salt), a catalytically active photocatalyst (such as silver halide) and a silver reducing agent are usually dispersed in an organic binder matrix. Contains. The photosensitive material is stable at room temperature, but when heated to a high temperature (for example, 80 ° C. or higher) after exposure, the silver is obtained through a redox reaction between a reducible silver source (which functions as an oxidizing agent) and the reducing agent. Generate. This redox reaction is promoted by the catalytic action of the latent image generated by exposure. The silver produced by the reaction of the reducible silver salt in the exposed area provides a black image, which is symmetric with the unexposed area and the image is formed.

  In such a photothermographic material, the moisture content in the light-sensitive material decreases during the low humidity period in winter and the development reaction does not proceed easily, and the concentration does not come out. There is a problem that the amount increases, the development reaction easily proceeds, the sensitivity increases, and the character line width increases.

  Conventional technologies that use vinylidene chloride as the protective layer to reduce the influence of the character line width under high humidity (for example, see Patent Document 1), and the effect of humidity on the dimensional performance using vinylidene chloride as the undercoat However, there is a problem in the environment. Also, a technique for thickening the protective layer to ensure low humidity concentration (for example, see Patent Document 2) and a technique for changing the drying temperature to reduce the influence of the character line width under high humidity (for example, Patent Document) 3) is also known but not sufficient.

As a result of intensive studies on the above problems, the present inventor has found that the humidity resistance of photographic performance can be improved by applying an aqueous coating solution in which a specific latex and a wax emulsion are mixed to the outermost layer of the photosensitive layer. As a result of further investigation, it was found that the scratch resistance was insufficient when a matting agent of inorganic particles was used in the above system.
JP 2001-272742 A JP 2001-249425 A JP 2002-55413 A

  An object of the present invention is to provide a photothermographic material having good humidity resistance and improved scratch resistance.

  As a result of diligent investigations on the above problems, the present inventor is excellent in humidity resistance of photographic performance by adding a specific organic matting agent to a layer composed of a latex and a wax emulsion, and further, scratch resistance. It was found that a heat-developable photographic light-sensitive material excellent in the above can be obtained. The present invention has been reached from such findings.

  That is, the configurations that achieve the object of the present invention are the following (1) to (8).

  (1) In a photothermographic material having a photosensitive layer containing organic silver salt particles, silver halide particles and a reducing agent on a support, latex and wax are formed on the outermost layer on the photosensitive layer side of the support. A photothermographic material having a moisture-proof layer composed of an emulsion and an organic matting agent having an average particle size of 0.5 to 20 µm.

(2) The photothermographic material according to (1), wherein the moisture-proof layer has a moisture permeability of 1 to 40 g / m ² · 24 hr.

  (3) The photothermographic material according to (1) or (2), wherein the organic matting agent is a hollow particle.

  (4) The photothermographic material according to (1) or (2), wherein the organic matting agent comprises two types of matting agents having different average particle diameters.

  (5) The photothermographic material according to (1) or (2), wherein the dispersion uniformity of the organic matting agent is 60% or more.

  (6) The photothermographic material according to any one of (1) to (5), wherein the wax emulsion is paraffinic.

  (7) The photothermographic material according to any one of (1) to (6), wherein the photosensitive layer contains a nucleating agent.

  (8) The photothermographic material according to any one of (1) to (7), wherein the support is a low heat-shrinkable support.

  The heat-developable photographic light-sensitive material provided with the moisture-proof layer of the present invention has little variation in photographic performance under various environmental conditions, is excellent in scratch resistance even at high temperatures, and is useful as a heat-developable photosensitive material for printing.

  Hereinafter, the present invention will be described in more detail. First, the moisture-proof layer that is a feature of the present invention will be described in detail.

<Dampproof layer>
The moisture-proof layer of the present invention is provided in the outermost layer on the photosensitive layer side with respect to the support, and is composed of a latex, a wax emulsion, and an organic matting agent having an average particle size. The ratio of the latex and the emulsion is not particularly defined, but is preferably in the range of 100: 2 to 100: 100, and more preferably 100: 10 to 100: 50 from the viewpoint of moisture resistance, humidity resistance of photographic performance, and blocking resistance. When the amount is less than 100: 2, the moisture-proof effect is not exhibited, and the deterioration occurs. On the other hand, when the amount of wax exceeds 100: 100, the film as the moisture-proof layer tends to be weakened.

The moisture permeability of the moisture-proof layer is preferably 1 to 40 g / m ² · 24 hr. More preferably, it is 1-20 g / m < ² > * 24hr. When it is lower than 1 g / m ² · 24 hr, it is necessary to increase the wax ratio, the film as the moisture-proof layer becomes weak, and the blocking property is deteriorated. ^{On the other hand} , if it exceeds 40 g / m ² · 24 hr, the moisture-proof effect is not exhibited and the humidity resistance of the photographic performance deteriorates.

  The measuring method of moisture permeability can be measured according to JIS Z-208 (cup method).

(latex)
The type of latex used in the present invention is not particularly limited, but a synthetic resin type or synthetic rubber type latex is preferred from the viewpoint of moisture resistance due to blocking resistance and film forming property. A synthetic resin type is particularly preferable.

  The latex of 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, emulsion-polymerized, micelle-dispersed, or partially hydrophilic in the polymer molecule, and the molecular chain itself is molecular. Any of dispersed ones may be used. As for latex, “Synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki; published by Polymer Publishing Co., Ltd. (1978))”, “Application of synthetic latex (Takaaki Sugimura, Ikuo Kataoka, Junichi Suzuki, Keiji Kasahara; Polymer) Publication of publication (1993)), “Synthetic latex chemistry (Muroichi Soichi; published by Polymer publication (1970))” and the like.

  The Tg (glass transition temperature) of the polymer constituting the latex is preferably -20 to 60 ° C, more preferably 0 to 50 ° C. When it is lower than −20 ° C., fluidity is generated in the membrane and the blocking property is deteriorated. On the other hand, when the temperature exceeds 60 ° C., the film forming property is deteriorated, the moisture-proof effect is not exhibited, and the humidity resistance of the photographic performance is deteriorated. The Tg of the latex is Bull. Am. Phys. Soc. T. described in G. The numerical value calculated | required by calculation by the method of Fox is shown. In the case of using a mixture of a plurality of latexes, it is calculated by adding the mass ratio of the constituent latexes.

  The average particle size of the dispersed particles of latex is preferably in the range of about 1 to 50,000 nm, more preferably about 5 to 1,000 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 latex may be a so-called core / shell type latex other than a normal uniform latex. In this case, it may be preferable to change the Tg and the composition of the core and the shell. In addition, it is preferable to use two or more types of latex in order to achieve both film-forming properties, moisture-proof properties, and blocking properties. In this case, as with the core / shell type, it is preferable to change the Tg and composition.

  The latex is obtained by emulsion polymerization of monomers including the following ethylenically unsaturated monomers. As the emulsifier used at this time, commercially available anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants and the like can be used. Of these, it is preferable to use a reactive emulsifier in order to further improve moisture resistance. By using this reactive emulsifier, a soap-free emulsion can be obtained.

  Examples of the reactive emulsifier include sodium styrenesulfonate, sodium vinylsulfonate, and an emulsifier having various ethylenically unsaturated groups. Among these, the compound having the following structural formula shown in JP-A-58-203960 is most preferable.

In the formula, R ₁ represents a hydrocarbon group, phenyl group, amino group or carboxyl group residue, and R ₂ represents a hydrogen atom or a methyl group. AO represents an alkyleneoxy group having 2 to 4 carbon atoms, and n represents a positive number from 0 to 100. M represents a cationic group such as a metal atom or an ammonium group.

(Synthetic resin)
As synthetic resin latex, the ethylenically unsaturated monomer shown below is manufactured as a copolymer by combining a single polymer or a plurality, respectively. Examples of the ethylenically unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and (meth) acrylic. (Meth) acrylic acid alkyl esters such as heptyl acid, octyl (meth) acrylate and octadecyl (meth) acrylate; aliphatic conjugated diene monomers such as 1,2-butadiene, 1,3-butadiene, isoprene and chloroprene Ethylenically unsaturated aromatic monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene 2,4-dibromostyrene; unsaturated nitriles such as (meth) acrylonitrile; (meth) acrylic acid, crotonic acid, Maleic acid and its anhydride, fumaric acid, itaconic acid and unsaturated dicarboxylic acid monoalkyl Esters; ethylenically unsaturated carboxylic acids such as monomethyl maleate, monoethyl fumarate and mononormal butyl itaconate; vinyl esters such as vinyl acetate and vinyl propionate; vinylidene halides such as vinylidene chloride and vinylidene bromide; ) Hydroxyalkyl esters of ethylenically unsaturated carboxylic acids such as acrylic acid-2-hydroxyethyleryl, 2-hydroxypropyl acrylate; glycidyl esters of ethylenically unsaturated carboxylic acids such as glycidyl (meth) acrylate, and ( (Meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethylacrylamide, diacetone acrylimide, 2-acetoacetoxyethyl (meth) acrylate, 2-acetoacetoxypropyl (meth) acrelane And monomers capable of radical polymerization such as acetoacetoxy ester having an active methylene group such as

  Among these, those having a functional group capable of chemical bonding are preferable for improving humidity resistance and scratch resistance. Particularly preferred are those having a glycidyl group and those having an active methylene group.

  It is preferable that it is 5 to 80% of the latex component to comprise as a functional group, More preferably, it is 20 to 60%. When it is less than 5%, humidity resistance and scratch resistance are insufficient, which is not preferable. On the other hand, if it exceeds 80%, the stability of the latex deteriorates, and there is a possibility that it may be hindered by coating or the like.

(Wax emulsion)
The wax emulsion used in the present invention is obtained by emulsifying wax. Examples of the wax include paraffin wax, candelilla wax, carnauba wax, rice wax, montan wax, ceresin wax, microcrystalline wax, petrolactam, Fisher tribush wax, polyethylene wax, montan wax and derivatives thereof, and microcrystalline wax. And derivatives thereof, hardened castor oil, liquid paraffin, stearamide and the like, and paraffin wax is particularly preferable.

  The wax emulsion may be prepared by a known method. For example, a wax, a resin, a fluidizing agent, etc. may be mixed and heated to melt, and an emulsifier may be added to emulsify. Examples of the resin include rosin, a rosin ester compound, and a petroleum resin. Examples of the fluidizing agent include polyhydric alcohols and esterified products of polyhydric alcohols. After melting these mixtures, for example, surfactants such as anions, cations, and nonions, or basic compounds such as ammonia, sodium hydroxide, and potassium hydroxide, organic amines, styrene-maleic acid copolymers, and the like are added to emulsify. By doing so, a wax emulsion can be obtained.

  Wax emulsions may be used alone or in combination of two or more. The melting point of the wax emulsion by differential scanning calorimetry (DSC) is preferably 40 to 100 ° C, more preferably 50 to 80 ° C. Here, if the melting point is less than 40 ° C., the blocking property is deteriorated, which is not preferable. On the other hand, when the melting point is higher than 100 ° C., the drying of the coating film when the moisture-proof layer is provided, the wax does not sufficiently soften and does not flow, so that the moisture-proof property is impaired, and as a result, the humidity resistance deteriorates.

(Organic matting agent)
The organic matting agent used in the present invention has an average particle size of 0.5 to 20 μm. If the average particle size is smaller than 0.5 μm, the mat effect cannot be exhibited and the scratch resistance is deteriorated. On the other hand, if the average particle size is larger than 20 μm, the dispersion stability in the dispersion of the matting agent and / or the moisture-proof layer coating solution is poor, and the matting agent particles aggregate, which is not preferable. More preferably, it is 1-15 micrometers, More preferably, it is 2-10 micrometers.

  The organic matting agent is effective because the difference in expansion from the moisture-proof layer during heat development is smaller than that of the inorganic matting agent, so that it can follow the distortion during transportation and become difficult to scratch. Estimated.

  The average particle size referred to here is an average of samples obtained by photographing a sample with an electron microscope and measuring the diameter of each particle. The shape of the particles 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 preferred.

  Examples of the resin constituting the matting agent include acrylic resins, polyester resins, polyurethane resins, vinyl chloride resins, vinylidene chloride resins, rubber resins (SBR rubber, NBR rubber, etc.), vinyl acetate resins, polyolefin resins, polyvinyl acetal resins, Examples thereof include pulverized and classified products such as polymer compounds such as starch. As the organic compound matting agent, a polymer compound synthesized by a suspension polymerization method or a polymer compound made spherical by a spray drying method or a dispersion method can be used.

  The resin may be a homopolymer obtained by polymerizing a single monomer or a copolymer obtained by polymerizing two or more kinds of polymers. The polymer may be linear or branched and may be further crosslinked.

  Next, specific examples of the polymer used for the matting agent of the organic compound are shown.

(1) -MMA (100)-
(2) -MMA (95) -AA (5)-
(3) -2EHA (30) -MMA (50) -St (15) -MAA (5)-
(4) -BR (50) -St (47) -AA (3)-
(5) -BR (40) -DVB (10) -St (45) -MAA (5)-
(6) -VC (70) -MMA (25) -AA (5)-
(7) -VDC (60) -MMA (35) -MAA (5)-
(8) -PS (100)-
(9) -PS (80) -MMA (20)-
(10) -PS (95) -AA (5)-
(11) -PS (80) -MMA (20) -MAA (5)-
In the above, MMA is methyl methacrylate, AA is acrylic acid, 2EHA is 2-ethylhexyl acrylate, St is styrene, MAA is methacrylic acid, BR is butadiene, DVB is divinylbenzene, VC is vinyl chloride, and VDC is a structural unit of vinylidene chloride. The numerical value in parentheses is% by mass.

  The matting agent of the present invention preferably has a dispersion uniformity of 60% or more. The dispersion uniformity referred to here is the ratio (%) of particles falling within ± 10% of the average particle diameter. When the dispersion uniformity is 60% or more, the mat effect can be sufficiently exhibited, and the scratch resistance is improved. More preferably, it is 80% or more, and particularly preferably 90% or more.

  In the present invention, it is preferable that the moisture-proof layer contains at least two kinds of matting agents having different average particle diameters. It is preferable to contain two or more kinds of matting agents having different average particle diameters because it can cope with scratch resistance in each device used in the production process and the printing process.

  In order to exert the above effect, the average particle diameter of one matting agent is 0.5 to 6 μm, more preferably 1 to 5 μm, and the average particle diameter of the other matting agent is 6 to 20 μm, more preferably 8 to A thickness of 15 μm is particularly preferable.

  The matting agent is preferably hollow particles. Hollow particles refer to those having one or more voids (hollow) within the particle shape. When the matting agent is hollow, the matting effect is easily exerted compared to non-hollow particles, and the scratch resistance is effective.

  Any method may be used for the production of the hollow matting agent, and for example, the methods described in JP-A-6-248812, JP-A-7-102024, JP-A-8-134160 and the like can be used. The porosity of the hollow matting agent is preferably in the range of 20 to 90% in the particles for the photothermographic material of the present invention, more preferably 40 to 80%. The porosity is taken with a transmission electron microscope, 100 particles are randomly selected from the photograph, the particle outer diameter and inner pore diameter are measured, the number average is obtained, and the average particle outer diameter and average inner diameter are determined. What is necessary is just to obtain | require each volume from a hole diameter and to express with the ratio.

  The organic matting agent is preferably contained in a mass ratio of 0.1 to 30% with respect to the total binder (latex and wax emulsion) of the moisture-proof layer. If the mass ratio is less than 0.1%, the mat effect cannot be exhibited and the scratch resistance is deteriorated. On the contrary, if the mass ratio is larger than 30%, the dispersion stability in the matting agent dispersion and / or the moisture-proof layer coating solution is poor, and the matting agent particles are agglomerated, which is not preferable. More preferably, it is 0.5-20 mass%, More preferably, it is 1-10 mass%.

(Other additives)
The moisture-proof layer preferably contains a fluorine-based surfactant in order to adjust coating properties and charging properties. The fluorine-based surfactant may be any of anionic, cationic, and nonionic, and among them, an anionic one is preferable. These active agents may be low molecular compounds or high molecular compounds.

  A cross-linking agent may be used for the moisture-proof layer. By using the crosslinking agent in combination with the latex and the wax emulsion, the moisture resistance is improved and the humidity resistance is improved. Examples of the crosslinking agent that can be used include various crosslinking agents conventionally used for photographic materials, such as aldehyde, epoxy, ethyleneimine, vinylsulfone, and the like described in JP-A-50-96216. Examples include sulfonic acid ester-based, acryloyl-based, and carbodiimide-based crosslinking agents.

  A matting agent can also be used to improve the scratch resistance of the moisture-proof layer. The fine particles added as the matting agent are generally fine particles of an organic or inorganic compound that is insoluble in water, and any of them can be used. For example, U.S. Pat. Nos. 1,939,213, 2,701,245, 2,322,037, 3,262,6782, 3,539,344, 3,767,448, etc. 1, 260,772, 1,192,241, 3,257,206, 3,370,951, 3,523,022, 3, Those well known in the art such as the inorganic matting agent described in No. 769,020 can be used.

  The above matting agents can be used by mixing different kinds of substances as required. The size and shape of the matting agent are not particularly limited, and those having an arbitrary particle size can be used. In practice, it is preferable to use one having a particle size of 0.1 to 30 μm. The particle size distribution of the matting agent may be narrow or wide. On the other hand, since the matting agent greatly affects the haze and surface gloss of the photosensitive material, the particle size, shape, and particle size distribution should be brought into a state as needed during the preparation of the matting agent or by mixing a plurality of matting agents. Is preferred.

<Photosensitive layer>
Next, organic silver salt grains, silver halide grains, a reducing agent and the like contained in the photosensitive layer of the photothermographic material of the invention will be described in order.

(Organic silver salt particles)
The organic silver salt contained in the photosensitive layer is a reducible silver source, and silver salts of organic acids and heteroorganic acids containing a reducible silver ion source, particularly long chains (10-30, preferably 5-25). Aliphatic carbonic acid and nitrogen-containing heterocyclic carboxylic acid. Also useful are organic or inorganic silver salt complexes where the ligand has a total stability constant for silver ions of 4.0-10.0. Examples of suitable silver salts are described in Research Disclosure (hereinafter abbreviated as RD) 17029 and 29963, and include the following.

  Salts of organic acids (gallic acid, succinic acid, behenic acid, stearic acid, palmitic acid, lauric acid, etc.); silver carboxyalkylthiourea salts (1- (3-carboxypropyl) thiourea, 1- (3-carboxyl) Propyl) -3,3-dimethylthiourea etc.); Silver complex of polymer reaction product of aldehyde and hydroxy-substituted aromatic carboxylic acid (aldehydes such as formaldehyde, acetaldehyde, butyraldehyde and salicylic acid, benzylic acid 3,5- Dihydroxybenzoic acid, silver complex of reaction products with hydroxy-substituted acids such as 5,5-thiodisalicylic acid); Silver salts or complexes of thiones (3- (2-carboxyethyl) -4-hydroxymethyl-4 -Thiazoline-2-thione and 3-carboxymethyl-4-methyl-4-thiazoline-2-thione) Nitric acid and silver complex or salt selected from imidazole, pyrazole, urazole, 1,2,4-thiazole and 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole) Silver salts such as saccharin and 5-chlorosalicylaldoxime; silver salts of mercaptides.

  Preferred silver sources are silver behenate, silver arachidate or silver stearate.

  The organic silver salt can be obtained by mixing a water-soluble silver compound and a compound that forms a complex with silver. The normal silver mixing method, the reverse mixing method, the simultaneous mixing method, and the control described in JP-A-9-127643. A dodder jet method or the like is preferably used. For example, after an alkali metal salt (sodium hydroxide, potassium hydroxide, etc.) is added to an organic acid to produce an organic acid alkali metal salt soap (sodium behenate, sodium arachidate, etc.), Organic silver salt crystals are prepared by adding silver nitrate and the like. At that time, silver halide grains may be mixed.

(Silver halide grains)
The silver halide grains contained in the photosensitive layer function as an optical sensor. In order to suppress white turbidity after image formation and to obtain good image quality, it is preferable that the average particle size is small, and the average particle size is preferably 0.03 μm or less, more preferably 0.01 to 0.03 μm. It is. The silver halide grains are produced at the same time as the preparation of the organic silver salt, or are prepared by mixing the silver halide grains at the time of preparing the organic silver salt, so that the silver halide grains are fused to the organic silver salt. It is preferable to form silver halide grains to form so-called in situ silver of fine grains. In addition, the measuring method of the average grain diameter of silver halide grains was taken at 50000 times with an electron microscope, the long side and the short side of each silver halide grain were measured, and 100 grains were measured and averaged. The average particle size is taken.

  Here, the grain size 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. In the case of non-normal crystals, for example, in the case of spherical, rod-like or tabular grains, it means the diameter when considering a sphere equivalent to the volume of silver halide grains. The silver halide grains are preferably monodispersed. The monodispersion here means that the monodispersity obtained by the following formula is 40% or less. The particles are more preferably 30% or less, and particularly preferably 0.1 to 20%.

Monodispersity = (standard deviation of particle size) / (average value of particle size) × 100
In the present invention, the silver halide grains are more preferably monodisperse grains having an average grain diameter of 0.01 to 0.03 [mu] m, and the graininess of the image is also improved by using this range.

  The shape of the silver halide grains is not particularly limited, but the ratio occupied by the Miller index [100] plane is preferably high, and this ratio is 50% or more, further 70% or more, particularly 80% or more. preferable. The ratio of the Miller index [100] plane is calculated by using the adsorption dependency between the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

  Another preferred silver halide grain shape is a tabular grain. The term “tabular grains” as used herein refers to those having an aspect ratio = r / h of 3 or more when the square root of the projected area is the grain size r μm and the thickness in the vertical direction is h μm. Among them, the aspect ratio is preferably 3 to 50. Moreover, it is preferable that a particle size is 0.03 micrometer or less, Furthermore, 0.01-0.03 micrometer is preferable. These production methods are described in US Pat. Nos. 5,264,337, 5,314,798, 5,320,958 and the like, and the desired tabular grains can be easily obtained. When these tabular grains are used, the sharpness of the image is further improved.

  The composition of the silver halide grains is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide. The photographic emulsion used in the present invention is P.I. By Glafkides; Chimie et Physique Photographic (published by Paul Montel, 1967), G. F. By Duffin; Photographic Emulsion Chemistry (published by The Focal Press, 1966), V.C. L. It can be prepared using the method described in Zelikman et al; Making and Coating Photographic Emulsion (published by The Focal Press, 1964) and the like.

  The silver halide grains used in the present invention preferably contain metal ions or complex ions belonging to groups 6 to 10 of the periodic table of elements for improving illuminance failure and adjusting gradation. As the metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, and Au are preferable.

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

  The silver halide grains in the present invention are preferably chemically sensitized. Preferred chemical sensitization methods include sulfur sensitization method, selenium sensitization method, tellurium sensitization method, noble metal sensitization method such as gold compound, platinum, palladium, iridium compound and reduction as well known in the art. A sensitization method can be used.

In order to prevent devitrification of the photothermographic material, the total amount of silver halide grains and organic silver salt is 0.3 to 2.2 g per 1 m ² in terms of silver amount, and 0.5 to 1.5 g. Is more preferable. By setting this range, a high-contrast image can be obtained. Further, the amount of silver halide with respect to the total amount of silver is 50% or less, preferably 25% or less, more preferably 0.1 to 15% in terms of mass ratio.

  The silver halide grains in the present invention have a maximum light absorption at 350 to 450 μm, and may not particularly contain a sensitizing dye, but may be contained if necessary.

(Reducing agent)
Examples of suitable reducing agents contained in the photosensitive layer of the photothermographic material include US Pat. Nos. 3,770,448, 3,773,512, 3,593,863, and RD17029 and the like. The following are mentioned.

  Aminohydroxycycloalkenone compounds (2-hydroxy-3-piperidino-2-cyclohexenone and the like); aminoreductones esters (piperidinohexose reductone monoacetate and the like) as precursors of the reducing agent; N-hydroxyurea Derivatives (such as Np-methylphenyl-N-hydroxyurea); hydrazones of aldehydes or ketones (such as anthracene aldehyde phenylhydrazone); phosphoramidophenols; phosphoramidoanilines; polyhydroxybenzenes (hydroquinone, t -Butylhydroquinone, i-propylhydroquinone and (2,5-dihydroxy-phenyl) methylsulfone, etc.); sulfhydroxamic acids (benzenesulfurhydroxamic acid, etc.); sulfonamidoanilines (4- (N-methanesulfonamido) aniline etc.); 2-tetrazolylthiohydroquinones (2-methyl-5- (1-phenyl-5-tetrazolylthio) hydroquinone etc.); tetrahydroquinoxalines (1,2,3 Amidooximes; azines; combinations of aliphatic carboxylic acid aryl hydrazides and ascorbic acid; combinations of polyhydroxybenzene and hydroxylamine; reductones and / or hydrazines; hydroxanoic acids; Combinations of sulfonamidophenols; α-cyanophenylacetic acid derivatives; combinations of bis-β-naphthol and 1,3-dihydroxybenzene derivatives; 5-pyrazolones; sulfonamidophenol reducing agents; 2-phenylindane-1,3- Zeon etc .; Chroman 1,4-dihydropyridines (2,6-dimethoxy-3,5-dicarboethoxy-1,4-dihydropyridine etc.); bisphenols (bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane Bis (6-hydroxy-m-tri) mesitol, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 4,4-ethylidene-bis (2-t-butyl-6-methylphenol), etc. ), UV-sensitive ascorbic acid derivatives; hindered phenols; 3-pyrazolidones. Of these, particularly preferred reducing agents are hindered phenols.

The amount of reducing agent used is preferably 1 × 10 ⁻² to 10 mol, in particular 1 × 10 ^{−2 to} 1.5 mol, per mol of silver.

(Nucleating agent)
The nucleating agent (functioning as a high contrast agent) preferably contained in the photosensitive layer of the photothermographic material is a hydrazine compound such as RD23515 (November 1983, page 346) and the literature cited therein. U.S. Pat. Nos. 4,080,207, 4,269,929, 4,276,364, 4,278,748, 4,385,108, 4,459,347, 4,478,928, 4,560,638, 4,686,167, 4,912,016, 4,988,604, 4,994,365, 5, No. 4,041,355, No. 5,104,769, British Patent No. 2,011,391B, European Patent No. 217,310, No. 301,799, No. 356,898, JP-A-60-179734, 61-17073 No. 61-270744, 62-178246, 62-270948, 63-29751, 63-32538, 63-104047, 63-121838, 63-129337, 63-223744, 63-234244, 63-234245, 63-234246, 63-294552, 63-306438, 64-10233, JP-A-1-904439, 1-100530, 1-105941, 1-105943, 1-276128, 1-280747, 1-283548, 1-283549, 1-285940, 2- No. 2541, No. 2-77057, No. 2-139538, No. 2-196234, No. 2-196235, -198444, 2-198441, 2-198442, 2-20042, 2-221953, 2-219554, 2-285342, 2-285343, 2-289343 No. 2-302750, No. 2-304550, No. 3-37642, No. 3-54549, No. 3-125134, No. 3-184039, No. 3-240036, No. 3-240037, 3-25240, 3-280038, 3-282536, 4-511143, 4-56843, 4-84134, 2-230233, 4-96053, 4 -216544, 5-45761, 5-45762, 5-45763, 5-45764, 5-45765, 6-28 No. 9524, 9-160164, etc. can be mentioned.

  In addition, compounds represented by (Chemical Formula 1) described in JP-B-6-77138, specifically, compounds described on pages 3 and 4 of the same publication, and described in JP-B-6-93082 The compound represented by the general formula (1), specifically, compounds 1 to 38 described on pages 8 to 18 of the same publication, general formulas (4) and (5) described in JP-A-6-23049 And compounds represented by (6), specifically, compounds 4-1 to 4-10 described on pages 25 and 26 of the same publication, and compounds 5-1 to 5-42 described on pages 28 to 36. And compounds represented by general formulas (1) and (2) described in JP-A-6-289520, specifically, compounds 6-1 to 6-7 described on pages 39 and 40; Compounds 1-1) to 1-17) and 2-1) described on pages 5 to 7, and (Chemical Formula 2) and (Chemical Formula 3) described in JP-A-6-313936. Specifically, compounds described in pages 6 to 19 of the same publication, compounds represented by (Chemical Formula 1) described in JP-A-6-313951, and specifically 3 to 5 of the publication. Compounds described in the page, compounds represented by the general formula (I) described in JP-A-7-5610, specifically, compounds I-1 to I-38 described on pages 5 to 10 of the same publication. And compounds represented by formula (II) described in JP-A-7-77783, specifically, compounds II-1 to II-102 and JP-A-7-104426 described on pages 10-27 of the same publication. The compounds represented by the general formula (H) and general formula (Ha) described in the above, and specifically those described in the compounds H-1 to H-44 described on pages 8 to 15 of the same publication are used. be able to.

  Furthermore, other nucleating agents used in the present invention are compounds described on pages 33 to 53 of JP-A No. 11-316437, more preferably the following formula (1) and formulas described in JP-A No. 2000-298327. The substituted alkene compound, substituted isoxazole compound and specific acetal compound of (2) and formula (3) are used.

In the formula (1), R ¹¹ , R ¹² and R ¹³ each represent a hydrogen atom or a substituent, Z represents an electron withdrawing group or a silyl group, R ¹¹ and Z, R ¹¹ and R ¹² , R ¹² And R ¹³ and R ¹³ and Z may be bonded to each other to form a cyclic structure.

In the formula (2), R ¹⁴ represents a substituent. In the formula (3), X and Y each represent a hydrogen atom or a substituent, and A and B each represent an alkoxy group, an alkylthio group, an alkylamino group, an arylthio group, an anilino group, a heterocyclic oxy group, Represents a heterocyclic thio group or a heterocyclic amino group. In Formula (3), X and Y and A and B may be bonded to each other to form a cyclic structure.

  Detailed explanations of the above-mentioned substituents are described in paragraphs “0116” to “0147” of the same patent specification, and specific examples of compounds include C-1 to C-64 in paragraphs “0149” to “0158”. Is described.

  The amount of the nucleating agent contained in the photosensitive layer is preferably from 0.1 to 0.001 mol, more preferably from 0.05 to 0.005 mol, per 1 mol of silver.

(Other additives)
The binder used for the photosensitive layer and the non-photosensitive layer of the photothermographic material may be either a hydrophilic binder (a binder or latex that dissolves in water) or a hydrophobic binder (a binder that dissolves in an organic solvent). Are preferably binders that are soluble in the same solvent system. For example, the binder of each layer of the photosensitive layer, the intermediate layer, and the protective layer is preferably an organic solvent-based binder or a hydrophilic binder.

  The binder used for each layer is transparent or translucent and generally colorless, and natural polymers, synthetic monopolymers and copolymers, and other media that form films are used. Specific examples of the binder include, for example, water-soluble binders such as gelatin, gum arabic, poly (vinyl alcohol), hydroxyethyl cellulose, casein, starch, cellulose acetate, cellulose acetate butyrate, polyvinyl pyrrolidone, polyacrylic acid, polymethyl Methacrylic acid, polyvinyl chloride, polymethacrylic acid, copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), polyvinyl acetals (polyvinyl formal and polyvinyl butyral), polyesters, polyurethanes , Hydrophobic binders such as phenoxy resin, polyvinylidene chloride, polyepoxides and polycarbonate, preferably polyvinyl butyral, cellulose acetate, cellulose Hydrophobic binders such as sacetate butyrate, polyester, polycarbonate, polyacrylic acid, and polyurethane, especially hydrophobic binders such as polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, and polyester, and monomers of those binder resins are emulsified. Examples thereof include latex obtained by polymerization in water by a combination method or a suspension polymerization method.

  As the main solvent for dissolving the hydrophobic binder, for example, alcohols (methanol, ethanol, propanol, etc.), ketones (acetone, methyl ethyl ketone, etc.) dimethylformamide, dimethyl sulfoxide, methyl cellosolve, etc. are preferably used.

  The Tg of the binder of the photosensitive layer is preferably 40 ° C. or higher. Preferably it is 40-120 degreeC, More preferably, it is 40-100 degreeC, Most preferably, it is 40-80 degreeC. When the temperature is lower than 40 ° C., the developability is increased, and the sensitivity increase (character line width) under high humidity is large and not preferable. On the other hand, when the temperature is higher than 120 ° C., the temperature becomes almost the same as the heat development temperature, so that the heat transfer is delayed and the developability is lowered.

  In order to control the amount of light reaching the photosensitive layer or the wavelength distribution, a filter dye layer may be formed on the same side as the photosensitive layer, or an auxiliary layer such as an antihalation dye layer, a so-called backing layer, may be formed on the opposite side. The photosensitive layer may contain a dye or a pigment. In addition to the binder and the matting agent, these auxiliary layers may contain a slipping agent such as a polysiloxane compound, wax, or liquid paraffin.

  In the photothermographic material of the present invention, various surfactants are used as coating aids, and among these, fluorine surfactants are preferably used for improving charging characteristics and preventing spotted coating failures. It is done.

  The photosensitive layer of the photothermographic material of the present invention may be composed of a plurality of layers, and in order to adjust the gradation, a multi-layer structure such as a high sensitivity layer / low sensitivity layer or a low sensitivity layer / high sensitivity layer is used. Also good.

  An example of a suitable colorant used in the photothermographic material of the present invention is disclosed in RD17029. Further, an antifoggant may be used, and these additives may be added to any of the photosensitive layer, the intermediate layer, the protective layer and other forming layers.

  For the photothermographic material, for example, a surfactant, an antioxidant, a stabilizer, a plasticizer, a coating aid and the like may be used. As these additives and the other additives described above, compounds described in RD17029 (June 1978, pages 9 to 15) can be preferably used.

(Low heat shrinkable support)
The support used in the photothermographic material of the invention is preferably low in heat shrinkability. The low heat-shrinkable support is 120 ° C. corresponding to the heat development of the support in order to suppress dimensional change of the plate due to the temperature (heat) at the time of heat development when used as a photothermographic material for printing plate making. The absolute value of the dimensional change rate at 60 seconds is 0.001 to 0.06%, preferably 0.001 to 0.04%, particularly preferably 0.001 in both the MD (longitudinal) and TD (lateral) directions. It is in the range of -0.02%.

  The measurement of the dimensional change rate is performed as follows. That is, the support is marked with a certain length in the MD and TD directions at 23 ° C. and 55% RH (relative humidity), then heated to 120 ° C. for 60 seconds, and then again 23 After adjusting the humidity for 3 hours under the condition of ° C. and 55% RH, the length in each direction is measured, and the dimensional change rate is evaluated. The dimension after heating is subtracted from the dimension before heating and divided by the dimension before heating, and the dimensional change rate is expressed as a percentage as a positive value or a negative value.

  The film used as the base material of the support is preferably a thermoplastic resin, and polyester resin is particularly preferable from the viewpoint of mechanical strength, thermal dimensional stability, and transparency. More preferred are aromatic polyester resins, and specific examples include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). The thickness of these films is preferably 50 to 500 μm, more preferably 75 to 300 μm, and particularly preferably 90 to 200 μm.

  The support of the present invention can be achieved by performing the following heat treatment in order to obtain the above dimensional change rate. In the heat treatment according to the present invention, it is desirable to reduce the conveyance tension and lengthen the heat treatment time as much as possible in order to reduce the dimensional change during the subsequent heat treatment (thermal development) without hindering the progress of heat shrinkage. The treatment temperature is preferably a temperature range of Tg + 50 ° C. to Tg + 150 ° C. of the polyester film, and in that temperature range, the transport tension is preferably 9.8 kPa to 2 MPa, more preferably 9.8 to 980 kPa, and even more preferably 9.8. The processing time is preferably 30 to 10 minutes, more preferably 30 to 5 minutes. By using the above temperature range, conveyance tension range, and treatment time, the flatness of the support does not deteriorate due to a partial difference in thermal contraction of the support during heat treatment, and fine scratches due to friction with the conveyance roll, etc. Etc. can also be suppressed.

  It is also a preferred embodiment to perform longitudinal relaxation treatment and / or lateral relaxation treatment after heat setting before heat treatment. Further, the heat treatment is required at least once in order to obtain a desired rate of dimensional change, and may be performed twice or more as necessary. Further, the heat-treated polyester film is cooled after being cooled from a temperature near Tg to room temperature, and at least −5 ° C./second or more until it is lowered to room temperature across Tg in order to prevent deterioration of flatness due to cooling at this time. It is preferable to cool at a rate of

  The heat treatment time as the heat treatment condition can be controlled by changing the film conveyance speed or changing the length of the heat treatment zone. If this heat treatment time is too short, the present invention is not effective, and the thermal dimensional stability of the support is lowered. On the other hand, if it is 60 minutes or more, the flatness and transparency of the support are deteriorated, which is not preferable as a support for a photothermographic material. Further, the tension of the heat treatment can be adjusted by adjusting the torque of the winding roll and / or the feeding roll. It can also be achieved by installing a dancer roll in the process and adjusting the load applied to it. When changing the tension during heat treatment and / or cooling after heat treatment, a desired tension state may be set by installing dancer rolls before and after these processes and / or in the processes and adjusting their loads. . In addition, it is possible to effectively change the conveyance tension by vibration by reducing the span between the heat treatment rolls.

  The support of the present invention is preferably provided with an undercoat layer. When providing the undercoat layer, acrylic resin, polyester resin, acrylic-modified polyester resin, polyurethane resin, vinylidene chloride resin, polyvinyl alcohol resin, cellulose ester resin, styrene resin, gelatin and the like are preferable. If necessary, triazine-based, epoxy-based, melamine-based, isocyanate-containing isocyanates including blocked isocyanate, aziridine-based, oxazaline-based crosslinking agents, colloidal silica and other inorganic particles, surfactants, thickeners, dyes, Preservatives and the like may be added.

  It is preferable to provide an antistatic layer on the side opposite to the photosensitive layer side. The antistatic layer is composed of an antistatic agent and a binder.

A metal oxide is preferably used as the antistatic agent. As an example of the metal oxide, ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ , or a composite oxide thereof is preferable. In particular, SnO ₂ (tin oxide) is preferable from the viewpoint of miscibility with the binder, conductivity, transparency, and the like. As an example including a different element, Sb, Nb, a halogen element or the like can be added to SnO ₂ . The amount of these different elements added is preferably in the range of 0.01 to 25 mol%, particularly preferably in the range of 0.1 to 15 mol%. Tin oxide is preferably in the form of an amorphous sol or crystalline particles. In the case of water-based coating, an amorphous sol is preferable, and in the case of solvent-based coating, the form of crystalline particles is preferable. In particular, the form of an amorphous sol with an aqueous coating is preferable from the viewpoint of work handling.

  Regarding the method for producing an amorphous tin oxide sol, any method such as a method of producing tin oxide fine particles by dispersing in a suitable solvent or a method of producing from a decomposition reaction of a tin compound soluble in the solvent in a solvent, etc. But you can. On the other hand, the crystalline particles are described in detail in JP-A-56-143430 and JP-A-60-258541. These conductive metal oxide fine particles can be produced by firstly producing metal oxide fine particles by firing and heat-treating them in the presence of different atoms in order to improve conductivity, and secondly by oxidizing the metal oxides by firing. Single and combined methods such as a method in which different atoms coexist at the time of production of fine particles, and a method of introducing oxygen defects by lowering the oxygen concentration at the time of firing are used.

The average particle diameter of the primary particles of the metal oxide is preferably 0.001 to 0.5 μm, particularly preferably 0.001 to 0.2 μm. The solid amount of the metal oxide used is preferably 0.05 to ² g, more preferably 0.1 to 1 g, per 1 m ² . The volume fraction of the metal oxide in the antistatic layer is 8 to 40% by volume, preferably 10 to 35% by volume. The above range varies depending on the color, shape, composition, etc. of the metal oxide fine particles, but the above range is most preferable from the viewpoint of transparency and conductivity.

  For the binder constituting the antistatic layer, it is preferable to use the same resin as the undercoat layer. In particular, polyester, acrylic-modified polyester, acrylic resin, and cellulose ester are preferable from the viewpoint of dispersibility and conductivity of the metal oxide.

  The thickness of the antistatic layer is preferably 0.30 to 0.70 μm from the viewpoint of transparency and coating unevenness (interference unevenness). More preferably, it is 0.35-0.55 micrometer. If it is less than 0.30 μm, the desired high-temperature conductivity and the scratch resistance when the BC layer is provided deteriorate, which is not preferable. On the other hand, if it exceeds 0.70 μm, the interference unevenness becomes strong, the commercial value is deteriorated, and the transparency is deteriorated so that it cannot be put into practical use.

  As a coating method for the undercoat layer and the antistatic layer, any known coating method can be applied. For example, kiss coat method, reverse coat method, die coat method, reverse kiss coat method, offset gravure coat method, Mayer bar coat method, roll brush method, spray coat method, air knife coat method, impregnation method, curtain coat method, etc. alone or in combination To apply.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “part” in the examples represents “part by mass” and “%” represents “% by mass”.

<Preparation of support for photothermographic material>
A PET resin was obtained as follows.

<PET resin>
0.05 part of magnesium acetate hydrate was added as a transesterification catalyst to 100 parts of dimethyl terephthalate and 65 parts of ethylene glycol, and transesterification was performed according to a conventional method. To the obtained product, 0.05 part of antimony trioxide and 0.03 part of trimethyl phosphate were added. Next, the temperature was gradually raised and the pressure was reduced, and polymerization was carried out at 280 ° C. and 66.66 Pa to obtain a PET resin having an intrinsic viscosity of 0.70.

  Using the obtained PET resin, a biaxially stretched PET film with an undercoat layer was produced as follows.

<Biaxially stretched PET film with undercoat>
Pelletized PET resin is vacuum-dried at 150 ° C for 8 hours, melted and extruded from a T-die at 285 ° C in a layered form, closely contacted with electrostatic application on a cooling drum at 30 ° C, cooled and solidified, and unstretched A film was obtained. This unstretched sheet was stretched 3.3 times in the longitudinal direction at 80 ° C. using a roll type longitudinal stretching machine. The following undercoating liquid A (solid content: 4%) was applied to the obtained uniaxially stretched film by kiss coating so that the WET film thickness was 2 g / m ² on one side. Subsequently, using a tenter-type transverse stretching machine, the film was stretched to 50% of the total transverse stretching ratio in the first stretching zone 90 ° C., and further stretched to a total transverse stretching ratio of 3.3 times in the second stretching zone 100 ° C. . Subsequently, pre-heat treatment was performed at 70 ° C. for 2 seconds, and heat setting was further performed at the first fixing zone 150 ° C. for 5 seconds, and heat fixing was performed at the second fixing zone 220 ° C. for 15 seconds. Next, 5% relaxation treatment is performed in the lateral (width) direction at 160 ° C. After exiting the tenter, the relaxation treatment is performed in the longitudinal (longitudinal) direction at 140 ° C. using the peripheral speed difference of the drive roll, until the room temperature is reached. After cooling for 60 seconds, the film was released from the clip, slitted, and wound up to obtain a biaxially stretched PET film having a thickness of 125 μm. The biaxially stretched PET film had a Tg of 79 ° C.
(Undercoating liquid A)
Methyl methacrylate / ethyl acrylate / acrylic acid / methacrylic acid-2-hydroxyethyl / acrylamide copolymer (30 / 47.5 / 10 / 2.5 / 10 molar ratio; weight average molecular weight 500,000) 40 parts Compound ( G) 50 parts Polyglycerin 10 parts Finished with pure water so that the total solid content in the coating solution was 4%.

<Heat treatment of support>
Using a suspension type thermal relaxation apparatus, relaxation heat treatment was performed under the conditions of 180 ° C., conveyance tension: 230 kPa, 15 seconds, and further cooled to room temperature at 10 ° C./min, and then wound.

<Formation of antistatic layer>
An undercoat coating solution B having the following composition was applied to the heat-treated support with a wire bar so as to have a dry film thickness of 0.35 μm, and dried at 80 ° C. for 2 minutes to obtain a support with an antistatic layer.
(Undercoating liquid B)
Tin oxide sol (SnO ₂ sol synthesized by the method described in Example 1 of Japanese Examined Patent Publication No. 35-6616 was heated and concentrated so that the solid content was 8.3%, and adjusted to pH = 10 with ammonia water. 500g
Acrylic-modified polyester resin (B-1 described in JP-A-2002-156730; solid content 17.8%) 200 g
300 g of water
<Preparation of photothermographic material>
A photothermographic material was prepared according to the following procedure.

<Application on the back layer side>
The back layer coating solution 1 and the back protective layer coating solution 1 having the following composition were filtered using a filter having an absolute filtration accuracy of 20 μm before coating, respectively, and then the above-mentioned support with an antistatic layer was totalized with an extrusion coater. Simultaneous multilayer coating was performed at a rate of 50 m / min so that the wet film thickness was 60 μm, and drying was performed at 70 ° C. for 4 minutes. Note that the amount of material indicates the amount per 1 m ² .
(Back layer coating solution 1)
16.4 g of methyl ethyl ketone
Infrared dye-A 17mg
Stabilizer B-1 (Sumitomo Chemical Co., Ltd., Sumitizer BPA) 20mg
Stabilizer B-2 (Tomisorb 77 manufactured by Yoshitomi Pharmaceutical) 50mg
Cellulose acetate propylate (Eastman Chemical: CAP504-0.2) 0.5 g
1.5 g of cellulose acetate propylate (Eastman Chemical: CAP482-20)

(Back protective layer coating solution 1)
22g of methyl ethyl ketone
Fluorine-based surfactant C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₂ C ₉ F ₁₇ 22 mg
Fluorine-based surfactant C ₈ F ₁₇ SO ₃ Li 10mg
Cellulose acetate propinate (manufactured by Eastman Chemical: CAP482) 2.0 g
Silica (manufactured by Fuji Devison: Thyroid 74, average particle size 7 μm) 12 mg
<Preparation of silver halide emulsion>
Gelatin 7.5 g and potassium bromide 10 mg are dissolved in 900 ml of pure water, adjusted to a temperature of 35 ° C. and pH 3.0, 370 ml of an aqueous solution containing 74 g of silver nitrate and potassium bromide in a molar ratio of (96/4) 370 ml of an aqueous solution containing 5 × 10 ⁻⁶ mol / liter of potassium iodide and (NH ₄ ) ₂ RhCl ₅ (H ₂ O) was added over 10 minutes by the controlled double jet method while maintaining pAg 7.7. . Thereafter, 0.3 g of 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene (stabilizer) was added, the pH was adjusted to 5 with sodium hydroxide, the average particle size was 0.06 μm, and the projected diameter was A silver halide emulsion composed of cubic silver iodobromide grains having an area variation coefficient of 8% and a {100} face ratio of 86% was obtained. The emulsion was coagulated and precipitated using a gelatin flocculant, and after desalting, 0.1 g of phenoxyethanol was added to adjust the pH to 5.9 and pAg 7.5.

(Preparation of organic fatty acid silver emulsion)
10.6 g of behenic acid was placed in 300 ml of water, dissolved by heating at 90 ° C., 31.1 ml of 1 mol / L sodium hydroxide was added with sufficient stirring, and the mixture was left as it was for 1 hour. Thereafter, the mixture was cooled to 30 ° C., 7.0 ml of 1 mol / L phosphoric acid was added, and 0.01 g of N-bromosuccinimide was added with sufficient stirring. Thereafter, silver halide grains prepared in advance were added with stirring in a state heated to 40 ° C. so that the amount of silver was 10 mol% with respect to behenic acid. Further, 25 ml of a 1 mol / L silver nitrate aqueous solution was continuously added over 2 minutes, and the mixture was allowed to stand for 1 hour with stirring.

  To this emulsion, polyvinyl butyral dissolved in ethyl acetate was added and stirred sufficiently, and then allowed to stand to separate into an ethyl acetate phase containing silver behenate grains and silver halide grains and an aqueous phase. After removing the aqueous phase, silver behenate particles and silver halide particles were collected by centrifugation. Thereafter, 20 g of synthetic zeolite A-3 (spherical) manufactured by Tosoh Corporation and 22 ml of i-propyl alcohol were added, and the mixture was allowed to stand for 1 hour and then filtered. Further, 3.4 g of polyvinyl butyral and 23 ml of i-propyl alcohol were added, and the mixture was sufficiently stirred and dispersed at 35 ° C. at high speed to complete the preparation of the organic fatty acid silver emulsion.

<Application of photosensitive layer>
A photosensitive layer coating solution and a surface protective layer coating solution having the following composition were prepared, and simultaneously coated on the opposite side of the back layer of the support after the coating on the back layer surface side.
(Photosensitive layer coating solution): organic fatty acid silver emulsion indicated by the amount biasing per 1 m ² (in terms of silver) 1.4 g
Pyridinium hydrobromide perbromide 1.5 × 10 ⁻⁴ mol
Calcium bromide 1.8 × 10 ^-4 mol
2- (4-Chlorobenzoyl) benzoic acid 1.5 × 10 ⁻³ mol
Infrared sensitizing dye 1 4.2 × 10 ⁻⁶ mol
2-mercaptobenzimidazole 3.2 × 10 ⁻³ mol
2-Tribromomethylsulfonylquinoline 6.0 × 10 ⁻⁴ mol
4-methylphthalic acid 1.6 × 10 ⁻³ mol
Tetrachlorophthalic acid 7.9 × 10 ⁻⁴ mol
1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane 4.8 × 10 ⁻³ mol
Infrared dye-A 3 × 10 ⁻⁵ mol
Nucleating agent C-65 0.5 × 10 ⁻³ mol
As the solvent, methyl ethyl ketone, acetone, and methanol were appropriately used.

(Surface Protective Layer Coating Solution): Shown in an amount per 1 m ² Cellulose acetate butyrate (Eastman Chemical: CAP381-20) / Cellulose acetate propinate (Eastman Chemical: CAP504-05) = 2/8 4 g
Phthalazine 3.2 × 10 ⁻³ mol
As the solvent, methyl ethyl ketone, acetone, and methanol were appropriately used.

<Application of moisture barrier>
After preparing a moisture-proof layer coating solution so that the material shown below has a 1000 ml finish and filtering using a filter having an absolute filtration accuracy of 20 μm, the wire is coated on the surface protective layer side of the photothermographic material with a wire bar coater. The film was applied at a speed of 30 m / min so that the film thickness was 15 μm and the dry film thickness was 3 μm, and dried at 70 ° C. for 4 minutes. As shown in Table 1, ten photothermographic materials of Examples 1 to 5 and Comparative Examples 1 to 5 in which the moisture and wax of the moisture-proof layer were changed were obtained.
(Moisture-proof coating liquid)
10g of pure water
Latex-1 (solid content 30%) 438 g
Latex-2 (solid content 30%) 162g
25 g of wax emulsion (described in Table 1, 40%)
Fluorine-containing activators _{C 9 F 19 -C 6 H 4} -SO 3 Na 20mg
Matting agent (type and amount of addition shown in Table 1)
Latex-1: Styrene / butyl acrylate / glycidyl methacrylate copolymer (20/40/40) (Tg = 20 ° C.)
Latex-2: styrene / butyl acrylate / glycidyl methacrylate / acetoacetoxyethyl methacrylate copolymer (39.5 / 0.5 / 40/20) (Tg = 45 ° C.)
<Performance evaluation>
The obtained photothermographic material was evaluated as follows.

<< Evaluation of moisture permeability >>
The measurement method of moisture permeability was measured according to JIS Z-208 (cup method) with a PET film coated with a moisture-proof layer with the coated surface facing outside.

<exposure>
For each photothermographic material produced, a single channel cylindrical inner surface type laser exposure apparatus equipped with a semiconductor laser having a beam diameter (FWHM ½ of the beam intensity) of 12.56 μm, a laser output of 50 mW, and an output wavelength of 783 nm. The exposure was performed under the conditions of a mirror rotation number of 60,000 rpm and an exposure time of 1.2 × 10 ⁻⁸ seconds. The overlap coefficient at this time was 0.449, and the laser energy density on the surface of the photothermographic material was 75 μJ / cm ² .

<Heat development>
The development was performed by thermal development using a film processor model 2771 manufactured by Imation at 120 ° C. for 48 seconds. At that time, exposure was performed in a room adjusted to 23 ° C. and 50% RH, and development processing was performed in an environment of 23 ° C. and 20% RH and 23 ° C. and 80% RH, respectively.

<Evaluation of photographic performance>
A photothermographic material was prepared by preparing a sample at 23 ° C./80% RH (high humidity) for 12 hours and a sample at 23 ° C./20% RH (low humidity) for 12 hours. Width exposure was performed and heat development was performed.

  The character line width at high humidity was evaluated by measuring the difference in line width after treatment at 23 ° C./50% RH and 23 ° C./80% RH. Moreover, Dmax (maximum density) in each environment was also evaluated. Concentration measurement was performed with a Macbeth TD904 densitometer.

<< Evaluation of scratch resistance >>
As an object to be scraped, affix the surface of each sample to the flat surface with no unevenness and a hot plate heated to 120 ° C with the back of each sample facing up, and place the photosensitive layer side of the same sample in the direction of contact with the back. The distance of 10 cm was reciprocated 10 times at a pressure of 9.8 × 10 ³ Pa. This sample was evaluated according to the following criteria. C and above are practical levels.

A: There is no penetration flaw B: The level at which the transmission flaw is visible (1-2)
C: 1-2 scratches are visible D: 3-5 transparent scratches are visible E: 6-9 transparent scratches are visible F: 10 or more transparent scratches are visible The results are shown in Table 1.

  As is apparent from Table 1, it can be seen that the photothermographic material of the present invention is superior in humidity resistance and scratch resistance in photographic performance (density and sensitivity) as compared with the comparative photothermographic material.

Claims (8)

In a photothermographic material having a photosensitive layer containing organic silver salt grains, silver halide grains and a reducing agent on a support, latex, wax emulsion and average are formed on the outermost layer on the photosensitive layer side of the support. A photothermographic material having a moisture-proof layer composed of an organic matting agent having a particle size of 0.5 to 20 µm. ^{2. The} photothermographic material according to claim 1, wherein the moisture-proof layer has a moisture permeability of 1 to 40 g / m ² · 24 hr. 3. The photothermographic material according to claim 1, wherein the organic matting agent is a hollow particle. 3. The photothermographic material according to claim 1, wherein the organic matting agent is composed of two kinds of matting agents having different average particle diameters. 3. The photothermographic material according to claim 1, wherein a dispersion uniformity of the organic matting agent is 60% or more. 6. The photothermographic material according to claim 1, wherein the wax emulsion is paraffinic. 7. The photothermographic material according to claim 1, wherein the photosensitive layer contains a nucleating agent. 8. The photothermographic material according to claim 1, wherein the support is a low heat-shrinkable support.