JP2006235174A - Heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material having a high maximum density, little fog, a good cold black tone as a silver tone and excellent image storage stability. <P>SOLUTION: The heat developable photosensitive material has on a support an image forming layer containing a non-photosensitive organic silver salt, a silver halide, a silver ion reducing agent and a binder, wherein at least one kind of the silver ion reducing agent is a compound represented by formula (1) and the heat developable photosensitive material contains a compound (leuco dye) represented by formula (2). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material, and more particularly to a photothermographic material excellent in sensitivity, silver tone, and image storage stability.

  In recent years, there has been a strong demand for a photosensitive material free from a developing solution waste in terms of environmental protection and workability in the medical and printing fields. For example, U.S. Pat. Nos. 3,152,904 and 3,487,075 and D.I. The method described in “Dry Silver Photographic Materials” by Morgan (Handbook of Imaging Materials, Marcel Dekker, Inc. 48, 1991) is well known. Since these photosensitive materials are usually developed at a temperature of 80 ° C. or higher, they are called photothermographic materials.

  The photothermographic material has a much larger number of kinds and added amounts of built-in chemical substances than the conventional photosensitive material processed by liquid processing, and accordingly, the film thickness of the photosensitive layer and the non-photosensitive layer is increased. It tends to increase. As a result, the coating process or the drying process at the time of manufacturing the light-sensitive material requires a lot of time and has the disadvantage that the productivity is lowered.

  In general, it is widely known that reducing the amount of silver is effective in reducing the film thickness in a photosensitive material. However, mere reduction of the amount of silver is not preferable because it causes a decrease in image density. In order to reduce the silver amount and not reduce the image density, it is effective to increase the number of development points per unit area and increase the covering power. Conventionally, a technology for obtaining a high image density with a small amount of silver has been established by using “infectious development” with a nucleating agent to increase the covering power in a photosensitive material for printing (see Patent Documents 1 and 2). ).

  However, many of the light-sensitive materials using a conventionally known nucleating agent have poor storage stability and the color tone of the formed image silver is yellowish, which is not preferable because it causes a decrease in diagnostics particularly in medical applications.

  The photothermographic material has been frequently used for medical diagnosis because of its convenience. Since a medical diagnostic image requires fine depiction, it requires a high image quality that is excellent in sharpness and graininess, and has a feature that a cold black image is preferred from the viewpoint of ease of diagnosis. However, it is difficult to produce a pure black color tone with a photothermal image forming system using an organic silver salt, and the color tone is adjusted with a color tone agent or the like, but the color tone control is not sufficient, and improvement is desired.

  As a technique for improving this defect, a combination of a specific reducing agent and a specific compound is disclosed (see Patent Documents 3 and 4), but the improvement effect is not sufficient, and the concentration tends to change during storage. Etc., and further improvement has been demanded.

On the other hand, diazo dyes have been disclosed as reagents for quantifying alcohol or the like by oxidative coloring with hydrogen peroxide or hydrogen peroxide (see Patent Document 5). Is not yet known, and there is of course no example of adding it to a photosensitive material for heat development.
Japanese National Patent Publication No. 10-512061 Japanese National Patent Publication No. 11-511571 JP 2002-169249 A JP 2002-236334 A JP 2004-267067 A

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is a heat development having a high maximum density, a low fog, a cool black tone having a good silver tone, and excellent image storage stability. It is to provide a photosensitive material.

  The above object of the present invention has been achieved by the following constitution.

(Claim 1)
In a photothermographic material having an image forming layer containing a non-photosensitive organic silver salt, silver halide, silver ion reducing agent and binder on a support, at least one silver ion reducing agent is represented by the general formula (1 And a photothermographic material comprising a compound represented by the following general formula (2):

[Wherein, R ₁ and R ₂ each represent a hydrogen atom, an aliphatic group or an aromatic group. R ₃ and R ₄ each represent a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Q represents a substitutable group on the benzene ring, and n represents an integer of 0 to 2. When there are a plurality of Q, each Q may be the same or different. ]

[Wherein Y ₁ and Y ₂ each represent —O—, —S—, —N (R ₁₃ ) — or —C (R ₁₄ ) (R ₁₅ ) —, and each of R ₁₃ , R ₁₄ and R ₁₅ Each represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. R ₁₁ and R ₁₂ each represent a hydrogen atom or a substituent. X ₁ and X ₂ each represents a group that can be substituted on the benzene ring. m1 and m2 each represent an integer of 0-4. When m1 and m2 are 2 or more, X ₁ and X ₂ may be the same or different, and may be connected to each other to form a ring. ]
(Claim 2)
2. The photothermographic material according to claim 1, wherein Y ₁ and Y ₂ in the general formula (2) are —S—.

(Claim 3)
3. The photothermographic material according to claim 1, wherein R ₃ in the general formula (1) is a secondary or tertiary alkyl group.

(Claim 4)
4. The photothermographic material according to claim 1, wherein R ₄ in the general formula (1) is an alkyl group having 2 or more carbon atoms.

(Claim 5)
The addition amount ratio (molar ratio) of the compound represented by the general formula (2) and the compound represented by the general formula (1) is 0.001 to 0.15. The photothermographic material according to claim 1.

(Claim 6)
6. The photothermographic material according to claim 5, wherein the molar ratio is 0.005 to 0.1.

(Claim 7)
7. The photothermographic material according to claim 1, wherein the silver halide contains 5 to 100 mol% of silver iodide.

(Claim 8)
8. The photothermographic material according to claim 1, wherein the non-photosensitive organic silver salt contains 70% by mass or more and less than 100% by mass of silver behenate.

  According to the present invention, the maximum image density and fog deterioration due to the action of light and heat during storage are very small, and the image has a cool image tone, and the color tone of the image is deteriorated with respect to light and heat. The output image is extremely small and suitable as a diagnostic image.

  Details of the present invention will be described below.

  In the present invention, at least one of the silver ion reducing agents is represented by the general formula (2) alone or in combination with a reducing agent having another different chemical structure, which is a specific bisphenol derivative. In combination with other compounds. As a result, the color tone of the image is a preferable cool black tone, and deterioration of the color tone in storing a silver image after heat development can be unexpectedly suppressed. Furthermore, a surprising effect such as obtaining an image excellent in processing fluctuation resistance can be obtained.

  First, the compound represented by the general formula (1) will be described.

In the general formula (1), R ₁ and R ₂ each represent a hydrogen atom, an aliphatic group, or an aromatic group, and the “aliphatic group” in this specification refers to a substituted or unsubstituted alkyl, respectively. Group, cycloalkyl group, alkenyl group, cycloalkenyl group, alkynyl group, aralkyl group.

  Specific examples of the aliphatic group include methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, hexyl, decyl, dodecyl, pentadecyl group, vinyl group, allyl, ethynyl, propargyl, cyclopropyl, cyclobutyl , Cyclobutenyl, cyclopentyl, cyclopentenyl, cyclopentadienyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, cycloheptyl, cycloheptynyl, cycloheptadienyl, cyclooctanyl, cyclooctenyl, cyclooctadienyl, cyclooctatrienyl, cyclononanyl, Examples include cyclononenyl, cyclononadienyl group, cyclononatrienylcyclodecanyl, cyclodecenyl, cyclodecadienyl, cyclodecatrienyl and the like. These groups may have a substituent at any position. Specific examples of the substituent include an alkyl group, a halogenated alkyl group, a halogen atom, a cyano group, an alkoxy group, a hydroxyl group, an amino group, and a carboxyl group. Group, carbooxy group, aryl group, heterocyclic group, aryloxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group.

  The aromatic group may be a single ring or a condensed ring, and examples thereof include phenyl, naphthyl, anthracenyl, phenanthrenyl, naphthacenyl, triphenylenyl and the like. These rings may have various substituents at arbitrary positions, and as a preferable substituent, a linear or branched alkyl group (preferably having 1 to 20 carbon atoms, methyl, ethyl, propyl, i-- Propyl, dodecyl, etc.), alkoxy groups (preferably having 1 to 20 carbon atoms, methoxy, ethoxy, propoxy, i-propoxy, dodecyloxy, etc.), aliphatic acylamino groups (preferably having an alkyl group having 1 to 21 carbon atoms) Acetylamino, heptylamino, etc.), aromatic acylamino groups and the like.

R ₁ is preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, more preferably a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, still more preferably methyl, ethyl, i-propyl, Cyclohexyl and the like. R ₂ is preferably a hydrogen atom.

R ₃ and R ₄ each represent a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Specific examples of the aliphatic group and the aromatic group represented by R ₃ and R ₄ include the R Examples thereof include the same groups as the examples of the aliphatic group and the aromatic group represented by ₁ and R ₂ .

Specific examples of the heterocyclic group represented by R ₃ and R ₄ include aromatic heterocyclic groups such as pyridyl, quinolyl, isoquinolyl, imidazolyl, pyrazolyl, triazolyl, oxazolyl, thiazolyl, oxadiazolyl, thiadiazolyl, tetrazolyl, piperidinyl, and morpholinyl. , Non-aromatic heterocyclic groups such as tetrahydrofuryl, tetrahydrothienyl and tetrahydropyranyl. These groups may further have a substituent, and examples of the substituent include the above-described substituents on the ring.

R ₃ is preferably an alkyl group or a cycloalkyl group, and more preferably a secondary or tertiary alkyl group or a cycloalkyl group. R ₄ is preferably an alkyl group, more preferably an alkyl group having 2 or more carbon atoms.

  Q represents a substitutable group on the benzene ring, specifically, an alkyl group having 1 to 25 carbon atoms (methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl, etc.), halogen Alkyl group (trifluoromethyl, perfluorooctyl etc.), cycloalkyl group (cyclohexyl, cyclopentyl etc.), alkynyl group (propargyl etc.), glycidyl group, acrylate group, methacrylate group, aryl group (phenyl etc.), heterocyclic group (Pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atom (chlorine, bromine, iodine, fluorine, etc.), alkoxy group (methoxy, ethoxy , Poxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc.), aryloxy groups (phenoxy, etc.), alkoxycarbonyl groups (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl groups (phenyloxycarbonyl) ), Sulfonamide groups (methanesulfonamide, ethanesulfonamide, butanesulfonamide, hexanesulfonamide, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl groups (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl, butylaminosulfonyl) , Hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyridylaminosulfo ), Urethane groups (methylureido, ethylureido, pentylureido, cyclohexylureido, phenylureido, 2-pyridylureido, etc.), acyl groups (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.), Carbamoyl group (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, pentylaminocarbonyl, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl, etc.), amide group (acetamide, propionamide, butanamide, hexaneamide, Benzamide, etc.), sulfonyl groups (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexylsulfonyl, phenyl) Rusulfonyl, 2-pyridylsulfonyl, etc.), amino group (amino, ethylamino, dimethylamino, butylamino, cyclopentylamino, anilino, 2-pyridylamino, etc.), cyano group, nitro group, sulfo group, carboxyl group, hydroxyl group, An oxamoyl group can be exemplified. These groups may be further substituted with these groups.

  n represents an integer of 0 to 2, and most preferably n is 0. When Q is plural, each Q may be the same or different.

  The silver ion reducing agent represented by the general formula (1) (also referred to as the reducing agent of the present invention) can be synthesized by various methods. A typical scheme is shown below.

Preferably 2 equivalents of phenol (In the above scheme, R _1, R ₃ and R _4, but synonymous with R _1, R ₃ and R ₄ in each formula (1) shows the case of R ₂ = H) and Dissolve or suspend 1 equivalent of aldehyde in the absence of a solvent or in a suitable organic solvent, add a catalytic amount of acid or alkali, and preferably react at a temperature of −20 to 180 ° C. for 30 minutes to 60 hours. Can be obtained in good yield.

  The organic solvent is preferably a hydrocarbon organic solvent, and specific examples include benzene, toluene, xylene, dichloromethane, chloroform and the like. Preferred are toluene and xylene. Furthermore, from the viewpoint of yield, it is most preferable to carry out the reaction without a solvent. Although any inorganic acid and organic acid can be used as the acid catalyst, concentrated hydrochloric acid, p-toluenesulfonic acid and phosphoric acid are preferably used. As the alkali catalyst, sodium hydroxide, potassium hydroxide, triethylamine, DBU (1,8-diazabicyclo [5.4.0] undec-7-ene) and sodium methylate are preferably used. As a catalyst amount, it is preferable to use 0.001-1.5 equivalent with respect to a corresponding aldehyde. The reaction temperature is preferably 15 to 150 ° C., and the reaction time is preferably 3 to 20 hours.

  Although the typical example of the reducing agent of this invention is shown below, this invention is not limited to these.

  Next, the compound (leuco dye) represented by the general formula (2) will be described in detail.

In the general formula (2), Y ₁ and Y ₂ each represent —O—, —S—, —N (R ₁₃ ) —, —C (R ₁₄ ) (R ₁₅ ) —, and R ₁₃ , R ₁₄ and R ₁₅ each represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group.

Specific examples of the aliphatic group, aromatic group and heterocyclic group represented by R ₁₃ , R ₁₄ and R ₁₅ include the aliphatic group represented by R ₁₁ and R ₁₂ in the general formula (1), The example given as a specific example of an aromatic group and a heterocyclic group is mentioned. R ₁₃ is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and still more preferably a methyl or ethyl group.

R ₁₄ and R ₁₅ are preferably an alkyl group having 1 to 10 carbon atoms and an aromatic group, more preferably an alkyl group having 1 to 6 carbon atoms, and still more preferably a methyl, ethyl, propyl and butyl group.

Y ₁ and Y ₂ are preferably —O—, —S—, —N (R ₁₃ ) —, more preferably —O—, —S—, and still more preferably —S—.

R ₁₁ and R ₁₂ represent a hydrogen atom or a substituent, and specific examples of the substituent include an alkyl group (methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl, etc.), cycloalkyl Groups (cyclohexyl, cyclopentyl, etc.), aryl groups (phenyl, etc.), heterocyclic groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), alkoxy Carbonyl group (methoxycarbonyl, ethoxycarbonyl, butoxycarbonyl, etc.), aryloxycarbonyl group (phenoxycarbonyl, etc.), acyl group (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzo) Yl, pyridinoyl, etc.), a carbamoyl group (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propyl aminocarbonyl, pentyl aminocarbonyl, cyclohexylaminocarbonyl, phenylaminocarbonyl, and 2-pyridylaminocarbonyl, etc.) and the like. These groups may be further substituted with these groups.

R ₁₁ and R ₁₂ each represent a hydrogen atom or a substituent, and the substituent is preferably an aliphatic group, an aromatic group or an acyl group.

Specific examples of the aliphatic group and aromatic group represented by R ₁₁ and R ₁₂ are given as examples of the aliphatic group and aromatic group represented by R ₁ and R ₂ in the general formula (1). Groups.

Specific examples of the acyl group represented by R ₁₁ and R ₁₂ include groups such as acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl and pyridinoyl.

R ₁₁ and R ₁₂ are preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and still more preferably an alkyl group having 1 to 4 carbon atoms.

X ₁ and X ₂ represent groups that can be substituted on the benzene ring, and specifically include alkyl groups having 1 to 25 carbon atoms (methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl, etc. ), Cycloalkyl groups (cyclohexyl, cyclopentyl, etc.), alkynyl groups (propargyl, etc.), glycidyl groups, acrylate groups, methacrylate groups, aryl groups (phenyl, etc.), heterocyclic groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl) , Pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atom (chlorine, bromine, iodine, fluorine, etc.), alkoxy group (methoxy, ethoxy, propoxy, pentyloxy, cyclopentyloxy, hexyloxy) , Cyclohexyloxy etc.), aryloxy group (phenoxy etc.), alkoxycarbonyl group (methoxycarbonyl, ethoxycarbonyl, butoxycarbonyl etc.), aryloxycarbonyl group (phenoxycarbonyl etc.), sulfonamide group (methanesulfonamide, ethanesulfonamide) , Butanesulfonamide, hexanesulfonamide, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl group (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl, butylaminosulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2 -Pyridylaminosulfonyl etc.), urethane group (methylureido, ethylureido, pentylureido, cyclo Xylureido, phenylureido, 2-pyridylureido, etc.), acyl groups (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.), carbamoyl groups (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl) , Pentylaminocarbonyl, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl, etc.), amide groups (acetamide, propionamide, butanamide, hexaneamide, benzamide, etc.), sulfonyl groups (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexyl) Sulfonyl, phenylsulfonyl, 2-pyridylsulfonyl, etc.), sulfonamide groups (methylsulfone) Octylsulfonamide, phenylsulfonamide, naphthylsulfonamide, etc.), amino group (amino, ethylamino, dimethylamino, butylamino, cyclopentylamino, anilino, 2-pyridylamino, etc.), cyano group, nitro group, sulfo group, A carboxyl group, a hydroxyl group, an oxamoyl group, etc. can be mentioned. These groups may be further substituted with these groups.

X ₁ and X ₂ are preferably an alkyl group, an alkoxy group, an aryloxy group and a halogen atom, more preferably an alkyl group and an alkoxy group.

m1 and m2 represent an integer of 0 to 4, but when m1 and m2 are 2 or more, X ₁ and X ₂ may be the same or different and may be connected to each other to form a ring. m1 and m2 are preferably 0 to 3, more preferably 0 or 1. Particularly preferably, m1 = m2 = 0.

  The compound represented by the general formula (2) can be easily synthesized by a conventionally known method such as the method described in Justus Liebigs Analder der Chemie, 1968, Vol. 711, pages 139 to 156.

  Although the specific example of a compound of General formula (2) is shown below, this invention is not limited to these.

  In the present invention, the amount of the compound of the general formula (2) / the amount of the compound of the general formula (1) is preferably 0.001 to 0.15 in terms of molar ratio, and 0.005 to 0. .1 is more preferred. When the molar ratio is less than 0.001, the effects of the present invention cannot be exhibited. When the molar ratio exceeds 0.15, fogging and deterioration of raw storage properties are observed, which is not preferable.

  The silver halide used in the photothermographic material of the present invention can inherently absorb light as an intrinsic property of silver halide crystals, or is visible or infrared light by an artificial physicochemical method. In the silver halide crystal and / or on the crystal surface when absorbing light in any region within the light wavelength range from the ultraviolet light region to the infrared light region. Refers to silver halide crystal grains that have been processed and produced so that can occur.

(Photosensitive silver halide grains)
The photosensitive silver halide grains themselves are P.I. By Glafkides: Chimie et Physique Photographic (published by Paul Montel, 1967), G. F. By Duffin: Photographic Emulsion Chemistry (published by The Focal Press, 1966), V.C. L. It can be prepared as a silver halide grain emulsion using a method described in Zelikman et al: Making and Coating Photographic Emulsion (published by The Focal Press, 1964). That is, any method such as an acidic method, a neutral method, and an ammonia method may be used, and the formation of a reaction between a soluble silver salt and a soluble halogen salt may be any one of a one-side mixing method, a simultaneous mixing method, and a combination thereof. Of these methods, the so-called controlled double jet method, in which silver halide grains are prepared while controlling the formation conditions, is preferred.

  The halogen composition is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide.

  Grain formation is usually divided into two stages: silver halide seed grain (nucleus) generation and grain growth, and these may be performed continuously at once, or the nucleus (seed grain) formation and grain growth are separated. It is also possible to do this. The controlled double jet method in which the particle formation is controlled by controlling the pAg, pH, etc., which are particle formation conditions, is preferable because the particle shape and size can be controlled. For example, when performing a method in which nucleation and grain growth are separated, first, a soluble silver salt and a soluble halogen salt are uniformly and rapidly mixed in an aqueous gelatin solution to form nuclei (seed grains) and then controlled. Silver halide grains are prepared by a grain growth process in which grains are grown while supplying a soluble silver salt and a soluble halogen salt under a pAg, pH, or the like. After the formation of the grains, the desired salt halide emulsion can be obtained by removing unnecessary salts by a desalting step by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, or an electrodialysis method. I can do it.

  The photosensitive silver halide grains according to the present invention preferably have a small average particle diameter in order to keep the white turbidity and color tone (yellowishness) after image formation low and to obtain good image quality. 0.035 to 0.055 μm is preferable as a value when particles less than 0.02 μm are excluded from measurement. The grain size referred to here means the length of the edge of the silver halide grain when the silver halide grain is a cubic or octahedral so-called normal crystal. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface.

  In the present invention, the silver halide grains are preferably monodispersed. The monodispersion mentioned here means that the coefficient of variation of the particle diameter obtained by the following formula is 30% or less. Preferably it is 20% or less, More preferably, it is 15% or less.

Coefficient of variation of particle size (%) = standard deviation of particle size / average value of particle size × 100
Examples of the shape of the silver halide grains include cubes, octahedrons, tetradecahedral grains, tabular grains, spherical grains, rod-like grains, and potato-like grains. Among these, cubic, octahedral, and tetrahedral Tabular silver halide grains are preferred.

  The average aspect ratio when using tabular silver halide grains is preferably 1.5 to 100, more preferably 2 to 50. These are described in US Pat. Nos. 5,264,337, 5,314,798, 5,320,958 and the like, and the desired tabular grains can be easily obtained. Further, grains having rounded corners of silver halide grains can be preferably used.

  There is no particular limitation on the crystal habit on the outer surface of the silver halide grain, but when using a spectral sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the silver sensitizing dye on the surface of the silver halide grain It is preferable to use silver halide grains having a relatively high proportion of crystal habits adapted to the selectivity. For example, when using a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100], the proportion of the [100] face on the outer surface of the silver halide grain is preferably high, and this ratio is 50 % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani: J.M. Imaging Sci. 29, 165 (1985).

  The silver halide grains used in the present invention are preferably prepared using low molecular weight gelatin having an average molecular weight of 50,000 or less at the time of forming the grains, but particularly preferably used at the time of nucleation of silver halide grains. The low molecular weight gelatin has an average molecular weight of 50,000 or less, preferably 2,000 to 40,000, more preferably 5,000 to 25,000. The average molecular weight of gelatin can be measured by gel filtration chromatography. Low molecular weight gelatin can be decomposed by adding gelatin-degrading enzyme to a commonly used gelatin aqueous solution with an average molecular weight of about 100,000, hydrolyzing by adding acid or alkali, and heating under atmospheric pressure or pressure. Can be obtained by thermal decomposition, decomposition by ultrasonic irradiation, or a combination of these methods.

  The concentration of the dispersion medium (gelatin) at the time of nucleation is preferably 5% by mass or less, and more effective at a low concentration of 0.05 to 3.0% by mass.

  For the silver halide grains, it is preferable to use a polyethylene oxide compound having the structure shown below when the grains are formed.

YO (CH ₂ CH ₂ O) _m (CH (CH ₃ ) CH ₂ O) _p (CH ₂ CH ₂ O) _n Y
In the formula, Y represents a hydrogen atom, —SO ₃ M or —CO—B—COOM, and M represents an ammonium group substituted with a hydrogen atom, an alkali metal atom, an ammonium group or an alkyl group having 5 or less carbon atoms, B represents a chain or cyclic group forming an organic dibasic acid. m and n each represents 0 to 50, and p represents 1 to 100.

  When the above-mentioned polyethylene oxide compound is used to produce a silver halide photographic light-sensitive material, a step of producing a gelatin aqueous solution, a step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, and coating an emulsion on a support. It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved in a process or the like, and the technique used as an antifoaming agent is described in, for example, JP-A-44-9497. Has been. The polyethylene oxide compound also functions as an antifoaming agent during nucleation.

  The polyethylene oxide compound is preferably used at 1% by mass or less, more preferably 0.01 to 0.1% by mass with respect to silver.

  The polyethylene oxide compound only needs to be present at the time of nucleation, and is preferably added in advance to the dispersion medium before nucleation, but it may be added during nucleation or an aqueous silver salt solution used during nucleation. Or added to an aqueous halide solution. Preferably, it is used by adding 0.01 to 2.0% by mass to the halide aqueous solution or both aqueous solutions. Also, it is preferably present for at least 50% of the nucleation step, more preferably 70% or more. The polyethylene oxide compound may be added as a powder or dissolved in a solvent such as methanol.

  The temperature at the time of nucleation is 5 to 60 ° C., preferably 15 to 50 ° C. Even if the temperature is constant, the temperature rising pattern (for example, the temperature at the start of nucleation is 25 ° C. It is preferable to control the temperature within the above temperature range even if the temperature is gradually raised and the temperature at the end of nucleation is 40 ° C.) and vice versa.

The concentration of the aqueous silver salt solution and aqueous halide solution used for nucleation is preferably 3.5 mol / L or less, and more preferably used in a low concentration range of 0.01 to 2.5 mol / L. The addition rate of silver ions during nucleation is preferably 1.5 × 10 ^{−3 to} 3.0 × 10 ⁻¹ mol / min, more preferably 3.0 × 10 ⁻³ to 8.times. 0 × 10 ⁻² mol / min.

  The pH at the time of nucleation can be set in the range of 1.7 to 10, but the pH on the alkali side is preferably pH 2 to 6 in order to broaden the particle size distribution of nuclei to be formed. Moreover, pBr at the time of nucleation is about 0.05 to 3.0, preferably 1.0 to 2.5, and more preferably 1.5 to 2.0.

  The silver halide grains may be added to the photosensitive layer (image forming layer) by any method. At this time, the silver halide grains are arranged so as to be close to the reducible silver source (aliphatic carboxylate silver salt). It is preferable to do this.

  The silver halide according to the present invention is prepared in advance and added to a solution for preparing the aliphatic carboxylic acid silver salt grains, and the silver halide preparing step and the aliphatic carboxylic acid silver salt particle preparing step are added. Although it is preferable from the viewpoint of production control because it can be handled separately, as described in British Patent 1,447,454, when preparing aliphatic carboxylate silver salt grains, halogen components such as halide ions are aliphatic. By coexisting with the carboxylate silver salt-forming component and injecting silver ions into this, it can be produced almost simultaneously with the production of the aliphatic carboxylate silver salt particles. It is also possible to prepare silver halide grains by converting a halogen-containing silver salt into an aliphatic carboxylic acid silver salt and converting the aliphatic carboxylic acid silver salt. 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.

  Examples of the 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. 4,009,039, 3,457,075, 4,003,749, British Patent 1,498,956 and JP-A-53-27027, 53-25420, metal halides, ammonium halides, etc. Inorganic halides such as trimethylphenylammonium bromide, cetylethyldimethylammonium bromide, onium halides such as trimethylbenzylammonium bromide; halogenated carbonization such as iodoform, bromoform, carbon tetrachloride, 2-bromo-2-methylpropane Hydrogens: N-bro Succinimide, N- bromo phthalimide, N- halogen compounds such as N- bromoacetamide; other, triphenylmethyl chloride, bromide triphenylmethyl, 2-bromoacetic acid, 2-bromo ethanol, dichloro benzophenone.

  Thus, silver halide can also be prepared by converting a part or all of silver in the organic acid silver salt into silver halide by the reaction between the organic acid silver and the halogen ion. Moreover, you may use together the silver halide grain manufactured by converting a part of aliphatic carboxylic acid silver salt into the silver halide prepared separately.

  These silver halide grains are separately prepared silver halide grains, silver halide grains by conversion of aliphatic carboxylic acid silver salts, 0.001 to 0.7 mol per 1 mol of aliphatic carboxylic acid silver salt, Preferably 0.03-0.5 mol is used.

  The silver halide grains preferably contain transition metal ions belonging to Groups 6 to 11 of the periodic table. As the metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, and Au are preferable. These may be used alone or in combination of two or more of the same or different metal complexes.

For these metal ions, the metal salt may be introduced as it is into the silver halide, but it can be introduced into the silver halide in the form of a metal complex or complex ion. The preferable content is in the range of 1 × 10 ⁻⁹ to 1 × 10 ⁻² mol, and more preferably in the range of 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ with ^respect to 1 mol of silver. 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 of the periodic table, L represents a ligand, and m represents 0,-, 2-, 3-, or 4-. Specific examples of the ligand represented by L include halides (fluoride, chloride, bromide and iodide), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aco. A ligand, nitrosyl, thionitrosyl and the like can be mentioned, and ako, nitrosyl, thionitrosyl and the like are preferable. 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 , May be added at any stage before or after chemical sensitization, but is preferably added at the stage of nucleation, growth and physical ripening, more preferably at the stage of nucleation and growth, most preferably Preferably, it is added at the stage of nucleation. In addition, it may be divided and added several times, or it can be uniformly contained in the silver halide grains. JP-A-63-29603, JP-A-2-306236, 3 As described in JP-A Nos. 167545, 4-76534, 6-110146, 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 (alcohols, ethers, glycols, ketones, esters, amides). For example, an aqueous solution of a metal compound powder or A method in which an aqueous solution in which a metal compound is dissolved together with sodium chloride and potassium chloride 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 at the same time. When adding a third aqueous solution, a method of preparing silver halide grains by a three-liquid simultaneous mixing method, a method of adding an aqueous solution of a required amount of a metal compound to the reaction vessel during grain formation, or silver halide There is a method of adding and dissolving another silver halide grain previously doped with metal ions or complex ions at the time of preparation. In particular, a method in which an aqueous solution of a metal compound powder or an aqueous solution in which a metal compound and sodium chloride and potassium chloride are dissolved together is added to the water-soluble halide solution. When added to the particle surface, a necessary 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 the physical ripening, or at the chemical ripening.

  The separately prepared photosensitive silver halide grains can be desalted by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, an electrodialysis method, etc., but may be used without desalting. it can.

(Non-photosensitive organic silver salt)
The non-photosensitive organic silver salt used in the present invention is a reducible silver source, is a salt of an organic acid containing silver ions, and is non-photosensitive. As the organic acid used in the present invention, aliphatic carboxylic acid, carbocyclic carboxylic acid, heterocyclic carboxylic acid, heterocyclic compound and the like are used.

  Examples of non-photosensitive organic acid silver salts are described in Research Disclosure, 17029 and 29963. Silver salts of aliphatic carboxylic acids (gallic acid, succinic acid, behenic acid, arachidic acid, stearic acid, palmitic acid, lauric acid) Silver salts of acids, etc .; silver carboxyalkylthiourea salts (1- (3-carboxypropyl) thiourea, 1- (3-carboxypropyl) -3,3-dimethylthiourea, etc.); aldehydes and hydroxy-substituted aromatic carboxylic acids Silver complexes of polymerization reaction products with acids (aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) and hydroxy-substituted aromatic carboxylic acids (salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid) Etc.) and silver complexes of thiones Are complexes (3- (2-carboxyethyl) -4-hydroxymethyl-4-thiazoline-2-thione and 3-carboxymethyl-4-thiazoline-2-thione), imidazole, pyrazole, urazole, 1,2, Nitric acid and silver complex or salt selected from 4-thiazole and 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; saccharin, 5-chlorosalicylaldoxime, etc. Silver salts; and silver salts of mercaptides.

  Among the above-mentioned organic silver salts, a silver salt of an aliphatic carboxylic acid is preferably used, and a silver salt of an aliphatic carboxylic acid having 10 to 30 carbon atoms, more preferably 15 to 25 carbon atoms. Examples of suitable silver salts include the following.

  Silver salts such as gallic acid, succinic acid, behenic acid, stearic acid, arachidic acid, palmitic acid and lauric acid. Among these, preferable silver salts include silver behenate, silver arachidate, and silver stearate. In the present invention, it is preferable that two or more types of aliphatic carboxylic acid silver salts are mixed in order to improve developability and form a silver image having a high density and high contrast. For example, two or more types of aliphatic carboxylic acids are used. It is preferable to prepare the mixture by mixing a silver ion solution.

  The aliphatic carboxylic acid silver salt compound can be obtained by mixing a water-soluble silver compound and a compound that forms a complex with silver, and is described in Japanese Patent Application Laid-Open No. 9-127643. The controlled double jet method as described above is preferably used. For example, an alkali metal salt (sodium hydroxide, potassium hydroxide, etc.) is added to an organic acid to produce an organic acid alkali metal salt soap (sodium behenate, sodium arachidate, etc.). A soap and silver nitrate are mixed to produce an aliphatic carboxylic acid silver salt crystal. At that time, silver halide grains may be mixed.

  In the aliphatic carboxylic acid silver salt according to the present invention, the average equivalent circle diameter can be adjusted in the range of 0.05 to 0.8 μm from the viewpoint of improving the transparency of the image after heat development and improving the image storage stability. Preferably, silver ions are appropriately supplied at the time of heat development, and the average thickness is preferably adjusted to 0.005 to 0.07 μm, particularly preferably from the viewpoint of improving the storage stability of the obtained image. The average equivalent circle diameter is 0.2 to 0.5 μm and the average thickness is adjusted to 0.01 to 0.05 μm.

  In order to obtain the average equivalent circle diameter, the dispersed aliphatic carboxylic acid silver salt is diluted and dispersed on a grid with a carbon support film, and the transmission electron microscope (manufactured by JEOL Ltd .: 2000FX type) is directly increased to 5000 times magnification. I took a picture. The negative is captured as a digital image with a scanner, and 300 or more particle sizes (equivalent circle diameter) are measured using appropriate image processing software, and the average particle size is calculated.

  The average thickness is calculated by a method using a TEM (transmission electron microscope) 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. . The prepared ultrathin slice was supported on a copper mesh, transferred onto a carbon film that had been made hydrophilic by glow discharge, and cooled with liquid nitrogen to −130 ° C. or lower using a transmission electron microscope (TEM). A bright field image is observed at 5,000 to 40,000 times, 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, it is preferable to use a very thin collodion or form bar supported by an organic film. More preferably, the carbon film is formed on a rock salt substrate and obtained by dissolving and removing the substrate. It is a carbon-only film obtained by solvent and ion etching. The TEM acceleration voltage 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 Japan Electron Microscopy Society Kanto Branch / Medical and Biological Electron Microscopy” (Maruzen), “The Japan Electron Microscopy Society Kanto Branch / Electron Microscope Biological Samples” "Manufacturing method" (Maruzen) can be referred to respectively.

  A TEM image recorded on an appropriate medium is preferably decomposed into at least 1024 pixels × 1024 pixels, preferably 2048 pixels × 2048 pixels or more, and image processing by a computer is performed. 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 aliphatic carboxylate silver is extracted by binarization processing.

  300 or more of the extracted aliphatic carboxylic acid silver salt particles are manually measured with appropriate software to obtain an average value.

  The method for obtaining the aliphatic carboxylic acid silver salt particles having the above-mentioned shape is not particularly limited, but includes a mixed state when forming an organic acid alkali metal salt soap and / or a mixed state when adding silver nitrate to the soap. It is effective to keep it well, to optimize the ratio of organic acid to soap, and the ratio of silver nitrate that reacts with soap.

  Tabular aliphatic carboxylic acid silver salt particles used in the present invention (aliphatic carboxylic acid silver salt particles having an average equivalent circle diameter of 0.05 to 0.8 μm and an average thickness of 0.005 to 0.07 μm) Is preferably preliminarily dispersed together with a binder, a surfactant or 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.

  As the media disperser, a rolling mill such as a ball mill, a planetary ball mill, and a vibrating ball mill, a bead mill that is a medium stirring mill, an attritor, and other basket mills can be used, and a high-pressure homogenizer includes a wall, Various types such as a type that collides with a plug or the like, a type that collides liquids at a high speed after dividing the liquid into a plurality of types, and a type that passes through a narrow orifice can be used.

Examples of ceramics 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 (titanium) _{strontium), 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, silicon nitride, yttrium-stabilized zirconia, zirconia-reinforced alumina, and the like are preferable. Yttrium-stabilized zirconia and zirconia-reinforced alumina (ceramics containing these 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.

  Ceramics such as zirconia, alumina, silicon nitride, boron nitride, or diamond as the material of the member in contact with the aliphatic carboxylate silver salt particles in the apparatus used when dispersing the flat aliphatic carboxylate silver salt particles Of these, it is preferable to use zirconia. When the above dispersion is performed, the binder concentration is preferably added in an amount of 0.1 to 10% of the mass of the aliphatic silver carboxylate, and it is preferable that the liquid temperature does not exceed 45 ° C. from the preliminary dispersion to the main dispersion. As preferable operating conditions for the present dispersion, for example, when a high-pressure homogenizer is used as the dispersing means, preferable operating conditions are 29.42 to 98.06 MPa, and the number of operations is preferably 2 times or more. Moreover, when using a media disperser as a dispersion | distribution means, a peripheral speed of 6-13 m / sec is mentioned as a preferable condition.

  In the present invention, the compound that functions as a crystal growth inhibitor or dispersant for the aliphatic carboxylate silver particles refers to a silver aliphatic carboxylate under the conditions in which the compound coexists in the production process of the aliphatic carboxylate particles. A compound having a function and an effect of reducing the particle size and monodispersing compared to when it is produced under conditions where it does not coexist. Specific examples include monohydric alcohols having 10 or less carbon atoms, preferably secondary alcohols, tertiary alcohols, glycols such as ethylene glycol and propylene glycol, polyethers such as polyethylene glycol, and glycerin. A preferable addition amount is 10 to 200% by mass with respect to the aliphatic carboxylate silver.

  On the other hand, branched aliphatic carboxylic acids containing isomers such as isoheptanoic acid, isodecanoic acid, isotridecanoic acid, isomyristic acid, isopalmitic acid, isostearic acid, isoarachidic acid, isobehenic acid and isohexaconic acid are also preferred. In this case, a preferable side chain includes an alkyl group or alkenyl group having 4 or less carbon atoms. Also, aliphatic unsaturated carboxylic acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, morotic acid, eicosenoic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosapentaenoic acid, docosahexaenoic acid, ceracolonic acid It is done. A preferable addition amount is 0.5 to 10 mol% of the aliphatic carboxylate silver.

  Glycosides such as glucoside, galactoside and fructoside, trehalose type disaccharides such as trehalose and sucrose, polysaccharides such as glycogen, dextrin, dextran and alginic acid, cellosolves such as methyl cellosolve and ethyl cellosolve, sorbitan, sorbit, ethyl acetate, Water-soluble organic solvents such as methyl acetate and dimethylformamide, water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylpyrrolidone, and gelatin Are also mentioned as preferred compounds. A preferable addition amount is 0.1 to 20% by mass with respect to aliphatic silver carboxylate.

  Alcohols having 10 or less carbon atoms, preferably secondary alcohols and tertiary alcohols, are monodispersed by increasing the viscosity of sodium aliphatic carboxylate in the preparation step and increasing the stirring efficiency. Reduce the particle size. Branched aliphatic carboxylic acids and aliphatic unsaturated carboxylic acids have higher steric hindrance than the main component linear aliphatic carboxylic acid silver when crystallization of the aliphatic carboxylic acid silver, and the disorder of the crystal lattice is large. Therefore, large crystals are not generated, and as a result, the particle size is reduced.

  As described above, compared to conventional silver halide photographic light-sensitive materials, the biggest difference in the composition of heat-developable light-sensitive materials is that the latter materials are fogged and printed regardless of before and after the development process. That is, it contains a large amount of photosensitive silver halide, organic silver salt and reducing agent that can cause out silver (baked out silver). For this reason, in order to maintain the storage stability not only before development but also after development, it is essential for the photothermographic material to have high fog prevention and image stabilization technology. In addition to aromatic heterocyclic compounds that suppress oxidization, mercury compounds such as mercury acetate having the function of oxidizing and extinguishing fog nuclei have been used as very effective storage stabilizers. Use was a major problem in terms of safety and environmental conservation.

(Anti-fogging agent, image stabilizer)
The antifogging and image stabilizer used in the photothermographic material of the present invention will be described below.

  In the photothermographic material of the present invention, since bisphenols are mainly used as the silver ion reducing agent, there is a compound that can inactivate the reducing agent by generating these active species capable of extracting hydrogen. It is preferable to contain. As the colorless photo-oxidizing substance, a compound capable of generating free radicals as reactive species upon exposure is preferable.

  Accordingly, any compound having these functions may be used, but an organic free radical composed of a plurality of atoms is preferred. A compound having any structure may be used as long as it has such a function and does not cause any particular adverse effect on the photothermographic material.

  These free radical-generating compounds include carbocyclic or heterocyclic rings so that the generated free radicals are stable enough to be in contact with the reducing agent for a sufficient period of time to be inactivated. Those having an aromatic group of the formula are preferred.

  Representative examples of these compounds include biimidazolyl compounds and iodonium compounds listed below.

  As the biimidazolyl compound, a compound represented by the following general formula [1] is preferably used.

In the formula, R ¹ , R ² and R ³ are each an alkyl group (methyl, ethyl, hexyl etc.), an alkenyl group (vinyl, allyl etc.), an alkoxy group (methoxy, ethoxy, octyloxy etc.), an aryl group (phenyl) , Naphthyl, tolyl etc.), hydroxyl group, halogen atom, aryloxy group (phenoxy etc.), alkylthio group (methylthio, butylthio etc.), arylthio group (phenylthio etc.), acyl group (acetyl, propionyl, butyryl, valeryl etc.), A sulfonyl group (methylsulfonyl, phenylsulfonyl, etc.), an acylamino group, a sulfonylamino group, an acyloxy group (acetoxy, benzoxy, etc.), a carboxyl group, a cyano group, a sulfo group, or an amino group is shown. Among these, more preferred substituents are an aryl group, an alkenyl group, a cyano group, and the like.

  The above-mentioned biimidazolyl compound can be produced by the production method described in US Pat. No. 3,734,733 and British Patent 1,271,177 and a method analogous thereto. As a preferable specific example, the compound example described in Unexamined-Japanese-Patent No. 2000-321711 can be mentioned, for example.

  Similarly, a suitable compound includes an iodonium compound represented by the following general formula [2].

Wherein Q ₁ includes the atoms necessary to complete a 5, 6 or 7 membered ring, and the required atoms are selected from carbon atoms, nitrogen atoms, oxygen atoms and sulfur atoms. R ¹¹ , R ¹² and R ¹³ are each a hydrogen atom, an alkyl group (methyl, ethyl, hexyl etc.), an alkenyl group (vinyl, allyl etc.), an alkoxy group (methoxy, ethoxy, octyloxy etc.), an aryl group (phenyl) , Naphthyl, tolyl etc.), hydroxyl group, halogen atom, aryloxy group (phenoxy etc.), alkylthio group (methylthio, butylthio etc.), arylthio group (phenylthio etc.), acyl group (acetyl, propionyl, butyryl, valeryl etc.), A sulfonyl group (methylsulfonyl, phenylsulfonyl, etc.), an acylamino group, a sulfonylamino group, an acyloxy group (acetoxy, benzoxy, etc.), a carboxyl group, a cyano group, a sulfo group, and an amino group are shown. Of these, more preferred substituents are an aryl group, an alkenyl group, and a cyano group.

R ¹⁴ represents a carboxylate group such as acetate, benzoate or trifluoroacetate and O 2 ⁻ . w represents 0 or 1;

X ⁻ represents an anionic counter ion, and preferred examples include CH ₃ COO ⁻ , CH ₃ SO ₃ ⁻ and PF ₆ ⁻ .

When R ¹³ is a sulfo group or a carboxyl group, W is 0 and, R ¹⁴ is O ^-. In addition, any two of R ¹¹ , R ¹² and R ¹³ may be bonded to each other to form a ring.

  Of these, particularly preferred compounds are those represented by the following general formula [3].

In the formula, R ²¹ , R ²² , R ²³ , R ²⁴ , X ⁻ and w are the same as R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and X ^{− in the} general formula [2], respectively. It represents a carbon atom (-CH =; benzene ring) or a nitrogen atom (-N =; pyridine ring).

  The above iodonium compounds are described in Org. Syn. , 1961 and Fiesser: Advanced Organic Chemistry (Reinhold, NY, 1961).

  Preferable specific examples include compounds described in, for example, JP-A No. 2000-321711.

The amount of the compound represented by the above general formulas [1] and [2] is 10 ⁻³ to 10 ⁻¹ mol / m ² , preferably 5 × 10 ^{−3 to} 5 × 10 ⁻² mol / m ² . . The compound can be contained in any constituent layer of the light-sensitive material of the present invention, but is preferably contained in the vicinity of the reducing agent.

  Further, as a compound that inactivates the reducing agent and prevents the reducing agent from reducing the aliphatic carboxylic acid silver salt to silver, a compound in which the reactive species is not a halogen atom is preferable, but a compound that releases a halogen atom as an active species is also available. Can be used in combination with a compound that releases an active species that is not a halogen atom. Many compounds capable of releasing a halogen atom as an active species are known, and a good effect can be obtained by the combined use.

  Specific examples of the compound that generates these active halogen atoms include compounds represented by the following general formula [4].

In the formula, Q ₂ represents an aryl group or a heterocyclic group. X ₁₁ , X ₁₂ and X ₁₃ each represent a hydrogen atom, a halogen atom, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group or an aryl group, at least one of which is a halogen atom. L represents —CO—, —SO— or —SO ₂ —.

The aryl group represented by Q ₂ may be monocyclic or condensed, preferably a monocyclic or bicyclic aryl group having 6 to 30 carbon atoms (phenyl, tolyl, naphthyl, etc.), more preferably Is a phenyl group or a naphthyl group, more preferably a phenyl group.

The heterocyclic group represented by Q ₂ is a 3- to 10-membered saturated or unsaturated heterocyclic group containing at least one of N, O, or S atoms, and these may be monocyclic or other A ring and a condensed ring may be formed. The heterocyclic group is preferably a 5- or 6-membered unsaturated heterocyclic group which may have a condensed ring, more preferably a 5- or 6-membered aromatic heterocyclic group which may have a condensed ring. is there. More preferably, it is a 5- or 6-membered aromatic heterocyclic group which may have a condensed ring containing a nitrogen atom, and particularly preferably 5 which may have a condensed ring containing 1 to 4 nitrogen atoms. Or a 6-membered aromatic heterocyclic group. The heterocyclic ring in such a heterocyclic group is preferably imidazole, pyrazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline Cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzothiazole, indolenine, tetrazaindene, more preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, Triazine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazo , Cinnoline, tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzothiazole, tetrazaindene, more preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, thiadiazole, quinoline, phthalazine, naphthyridine, Quinoxaline, quinazoline, cinnoline, tetrazole, thiazole, benzimidazole, and benzothiazole are preferable, and pyridine, thiadiazole, quinoline, and benzothiazole are particularly preferable.

The aryl group and heterocyclic group represented by Q ₂ may have a substituent in addition to —LC (X ₁₁ ) (X ₁₂ ) (X ₁₃ ). Group, alkenyl group, aryl group, alkoxy 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, heterocyclic group, more preferably alkyl group, aryl group, alkoxy group, Aryloxy group, acyl group, acylamino group, alkoxycarbonylamino group Aryloxycarbonylamino group, sulfonylamino 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, alkoxy group, An aryloxy group, an acyl group, an acylamino group, a sulfonylamino group, a sulfamoyl group, a carbamoyl group, a halogen atom, a cyano group, a nitro group, and a heterocyclic group, particularly preferably an alkyl group, an aryl group, and a halogen atom.

Examples of the substituent represented by X ₁₁ , X ₁₂ and X ₁₃ include a halogen atom, a haloalkyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group and a heterocyclic group. Preferred is a halogen atom, haloalkyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, sulfonyl group (alkylsulfonyl group, arylsulfonyl group), more preferred is a halogen atom or trihalomethyl group. Particularly preferred is a halogen atom. Of the halogen atoms, preferred are a chlorine atom, a bromine atom and an iodine atom, more preferred are a chlorine atom and a bromine atom, and particularly preferred is a bromine atom.

L represents —CO—, —SO— or —SO ₂ —, among which —SO ₂ — is preferably used.

  The amount of these compounds added is preferably within a range in which the increase in printout silver due to the formation of silver halide does not become a problem, and the ratio to the compound that does not generate active halogen radicals is 150% or less, more preferably It is preferable that it is 100% or less.

  In addition to the above compounds, the photothermographic material of the present invention may contain a compound conventionally known as an antifoggant, but generates a reactive species similar to the above compound. Even a compound that can be used may be a compound having a different antifogging mechanism. For example, U.S. Pat. Nos. 3,589,903, 4,546,075, 4,452,885, JP-A-59-57234, U.S. Pat. No. 3,874,946, 4,756,999. And compounds described in JP-A Nos. 9-288328 and 9-90550. Further, other antifoggants include compounds disclosed in US Pat. No. 5,028,523 and European Patents 600,587, 605,981, and 631,176.

  In the present invention, the silver ion reducing agent is preferably a bisphenol derivative represented by the general formula (1). The amount of silver ion reducing agent used varies depending on the type of organic silver salt, reducing agent, and other additives, but is generally 0.05 to 10 mol per mol of organic silver salt, but preferably 0.1-3 mol is suitable. Within this range, two or more silver ion reducing agents of the present invention may be used in combination. In the present invention, it may be preferable to apply the reducing agent to a photosensitive emulsion solution composed of photosensitive silver halide and organic silver salt grains and a solvent immediately before coating, since the variation in photographic performance due to stagnation time is small. is there.

  The photosensitive silver halide according to the present invention can be chemically sensitized. For example, a chemical sensitization center (chemical reaction) can be achieved by utilizing a compound that releases chalcogen such as sulfur or a noble metal compound that releases noble metal ions such as gold ions by a method described in Japanese Patent Application No. 2000-57004 and JP-A No. 2001-249426. Sensitizing nuclei) can be formed and imparted. It is preferably chemically sensitized with an organic sensitizer containing chalcogen atoms shown below.

  These organic sensitizers containing chalcogen atoms are preferably compounds having groups capable of adsorbing to silver halide and unstable chalcogen atom sites.

  As these organic sensitizers, organic sensitizers having various structures disclosed in JP-A-60-150046, JP-A-4-109240, JP-A-11-218874, and the like can be used. Of these, at least one compound having a structure in which a chalcogen atom is bonded to a carbon atom or a phosphorus atom by a double bond is preferable.

The amount of the chalcogen compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, etc., but is 10 ⁻⁸ to 10 ⁻ per mol of silver halide. ² mol is preferred, more preferably 10 ⁻⁷ to 10 ⁻³ mol. The chemical sensitization environment is not particularly limited, but in the presence of a compound capable of annihilating or reducing the size of silver chalcogenide or silver nuclei on photosensitive silver halide grains, and in particular silver nuclei. It is preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent that can be oxidized. As the sensitization condition, pAg is preferably 6 to 11, and more preferably 7 It is preferable that the pH is 4 to 10, more preferably 5 to 8, and the temperature is preferably 30 ° C. or lower for sensitization.

  Therefore, in the photothermographic material of the present invention, the photosensitive silver halide uses an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei on the grain, It is preferable to use a photosensitive emulsion that has been chemically sensitized at 30 ° C. or lower, mixed with an aliphatic carboxylic acid silver salt, dispersed, dehydrated and dried.

  Further, chemical sensitization using these organic sensitizers is preferably performed in the presence of a heteroatom-containing compound having adsorptivity to spectral sensitizing dyes or silver halide grains. By performing chemical sensitization in the presence of a compound having an adsorptivity to silver halide, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved. Although the spectral sensitizing dye will be described later, preferred examples of the heteroatom-containing compound having adsorptivity to silver halide include nitrogen-containing heterocyclic compounds described in JP-A-3-24537. As the heterocyclic ring in the nitrogen-containing heterocyclic compound, pyrazole, pyrimidine, 1,2,4-triazole, 1,2,3-triazole, 1,3,4-thiadiazole, 1,2,3-thiadiazole, 1,2 , 4-thiadiazole, 1,2,5-thiadiazole, 1,2,3,4-tetrazole, pyridazine, 1,2,3-triazine, a ring in which two or three of these rings are bonded, such as triazolotriazole, Examples of the ring include diazaindene, triazaindene, and pentazaindene. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, phthalazine, benzimidazole, indazole, benzothiazole ring and the like can also be applied.

  Among these, an azaindene ring is preferable, and an azaindene compound having a hydroxyl group as a substituent, such as a hydroxytriazaindene, tetrahydroxyazaindene, hydroxypentazaindene compound, or the like is more preferable.

  The heterocycle may have a substituent other than a hydroxyl group. Examples of the substituent include (substituted) alkyl groups, alkylthio groups, amino groups, hydroxyamino groups, alkylamino groups, dialkylamino groups, arylamino groups, carboxyl groups, alkoxycarbonyl groups, halogen atoms, cyano groups, and the like. May be.

The addition amount of these nitrogen-containing heterocyclic compounds varies over a wide range depending on the size, composition, and other conditions of the silver halide grains, but the approximate amount is the amount per mole of silver halide. In the range of 10 ⁻⁶ to 1 mol, preferably in the range of 10 ⁻⁴ to 10 ⁻¹ mol.

  The photosensitive silver halide according to the present invention can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, chloroaurate and organic gold compounds can be used as the gold sensitizer.

  In addition to the above-described sensitization methods, reduction sensitization methods and the like can also be used. Examples of reduction-sensitized shell-like compounds include ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, and borane. A compound, a silane compound, a polyamine compound, or the like can be used. Further, reduction sensitization can be performed by ripening the emulsion while maintaining the pH at 7 or higher or the pAg at 8.3 or lower.

  The silver halide subjected to chemical sensitization may be formed in the presence of an organic silver salt, formed in the absence of an organic silver salt, or a mixture of both. .

  The photosensitive silver halide is preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. As the spectral sensitizing dye, dyes such as cyanine, merocyanine, complex cyanine, complex merocyanine, holopolar cyanine, styryl, hemicyanine, oxonol, hemioxonol and the like can be used. For example, JP-A-63-159841, JP-A-60-140335, JP-A-63-231437, JP-A-63-259651, JP-A-63-304242, JP-A-63-15245, U.S. Pat. The sensitizing dyes described in US Pat. Nos. 4,740,455, 4,741,966, 4,751,175, and 4,835,096 can be used.

  Sensitizing dyes useful in the present invention are described, for example, in the literature described or cited in Section RD17643IV-A (December 1978, page 23) and Section 18431X (August 1978, page 437). In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light sources of various laser imagers and scanners. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

  Useful cyanine dyes are cyanine dyes having basic nuclei such as thiazoline nucleus, oxazoline nucleus, pyrroline nucleus, pyridine nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus and imidazole nucleus. Useful merocyanine dyes are preferably acidic nuclei such as thiohydantoin nucleus, rhodanine nucleus, oxazolidinedione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus in addition to the above basic nucleus. Including.

  In the present invention, a sensitizing dye having spectral sensitivity particularly in the infrared can also be used. Examples of infrared spectral sensitizing dyes preferably used include infrared spectral sensitizing dyes disclosed in U.S. Pat. Nos. 4,536,473, 4,515,888, and 4,959,294. It is done. As the infrared spectral sensitizing dye, a long-chain polymethine dye characterized in that a sulfinyl group is substituted on the benzene ring of the benzoazole ring is particularly preferable.

  The above-mentioned infrared sensitizing dyes are described in, for example, HM Hammer: The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dies and Related Compounds, published by A. Weissberger ed. The method can be synthesized by referring to the method.

  These infrared sensitizing dyes may be added at any time after the silver halide is prepared. For example, silver halide grains or silver halide grains / in a so-called solid dispersion state added to a solvent or dispersed in the form of fine particles. It can be added to a photosensitive emulsion containing aliphatic carboxylic acid silver salt grains. Similarly to the heteroatom-containing compound having adsorptivity to the silver halide grains, chemical sensitization can be performed after adding and adsorbing to the silver halide grains prior to chemical sensitization. Thus, dispersion of the chemically sensitized central core can be prevented, and high sensitivity and low fog can be achieved.

  The above spectral sensitizing dyes may be used alone or in combination, and the combination of sensitizing dyes is often used particularly for the purpose of supersensitization.

  The emulsion containing the photosensitive silver halide and the aliphatic carboxylic acid silver salt used in the photothermographic material of the present invention substantially contains a dye having no spectral sensitizing action or visible light itself together with the sensitizing dye. A substance that does not absorb and exhibits a supersensitization effect may be included in the emulsion to thereby supersensitize the silver halide grains.

  Useful sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in RD17643 (issued in December, 1978), page 23, Section J, Japanese Patent Publication No. 9-25500, 43. No.-4933, JP-A-59-19032, JP-A-59-192242, JP-A-5-341432, and the like, but as a supersensitizer, a heteroaromatic mercapto compound represented by the following, Or a mercapto derivative compound is preferable.

Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic ring or condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium or tellurium atoms. Preferably, the heteroaromatic ring is benzimidazole, naphthimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzotelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine , Purine, quinoline, or quinazoline. However, other heteroaromatic rings are also included.

  In addition, a mercapto derivative compound which substantially produces the above mercapto compound when contained in a dispersion of an aliphatic carboxylic acid silver salt and / or a silver halide grain emulsion is also included. In particular, mercapto derivative compounds represented below are preferred examples.

Ar-SS-Ar
Ar in the formula has the same meaning as in the case of the mercapto compound represented above.

  The heteroaromatic ring is, for example, a halogen atom (Cl, Br, I), a hydroxyl group, an amino group, a carboxyl group, an alkyl group (having one or more carbon atoms, preferably 1 to 4 carbon atoms) And a substituent selected from the group consisting of alkoxy groups (having one or more carbon atoms, preferably having 1 to 4 carbon atoms).

  In addition to the supersensitizer described above, compounds represented by the following general formula [5] and macrocycles disclosed in Japanese Patent Application No. 2000-70296 can be used as supersensitizers.

In the formula, H ³¹ Ar represents an aromatic hydrocarbon group or an aromatic heterocyclic group, T ₃₁ represents a divalent linking group or linking group composed of an aliphatic hydrocarbon group, and J ₃₁ represents an oxygen atom or a sulfur atom. Alternatively, it represents a divalent linking group or linking group containing one or more nitrogen atoms. Ra, Rb, Rc and Rd each represent a hydrogen atom, an acyl group, an aliphatic hydrocarbon group, an aryl group or a heterocyclic group, or between Ra and Rb, Rc and Rd, Ra and Rc, or Rb and Rd. It can combine to form a nitrogen-containing heterocyclic group. M ₃₁ represents an ion necessary for canceling the charge in the molecule, and k ₃₁ represents the number of ions necessary for canceling the charge in the molecule.

The divalent linking group comprising an aliphatic hydrocarbon group represented by T ₃₁ is a linear, branched or cyclic alkylene group (preferably having a carbon number of 1 to 20, more preferably 1 to 16, more preferably 1). To 12), an alkenylene group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16, more preferably 2 to 12), an alkynylene group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, still more preferably). 2 to 12) and may have a substituent. For example, as an aliphatic hydrocarbon group, a linear, branched or cyclic alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms). , More preferably 1 to 12), an alkenyl group (preferably 2 to 20 carbon atoms, more preferably 2 to 16, more preferably 2 to 12), an alkynyl group (preferably 2 to 20 carbon atoms, more preferably To 16 and more preferably 2 to 12), and the aryl group is a monocyclic or condensed aryl group having 6 to 20 carbon atoms (phenyl, naphthyl, etc., preferably phenyl), and a heterocyclic ring. As a group, a 3- to 10-membered saturated or unsaturated heterocyclic group (2-thiazolyl, 1-piperazinyl, 2-pyridyl, 3-pyridyl, 2-furyl, 2-thienyl, 2-benzimidazolyl, carbazolyl, etc.) Yes, the heterocyclic ring in these groups may be a single ring or may form a condensed ring with other rings. Each of these groups may have a substituent at an arbitrary position, for example, an alkyl group (including a cycloalkyl group and an aralkyl group, preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, Particularly preferably, it has 1 to 8 carbon atoms, such as methyl, ethyl, propyl, i-propyl, butyl, t-butyl, heptyl, octyl, decyl, undecyl, hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, benzyl, phenethyl and the like. An alkenyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms, such as vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an alkynyl group ( Preferably it has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms. Pargyl, 3-pentynyl, etc.), an aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyl, p-tolyl, o-aminophenyl) , Naphthyl, etc.), amino group (preferably having 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, particularly preferably 0 to 6 carbon atoms, such as amino, methylamino, ethylamino, dimethylamino, diethylamino , Diphenylamino, dibenzylamino, etc.), imino group (preferably having 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylimino, ethylimino, propylimino, phenyl Imino etc.) alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly C1-8, for example, methoxy, ethoxy, butoxy, etc.), aryloxy groups (preferably 6-20, more preferably 6-16, particularly preferably 6-12, Phenyloxy, 2-naphthyloxy, etc.), acyl groups (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as acetyl, benzoyl, formyl, pivaloyl, etc. ), An alkoxycarbonyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms such as methoxycarbonyl, ethoxycarbonyl, etc.), an aryloxycarbonyl group (preferably 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 10 carbon atoms. Phenyloxycarbonyl and the like), acyloxy groups (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 10 carbon atoms, such as acetoxy, benzoyloxy and the like), acylamino groups (preferably C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C10, for example, an acetylamino group, a benzoylamino group, etc., alkoxycarbonylamino group (preferably C2-C20, more) Preferably it has 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino, etc., aryloxycarbonylamino group (preferably 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, especially Preferably it has 7 to 12 carbon atoms, such as phenyloxycarbonylamino), sulfonyl Mino group (preferably having 1 to 20 carbon atoms, more preferably having 1 to 16 carbon atoms, particularly preferably having 1 to 12 carbon atoms, such as methanesulfonylamino, benzenesulfonylamino, etc.), sulfamoyl group (preferably having 0 carbon atoms) -20, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc.), carbamoyl group (preferably 1 carbon atom) To 20, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc., alkylthio groups (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms For example, methylthio, ethylthio, etc.), an arylthio group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms such as phenylthio), a sulfonyl group (preferably having 1 carbon atom). -20, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfonyl, tosyl, etc.), sulfinyl groups (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms). Particularly preferably, it has 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc., ureido group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms). For example, ureido, methylureido, phenylureido, etc.), phosphoric acid amide group (preferably having 1 to 20 carbon atoms) More preferably, it has 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. For example, diethyl phosphate amide, phenyl phosphate amide, etc.), hydroxyl group, mercapto group, halogen atom (fluorine, chlorine, bromine, iodine), cyano Group, sulfo group, sulfino group, carboxyl group, phosphono group, phosphino group, nitro group, hydroxamic acid group, hydrazino group, heterocyclic group (imidazolyl, benzoimidazolyl, thiazolyl, benzothiazolyl, carbazolyl, pyridyl, furyl, piperidyl, morpholino, etc.) Etc.

  Among the above groups, a salt-forming group such as a hydroxyl group, a mercapto group, a sulfo group, a sulfino group, a carboxyl group, a phosphono group, or a phosphino group may be a salt. These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. The substituent is preferably an alkyl group, aralkyl group, alkoxy group, aryl group, alkylthio group, acyl group, acylamino group, imino group, sulfamoyl group, sulfonyl group, sulfonylamino group, ureido group, amino group, halogen atom, nitro Group, heterocyclic group, alkoxycarbonyl group, hydroxyl group, sulfo group, carbamoyl group, carboxyl group, more preferably alkyl group, alkoxy group, aryl group, alkylthio group, acyl group, acylamino group, imino group, sulfonylamino Group, ureido group, amino group, halogen atom, nitro group, heterocyclic group, alkoxycarbonyl group, hydroxyl group, sulfo group, carbamoyl group, carboxyl group, more preferably alkyl group, alkoxy group, aryl group, alkylthio group , Acyl Amino group, an imino group, a ureido group, an amino group, a heterocyclic group, an alkoxycarbonyl group, a hydroxyl group, a sulfo group, a carbamoyl group, a carboxyl group. Examples of the amidino group include those having a substituent, and examples of the substituent include an alkyl group (each group such as methyl, ethyl, pyridylmethyl, benzyl, phenethyl, carboxybenzyl, and aminophenylmethyl), an aryl group (phenyl, each group such as p-tolyl, naphthyl, o-aminophenyl, o-methoxyphenyl), a heterocyclic group (2-thiazolyl, 2-pyridyl, 3-pyridyl, 2-furyl, 3-furyl, 2-thieno, 2 -Each group such as imidazolyl, benzothiazolyl, carbazolyl) and the like.

Examples of the divalent linking group containing at least one oxygen atom, sulfur atom or nitrogen atom represented by J ₃₁ include the following. A combination of these may also be used.

Here, Re and Rf are respectively synonymous with the contents defined by Ra to Rd in the general formula [5]. The aromatic hydrocarbon group represented by H ³¹ Ar is preferably one having 6 to 30 carbon atoms, more preferably a monocyclic or condensed aryl group having 6 to 20 carbon atoms, such as a phenyl group. , A naphthyl group, and the like, particularly preferably a phenyl group. The aromatic heterocyclic group is a 5- to 10-membered unsaturated heterocyclic group containing at least one atom of N, O and S. The heterocyclic ring in these groups may be monocyclic, A condensed ring may be formed with this ring. The heterocyclic ring in such a heterocyclic group is preferably a 5- to 6-membered aromatic heterocyclic ring and a benzo-fused ring thereof, more preferably a 5- to 6-membered aromatic heterocyclic ring containing a nitrogen atom and its benzoic ring. A condensed ring, more preferably a 5- to 6-membered aromatic heterocyclic ring containing 1 to 2 nitrogen atoms and a benzo-fused ring thereof.

  Specific examples of the heterocyclic group include, for example, thiophene, furan, pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, And groups derived from quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzothiazole, benzothiazoline, benzotriazole, tetrazaindene, carbazole and the like. The heterocyclic group is preferably imidazole, pyrazole, pyridine, pyrazine, indole, indazole, thiadiazole, oxadiazole, quinoline, phenazine, tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzothiazole, benzothiazoline, benzotriazole, A group consisting of tetrazaindene and carbazole, more preferably a group derived from imidazole, pyridine, pyrazine, quinoline, phenazine, tetrazole, thiazole, benzoxazole, benzimidazole, benzothiazole, benzothiazoline, benzotriazole, carbazole Is mentioned.

The aromatic hydrocarbon group and aromatic heterocyclic group represented by H ³¹ Ar may have a substituent, and examples of the substituent include the same groups as those exemplified as the substituent for T _31. The preferable range is also the same. These substituents may be further substituted, and when there are two or more substituents, each may be the same or different. The group represented by H ³¹ Ar is preferably an aromatic heterocyclic group.

Examples of the aliphatic hydrocarbon group, aryl group and heterocyclic group represented by Ra, Rb, Rc and Rd are the same as the specific examples of the aliphatic hydrocarbon group, aryl group and heterocyclic group in T ₃₁ . The preferable range is the same. The acyl group represented by Ra to Rd is an aliphatic or aromatic group having 1 to 12 carbon atoms, and specifically includes groups such as acetyl, benzoyl, formyl, and pivaloyl. The nitrogen-containing heterocyclic group formed by bonding between Ra and Rb, Rc and Rd, Ra and Rc, or Rb and Rd is a 3- to 10-membered saturated or unsaturated heterocyclic group (piperidyl, piperazinyl, acridinyl, Pyrrolidinyl, pyrrolyl, morpholino, morpholinyl, etc.).

As ions necessary for canceling out the charge in the molecule represented by M ₃₁ , specific examples of acid anions include halogen ions (chlorine ions, bromine ions, iodine ions, etc.), p-toluenesulfonic acid ions, perchloric acid. Ions, boron tetrafluoride ions, sulfate ions, methyl sulfate ions, ethyl sulfate ions, methanesulfonate ions, trifluoromethanesulfonate ions, and the like.

  The supersensitizer is preferably used in an amount of 0.001 to 1.0 mole per mole of silver in the photosensitive layer containing an organic silver salt and silver halide grains. Particularly preferred is an amount of 0.01 to 0.5 mole per mole of silver.

  Binders suitable for photothermographic materials are transparent or translucent and generally colorless, and are natural polymer synthetic resins, polymers and copolymers, and other media forming films such as gelatin, gum arabic, polyvinyl alcohol, hydroxyethyl cellulose, cellulose. Acetate, cellulose acetate butyrate, polyvinylpyrrolidone, casein, starch, polyacrylic acid, polymethylmethacrylic acid, polyvinyl chloride, polymethacrylic acid, copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene) -Butadiene), polyvinyl acetals (polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resins, polyvinylidene chloride, polyepoxides, polycar Sulfonates, polyvinyl acetate, cellulose esters, and polyamides. The binder may be hydrophilic or non-hydrophilic.

  Preferred binders for the photosensitive layer of the photothermographic material of the invention are polyvinyl acetals, and a particularly preferred binder is polyvinyl butyral. Details will be described later. For non-photosensitive layers such as overcoat layers and undercoat layers, especially protective layers and backcoat layers, cellulose esters which are polymers with higher softening temperatures, especially polymers such as triacetyl cellulose and cellulose acetate butyrate preferable. In addition, as needed, said binder can be used in combination of 2 or more type.

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 an aliphatic carboxylic acid silver salt in the photosensitive layer, the ratio of the binder to the aliphatic carboxylic acid silver salt is 15: 1 to 1: 2, particularly 8: 1 to 1: 1. A range is preferred. That is, it is preferable amount of the binder in the photosensitive layer is a 1.5~6g / m ^2. More preferably, it is 1.7-5 g / 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.

  In this invention, it is preferable that the heat transition point temperature after developing at the temperature of 100 degreeC or more is 46-200 degreeC. The heat transition temperature referred to in the present invention is a value indicated by the VICAT softening point or ring-and-ball method, and is a differential scanning calorimeter (DSC), for example, EXSTAR 6000 (manufactured by Seiko Denshi), DSC220C (manufactured by Seiko Denshi Kogyo). , DSC-7 (manufactured by Perkin Elmer) or the like, and refers to an endothermic peak when a thermally developed photosensitive layer is isolated and measured. In general, a polymer compound has a glass transition point (Tg), but in a photothermographic material, a large endothermic peak appears at a position lower than the Tg value of the binder resin used in the photosensitive layer.

  Tg is determined by the method described in “Polymer Handbook” III, pages 139 to 179 (1966, Wiley and Sun, Inc.) by Brand Wrap, etc., and Tg when the binder is a copolymer resin is Tg. It is obtained by the following formula.

Tg (copolymer) (° C.) = V ₁ Tg ₁ + v ₂ Tg ₂ +... + V _n Tg _n
Wherein, v1, v2 · · · vn represents the mass fraction of the monomer in the _{copolymer, Tg 1, Tg 2 ··· Tg} n is obtained from each monomer in the copolymer Represents the Tg (° C.) of a single polymer. The accuracy of Tg calculated according to the above equation is ± 5 ° C.

  In the photothermographic material of the invention, a conventionally known polymer compound is used as a binder contained in a photosensitive layer containing an aliphatic carboxylic acid silver salt, photosensitive silver halide grains, a reducing agent and the like on a support. be able to. The Tg is 70 to 105 ° C., the number average molecular weight is 1,000 to 1,000,000, preferably 10,000 to 500,000, and the degree of polymerization is about 50 to 1,000. Examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, (meth) acrylic acid, (meth) acrylic acid ester, vinylidene chloride, acrylonitrile, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether. And compounds comprising a polymer or copolymer containing an ethylenically unsaturated monomer as a constituent unit, polyurethane resins, and various rubber resins. Moreover, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone resin, epoxy-polyamide resin, polyester resin and the like can be mentioned. These resins are described in detail in “Plastic Handbook” issued by Asakura Shoten. These polymer compounds are not particularly limited, and may be either a homopolymer or a copolymer as long as the Tg of the derived polymer is in the range of 70 to 105 ° C.

  Polymers or copolymers containing such ethylenically unsaturated monomers as structural units include (meth) acrylic acid alkyl esters, (meth) acrylic acid aryl esters, cyanoacrylic acid alkyl esters, cyanoacrylic acid. Aryl esters and the like, and the alkyl group and aryl group thereof may or may not be substituted. Specifically, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, sec- Butyl, t-butyl, amyl, hexyl, cyclohexyl, benzyl, chlorobenzyl, octyl, stearyl, sulfopropyl, N-ethyl-phenylaminoethyl, 2- (3-phenylpropyloxy) ethyl, dimethylaminophenoxyethyl, furfuryl, Tetrahydrofurfuryl, phenyl, Gills, naphthyl, 2-hydroxyethyl, 4-hydroxybutyl, triethylene glycol, dipropylene glycol, 2-methoxyethyl, 3-methoxybutyl, 2-acetoxyethyl, 2-acetoacetoxyethyl, 2-ethoxyethyl, 2- iso-propoxyethyl, 2-butoxyethyl, 2- (2-methoxyethoxy) ethyl, 2- (2-ethoxyethoxy) ethyl, 2- (2-butoxyethoxy) ethyl, 2-diphenylphosphorylethyl, ω-methoxypolyethylene Examples include glycol (addition mole number n = 6), allyl, dimethylaminoethylmethyl chloride salt, and the like.

  In addition, the following monomers can be used. Specific examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl chloroacetate, vinyl methoxyacetate, vinyl phenyl acetate, vinyl benzoate, vinyl salicylate. N-substituted acrylamides, N-substituted methacrylamides and acrylamides, methacrylamides: N-substituents include methyl, ethyl, propyl, butyl, t-butyl, cyclohexyl, benzyl, hydroxymethyl, methoxyethyl, dimethyl Aminoethyl, phenyl, dimethyl, diethyl, β-cyanoethyl, N- (2-acetoacetoxyethyl), diacetone and the like; olefins: for example dicyclopentadiene, ethylene, propylene, 1-butene, 1- Nthene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, 2,3-dimethylbutadiene, etc .; styrenes: for example methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, t-butylstyrene, chloromethylstyrene, Methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, etc .; Vinyl ethers: for example, methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethyl vinyl ether, etc .; N-substituted maleimide Class: methyl, ethyl, propyl, butyl, t-butyl, cyclohexyl, benzyl, dodecyl, phenyl as N-substituent , 2-methylphenyl, 2,6-diethylphenyl, 2-chlorophenyl and the like; others include butyl crotonate, hexyl crotonate, dimethyl itaconate, dibutyl itaconate, diethyl maleate, dimethyl maleate, Dibutyl maleate, diethyl fumarate, dimethyl fumarate, dibutyl fumarate, methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone, glycidyl acrylate, glycidyl methacrylate, N-vinyl oxazolidone, N-vinyl pyrrolidone, acrylonitrile, methacrylonitrile, Examples thereof include methylenemalon nitrile and vinylidene chloride.

  Of these, particularly preferred examples include methacrylic acid alkyl esters, methacrylic acid aryl esters, and styrenes. Among such polymer compounds, it is preferable to use a polymer compound having an acetal group. The polymer compound having an acetal group is preferable because it is excellent in compatibility with the aliphatic carboxylic acid to be produced and has a great effect of preventing the film from being softened.

  As the polymer compound having an acetal group, a compound represented by the following general formula [6] is particularly preferable.

In the formula, R ₅₁ represents an alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group, but is preferably a group other than an aryl group. R ₅₂ represents an optionally substituted alkyl group, an optionally substituted aryl group, —COR ₅₃ or —CONHR ₅₃ . R ₅₃ is the same group as R ₅₁ .

The alkyl group represented by R ₅₁ , R ₅₂ and R ₅₃ is preferably an alkyl group having 1 to 20 carbon atoms, particularly preferably 1 to 6 carbon atoms. These may be linear or branched, and preferably a linear alkyl group. Examples of such an unsubstituted alkyl group include methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, amyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, t-octyl, 2 -Ethylhexyl, nonyl, decyl, dodecyl, octadecyl and the like are exemplified, and methyl or propyl is particularly preferable. As an aryl group, a C6-C20 thing is preferable, for example, phenyl, a naphthyl, etc. are mentioned.

  Examples of groups that can be substituted with the above alkyl group and aryl group include alkyl groups (methyl, propyl, t-amyl, t-octyl, nonyl, dodecyl, etc.), aryl groups (phenyl, etc.), nitro groups, hydroxyl groups, cyanos. Group, sulfo group, alkoxy group (such as methoxy), aryloxy group (such as phenoxy), acyloxy group (such as acetoxy), acylamino group (such as acetylamino), sulfonamide group (such as methanesulfonamide), sulfamoyl group (methylsulfuryl group) Famoyl etc.), halogen atoms (fluorine, chlorine, bromine etc.), carboxyl groups, carbamoyl groups (methylcarbamoyl etc.), alkoxycarbonyl groups (methoxycarbonyl etc.), sulfonyl groups (methylsulfonyl etc.) and the like. When there are two or more substituents, they may be the same or different. The total carbon number of the substituted alkyl group is preferably 1-20, and the total carbon number of the substituted aryl group is preferably 6-20.

As R ₅₂ , —COR ₅₃ (R ₅₃ is an alkyl group or aryl group) and —CONHR ₅₃ (R ₅₃ is an aryl group) are preferable. a, b, and c are values representing the mass of each repeating unit in mol%, and a = is in the range of 40 to 86 mol%, b = 0 to 30 mol%, c = 0 to 60 mol%, and a + b + c = A number representing 100 mol%, particularly preferably a = 50 to 86 mol%, b = 5 to 25 mol%, and c = 0 to 40 mol%. Each repeating unit having each composition ratio of a, b, and c may be composed of only the same one or different ones.

As the polyurethane resin that can be used, known resins such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the polyurethane shown here, if _{necessary, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, -O-P = O (OM) 2 (M is a hydrogen atom Or represents an alkali metal atom), —N (R ₅₄ ) ₂ , —N ⁺ (R ₅₄ ) ₃ (R ₅₄ represents a hydrocarbon group, and a plurality of R ₅₄ may be the same or different), an epoxy group It is preferable to use one in which at least one polar group selected from, -SH, -CN and the like is introduced by copolymerization or addition reaction. The amount of such a polar group is 10 ⁻¹ to 10 ⁻⁸ mol / g, preferably 10 ⁻² to 10 ⁻⁶ mol / g. In addition to these polar groups, it is preferred to have a total of two or more hydroxyl groups, at least one at each polyurethane molecule end. Since hydroxyl groups are cross-linked with polyisocyanate as a curing agent to form a three-dimensional network structure, it is more preferable that they are contained in the molecule. In particular, it is preferable that the hydroxyl group is at the molecular end because the reactivity with the curing agent is high. The polyurethane preferably has 3 or more hydroxyl groups at the molecular terminals, and particularly preferably 4 or more. When polyurethane is used, Tg is preferably 70 to 105 ° C., elongation at break is 100 to 2,000%, and stress at break is preferably 0.5 to 100 N / mm ² .

  The polymer compound represented by the general formula [6] can be synthesized by a general synthesis method described in “Vinyl acetate resin” edited by Ichiro Sakurada (Polymer Chemistry Press, 1962).

  These polymer compounds may be used alone as a binder, or two or more kinds may be blended and used. In the photosensitive silver salt-containing layer (preferably photosensitive layer) according to the present invention, the above polymer is used as a main binder. The main binder as used herein refers to “a state in which the polymer occupies 50% by mass or more of the total binder of the photosensitive silver salt-containing layer”. Therefore, other polymers may be blended and used within a range of less than 50% by weight of the total binder.

  These polymers are not particularly limited as long as the polymers according to the present invention are soluble. More preferably, polyvinyl acetate, a polyacrylic resin, a urethane resin, etc. are mentioned.

  By using a crosslinking agent for the binder, it is known that filming is improved and development unevenness is reduced, but there is also an effect of suppressing fogging during storage and suppressing generation of printout silver after development. is there.

  Examples of the crosslinking agent used include various crosslinking agents conventionally used for silver halide photographic light-sensitive materials, such as aldehyde-based, epoxy-based, ethyleneimine-based, and vinyl sulfone described in JP-A-50-96216. , Sulfonic acid ester-based, acryloyl-based, carbodiimide-based, silane compound-based cross-linking agents, and the like can be used. Preferred are isocyanate compounds, silane compounds, epoxy compounds, and acid anhydrides shown below.

  An isocyanate-based and thioisocyanate-based crosslinking agent represented by the following general formula [7], which is one of the preferable ones, will be described.

General formula [7] V = C = N−L− (N = C = V) _v
In the formula, v is 1 or 2, L is a residue of an alkyl group, alkenyl group, aryl group or alkaryl group, and is a (v + 1) -valent linking group, and V is an oxygen or sulfur atom.

  In the compound represented by the general formula [7], the aryl ring of the aryl group or alkaryl group may have a substituent. Examples of preferred substituents are selected from halogen atoms (bromine or chlorine), hydroxyl groups, amino groups, carboxyl groups, alkyl groups and alkoxy groups.

  The isocyanate-based crosslinking agent is an isocyanate having at least two isocyanate groups and adducts thereof (adducts), more specifically, aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, Benzene diisocyanates, naphthalene diisocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates and diisocyanates with these isocyanates and di- or trivalent polyalcohols And adducts with the above. As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used.

  The adduct body of isocyanate and polyalcohol has particularly high ability to improve interlayer adhesion, and prevent layer peeling, image shift and bubble generation. Such isocyanate may be placed in any part of the photothermographic material. For example, in the support (especially when the support is paper, it can be included in the size composition), photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc. It can be added to any of these layers, and can be added to one or more of these layers.

  As the thioisocyanate-based crosslinking agent that can be used in the present invention, compounds having a thioisocyanate structure corresponding to the above-mentioned isocyanates are also useful.

  The amount of the crosslinking agent used is in the range of 0.001 to 2 mol, preferably 0.005 to 0.5 mol, with respect to 1 mol of silver.

  The isocyanate compound and thioisocyanate compound that can be contained in the present invention are preferably compounds that function as the above-mentioned crosslinking agent, but in the above general formula, v is 0, that is, a compound having only one functional group. Even good results are obtained.

  Examples of the silane compound that can be used as a crosslinking agent in the present invention include compounds represented by general formula (1) or general formula (2) described in Japanese Patent Application No. 2000-77904.

In these general formulas, R _{1 to} R ₈ are each a linear, branched, or cyclic alkyl group having 1 to 30 carbon atoms (methyl, ethyl, butyl, octyl, dodecyl, cycloalkyl, etc.) that may be substituted. , Alkenyl groups (propenyl, butenyl, nonenyl, etc.), alkynyl groups (acetylene, bisacetylene, phenylacetylene, etc.), aryl groups or heterocyclic groups (phenyl, naphthyl, tetrahydropyranyl, pyridyl, furyl, thienyl, imidazolyl, thiazolyl, Thiadiazolyl, oxadiazolyl and the like), and the substituent may have either an electron-withdrawing substituent or an electron-donating substituent.

At least one of the substituents selected from R _{1 to} R ₈ is preferably a non-diffusible group or an adsorptive group, and R ₂ is particularly preferably a non-diffusible group or an adsorptive group.

  The non-diffusible group is also called a ballast group, and is preferably an aliphatic group having 6 or more carbon atoms or an aryl group into which an alkyl group having 3 or more carbon atoms is introduced. Diffusion resistance varies depending on the amount of binder and cross-linking agent used. By introducing a diffusion-resistant group, the intramolecular movement distance at room temperature is suppressed, and the reaction over time can be suppressed.

  The epoxy compound that can be used as the crosslinking agent is not particularly limited as long as it has one or more epoxy groups and the number of epoxy groups, molecular weight, and the like. The epoxy group is preferably contained in the molecule as a glycidyl group via an ether bond or an imino bond. The epoxy compound may be any of a monomer, an oligomer, a polymer and the like, and the number of epoxy groups present in the molecule is usually about 1 to 10, preferably 2 to 4. When the epoxy compound is a polymer, it may be either a homopolymer or a copolymer, and the number average molecular weight Mn is particularly preferably in the range of about 2,000 to 20,000.

  As the epoxy compound, a compound represented by the following general formula [8] is preferable.

In the formula, the substituent of the alkylene group represented by R ₉₀ is preferably a group selected from a halogen atom, a hydroxyl group, a hydroxyalkyl group or an amino group. The linking group represented by R ₉₀ preferably has an amide linking moiety, an ether linking moiety, or a thioether linking moiety. Examples of the divalent linking group represented by _{X 9, -SO 2 -, -} SO 2 NH -, - S -, - O-, or -NR ₉₁ - are preferred. Here, R ₉₁ is a monovalent group and is preferably an electron withdrawing group.

These epoxy compounds may be used alone or in combination of two or more. The addition amount is not particularly limited, but is preferably in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / m ² , more preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / m ² . It is.

  The epoxy compound can be added to any layer on the photosensitive layer side of the support, such as a photosensitive layer, a surface protective layer, an intermediate layer, an antihalation layer, and an undercoat layer, and one or more of these layers can be added. Can be added. Further, it can be added to any layer on the opposite side of the support from the photosensitive layer. In addition, any layer may be sufficient in the type of photosensitive material in which a photosensitive layer exists on both surfaces.

  An acid anhydride is a compound having at least one acid anhydride group represented by -CO-O-CO-.

  The acid anhydride only needs to have one or more such acid anhydride groups, and the number, molecular weight, and the like of the acid anhydride group are not limited, but the compound represented by the following general formula [9] Is preferred.

  In the formula, Z represents a group of atoms necessary to form a monocyclic or polycyclic system. These ring systems may have a substituent. Examples of substituents include alkyl groups (methyl, ethyl, hexyl, etc.), alkoxy groups (methoxy, ethoxy, octyloxy, etc.), aryl groups (phenyl, naphthyl, tolyl, etc.), hydroxyl groups, aryloxy groups (phenoxy, etc.) ), Alkylthio groups (methylthio, butylthio, etc.), arylthio groups (phenylthio, etc.), acyl groups (acetyl, propionyl, butyryl, etc.), sulfonyl groups (methylsulfonyl, phenylsulfonyl, etc.), acylamino groups, sulfonylamino groups, acyloxy groups ( Acetoxy, benzoxy and the like), carboxyl group, cyano group, sulfo group and amino group. As the substituent, those not containing a halogen atom are preferable.

These acid anhydrides may be used alone or in combination of two or more. The addition amount is not particularly limited, but is preferably in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / m ² , more preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / m ² . It is.

  In the present invention, the acid anhydride can be added to any layer on the photosensitive layer side of the support, such as a photosensitive layer, a surface protective layer, an intermediate layer, an antihalation layer, and an undercoat layer. It can be added to two or more layers. Moreover, you may add to the same layer as the said epoxy compound.

  The photothermographic material of the present invention forms a photographic image by heat development processing, and includes a reducible silver source (aliphatic carboxylic acid silver salt), photosensitive silver halide grains, a silver ion reducing agent, and a necessity. Accordingly, it is usually preferable to contain a color toning agent that adjusts the color tone of silver in a state dispersed in an (organic) binder matrix.

  Examples of suitable toning agents are disclosed in RD 17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. Particularly preferred color tones are phthalazinone or a combination of phthalazine and phthalic acids and phthalic anhydrides. Conventionally, regarding the color tone of an output image for medical diagnosis, it is said that a cold tone image tone is easier for a reader of an X-ray photograph to obtain a more accurate diagnostic observation result of a recorded image. Here, the cool image tone is a pure black tone or a bluish black tone of a black image, and the warm image tone is a warm black tone that a black image is brownish. Say that.

  In the present invention, the surface layer of the photothermographic material (when the photosensitive layer side or a non-photosensitive layer is provided on the opposite side of the photosensitive layer with the support interposed therebetween) is handled before development or after thermal development. It is preferable to contain a matting agent in order to prevent the image from being damaged, and it is preferable to contain 0.1 to 30% by mass with respect to the binder.

  The material of the matting agent may be either organic or inorganic. Examples of inorganic substances include silica described in Swiss Patent 330,158, glass powder described in French Patent 1,296,995, alkaline earth metal or cadmium described in British Patent 1,173,181, and the like. Further, carbonates such as zinc can be used as the matting agent. Examples of organic substances include starch described in U.S. Pat. No. 2,322,037, starch derivatives described in Belgian Patent 625,451 and British Patent 981,198, and polyvinyls described in Japanese Patent Publication No. 44-3643. Alcohol, polystyrene or polymethacrylate described in Swiss Patent 330,158, etc., polyacrylonitrile described in US Pat. No. 3,079,257, etc., and organic compounds such as polycarbonate described in US Pat. No. 3,022,169 A matting agent can be used.

  The matting agent preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm. The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less. Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

(Standard deviation of particle size / average value of particle size) × 100
The method of adding the matting agent may be a method in which the matting agent is dispersed in the coating solution in advance, or a method of spraying the matting agent after the coating solution is applied and before drying is completed. In addition, when a plurality of types of matting agents are added, both methods may be used in combination.

  Examples of the support material used in the photothermographic material of the present invention include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (for example, aluminum), etc. A material that can be processed into a flexible sheet or roll is preferred. Accordingly, the support according to the present invention is preferably a plastic film (cellulose acetate, polyester, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, cellulose triacetate, or polycarbonate film). Among them, biaxially stretched polyethylene terephthalate ( PET) film is particularly preferred. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  In the present invention, a conductive compound such as a metal oxide and / or a conductive polymer can be included in the constituent layers in order to improve the chargeability. These may be contained in any layer, but are preferably contained in an undercoat layer, a backing layer, an intermediate layer between the photosensitive layer and the undercoat layer, or the like. The conductive compounds described in US Pat. No. 5,244,773, columns 14 to 20 are preferably used.

  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. For example, a protective layer is provided on the photosensitive layer, and a back coat layer is provided on the opposite side of the support to prevent sticking between the photosensitive materials or in the photosensitive material roll. Preferably it is provided. Binders used in these protective layers and backcoat layers have a glass transition point higher than that of the heat-developable layer, and polymers such as scratches and deformations, such as cellulose acetate and cellulose acetate butyrate, It is chosen from among them. For the purpose of expanding the latitude, it is one of the preferred embodiments for the present invention to provide two or more photosensitive layers on one side of the support or one or more layers on both sides of the support.

  In the photothermographic material of the present invention, a filter layer is formed on the same side as or opposite to the photosensitive layer in order to control the amount of light transmitted through the photosensitive layer or the wavelength distribution, or a dye or pigment is contained in the photosensitive layer. It is preferable to make it.

  As the dye used, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the photosensitive material. For example, when the photothermographic material is an image recording material using infrared light, a squarylium dye having a thiopyrylium nucleus (referred to as a thiopyrylium squarylium dye) and a pyrylium nucleus as disclosed in JP-A-2001-83655 are used. It is preferred to use a squarylium dye (referred to as a pyrylium squarylium dye), or a thiopyrylium croconium dye or a pyrylium croconium dye similar to the squarylium dye. The compound having a squarylium nucleus is a compound having 1-cyclobutene-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy- in the molecular structure. It is a compound having 4,5-dione. Here, the hydroxyl group may be dissociated. Hereinafter, in the present specification, these pigments are collectively referred to as squarylium dyes for convenience. As the dye, compounds described in JP-A-8-201959 are also preferable.

  The photothermographic material is preferably formed by preparing a coating solution in which the above-described constituent layers are dissolved or dispersed in a solvent, applying a plurality of coating solutions simultaneously, and then performing a heat treatment. 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 this is coated on a support, the coating and drying are repeated for each layer individually. Rather, it means that each constituent layer can be formed in a state in which multiple layers can be simultaneously applied and dried. That is, 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 restrictions on the method of applying multiple layers of each constituent layer simultaneously. For example, a known method such as a bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, or extrusion coating method may be used. it can. Of these, a pre-weighing type coating method called an extrusion coating method is more preferable. The extrusion coating method is suitable for precision coating and organic solvent coating because there is no volatilization on the slide surface unlike the slide coating method. This coating method has been described on the side having the photosensitive layer, but the same applies to the case of coating with undercoating when providing the backcoat layer.

The amount of coated silver in the present invention is preferably selected in accordance with the purpose of the light-sensitive material, but is preferably 0.1 to 2.5 g / m ² for medical images. . Furthermore, 0.5 to 1.5 g / m ² is preferable. Among the applied silver amount, those derived from silver halide preferably occupy 2 to 18%, more preferably 3 to 15%, based on the total silver amount.

In the present invention, the coating density of silver halide grains having a particle diameter of 0.01 μm or more (equivalent sphere equivalent diameter) is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁸ particles / m ² . Furthermore, 1 * 10 < ¹⁵ > -1 * 10 < ¹⁷ > piece / m < ² > is preferable. Furthermore, the coating density of the aliphatic carboxylic acid silver salt is 10 ⁻¹⁷ to 10 ⁻¹⁵ g or less, more preferably 10 ⁻¹⁶ to 10 ⁻¹⁴ g per silver halide grain of 0.01 μm or more (equivalent particle diameter equivalent to a sphere). Is preferred.

  In the case of coating under the conditions within the above range, preferable results are obtained from the viewpoint of the optical maximum density of the silver image per fixed coating silver amount, that is, the silver coating amount (covering power) and the color tone of the silver image. Is obtained.

  The development conditions of the photothermographic material vary depending on the equipment, apparatus or means used, but typically involve heating the photothermographic material exposed imagewise at a suitable high temperature. The latent image obtained after exposure can be developed by heating the photothermographic material at a moderately high temperature (about 100 to 200 ° C.) for a sufficient time (generally about 1 second to about 2 minutes). When the heating temperature is 100 ° C. or less, sufficient image density cannot be obtained in a short time, and when the heating temperature exceeds 200 ° C., the binder melts, and transfer to a roller, not only the image itself but also transportability, developing machine, etc. It also has an adverse effect. By heating, a silver image is generated by a redox reaction between the aliphatic carboxylic acid silver salt (which functions as an oxidizing agent) and the reducing agent. This reaction process proceeds without any supply of treatment 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, in the photothermographic material provided with the protective layer of the present invention, the surface on the side having the protective layer is brought into contact with the heating means and is subjected to heat treatment. It is preferable from the viewpoint of workability and the like, and it is preferable that the surface is conveyed while being in contact with a heat roller, and is developed by heat treatment.

  For exposure of the photothermographic material, it is desirable to use a light source suitable for the color sensitivity imparted to the photosensitive material. For example, when the photosensitive material is sensitive to infrared light, it can be applied to any light source as long as it is in the infrared light range. However, the laser power is high and the photosensitive material can be transparent. In view of the above, an infrared semiconductor laser (780 nm, 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 between the exposure surface of the photosensitive material and the scanning laser beam is not substantially perpendicular. Here, “substantially not perpendicular” means that the angle 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 70-82 degrees.

  The beam spot diameter on the photosensitive material exposure surface when the laser beam is scanned onto the photosensitive material is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the angle of deviation of the laser incident angle from the vertical. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality degradation related to reflected light such as generation of interference fringe-like unevenness.

  As the second exposure method, it is also preferable to use 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, methods such as using return light by multiplexing and applying high-frequency superposition are preferable. The vertical multi means that the exposure wavelength is not single, and the distribution of the exposure wavelength is usually 5 nm or more, preferably 10 nm or more. The upper limit of the exposure wavelength distribution is not particularly limited, but is usually about 60 nm.

In the exposure methods of the first and second aspects described above, lasers used for scanning exposure include solid lasers such as ruby laser, YAG laser, and glass laser that are generally well known; HeNe laser, Ar ion laser, Gas lasers such as Kr ion laser, CO ₂ laser, CO laser, HeCd laser, N ₂ laser, and excimer laser; semiconductor lasers such as InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP ₂ laser, and GaSb laser A chemical laser, a dye laser, and the like can be selected and used in a timely manner, but among these, it is preferable to use a semiconductor laser having a wavelength of 600 to 1200 nm in view of maintenance and the size of the light source. 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 photosensitive material depending on the sensitivity and laser power at the laser oscillation wavelength unique to the photothermographic material.

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

Example 1
<Production of support>
After applying a corona discharge treatment of 0.5 kV · A · min / m ² to one surface of a blue-colored PET film base (thickness: 175 μm) having a concentration of 0.170, the following undercoat coating solution A is applied thereto. Was used to coat the undercoat layer a so that the dry film thickness was 0.2 μm. Further, the other surface was similarly subjected to a corona discharge treatment of 0.5 kV · A · min / m ² , and then the undercoat layer b was dried on the surface using the following undercoat coating solution B. Was coated to be 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 butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (30/20/25/25% ratio) copolymer latex liquid (solid content 30%), 0.6 g of surfactant (UL-1) And 0.5 g of methylcellulose were mixed. Further, 1.3 g of silica particles (Syloid 350: manufactured by Fuji Silysia) was added to 100 g of water, and the dispersion was subjected to a dispersion treatment for 30 minutes using an ultrasonic dispersing machine (manufactured by ALEX Corporation: Ultrasonic Generator, frequency 25 kHz, 600 W). Finally, it was made up to 1,000 ml with water to give a subbing coating solution A.
(Colloidal tin oxide dispersion)
A homogeneous solution was prepared by dissolving 65 g of stannic chloride hydrate in 2,000 ml of a water / ethanol mixed solution. Subsequently, this was boiled and the coprecipitate was obtained. The generated precipitate was taken out by decantation and washed several times with distilled water. Silver nitrate is dropped into distilled water from which the precipitate has been washed, and after confirming that there is no reaction of chlorine ions, distilled water is added to the washed precipitate to make a total volume of 2000 ml. Further, 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.
(Undercoating liquid B)
2. 37.5 g of the above colloidal tin oxide dispersion, butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (20/30/27/28% ratio) copolymer latex liquid (solid content 30%) 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 were mixed with water. Finished to 1,000 ml and used as the undercoat coating solution B.
(Back surface coating solution)
While stirring 830 g of methyl ethyl ketone (MEK), 84.2 g of cellulose acetate butyrate (CAB381-20: manufactured by Eastman Chemical) and 4.5 g of polyester resin (VitelPE2200B: manufactured by Boston) were added and dissolved. Next, 0.30 g of infrared dye 1 was added, and 4.5 g of a fluorine-based activator (Surflon KH40: manufactured by Asahi Glass Co., Ltd.) dissolved in 43.2 g of methanol and a fluorine-based activator (Megafag F120K: Dainippon Ink, Inc.) 2.3 g) was added and stirred well until dissolved. Finally, 75 g of silica (Syloid 64X6000: manufactured by WR Grace) dispersed in MEK at a concentration of 1% with a dissolver type homogenizer was added and stirred to prepare a coating solution for the back surface side.

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

<Preparation of photosensitive silver halide emulsion A>
Solution (A1)
Phenylcarbamoylated gelatin 88.3g
Compound AO (10% methanol aqueous solution) 10 ml
Potassium bromide 0.32g
Solution finished to 5429 ml with water (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
Solution (C1)
Potassium bromide 51.55g
Potassium iodide 1.47g
Solution to make up to 660 ml with water (D1)
Potassium bromide 154.9g
4.41 g of potassium iodide
Iridium chloride (1% solution) 0.93ml
Solution to make up to 1982ml with water (E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount solution (F1)
Potassium hydroxide 0.71g
Solution finished to 20 ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
Solution (H1)
Anhydrous sodium carbonate 1.72 g
Finish to 151 ml with water AO: 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 Nos. 58-58288 and 58-58289, ¼ amount of the solution (B1) and the whole amount of the solution (C1) were adjusted to a temperature of 30 ° C. and a pAg of 8.09. While being controlled, the nucleation was performed by adding 4 minutes 45 seconds by the simultaneous mixing method. After 1 minute, the entire amount of solution (F1) was added. During this time, the pAg was adjusted as appropriate using the aqueous solution (E1). After 6 minutes, 3/4 amount of the solution (B1) and the whole amount of the solution (D1) were added over 14 minutes and 15 seconds by a simultaneous mixing method while controlling the temperature at 30 ° C. and pAg 8.09. 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 precipitated. 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 mol of silver to obtain an emulsion. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 0.040 μm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

  Next, 240 ml of sulfur sensitizer S-5 (0.5% methanol solution) was added to the above emulsion, and gold sensitizer Au-5 corresponding to 1/20 mol of this sensitizer was further added to the emulsion. The mixture was stirred for 120 minutes for chemical sensitization. This is designated as photosensitive silver halide emulsion A.

<Preparation of powdered aliphatic carboxylic acid silver salt A>
In 4,720 ml of pure water, 130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved at 80 ° C. Next, 540.2 ml of a 1.5 mol / L sodium hydroxide aqueous solution was added, and 6.9 ml of concentrated nitric acid was added, followed by cooling to 55 ° C. to obtain a fatty acid sodium solution. While maintaining the temperature of the fatty acid sodium solution at 55 ° C., 45.3 g of the photosensitive silver halide emulsion A and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 702.6 ml of a 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an aliphatic carboxylic acid silver salt dispersion. Then, transfer this aliphatic carboxylic acid silver salt dispersion to a water-washing container, add deionized water, stir, and let stand to float and separate the aliphatic carboxylic acid silver salt dispersion to remove the lower water-soluble salts. did. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 50 μS / cm, and centrifugal dehydration was carried out. Then, the cake-like aliphatic carboxylic acid silver salt thus obtained was added to the airflow dryer flash jet. Using a dryer (manufactured by Seishin Enterprise Co., Ltd.), a powdered aliphatic carboxylic acid silver salt A was obtained by drying until the water content became 0.1% under the operating conditions of nitrogen gas atmosphere and dryer inlet hot air temperature. An infrared moisture meter was used to measure the water content of the aliphatic carboxylic acid silver salt composition.

<Preparation of preliminary dispersion A>
14.57 g of polyvinyl butyral resin (B-79: manufactured by Solusia) was dissolved in 1,457 g of MEK, and 500 g of powdered fat was stirred with a dissolver type disperser DISPERMAT CA-40M (manufactured by VMA-GETZMANN). The group A carboxylate silver salt A was gradually added and mixed well to obtain a preliminary dispersion A.

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

<Preparation of stabilizer solution>
A stabilizer solution was prepared by dissolving 1.0 g of Stabilizer 1 and 0.31 g of potassium acetate in 4.97 g of methanol.

<Preparation of infrared sensitizing dye liquid A>
19.2 mg of infrared sensitizing dye 1, 1.488 g of 2-chloro-benzoic acid, 2.7779 g of stabilizer 2 and 365 mg of 5-methyl-2-mercaptobenzimidazole are darkened in 31.3 ml of MEK. The solution was dissolved at a place to prepare an infrared sensitizing dye liquid A.

<Preparation of additive solution a>
Silver ion reducing agent (compound described in Table 1) 1.5 × 10 ⁻² mol, leuco dye of general formula (2) (compound and amount described in Table 1), 1.54 g of 4-methylphthalic acid, 0 .48 g of infrared dye 1 was dissolved in 110 g of MEK to obtain additive solution a.

<Preparation of additive liquid b>
3.56 g of antifoggant 2 and 3.43 g of phthalazine were dissolved in 40.9 g of MEK to obtain additive solution b.

<Preparation of photosensitive layer coating solution A>
In an inert gas atmosphere (97% nitrogen), 50 g of the photosensitive emulsion dispersion A and 15.11 g of MEK were kept at 21 ° C. with stirring, and 390 μl of antifoggant 1 (10% methanol solution) was added. Stir for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 20 minutes. Subsequently, 167 ml of a stabilizer solution was added and stirred for 10 minutes, and then 1.32 g of the infrared sensitizing dye solution A was added and stirred for 1 hour. Thereafter, the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While keeping the temperature at 13 ° C., after adding 13.31 g of polyvinyl butyral resin (B-79: the above) as a binder resin and stirring for 30 minutes, 1.084 g of tetrachlorophthalic acid (9.4% MEK solution) was added. Added and stirred for 15 minutes. While continuing to stir, the additive liquid a (silver ion reducing agent, cyan color developing leuco dye was weighed so as to have the addition amount shown in Table 1), 1.6 ml of Desmodur N3300 (Mobey aliphatic isocyanate) A photosensitive layer coating solution A was obtained by sequentially adding 10% MEK solution and 4.27 g of additive solution b and stirring.

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

<Preparation of surface protective layer coating solution>
While stirring MEK865g, 96 g of cellulose acetate butyrate (CAB171-15: supra), 4.5 g of polymethylmethacrylic acid (Paraloid A-21: manufactured by Rohm & Haas), 1 vinylsulfone compound (VSC) 0.5 g, 1.0 g of benzotriazole, and 1.0 g of a fluorine-based activator (Surflon KH40: supra) were added and dissolved. Next, 30 g of the above matting agent dispersion was added and stirred to obtain a surface protective layer coating solution.

<Preparation of photothermographic material sample>
A photosensitive material sample was prepared by simultaneously applying the photosensitive layer coating solution A and the surface protective layer coating solution on the undercoat layer a using a known extrusion coater. The coating was carried out so that the photosensitive layer had a coating silver amount of 1.5 g / m ² and the surface protective layer had a dry film thickness of 2.5 μm. Then, it dried for 10 minutes using the drying air with a drying temperature of 75 degreeC and dew point temperature of 10 degreeC, and obtained the samples 101-120.

  The chemical structure of the compound used in Example 1 is shown below.

VSC: (CH ₂ = CHSO ₂ CH ₂ ) ₂ CHOH

<Exposure and development processing>
From the emulsion surface side of each sample prepared as described above, exposure by laser scanning was given by an exposure machine using a semiconductor laser that was converted into a longitudinal multimode with wavelengths of 810 nm and 814 nm by high frequency superposition as an exposure source. At this time, an image was formed by setting the angle of the exposure surface of the sample and the exposure laser beam to 75 degrees. As a result, an image with less unevenness and unexpectedly good sharpness or the like was obtained compared to the case where the angle was 90 degrees.

  Thereafter, using an automatic developing machine having a heat drum, the sample was subjected to a heat development treatment at 123 ° C. for 13.5 seconds so that the protective layer of the sample was in contact with the drum surface. At that time, exposure and development were performed in a room adjusted to 23 ° C. and 50% RH (relative humidity).

<Performance evaluation>
The following evaluations were performed on the images obtained as described above.

<Sensitivity, fog, and maximum density>
For each image, density measurement is performed with a Macbeth densitometer (TD-904), and a characteristic curve is created with the horizontal axis: exposure amount and vertical axis: image density, giving a density 1.0 higher than the unexposed area. The reciprocal of the ratio of the exposure amount required for the above was defined as sensitivity, and the minimum density (fogging) and the maximum density were measured. The sensitivity was expressed as a relative value with the sensitivity of the sample 101 as 100.

《Color tone》
The color tone of each image was observed and evaluated according to the following criteria. Practically, it is preferably rank 4 or higher.

5: Cold black tone does not feel red at all 4: 4: Black tone is not red, but almost no redness is felt 3: Partial redness is slightly felt 2: The entire surface is slightly reddish 1: Red at first glance <Image preservation>
For each image, the image density change rate of the minimum density portion and the maximum density portion was measured according to the following method to evaluate the image storage stability.

<Image storability of minimum density area>
Each of the heat-developed samples prepared in the same manner as the above sensitivity, fog, and maximum density measurement methods was subjected to a commercially available white fluorescent lamp with an illuminance of 500 lux on the sample surface in an environment of 45 ° C. and 55% RH. And then irradiated continuously for 3 days. Measure the minimum density (D ₂ ) of the sample irradiated with the fluorescent lamp and the minimum density (D ₁ ) of the sample not irradiated with the fluorescent lamp, and calculate the minimum density change rate (%) from the following formula. It was used as a measure of image preservation. The closer the value is to 100, the better.

Minimum density change rate = D ₂ / D ₁ × 100 (%)
<< Image preservation at the highest density area >>
Each heat-developed sample prepared by the same method as the measurement of the minimum density change rate is allowed to stand in an environment of 25 ° C. and 45 ° C. for 3 days, and then the maximum density is measured. The density change rate (%) was measured, and this was used as a measure of image storage stability at the highest density part. The closer the value is to 100, the better.

Image density change rate = maximum density after storage at 45 ° C./maximum density after storage at 25 ° C. × 100 (%)
The results are also shown in Table 1.

  From Table 1, the photothermographic material of the present invention has not only good color tone but also good sensitivity, maximum density and fog, and oscillation wavelength when exposed using a laser scanning exposure machine. It can be seen that the sensitivity and the maximum density of the output image are extremely stable with respect to fluctuations in the output.

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 having 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. After that, after slitting the chuck portion of the tenter, knurl processing was performed on both ends, and the roll was wound at 39.2 × 10 ⁴ Pa (4 kg / cm ² ) to obtain a roll having a thickness of 175 μm.

<Surface corona treatment>
Using a pisolid state corona treatment machine (manufactured by Pillar: 6KVA model), 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 processing frequency at this time is 9.6 kHz, and the gap clearance between the electrode and the dielectric roll is 1.6 mm.

<Preparation of undercoat support>
First, each coating solution of the photosensitive layer side undercoat layer, the back surface side first layer, and the back surface side second layer having the following composition was prepared.

On one side (photosensitive layer surface) of the PET support subjected to the corona discharge treatment, the photosensitive layer side undercoat layer coating solution is applied with a wire bar so that the wet coating amount is 6.6 ml / m ² (per one side). And dried at 180 ° C. for 5 minutes. Next, the first layer coating solution is applied to the back surface (back surface) with a wire bar so that the wet coating amount is 5.7 ml / m ² and dried at 180 ° C. for 5 minutes. The layer coating solution was applied with a wire bar so that the wet coating amount was 7.7 ml / m ² and dried at 180 ° C. for 6 minutes to prepare an undercoat support.
(Photosensitive layer side undercoat layer coating solution)
Pesresin A-515GB: 234 g manufactured by Takamatsu Yushi Co., Ltd. (30% solution)
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number 8.
5) 21.5 g of 10% solution
Polymer fine particles (MP-1000: manufactured by Soken Chemical Co., Ltd., average particle size 0.4 μm) 0.91 g
744 ml of distilled water
(Back surface side first layer coating solution)
Styrene / butadiene (68/32% ratio) copolymer latex (solid content 40%)
158g
2,4-Dichloro-6-hydroxy-s-triazine sodium salt (8% aqueous solution)
20g
Sodium laurylbenzenesulfonate (1% aqueous solution) 10ml
854 ml of distilled water
(Back surface side second layer coating solution)
84 g of SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17% dispersion)
Gelatin (10% aqueous solution) 89.2g
Metrose TC-5 (manufactured by Shin-Etsu Chemical Co., Ltd.) 2% aqueous solution 8.6g
Polymer fine particles (MP-1000: manufactured by Soken Chemical Co., Ltd.) 0.01 g
Sodium dodecylbenzenesulfonate (1% aqueous solution) 10ml
Sodium hydroxide (1% aqueous solution) 6ml
Proxel (ICI) 1ml
805 ml of distilled water
<Preparation of back surface coating solution>
<Preparation of Base Precursor Solid Fine Particle Dispersion (a)>
64 g of base precursor (compound 11), 28 g of diphenylsulfone and 10 g of surfactant demole N (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 Corporation). The beads were dispersed to obtain a base precursor solid fine particle dispersion (a) 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 beads using a sand mill (1/4 Gallon sand grinder mill: supra). 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, base precursor solid fine particle dispersion (a) 70 g, dye solid fine particle dispersion 56 g, monodisperse polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4) 1 0.5 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. Got.

<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 (vinylsulfoneacetamide), 1 g of sodium t-octylphenoxyethoxyethanesulfonate, 30 mg of benzoisothiazolinone , 37 mg of fluorine surfactant (F-1), 0.15 g of fluorine surfactant (F-2), 64 mg of fluorine surfactant (F-3), 32 mg of fluorine surfactant (F-4) 8.8 g of acrylic acid / ethyl acrylate copolymer (copolymerization mass ratio 5/95), 0.6 g of aerosol OT (manufactured by American Cyanamide), 1.8 g of liquid paraffin emulsion as liquid paraffin, and 950 ml of water It mixed and it was set as the back surface protective layer coating liquid.

<Preparation of silver halide emulsion 1>
A solution obtained by adding 3.1 ml of 1% potassium bromide solution to 1421 ml of distilled water, and further adding 3.5 ml of 0.5 mol / L sulfuric acid and 31.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. The solution temperature was maintained at ℃, and distilled water was diluted to 95.4 ml by adding distilled water to 22.22 g of silver nitrate, and 15.3 g of potassium bromide and 0.8 g of potassium iodide were diluted to 97.4 ml with distilled water. Solution B was added at a constant flow rate over 45 seconds. Thereafter, 10 ml of a 3.5% aqueous hydrogen peroxide solution was added, and 10.8 ml of a 10% aqueous solution of benzimidazole was further added. Further, a solution C in which distilled water was added to 51.86 g of silver nitrate and diluted to 317.5 ml, and a solution D in which 44.2 g of potassium bromide and 2.2 g of potassium iodide were diluted to 400 ml with distilled water were used as solution C. Was added at a constant flow rate over 20 minutes, and solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridate (III) was added 10 minutes after the start of the addition of Solution C and Solution D 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, a potassium iron (II) hexacyanide aqueous solution was added in a total 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.

The silver halide dispersion is maintained at 38 ° C. with stirring, 5 ml of 0.34% 1,2-benzisothiazolin-3-one in methanol is added, and after 40 minutes, spectral sensitizing dye A and spectral sensitization are added. A methanol solution of Dye B (1: 1 in molar ratio) as a total of spectral sensitizing dye per mol of silver was added at 1.2 × 10 ⁻³ mol, 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 moles per mole 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% methanol solution of N, N'-dihydroxy-N "-diethylmelamine was added, and after another 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the methanol solution at a rate of 4.8 per mole of silver. Silver halide emulsion 1 was prepared by adding 5.4 × 10 ⁻³ mole of × 10 ⁻³ mole and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole per mole of silver in a methanol solution. The grains in the prepared silver halide emulsion were silver iodobromide grains having an average sphere equivalent diameter of 0.042 .mu.m and a sphere equivalent diameter variation coefficient of 20% uniformly containing 3.5 mol% of iodine. The particle size, etc. was determined from the average of 1,000 particles using an electron microscope, and the {100} face ratio of the particles was 80% using the Kubelka-Munk method.

<Preparation of silver halide emulsion 2>
In the preparation of silver halide emulsion 1, the liquid temperature 30 ° C. during grain formation was changed to 47 ° C., and solution B was changed to diluting 15.9 g of potassium bromide to 97.4 ml with distilled water. D was changed to diluting 45.8 g of potassium bromide with distilled water to 400 ml, and the addition time of solution C was changed to 30 minutes to remove potassium hexacyanoiron (II) in the same manner. Silver chloride emulsion 2 was prepared. Precipitation / desalting / washing / dispersion was carried out in the same manner as silver halide emulsion 1. Furthermore, the addition amount of the methanol solution of 1: 1 in the molar ratio of the spectral sensitizing dye A and the spectral sensitizing dye B is 7.5 × 10 ⁻⁴ mol as the total of the sensitizing dye A and the sensitizing dye B per mol of silver. The amount of tellurium sensitizer C added was 1.1 × 10 ⁻⁴ mol per mol of silver, and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole was added 3 mol / mol of silver. Spectral sensitization, chemical sensitization, 5-methyl-2-mercaptobenzimidazole, and 1-phenyl-2-heptyl-5-mercapto in the same manner as silver halide emulsion 1 except that the amount was changed to 3 × 10 ⁻³ mol. -1,3,4-Triazole was added to obtain a silver halide emulsion 2. The emulsion grains of the silver halide emulsion 2 were pure silver bromide cubic grains having an average sphere equivalent diameter of 0.080 μm and a sphere equivalent diameter variation coefficient of 20%.

<Preparation of silver halide emulsion 3>
In the preparation of silver halide emulsion 1, silver halide emulsion 3 was prepared in the same manner except that the liquid temperature at the time of grain formation was changed from 30 ° C. to 27 ° C. Further, precipitation / desalting / water washing / dispersion was carried out in the same manner as silver halide emulsion 1. The molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is 1: 1 as a solid dispersion (gelatin aqueous solution), and the addition amount is 6 × 10 ⁻ as the total of sensitizing dye A and sensitizing dye B per mole of silver. ^A silver halide emulsion 3 was obtained in the same manner as the silver halide emulsion 1 except that ³ mol and the addition amount of the tellurium sensitizer C was changed to 5.2 × 10 ⁻⁴ mol per mol of silver. The emulsion grains of the silver halide emulsion 3 were silver iodobromide grains containing 3.5 mol% of iodine with an average equivalent sphere diameter of 0.034 μm and a sphere equivalent diameter variation coefficient of 20%.

<Preparation of mixed emulsion A for coating solution>
70% of silver halide emulsion 1, 15% of silver halide emulsion 2 and 15% of silver halide emulsion 3 are dissolved, and benzothiazolium iodide is dissolved in a 1% aqueous solution at 7 × 10 ⁻³ per mol of silver. Mole was added. Further, water was added so that the silver halide content per kg of the mixed emulsion for coating solution was 38.2 g in terms of silver.

<Preparation of fatty acid silver dispersion>
Behenic acid (Edenor C22-85R: manufactured by Henkel) 87.6 kg, distilled water 423 L, 5 mol / L sodium hydroxide aqueous solution 49.2 L, t-butanol 120 L were mixed and stirred at 75 ° C. for 1 hour. 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 t-butanol was kept at 30 ° C., and with sufficient stirring, the total amount of the previous sodium behenate solution and the total amount of the aqueous silver nitrate solution were 93 minutes and 15 seconds, respectively, at a constant flow rate. 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. Further, 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 to a height that did not 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 filtered off 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 silver behenate particles was evaluated by electron micrographs, the average values were a = 0.14 μm, b = 0.4 μm, c = 0.6 μm, average aspect ratio 5.2, average sphere equivalent diameter 0.52 μm. It was a scaly crystal with a coefficient of variation of 15% of the equivalent sphere diameter. The coefficients a, b, and c are a, b, and c from the shortest side of the rectangular parallelepiped when the shape of the organic acid silver salt particle is approximated to a rectangular parallelepiped.

  19.3 kg of polyvinyl alcohol (Kuraray Co., Ltd .: PVA-217) and water are added to the wet cake corresponding to a dry solid content of 260 kg, and the whole amount is made 1,000 kg, and then slurried with a dissolver blade, and then a pipeline mixer ( Pre-dispersed by Mizuho Kogyo Co., Ltd .: PM-10 type). Next, the pre-dispersed undiluted solution was treated three times by adjusting the pressure of the disperser (Microfluidizer M-610: manufactured by Microfluidics International Corporation, using Z-type interaction chamber) to 123.6 MPa, A silver behenate dispersion was obtained. 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 dispersion>
16 kg of water was added to 10 kg of a 20% aqueous solution of 26.0 mol of a silver ion reducing agent (compound described in Table 2) and modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd .: Poval MP203) and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal bead mill (Immex: UVM-2) 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% to obtain a reducing agent dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.42 μm and a maximum particle diameter of 2.0 μm or less. The obtained reducing agent 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 leuco dye dispersion>
75 g of water is added to 150 g of a 10% aqueous solution of a leuco dye represented by the general formula (2) (compounds and amounts shown in Table 2) and modified polyvinyl alcohol (Poval MP-203: supra) and mixed well. To give a slurry. This slurry was dispersed with a 0.5 mm zirconia bead and a sand mill (1/4 Gallon sand grinder mill: manufactured by Imex) for 10 hours at 1,500 rpm, and a solid fine particle dispersion having a median diameter of 0.4 μm. Got. This dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign matters such as dust and stored.

<Preparation of Development Accelerator-1 Dispersion>
75 g of water was added to 75 g of development accelerator-1 and 150 g of a 10% aqueous solution of modified polyvinyl alcohol (Poval MP-203: supra) and mixed well to obtain a slurry. This slurry was dispersed using a 0.5 mm zirconia bead and a sand mill (1/4 Gallon sand grinder mill: the above) for 10 hours at a rotation speed of 1,500 rpm to obtain a solid fine particle dispersion having a median diameter of 0.35 μm. Obtained. The obtained 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 hydrogen bonding compound-2 dispersion>
10 kg of water is added to 10 kg of 10% aqueous solution of hydrogen bonding compound-2 (tri (4-t-butylphenyl) phosphine oxide) and denatured polyvinyl alcohol (Poval MP203: supra), and mixed well to prepare a slurry. It was. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal bead mill (Immex: UVM-2) 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 hydrogen bonding compound concentration of 22% to obtain a hydrogen bonding compound-2 dispersion. The hydrogen bonding compound-2 contained in this dispersion had a median diameter of 0.35 μm and a maximum particle diameter of 1.5 μm or less. The obtained 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-1 dispersion>
10 kg of organic polyhalogen compound-1 (2-tribromomethanesulfonylnaphthalene) and 10 kg of 20% aqueous solution of modified polyvinyl alcohol (Poval MP203: supra), and 0.4 kg of 20% aqueous solution of sodium tri-i-propylnaphthalenesulfonate Then, 16 kg of water was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump, dispersed in a horizontal bead mill (UVM-2: supra) filled with zirconia beads having an average diameter of 0.5 mm for 5 hours, 0.2 g of benzoisothiazolinone sodium salt and water Was added so that the concentration of the organic polyhalogen compound was 23.5% to obtain an organic polyhalogen compound-1 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 2.0 μm or less. This dispersion was filtered through a polypropylene filter having a pore diameter of 10.0 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% aqueous solution of modified polyvinyl alcohol (Poval MP203: supra), 0.4 kg of 20% aqueous solution of sodium tri-i-propylnaphthalenesulfonate, 14 kg of water was added and mixed well to make a slurry. This slurry was fed with a diaphragm pump, dispersed in a horizontal bead mill (UVM-2: supra) filled with zirconia beads having an average diameter of 0.5 mm for 5 hours, 0.2 g of benzoisothiazolinone sodium salt and water Was added so that the concentration of the organic polyhalogen compound was 26% to obtain an organic polyhalogen compound-2 dispersion. The organic polyhalogen compound particles contained in this polyhalogen compound dispersion had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less. The 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 Phthalazine Compound-1 Solution>
8 kg of modified polyvinyl alcohol (MP203: supra) was dissolved in 174.57 kg of water, then 3.15 kg of a 20% aqueous solution of sodium tri-i-propylnaphthalenesulfonate and phthalazine compound-1 (6-i-propylphthalazine) ) Was added to obtain a 5% 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% aqueous solution.

<Preparation of pigment-1 dispersion>
To 64 g of pigment-1 (CI Pigment Blue 60) and demole N manufactured by Kao Corporation was added to 6.4 g, 250 g of water was added and mixed well to obtain a slurry. 800 g of zirconia beads having an average diameter of 0.5 mm were prepared, put into a vessel together with the slurry, and dispersed for 25 hours with a disperser (1/4 G sand grinder mill: supra) to obtain a pigment-1 dispersion. The pigment particles contained in this pigment dispersion had an average particle size of 0.21 μm.

<Preparation of SBR latex solution>
An SBR latex with Tg = 23 ° C. was prepared as follows. Using ammonium persulfate as a polymerization initiator and an anionic surfactant as an emulsifier, 70.5 parts of styrene, 26.5 parts of butadiene and 3 parts of acrylic acid were emulsion-polymerized, and then aging was performed at 80 ° C. for 8 hours. Thereafter, the mixture was cooled to 40 ° C., adjusted to pH 7.0 with aqueous ammonia, and Sandet BL manufactured by Sanyo Kasei Co., Ltd. was added to a concentration of 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 ⁺ to NH ₄ ⁺ used at this time was 1: 2.3. Further, 0.15 ml of a 7% aqueous solution of benzoisothiazolinone sodium salt was added to 1 kg of this liquid to prepare an SBR latex liquid.

Properties of SBR Latex: Styrene / Butadiene / Acrylic Acid (70.5 / 26.5 / 3) Latex Tg 23 ° C., Average Particle Size 0.1 μm, Concentration 43%, Equilibrium Water Content 0.6% at 25 ° C./RH 60% , Ion conductivity 4.2 mS / cm (conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd., latex stock solution (43%) measured at 25 ° C.), pH 8.4
SBR latexes having different Tg were prepared in the same manner as described above by appropriately changing the ratio of styrene and butadiene.

<Preparation of emulsion layer (photosensitive layer) coating solution>
1,000 g of the fatty acid silver dispersion obtained above, 125 ml of water, 204 g of reducing agent dispersion, cyan chromogenic leuco dye dispersion (type and amount are listed in Table 2), 27 g of pigment-1 dispersion, organic polyhalogen compound -1 dispersion 82g, organic polyhalogen compound-2 dispersion 40g, phthalazine compound-1 solution 173g, SBR latex (Tg: 20.5 ° C) solution 1,082g, mercapto compound-1 aqueous solution 9g were added in order. Immediately before, 158 g of silver halide mixed emulsion A was added, and the well-mixed emulsion layer coating solution was directly fed to the coating die for coating. The viscosity of the emulsion layer coating solution was 40 mPa · s at 40 ° C. (No. 1 rotor, 60 rpm) as measured with a B-type viscometer of Tokyo Keiki. Rheometrics Far East, Inc .: The viscosity of the coating solution at 25 ° C. using an RFS fluid spectrometer is 1,500 at shear rates of 0.1, 1, 10, 100, and 1000 [1 / second], respectively. 220, 70, 40, 20 [mPa · s].

<Preparation of emulsion surface intermediate layer coating solution>
772 g of 10% aqueous solution of polyvinyl alcohol (PVA-205: manufactured by Kuraray Co., Ltd.), 5.3 g of 20% dispersion of pigment, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (64/9/20 / 5/2% ratio) 226 g of latex 27.5% solution, 2 ml of 5% aqueous solution of aerosol OT (supra), 10.5 ml of 20% aqueous solution of diammonium phthalate, and a total mass of 880 g Then, water was added so that the pH was adjusted to 7.5 with sodium hydroxide to obtain an intermediate layer coating solution, which was fed to the coating die so as to be 10 ml / m ² . The viscosity of the coating solution was 21 mPa · s at a B-type viscometer at 40 ° C. (No. 1 rotor, 60 rpm).

<Preparation of emulsion 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 (64/9/20/5/2% ratio) latex 27.5 (supra)% solution 80 g 23 ml of 10% methanol solution of phthalic acid, 23 ml of 10% aqueous solution of 4-methylphthalic acid, 28 ml of 0.5 mol / L sulfuric acid, 5 ml of 5% aqueous solution of aerosol OT (supra), 0.5 g of phenoxyethanol, 0.1 g of benzoisothiazolinone was added, water was added to a total mass of 750 g to prepare a coating solution, and 26 ml of a 4% aqueous solution of chrome alum was mixed with a static mixer immediately before coating, 18.6 ml / m ^The solution was fed to the coating die so as to be ² . The viscosity of the coating solution was 17 mPa · s at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

<Preparation of photothermographic material sample>
On the back surface side of the undercoat support, the antihalation layer coating solution is applied so that the solid content coating amount of the solid fine particle dye is 0.04 g / m ^2, and the back surface protective layer coating solution is applied with a gelatin coating amount of 1 The back layer was produced by applying and drying the multilayer simultaneously so as to be 0.7 g / m ² . On the surface opposite to the back surface, the emulsion layer, the intermediate layer, the protective layer first layer, and the protective layer second layer were coated simultaneously in the order of the emulsion layer, the intermediate layer, the protective layer, and the second layer by the slide bead coating method. . At this time, the emulsion layer and the intermediate layer were adjusted to 31 ° C., the protective layer first layer was adjusted to 36 ° C., and the protective layer second layer was adjusted to 37 ° C. The coating amount (g / m ² ) of each compound in the emulsion layer is as follows.

Silver behenate 6.19
Reducing agent Type and amount are listed in Table 2. Dye of general formula (2) Type and amount are listed in Table 2. Pigment (CI Pigment Blue 60) 0.032
Organic polyhalogen compound-1 (supra) 0.46
Organic polyhalogen compound-2 (supra) 0.25
Phthalazine compound-1 (supra) 0.21
SBR latex (supra) 11.1
Mercapto compound-1 (supra) 0.002
Silver halide (as Ag) 0.145
The coating / 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 be 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 liquid with wind at a dry bulb temperature of 10 to 20 ° C., the coating solution is transported in a non-contact manner, and in a string-wound non-contact dryer, the dry bulb temperature is 23 to 45 ° C. It dried with the dry wind of the wet bulb temperature 15-21 degreeC. After drying, the humidity was adjusted to 40 to 60% RH (relative humidity) at 25 ° C., and then the film surface was heated to 70 to 90 ° C. After heating, the film surface was cooled to 25 ° C.

  The resulting photothermographic material had a matte degree of Beck smoothness of 550 seconds on the photosensitive layer surface side and 130 seconds on the back surface. The pH of the film surface on the photosensitive layer side was measured and found to be 6.0.

  The chemical structure of the compound used in Example 2 is shown below.

_{F-1: C 8 F 17} SO 2 N (C 3 H 7) CH 2 COOK
_{F-2: C 8 F 17} SO 2 N (C 3 H 7) (CH 2 CH 2 O) n H n = 16 ( average)
_{F-3: C 8 F 17} SO 2 N (C 3 H 7) (CH 2 CH 2 O) 5 (CH 2) 4 SO 3 Na
F-4: C ₈ F ₁₇ SO ₃ K

<Exposure and development processing>
The photographic material was exposed with a Fuji Medical Dry Laser Imager FM-DPL L (equipped with a 660 nm semiconductor laser with a maximum output of 60 mW (IIIB)). After exposure, the FM-DPL thermal development unit is remodeled and thermally developed (total of 24 seconds with 4 panel heaters set at 112 ° C-119 ° C-121 ° C-121 ° C = standard development time is 24 seconds) did.

<Performance evaluation>
The following evaluations were performed on the images obtained as described above.

<Sensitivity, fog, and maximum density>
For each image, density measurement is performed with a Macbeth densitometer (TD-904) to create a characteristic curve consisting of horizontal axis = exposure amount and vertical axis = image density, giving a density 1.0 higher than the unexposed portion. The reciprocal of the ratio of the exposure amount required for the above was defined as sensitivity, and the minimum density (fogging) and the maximum density were measured. The sensitivity is expressed as a relative value where the sensitivity of the sample 201 is 100.

《Color tone》
The color tone of each image was observed and evaluated according to the following criteria. Practically, it is preferably rank 4 or higher.

5: Cold black tone does not feel red at all 4: 4: Black tone is not red, but almost no redness is felt 3: Partial redness is slightly felt 2: The entire surface is slightly reddish 1: Red at first glance <Image preservation>
For each of the obtained images, the image density change rate of the minimum density portion and the maximum density portion was measured in the same manner as in Example 1 to evaluate the image storage stability.

<Image storability of minimum density area>
Each of the heat-developed samples prepared in the same manner as the above sensitivity, fog, and maximum density measurement methods was subjected to a commercially available white fluorescent lamp with an illuminance of 500 lux on the sample surface in an environment of 45 ° C. and 55% RH. And then irradiated continuously for 3 days. Measure the minimum density (D ₂ ) of the sample irradiated with the fluorescent lamp and the minimum density (D ₁ ) of the sample not irradiated with the fluorescent lamp, and calculate the minimum density change rate (%) from the following formula. It was used as a measure of image preservation. The closer the value is to 100, the better.

Minimum density change rate = D ₂ / D ₁ × 100 (%)
<< Image preservation at the highest density area >>
Each heat-developed sample prepared by the same method as the measurement of the minimum density change rate is allowed to stand in an environment of 25 ° C. and 45 ° C. for 3 days, and then the maximum density is measured. The density change rate (%) was measured, and this was used as a measure of image storage stability at the highest density part. The closer the value is to 100, the better.

Image density change rate = maximum density after storage at 45 ° C./maximum density after storage at 25 ° C. × 100 (%)
The results are also shown in Table 2.

  From the results of Table 2, it can be seen that the sample according to the present invention has higher sensitivity, lower fog, and better color tone than the comparative sample. Further, it can be seen that the image storability is much better than the comparative example.

Claims (8)

In a photothermographic material having an image forming layer containing a non-photosensitive organic silver salt, silver halide, silver ion reducing agent and binder on a support, at least one silver ion reducing agent is represented by the general formula (1 And a photothermographic material comprising a compound represented by the following general formula (2):

[Wherein, R ₁ and R ₂ each represent a hydrogen atom, an aliphatic group or an aromatic group. R ₃ and R ₄ each represent a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Q represents a substitutable group on the benzene ring, and n represents an integer of 0 to 2. When there are a plurality of Q, each Q may be the same or different. ]

[Wherein Y ₁ and Y ₂ each represent —O—, —S—, —N (R ₁₃ ) — or —C (R ₁₄ ) (R ₁₅ ) —, and each of R ₁₃ , R ₁₄ and R ₁₅ Each represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. R ₁₁ and R ₁₂ each represent a hydrogen atom or a substituent. X ₁ and X ₂ each represents a group that can be substituted on the benzene ring. m1 and m2 each represent an integer of 0-4. When m1 and m2 are 2 or more, X ₁ and X ₂ may be the same or different, and may be connected to each other to form a ring. ] 2. The photothermographic material according to claim 1, wherein Y ₁ and Y ₂ in the general formula (2) are —S—. 3. The photothermographic material according to claim 1, wherein R ₃ in the general formula (1) is a secondary or tertiary alkyl group. 4. The photothermographic material according to claim 1, wherein R ₄ in the general formula (1) is an alkyl group having 2 or more carbon atoms. The addition amount ratio (molar ratio) of the compound represented by the general formula (2) and the compound represented by the general formula (1) is 0.001 to 0.15. The photothermographic material according to claim 1. 6. The photothermographic material according to claim 5, wherein the molar ratio is 0.005 to 0.1. 7. The photothermographic material according to claim 1, wherein the silver halide contains 5 to 100 mol% of silver iodide. 8. The photothermographic material according to claim 1, wherein the non-photosensitive organic silver salt contains 70% by mass or more and less than 100% by mass of silver behenate.