JP2005338127A - Silver salt photothermographic dry imaging material and image forming method for the silver salt photothermographic dry imaging material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silver salt photothermographic dry imaging material which contains a photosensitive emulsion having high sensitivity, low fog, a high maximum density, a good silver tone, excellent raw stock preservability and excellent light stability of an image, can maintain high sensitivity and low fog particularly even in long-term raw storage, and has excellent light stability of an image after heat development, and to provide an image forming method for the silver salt photothermographic dry imaging material. <P>SOLUTION: The silver salt photothermographic dry imaging material contains photosensitive silver halide grains sensitized with a spectral sensitizing dye, non-photosensitive silver salt of aliphatic carboxylic acid particles, a silver ion reducing agent, a binder and a crosslinking agent, wherein the photosensitive silver halide grains are surface latent image type silver halide grains before heat development, convert to internal latent image type silver halide grains after heat development, and lose their sensitivity by spectral sensitization with the spectral sensitizing dye after heat development because the spectral sensitizing dye is thermally oxidized or thermally decomposed in heat development. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a silver salt photothermographic dry imaging material and an image forming method of a silver salt photothermographic dry imaging material using the same.

  Conventionally, in the fields of medical treatment and printing plate making, waste liquids resulting from wet processing of image forming materials have been a problem in terms of workability. In recent years, reduction of processing waste liquids is strongly desired from the viewpoint of environmental conservation and space saving. It is rare. Accordingly, attention has been paid to a technique relating to a photothermographic material that can be efficiently exposed by a laser imager and can form a clear black image with high resolution.

  Examples of this technique include US Pat. Nos. 3,152,904, 3,487,075 and D.C. As described in Morgan, “Dry Silver Photographic Materials” (Handbook of Imaging Materials, Marcel Dekker, Inc. page 48, 1991), etc. A silver salt photothermographic dry imaging material (also referred to as a photothermographic material) containing photosensitive silver halide grains, a reducing agent and a binder is known.

  However, the photothermographic material has the disadvantage that the pre-development of the photosensitive material is remarkably worse than the photosensitive material for wet processing because all the materials related to development are incorporated in the photosensitive material.

  In addition, when heated to a high temperature (for example, 80 ° C. or higher) after exposure, silver is generated through a redox reaction between a reducible silver source (functioning as an oxidizing agent) and the reducing agent. 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 areas provides a black image that contrasts with the unexposed areas and forms an image. In addition, a photothermographic material using silver iodide (AgI) has been disclosed to improve image light resistance stability after development (see, for example, Patent Document 1 and Patent Document 2). Sensitivity and low fog level have not been achieved.

  Since the photosensitive silver halide grains of the photothermographic material remain even after heat development, it is necessary that the image light stability after heat development is excellent. That is, in the exposure before heat development, a latent image that can function as a catalyst for a development reaction (reduction reaction of silver ions by a silver ion reducing agent) is formed on the surface of the silver halide grains, and the exposure after the heat development process has passed. Then, it is preferable that the silver halide grain has a latent image formed on the surface thereof by suppressing the latent image by forming a larger number of latent images inside the surface of the silver halide grain. Heretofore, silver halide grains (latent silver halide grains in heat conversion) whose latent image forming function changes before and after heat development processing have not been known. That is, generally, when the photosensitive silver halide grains are exposed, the silver halide grains themselves or the spectral sensitizing dye adsorbed on the surface of the photosensitive silver halide grains is photoexcited and can move freely. Electrons are generated, and these electrons are competitively trapped (captured) by an electron trap (photosensitive center) existing on the surface of the silver halide grain or an electron trap inside the grain. Therefore, if there are more chemical sensitization centers (chemical sensitization nuclei) and dopants effective as electron traps on the surface than the inside of the silver halide grains, a latent image is preferentially formed on the surface and development is possible. It becomes. Conversely, if there are more chemical sensitization centers (chemical sensitization nuclei) and dopants that are effective as electron traps than the surface of the silver halide grains and there is an appropriate number of them, a latent image is preferentially formed inside and developed. It becomes difficult. In other words, in the former case, the surface sensitivity is higher than in the interior, and in the latter case, the surface sensitivity is lower than in the interior (for example, see Non-Patent Document 1 and Non-Patent Document 2). However, none of the techniques disclosed in these documents are suitable for silver salt photothermographic dry imaging materials.

Therefore, there is a technology for providing a silver salt photothermographic dry imaging material containing a photosensitive emulsion with high sensitivity, low fog, high maximum density, good silver color tone, excellent raw storage stability, and excellent image light stability. It was desired. In particular, there has been a demand for a technique for providing a silver salt photothermographic dry imaging material that can maintain high sensitivity and low fog even when stored raw for a long period of time and that has excellent image light stability.
JP 2003-91052 A JP 2003-140294 A T.A. H. Edited by James “The Theory of the Photographic Process”, 4th edition, Macmillan Publishing Co. , Ltd., Ltd. 1977 Japan Photographic Society, “Basics of Photographic Engineering (Silver Salt Photography), Corona, 1979

  The present invention has been made in view of the above-mentioned problems. The object of the present invention is to provide a photosensitive film having high sensitivity, low fog, high maximum density, good silver tone, excellent raw storage, and excellent image light resistance. The present invention provides a silver salt photothermographic dry imaging material containing a light-sensitive emulsion and an image forming method for the silver salt photothermographic dry imaging material. In particular, high sensitivity and low fog can be maintained even when stored for a long period of time. Another object of the present invention is to provide a silver salt photothermographic dry imaging material excellent in image light stability after heat development and an image forming method of the silver salt photothermographic dry imaging material.

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

(Claim 1)
In a silver salt photothermographic dry imaging material containing photosensitive silver halide grains sensitized with a spectral sensitizing dye, non-photosensitive aliphatic carboxylic acid silver salt particles, a silver ion reducing agent, a binder and a crosslinking agent, The photosensitive silver halide grains are surface latent image type silver halide grains before thermal development, and are converted into inner latent type silver halide grains after thermal development, and the spectral sensitizing dye is oxidized by heat during thermal development. Alternatively, a silver salt photothermographic dry imaging material, wherein the spectral sensitization sensitivity due to the spectral sensitizing dye disappears after thermal development by thermal decomposition.

(Claim 2)
The silver salt according to claim 1, wherein the spectral sensitizing dye is at least one selected from spectral sensitizing dyes represented by the following general formulas [Ia] to [Id]: Photothermographic dry imaging material.

[Wherein Z ₁₁ , Z ₁₂ , Z ₂₁ , Z ₂₂ , Z ₃₁ , Z ₄₁ and Z ₄₂ are each necessary to complete a monocyclic or condensed 5- or 6-membered nitrogen-containing heterocycle. Q ₃₁ , Q ₃₂ and Q ₄₁ each represents an oxygen atom, a sulfur atom, a selenium atom or —N (R) —, wherein R is an alkyl group, an aryl group or a heterocyclic ring. Represents a group. R ₁₁ , R ₁₂ , R ₂₁ , R ₂₂ , R ₃₁ , R ₄₁ and R ₄₃ each represent an aliphatic group, and R ₃₂ , R ₃₃ and R ₄₂ each represent an alkyl group, an aryl group or a heterocyclic ring. Represents a group. _{R 13, R 14, R 15} , R 16, R 17, R 23, R 24, R 25, R 26, R 27, R 28, R 29, R 34, R 35, R 36, R 37, R 38 , R ₃₉ , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ and R ₄₉ are each a hydrogen atom, a substituted or unsubstituted alkyl group, alkoxyl group, aryloxy group, aryl group, —N ( W ₁ , W ₂ ), —SR or a heterocyclic group. Here, R represents an alkyl group, an aryl group, or a heterocyclic group, W ₁ and W ₂ each represents a substituted or unsubstituted alkyl group or aryl group, and W ₁ and W ₂ are connected to each other to form 5 It is also possible to form a 6-membered or 6-membered nitrogen-containing heterocycle. R ₁₁ and R _13, R ₁₄ and R _16, R ₁₇ and R _12, R ₂₁ and R _23, R ₂₄ and R _26, R ₂₅ and R _27, R ₂₆ and R _28, R ₂₂ and R _29, R ₃₁ And R ₃₄ , R ₃₅ and R ₃₇ , R ₄₁ and R ₄₄ , R ₄₅ and R _47, and R ₄₉ and R ₄₃ can be connected to each other to form a 5-membered or 6-membered ring. X ₁₁ , X _21, and X ₄₁ each represent an ion required to cancel the charge in the molecule, and m 11, m _21, and m ₄₁ each represent the number of ions required to cancel the charge in the molecule. n11, n12, n21, n22, n31, n41, and n42 each represent 0 or 1, and l31, l32, l33, l41, l42, and l43 each represent 0 or 1. ]
(Claim 3)
The spectral sensitizing dye is a spectral sensitizing dye having an oxidation potential of less than 1 volt and a difference between an oxidation potential and a reduction potential of 2 volts or more. Silver salt photothermographic dry imaging material.

(Claim 4)
4. The silver salt photothermographic dry imaging material according to claim 1, wherein the photosensitive silver halide grains have an average equivalent-circle diameter of 10 to 90 nm.

(Claim 5)
The silver salt photothermographic dry imaging material according to any one of claims 1 to 4, further comprising a water-soluble binder.

(Claim 6)
Image formation of a silver salt photothermographic dry imaging material, wherein the silver salt photothermographic dry imaging material according to any one of claims 1 to 5 is exposed to light having a wavelength of 700 nm or less to form an image. Method.

(Claim 7)
The silver salt photothermographic dry imaging material according to claim 1, wherein the silver salt photothermographic dry imaging material according to claim 1 is exposed to light, heated at 80 to 150 ° C., and developed in 5 to 20 seconds. Image forming method of imaging material.

  According to the present invention, there is provided a silver salt photothermographic dry imaging material containing a photosensitive emulsion having high sensitivity, low fog, high maximum density, good silver tone, excellent raw storage, and excellent image light stability. Can be provided. In particular, it is possible to provide a silver salt photothermographic dry imaging material that can maintain high sensitivity and low fog even when stored raw for a long period of time and is excellent in image light stability.

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

  The silver salt photothermographic dry imaging material of the present invention comprises a photosensitive silver halide particle, a non-photosensitive aliphatic carboxylic acid silver salt particle, a silver ion reducing agent, a binder and a crosslinking agent that have been sensitized with a spectral sensitizing dye. In the silver salt photothermographic dry imaging material containing, the photosensitive silver halide grains are surface latent image type silver halide grains before thermal development, and after thermal development, are converted into inner latent type silver halide grains, and One characteristic is that the spectral sensitizing dye loses its spectral sensitizing dye after thermal development by being oxidized or thermally decomposed by heat during thermal development.

  The spectral sensitizing dye is preferably at least one selected from spectral sensitizing dyes represented by the following general formulas [Ia] to [Id].

  The spectral sensitizing dye is preferably a spectral sensitizing dye having an oxidation potential of less than 1 volt and a difference between the oxidation potential and the reduction potential of 2 volts or more.

  In the present invention, “the spectral sensitizing dye loses its spectral sensitization sensitivity after thermal development due to thermal oxidation or thermal decomposition during thermal development”. It means that only the intrinsic sensitivity of photosensitive silver halide grains exists due to oxidation or thermal decomposition with heat during thermal development.

  Various additives such as a photosensitive silver halide, an organic fatty acid silver salt, a binder, a spectral sensitizing dye, and a crosslinking agent used in the photothermographic material of the present invention, coating techniques, and exposure / development conditions will be described in order.

(Photosensitive silver halide grains)
The photosensitive silver halide grain according to the present invention is a surface latent image type silver halide grain before thermal development and is changed to an internal latent type silver halide grain after thermal development. The photosensitive silver halide grains can be obtained by chemical sensitization during grain growth.

  The photosensitive silver halide grains used in the present invention are silver halide grains that have been chemically sensitized (reduction sensitization, chalcogen sensitization, noble metal sensitization, provision of an internal electron trapping dopant after heat development, etc.). Particularly preferred is chemical sensitization inside the silver halide grains. In the present invention, the inside of a silver halide grain refers to a portion from 0 to 50 mol% from the volume center of one silver halide grain. Preferably it is 10-35 mol%.

  In general, as a specific compound for reduction sensitization, for example, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivative, borane compound, silane compound, polyamine compound and the like are used in addition to ascorbic acid and thiourea dioxide. be able to. Further, reduction sensitization can be performed by aging while maintaining the pH during particle formation at 6.5 or more and 9.5 or less.

  In the present invention, the chalcogen releasing agent is preferably a chalcogen releasing agent represented by the following general formula (C-1) or (C-2). The pH when growing the core portion of the particles of the present invention is 4.0-10.0. Preferably, chemical sensitization is performed at pH 5.5 to 8.0. Since the chalcogen release agent represented by the general formula (C-1) or (C-2) can control the chalcogen nucleation effect depending on the pH, it suppresses the formation of large fog nuclei on the surface of the silver halide grains. Can do.

In formula (C-1), Z ₁ , Z ₂ and Z ₃ may be the same or different from each other, and may be an aliphatic group, an aromatic group, a heterocyclic group, —OR ₇ , —NR ₈ (R ₉ ), -SR _10, -SeR _11, a halogen atom or a hydrogen atom. R ₇ , R ₁₀ and R ₁₁ represent an aliphatic group, an aromatic group, a heterocyclic group, a hydrogen atom or a cation, and R ₈ and R ₉ represent an aliphatic group, an aromatic group, a heterocyclic group or a hydrogen atom. . Z ₁ and Z ₂ , Z ₂ and Z ₃ , Z ₃ and Z ₁ may form a ring. Chalcogen represents a sulfur atom, a selenium atom or a tellurium atom.

In formula (C-2), Z ₄ and Z ₅ may be the same or different, and are an alkyl group, an alkenyl group, an aralkyl group, an aryl group, a heterocyclic group, —NR ₁ (R ₂ ), —OR _3. or an -SR _4. R ₁ , R ₂ , R ₃ and R ₄ may be the same or different and each represents an alkyl group, an aralkyl group, an aryl group or a heterocyclic group. However, R ₁ and R ₂ may be a hydrogen atom or an acyl group. Z ₄ and Z ₅ may form a ring. Chalcogen represents a sulfur atom, a selenium atom or a tellurium atom.

  Specific examples of the chalcogen release agent represented by the general formula (C-1) or (C-2) are shown below.

  The chalcogen releasing agent represented by the general formula (C) is water or a suitable organic solvent such as alcohols (methanol, ethanol, propanol, fluorinated alcohol), ketones (acetone, methyl ethyl ketone), dimethylformamide, dimethyl sulfoxide, It can be used by dissolving in methyl cellosolve.

  In addition, using a well-known emulsification dispersion method, it is dissolved using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, or an auxiliary solvent such as ethyl acetate or cyclohexanone, and mechanically emulsified and dispersed. An object can be made and used. Furthermore, the chalcogen compound powder represented by the general formula (C) can be dispersed in water or an organic solvent by a ball mill, a colloid mill, or ultrasonic waves by a method known as a solid dispersion method.

  A thiosulfonic acid compound may be added to the silver halide emulsion of the present invention by the method shown in European Patent Publication EP293,917.

  In the photosensitive silver halide grain according to the present invention, it is preferable in terms of sensitivity and image storability that an electron trapping dopant is contained inside the silver halide grain. In addition, the dopant silver halide that functions as a hole trap during the exposure for image formation before heat development, changes in quality during heat development, and functions as an electron trap after heat development. Particles are particularly preferred.

  The electron trapping dopant used herein is an element or compound other than silver and halogen constituting silver halide, and the dopant itself has the property of trapping (capturing) free electrons, or the dopant is halogenated. It is the one in which a site such as an electron trapping lattice defect is generated by being contained in silver particles. For example, an inorganic compound or an organic compound containing a metal ion other than silver or a chalcogen (oxygen group element) such as a sulfur atom, a selenium atom, or a tellurium atom, a nitrogen atom, or a complex thereof can be given.

  Examples of metal ions or salts or complexes thereof include lead ions, bismuth ions, gold ions, etc., or lead bromide, lead nitrate, lead carbonate, lead sulfate, bismuth nitrate, bismuth chloride, bismuth trichloride, bismuth carbonate, sodium bismutate, Examples thereof include chloroauric acid, lead acetate, lead stearate, bismuth acetate and the like.

  As the compound containing a chalcogen such as a sulfur atom, a selenium atom or a tellurium atom, various chalcogen-releasing compounds generally known as a chalcogen releasing agent in the photographic industry can be used. Moreover, as an organic substance containing a chalcogen or a nitrogen atom, a heterocyclic compound is preferable. For example, imidazole, pyrazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, indazole, purine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, Tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzothiazole, indolenine, tetrazaindene, preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, thiadiazole, oxadiazole, quinoline, phthalazine, Naphthyridine, quinoxaline, quinazoline, cinnoline, tetrazole, thiazole, o Sasol, benzimidazole, benzoxazole, benzothiazole, tetrazaindene and the like.

  The above heterocyclic compound may have a substituent, and the substituent is preferably an alkyl group, alkenyl group, aryl group, alkoxyl group, aryloxy group, acyloxy group, acyl group, alkoxycarbonyl group. Aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, sulfonyl group, ureido group, phosphoric acid amide group, halogen atom, cyano group, Sulfo group, carboxyl group, nitro group and heterocyclic group, more preferably alkyl group, aryl group, alkoxyl group, aryloxy group, acyl group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfo group. Nylamino group, sulfamoyl group, carbamoyl group, ureido group, phosphoric acid amide group, halogen atom, cyano group, nitro group, heterocyclic group, more preferably alkyl group, aryl group, alkoxyl group, aryloxy group, acyl group Acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, halogen atom, cyano group, nitro group, heterocyclic group and the like.

  The silver halide grains used in the present invention include groups 6 to 11 in the periodic table so that they function as electron trapping dopants as described above or as hole trapping dopants. Transition metal ions belonging to the above may be contained by chemically adjusting the oxidation state of the metal with a ligand or the like. As the transition metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, and Pt are preferable.

  In the present invention, the above various dopants may be used alone or in combination of two or more of the same or different compounds or complexes. However, at least one kind needs to function as an electron trapping dopant at the time of exposure after heat development. These dopants may be introduced into the silver halide grains in any chemical form. In the present invention, embodiments in which doping is performed using any one of Ir or Cu complexes or salts alone are excluded from the scope of the present invention.

The preferable content of the dopant is preferably in the range of 1 × 10 ⁻⁹ to 1 × 10 mol and more preferably in the range of 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol with ^respect to 1 mol of silver. Furthermore, 1 * 10 ^{< -6} > ^-1 * 10 ^<-2> mol is preferable.

  However, since the optimum amount depends on the kind of dopant, the grain size and shape of the silver halide grains, and other environmental conditions, it is preferable to examine optimization of the dopant addition conditions according to these conditions.

  In the present invention, the transition metal complex or complex ion is preferably represented by the following general formula.

General formula [ML ₆ ] ^m
In the formula, M represents a transition metal selected from Group 6 to 11 elements in the periodic table, L represents a ligand, and m represents 0,-, 2-, 3-, or 4-. Specific examples of the ligand represented by L include halogen ions (for example, fluorine ion, chlorine ion, bromine ion, iodine ion), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aquo. Each ligand includes nitrosyl, thionitrosyl, and the like, preferably aco, nitrosyl, thionitrosyl, and the like. When an acoligand is present, it preferably occupies one or two of the ligands. L may be the same or different.

  The compounds providing these metal ions or complex ions are preferably added at the time of silver halide grain formation and incorporated into the silver halide grains. Preparation of silver halide grains, that is, nucleation, growth, physical ripening In addition, it may be added at any stage before or after chemical sensitization, but it is particularly preferably added at the stage of nucleation, growth and physical ripening, and more preferably at the stage of nucleation and growth, Most preferably, it is added at the stage of nucleation. In the addition, it may be added several times and can be added uniformly in the silver halide grains. For example, JP-A-63-29603, JP-A-2-306236, As described in JP-A-3-167545, JP-A-4-76534, JP-A-6-110146, JP-A-5-273683, etc., the particles can be contained with a distribution.

  These metal compounds can be added by dissolving in water or an appropriate organic solvent (for example, alcohols, ethers, glycols, ketones, esters, amides). A method in which an aqueous solution or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to a water-soluble silver salt solution or a water-soluble halide solution during particle formation, or the silver salt solution and the halide solution are mixed simultaneously. When adding a third aqueous solution, a method of preparing silver halide grains by a method of simultaneous mixing of three liquids, a method of introducing an aqueous solution of a required amount of a metal compound into a reaction vessel during grain formation, or a silver halide preparation There is a method of adding and dissolving another silver halide grain that has been previously doped with metal ions or complex ions. In particular, a method of adding an aqueous solution of a metal compound powder or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to the water-soluble halide solution. When added to the particle surface, a required amount of an aqueous solution of a metal compound can be charged into the reaction vessel immediately after the formation of the particle, during or after physical ripening, or at the time of chemical ripening.

  In addition, a nonmetallic dopant can also be introduce | transduced inside a silver halide by the method similar to said metallic dopant.

  In the silver salt photothermographic dry imaging material of the present invention, whether or not the dopant has an electron trapping property can be evaluated by a method generally used in the photographic industry as follows. . That is, a silver halide emulsion comprising silver halide grains doped with the above-mentioned dopant or a decomposition product thereof in silver halide grains is subjected to a photoconductivity measurement by a microwave photoconductivity measurement method or the like, and the halogenation does not contain a dopant. Evaluation can be made by measuring the degree of decrease in photoconduction with silver grains (emulsion) as a reference. Alternatively, it can be performed by a comparative experiment of the internal sensitivity and surface sensitivity of the silver halide grains.

  Alternatively, a method for evaluating the effect of the electron trapping dopant according to the present invention after preparing a silver salt photothermographic dry imaging material is, for example, under the same conditions as normal practical thermal development conditions before exposing the imaging material. A characteristic curve (sensitivity) obtained by heating, then exposing through an optical wedge with ultraviolet to visible light or spectrally sensitized light for a certain time (for example, 30 seconds), and further heat development under the same heat development conditions. The sensitivity obtained on the basis of the tomometry curve can be evaluated by comparing with the sensitivity of the imaging material using the silver halide grain emulsion not containing the electron trapping dopant. That is, it is necessary to confirm that the sensitivity of the former sample containing the silver halide grain emulsion containing the dopant according to the present invention is lower than the sensitivity of the latter sample not containing the dopant.

  In addition, when the silver salt photothermographic dry imaging material is exposed to light in the range of ultraviolet to visible light or spectrally sensitized light for a certain period of time (for example, 30 seconds) through an optical wedge and then thermally developed under normal heat development conditions. For the sensitivity of the sample obtained on the basis of the characteristic curve obtained in step 1, the sample is heated under the same conditions as normal heat development conditions before exposure, and then subjected to the same constant time and constant exposure as described above, and The sensitivity obtained based on the characteristic curve obtained by heat development under normal heat development conditions is 1/5 or less, preferably 1/10 or less, more preferably 1/20 or less.

  The particle size of the photosensitive silver halide grains is preferably small for the purpose of keeping the white turbidity after image formation low, specifically 0.20 μm or less, more preferably 0.01 μm or more and 0.00. It is 15 μm or less, more preferably 0.01 μm or more and 0.09 μm or less. The grain size here means 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. In the case of other non-normal crystals, for example, in the case of spherical grains, rod-shaped grains, etc., it means the diameter when considering a sphere equivalent to the volume of silver halide grains.

  Examples of the shape of the photosensitive silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-like grains, and potato grains. In the present invention, cubic grains and tabular grains are particularly preferred. . When tabular silver halide grains are used, the average aspect ratio is preferably 100: 1 to 2: 1, more preferably 50: 1 to 3: 1. Further, grains having rounded corners of silver halide grains can be preferably used. The surface index (Miller index) on the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the {100} plane, which has high spectral sensitizing efficiency when adsorbed by the spectral sensitizing dye, is high. preferable. The ratio is preferably 50% or more, more preferably 65% or more, and still more preferably 80% or more. The ratio of the Miller index {100} plane is a T.K. based on the adsorption dependence of {111} plane and {100} plane in the adsorption of spectral sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

  The photosensitive silver halide grains in the photothermographic material of the present invention may be used alone or in combination of two or more (for example, grains having different average grain sizes, grains having different halogen compositions, grains having different crystal habits). May be.

  The amount of the photosensitive silver halide grain used in the present invention is preferably 0.01 mol or more and 0.5 mol or less, and 0.02 mol or more and 0.3 mol per 1 mol of the organic silver salt. The following is more preferable, and 0.03 to 0.25 mol is particularly preferable. Regarding the mixing method and mixing conditions of photosensitive silver halide and organic silver salt prepared separately, the silver halide grains and organic silver salt that have been prepared respectively are mixed with a high-speed stirrer, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc. And a method of preparing an organic silver salt by mixing photosensitive silver halide grains that have been prepared at any timing during the preparation of the organic silver salt.

  Typically, a silver halide emulsion containing light-sensitive silver halide grains according to the present invention comprises a silver salt aqueous solution and a halogen in a protective colloid (a hydrophilic colloid such as gelatin is used) as a reaction mother liquor. A mixed aqueous solution is mixed, and nucleation and crystal growth are performed for preparation. A double jet method is generally used as a method for adding a halide aqueous solution or a silver salt aqueous solution. Among these, the controlled double jet method in which each component is mixed while controlling pAg and pH to perform the nucleation and crystal growth is representative. In addition, it includes various variations such as a method in which seed particles are first prepared (nucleated) and subsequently grown in the same condition or in another condition (crystal growth or ripening). Yes. In short, it is well known in the art to control the crystal habit and size in various ways by defining the mixing conditions of the silver salt aqueous solution and the halide aqueous solution in the mixing step in the protective colloid aqueous solution. Subsequent to these mixing steps, a desalting step for removing excess salts from the prepared emulsion is performed. As a desalting step, there is a flocculation method in which a silver halide grain is coagulated and precipitated together with gelatin as a protective colloid by adding a flocculant to the prepared silver halide emulsion, and this is separated from a supernatant containing salts. well known. The supernatant liquid is removed by decantation, and dissolution, flocculation, and decantation are repeated in order to remove excess salts contained in the gelatin coagulate containing silver halide grains that have been aggregated and settled. A method for removing soluble salts by ultrafiltration is also well known. This is a method of removing unnecessary low-molecular weight salts by using an ultrafiltration membrane, using a synthetic membrane that does not transmit large-sized grains such as silver halide grains and gelatin, and molecules having a large molecular weight.

  The hydrophilic colloid used in the silver halide emulsion containing the photosensitive silver halide grains according to the present invention is preferably 40 g or less per 1 mol of silver. Particularly preferably, it is 35 g or less.

  Photosensitive silver halide grains prepared by the various methods described above can also be chemically sensitized on the surface of the grains. For example, it can be chemically sensitized by a sulfur-containing compound, a gold compound, a platinum compound, a palladium compound, a silver compound, a tin compound, a chromium compound, or a combination thereof. Regarding the method and procedure of this chemical sensitization, for example, US Pat. No. 4,036,650, British Patent 1,518,850, JP-A-51-22430, JP-A-51-78319, JP-A-51- 81124 and the like. In addition, when a part of the organic silver salt is converted into photosensitive silver halide by the silver halide forming component, as described in U.S. Pat. No. 3,980,482, it is low to achieve sensitization. A molecular weight amide compound may coexist.

  The photosensitive silver halide grains according to the present invention may be added to the photosensitive layer by any method so that the silver halide grains are close to a reducible silver source (aliphatic carboxylic acid silver salt). It is preferable to arrange.

  The photosensitive silver halide grain according to the present invention is prepared in advance, and it is added at the time of preparing the aliphatic carboxylic acid silver salt grain, so that the photosensitive silver halide grain preparing step and the aliphatic carboxylic acid silver salt grain preparing Although it is possible to handle the process separately and is preferable in terms of production control, as described in British Patent 1,447,454, when preparing aliphatic carboxylic acid silver salt particles, halogen components such as halide ions By coexisting with an aliphatic carboxylate silver salt-forming component and injecting silver ions therein, silver halide grains produced almost simultaneously with the production of aliphatic carboxylate silver salt grains can be used in combination. It is also possible to prepare a silver halide grain by allowing a halogen-containing compound to act on an aliphatic carboxylic acid silver salt and converting the aliphatic carboxylic acid silver salt, and use the grain together. That is, a silver halide-forming component is allowed to act on a solution or dispersion of an aliphatic carboxylic acid silver salt prepared in advance, or a sheet material containing the aliphatic carboxylic acid silver salt, so that a part of the aliphatic carboxylic acid silver salt is removed. It can also be converted to photosensitive silver halide. The photosensitive silver halide grains according to the present invention can be phase-shifted from a water-soluble solvent to an organic solvent, and added and dispersed in a coating solution of an aliphatic carboxylic acid silver salt immediately before coating. Alternatively, the photosensitive silver halide grain according to the present invention can be prepared in an organic solvent.

  Examples of the photosensitive silver halide grain forming component include inorganic halogen compounds, onium halides, halogenated hydrocarbons, N-halogen compounds, and other halogen-containing compounds. Specific examples thereof include US Pat. No. 4,009, No. 039, No. 3,457,075, No. 4,003,749, British Patent No. 1,498,956, and JP-A Nos. 53-27027 and 53-25420. .

  Photosensitive silver halide grains produced by converting part of the aliphatic carboxylic acid silver salt into silver halide grains separately prepared as described above may be used in combination.

  These photosensitive silver halide grains, both separately prepared photosensitive silver halide grains and photosensitive silver halide grains by conversion of aliphatic carboxylic acid silver salts, were 0.001 per 1 mol of aliphatic carboxylic acid silver salt. It is preferable to use at -0.7 mol, preferably 0.03-0.5 mol.

  Separately prepared photosensitive silver halide grains are desalted by a known desalting method such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. However, it can be used without desalting.

  The spectral sensitizing dyes represented by the general formulas [Ia] to [Id] according to the present invention will be described.

  In the spectral sensitizing dyes represented by the general formulas [Ia] to [Id] according to the present invention, the spectral sensitizing dye represented by the general formula [Ia] is represented by the following general formula [I The spectral sensitizing dye represented by -e] or [If] is preferable. The spectral sensitizing dye represented by the general formula [Ib] is a spectral sensitizing dye represented by the following general formula [Ig], [Ih] or [Ii]. It is preferable.

[Wherein Y ₅₁ , Y ₅₂ , Y ₆₁ and Y ₆₂ each represent an oxygen atom, a sulfur atom, a selenium atom or — (NR ₀ ) —, wherein R ₀ represents an aliphatic group. R ₅₁ and R ₅₂ each represents an aliphatic group, and R ₆₁ represents an aliphatic group or a group of nonmetallic atoms necessary for bonding to R ₆₅ to complete a 5-membered or 6-membered condensed ring. R ₅₃ and R ₅₄ each represent a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, and R ₅₅ and R ₆₂ each represent a hydrogen atom, an alkyl group, an aryl group, a heterocyclic group, a halogen atom, an alkoxyl group, Represents an aryloxy group, an alkylthio group, an arylthio group or an amino group, and R ₆₃ and R ₆₄ are each bonded to a hydrogen atom, an alkyl group or R ₆₃ and R ₆₄ to form a 5-membered or 6-membered ring. Represents a group of nonmetallic atoms necessary for the production of R ₆₅ represents a hydrogen atom or a bond to R ₆₁ . A _{51 to} A ₅₈ and A _{61 to} A ₆₈ each represents a hydrogen atom or a substitutable group, and each of A ₅₁ and A ₅₂ , A ₅₂ and A ₅₃ , A ₅₃ and A ₅₄ , A ₅₅ and A ₅₆ , A ₅₆ And A ₅₇ , A ₅₇ and A ₅₈ and A ₆₁ and A ₆₂ , A ₆₂ and A ₆₃ , A ₆₃ and A ₆₄ , A ₆₅ and A ₆₆ , A ₆₆ and A ₆₇ , A ₆₇ and A ₆₈ They can be linked together to form a condensed naphthol ring. M ₅₁ and M ₆₁ each represent an ion required to cancel the charge in the molecule, and m 51 and m 61 each represent the number of ions required to cancel the charge in the molecule. p represents 2 or 3. ]

[Wherein Y ₇₁ , Y ₇₂ , Y ₈₁ , Y ₈₂ , Y ₉₁ and Y ₉₂ each represent an oxygen atom, a sulfur atom, a selenium atom or — (NR ₀ ) —, wherein R ₀ is an aliphatic group. Represents. R ₇₁ , R ₇₂ , R ₈₁ , R ₈₂ , R ₉₁ and R ₉₂ each represent an aliphatic group. R ₇₃ and R ₇₄ and R ₉₃ and R ₉₄ each represent a group of non-metallic atoms necessary for bonding to each other to form a 5-membered or 6-membered ring, and R ₇₅ and R ₉₅ are each a hydrogen atom Represents an alkyl group, an aryl group, a heterocyclic group, a halogen atom, an alkoxyl group, an aryloxy group, an alkylthio group, an arylthio group or an amino group. A _{71 to} A ₇₈ , A _{81 to} A ₈₈ and A _{91 to} A ₉₈ each represent a hydrogen atom or a substitutable group, A ₇₁ and A ₇₂ , A ₇₂ and A ₇₃ , A ₇₃ and A ₇₄ , A ₇₅ And A ₇₆ , A ₇₆ and A ₇₇ , A ₇₇ and A _78, A ₈₁ and A ₈₂ , A ₈₂ and A ₈₃ , A ₈₃ and A ₈₄ , A ₈₅ and A ₈₆ , A ₈₆ and A ₈₇ , A ₈₇ and A ₈₈ and A ₉₁ and A ₉₂ , A ₉₂ and A ₉₃ , A ₉₃ and A ₉₄ , A ₉₅ and A ₉₆ , A ₉₆ and A ₉₇ , A ₉₇ and A ₉₈ are linked to each other to form a condensed naphthol ring. Can be formed. M ₇₁ , M _81, and M ₉₁ each represent an ion necessary to cancel the charge in the molecule, and m 71, m 81, and m 91 each represent the number of ions required to cancel the charge in the molecule. ]
Hereinafter, the spectral sensitizing dyes represented by the general formulas [Ia] to [Ii] will be described.

In the formula [I-a] - _{[I-i], Z 11, Z 12, Z} 21, Z 22, each in Z _31, Z ₄₁ and Z _42, 5-membered or 6-membered nitrogen-containing heterocyclic represented Examples of the ring include an oxazole nucleus (for example, an oxazolidine ring, an oxazoline ring, a benzoxazole ring, a tetrahydrobenzoxazole ring, a naphthoxazole ring, a benzonaphthoxazole ring, etc.), an imidazole nucleus (for example, an imidazolidine ring, an imidazoline ring, a benzimidazole ring, Tetrahydrobenzimidazole ring, naphthimidazole ring, benzonaphthimidazole ring, etc.), thiazole nucleus (for example, thiazolidine ring, thiazoline ring, benzothiazole ring, tetrahydrobenzothiazole ring, naphthothiazole ring, benzonaphthothiazole ring, etc.), selenazole nucleus ( For example, selenazolidine , Selenazoline ring, benzoselenazole ring, tetrahydrobenzoselenazole ring, naphthoselenazole ring, benzonaphthoselenazole ring, etc.), tellurazole nucleus (eg, tellrazolidine ring, tellurazoline ring, benzotelrazole ring etc.), pyridine nucleus (eg. , Pyridine, quinoline, etc.), pyrrole nucleus (for example, pyrrolidine ring, pyrroline ring, pyrrole ring, 3,3-dialkylindolenine ring, etc.), and these rings are represented by A _{51 to} A ₉₈ described later. Any group described as a substitutable group can be substituted.

_{R 0, R 11, R 12} , R 21, R 22, R 31, R 41, R 43, R 51, R 52, R 61, R 71, R 72, R 81, R 82, R 91 and R ₉₂ In each of the aliphatic groups shown, for example, a branched or straight chain alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, iso-pentyl group) 2-ethyl-hexyl group, octyl group, decyl group, etc.), alkenyl group having 3 to 10 carbon atoms (for example, 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl) Group, 1-methyl-3-butenyl group, 4-hexenyl group and the like) and aralkyl groups having 7 to 10 carbon atoms (for example, benzyl group, phenethyl group and the like).

  Further, the above-described groups further include lower alkyl groups (for example, methyl group, ethyl group, propyl group, etc.), halogen atoms (for example, fluorine atom, chlorine atom, bromine atom, etc.), vinyl groups, aryl groups (for example, phenyl group). , P-tolyl group, p-bromophenyl group, etc.), trifluoromethyl group, alkoxyl group (for example, methoxy group, ethoxy group, methoxyethoxy group, etc.), aryloxy group (for example, phenoxy group, p-tolyloxy group, etc.) ), Cyano group, sulfonyl group (for example, methanesulfonyl group, trifluoromethanesulfonyl group, p-toluenesulfonyl group, etc.), alkoxycarbonyl group (for example, ethoxycarbonyl group, butoxycarbonyl group, etc.), amino group (for example, amino group) , Biscarboxymethylamino group, etc.), aryl group (for example, phenyl group, Ruboxyphenyl group etc.), heterocyclic group (eg tetrahydrofurfuryl, 2-pyrrolidinon-1-yl group etc.), acyl group (eg acetyl group, benzoyl group etc.), ureido group (eg ureido group, 3 -Methylureido group, 3-phenylureido group etc.), thioureido group (eg thioureido group, 3-methylthioureido group etc.), alkylthio group (eg methylthio, ethylthio group etc.), arylthio group (eg phenylthio group etc.) , Heterocyclic thio groups (for example, 2-thienylthio group, 3-thienylthio group, etc.), carbonyloxy groups (for example, acetyloxy group, propanoyloxy group, benzoyloxy group, etc.), acylamino groups (for example, acetylamino, benzoyl) Amino group, etc.), thioamide group (for example, thioacetamide group, A group such as a benzoylamino group or the like, or, for example, a sulfo group, a carboxy group, a phosphono group, a sulfate group, a hydroxy group, a mercapto group, a sulfino group, a carbamoyl group (for example, a carbamoyl group, an N-methylcarbamoyl group, N, N-tetramethylenecarbamoyl group etc.), sulfamoyl group (eg sulfamoyl group, N, N-3-oxapentamethyleneaminosulfonyl group etc.), sulfonamide group (eg methanesulfonamide, butanesulfonamide group etc.), sulfonyl An aminocarbonyl group (eg, methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl group, etc.), an acylaminosulfonyl group (eg, acetamidosulfonyl, methoxyacetamidosulfonyl group, etc.), an acylaminocarbonyl group (eg, For example, it may be substituted with a hydrophilic group such as acetamidocarbonyl, methoxyacetamidocarbonyl group, etc.), sulfinylaminocarbonyl group (for example, methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl group, etc.). Specific examples of the aliphatic group substituted with these hydrophilic groups include carboxymethyl, carboxyethyl, carboxybutyl, carboxypentyl, 3-sulfatobutyl, 3-sulfopropyl, and 2-hydroxy-3-sulfopropyl groups. 4-sulfobutyl, 5-sulfopentyl, 3-sulfopentyl, 3-sulfinobutyl, 3-phosphonopropyl, hydroxyethyl, N-methanesulfonylcarbamoylmethyl, 2-carboxy-2-propenyl, o-sulfobenzyl, Examples include groups such as p-sulfophenethyl and p-carboxybenzyl.

_{R, R 13, R 14,} R 15, R 16, R 17, R 23, R 24, R 25, R 26, R 27, R 28, R 29, R 32, R 33, R 34, R 35, _R36 , _R37 , _R38 , _R39 , _R42 , _R44 , _R45 , _R46 , _R47 , _R48 , _R49 , _R53 , _R54 , _R55 , _R62 , _R63 , _R64 , R ₇₅ and R ₉₅ each represents an alkyl group, for example, a methyl group, an ethyl group, a butyl group, an iso-butyl group, etc., and an aryl group includes monocyclic and polycyclic ones, For example, groups such as a phenyl group and a naphthyl group are exemplified, and examples of the heterocyclic group include thienyl, furyl, pyridyl, carbazolyl, pyrrolyl, indolyl and the like.

These groups can be substituted with the groups mentioned in the description of the aliphatic groups represented by R ₀ , R ₁₁ , R _{92 and the} like. Specific examples of the substituted alkyl group include 2-methoxyethyl, 2-methoxy Examples include hydroxyethyl, 3-ethoxycarbonylpropyl, 2-carbamoylethyl, 2-methanesulfonylethyl, 3-methanesulfonylaminopropyl, benzyl, phenethyl, carboxymethyl, carboxyethyl, allyl, 2-furylethyl and the like. Specific examples of the substituted aryl group include p-carboxyphenyl, pN, N-dimethylaminophenyl, p-morpholinophenyl, p-methoxyphenyl, 3,4-dimethoxyphenyl, 3,4 -Methylenedioxyphenyl, 3-chlorophenyl, p-nitrophenyl, etc. Specific examples of the heterocyclic group are, for example, 5-chloro-2-pyridyl, 5-ethoxycarbonyl-2-pyridyl, and each group such as 5-carbamoyl-2-pyridyl.

Examples of the alkyl group and aryl group represented by W ₁ and W ₂ include the groups described in the above R and others.

_{R 13, R 14, R 15} , R 16, R 17, R 23, R 24, R 25, R 26, R 27, R 28, R 29, R 34, R 35, R 36, R 37, R 38 , R ₃₉ , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ , R ₄₉ , R ₅₅ , R ₆₂ , R ₇₅ and R ₉₅ , examples of the alkoxyl group represented by each include, for example, a methoxy group and an ethoxy group , 2-methoxyethoxy group, 2-hydroxyethoxy group and the like. As the aryloxy group, for example, phenoxy group, 2-naphthoxy group, 1-naphthoxy group, p-tolyloxy group, p-methoxyphenyl group, etc. Can be mentioned.

Examples of the halogen atom represented by R ₅₅ , R ₆₂ , R ₇₅ and R ₉₅ include a fluorine atom, a chloro atom, a bromine atom and an iodine atom, and examples of the alkylthio group include a methylthio group and an ethylthio group. Examples of the arylthio group include a phenylthio group and an m-chlorophenylthio group. The amino group includes a substituted or unsubstituted group. For example, an amino group, a methylamino group, a dimethylamino group, a diethylamino group, Examples thereof include a diphenylamino group, an N, N-tetramethyleneamino group, and an N, N-pentamethyleneamino group.

R ₁₄ and R ₁₆ , R ₂₄ and R ₂₆ , R ₂₅ and R ₂₇ , R ₂₆ and R ₂₈ , R ₃₅ and R ₃₇ , R ₄₅ and R ₄₇ , R ₄₉ and R ₄₃ , R ₆₃ and R ₆₄ , R ₇₃ Examples of the condensed ring which can be formed by linking R ₇₄ and R ₉₃ and R ₉₃ and R ₉₄ to each other include 5-membered and 6-membered saturated or unsaturated condensed carbocycles. These condensed rings can be substituted at any position, and examples of the substituted group include the groups described above for the group which can be substituted with the aliphatic group.

R ₁₁ and R ₁₃ , R ₁₇ and R ₁₂ , R ₂₁ and R ₂₃ , R ₂₂ and R ₂₉ , R ₃₁ and R ₃₄ , R ₄₁ and R ₄₄ can be linked to each other as a condensed ring. Examples thereof include 5-membered and 6-membered saturated or unsaturated nitrogen-containing condensed rings.

Examples of the 5-membered or 6-membered nitrogen-containing heterocycle formed by linking W ₁ and W ₂ together with the nitrogen atom include a pyrrolidine ring, a morpholine ring, and a piperidine ring.

The substitutable groups represented by A _{51 to} A ₅₈ , A _{61 to} A ₆₈ , A _{71 to} A ₇₈ , A _{81 to} A ₈₈ and A _{91 to} A ₉₈ are each a lower alkyl group (for example, methyl group, ethyl Group, propyl group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), vinyl group, styryl group, aryl group (eg, phenyl group, p-tolyl group, p-bromophenyl group, etc.), Trifluoromethyl group, alkoxyl group (for example, methoxy group, ethoxy group, etc.), aryloxy group (for example, phenoxy group, p-tolyloxy group, etc.), carbonyloxy group (for example, acetyloxy group, propanoyloxy group, benzoyl) Oxy group, etc.), amino group (eg, amino, dimethylamino, anilino, etc.), heterocyclic group (eg, pyridyl group, pyrrolyl group, furyl group, thienyl) Imidazolyl group, thiazolyl group, pyrimidinyl group, etc.), acyl group (eg, acetyl group, benzoyl group, etc.), cyano group, sulfonyl group (eg, methanesulfonyl group, benzenesulfonyl group, etc.), carbamoyl group (eg, carbamoyl group) N, N-dimethylcarbamoyl group, morpholinocarbonyl group, etc.), sulfamoyl group (eg, sulfamoyl group, N-phenylsulfamoyl group, morpholinosulfonyl group, etc.), acylamino group (eg, acetylamino group, benzoylamino) , O-hydroxybenzoylamino group, etc.), sulfonylamino group (eg, methanesulfonylamino group, benzenesulfonylamino group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, trifluoroethoxy) A carbonyl group or the like), a hydroxyl group, a carboxyl group, or the like.

In the spectral sensitizing dyes represented by the general formulas [Ia] to [Ii], when a group having a cation or anion charge is substituted, the charges in the molecule cancel each other. Thus, a counter ion is formed with an equivalent amount of anion or cation. For example, X ₁₁ , X ₂₁ , X ₄₁ , M ₅₁ , M ₆₁ , M ₇₁ , M _81, and M ₉₁ are specific examples of cations in the ions necessary for canceling out the charges in the molecule. , Protons, organic ammonium ions (for example, triethylammonium, triethanolammonium and other ions) and inorganic cations (for example, lithium, sodium, potassium and other cations). Specific examples of acid anions include halogens Ions (for example, chlorine ions, bromine ions, iodine ions, etc.), p-toluenesulfonate ions, perchlorate ions, boron tetrafluoride ions, sulfate ions, methyl sulfate ions, ethyl sulfate ions, methanesulfonate ions, trifluoromethane Examples include sulfonate ions.

  In the spectral sensitizing dyes represented by the general formulas [Ia] to [Id], the spectral sensitizing dyes represented by the general formulas [Ie] and [If] are preferably used. Spectral sensitizing dyes represented by the above general formulas [Ig] to [Ii] are more preferably used.

  The typical spectral sensitizing dyes (compounds) represented by the above general formulas [Ia] to [Ii] are shown below, but the present invention is not limited to these compounds. .

  The above-described spectral sensitizing dyes are described in, for example, F. F. Hammer, The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dies and Related Compounds, (A. Weisserger ed. It can be easily synthesized by this method.

  Although the spectral sensitizing dye according to the present invention may be used alone, two or more kinds of spectral sensitizing dyes may be used in combination. When two or more kinds of spectral sensitizing dyes according to the present invention are combined, the spectral sensitizing dyes can be dispersed in the silver halide emulsion by the above-mentioned methods independently or in advance. Along with the spectral sensitizing dye according to the present invention, a dye having absorption in the visible range for the purpose of supersensitization, a dye having no spectral sensitizing action itself, or a substance that does not substantially absorb visible light, A substance showing supersensitization may be included in the emulsion. Useful spectral sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in Research Disclosure, 176, 17643 (published December 1978), page 23 IV. J, or JP-B-49-25500, JP-A-43-4933, JP-A-59-19032, JP-A-59-192242, JP-A-62-123454, JP-A-3-15049, JP-A-7-146527. It is described in the issue.

  The “spectral sensitizing dye having an oxidation potential of less than 1 volt and a difference between the oxidation potential and the reduction potential of 2 volts or more” according to the present invention will be described.

The photothermographic material according to claim 3 of the present invention has an oxidation potential of less than 1 volt in an image forming layer (hereinafter also referred to as a photosensitive layer or a photosensitive layer), and an oxidation potential and a reduction potential. And a spectral sensitizing dye having a value of 2 volts or more. When the spectral sensitizing dye is highly reducible, fogging is high, and fogging during storage is likely to increase. In the present invention, the time when the spectral sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from the desalting to the start of chemical ripening. The addition amount of the spectral sensitizing dye in the present invention can be set to a desired amount according to the sensitivity and fogging performance, but it is 1 × 10 ⁻⁶ mol or more per mol of silver halide in the image forming layer. The molar amount is preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻¹ mol or less.

  Those skilled in the art can easily measure the reduction potential (Ered value) and oxidation potential (Eox value) of the spectral sensitizing dye used in the present invention. For the measurement method, see A. Stanienda, “Naturwissenschaften”, 47, 353 and 512/1960, p. Delahay's “New Instrumental Methods in Electrochemistry” 1954 (published by Interscience Pullers), L. It is described in "Polaographic Technologies" 2nd edition / 1965 (published by Interscience Publishers) by Meites.

  The Ered value means a potential at which a target compound is reduced by electron injection at the cathode in voltammetry, which is considered to be approximately linearly related to the excitation energy level of the compound. ing. The value of Eox means a potential at which a target compound can extract its electrons at the anode in voltammetry, which is considered to be primarily related to the highest occupied electron energy level in the ground state of the compound. ing.

The Ered value of the spectral sensitizing dye in the present invention is 25 using a mercury dropping electrode in a 1 × 10 ⁻⁴ to 1 × 10 ⁻⁶ mol acetonitrile solution of a compound using tetranormalpropyl ammonium perchlorate as a supporting electrolyte. A voltage-current curve is obtained using an SCE (standard calomel electrode) as a reference electrode at a temperature, and determined as a half-wave potential from this curve. Further, the Eox value is determined according to the same operation as the measurement of the Ered value using a rotating platinum electrode with sodium perchlorate as a supporting electrolyte. A series of Ered and Eox values can be up to about 100 millivolts due to the effects of liquid-to-liquid contact potential differences, imperfect calibration of liquid resistance of sample solutions, interference from spectral sensitizing dye anions, and effects of dye concentration. Allow excursions. This can ensure the reproducibility of the measured potential value by calibrating the standard sample with 3,3'-diethylthiacarbocyanine perchlorate.

  Specific examples (A-1 to A-31) of spectral sensitizing dyes preferably used in the present invention and the values of Ered and Eox are shown below, but the present invention is not limited to these. .

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

(Non-photosensitive aliphatic carboxylic acid silver salt particles (organic fatty acid silver salt))
In the present invention, the organic silver salt 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. Organic or inorganic complexes described in Research Disclosure (hereinafter also referred to as RD) 17029 and 29963 in which the ligand has a value of 4.0 to 10.0 as a total stability constant with respect to silver ions are also preferable. Examples of these suitable silver salts include the following.

  Silver salts of organic acids: silver salts such as gallic acid, succinic acid, behenic acid, stearic acid, arachidic acid, palmitic acid, lauric acid and the like. Silver carboxyalkylthiourea salts: Silver salts such as 1- (3-carboxypropyl) thiourea and 1- (3-carboxypropyl) -3,3-dimethylthiourea. Silver salt or complex of polymer reaction product of aldehyde and hydroxy-substituted aromatic carboxylic acid: Aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) and hydroxy-substituted acids (salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, etc.) A silver salt or complex of the reaction product of Silver salts or complexes of thiones: Silver salts or complexes such as 3- (2-carboxyethyl) -4-hydroxymethyl-4-thiazoline-2-thione and 3-carboxymethyl-4-thiazoline-2-thione. A complex or salt of nitrogen acid and silver 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, and silver salts of mercaptides.

  Among these, preferable silver salts include non-photosensitive aliphatic carboxylic acid silver salt particles according to the present invention, for example, long-chain (10 to 30 carbon atoms, preferably 15 to 25) silver carboxylic acid silver salts. The particles include, for example, silver behenate, silver arachidate, and silver stearate. In the present invention, it is preferable to mix two or more kinds of organic silver salts in order to improve developability and form a silver image having a high density and a high contrast. For example, a silver ion solution is added to a mixture of two or more kinds of organic acids. It is preferable to prepare by mixing.

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

  The organic silver salt according to the present invention can be used in various shapes, but tabular grains are preferred. In particular, it is a flat organic silver salt particle having an aspect ratio of 3 or more, and the shape anisotropy of two substantially parallel faces (main planes) having the largest area is reduced in the photosensitive layer. In order to perform filling, particles having an average needle-like ratio of the tabular organic silver salt particles measured from the main plane direction of 1.1 or more and less than 10.0 are preferable. A more preferable acicular ratio is 1.1 or more and less than 5.0.

  In the present invention, the term “tabular organic silver salt particles having an aspect ratio of 3 or more” means that the tabular organic silver salt particles occupy 50% by number or more of the total organic silver salt particles. Further, in the organic silver salt according to the present invention, tabular grains having an aspect ratio of 3 or more preferably occupy 60% or more of the total number of grains, more preferably 70% or more (number), and particularly preferably 80. % Or more (number).

  The aspect ratio (abbreviated as AR) is represented by the following formula.

AR = average particle diameter (μm) / average thickness (μm)
The aspect ratio of the tabular organic silver salt particles according to the present invention is preferably 3 to 20, and more preferably 3 to 10. The reason is that if the aspect ratio is too low, the organic silver salt particles tend to be close-packed, and if the aspect ratio is too high, the organic silver salt particles tend to overlap with each other, and the organic silver salt particles are dispersed in a stuck state. The above range is preferable because light scattering or the like is likely to occur and the transparency of the photothermographic material is lowered as a result.

  In order to obtain the above average particle diameter, the dispersed organic silver salt particles are diluted and dispersed on a grid with a carbon support film, and directly magnified using a transmission electron microscope (JEOL: 2000FX type). Take a picture at 5000x magnification. The photographed negative is captured as a digital image by a scanner, and 300 or more particle diameters (equivalent circle diameter) are measured using appropriate image processing software, and the average particle diameter is calculated.

  The average thickness is calculated by a method using a transmission electron microscope (TEM) as shown below.

  First, the photosensitive layer coated on the support is attached to an appropriate holder with an adhesive, and an ultrathin slice having a thickness of 0.1 to 0.2 μm is produced using a diamond knife in a direction perpendicular to the support surface. To do. This ultra-thin slice is supported on a copper mesh, transferred onto a carbon film that has been hydrophilized by glow discharge, and cooled to −130 ° C. or less with liquid nitrogen, using a TEM, at a magnification of 5,000 to 40,000 times The bright field image is observed and the image is quickly recorded on a film, an imaging plate, a CCD camera or the like. At this time, it is preferable to appropriately select a portion where the section is not torn or slack as the field of view to be observed.

  As the carbon film, one supported by an organic film such as ultrathin collodion or form bar is preferably used, and more preferably, the carbon film is formed on a rock salt substrate and dissolved and removed, or the organic film is formed of an organic film. It is a carbon-only film obtained by solvent and ion etching. The acceleration voltage of TEM is preferably 80 to 400 kV, particularly preferably 80 to 200 kV.

  In addition, for details of electron microscope observation techniques and sample preparation techniques, see “The Electron Microscopy Society of Kanto Branch / Medical and Biological Electron Microscopy” (Maruzen), “The Electron Microscopy Society of Kanto Branch / Electron Microscope Biological Samples” “Production method” (Maruzen) can be referred to respectively.

  A TEM image recorded on a suitable medium is preferably decomposed into at least 1024 × 1024 pixels, preferably 2048 × 2048 pixels, and subjected to image processing by a computer. In order to perform image processing, it is preferable that an analog image recorded on a film is converted into a digital image by a scanner or the like, and shading correction, contrast / edge enhancement, and the like are performed as necessary. Thereafter, a histogram is prepared, and a portion corresponding to the organic silver salt particles is extracted by binarization processing. The thickness of the extracted organic silver salt particles is manually measured for 300 or more with appropriate software, and the average value is obtained.

  Moreover, the average value of the acicular ratio of the flat organic silver salt particles can be obtained by the following method. First, the photosensitive layer containing tabular organic silver salt particles is swollen with an organic solvent capable of dissolving the photosensitive layer binder and peeled off from the support, and ultrasonic cleaning, centrifugation, and removal of the supernatant using the solvent are performed. Repeat 5 times. In addition, the said process is implemented under a safelight.

  Subsequently, it is diluted with methyl ethyl ketone (MEK) so that the solid content concentration of the organic silver salt is 0.01%, and ultrasonically dispersed, and then dropped on a polyethylene terephthalate film that has been made hydrophilic by glow discharge and dried.

  The film on which the particles are mounted is preferably used for observation after a Pt-C having a thickness of 3 nm is obliquely deposited by an electron beam from an angle of 30 ° with respect to the film surface in a vacuum deposition apparatus.

  The prepared sample was observed with a field emission scanning electron microscope (FE-SEM) at an acceleration voltage of 2 to 4 kV and a secondary electron image at a magnification of 5000 to 20000, and an image on an appropriate recording medium. Save.

  For the above-mentioned processing, it is convenient to use an apparatus capable of AD-converting an image signal from the electron microscope main body and recording it directly as digital information on a memory. However, an analog image recorded on a polaroid film or the like is also a scanner. It can be used by converting it into a digital image and performing shading correction, contrast / edge enhancement, etc. as necessary.

  As the procedure of the image processing described above, first, a histogram is prepared, and a portion corresponding to organic silver salt particles having an aspect ratio of 3 or more is extracted by binarization processing. The particles aggregated by necessity are cut by an appropriate algorithm or manual operation to extract the contour. Thereafter, the maximum length (MX LNG) and the minimum width (WIDTH) of each particle are measured for at least 1000 particles, and the acicular ratio is determined for each particle by the following formula. The maximum particle length refers to the maximum value when two points in a particle are connected by a straight line. Further, the minimum width of the particle means a value when the distance between the parallel lines becomes a minimum value when two parallel lines circumscribing the particle are drawn.

Needle-shaped ratio = (MX LNG) ÷ (WIDTH)
Then, the average value of the acicular ratio regarding all the measured particles is calculated. When performing the measurement according to the above procedure, it is preferable to sufficiently perform length correction (scale correction) per pixel and correction of two-dimensional distortion of the measurement system using a standard sample in advance. Uniform latex particles (DULP) commercially available from Dow Chemical Company, USA are suitable as the standard sample, and polystyrene particles having a coefficient of variation of less than 10% for a particle size of 0.1 to 0.3 μm. Specifically, a lot having a particle size of 0.212 μm and a standard deviation of 0.0029 μm is available.

  Details of the image processing technology can be referred to "Hiroshi Tanaka image processing applied technology (Industry Study Group)", and the image processing program or device is not particularly limited as long as the above operation is possible, An example is Lulex-III manufactured by Nireco.

  The method for obtaining the organic silver salt particles having the above-mentioned shape is not particularly limited. However, the mixed state at the time of forming the organic acid alkali metal salt soap and / or the mixed state at the time of adding silver nitrate to the soap is preferably maintained. It is also effective to optimize the ratio of silver nitrate that reacts with soap.

  The tabular organic silver salt particles are preferably preliminarily dispersed together with a binder, a surfactant and the like, if necessary, and then dispersed and pulverized with a media disperser or a high-pressure homogenizer. For the preliminary dispersion, a general stirrer such as an anchor type or a propeller type, a high-speed rotating centrifugal radiation type stirrer (dissolver), or a high-speed rotating shear type stirrer (homomixer) can be used.

  In addition, as the media dispersing machine, a rolling mill such as a ball mill, a planetary ball mill, a vibrating ball mill, a bead mill that is a medium stirring mill, an attritor, other basket mills, and the like can be used, and as a high-pressure homogenizer, Various types can be used, such as a type that collides with a wall, a plug, etc., a type in which liquids are collided at a high speed after being divided into a plurality of types, and a type in which fine orifices are passed.

Examples of the ceramic used for the ceramic beads used when dispersing the media include Al ₂ O ₃ , BaTiO ₃ , SrTiO ₃ , MgO, ZrO, BeO, Cr ₂ O ₃ , SiO ₂ , SiO ₂ —Al ₂ O ₃ , Cr ₂ O ₃ —MgO, MgO—CaO, MgO—C, MgO—Al ₂ O ₃ (spinel), SiC, TiO ₂ , K ₂ O, Na ₂ O, BaO, PbO, B ₂ O ₃ , SrTiO ₃ ( strontium _{titanate), BeAl 2 O 4, Y} 3 Al 5 O 12, ZrO 2 -Y 2 O 3 ( cubic _{zirconia), 3BeO-Al 2 O 3} -6SiO 2 ( synthesis emerald), C (diamond), Si ₂ O—nH ₂ O, ticker silicon, yttrium stabilized zirconia, zirconia reinforced alumina and the like are preferable. Yttrium-stabilized zirconia and zirconia reinforced alumina (hereinafter, these ceramics containing zirconia are hereinafter abbreviated as zirconia) are particularly preferably used because of the low generation of impurities due to friction with beads and dispersers during dispersion.

  In the apparatus used when dispersing the flat organic silver salt particles, it is preferable to use ceramics such as zirconia, alumina, silicon nitride, boron nitride or diamond as the material of the member in contact with the organic silver salt particles, Of these, zirconia is preferably used.

  When the dispersion is performed, the binder concentration is preferably 0.1 to 10% of the mass of the organic silver salt, and it is preferable that the liquid temperature does not exceed 45 ° C. from the preliminary dispersion through the main dispersion. Further, as preferable operating conditions for the present dispersion, for example, when a high-pressure homogenizer is used as the dispersing means, preferable conditions are 29.42 to 98.06 MPa, and the number of operations is preferably 2 times or more. Moreover, when using a media dispersion machine as a dispersion | distribution means, 6-13 m / sec of peripheral speed is mentioned as preferable conditions.

  Further, zirconia can be used for a part of beads and members and can be mixed in the dispersed emulsion at the time of dispersion. This is preferably effective in terms of photographic performance. Zirconia fragments may be added later to the dispersed emulsion or may be added in advance during preliminary dispersion. Although it does not specifically limit as a specific method, For example, if MEK is circulated through the bead mill filled with zirconia beads, a high-concentration zirconia solution can be obtained. What is necessary is just to add this by a preferable density | concentration at a preferable time.

  In the photosensitive emulsion containing photosensitive silver halide grains and organic silver salt grains, it is preferable to contain 0.01 to 0.5 mg of zirconium per 1 g of silver, and more preferable zirconium content is 0.01. ~ 0.3 mg. Moreover, as a preferable containing form, it is preferable that it is a microparticle with a particle size of 0.02 micrometer or less.

  The conditions for preparing the photosensitive emulsion having such characteristics are not particularly limited. However, the mixed state at the time of forming the organic acid alkali metal salt soap and / or the mixed state at the time of adding silver nitrate to the soap are favorable. Maintaining, optimizing the proportion of silver nitrate that reacts with soap, dispersing and grinding with a media disperser or high-pressure homogenizer, the binder concentration is 0.1 to 10% by mass of the amount of organic silver salt In addition to the addition, the temperature from drying to the end of this dispersion does not exceed 45 ° C., and the like, it is preferable to use a dissolver at the time of liquid preparation and stir at a peripheral speed of 2.0 m / second or more. .

The ratio of the projected area and the total projected area of the organic silver salt particles having a specific projected area value as described above, as described in the section for obtaining the average thickness of tabular grains having an aspect ratio of 3 or more, A portion corresponding to the organic silver salt particles is extracted by a method using TEM. At this time, the aggregated organic silver salt particles are treated as one particle, and the area of each particle is determined. Similarly, at least 1,000, preferably obtains the area about 2,000 particles, each, A: 0.025 .mu.m less than ^2, B: 0.025 .mu.m ² or 0.2μm below ^2, C: 0 Classify into 3 groups of ² μm ² or more. The photothermographic material of the present invention is 70% or more of the total area of particles measured for the total area of particles belonging to Group A, and the total area of particles for the group C is measured. What satisfies 10% or less of an area is preferable.

  When performing the measurement according to the above procedure, it is preferable to sufficiently perform the length correction (scale correction) per pixel and the two-dimensional distortion of the measurement system in advance using a standard sample.

  The organic silver salt particles are preferably monodisperse particles, and the preferred monodispersity is 1 to 30%. By using monodisperse particles in this range, an image having a high density can be obtained. The monodispersity here is defined by the following formula.

Monodispersity = (standard deviation of particle size) / (average value of particle size) × 100
The average particle diameter of the organic silver salt particles is preferably 0.01 to 0.2 μm, more preferably 0.02 to 0.15 μm, and the average particle diameter (equivalent circle diameter) is observed with an electron microscope. It represents the diameter of a circle having an area equal to the individual particle image.

In order to prevent devitrification of the photothermographic material, the total amount of silver halide and organic silver salt is preferably 0.5 to 2.2 g per 1 m ² in terms of silver amount. By setting this range, a high-contrast image can be obtained.

(binder)
The binder used in the photothermographic material of the present invention is transparent or translucent and generally colorless, and is a natural polymer synthetic resin, polymer and copolymer, and other media for forming a film such as gelatin, gum arabic, poly (vinyl). Alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, polyacrylic acid, polymethylmethacrylic acid, polyvinyl chloride, polymethacrylic acid, copoly (styrene-maleic anhydride), Copoly (styrene-acrylonitrile), copoly (styrene-butadiene), polyvinyl acetals (polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resins, polyvinylidene chloride, polyester Kishido, polycarbonates, polyvinyl acetate, cellulose esters, and polyamides. These may be hydrophilic or non-hydrophilic. Alternatively, SBR latex, NBR latex, or the like may be added.

  Preferred binders for the photosensitive layer of the photothermographic material are polyvinyl acetals, and a particularly preferred binder is polyvinyl butyral. In addition, in non-photosensitive layers such as an overcoat layer and an undercoat layer, particularly a protective layer and a back coat layer, cellulose esters which are polymers having a higher glass transition temperature (Tg), particularly triacetyl cellulose, cellulose acetate butyrate, etc. Polymers are preferred. In addition, the said binder can be used in combination of 2 or more type as needed.

  Examples of the binder preferably used in the present invention include the following polyvinyl acetals.

Such a binder is used in an effective range to function as a binder. The effective range can be easily determined by one skilled in the art. For example, as an index for holding at least organic silver salt particles in the photosensitive layer, the ratio of the binder to the organic silver salt particles is preferably 15: 1 to 1: 2, particularly 8: 1 to 1: 1. The range of is preferable. That is, it is preferable that the binder of the photosensitive layer is a 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.
(Water-soluble binder)
Water-soluble binders suitable for heat-developable photosensitive materials are transparent or translucent and generally colorless, natural polymer synthetic resins, polymers and copolymers, and other media forming films such as gelatin, gum arabic, poly (vinyl) Alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, polyacrylic acid, polymethylmethacrylic acid, polyvinyl chloride, polymethacrylic acid, copoly (styrene-maleic anhydride), Copoly (styrene-acrylonitrile), copoly (styrene-butadiene), polyvinyl acetals (polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resins, polyvinylidene chloride, poly Pokishido, polycarbonates, polyvinyl acetate, cellulose esters, polyamides, and the like.

  Usually, single or multiple photosensitive silver halide grains are provided in the form of a hydrophilic photosensitive silver halide emulsion containing one or more peptizers (eg, gelatin). The concentration of the photosensitive silver halide in the coating solution is usually 0.01 to 1 mole per mole of the non-photosensitive organic silver salt.

  Hydrophilic silver halide emulsions containing peptizers can be made using conventional methods in the photographic art, including those described in Product Licensing Index, Vol. 92, December 1971. The silver halide emulsion may be washed or unwashed as described and can be chemically sensitized as follows. The hydrophilic photosensitive silver halide emulsion contains one or more peptizers that are compatible with aqueous solvents.

  Useful peptizers include, but are not limited to, gelatin-based peptizers known in the photographic art such as phthalated and non-phthalated gelatin, acid hydrolyzed gelatin and poly (vinyl alcohol). A particularly preferred peptizer is a cationic starch, which is disclosed in US Pat. Nos. 5,604,085 (Maskasky), 5,620,840 (Maskasky), 5,667,955 (Maskasky) and , 733, 718 (Maskasky). Such peptizers reduce fog and improve raw film shelf life.

  The amount of peptizer in the hydrophilic silver halide emulsion is usually 5 to 40 g per mole of silver. A particularly effective concentration of peptizer is 9-15 g per mole of silver.

  It is also preferred that a hydrophilic binder be present in the silver halide blend or emulsion. Useful binders, including those conventionally used to make light sensitive silver halide emulsions, may be the same or different from the peptizer. Gelatins, polyacrylamides, polymethacrylates, poly (vinyl alcohol) and starches are preferred. Poly (vinyl alcohol) is more preferred as a binder for hydrophilic silver halide emulsions.

(Crosslinking agent)
As the crosslinking agent, various crosslinking agents conventionally used for ordinary photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based compounds described in JP-A No. 50-96216 are used. Sulfonic acid ester-based, acryloyl-based, carbodiimide-based, and silane compound-based crosslinking agents may be used, but an isocyanate compound, a silane compound, an epoxy compound, or an acid anhydride is preferable. These compounds are described in detail in JP-A No. 2001-249428.

  In the present invention, it is preferable to contain a matting agent on the photosensitive layer side, and it is preferable to dispose the matting agent on the surface of the photothermographic material in order to prevent scratches on the image after heat development. The matting agent is preferably contained in a mass ratio of 0.5 to 10% with respect to the total binder on the photosensitive layer side. The material of the matting agent used in the present invention may be either organic or inorganic. Examples of inorganic substances include silica described in Swiss Patent No. 330,158, glass powder described in French Patent No. 1,296,995, and alkaline earth described in British Patent No. 1,173,181. Metals or carbonates such as cadmium and zinc can be used as the matting agent. Examples of organic substances include starch described in U.S. Pat. No. 2,322,037 and the like, starch derivatives described in Belgian Patent 625,451 and British Patent 981,198, and Japanese Patent Publication No. 44-3643. Polyvinyl alcohol described, polystyrene or polymethacrylate described in Swiss Patent No. 330,158, polyacrylonitrile described in US Pat. No. 3,079,257, US Pat. No. 3,022,169 etc. An organic matting agent such as prepared polycarbonate can be used.

  The shape of the matting agent may be either a regular shape or an irregular shape, but is preferably a regular shape, and a spherical shape is particularly preferably used. The size of the matting agent is represented by a diameter when the volume of the matting agent is converted into a sphere, and the particle size of the matting agent in the present invention indicates the diameter converted into a sphere. The matting agent used in the present invention preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm. The coefficient of variation of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less. The variation coefficient of the particle size distribution referred to here is represented by the same formula as the variation coefficient of the silver salt particles. The matting agent can be included in any constituent layer, but preferably in the constituent layers other than the photosensitive layer. Addition to the outermost layer as viewed from the support is more preferable. The method of adding the matting agent may be a method in which the matting agent is dispersed and applied in advance, or a method of spraying the matting agent before the coating solution is applied and the drying is completed may be used. . In addition, when a plurality of types of matting agents are added, both the above methods may be used in combination.

  It is preferable to add a color toner to the photothermographic material of the invention. Examples of suitable toning agents are disclosed in RD17029, and specific examples include the following.

  Imides (phthalimide, etc.); Cyclic imides, pyrazolin-5-ones and quinazolinones (succinimide, 3-phenyl-2-pyrazolin-5-one, 1-phenylurazole, quinazoline, 2,4-thiazolidinedione, etc. ); Naphtalimides (such as N-hydroxy-1,8-naphthalimide); Cobalt complexes (such as hexamine trifluoroacetate of cobalt); Mercaptans (such as 3-mercapto-1,2,4-triazole); N- (amino Methyl) aryldicarboximides (such as N- (dimethylaminomethyl) phthalimide); combinations of blocked pyrazoles, isothiuronium derivatives and certain photobleaching agents (N, N′-hexamethylene (1-carbamoyl- 3,5-dimethylpyrazole), 1,8- (3,6 Dioxaoctane) bis (isothiuronium trifluoroacetate) and 2- (tribromomethylsulfonyl) benzothiazole); merocyanine dye (3-ethyl-5-((3-ethyl-2-benzothiazolinylidene) (Benzothiazolinylidene))-1-methylethylidene) -2-thio-2,4-oxazolidinedione, etc.); phthalazinone, phthalazinone derivatives or metal salts of these derivatives (4- (1-naphthyl) phthalazinone, 6 -Chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); a combination of phthalazinone and a sulfinic acid derivative (6-chlorophthalazinone + sodium benzenesulfinate or 8-methylphthalazinone + sodium p-trisulfonate); Razine + phthalic acid combination; phthalazine (including adducts of phthalazine) and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivative and anhydride (phthalic acid, 4-methylphthalic acid) A combination with at least one compound selected from acids, 4-nitrophthalic acid and tetrachlorophthalic anhydride); quinazolinediones, benzoxazines, naltoxazine derivatives; benzoxazine-2,4-diones (1,3- Benzoxazine-2,4-dione, etc.); pyrimidines and asymmetric-triazines (2,4-dihydroxypyrimidine etc.), and tetraazapentalene derivatives (3,6-dimercapto-1,4-diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene etc.), etc. Preferred toning agents are phthalazone or phthalazine.

(Layer structure)
The photothermographic material of the present invention has at least one photosensitive layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer. In order to control the amount of light passing through the photosensitive layer or the wavelength distribution, a filter layer may be formed on the same side or the opposite side of the photosensitive layer, or a dye or a known pigment may be directly contained in the photosensitive layer. May be. The photosensitive layer may be composed of a plurality of layers, or may have a different sensitivity for gradation adjustment, for example, a high sensitivity layer / low sensitivity layer or a low sensitivity layer / high sensitivity layer.

  Various additives may be added to any of the photosensitive layer, the non-photosensitive layer, and other forming layers. In the photothermographic material of the invention, for example, a surfactant, an antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber, a coating aid and the like may be used.

(Coating technology)
The photothermographic material of the present invention may be formed by preparing a coating solution in which the above-described constituent materials are dissolved or dispersed in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment. preferable. Here, "multiple simultaneous multi-layer coating" means that a coating solution for each constituent layer (for example, a photosensitive layer and a protective layer) is prepared, and when coating this onto a support, each layer is individually coated and dried repeatedly. In other words, it means that each constituent layer can be formed in such a state that the multilayer coating and drying can be performed simultaneously. That is, the upper layer is provided before the remaining amount of the total solvent in the lower layer reaches 70% by mass or less.

  There are no particular limitations on the method of applying multiple layers of each constituent layer simultaneously, and 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 there is no volatilization 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.

(Exposure conditions)
For exposure of the photothermographic material, it is desirable to use a light source suitable for the color sensitivity imparted to the photothermographic material. For example, when the photothermographic material is sensitive to infrared light, it can be applied to any light source as long as it is in the infrared light range. In view of the fact that the semiconductor laser can be made transparent, an infrared semiconductor laser (780 to 820 nm) is more preferably used.

  The exposure is preferably performed by laser scanning exposure, but various methods can be adopted as the exposure method. For example, as a first preferred method, there is a method using a laser scanning exposure machine in which the angle formed by the scanning laser beam and the exposure surface of the photothermographic material is not substantially perpendicular. Here, “not substantially vertical” means that the angle that is closest to the vertical during laser scanning is preferably 55 to 88 degrees, more preferably 60 to 86 degrees, and still more preferably 65 to 84 degrees. Most preferably, it is 70 to 82 degrees.

  The beam spot diameter on the exposed surface 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 the smaller the spot diameter, the smaller 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 longitudinal single mode scanning laser beam, image quality degradation such as occurrence of interference fringe-like unevenness is reduced. In order to make it vertically multi-ply, a method such as using return light by combining or applying high-frequency superposition is preferable.

  Note that the vertical multi means that the exposure wavelength is not single, and the exposure wavelength distribution 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.

  Furthermore, as a third aspect, it is also preferable to form an image by scanning exposure using two or more lasers.

  As such an image recording method using a plurality of lasers, it is used in an image writing means of a laser printer or a digital copying machine that writes an image for each line in one scan in response to a request for high resolution and high speed. This technique is known, for example, from Japanese Patent Laid-Open No. 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, and is the same laser scanning optical apparatus in principle as a laser imager or the like. .

  The image formation of laser light on the photoconductor in the image writing means of a laser printer or digital copying machine is for one line from the image formation position of one laser light for the purpose of writing an image by a plurality of lines in one scan. The next laser beam is imaged by shifting. Specifically, the two light beams are close to each other in the sub-scanning direction on the image plane with an interval of several tens of μm, and the printing density is 400 dpi (dpi is 1 inch, that is, the number of dots per 2.54 cm). The pitch in the sub-scanning direction of the two beams is 63.5 μm, and 42.3 μm at 600 dpi.

  Unlike the method of shifting the resolution in the sub-scanning direction as described above, in the present invention, it is also preferable to form an image by condensing two or more lasers at the same location on the exposure surface while changing the incident angle. In this case, when the exposure energy on the exposure surface when writing is performed with one ordinary laser (wavelength λ nm), the N lasers used for exposure have the same wavelength (wavelength λ nm) and the same exposure energy. In the case of (En), 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 λnm.

In the image recording methods of the first, second, and third modes described above, solid lasers such as ruby laser, YAG laser, and glass laser, which are generally well known, are used as scanning lasers; He— Ne laser, 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 Semiconductor lasers such as ₂ lasers and GaSb lasers; chemical lasers, dye lasers, etc. can be selected and used in a timely manner, but among these, semiconductor lasers with a wavelength of 600 to 1200 nm due to maintenance and light source size problems Is preferably used. In a laser used in a laser imager or a laser image setter, the beam spot diameter on the exposed surface of the material when scanned by a photothermographic material is generally 5 to 75 μm as a short axis diameter, and a long axis diameter. The laser beam scanning speed can be set to an optimum value for each photothermographic material depending on the sensitivity and laser power at the laser oscillation wavelength inherent to the photothermographic material.

(Development conditions)
The development conditions for the photothermographic material vary depending on the equipment, apparatus, or means used, but typically involve heating the imagewise exposed material at a suitable high temperature. The latent image obtained after exposure is subjected to a rapid development process at a moderately high temperature (about 80 to 150 ° C., preferably about 100 to 130 ° C.) for a sufficient time (in the present invention, a speed of 5 to 20 seconds). Development is performed by heating the photothermographic material.

  If the heating temperature is less than 80 ° C, a sufficient image density cannot be obtained in a short time, and if the heating temperature exceeds 150 ° C, the binder melts and transfer to a roller or the like as well as transportability and development. It also adversely affects the 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 any supply of processing liquid such as water from the outside.

  The heating device, apparatus, and means may be a heating means typical as a heat generator using a hot plate, iron, hot roller, carbon, white titanium, or the like. More preferably, the photothermographic material provided with the protective layer is subjected to heat treatment by bringing the surface having the protective layer into contact with the heating means, in order to achieve uniform heating, thermal efficiency and workability. It is preferable from the point of view, and it is preferable that the surface is conveyed while being brought into contact with a heat roller, heated and developed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “%” in the examples represents “mass%”.

Example 1
A photothermographic material was prepared according to the following method.

<< Preparation of photosensitive silver halide emulsion Em-A >>
(A1)
Phenylcarbamoylated gelatin 88.3g
Compound (A) (10% methanol aqueous solution) 10 ml
Potassium bromide 0.32g
Finish to 5429 ml with water (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(C1)
Potassium bromide 51.55g
Potassium iodide 1.47g
Finish to 660ml with water (D1)
Potassium bromide 151.6g
Potassium iodide 7.67g
0.93ml potassium hexachloroiridium (IV) (1% aqueous solution)
Potassium hexacyanoferrate (II) 0.004g
Finish to 1982ml with water (E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount (F1)
Potassium hydroxide 0.71g
Finish to 20ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
(H1)
Anhydrous sodium carbonate 1.72 g
Finish to 151 ml with water Compound (A):
_{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 shown in Japanese Patent Publication No. 58-58288, while controlling the 1/4 amount of the solution (B1) and the total amount of the solution (C1) to 75 ° C. and pAg 8.09, simultaneously in the solution (A1) Nucleation was performed by adding 4 minutes and 45 seconds by a mixing method. After 7 minutes, 3/4 amount of the solution (B1) and the whole amount of the solution (D1) were added by a simultaneous mixing method over 14 minutes and 15 seconds. After stirring for 5 minutes, the temperature was lowered to 40 ° C., the whole amount of the solution (G1) was added, and the silver halide emulsion was allowed to settle. 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 prepare a photosensitive silver halide emulsion Em-A.

This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 110.6 nm (equivalent circle diameter), a grain size variation coefficient of 16%, and a [100] face ratio of 89%. (AgI content on the particle surface is 3.5 mol%)
<< Preparation of photosensitive silver halide emulsion Em-B >>
Nucleation was carried out by changing the temperature to 30 ° C., and after 10 minutes, 3/4 amount of the solution (B1) and the whole amount of the solution (D1) were added by the simultaneous mixing method over 14 minutes and 15 seconds. Photosensitive silver halide emulsion Em-B was prepared in the same manner as photosensitive silver halide emulsion Em-A. This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 45.5 nm (equivalent circle diameter), a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<< Preparation of photosensitive silver halide emulsions Em-C to Em-I >>
Nucleation was performed by changing the temperature to 30 ° C., and after 3 minutes, a 0.5% solid dispersion aqueous solution of a sulfur releasing agent was added as shown in Table 1. After 4 minutes, hydrogen peroxide solution (3% solution) 2.4 × 10 ⁻² mol / Ag mol was added. After 10 minutes, 3/4 amount of the solution (B1) and the total amount of the solution (D1) were added by the simultaneous mixing method over 14 minutes and 15 seconds, in the same manner as the photosensitive silver halide emulsion Em-A. Photosensitive silver halide emulsions Em-C to Em-I were prepared.

<< Preparation of powdered organic silver salt A >>
In 5470 ml of pure water, 52.3 g of behenic acid, 27.1 g of arachidic acid, 17.45 g of stearic acid and 0.9 g of palmitic acid were dissolved at 80 ° C. Next, 270.1 ml of a 1.5 mol / L sodium hydroxide aqueous solution was added while stirring at high speed, 6.9 ml of concentrated nitric acid was added, and then cooled to 55 ° C. to obtain an organic acid sodium solution. While maintaining the temperature of the organic acid sodium solution at 55 ° C., 380.3 ml of 1 mol / L silver nitrate solution was added over 2 minutes. Next, with stirring at high speed, the above-described photosensitive silver halide emulsion Em-A equivalent to 0.038 mol as silver and 450 ml of pure water were added over 5 minutes. After further stirring for 10 minutes at high speed, water-soluble salts were removed by filtration. Thereafter, water washing and filtration with deionized water were repeated until the electrical conductivity of the filtrate reached 2 μS / cm, and centrifugal dehydration was performed, followed by heating and drying until there was no decrease in mass to prepare powdered organic silver salt A.

<< Preparation of powdered organic silver salts B to I >>
Powdered organic silver salt B was prepared in the same manner as powdered organic silver salt A, except that photosensitive silver halide emulsions Em-B to Em-I were used as shown in Table 1 instead of photosensitive silver halide emulsion Em-A. ~ I was prepared.

<< Preparation of photosensitive emulsion dispersions A to I >>
While dissolving 14.57 g of polyvinyl butyral powder (Monsanto: Butvar B-79) in 1457 g of methyl ethyl ketone (MEK) and stirring with a dissolver type homogenizer, 500 g of the above powdered organic silver salts A to I were gradually added. Added and mixed well. Thereafter, dispersion was carried out at a peripheral speed of 13 m and a residence time in the mill of 0.5 minutes using a media type dispersing machine (gettzmann) filled with 80% of 1 mm diameter zirconium beads (manufactured by Toray Industries, Inc.). Dispersions A to I were prepared.

<< Preparation of stabilizer liquid >>
1.0 g of dye stabilizer-1 and 0.31 g of potassium acetate were dissolved in 14.35 g of methanol to obtain a stabilizer solution.

<< Preparation of sensitizing dye liquid >>
Spectral sensitizing dyes represented by the general formulas [Ia] to [Id] shown in Table 1 or comparative spectral sensitizing dye A, 2.49 g of 2-chlorobenzoic acid, and 21.48 g of dye. Stabilizer-2 was dissolved in 135 g of MEK to obtain a sensitizing dye solution.

<Preparation of reducing agent solution>
143.6 g of reducing agent A, 0.81 g of reducing agent B, 7.39 g of 4-methylphthalic acid, and 0.46 g of infrared dye were dissolved in 554 g of MEK to obtain a reducing agent solution.

[Preparation of photosensitive layer coating solutions A, B ', B, C to I]
As shown in Table 1, 50 g of the photosensitive emulsion dispersions A to I and 15.11 g of MEK were kept at 15 ° C. while stirring, 0.47 g of a stabilizer solution was added, and the mixture was stirred for 10 minutes. The sensitizing dye solution was added as described in 1 and stirred for 1 hour and 25 minutes, and 0.4 g of 0.9% MEK solution of Dye Stabilizer-3 was added. After 5 minutes, 12.45 g of polyvinyl acetal resin (compound P-1, Tg = 75 ° C.) was added as a binder resin and stirred for 30 minutes, and then 1.1 g of tetrachlorophthalic acid (13% MEK solution) was added. And stirred for 15 minutes. While continuing to stir, Desmodur N3300 (Movey: aliphatic isocyanate) 22% MEK solution 2.23 g, reducing agent liquid 21.2 g, phthalazine 12.74% MEK solution 3.34 g, fogging inhibitor ( A photosensitive layer coating solution A, B ′, B, C to I was obtained by stirring 4.0 g of 7% MEK solution) and 3.5 g of potassium toluenethiosulfonate (1% MEK solution).

[Surface protective layer coating solution]
While stirring 865 g of MEK, 96 g of cellulose acetate butyrate (manufactured by Eastman Chemical, CAB171-15), 4.5 g of polymethylmethacrylic acid (Rohm & Haas, paraloid A-21), 1. 5 g of an F-based activator (Asahi Glass Co., Surflon KH40) was added and dissolved. Next, 30 g of the following matting agent dispersion was added and stirred, and Compound O was added to a concentration of 0.045 g / m ² to prepare a surface protective layer coating solution.

(Preparation of matting agent dispersion)
Dissolve 7.5 g of cellulose acetate butyrate (Eastman Chemical: CAB171-15) in 42.5 g of MEK, add 5 g of calcium carbonate (Speciality Minerals: Super-Pflex200) to the dissolver type homogenizer. Was dispersed at 8000 rpm for 30 minutes to obtain a matting agent dispersion.

[Preparation of back surface coating solution]
While stirring MEK830 g, 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. Infrared dye 1 is added to the dissolved solution so that the absorbance (abs) of the absorption maximum of the infrared dye in the coating sample on the back surface is 0.3, and further the fluorine-based activator dissolved in 43.2 g of methanol 4.5 g (Surflon KH40, manufactured by Asahi Glass Co., Ltd.) and 2.3 g of a fluorine-based activator (Dainippon Ink Co., MegaFag F120K) were added and sufficiently stirred until dissolved. Finally, 75 g of silica (manufactured by WR Grace, Syloid 64X6000) dispersed in MEK with a dissolver type homogenizer at a concentration of 1% by mass was added and stirred to prepare a coating solution for the back surface.

<Production of support>
Corona discharge treatment of 0.15 kV · A · min / m ² was performed on both sides of a blue-colored polyethylene terephthalate film base (thickness: 175 μm) with a concentration of 0.170. On one surface thereof, an undercoat layer a was coated using the following undercoat coating solution A so that the dry film thickness was 0.2 μm. Further, the undercoat layer B was coated on the other surface using the following undercoat coating solution B so that the dry film thickness was 0.1 μm. 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.

(Undercoating liquid A)
270 g of copolymer latex liquid (30% solid content) of butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (30/20/25/25% ratio), surfactant (UL-1) 0. 6 g and 0.5 g of methylcellulose were mixed. Furthermore, 1.3 g of silica particles (Fuji Silysia Co., Ltd .: Psyroid 350) was added to 100 g of water, and the dispersion was subjected to a dispersion treatment for 30 minutes with an ultrasonic dispersing machine (ALEX Corporation: Ultrasonic Generator, frequency 25 kHz, 600 W). Finally, it was made up to 1000 ml with water to obtain a subbing coating solution A.

(Undercoating liquid B)
37.5 g of the following colloidal tin oxide dispersion, copolymer latex liquid of butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (20/30/25/25% ratio) (solid content 30%) 3 0.7 g, 14.8 g of copolymer latex liquid (solid content 30%) of butyl acrylate / styrene / glycidyl methacrylate (40/20/40% ratio) and 0.1 g of surfactant (UL-1) are mixed, The undercoating solution B was made up to 1000 ml with water.

<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 was dropped into distilled water from which the precipitate was washed, and after confirming that there was no reaction of chlorine ions, distilled water was 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.

[Preparation of photothermographic material]
On the undercoat layer a and the undercoat layer b of the subbing support, the following photosensitive layer surface application (as described in Table 1) and back layer surface application are performed, dried and heated. Development photosensitive material samples 1 to 10 were prepared.

(Coating on the photosensitive layer side)
Using the prepared photosensitive layer coating liquids A, B ′, B, C to I and the respective surface protective layer coating liquids, the photosensitive layer and the surface protective layer are respectively coated from the support side using an extrusion coater. And dried. The coated silver amount was 1.45 g / m ² , and the drying was performed for 5 minutes using a drying air having a temperature of 80 ° C. and a dew point temperature of 10 ° C. The surface protective layer was dried to a thickness of 1.5 μm.

(Application on the back side)
The prepared back surface coating solution was applied and dried using an extrusion coater so that the dry film thickness was 3 μm. The drying temperature was 100 ° C., and drying was performed for 5 minutes using a drying air having a dew point temperature of 10 ° C.

  The details of the constitution of the photothermographic material samples 1 to 10 produced as described above are shown in Table 1.

<< Evaluation of photothermographic material >>
Characteristics of the photothermographic materials (samples 1 to 10) prepared above were evaluated by the following methods.

(Measurement of Dmin, Dmax and sensitivity)
After processing each sample into a half-cut size, each sample was subjected to imagewise exposure with a 780 nm semiconductor laser. In the exposure, the angle between the exposure surface of the sample and the exposure laser beam was 80 degrees, the laser output was 57.45 mm / sec, 75 mW, and high frequency superposition was output in the vertical multimode. The heat development process was performed uniformly using a heat drum at a processing condition of 125 ° C. and 13.5 seconds. The density of the heat-developed sample thus obtained was measured with an optical densitometer (manufactured by Konica: PD-82), and a characteristic curve consisting of density D and exposure amount Log (1 / E) was created. The minimum density (Dmin = fog density), sensitivity, and maximum density (Dmax) were measured. The sensitivity was defined as the logarithm of the reciprocal of the exposure amount giving a density 1.0 higher than the minimum density. The results are shown as relative values with Sample 1 as 100.

(Evaluation of raw preservation)
Each of the prepared samples was stored in a light-shielding container at 40 ° C. and 55% RH for 30 days, and this was subjected to forced deterioration treatment. For comparison, the same sample was stored in a light-shielding container at 25 ° C. and 55% RH for 7 days, and this was used as a standard treatment. Each of these samples is exposed and thermally developed in the same manner as described above, the minimum density (fogging density) is measured in the same way, and the increase in fog (ΔDmin1) is calculated from the following formula. As a measure of storage stability, it was expressed as a relative value with that of Sample 1 as 100.

ΔDmin1 = (fogging concentration of forced deterioration treated sample) − (fogging concentration of reference treated sample)
(Evaluation of image light stability)
Each sample (image sample) that has been heat-developed by the above-described method is further subjected to a minimum density portion (Dmin portion) before and after being left under a fluorescent lamp for 7 days in a room at 37 ° C. and 55% RH. The minimum density (Dmin) variation (ΔDmin2) was determined according to the following formula, and this was used as a measure of image light resistance stability and displayed as a relative value with that of sample 1 as 100.

ΔDmin2 = (Dmin after fluorescent lamp exposure) − (Dmin before fluorescent lamp exposure)
In addition, the temperature on the used light source stand was 45 degreeC and 6000 Lux.

(Silver tone evaluation)
About the produced silver image, visual evaluation was performed and the silver color tone was determined according to the following reference | standard.

◎: Silver tone optimal for visual diagnosis ○: Silver tone with no hindrance during visual diagnosis ×: Silver tone that is easy to get tired during visual diagnosis and difficult to diagnose Result Is shown in Table 2.

  From Table 2, the sample of the present invention has high sensitivity, low fog, the highest density is sufficiently high, the silver tone is good, the raw storage property is excellent, and the image light stability after heat development is excellent. I understand that. In particular, it can be seen that high sensitivity and low fog can be maintained even when stored raw for a long period of time, and the image light stability after heat development is excellent. It can also be seen that it has suitability as a medical photosensitive material.

Example 2
[Preparation of PET support]
Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured at 25 ° C. in phenol / tetrachloroethane = 6/4 (mass ratio)) was obtained according to a conventional method. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to produce an unstretched film having a thickness of 175 μm after heat setting.

This was longitudinally stretched 3.3 times using rolls with different peripheral speeds, and then stretched 4.5 times with a tenter. The temperatures at this time were 110 ° C. and 130 ° C., respectively. Thereafter, the film was heat-fixed at 240 ° C. for 20 seconds and relaxed by 4% in the lateral direction at the same temperature. Thereafter, the chuck portion of the tenter was slit and then knurled at both ends, and wound at 4 kg / cm ² (4 × 10 ⁴ Pa) to obtain a roll having a thickness of 175 μm.

[Surface corona treatment]
Using a solid state corona treatment machine 6KVA model manufactured by Pillar, both surfaces of the support were treated at room temperature at 20 m / min. From the current and voltage readings at this time, it was found that the support was processed at 0.375 kV · A · min / m ² . The treatment frequency at this time was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

[Preparation of undercoat support]
<< Preparation of undercoat layer coating liquid >>
<Coating liquid for photosensitive layer (image forming layer) side undercoat>
59 g of pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 10% by mass solution
5.4g
MP-1000 (polymer fine particles, average particle size 0.4 μm), manufactured by Soken Chemical Co., Ltd.
0.91g
935 ml of distilled water
<Back surface side first layer coating solution>
Styrene-butadiene copolymer latex (solid content 40% by mass, styrene / butadiene mass ratio = 68/32)
158g
8 mass% aqueous solution of 2,4-dichloro-6-hydroxy-S-triazine sodium salt
20g
10% 1% by weight aqueous solution of sodium laurylbenzenesulfonate
854 ml of distilled water
<Back surface side second layer coating solution>
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion)
84g
Gelatin (10 mass% aqueous solution) 89.2g
8.6 g, manufactured by Shin-Etsu Chemical Co., Ltd., Metroz TC-5 (2% by weight aqueous solution)
Made by Soken Chemical Co., Ltd., MP-1000 0.01 g
10% 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 6 ml
Proxel (ICI) 1ml
805 ml of distilled water
<Preparation of undercoat support>
Each of both surfaces of the 175 μm thick biaxially stretched polyethylene terephthalate support is subjected to the corona discharge treatment, and then the photosensitive layer (image forming layer) side undercoat layer coating solution is applied to one side (photosensitive layer surface). Apply with a wire bar so that the wet coating amount is 6.6 ml / m ² (per one side), dry at 180 ° C. for 5 minutes, and then apply the back surface side first layer coating solution on the back surface (back surface). Is applied with a wire bar so that the wet coating amount is 5.7 ml / m ² , dried at 180 ° C. for 5 minutes, and further on the back surface (back surface), the back surface side second layer coating liquid undercoat coating liquid. Was coated with a wire bar so that the wet coating amount was 7.7 ml / m ² and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

[Preparation of back surface coating solution]
<Preparation of Base Precursor Solid Fine Particle Dispersion (a)>
64 g of the base precursor compound 11, 28 g of diphenylsulfone and 10 g of surfactant demole N10 manufactured by Kao Corporation were mixed with 220 ml of distilled water, and the mixture was used with a sand mill (1/4 Gallon Sand Grinder Mill, manufactured by IMEX Co., Ltd.). The beads were dispersed to obtain a solid fine particle dispersion (a) of a base precursor compound having an average particle size of 0.2 μm.

<Preparation of dye solid fine particle dispersion>
9.6 g of cyanine dye compound 13 and 5.8 g of sodium p-dodecylbenzenesulfonate are mixed with 305 ml of distilled water, and the mixture is dispersed in a bead using a sand mill (1/4 Gallon sand grinder mill, manufactured by IMEX Co., Ltd.). Thus, a dye solid fine particle dispersion having an average particle size of 0.2 μm was obtained.

<Preparation of antihalation layer coating solution>
Gelatin 17 g, polyacrylamide 9.6 g, solid fine particle dispersion (a) 70 g of the above-mentioned precursor precursor, 56 g of the above dye solid fine particle dispersion, monodisperse polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4) 1.5 g, benzoisothiazolinone 0.03 g, sodium polyethylene sulfonate 2.2 g, blue dye compound 14 0.2 g, yellow dye compound 15 3.9 g, and water 844 ml are mixed to form an antihalation layer coating solution. Prepared.

<Preparation of back surface protective layer coating solution>
The container was kept at 40 ° C., 50 g of gelatin, 0.2 g of sodium polystyrenesulfonate, 2.4 g of N, N-ethylenebis (vinylsulfonateacetamide), 1 g of sodium t-octylphenoxyethoxyethanesulfonate, 30 mg of benzoisothiazolinone , Fluorine-based surfactant (F-1: N-perfluorooctylsulfonyl-N-propylalanine potassium salt) 37 mg, fluorine-based surfactant (F-2: polyethylene glycol mono (N-perfluorooctylsulfonyl-N-) Propyl-2-aminoethyl) ether [ethylene oxide average polymerization degree 15]) 0.15 g, fluorosurfactant (F-3) 64 mg, fluorosurfactant (F-4) 32 mg, acrylic acid / ethyl acrylate Copolymer (copolymerization mass ratio 5/95 8.8 g, Aerosol OT (manufactured by American Cyanamid Co.) 0.6 g, and the back surface protective layer coating liquid was 950ml mixing 1.8g, water and liquid paraffin emulsion as liquid paraffin.

[Preparation of each component contained in image forming layer coating solution]
<Preparation of silver halide emulsion Em2-1, 2-2 ', 2-2 to 2-9>
To a solution of 1420 ml of distilled water, 4.3 ml of a 1% by weight potassium iodide solution, 3.5 ml of 0.5 mol / L sulfuric acid and 36.7 g of phthalated gelatin were added and stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 42 ° C., a solution A in which distilled water was added to 22.22 g of silver nitrate and diluted to 195.6 ml and solution B in which 21.8 g of potassium iodide was diluted with distilled water to a volume of 218 ml were added at a constant flow rate. The whole amount was added over 9 minutes. Thereafter, chemical sensitizers were added as shown in Table 3. Three minutes later, 10 ml of a 3.5% by mass aqueous hydrogen peroxide solution was added. After another 10 minutes, solution C, in which distilled water was added to 51.86 g of silver nitrate and diluted to 317.5 ml, and solution D in which 60 g of potassium iodide were diluted with distilled water to a volume of 600 ml, solution C was maintained at a constant flow rate for 120 minutes. The solution D was added by the controlled double jet method while maintaining the pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of the solution C and the solution D so as to be 1 × 10 ⁻⁴ mol per mol of silver. Further, 5 seconds after the completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

While maintaining the silver halide dispersion at 38 ° C. with stirring, 5 ml of a methanol solution of 0.34% by mass of 1,2-benzisothiazolin-3-one was added, and after 40 minutes, as shown in Table 3. A solid dispersion solution of spectral sensitizing dye was added, and the temperature was raised to 47 ° C. after 1 minute. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per 1 mol of silver, and further 5 minutes later, tellurium sensitizer C was added in a methanol solution at a rate of 2. per mol of silver. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes. 1.3 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ -diethylmelamine was added, and after 4 minutes, 5-methyl-2-mercaptobenzimidazole was added in methanol solution at a rate of 4. Halogenation by adding 5.4 × 10 ⁻³ mol of 8 × 10 ⁻³ mol and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole to 1 mol of silver with methanol solution Silver emulsions Em2-1, 2-2 'and 2-2 to 2-9 were prepared.

  Grains in the prepared silver halide emulsion were pure silver iodide grains having a sphere equivalent diameter variation coefficient of about 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<Preparation of mixed emulsions A, B ', B to I for coating solution for image forming layer>
The silver halide emulsions Em2-1, 2-2 'and 2-2 to 2-9 are dissolved so that the silver halide content is 38.2 g as the silver per 1 kg of the mixed emulsion for the image forming layer coating solution. By adding water, mixed emulsions A, B 'and B to I for the image forming layer coating solution were prepared.

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

  After completion of the addition of the sodium behenate solution, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm. Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying.

  When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average value was thickness a = 0.14 μm, minor axis b = 0.4 μm, major axis c = 0.6 μm, average aspect ratio 5.2. It was a flake-like crystal having an average sphere equivalent diameter of 0.52 μm and a sphere equivalent diameter variation coefficient of 15%.

  19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to the wet cake corresponding to a dry solid content of 260 kg to make a total amount of 1000 kg, and then slurryed with a dissolver blade, and a pipeline mixer (manufactured by Mizuho Kogyo Co., Ltd.). : PM-10 type).

Next, the pre-dispersed stock solution was adjusted to 1260 kg / cm ² by adjusting the pressure of a disperser (trade name: Microfluidizer M-610, manufactured by Microfluidics International Corporation, using a Z-type interaction chamber). The organic silver salt dispersion I (silver behenate dispersion) was prepared by repeated processing. The cooling operation was carried out by installing a serpentine heat exchanger before and after the interaction chamber, and adjusting the temperature of the refrigerant to a dispersion temperature of 18 ° C.

<Preparation of reducing agent complex-3 dispersion>
Reducing agent complex-3 (1,2 complex of 2,2′-methylenebis- (4-ethyl-6-tert-butylphenol) and triphenylphosphine oxide) 10 kg, triphenylphosphine oxide 0.12 kg and modified polyvinyl alcohol (Kuraray) 7.2 kg of water was added to 16 kg of a 10% by mass aqueous solution of Poval MP203 manufactured by Co., Ltd. and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 4 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to prepare a reducing agent concentration of 25% by mass to obtain a reducing agent complex-3 dispersion. The reducing agent complex particles contained in the reducing agent complex dispersion thus obtained had a median diameter of 0.46 μm and a maximum particle diameter of 1.6 μm or less. The obtained reducing agent complex dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

<Preparation of organic polyhalogen compound-2 dispersion>
10 kg of organic polyhalogen compound-2 (tribromomethanesulfonylbenzene), 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), 0.4 kg of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, Then, 14 kg of water was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to prepare an organic polyhalogen compound concentration of 26% by mass to obtain an organic polyhalogen compound-2 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<Preparation of organic polyhalogen compound-3 dispersion>
10 kg of an organic polyhalogen compound-3 (N-butyl-3-tribromomethanesulfonylbenzoamide), 20 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and 20 of sodium triisopropylnaphthalenesulfonate 0.4 kg of a mass% aqueous solution and 8 kg of water were added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to prepare an organic polyhalogen compound concentration of 25% by mass. This dispersion was heated at 40 ° C. for 5 hours to obtain an organic polyhalogen compound-3 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.36 μm and a maximum particle diameter of 1.5 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

<Preparation of Phthalazine Compound-1 Solution>
8 kg of Kuraray Co., Ltd. modified polyvinyl alcohol MP203 was dissolved in 174.57 kg of water, and then 3.15 kg of a 20 mass% aqueous solution of sodium triisopropylnaphthalenesulfonate and 70 mass of phthalazine compound-1 (6-isopropylphthalazine). 14.28 kg of% aqueous solution was added to prepare a phthalazine compound-1 solution, which is a 5% by mass solution of phthalazine compound-1.

<Preparation of Mercapto Compound-1 Aqueous Solution>
7 g of mercapto compound-1 (1- (3-sulfophenyl) -5-mercaptotetrazole sodium salt) was dissolved in 993 g of water to obtain a 0.7% by mass aqueous solution.

<Preparation of pigment-1 dispersion>
64 g of Pigment-1 (CI Pigment Blue) 60 and 6.4 g of DEMOL N manufactured by Kao Corporation were added to 250 g of water and mixed well to obtain a slurry. Prepare 800 g of zirconia beads having an average diameter of 0.5 mm, put them in a vessel together with the slurry, and disperse with a disperser (1/4 G sand grinder mill: manufactured by IMEX Co., Ltd.) for 25 hours. Obtained. The pigment particles contained in the pigment dispersion thus obtained had an average particle size of 0.21 μm.

<Preparation of SBR latex solution>
The SBR latex (St (70.5%) / Bu (26.5%) / AA (3%), Tg 23 ° C.) was prepared as follows. First, ammonium persulfate is used as a polymerization initiator, an anionic surfactant is used as an emulsifier, 70.5 parts by mass of styrene, 26.5 parts by mass of butadiene, and 3 parts by mass of acrylic acid are subjected to emulsion polymerization, and then 8 ° C. at 80 ° C. Time aging was performed. Thereafter, the mixture was cooled to 40 ° C., adjusted to pH 7.0 with aqueous ammonia, and Sandet BL manufactured by Sanyo Chemical Co., Ltd. was further added to 0.22%. Next, 5% aqueous sodium hydroxide solution was added to adjust the pH to 8.3, and further adjusted to pH 8.4 with aqueous ammonia. The molar ratio of Na ⁺ ions and NH ₄ ⁺ ions used at this time was 1: 2.3. Further, 0.15 ml of a 7% aqueous solution of benzoisothiazoline non sodium salt was added to 1 kg of this liquid to prepare an SBR latex liquid.

  The average particle size of the obtained SBR latex was 0.1 μm, the solid content concentration was 43% by mass, the equilibrium water content at 25 ° C. and 60% RH was 0.6% by mass, and the ionic conductivity was 4.2 mS / cm (ion conductivity The measurement was performed using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd., a latex stock solution (43% by mass) measured at 25 ° C.), and the pH was 8.4.

<Preparation of Image Forming Layer Coating Liquids A, B ', B to I>
1000 g of organic silver salt dispersion I obtained above, 104 ml of water, 30 g of pigment-1 dispersion, 6.3 g of organic polyhalogen compound-2 dispersion, 20.7 g of organic polyhalogen compound-3 dispersion, phthalazine compound-1 solution 173 g, SBR latex (Tg: 23 ° C.) 1082 g, reducing agent complex-3 dispersion 258 g, and mercapto compound-1 solution 9 g were sequentially added, and mixed emulsions A, B ′ and B for the image forming layer coating solution immediately before coating. ˜I were added as shown in Table 3, and mixed well to prepare image forming layer coating solutions A, B ′, B to I (in addition, image forming layer coating solutions A, B ′, B to I). Was directly fed to the coating die and applied).

<Preparation of intermediate layer coating solution>
772 g of 10 mass% aqueous solution of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), 5.3 g of pigment-1 dispersion (20 mass% dispersion of pigment-1), methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / Acrylic acid copolymer (copolymerization mass ratio 64/9/20/5/2) 27.5 mass% aqueous solution of aerosol OT (manufactured by American Cyanamid Co., Ltd.) 226 g of latex 27.5 mass% liquid, phthalate 10.5 ml of a 20% by weight aqueous solution of acid diammonium salt, water is added so that the total amount becomes 880 g, and the pH is adjusted to 7.5 with NaOH to obtain an intermediate layer coating solution of 10 ml / m ² . The solution was fed to the coating die. The viscosity of the coating solution was 65 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

[Preparation of surface protective layer coating solution]
<Preparation of surface protective layer first layer coating solution>
Inert gelatin (64 g) is dissolved in water, and methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5/2) 27.5% by weight latex 80 g, 23 ml of a 10% by weight methanol solution of phthalic acid, 23 ml of a 10% by weight aqueous solution of 4-methylphthalic acid, 28 ml of sulfuric acid having a concentration of 0.5 mol / L, and a 5% by weight aqueous solution of Aerosol OT (American Cyanamid Co., Ltd.) Add 5 ml, 0.5 g phenoxyethanol, 0.1 g benzoisothiazolinone, add water to make a total amount of 750 g, and use 26 ml of 4% by weight chromium alum mixed with a static mixer just before coating. The solution was fed to the coating die so as to be 18.6 ml / m ² . The viscosity of the coating solution was 20 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

<Preparation of surface protective layer second layer coating solution>
Inert gelatin (80 g) is dissolved in water, and methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5/2) latex 27.5% by mass solution 102 g, 3.2 ml of a 5% by mass solution of a fluorosurfactant (F-1: N-perfluorooctylsulfonyl-N-propylalanine potassium salt), a fluorosurfactant (F-2: polyethylene glycol mono (N- Perfluorooctylsulfonyl-N-propyl-2-aminoethyl) ether [ethylene oxide average polymerization degree = 15]) 2% by mass aqueous solution 32 ml, aerosol OT (manufactured by American Cyanamid Co., Ltd.) 5% mass solution 23 ml , 4 g of polymethyl methacrylate fine particles (average particle size 0.7 μm), Water so that the total amount is 650 g in 21 g of dimethyl methacrylate fine particles (average particle size 4.5 μm), 1.6 g of 4-methylphthalic acid, 4.8 g of phthalic acid, 44 ml of 0.5 mol / L sulfuric acid, and 10 mg of benzoisothiazolinone. Was added with 445 ml of an aqueous solution containing 4% by weight of chromium alum and 0.67% by weight of phthalic acid using a static mixer immediately before coating, to obtain 8.3 ml / m ² as a surface protective layer coating solution. Then, the solution was fed to the coating die. The viscosity of the coating solution was 19 [mPa · s] at 40 ° C. (No. 1 rotor, 60 rpm) B-type viscometer.

[Preparation of photothermographic material]
On the back surface side of the undercoat support, the antihalation layer coating solution is applied so that the solid coating amount of the solid fine particle dye is 0.04 g / m ^2, and the back surface protective layer coating solution is prepared with a gelatin coating amount of 1. A simultaneous multilayer coating was applied so as to be 7 g / m ² , followed by drying to produce a back layer.

A photothermographic material sample was applied simultaneously on the surface opposite to the back surface by the slide bead coating method in the order of the image forming layer, the intermediate layer, the first surface protective layer, and the second surface protective layer from the undercoat surface. 11-20 were produced. At this time, the image forming layer and the intermediate layer were adjusted to 35 ° C., the surface protective layer first layer was adjusted to 36 ° C., and the surface protective layer first layer was adjusted to 37 ° C. The coating amount (g / m ² ) of each compound in the image forming layer is as follows.

Silver behenate 6.19
Pigment (C.I. Pigment Blue 60) 0.036
Polyhalogen compound-2 0.04
Polyhalogen compound-3 0.12
Phthalazine Compound-1 0.21
SBR latex 11.1
Reducing agent complex-3 1.54
Mercapto Compound-1 0.002
Silver halide (as Ag) 0.10
The coating and drying conditions are as follows. The coating was performed at a speed of 160 m / min, the gap between the coating die tip and the support was set to 0.10 to 0.30 mm, and the pressure in the decompression chamber was set to 196 to 882 Pa lower than the atmospheric pressure. The support was neutralized with an ion wind before coating. In the subsequent chilling zone, after cooling the coating solution with wind at a dry bulb temperature of 10 to 20 ° C., the coating solution is transported in a non-contact manner, and dried at a dry bulb temperature of 23 to 45 ° C. It dried with the dry wind of the wet bulb temperature 15-21 degreeC. After drying, the humidity was adjusted at 25 ° C. and humidity of 40 to 60% RH, and then the film surface was heated to 70 to 90 ° C. After heating, the film surface was cooled to 25 ° C.

  The photothermographic material thus produced had a matte degree of Beck smoothness of 550 seconds on the image forming layer surface side and 130 seconds on the back surface. Further, the pH of the film surface on the image forming layer side was measured and found to be 6.0.

  The obtained sample was cut into half-cut sizes, packaged in the following packaging materials in an environment of 25 ° C. and 50% RH, stored at room temperature for 2 weeks, and then evaluated as follows.

[Packaging materials]
As a packaging material for packaging the photothermographic material of the present invention, a material having the following layer constitution, oxygen permeability, and moisture permeability was used.

Layer structure: PET (polyethylene terephthalate) 10 μm / PE (polyethylene) 12 μm / aluminum foil 9 μm / Ny (nylon) 15 μm / polyethylene 50% polyethylene 3%
Oxygen permeability: 0 ml / atm · m ² · 25 ° C · day Moisture permeability: 0 g / atm · m ² · 25 ° C · day
[Evaluation of photographic performance]
For the heat-developable halogenated photographic light-sensitive material produced in Example 2, the exposure was performed by mounting a NLHV3000E semiconductor laser from Nichia Corporation as a semiconductor laser light source in the exposure part of the dry laser imager, and reducing the beam diameter. was exposed sensitive material at 10 ^-6 seconds the photosensitive material surface illuminance of the laser light was varied between 0 and ^{1mW / mm 2 ~1000mW / mm 2} . The emission wavelength of the laser beam was 405 nm.

The development was performed using the thermal development section of a medical dry laser imager and setting the temperature of the four panel heaters to 112 ° C.-119 ° C.-121 ° C.-121 ° C. The development time was 19 seconds in total.
(Evaluation)
Evaluation was performed in the same manner as in Example 1 (however, Dmax was omitted). The results are shown in Sample No. 11 is a relative value with reference 100.

  As is apparent from Table 4, the photothermographic material sample of the present invention has high sensitivity, low fog, the highest density is sufficiently high, the silver tone is good, the raw storage property is excellent, and the image light stability is excellent. It turns out that it is excellent. In particular, it can be seen that even when stored raw for a long period of time, high sensitivity and low fog can be maintained, and image light stability is excellent. It can also be seen that it has suitability as a medical photosensitive material.

  Further, in the same manner as in Example 1, it was confirmed that there was no spectral sensitivity due to the spectral sensitizing dye even after exposure after actual appearance (heat development without exposure).

Claims (7)

In a silver salt photothermographic dry imaging material containing photosensitive silver halide grains sensitized with a spectral sensitizing dye, non-photosensitive aliphatic carboxylic acid silver salt particles, a silver ion reducing agent, a binder and a crosslinking agent, The photosensitive silver halide grains are surface latent image type silver halide grains before thermal development, and are converted into inner latent type silver halide grains after thermal development, and the spectral sensitizing dye is oxidized by heat during thermal development. Alternatively, a silver salt photothermographic dry imaging material in which the spectral sensitization sensitivity due to the spectral sensitizing dye disappears after thermal development by thermal decomposition. The silver salt according to claim 1, wherein the spectral sensitizing dye is at least one selected from spectral sensitizing dyes represented by the following general formulas [Ia] to [Id]: Photothermographic dry imaging material.

[Wherein Z ₁₁ , Z ₁₂ , Z ₂₁ , Z ₂₂ , Z ₃₁ , Z ₄₁ and Z ₄₂ are each necessary to complete a monocyclic or condensed 5- or 6-membered nitrogen-containing heterocycle. Q ₃₁ , Q ₃₂ and Q ₄₁ each represents an oxygen atom, a sulfur atom, a selenium atom or —N (R) —, wherein R is an alkyl group, an aryl group or a heterocyclic ring. Represents a group. R ₁₁ , R ₁₂ , R ₂₁ , R ₂₂ , R ₃₁ , R ₄₁ and R ₄₃ each represent an aliphatic group, and R ₃₂ , R ₃₃ and R ₄₂ each represent an alkyl group, an aryl group or a heterocyclic ring. Represents a group. _{R 13, R 14, R 15} , R 16, R 17, R 23, R 24, R 25, R 26, R 27, R 28, R 29, R 34, R 35, R 36, R 37, R 38 , R ₃₉ , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ and R ₄₉ are each a hydrogen atom, a substituted or unsubstituted alkyl group, alkoxyl group, aryloxy group, aryl group, —N ( W ₁ , W ₂ ), —SR or a heterocyclic group. Here, R represents an alkyl group, an aryl group, or a heterocyclic group, W ₁ and W ₂ each represents a substituted or unsubstituted alkyl group or aryl group, and W ₁ and W ₂ are connected to each other to form 5 It is also possible to form a 6-membered or 6-membered nitrogen-containing heterocycle. R ₁₁ and R _13, R ₁₄ and R _16, R ₁₇ and R _12, R ₂₁ and R _23, R ₂₄ and R _26, R ₂₅ and R _27, R ₂₆ and R _28, R ₂₂ and R _29, R ₃₁ And R ₃₄ , R ₃₅ and R ₃₇ , R ₄₁ and R ₄₄ , R ₄₅ and R _47, and R ₄₉ and R ₄₃ can be connected to each other to form a 5-membered or 6-membered ring. X ₁₁ , X _21, and X ₄₁ each represent an ion required to cancel the charge in the molecule, and m 11, m _21, and m ₄₁ each represent the number of ions required to cancel the charge in the molecule. n11, n12, n21, n22, n31, n41, and n42 each represent 0 or 1, and l31, l32, l33, l41, l42, and l43 each represent 0 or 1. ] The spectral sensitizing dye is a spectral sensitizing dye having an oxidation potential of less than 1 volt and a difference between an oxidation potential and a reduction potential of 2 volts or more. Silver salt photothermographic dry imaging material. The silver salt photothermographic dry imaging material according to any one of claims 1 to 3, wherein the photosensitive silver halide grains have an average equivalent-circle diameter of 10 to 90 nm. The silver salt photothermographic dry imaging material according to any one of claims 1 to 4, further comprising a water-soluble binder. Image formation of a silver salt photothermographic dry imaging material, wherein the silver salt photothermographic dry imaging material according to any one of claims 1 to 5 is exposed to light having a wavelength of 700 nm or less to form an image. Method. The silver salt photothermographic dry imaging material according to claim 1, wherein the silver salt photothermographic dry imaging material according to claim 1 is exposed to light, heated at 80 to 150 ° C., and developed in 5 to 20 seconds. Image forming method of imaging material.