JP2005128289A - Heat developable photosensitive material and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material having high density, excellent in silver tone, excellent in image preservability under photoirradiation and in prevention of fogging increase with time, and excellent in density unevenness in heat development, and an image forming method, and to optionally provide a heat developable photosensitive material excellent further in image preservability in storage at high temperature or excellent in conveyability and environmental suitability of the heat developable photosensitive material (film), and an image forming method. <P>SOLUTION: In the heat developable photosensitive material having an image forming layer containing at least an organic silver salt, a silver halide, a binder and a reducing agent on one surface of a support, a compound represented by formula (1) is contained as the reducing agent, a compound represented by a general formula (L) is also contained, and the molar ratio between the compound represented by the general formula (L) and the compound represented by the general formula (1), [the compound of the general formula (L) (mol)]/[the compound of the general formula (1) (mol)] is 0.001-0.2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, and an image forming method.

  Conventionally, in the fields of medical treatment and printing plate making, waste liquid from wet processing of image forming materials has been a problem in terms of workability. In recent years, reduction of waste processing liquid has been strongly desired from the viewpoint of environmental conservation and space saving. ing. Therefore, photothermographic materials capable of forming an image only by applying heat have been put into practical use and are rapidly spreading in the above fields.

  A photothermographic material (hereinafter also simply referred to as a photothermographic material or a photosensitive material) has been proposed for a long time. For example, US Pat. Nos. 3,152,904 and 3,457,075 It is described in.

  This heat-developable material is usually processed by a heat-development processing apparatus called a heat-development processor that applies stable heat to the heat-developable material to form an image. As described above, with the rapid spread in recent years, a large amount of this heat development processing apparatus has been supplied to the market. However, depending on the temperature and humidity conditions during the heat development processing, the slipping property between the photosensitive material and the transport roller or processing member of the heat development processing apparatus changes, resulting in the problem of poor transport and uneven density. It was. There is also a problem that the density of the photothermographic material varies with time. It has been found that these phenomena occur remarkably in a photothermographic material that forms an image by thermal development after image exposure with a laser beam. In recent years, there has been a demand for a compact laser imager and rapid processing.

  For this purpose, it is essential to improve the characteristics of the photothermographic material. In order to obtain a sufficient density of the photothermographic material even if rapid processing is performed, a silver halide having a small average grain size as disclosed in JP-A-11-295844 and JP-A-11-352627 The covering power is increased by increasing the number of color development points using, a highly active reducing agent having a secondary or tertiary alkyl group as disclosed in JP 2001-209145 A, a hydrazine compound or a vinyl compound. It is effective to use a development accelerator such as

Further, as a technique for adjusting the silver tone, Japanese Patent Laid-Open No. 8-510563 (Patent Document 1), Japanese Patent Application Laid-Open No. 11-231460 (Patent Document 2), Japanese Patent Application Laid-Open No. 2002-169249 (Patent Document 3), and Japanese Patent Application Laid-Open No. 2002-2002 No. 236334 (Patent Document 4) is disclosed.
Japanese Patent Publication No. 8-510563 (claims) JP-A-11-231460 (Claims) JP 2002-169249 A (Claims) JP 2002-236334 A (Claims)

  However, if the above-mentioned conventional technology is used for speeding up the processing, filament-shaped developed silver is likely to be generated on the surface of the silver halide, the fog rises over time, and the light irradiation image storage stability (printout) (Characteristics) deteriorated, and the silver tone is greatly different from that of a conventional wet X-ray film (yellowish). Further, when a silver halide having a small average grain size is used, a new problem that the color tone becomes reddish at a high density portion having a density of 2.0 or more has occurred. In addition, when the processing is speeded up, the problem that density unevenness occurs at the time of heat development has also been clarified.

  The present invention has been made in view of the above problems, and the object of the present invention is high density, excellent silver tone, light irradiation image storage stability, excellent prevention of fogging over time, and heat development. It is an object of the present invention to provide a photothermographic material and an image forming method excellent in density unevenness. It is another object of the present invention to provide a photothermographic material and an image forming method which are excellent in image storability during high temperature storage, or are excellent in the transportability and environmental suitability of the photothermographic material (film).

  In the present invention, the silver tone, fog increase with time, heat, which is a problem when trying to increase the image density by using fine silver halide, a highly active developer or a development accelerator, particularly during rapid development, As a result of repeated studies to improve the occurrence of density unevenness during development, a compound represented by the general formula (1) (reducing agent) and a compound represented by the general formula (2) were used. It was found that the above object was achieved by setting the molar ratio of the compound represented by formula (1) and the compound represented by the general formula (1) (reducing agent) to 0.001 to 0.2, and the present invention was achieved. .

The above object of the present invention can be achieved by the following constitution.
(Claim 1)
In a photothermographic material having an image forming layer containing at least an organic silver salt, a silver halide, a binder and a reducing agent on one side of the support, a compound represented by the following general formula (1) as the reducing agent And a compound represented by the following general formula (L), a molar ratio of the compound represented by the general formula (L) and the compound represented by the general formula (1) [general formula (L) The compound (mol)] / [the compound (mol) of the general formula (1)] is 0.001 to 0.2.

[Wherein, X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₂ represents an alkyl group and may be the same or different. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2. ]

[Wherein, X represents S, O, or N—R (R represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group); Y represents a —CONH—R ₇ group, —CO—R; ₇ group, -CO-O-R ₇ group or -SO ₂ -R ₇ group (R ₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ each independently represent a hydrogen atom or a group capable of substituting for a benzene ring. W and Z are each independently a hydrogen atom, halogen atom, alkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, alkoxy group, alkylthio group, acyl group, acyloxy group, hydroxyl group, mercapto group, or —NR _{8 represents an} R ₉ group (R ₈ and R ₉ each independently represents a hydrogen atom, an alkyl group, an aryl group or an acyl group). ]
(Claim 2)
2. The photothermographic material according to claim 1, wherein the silver halide contains silver halide grains having an average grain size of 10 to 50 nm.
(Claim 3)
3. The photothermographic material according to claim 1, further comprising silver halide grains having an average grain size of 55 to 100 nm as the silver halide.
(Claim 4)
4. The photothermographic material according to claim 1, wherein the silver halide grains contain silver halide grains chemically sensitized with a compound containing a chalcogen atom as the silver halide.
(Claim 5)
The photothermographic material according to claim 1, wherein the amount of silver contained in the image forming layer is 0.3 to 1.5 g / m ² .
(Claim 6)
The average particle size of the largest average particle size of the matting agent contained in the image forming layer side across the support is Le (μm), and is contained in the layer opposite to the image forming layer across the support. 6. Any one of claims 1 to 5, wherein Lb / Le is 2.0 or more and 10.0 or less when the average particle size of the matting agent having the largest average particle size is Lb (μm). 2. The photothermographic material according to item 1.
(Claim 7)
When the ten-point average roughness of the outermost surface on the image forming layer side is Rz (E) and the ten-point average roughness of the outermost surface on the opposite side of the image forming layer across the support is Rz (B), 6. The photothermographic material according to claim 1, wherein the value of Rz (E) / Rz (B) is 0.1 or more and 0.7 or less.
(Claim 8)
The Ra (E) is 40 nm or more and 150 nm or less, when Ra (E) is the center line average roughness of the outermost surface on the image forming layer side with the support interposed therebetween. The photothermographic material according to claim 1.
(Claim 9)
An image forming method, wherein the photothermographic material according to any one of claims 1 to 8 is thermally developed at a conveying speed of a heat developing portion of 20 to 200 mm / sec using a heat development processing apparatus. .

  According to the present invention, there are provided a photothermographic material and an image forming method having a high density, an excellent silver tone, a light-irradiated image preservability, an excellent antifogging effect over time, and an excellent density unevenness during thermal development. I can. Further, if necessary, it is possible to provide a photothermographic material and an image forming method that are excellent in image storability during high temperature storage, or excellent in the transportability and environmental suitability of the photothermographic material (film).

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

  In the invention according to claim 2 of the present invention, the average grain size of the silver halide is preferably 10 to 40 nm, more preferably 10 to 35 nm. If the average grain size of the silver halide is smaller than 10 nm, the image density may be lowered, or the light irradiation image storage stability may be deteriorated. On the other hand, if it exceeds 50 nm, the image density may decrease.

  The average 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 addition, when it is not a normal crystal, for example, in the case of spherical particles, rod-like particles, etc., the diameter when considering a sphere equivalent to the volume of silver halide grains is calculated as the grain size. The measurement was performed using an electron microscope, and the average particle size was determined by averaging the measured values of 300 particle sizes.

  In the invention according to claim 3 of the present invention, the image density is improved by using together silver halide grains having an average grain size of 55 to 100 nm and silver halide grains having an average grain size of 10 to 50 nm. And the degree of freedom in gradation design can be increased. The ratio (mass ratio) of silver halide grains having an average grain size of 10 to 50 nm and silver halide grains having an average grain size of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90. : 10-60: 40.

  By adopting the configuration of the invention according to claim 6 of the present invention, density unevenness during rapid thermal development processing can be further improved.

  By adopting the configuration of the invention according to claim 7 of the present invention, density unevenness during rapid thermal development processing can be further improved.

  By adopting the configuration of the invention according to claim 8 of the present invention, density unevenness during rapid thermal development processing can be further improved.

  Ra (E) is preferably 50 nm or more and 140 nm or less, and more preferably 60 nm or more and 130 nm or less.

  Hereinafter, the constituent elements of the present invention will be sequentially described.

(Reducing agent)
In the present invention, as the reducing agent (silver ion reducing agent), in particular, at least one of the reducing agents is a compound represented by the general formula (1) alone or in combination with a reducing agent having another different chemical structure. Use.

In the general formula (1), X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, or a heterocyclic group. R ₂ represents an alkyl group and may be the same or different. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2.

Among the compounds represented by the general formula (1), a highly active reducing agent (hereinafter referred to as a compound of the general formula (1a)) in which at least one of R ₂ is a secondary or tertiary alkyl group is used. It is more preferable that a photothermographic material having a high density and excellent light-storing image storage stability can be obtained. In the present invention, it is preferable to use a compound of the general formula (1a) and a compound of the following general formula (2) in order to obtain a desirable color tone.

In the formula, X ₂ represents a chalcogen atom or CHR ₅ , and R ₅ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₆ represents an alkyl group, which may be the same or different, but is not a secondary or tertiary alkyl group. R ₇ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₈ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2.

  As the ratio of the combined use, [mass of compound of general formula (1a)]: [mass of compound of general formula (2)] is preferably 5:95 to 45:55, more preferably 10:90 to 40:60.

In the general formula (1), X ₁ represents a chalcogen atom or CHR ₁ . The chalcogen atom is sulfur selenium or tellurium, preferably a sulfur atom. R ₁ in CHR ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. The halogen atom is a fluorine atom, a chlorine atom, a bromine atom or the like, and the alkyl group is preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. Specific examples include methyl, ethyl, propyl, butyl, and hexyl. Alkenyl groups such as vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, Examples of the aryl group include a benzene ring and a naphthalene ring, and examples of the heterocyclic group include thiophene, furan, imidazole, pyrazole, and pyrrole.

  These groups may further have a substituent. Specific examples of the substituent include a halogen atom (fluorine, chlorine, bromine, etc.), an alkyl group (methyl, ethyl, propyl, butyl, pentyl, i-pentyl). , 2-ethylhexyl, octyl, decyl, etc.), cycloalkyl groups (cyclohexyl, cycloheptyl, etc.), alkenyl groups (ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl) -3-butenyl, etc.), cycloalkenyl groups (1-cycloalkenyl, 2-cycloalkenyl groups, etc.), alkynyl groups (ethynyl, 1-propynyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, etc.), alkylcarbonyloxy groups (Acetyloxy, etc.), alkylthio groups (methylthio, trifluoromethylthio, etc.), Sil group (acetyl group, benzoyl group), carboxyl group, alkylcarbonylamino group (acetylamino etc.), ureido group (methylaminocarbonylamino etc.), alkylsulfonylamino group (methanesulfonylamino etc.), alkylsulfonyl group (methanesulfonyl) , Trifluoromethanesulfonyl, etc.), carbamoyl group (carbamoyl, N, N-dimethylcarbamoyl, N-morpholinocarbonyl, etc.), sulfamoyl group (sulfamoyl, N, N-dimethylsulfamoyl, morpholinosulfamoyl etc.), trifluoromethyl Group, hydroxyl group, nitro group, cyano group, alkylsulfonamide group (methanesulfonamide, butanesulfonamide, etc.), alkylamino group (amino, N, N-dimethylamino, N, N-diethylamino) Etc.), sulfo group, phosphono group, sulfite group, sulfino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl etc.), alkylcarbonylaminosulfonyl group (acetamidesulfonyl, methoxyacetamidosulfonyl etc.), alkynyl Examples thereof include aminocarbonyl groups (acetamidocarbonyl, methoxyacetamidocarbonyl, etc.), alkylsulfinylaminocarbonyl groups (methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.) and the like. Moreover, when there are two or more substituents, they may be the same or different. A particularly preferred substituent is an alkyl group.

R ₂ represents an alkyl group, which may be the same or different, but at least one is preferably a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, specifically, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, t-pentyl, t-octyl. , Cyclohexyl, cyclopentyl, 1-methylcyclohexyl, 1-methylcyclopropyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group , Ester groups, halogen atoms and the like. Or it may form a saturated ring with (R _{4) n} and (R _{4) m.} R ₂ is preferably a secondary or tertiary alkyl group, and preferably has 2 to 20 carbon atoms. A tertiary alkyl group is more preferred, t-butyl, t-pentyl and 1-methylcyclohexyl are more preferred, and t-butyl is most preferred.

R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. Examples of groups that can be substituted on the benzene ring include halogen atoms such as fluorine, chlorine, bromine, alkyl groups, aryl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, amino groups, acyl groups, and acyloxy groups. , Acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, heterocyclic group and the like.

R ₃ is preferably methyl, ethyl, i-propyl, t-butyl, cyclohexyl, 1-methylcyclohexyl, 2-hydroxyethyl and the like. More preferred are methyl and 2-hydroxyethyl.

These groups may further have a substituent, and the substituents mentioned in the above R ₁ can be used as the substituent. R ₃ is preferably a C 1-20 alkyl group having a hydroxyl group or a precursor group thereof, and more preferably a C 1-5 alkyl group. Most preferred is 2-hydroxyethyl. In the most preferred combination of R ₂ and R ₃ , R ₂ is a tertiary alkyl group (t-butyl, 1-methylcyclohexyl, etc.), and R ₃ is a primary alkyl group having a hydroxyl group or a precursor group thereof ( 2-hydroxyethyl and the like). A plurality of R ₂ and R ₃ may be the same or different.

R ₄ 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.), Halogenated 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 ring Groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups (methoxy, ethoxy) , Ropyloxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc.), aryloxy groups (phenoxy, etc.), alkoxycarbonyl groups (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl groups (phenyloxycarbonyl) ), Sulfonamide groups (methanesulfonamide, ethanesulfonamide, butanesulfonamide, hexanesulfonamide group, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl groups (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl, butylamino) Sulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyridylamino Sulfonyl, etc.), 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 group, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl), amide group (acetamide, propionamide, butanamide, hexaneamide, Benzamide, etc.), sulfonyl groups (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexylsulfonyl) Phenylsulfonyl, 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 and m represent an integer of 0 to 2, and most preferably n and m are 0.

R ₄ may form a saturated ring with R ₂ and R ₃ . R ₄ is preferably a hydrogen atom, a halogen atom or an alkyl group, more preferably a hydrogen atom. A plurality of R ₄ may be the same or different.

In general formula (2), R ₅ is the same group as R ₁ , R ₇ is the same group as R _3, and R ₈ is the same group as R ₄ . R ₆ represents an alkyl group, which may be the same or different, but is not a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, and specific examples thereof include methyl, ethyl, propyl, butyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group , Ester groups, halogen atoms and the like. Further, a saturated ring may be formed with (R ₈ ) _n and (R ₈ ) _m . R ₆ is preferably methyl. Among the compounds represented by the general formula (2), the compound that is preferably used is a compound that satisfies the general formula (S) and the general formula (T) described in the specification of European Patent No. 1,278,101, Specific examples include compounds (1-24), (1-28) to (1-54), and (1-56) to (1-75) described in p21 to p28.

  Specific examples of the compounds represented by general formula (1) and general formula (2) are shown below, but the present invention is not limited to these.

  These bisphenol compounds represented by the general formulas (1) and (2) can be easily synthesized by a conventionally known method.

  The reducing agent contained in the photothermographic material is for reducing the organic silver salt to form a silver image. Examples of the reducing agent that can be used in combination with the reducing agent of the present invention include, for example, US Pat. Nos. 3,770,448, 3,773,512, and 3,593,863, RD17029 and No. 29963, JP-A-11-119372, JP-A-2002-62616, and the like.

The amount of the reducing agent including the compound represented by the general formula (1) is preferably 1 × 10 ⁻² to 10 mol, particularly preferably 1 × 10 ^{−2 to} 1.5 mol, per mol of silver. It is.

(Compound represented by formula (L))
In the general formula (L), X represents S, O, or N—R (R represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group), Y represents a —CONH—R ₇ group, —CO—R ₇ group, —CO—O—R ₇ group or —SO ₂ —R ₇ group (R ₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ each independently represent a hydrogen atom or a group capable of substituting for a benzene ring. W and Z are each independently a hydrogen atom, halogen atom, alkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, alkoxy group, alkylthio group, acyl group, acyloxy group, hydroxyl group, mercapto group, or —NR _{8 represents an} R ₉ group (R ₈ and R ₉ each independently represents a hydrogen atom, an alkyl group, an aryl group or an acyl group).

In the general formula (L), groups that can be substituted on the benzene ring represented by R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ are listed in the description of R _{4 in} the general formula (1). Mention may be made of groups which can be substituted on the benzene ring. The group capable of substituting on the benzene ring is preferably a hydrogen atom, a halogen atom or an alkyl group. Examples of the halogen atom include a fluorine atom, a bromine atom, and a chlorine atom. The alkyl group preferably has 1 to 20 (more preferably 1 to 4) carbon atoms (for example, a methyl group or an ethyl group). Group, butyl group, dodecyl group, etc.), and a hydrogen atom is particularly preferable. In N—R in X, the alkyl group represented by R is preferably an alkyl group having up to 20 carbon atoms, and examples thereof include a methyl group, an ethyl group, a butyl group, and a dodecyl group. An aryl group having 6 to 20 carbon atoms, preferably a phenyl group, a naphthyl group, a thienyl group, etc., and examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group. Etc.

—CONH—R ₇ group, —CO—R ₇ group or —CO—O—R ₇ group or —SO ₂ —R ₇ group (R ₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group. In Y represented by formula ( ₇ ), the alkyl group represented by R ₇ is preferably an alkyl group having up to 20 carbon atoms, and examples thereof include a methyl group, an ethyl group, a butyl group, and a dodecyl group. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, and examples thereof include a phenyl group, a naphthyl group, and a thienyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, A pyrazole group, a pyrrole group, etc. are mentioned.

  Examples of the halogen atom represented by W and Z include a fluorine atom, a bromine atom, and a chlorine atom, and the alkyl group includes an alkyl group having up to 20 carbon atoms (for example, a methyl group, an ethyl group, and a butyl group). An alkenyl group having up to 20 carbon atoms (for example, a vinyl group, an allyl group, a butenyl group, a hexenyl group, a hexadienyl group, an ethenyl-2-propenyl group, a 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl, etc.). As the alkynyl group, an alkynyl group having up to 20 carbon atoms (for example, ethynyl group, alkoxy group having carbon atoms) 20-propynyl group), and as the alkoxy group, an alkoxy group having up to 20 carbon atoms (for example, methoxy group, ethoxide group) The alkylthio group includes an alkylthio group having up to 20 carbon atoms (eg, methylthio group, ethylthio group, etc.), and the acyl group includes an acyl group having up to 20 carbon atoms (eg, an acetyl group, Propionyl group, butyryl group, oxalyl group, benzoyl group, naphthoyl group and the like), and acyloxy groups include acyloxy groups having up to 20 carbon atoms (eg, acetoxy group, benzoyloxy group, etc.).

In the NR ₈ R ₉ group represented by W or Z, R ₈ and R ₉ represent a hydrogen atom, an alkyl group, an aryl group or an acyl group. Examples of the alkyl group, aryl group or acyl group include W, Z The group described in the above can be mentioned. R ₈ and R ₉ are particularly preferably alkyl groups having up to 20 carbon atoms, and particularly preferably alkyl groups having up to 4 carbon atoms. Among the groups represented by W and Z, an NR ₈ R ₉ group is particularly preferred, and examples thereof include a diethylamino group and a dimethylamino group.

  As the addition amount of the compound represented by the general formula (L), the molar ratio of the compound represented by the general formula (L) and the compound represented by the general formula (1) [compound of the general formula (L) (mol )] / [Compound (mol) of general formula (1)] is required to be 0.001 to 0.2, more preferably 0.005 to 0.1, and 0.007 to 0. A range of .07 is particularly preferred.

  Although the specific example of a compound represented by general formula (L) below is given, this invention is not limited to these.

(Organic silver salt)
The organic silver salt that can be used in the present invention is relatively stable to light, but is 80 ° C. or higher in the presence of an exposed photocatalyst (such as a latent image of photosensitive silver halide) and a reducing agent. It is a silver salt that forms a silver image when heated above. The organic silver salt may be any organic material containing a source capable of reducing silver ions.

  As for such a non-photosensitive organic silver salt, paragraphs “0048” to “0049” of JP-A No. 10-62899, page 18, line 24 to No. 803 of European Patent Application Publication No. 803,764A1. 19th page, line 37, European Patent Application Publication No. 962,812A1, Japanese Patent Application Laid-Open No. 11-349591, Japanese Patent Application Laid-Open No. 2000-7683, Japanese Patent Application Laid-Open No. 2000-72711, and the like.

  Silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30, preferably 15 to 28 carbon atoms) are preferred. Preferable examples of the fatty acid silver salt include silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, and a mixture thereof.

  In the present invention, among these fatty acid silvers, it is preferable to use a fatty acid silver having a silver behenate content of preferably 50 mol% or more, more preferably 80 mol% or more, and still more preferably 90 mol% or more.

  There is no restriction | limiting in particular as a shape of the organic silver salt which can be used for this invention, Any of needle shape, rod shape, flat plate shape, and flake shape may be sufficient. In the present invention, scaly organic silver salts are preferred. Also, short needle-shaped, rectangular parallelepiped, cubic or potato-shaped amorphous particles having a major axis / uniaxial length ratio of 5 or less are preferably used. These organic silver salt particles have a feature that there is less fog at the time of heat development than long needle-like particles having a ratio of the long axis to the single axis of 5 or more. In the present specification, the scaly organic silver salt is defined as follows. The organic acid silver salt was observed with an electron microscope, the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped were designated as a, b, and c from the shortest side (c was the same as b). Then, the shorter numerical values a and b are calculated, and x is obtained as follows.

x = b / a
In this way, x is obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of x (average) ≧ 1.5 are defined as flakes. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 20 ≧ x (average) ≧ 2.0. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

  In the flake shaped particle, a can be regarded as a thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 μm or more and 0.23 μm, more preferably 0.1 μm or more and 0.20 μm or less. The average c / b is preferably 1 or more and 6 or less, more preferably 1.05 or more and 4 or less, still more preferably 1.1 or more and 3 or less, and particularly preferably 1.1 or more and 2 or less.

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

  Known methods and the like can be applied to the production and dispersion method of the organic acid silver used in the present invention. For example, Japanese Patent Application Laid-Open No. 10-62899, European Patent Application Publication No. 803,763A1, European Patent Application Publication No. 962,812A1, Japanese Patent Application Laid-Open No. 2001-167022, and Japanese Patent Application Laid-Open No. 2000-7683. No. 2000-72711, No. 2001-163889, No. 2001-163890, No. 2001-163828, No. 2001-33907, No. 2001-188313, No. 2001-83651, Reference can be made to JP-A Nos. 2001-6442 and 3001-31870.

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

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

The organic silver salt of the present invention can be used in a desired amount, but the silver amount is preferably 0.1 to 5 g / m ² , more preferably 0.3 to 3 g / m ² , still more preferably 0.5 to ² g / m ² . m ² .

(Silver halide)
The silver halide of the present invention (hereinafter also referred to as photosensitive silver halide grains or silver halide grains) will be described. The silver halide of the present invention can inherently absorb light as an intrinsic property of a silver halide crystal, or can absorb visible light or infrared light by an artificial physicochemical method. In addition, it is processed and manufactured so that physicochemical changes can occur in the silver halide crystal and / or on the crystal surface when light in any region within the light wavelength range from the ultraviolet light region to the infrared light region is absorbed. Silver halide crystal grains.

  The silver halide grains themselves used in the present invention can be prepared as a silver halide grain emulsion (also referred to as a silver halide emulsion) using a known method. That is, any of an acidic method, a neutral method, an ammonia method, etc. may be used, and a method of reacting a soluble silver salt and a soluble halogen salt may be any one of a one-side mixing method, a simultaneous mixing method, a combination thereof, and the like. 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 formation of nucleus (seed grain) and grain growth is separated. The method of performing may be used. 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 particle growth are performed separately, first, an aqueous silver salt solution and an aqueous halide solution are uniformly and rapidly mixed in an aqueous gelatin solution to produce nuclei (seed particles) (nucleation process). Then, silver halide grains are prepared by a grain growth process in which grains are grown while supplying an aqueous silver salt solution and an aqueous halide solution under controlled pAg, pH, and the like. After the formation of grains, a desired silver halide emulsion can be obtained by removing unnecessary salts and the like by a desalting step by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, or an electrodialysis method. .

  In the present invention, the grain size of the silver halide grains is preferably monodispersed. The monodispersion here means that the coefficient of variation of the particle size determined 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, tetrahedron grains, tabular grains, spherical grains, rod-like grains, potato-like grains, etc. Among these, cubic, octahedral, 14 Planar and tabular silver halide grains are preferred.

  The average aspect ratio when using tabular silver halide grains is preferably 1.5 or more and 100 or less, more preferably 2 or more and 50 or less. These are described in US Pat. Nos. 5,264,337, 5,314,798 and 5,320,958, 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 sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the 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 .; 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, and particularly preferably used at the time of nucleation of silver halide grains.

  In the present invention, the low molecular weight gelatin preferably has an average molecular weight of 50,000 or less, more preferably 2,000 to 40,000, and particularly 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 hydrolyzed by adding gelatin-degrading enzyme to a commonly used gelatin aqueous solution with an average molecular weight of about 100,000, heating 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 at the time of nucleation is preferably 5% by mass or less, and more preferably 0.05 to 3.0% by mass.

  As the silver halide grains used in the present invention, it is preferable to use a compound represented by the following general formula when forming the grains.

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. And 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.

  The polyethylene oxide compound represented by the above general formula comprises 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 an emulsion. It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved, such as a step of coating on a support. This is described in Japanese Patent Publication No. 44-9497. The polyethylene oxide compound represented by the above general formula also functions as an antifoaming agent during nucleation. The compound represented by the above general formula 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 represented by the above general formula may be present at the time of nucleation and is preferably added in advance to the dispersion medium before nucleation, but may be added during nucleation or You may add and use for the silver salt aqueous solution and halide aqueous solution which are used at the time of formation. Preferably, it is used by adding 0.01 to 2.0% by mass to the halide aqueous solution or both aqueous solutions. Further, the compound represented by the above general formula is preferably present for a time of at least 50% of the nucleation step, and more preferably for a time of 70% or more. The compound represented by the above general formula may be added as a powder or dissolved in a solvent such as methanol.

  The temperature at the time of nucleation is usually 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 when the temperature is gradually increased 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} 8.0, per liter of the reaction solution. × 10 ^-2 mol / min.

  The pH at the time of nucleation can usually be set in the range of 1.7 to 10, but the pH on the alkali side broadens the particle size distribution of the nuclei to be formed, and is preferably pH 2 to 6. Moreover, pBr at the time of nucleation is 0.05-3.0 normally, Preferably it is 1.0-2.5, More preferably, it is 1.5-2.0.

  The silver halide grains used in the present invention may be added to the image forming layer by any method. At this time, the silver halide grains are preferably arranged so as to be close to a reducible silver source (organic silver salt). .

  The silver halide grains used in the present invention are prepared in advance and added to the solution for preparing the organic silver salt grains, so that the silver halide preparation process and the organic silver salt grain preparation process are separated. Since it can be handled, it is preferable in terms of production control. However, as described in British Patent 1,447,454, when preparing organic silver salt particles, halogen components such as halide ions are used as organic silver salt forming components. By coexisting and injecting silver ions, organic silver salt particles can be produced almost simultaneously.

  It is also possible to prepare silver halide grains by converting a halogen-containing compound to an organic silver salt and converting the organic silver salt. That is, a silver halide forming component is allowed to act on a solution or dispersion of an organic silver salt prepared in advance or a sheet material containing the organic silver salt to convert a part of the organic silver salt into photosensitive silver halide. You can also.

  Examples of the silver halide forming component include compounds described in paragraph “0086” of JP-A No. 2002-287299. Thus, silver halide can also be prepared by converting part or all of silver in the organic acid silver salt into silver halide by the reaction of the organic acid silver salt and a halogen ion. Moreover, you may use together the silver halide grain manufactured by converting a part of these organic silver salt into the silver halide prepared separately.

  These silver halide grains are preferably used in an amount of 0.001 to 0.7 moles per mole of the organic silver salt, both separately prepared silver halide grains and silver halide grains obtained by conversion of the organic silver salt. It is more preferable to use 0.03 to 0.5 mol.

The silver halide used in the present invention preferably contains transition metal ions belonging to groups 6 to 11 of the periodic table. As said 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, a metal salt may be introduced as it is into silver halide, but can be introduced into silver halide in the form of a metal complex or complex ion. The content is preferably 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 mol 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 halogen ion (fluorine ion, chlorine ion, bromine ion, iodine ion), 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 during silver halide grain formation and incorporated into the silver halide grains. Preparation of silver halide grains, that is, nucleation, growth, physical ripening It 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, particularly preferably. Add at the nucleation stage. 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, and 5-273683, etc., the particles can be contained with a distribution.

  These metal compounds can be added by dissolving in water or an appropriate organic solvent (for example, alcohols, ethers, glycols, ketones, esters, amides). A method in which an aqueous solution or a metal compound and an aqueous solution in which NaCl and KCl are dissolved together is added to a water-soluble silver salt solution or a water-soluble halide solution during particle formation, or a silver salt aqueous solution and a halide aqueous solution are mixed simultaneously. When adding a third aqueous solution, a method of preparing silver halide grains by a method of simultaneous mixing of three liquids, a method of 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 of adding an aqueous solution of a powder of a metal compound or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to the halide aqueous 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 physical ripening, or at the time of chemical ripening.

  Separately prepared photosensitive silver halide grains can be desalted by known desalting methods such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. It can also be used without.

  The silver halide grains used in the present invention can be chemically sensitized. For example, by using the methods disclosed in Japanese Patent Application Laid-Open Nos. 2001-249428 and 2001-249426, a compound having a chalcogen atom such as sulfur or a noble metal compound that releases a noble metal ion such as a gold ion is used. A sensitization center (chemical sensitization nucleus) can be formed and imparted. In the present invention, it is particularly preferable to combine the chemical sensitization using the above-mentioned compound having a chalcogen atom and the chemical sensitization using a noble metal compound.

  In the present invention, it is preferably chemically sensitized by the following compound containing a chalcogen atom.

  The compound containing a chalcogen atom useful as an organic sensitizer is preferably a compound having a group capable of adsorbing to silver halide and an unstable chalcogen atom site.

  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 are 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. Particularly preferred are compounds of general formula (1-1) and general formula (1-2) disclosed in JP-A No. 2002-250984.

The amount of the compound containing a chalcogen atom as an organic sensitizer varies depending on the compound containing the chalcogen atom to be used, silver halide grains, the reaction environment for chemical sensitization, etc., but 1 mol of silver halide The amount is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻² mol, more preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol. The chemical sensitization environment in the present invention 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 particularly silver. It is preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing the nucleus. As the sensitization condition, pAg is preferably 6 to 11, more preferably The pH is preferably 7 to 10, and the pH is preferably 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 is used in the presence of an oxidizing agent capable of oxidizing the silver nuclei on the grains, using a compound containing a chalcogen atom at a temperature of 30 ° C. or lower. It is preferable to use a photosensitive silver halide emulsion that has been chemically sensitized and mixed with an organic silver salt, dispersed, dehydrated and dried.

  In addition, 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. The spectral sensitizing dye used in the present invention will be described later, but the heteroatom-containing compound having adsorptivity to silver halide is preferably a nitrogen-containing heterocyclic compound described in JP-A-3-24537. As mentioned. In the nitrogen-containing heterocyclic compound used in the present invention, the heterocyclic ring includes pyrazole ring, pyrimidine ring, 1,2,4-triazole ring, 1,2,3-triazole ring, 1,3,4-thiadiazole ring, 1 , 2,3-thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,2,3,4-tetrazole ring, pyridazine ring, 1,2,3-triazine ring, these Examples include a ring in which 2 to 3 rings are bonded, for example, a triazolotriazole ring, a diazaindene ring, a triazaindene ring, a pentaazaindene ring, and the like. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, a phthalazine ring, a benzimidazole ring, an indazole ring, a benzthiazole ring, or the like can also be applied.

  Of these, an azaindene ring is preferable, and an azaindene compound having a hydroxyl group as a substituent, for example, a hydroxytriazaindene, hydroxytetraazaindene, hydroxypentaazaindene compound, or the like is more preferable.

  The heterocyclic ring may have a substituent other than the hydroxyl group. Examples of the substituent include an alkyl group, a substituted alkyl group, an alkylthio group, an amino group, a hydroxyamino group, an alkylamino group, a dialkylamino group, an arylamino group, a carboxyl group, an alkoxycarbonyl group, a halogen atom, and a cyano group. You may have.

The addition amount of the heterocyclic ring containing compound varies over a wide range depending on the size and composition of silver halide grains, but an approximate amount of 1 × 10 in an amount per mol of silver halide ^- The range is ⁶ to 1 mol, and preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ mol.

  As described above, the silver halide grains of the present invention can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, a chloroaurate or an organic gold compound can be used as a gold sensitizer.

  In addition to the above-described sensitization methods, reduction sensitization methods and the like can also be used. Examples of reduction sensitization shell-like compounds include ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, and borane compounds. 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 according to the present invention 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. It may be a thing.

  The photosensitive silver halide grains used in the present invention are preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. As the spectral sensitizing dye, a sensitizing dye described in paragraph “0106” of JP-A No. 2002-287299 can be used. Useful sensitizing dyes used in the present invention are described in, for example, the literature described or cited in Section RD17643IV-A (December 1978, p.23), Section 18431X (August 1978, p.437). Has been. In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various laser imagers and scanner light sources. 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 basic nuclei described above. including.

  In the present invention, it is particularly preferable to use a sensitizing dye having spectral sensitivity in the infrared. Infrared spectral sensitizing dyes preferably used in the present invention are disclosed, for example, in the specifications of US Pat. Nos. 4,536,473, 4,515,888, and 4,959,294. Infrared spectral sensitizing dyes. The infrared spectral sensitizing dye used in the present invention is particularly preferably a long-chain polymethine dye characterized in that a sulfinyl group is substituted on the benzene ring of the benzazole ring.

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

  In the present invention, the above-mentioned spectral sensitizing dyes may be used alone or in combination, and the combination of sensitizing dyes is often used for the purpose of supersensitization.

  The emulsion containing silver halide grains or organic silver salt grains used in the photothermographic material of the present invention is a dye having no spectral sensitizing action with a sensitizing dye, or a substance that does not substantially absorb visible light. In addition, a substance exhibiting a supersensitization effect may be included in the emulsion, whereby the silver halide grains may be supersensitized.

  Useful sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in RD17643 (issued in December, 1978), page 23, Section J, or Japanese Patent Publication No. 9-25500, 43-4933, JP-A-59-19032, JP-A-59-192242, JP-A-5-341432, and the like. In the present invention, the following general sensitizers are used. Heteroaromatic mercapto compounds or mercapto derivative compounds represented by the formula are preferred.

General formula Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic heterocyclic ring or an aromatic condensed ring having one or more nitrogen, sulfur, oxygen, selenium, or tellurium atoms. Preferred aromatic heterocyclic rings or aromatic condensed rings include benzimidazole, naphthimidazole, benzthiazole, naphthothiazole, benzoxazole, naphthoxazole, benzselenazole, benztelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine. , Pyridazine, pyrazine, pyridine, purine, quinoline, quinazoline and the like. However, other aromatic heterocycles are also included.

  In addition, a mercapto derivative compound that substantially produces the above mercapto compound when contained in a dispersion of an organic acid silver salt or a silver halide grain emulsion is also included in the present invention. In particular, preferred examples include mercapto derivative compounds represented by the following general formula.

General formula Ar-SS-Ar
Ar in the formula is synonymous with the mercapto compound represented by the above general formula.

  The aromatic heterocyclic ring or aromatic condensed ring is, for example, a halogen atom (eg, Cl, Br, I), a hydroxyl group, an amino group, a carboxyl group, an alkyl group (eg, one or more carbon atoms, preferably , Having 1 to 4 carbon atoms) and an alkoxy group (for example, having 1 or more carbon atoms, preferably 1 to 4 carbon atoms). .

  In the present invention, in addition to the supersensitizer described above, a compound represented by the general formula (1) disclosed in JP-A No. 2001-330918 and a macrocyclic compound containing a hetero atom are supersensitized. Can be used as a sensitizer.

  The supersensitizer is preferably used in the range of 0.001 to 1.0 mole per mole of silver in the emulsion layer containing an organic silver salt and silver halide grains. It is particularly preferred to use in the range of 0.01 to 0.5 mole per mole of silver.

  In the present invention, the average grain size of silver halide is preferably 10 to 40 nm, and more preferably 10 to 35 nm. If the average grain size of the silver halide is smaller than 10 nm, the image density may be lowered, or the light irradiation image storage stability may be deteriorated. On the other hand, if it exceeds 50 nm, the image density may decrease.

  The average 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 addition, when it is not a normal crystal, for example, in the case of spherical particles, rod-like particles, etc., the diameter when considering a sphere equivalent to the volume of silver halide grains is calculated as the grain size. The measurement was performed using an electron microscope, and the average particle size was determined by averaging the measured values of 300 particle sizes.

  Further, in the present invention, by using silver halide grains having an average grain size of 55 to 100 nm and silver halide grains having an average grain size of 10 to 50 nm in combination, image density can be improved, or time-lapse image. The decrease in density can be improved (smaller). The ratio (mass ratio) of silver halide grains having an average grain size of 10 to 50 nm and silver halide grains having an average grain size of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90. : 10-60: 40.

(Image tone)
Next, the color tone of an image obtained by thermally developing a photothermographic material will be described.

  Regarding the color tone of an output image for medical diagnosis such as a conventional X-ray photographic film, it is said that a cold tone image tone is easier for a reader to obtain a more accurate diagnostic observation result. Here, the cool image tone means a pure black tone or a bluish black tone of a black image. On the other hand, the warm image tone is said to be a warm black tone with a black image, but in order to allow a more precise quantitative discussion, the International Lighting Commission (CIE) ), Based on the recommended expression.

The terms “more cold” and “more warm” regarding the color tone can be expressed by the hue angle hab at the minimum density Dmin and the optical density D = 1.0. That is, the hue angle hab is expressed by the color coordinates a ^* and b ^* of the color space L ^* a ^* b ^* color space, which is a color space having a perceptually uniform rate recommended by the International Commission on Illumination (CIE) in 1976. Using the following formula.

hab = tan ⁻¹ (b ^* / a ^* )
As a result of the examination based on the expression method based on the hue angle, the color tone after development of the photothermographic material of the present invention is preferably such that the hue angle hab is in the range of 180 ° <hab <270 °, more preferably 200 °. It was found that <hab <270 degrees, most preferably 220 degrees <hab <260 degrees. This is disclosed in Japanese Patent Laid-Open No. 2002-6463.

Conventionally, the CIE 1976 (L ^* u ^* v ^* ) color space or the (L ^* a ^* b ^* ) color space near the optical density of 1.0 is specified as u ^* , v ^* or a ^* , b ^* . It is known that a diagnostic image with a favorable color tone can be obtained by adjusting to a numerical value, and is described in, for example, Japanese Patent Application Laid-Open No. 2000-29164.

However, as a result of further intensive studies on the photothermographic material of the present invention, the horizontal axis is u ^* or a ^* , in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space. When plotting u ^* , v ^* or a ^* , b ^* at various photographic densities on a graph with the axis as v ^* or b ^* and creating a linear regression line, the linear regression line is specified. By adjusting the range, it was found that it has a diagnostic ability equal to or higher than that of conventional wet silver salt photosensitive materials. A preferable range of conditions is described below.

(1) The optical density of the silver image obtained after heat development processing of the photothermographic material was measured at 0.5, 1.0, 1.5 and the lowest optical density, and CIE 1976 (L ^* u ^* v ^* ) Linear regression line determination coefficient (multiple determination) R2 created by arranging u ^* and v ^* at each optical density in two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^*. Is preferably 0.998 to 1.000. Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (v ^* / u ^* ) is 0.7 to 2.5.

(2) The optical density of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density, and the horizontal axis of the CIE 1976 (L ^* a ^* b ^* ) color space. the a ^*, vertical axis in the two-dimensional coordinates to b ^*, a ^* in the above each optical density, coefficient of determination of the linear regression line that created arranged b ^* (multiple determination) R2 is 0.998 to 1. 000 is preferred. Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (b ^* / a ^* ) is 0.7 to 2.5.

An example of a method for creating the above-described linear regression line, that is, a method for measuring u ^* , v ^*, a ^* , and b ^{* in} the CIE 1976 color space will be described next.

A four-stage wedge sample including an unexposed portion and optical densities of 0.5, 1.0, and 1.5 is prepared using a heat development apparatus. Each wedge density part thus produced is measured with a spectrocolorimeter (Minolta Co., Ltd .: CM-3600d or the like), and u ^* , v ^* or a ^* , b ^* are calculated. The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 degrees, and measurement is performed in the transmission measurement mode. Plot u ^* , v ^* or a ^* , b ^* measured on a graph with u ^* or a ^{* on} the horizontal axis and v ^* or b ^{* on the} vertical axis to obtain a linear regression line, and the coefficient of determination (multiple determination) Find R2, intercept and slope.

  Next, a specific method for obtaining a linear regression line having the above characteristics will be described.

  In the present invention, the developed silver can be adjusted by adjusting the addition amount of a compound or the like directly or indirectly involved in the development reaction process of the following toning agent, developer, silver halide grains and aliphatic carboxylate. The shape can be optimized to obtain a preferable color tone. For example, when the developed silver shape is dendritic, it becomes a bluish direction, and when it is a filament shape, it becomes a yellowish direction. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

  Conventionally, phthalazinone or phthalazine and phthalic acids and phthalic anhydrides are generally used as toning agents. Examples of suitable toning agents include RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, and 4,021,249. Is disclosed.

  In addition to such toning agents, color tone using couplers disclosed in JP-A-11-288057, European Patent No. 1,134,611A2, etc. and leuco dyes described in detail below. Can also be adjusted. In particular, a coupler or leuco dye is preferably used for fine adjustment of the color tone.

(Leuco dye)
The leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds, and is oxidized by silver ions. Any leuco dye that forms a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  Representative leuco dyes suitable for use in the present invention are not particularly limited. For example, biphenol leuco dyes, phenol leuco dyes, indoanilin leuco dyes, acrylated azine leuco dyes, phenoxazine leuco dyes, phenodiazine leuco dyes. And dyes and phenothiazine leuco dyes. Also useful are US Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4,022,617, 4,123,282, 4,368,247, 4,461,681, and JP-A-50-36110, 59-26831, These are leuco dyes disclosed in JP-A-5-204087, JP-A-11-231460, JP-A-2002-169249, and JP-A-2002-236334.

  In order to adjust to a predetermined color tone, it is preferable to use leuco dyes of various colors singly or in combination of a plurality of types. In the present invention, when a highly active reducing agent is used, the color tone (especially yellowishness) changes depending on the amount and ratio of use, or by using fine grain silver halide, the concentration is particularly 2.0. In order to prevent the image from being excessively reddish at the above high density portion, it is preferable to use a leuco dye that develops yellow and cyan colors and to adjust the amount of use.

  The color density is preferably adjusted appropriately in relation to the color tone of the developed silver itself. In the present invention, the color tone is adjusted so as to have an image in the preferable color tone range described below by developing the color so as to have a reflection optical density of 0.01 to 0.05 or a transmission optical density of 0.005 to 0.03. preferable.

(Yellow coloring leuco dye)
In the present invention, a color image forming agent represented by the following general formula (YA), which increases its absorbance at 360 to 450 nm when oxidized, is particularly preferably used as a yellow color-forming leuco dye.

In the formula, R ₁₁ represents a substituted or unsubstituted alkyl group, R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively, and R ₁₁ and R ₁₂ are 2-hydroxyphenylmethyl groups. There is never. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on the benzene ring.

  Hereinafter, the compound of the general formula (YA) will be described in detail.

In General Formula (YA), R ₁₁ represents a substituted or unsubstituted alkyl group. When R ₁₂ is a substituent other than a hydrogen atom, R ₁₁ represents an alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms and may have a substituent.

Specifically, methyl, ethyl, butyl, octyl, i-propyl, t-butyl, t-octyl, t-pentyl, sec-butyl, cyclohexyl, 1-methyl-cyclohexyl and the like are preferable, and steric rather than i-propyl. Are preferably large groups (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl, etc.), among which secondary or tertiary alkyl Group is preferable, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferable. Examples of the substituent that R ₁₁ may have include a halogen atom, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamide group, an acyloxy group, an oxycarbonyl group, and a carbamoyl group. , Sulfamoyl group, sulfonyl group, phosphoryl group and the like.

R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively. The alkyl group represented by R ₁₂ is preferably an alkyl group having 1 to 30 carbon atoms, and the acylamino group is preferably an acylamino group having 1 to 30 carbon atoms. Among these, the description of the alkyl group is the same as R ₁₁ described above.

The acylamino group represented by R ₁₂ may be unsubstituted or substituted, and specific examples include an acetylamino group, an alkoxyacetylamino group, and an aryloxyacetylamino group. R ₁₂ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, and t-butyl. R ₁₁ and R ₁₂ are not 2-hydroxyphenylmethyl groups.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, and the description of the alkyl group is the same as that for R ₁₁ . R ₁₃ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, t-butyl and the like. Further, it is preferable either R _12, R ₁₃ is a hydrogen atom.

R ₁₄ represents a group substitutable on the benzene ring, and is, for example, the same group as described for the substituent R ₄ in the general formula (1). R ₁₄ is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or an oxycarbonyl group having 2 to 30 carbon atoms, and more preferably an alkyl group having 1 to 24 carbon atoms. Examples of the substituent of the alkyl group include an aryl group, an amino group, an alkoxy group, an oxycarbonyl group, an acylamino group, an acyloxy group, an imide group, and a ureido group, and more preferable examples include an aryl group, an amino group, an oxycarbonyl group, and an alkoxy group. preferable. These alkyl group substituents may be further substituted with these substituents.

  Next, among the compounds represented by the general formula (YA), the bisphenol compound represented by the following general formula (YB), which is particularly preferably used in the present invention, will be described.

In the formula, Z represents —S— or —C (R ₂₁ ) (R ₂₁ ′) —, and R ₂₁ and R ₂₁ ′ each represents a hydrogen atom or a substituent. Examples of the substituent represented by R ₂₁ and R ₂₁ ′ include the same groups as the substituents exemplified in the description of R _{1 in} the general formula (1). R ₂₁ and R ₂₁ ′ are preferably a hydrogen atom or an alkyl group.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ each represent a substituent, and examples of the substituent include the same groups as those described for R ₂ and R ₃ in the general formula (1).

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, but an alkyl group is more preferable. Examples of the substituent on the alkyl group include the same groups as those described in the description of the substituent in the general formula (1).

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are more preferably tertiary alkyl groups such as t-butyl, t-pentyl, t-octyl and 1-methyl-cyclohexyl.

R ₂₄ and R ₂₄ ′ each represent a hydrogen atom or a substituent, and examples of the substituent include the same groups as those described in the description of R ₄ in the general formula (1).

  Examples of the compounds represented by the general formulas (YA) and (YB) include compounds (II-1) to (II-40) described in paragraphs “0032” to “0038” of JP-A No. 2002-169249, Examples thereof include compounds (ITS-1) to (ITS-12) described in paragraph “0026” of EP 1,211,093.

  Although the specific example of the bisphenol compound represented by general formula (YA) and (YB) below is shown, this invention is not limited to these.

  The addition amount of the compound of the general formula (YA) (including hindered phenol compounds and compounds of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0. 0005 to 0.01 mol, more preferably 0.001 to 0.008 mol.

(Cyan coloring leuco dye)
Next, the cyan color-forming leuco dye that can be used in combination with the compound represented by formula (L) in the present invention will be described. In the present invention, a color image forming agent that increases its absorbance at 600 to 700 nm upon oxidation is particularly preferably used as a cyan color developing dye. JP-A-59-206831 (especially λmax is 600 to 600). Compounds within the range of 700 nm), compounds of general formula (I) to general formula (IV) of JP-A-5-204087 (specifically, (1) to (3) described in paragraphs “0032” to “0037”) Compound (18)) and compounds of general formula 4 to general formula 7 of JP-A No. 11-231460 (specifically, compounds No. 1 to No. 79 described in paragraph “0105”). The addition amount of the cyan coloring leuco dye is usually 0.00001 to 0.05 mol / Ag1 mol, preferably 0.0005 to 0.02 mol / Ag1 mol, more preferably 0.001 to 0.01 mol. / Ag1 mol.

  The addition method of the compound represented by the general formula (L), the general formula (YA) and (YB) and the cyan color-forming leuco dye is the same as the addition method of the reducing agent represented by the general formula (1). And may be added to the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form, and may be contained in the photosensitive material.

  The compounds of general formulas (1), (2), general formula (L), general formulas (YA), (YB) and cyan color-forming leuco dyes are preferably contained in an image forming layer containing an organic silver salt. However, one may be contained in the image forming layer and the other may be contained in the non-image forming layer adjacent to the image forming layer, or both may be contained in the non-image forming layer. When the image forming layer is composed of a plurality of layers, they may be contained in separate layers.

(binder)
A binder suitable for the photothermographic material is transparent or translucent and generally colorless, and is a natural polymer synthetic resin, polymer and copolymer, or other medium for forming a film, for example, paragraph “0069” of JP-A No. 2001-330918. The thing of description is mentioned. Among these, preferred binders for the photosensitive layer of the photothermographic material of the invention are polyvinyl acetals, and particularly preferred is polyvinyl butyral. These will be described in detail 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.

The binder includes —COOM, —SO ₃ M, —OSO ₃ M, —P═O (OM) ₂ , —O—P═O (OM) ₂ , —N (R) ₂ , —N ⁺ (R) _3. (M represents a hydrogen atom or an alkali metal base, R represents a hydrocarbon group), a group in which at least one polar group selected from an epoxy group, —SH, —CN and the like is introduced by copolymerization or addition reaction It is preferable to use, and —SO ₃ M and —OSO ₃ M are particularly preferable. The amount of such a polar group is 1 × 10 ⁻¹ to 1 × 10 ⁻⁸ mol / g, preferably 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / g.

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 the organic silver salt in the image forming layer, the ratio of the binder to the organic silver salt is preferably 15: 1 to 1: 2 (mass ratio), and particularly 8: 1 to 1: 1. The range of is preferable. That is, it is preferable that the binder amount of the image forming layer is 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.

  The glass transition temperature (Tg) of the binder used in the present invention is preferably 70 to 105 ° C. Tg can be obtained by measuring with a differential scanning calorimeter, and the intersection of the baseline and the endothermic peak slope is defined as Tg. Tg in the present invention is determined by the method described in “Polymer Handbook” III-139-179 (1966, Wiley and Sun, Inc.) by Brand Wrap et al.

  Tg when the binder is a copolymer resin is obtained by the following formula.

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

  Use of a binder having a Tg of 70 to 105 ° C. is preferable because a sufficient maximum density can be obtained in image formation.

  The binder of the present invention has a Tg of 70 to 105 ° C., a number average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 500,000, and a degree of polymerization of about 50 to 1,000. It is. Examples of the polymer or copolymer containing an ethylenically unsaturated monomer as a constituent unit include those described in paragraph No. “0069” of JP-A No. 2001-330918.

  Of these, particularly preferred examples include methacrylic acid alkyl esters, methacrylic acid aryl esters, and styrenes. Among such polymer compounds, a polymer compound having an acetal group is preferably used. Even a polymer compound having an acetal group is more preferably a polyvinyl acetal having an acetoacetal structure, for example, U.S. Pat. Nos. 2,358,836, 3,003,879, 2,828,204, UK The polyvinyl acetal shown by patent 771,155 etc. can be mentioned.

  As the polymer compound having an acetal group, a compound represented by the general formula (V) described in “150” of JP-A No. 2002-287299 is particularly preferable.

As the polyurethane resin that can be used in the present invention, known resins such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. Moreover, it is preferable to have a total of 2 or more hydroxyl groups, at least one at each polyurethane molecule end. Since hydroxyl groups are cross-linked with polyisocyanate which is a curing agent to form a three-dimensional network structure, it is more preferable that the hydroxyl groups 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. In the present invention, when polyurethane is used, Tg is preferably 70 to 105 ° C., elongation at break is 100 to 2000%, and stress at break is preferably 0.5 to 100 N / mm ² .

  These polymer compounds (polymers) may be used alone or in a blend of two or more.

  In the image forming layer of the present invention, the above polymer is used as a main binder. The main binder here refers to “a state in which the polymer occupies 50% by mass or more of the total binder in the image forming 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 polymer of the present invention is soluble. More preferably, a polyvinyl acetate, a polyacryl resin, a urethane resin, etc. are mentioned.

  An organic gelling agent may be contained in the image forming layer. In addition, the organic gelling agent said here is a function of giving a yield value to the system by adding it to an organic liquid, for example, polyhydric alcohols, and eliminating or reducing the fluidity of the system. A compound having

  It is also a preferred embodiment that the image forming layer coating solution contains an aqueous dispersed polymer latex. In this case, a polymer latex in which 50% by mass or more of the total binder in the coating solution for the image forming layer is dispersed in water is preferable. When the image forming layer contains a polymer latex, 50% by mass or more of the total binder in the image forming layer is preferably polymer latex, and more preferably 70% by mass or more.

  The polymer latex is a water-insoluble hydrophobic polymer dispersed as fine particles in a water-soluble dispersion medium. As the dispersion state, the polymer is emulsified in a dispersion medium, the emulsion is polymerized, the micelle is dispersed, or the polymer molecule has a partially hydrophilic structure, and the molecular chain itself is molecularly dispersed. Any of these may be used. The average particle diameter of the dispersed particles is preferably 1 to 50,000 nm, more preferably in the range of about 5 to 1,000 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution.

  The polymer latex used in the present invention may be a so-called core / shell type latex in addition to a normal polymer latex having a uniform structure. In this case, it may be preferable to change the Tg of the core and the shell. The minimum film-forming temperature (MFT) of the polymer latex according to the present invention is preferably -30 to 90 ° C, more preferably about 0 to 70 ° C. In addition, a film-forming auxiliary may be added to control the minimum film-forming temperature.

  The film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of polymer latex. For example, “Synthetic Latex Chemistry (Souichi Muroi, published by Polymer Publishing Co., Ltd.) , 1970).

  Examples of the polymer species used for the polymer latex include acrylic resins, vinyl acetate resins, polyester resins, polyurethane resins, rubber resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, and copolymers thereof. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is a number average molecular weight and is usually about 5,000 to 1,000,000, preferably about 10,000 to 100,000. When the molecular weight is too small, the mechanical strength of the photosensitive layer is insufficient.

  The polymer latex preferably has an equilibrium water content of 0.01 to 2% by mass or less, more preferably 0.01 to 1% by mass at 25 ° C. and 60% RH (relative humidity). For the definition and measurement method of the equilibrium moisture content, for example, “Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Polymer Society, Jinshokan)” can be referred to.

  Specific examples of the polymer latex include latexes described in “0173” of JP-A No. 2002-287299. These polymers may be used alone or in combination of two or more as required. As a polymer seed | species of a polymer latex, what contains about 0.1-10 mass% of carboxylic acid components, such as an acrylate or a methacrylate component, is preferable.

  Furthermore, if necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose or the like may be added within a range of 50% by mass or less of the total binder. The addition amount of these hydrophilic polymers is preferably 30% by mass or less based on the total binder of the photosensitive layer.

  In the preparation of the coating solution for the image forming layer, the order of the addition of the organic silver salt and the aqueous-dispersed polymer latex may be added first or at the same time, but preferably the polymer latex There will be later.

  Furthermore, it is preferable that an organic silver salt and further a reducing agent are mixed before adding the polymer latex. In addition, after mixing the organic silver salt and the polymer latex, if the temperature for aging is too low, the coating surface shape is impaired, and if it is too high, there is a problem that the fog rises, so the coating solution after mixing is 30 to 65 ° C. It is preferable that the above time is elapsed. Furthermore, it is preferable to be aged at 35 to 60 ° C, and a time at 35 to 55 ° C is particularly preferable. In order to maintain the temperature in this way, it is sufficient to keep the temperature of the coating solution preparation tank or the like.

  For coating of the image forming layer coating solution, it is preferable to use a coating solution that has been mixed for 30 minutes to 24 hours after mixing the organic silver salt and the aqueous dispersed polymer latex, and more preferably, 60 minutes after mixing. It is to make -12 hours pass, and it is especially preferable to use the coating liquid which passed 120 minutes-10 hours.

  Here, “after mixing” means after the organic silver salt and the aqueous polymer latex are added and the additive material is uniformly dispersed.

  It is known that the use of a cross-linking agent for the binder improves film adhesion and reduces development unevenness, but also has an effect of suppressing fogging during storage and suppressing generation of printout silver after development. is there.

  Examples of the crosslinking agent to be used include various crosslinking agents conventionally used for photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based, sulfone described in JP-A-50-96216. Acid ester-based, acryloyl-based, carbodiimide-based, and silane compound-based crosslinking agents are used, and the following isocyanate-based, silane compound-based, epoxy-based compounds, and acid anhydrides are preferable.

  Isocyanate-based crosslinking agents are isocyanates 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 divalent or trivalent polyalcohols with these isocyanates Adducts and the like. As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used.

  In addition, the adduct 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 layer 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 usually 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 a good result can be obtained even if the compound has only one functional group.

  Examples of the silane compound include compounds represented by general formulas (1) to (3) disclosed in JP-A No. 2001-264930.

  Moreover, as an epoxy compound which can be used as a crosslinking agent, what is necessary is just to have one or more epoxy groups, and there is no restriction | limiting in the number of epoxy groups, molecular weight, and others. 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, etc., 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.

  The acid anhydride used in the present invention is a compound having at least one acid anhydride group represented by the following structural formula. The number of acid anhydride groups, molecular weight, and the like are not particularly limited as long as they have one or more acid anhydride groups.

-CO-O-CO-
Said epoxy compound and acid anhydride may use only 1 type, or may use 2 or more types together. 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. This epoxy compound or acid anhydride can be added to any layer on the photosensitive layer side of the support, such as the photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc., and one of these layers Or it can add to two or more layers.

(Silver saving agent)
Preferred examples of the silver saving agent include hydrazine derivative compounds, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds.

  Specific examples of the hydrazine derivative include compounds H-1 to H-29 described in US Pat. No. 5,545,505, columns 11 to 20, US Pat. No. 5,464,738, columns 9 to 11. 1 to 12 described in JP-A-2001-27790, compounds H-1-1 to H-1-28 described in paragraphs “0042” to “0052”, and H-2-1 to H-2- 9, H-3-1 to H-3-12, H-4-1 to H-4-21, H-5-1 to H-5-5.

  Specific examples of the vinyl compound include compounds CN-01 to CN-13 described in columns 13 to 14 of US Pat. No. 5,545,515 and column 10 of US Pat. No. 5,635,339. Compounds HET-01 to HET-02 described in US Pat. No. 5,654,130, columns MA-10 to compounds MA-01 to MA-07, US Pat. No. 5,705,324 Compounds IS-01 to IS-04 described in columns 9 to 10 of the specification, and compounds 1-1 to 218-2 described in paragraphs “0043” to “0088” of JP-A-2001-125224.

  Specific examples of the phenol derivative and the naphthol derivative include compounds A-1 to A-89 described in paragraphs “0075” to “0078” of JP 2000-267222 A, and paragraph “0025” of JP 2003-66558 A. ”To“ 0045 ”. Examples thereof include compounds A-1 to A-258.

  Specific examples of the quaternary onium compound include triphenyltetrazolium.

  Specific examples of the silane compound include alkoxysilane compounds having two or more primary or secondary amino groups as shown in compounds A1 to A33 described in paragraphs “0027” to “0029” of JP-A No. 2003-5324 or The salt is mentioned.

The amount of the silver saving agent added is in the range of 1 × 10 ⁻⁵ to 1 mol, preferably 1 × 10 ^{−4 to} 5 × 10 ⁻¹ mol, per mol of the organic silver salt.

(Anti-fogging and image stabilizer)
The fog prevention and image stabilizer used in the photothermographic material of the present invention will be described.

  Since reducing agents with protons such as bisphenols and sulfonamidophenols are mainly used as reducing agents, these reducing agents are deactivated by generating active species that can extract hydrogen. It is preferable that the compound which can be converted is contained. Preferably, the colorless photo-oxidizing substance is preferably a compound capable of generating free radicals as reactive active species during exposure.

  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.

  In addition, as a compound that generates these free radicals, the generated free radicals are carbocyclic or complex in order to have a stability that allows contact with the reducing agent for a time sufficient to react with the reducing agent and inactivate it. Those having a cyclic aromatic group are preferred. Representative examples of these compounds include biimidazolyl compounds and iodonium compounds.

The amount of the biimidazolyl compound and iodonium compound added is in the range of 0.001 to 0.1 mol / m ² , preferably 0.005 to 0.05 mol / m ² . The compound can be contained in any constituent layer in the light-sensitive material of the present invention, but is preferably contained in the vicinity of the reducing agent.

  Many compounds that can release halogen atoms as active species are known as fog prevention and image stabilizers. Specific examples of the compound that generates these active halogen atoms include compounds represented by general formula (9) described in “0264” to “0271” of JP-A-2002-287299.

  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 is not a problem, and is a maximum of 150% or less, more preferably 100% in terms of the ratio to the compound that does not generate active halogen radicals. % Or less is preferable. Specific examples of compounds that generate these active halogen atoms include compounds (III-1) to (III-23) described in paragraphs “0086” to “0087” of JP-A No. 2002-169249, Compounds 1-1a to 1-1o and 1-2a to 1-2o described in paragraphs “0031” to “0034” of JP-A-2003-50441, and compounds 2a to 2z and 2aa described in paragraphs “0050” to “0056” To 2ll, 2-1a to 2-1f, compounds 4-1 to 4-32 described in paragraphs “0055” to “0058” of JP-A No. 2003-91054, and compounds 5 described in paragraphs “0069” to “0072” -1 to 5-10.

  Next, the antifoggants other than the above that are preferably used in the present invention will be described. Examples of the antifoggant preferably used in the present invention include compound examples a to j described in paragraph “0012” of JP-A-8-314059 and paragraph “0028” of JP-A-7-209797. Thiosulfonate esters A to K, compound examples (1) to (44) described from p14 of JP-A No. 55-140833, compounds described in paragraph “0063” of JP-A No. 2001-13627 (I-1 ) To (I-6), (C-1) to (C-3) described in paragraph “0066”, and compounds (III-1) to (III-) described in paragraph “0027” of JP-A-2002-90937. 108), compounds VS-1 to VS-7 and compounds HS-1 to HS-5 described in paragraph “0013” of JP-A-6-208192 as compounds of vinyl sulfones and / or β-halo sulfones. KS-1 to KS-8 compounds described in JP-A No. 2000-330235 as sulfonylbenzotriazole compounds, PR-01 to PR-08 described in JP-T-2000-515995 as substituted propene nitrile compounds, Examples thereof include compounds (1) -1 to (1) -132 described in paragraphs “0042” to “0051” of JP-A-2002-207273.

  The antifoggant is generally used in an amount of at least 0.001 mole per mole of silver. Usually, the range is 0.01 to 5 moles of the compound relative to the moles of silver, preferably 0.02 to 0.6 moles of the compound relative to the moles of silver.

  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 has a different mechanism for preventing fogging may be used. 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. Examples thereof include compounds described in the specification, JP 4,756,999, JP-A-9-288328, and JP-A-9-90550. Further, as other antifogging agents, compounds disclosed in the specifications of US Pat. No. 5,028,523 and European Patent Nos. 600,587, 605,981 and 631,176 are exemplified. Can be mentioned.

  When the reducing agent used in the present invention has an aromatic hydroxyl group (—OH), particularly in the case of bisphenols, a non-reducing compound having a group capable of forming a hydrogen bond with these groups is used. It is preferable to use together.

  Specific examples of particularly preferred hydrogen bonding compounds in the present invention include, for example, compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937. Is mentioned.

  The photothermographic material of the present invention forms a photographic image by heat development processing, and contains a toning agent that adjusts the color tone of silver as necessary dispersed in an ordinary (organic) binder matrix. Preferably it is.

  Examples of suitable toning agents for use in the present invention include those of RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. For example, the following are disclosed.

  Imides (eg, succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide); mercaptans (eg, 3-mercapto-1,2,4-triazole); phthalazinone derivatives or metal salts of these derivatives ( For example, phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); phthalazine and phthalic acids ( For example, combinations of phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid; phthalazine and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivatives and anhydrides thereof Products (eg, phthalic acid, 4-methylphthalic acid, 4 The combination and the like with at least one compound selected from nitrophthalic acid and tetrachlorophthalic anhydride). A particularly preferred colorant is a combination of phthalazinone or phthalazine with phthalic acids and phthalic anhydrides.

(Fluorosurfactant)
In the present invention, a fluorosurfactant represented by the following general formula (SF) is preferably used in order to improve film transportability and environmental suitability (accumulation in vivo) in a heat development processing apparatus.

General formula (SF)
(Rf− (L ₁ ) _n1 −) _p − (Y) _m1 − (A) _q
In the formula, Rf represents a substituent containing a fluorine atom, L ₁ represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, A Represents an anionic group or a salt thereof, n1 and m1 each represents an integer of 0 or 1, p represents an integer of 1 to 3, and q represents an integer of 1 to 3. However, when q is 1, n1 and m1 are not 0 at the same time.

  In the general formula (SF), Rf represents a substituent containing a fluorine atom. Examples of the substituent containing a fluorine atom include a fluorinated alkyl group having 1 to 25 carbon atoms (for example, a trifluoromethyl group). Trifluoroethyl group, perfluoroethyl group, perfluorobutyl group, perfluorooctyl group, perfluorododecyl group and perfluorooctadecyl group) or fluorinated alkenyl group (for example, perfluoropropenyl group, perfluorobutenyl group, Perfluorononenyl group, perfluorododecenyl group, etc.).

L ₁ represents a divalent linking group having no fluorine atom. Examples of the divalent linking group having no fluorine atom include an alkylene group (for example, a methylene group, an ethylene group, a butylene group, etc.), Alkyleneoxy group (methyleneoxy group, ethyleneoxy group, butyleneoxy group, etc.), oxyalkylene group (for example, oxymethylene group, oxyethylene group, oxybutylene group, etc.), oxyalkyleneoxy group (for example, oxymethyleneoxy group, Oxyethyleneoxy group, oxyethyleneoxyethyleneoxy group, etc.), phenylene group, oxyphenylene group, phenyloxy group, oxyphenyloxy group, or a combination of these groups.

  A represents an anionic group or a salt thereof. For example, carboxylic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfonic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfuric acid half ester Group or a salt thereof (sodium salt, potassium salt and lithium salt), a phosphoric acid group or a salt thereof (sodium salt, potassium salt and the like) and the like.

  Y represents a (p + q) -valent linking group having no fluorine atom. For example, the trivalent or tetravalent linking group having no fluorine atom is composed mainly of a nitrogen atom or a carbon atom. An atomic group is mentioned. n1 represents 0 or an integer of 1, and is preferably 1.

  The fluorine-based surfactant represented by the general formula (SF) is an alkyl compound having 1 to 25 carbon atoms into which a fluorine atom is introduced (for example, trifluoromethyl group, pentafluoroethyl group, perfluorobutyl group, perfluorooctyl). Group and a compound having a perfluorooctadecyl group) and an alkenyl compound (for example, a perfluorohexenyl group and a perfluorononenyl group), a trivalent to hexavalent alkanol compound in which no fluorine atom is introduced, and a hydroxyl group, respectively. An anionic group (A) is further introduced into the compound (partially Rf-modified alkanol compound) obtained by addition reaction or condensation reaction with 3 to 4 aromatic compounds or hetero compounds by, for example, sulfate esterification. Can be obtained.

  Examples of the trivalent to hexavalent alkanol compound include glycerin, pentaerythritol, 2-methyl-2-hydroxymethyl 1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentene, and 1,2,6-hexane. Examples include triol, 1,1,1-tris (hydroxymethyl) propane, 2,2-bis (butanol) -3, aliphatic triol, tetramethylolmethane, D-sorbitol, xylitol, D-mannitol and the like.

  Examples of the aromatic compound and hetero compound having 3 to 4 hydroxyl groups include 1,3,5-trihydroxybenzene and 2,4,6-trihydroxypyridine.

  Below, the preferable specific compound of the fluorine-type surfactant represented by general formula (SF) is shown.

  As a method for adding the fluorosurfactant represented by the general formula (SF) of the present invention to the coating solution, it can be added according to a known addition method. That is, it can be dissolved and added in alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone and acetone, polar solvents such as dimethyl sulfoxide and dimethylformamide. Further, fine particles having a size of 1 μm or less can be added after being dispersed in water or an organic solvent by sand mill dispersion, jet mill dispersion, ultrasonic dispersion or homogenizer dispersion. Many techniques for fine particle dispersion are disclosed, but they can be dispersed according to these techniques. The fluorine-based surfactant represented by the general formula (SF) is preferably added to the outermost protective layer.

The amount of the fluorosurfactant represented by the general formula (SF) of the present invention is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ² , and 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol. Is particularly preferred. If it is less than the former range, charging characteristics cannot be obtained, and if it exceeds the former range, the humidity dependence is large and the storage stability under high humidity deteriorates.

(Surface layer)
The photothermographic material of the present invention further has a ten-point average roughness (Rz (E)) of the outermost surface on the image forming layer side across the support and the outermost surface on the opposite side of the image forming layer across the support. When the ten-point average roughness (Rz (B)) of the surface is used, the value of Rz (E) / Rz (B) is preferably 0.1 or more and 0.7 or less, more preferably 0.2 or more and 0. .6 or less, particularly preferably 0.3 or more and 0.5 or less. By setting the value of Rz (E) / Rz (B) within this range, density unevenness during thermal development can be further improved. The average particle diameter of the matting agent having the maximum average particle diameter of the matting agent contained on the outermost surface on the side having the image forming layer is Le (μm), and the matting agent contained on the outermost surface on the side having the backcoat layer Lb / Le is preferably 2.0 or more and 10 or less, more preferably 3.0 or more and 4.5 or less when the average particle diameter of the matting agent having the maximum average particle diameter is Lb (μm). preferable. By setting Lb / Le within this range, density unevenness during thermal development can be further improved.

  The ten-point average roughness (Rz) is defined by the following JIS surface roughness (B0601). Ten-point average roughness (Rz) is the maximum to the fifth measured in the direction of the vertical magnification from the straight line that is parallel to the average line and does not cross the cross-sectional curve, in the portion that has been removed from the cross-sectional curve by the reference length. The difference between the average value of the altitude at the top of the mountain and the average value of the altitude at the bottom of the valley from the deepest to the fifth is expressed in micrometers (μm). As a measuring method of the center line average surface roughness (Ra), the humidity was adjusted for 24 hours in a 25 ° C., 65% RH environment under conditions where the measurement samples were not overlapped, and then the measurement was performed in the environment. Examples of the non-overlapping condition shown here include any of a method of winding with the film edge portion raised, a method of stacking paper between films, and a method of producing a frame with cardboard and fixing its four corners. It is. Examples of the measuring apparatus that can be used include a RSTPLUS non-contact three-dimensional micro surface shape measuring system manufactured by WYKO. In order to make the ten-point average roughness of the front and back surfaces of the photosensitive material within the above-mentioned range, the type, average particle size and addition amount of the matting agent used, the matting agent dispersion conditions, and the drying conditions during coating are controlled. It can be adjusted easily. In the present invention, the surface layer of the photothermographic material (when the image forming layer side or a non-photosensitive layer is provided on the opposite side of the image forming layer across the support), the object of the present invention, In order to control the surface roughness, it is preferable to use organic or inorganic powder as the matting agent. As the powder used, it is preferable to use a powder having a Mohs hardness of 5 or more. Further, when the ten-point average roughness of the outermost surface on the image forming layer side across the support is Rz (E), Rz (E) is preferably 1.0 μm or more and 4.0 μm or less, more preferably. Is 1.2 μm or more and 3.8 μm or less, particularly preferably 1.4 μm or more and 3.6 μm or less. By setting Rz within this range, it is possible to improve density unevenness in heat development and transportability during heat development.

  In the present invention, the value of Ra (E) / Ra (B) is preferably 0.4 or more and 1.5 or less, more preferably 0.5 or more and 1.4 or less. It is particularly preferable that it is 6 or more and 1.3 or less. By setting it within this range, among the effects of the present invention, in particular, the increase in fog over time is small, the transportability of the film is good, and the occurrence of uneven density during thermal development can be further improved. Further, when the center line average roughness of the outermost surface on the image forming layer side is Ra (E) across the support, Ra (E) is 40 nm or more and 150 nm or less, preferably 50 nm or more and 140 nm or less, More preferably, it is 60 nm or more and 130 nm or less. By setting it within this range, among the effects of the present invention, in particular, the increase in fog over time is small, the transportability of the film is good, and the occurrence of uneven density during thermal development can be further improved.

As the powder, a known inorganic powder or organic powder can be appropriately selected and used. Examples of the inorganic powder include titanium oxide, boron nitride, SnO ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, cerium oxide, corundum, artificial diamond, garnet. Mica, silica, silicon nitride, silicon carbide, and the like. Examples of the organic powder include powders such as polymethyl methacrylate, polystyrene, and Teflon (R). Among these, inorganic powders such as SiO ₂ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃ , mica, etc. are preferable. , SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ is particularly preferable.

  In the present invention, the powder is preferably surface-treated with a Si compound or an Al compound. By using such a surface-treated powder, the surface state of the uppermost layer can be improved. The content of Si or Al is preferably 0.1 to 10% by mass of Si and 0.1 to 10% by mass of Al with respect to the powder, and more preferably 0.1 to 5% of Si. It is particularly preferable that the mass% is 0.1 to 5 mass%, Si is 0.1 to 2 mass%, and Al is 0.1 to 2 mass%. Further, the mass ratio of Si and Al is preferably Si <Al. The surface treatment can be performed by the method described in JP-A-2-83219. The average particle diameter of the powder in the present invention is the average diameter in the case of spherical powder, the average major axis length in the case of acicular powder, and the maximum diagonal length of the plate-like surface in the case of plate-like powder. Mean values can be easily determined from measurement with an electron microscope.

  The organic or inorganic powder preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm.

  The average particle size of the organic or inorganic powder contained in the outermost layer on the photosensitive layer side is usually 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm. It is. The addition amount is usually 1.0 to 20% by mass, preferably 2.0 to 15% by mass, and more preferably based on the amount of binder used in the outermost layer (including the curing agent in the binder amount). Is 3.0-10 mass%.

  The average particle diameter of the organic or inorganic powder contained in the outermost layer on the side opposite to the photosensitive layer side across the support is usually 2.0 to 15.0 μm, preferably 3.0 to 12.0 μm. Preferably it is 4.0-10.0 micrometers. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably based on the amount of binder used for the outermost layer (including the curing agent in the binder amount). It is 0.6-5 mass%.

  Further, the coefficient of variation in the particle size distribution of the powder 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 organic or inorganic powder may be a method in which the organic or inorganic powder is previously dispersed in the coating solution, or a method of spraying the organic or inorganic powder after the coating solution is applied and before the drying is completed. May be. Moreover, when adding several types of powder, you may use both methods together.

(Support)
Examples of the support material used for the photothermographic material include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (aluminum, etc.), etc., but flexible in handling as an information recording material. A material that can be processed into a sheet or a roll having a property is suitable. Therefore, as a support in the photothermographic material of the present invention, cellulose acetate film, polyester film, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyamide film, polyimide film, cellulose triacetate film (TAC) or A plastic film such as a polycarbonate (PC) film is preferable, and a biaxially stretched PET film is particularly preferable. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  In order to improve the charging property, a conductive compound such as a metal oxide and / or a conductive polymer can be included in the constituent layer. These may be contained in any layer, but are preferably contained in the backing layer or the surface protective layer on the photosensitive layer side, the undercoat layer and the like. The conductive compounds described in columns 14 to 20 of US Pat. No. 5,244,773 are preferably used. Among these, in the present invention, the surface protective layer on the backing layer side preferably contains a conductive metal oxide. This proved that the effects of the present invention (particularly the transportability during heat development) can be further enhanced.

Here, the conductive metal oxide is crystalline metal oxide particles, and those containing oxygen defects and those containing a small amount of hetero atoms forming a donor with respect to the metal oxide used are generally used. In particular, it is particularly preferable because of its high conductivity, and the latter is particularly preferable because it does not give fog to the silver halide emulsion. Examples of metal oxides are ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O _5, etc., or a composite oxide thereof, especially ZnO, TiO ₂ and SnO ₂ are preferred. As an example of containing a heteroatom, addition Al, or In to ZnO, addition Sb, Nb, P, such as a halogen element relative to SnO _2, In addition, Nb for TiO _2, Ta Etc. are effective. The amount of these different atoms added is preferably in the range of 0.01 to 30 mol%, but particularly preferably 0.1 to 10 mol%. Furthermore, a silicon compound may be added during the production of fine particles in order to improve fine particle dispersibility and transparency.

The metal oxide fine particles used in the present invention have electrical conductivity, and the volume resistivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A Nos. 56-143431, 56-120519, 58-62647 and the like. Furthermore, as described in Japanese Examined Patent Publication No. 59-6235, a conductive material in which the above metal oxide is attached to other crystalline metal oxide particles or fibrous materials (such as titanium oxide) may be used. .

The particle size that can be used is preferably 1 μm or less, but if it is 0.5 μm or less, the stability after dispersion is good and it is easy to use. In order to make the light scattering property as small as possible, it is very preferable to use conductive particles of 0.3 μm or less because a transparent photosensitive material can be formed. Further, when the conductive metal oxide is needle-like or fibrous, the length is preferably 30 μm or less and the diameter is preferably 1 μm or less, particularly preferably the length is 10 μm or less and the diameter is 0.3 μm or less. The thickness / diameter ratio is 3 or more. As the SnO _2, are commercially available from Ishihara Sangyo Kaisha, it can be used SNS10M, SN-100P, SN- 100D, the FSS10M like.

  The photothermographic material of the present invention has an image forming layer which is at least one photosensitive layer on a support. Although only the image forming layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the image forming layer. For example, a protective layer is preferably provided on the image forming layer for the purpose of protecting the image forming layer, and the opposite surface of the support is “sticking” between the photosensitive materials or in the photosensitive material roll. In order to prevent “,” a backcoat layer is provided.

  As a binder used for these protective layer and backcoat layer, a glass transition point (Tg) is higher than that of the image forming layer, and a polymer that is less likely to be scratched or deformed, such as cellulose acetate and cellulose acetate butyrate, Selected from the above binders.

  For gradation adjustment or the like, two or more image forming layers may be provided on one side of the support or one or more layers on both sides of the support.

(dye)
In the photothermographic material of the present invention, a filter layer is formed on the same side as or opposite to the image forming layer in order to control the amount of light transmitted through the image forming layer or the wavelength distribution, or a dye is formed on the image forming layer. Or it is preferable to contain a pigment.

  As the dye used in the present invention, known compounds that absorb light in various wavelength regions can be used according to the color sensitivity of the heat developing material.

  For example, when the heat developing material of the present invention is used as an image recording material by infrared light, a squarylium dye having a thiopyrylium nucleus and a squarylium dye having a pyrylium nucleus as disclosed in JP-A-2001-83655, It is also preferable to use a thiopyrylium croconium dye similar to a squarylium dye or a pyrylium croconium 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. As the dye, the compounds described in JP-A-8-201959 are also preferable.

(Application of component layers)
The photothermographic material of the present invention may be formed by preparing a coating solution obtained by dissolving or dispersing the above-described constituent layers in a solvent, applying a plurality of coating solutions simultaneously, and then performing a heat treatment. preferable. Here, "multiple simultaneous multi-layer coating" means that a coating solution for each constituent layer (for example, an image forming layer, a protective layer) is prepared, and each layer is repeatedly coated and dried when it is coated on a support. Instead, it means that each constituent layer can be formed in such a state that a multilayer coating and drying process can be performed simultaneously. That is, the upper layer is provided before the remaining amount of all the solvents in the lower layer reaches 70% by mass or less (more preferably 90% by mass or less).

  There are no particular restrictions on the method of applying multiple layers simultaneously to each constituent layer, for example, bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, reverse roll coating method, gravure coating method, and extrusion. A known method such as a coating method can be used. Of these, the slide coating method and the extrusion coating method are more preferable. These coating methods have been described on the side having the image forming layer, but the same applies to the case of coating with undercoating when the back layer is provided. Japanese Unexamined Patent Publication No. 2000-15173 has a detailed description on the simultaneous multilayer coating method in the heat development material.

In the present invention, the silver coating amount is preferably selected in accordance with the purpose of the photothermographic material. However, for the purpose of medical images, 0.3 g / m ² or more, 1.5 g / m. m ² or less is preferable, and 0.5 g / m ² or more and 1.5 g / m ² or less are more preferable. Among the applied silver amounts, those derived from silver halide preferably account for 2 to 18%, more preferably 5 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 particle diameter equivalent to a sphere) is preferably 1 × 10 ¹⁴ particles / m ² or more and 1 × 10 ¹⁸ particles / m ² or less. Furthermore, 1 × 10 ¹⁵ pieces / m ² or more and 1 × 10 ¹⁷ pieces / m ² or less are preferable.

Furthermore, the coating density of the non-photosensitive long-chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ g or more, 1 × 10 1 per silver halide grain of 0.01 μm or more (equivalent particle diameter equivalent to sphere). ^-14 g or less is preferable, and 1 x 10 ^-16 g or more and 1 x 10 ^-15 g or less are more preferable.

  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.

In the present invention, the photothermographic material preferably contains a solvent in the range of 5 to 1,000 mg / m ² during development. It is more preferable to adjust so that it may be 100-500 mg / m < ² >. As a result, the photothermographic material has high sensitivity, low fog and high maximum density. Examples of the solvent include those described in paragraph “0030” of JP-A No. 2001-264930. However, it is not limited to these. These solvents can be used alone or in combination of several kinds.

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

(Packaging body)
When storing the photothermographic material of the present invention, the oxygen permeability and / or moisture permeability is low in order to prevent density changes and fogging over time, or to improve curling, curling, etc. It is preferable to package with a packaging material. The oxygen permeability is preferably 50 ml / atm · m ² · day or less at 25 ° C., more preferably 10 ml / atm · m ² · day or less, more preferably 1.0 ml / atm · m ² · day or less. is there. The moisture permeability is preferably 10 g / atm · m ² · day or less, more preferably 5 g / atm · m ² · day or less, and still more preferably 1 g / atm · m ² · day or less. Specific examples of the packaging material for the photothermographic material include, for example, JP-A-8-254793, JP-A-2000-206653, JP-A-2000-235241, JP-A-2002-062625, JP-A-2003-015261, JP 2003-057990 A, JP 2003-084397 A, JP 2003-098648 A, JP 2003-098635 A, JP 2003-107635 A, JP 2003-131337 A, JP 2003-146330 A, Special It is a packaging material described in Japanese Patent Application Laid-Open No. 2003-226439 and Japanese Patent Application Laid-Open No. 2003-228152. The void ratio in the package is 0.01 to 10%, preferably 0.02 to 5%. Nitrogen sealing is performed so that the nitrogen partial pressure in the package is 80% or more, preferably 90% or more. It is good to do. The relative humidity in the package is 10% to 60%, preferably 40% to 55%.

(Exposure of photothermographic material)
The photothermographic material usually uses a laser beam when recording an image. In the present invention, it is desirable to use a light source suitable for the color sensitivity imparted to the photosensitive material. For example, if 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, but the laser power is high or the photothermographic material is made transparent. From the viewpoint of being able to do so, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

  In the present invention, the exposure is preferably performed by laser scanning exposure, but various methods can be adopted as the exposure method. For example, as a first preferred method, there is a method using a laser scanning exposure machine in which the angle formed by the scanning 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 beam 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 exposure surface of the photosensitive material 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 “shift angle” from the vertical of the laser beam incident angle. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

  As a second method, it is also preferable to perform exposure using a laser scanning exposure machine that emits scanning laser light that is a vertical multi. Compared with a longitudinal single mode scanning laser beam, image quality degradation such as occurrence of interference fringe-like unevenness is reduced. In order to make a vertical multiplex, methods such as using return light by combining and applying high-frequency superposition are preferable. Note that 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.

  Furthermore, as a third aspect, it is also preferable to form an image by scanning exposure using two or more laser beams. As such an image recording method using a plurality of laser beams, it is used in an image writing unit of a laser printer or a digital copying machine that writes an image line by line in one scan because of a demand for higher resolution and higher speed. For example, Japanese Patent Laid-Open No. 60-166916 is known. This is a method in which laser light emitted from a light source unit is deflected and scanned by a polygon mirror and imaged on a photoconductor via an fθ lens or the like. This is in principle the same laser scanning optics as a laser imager or the like. Device.

  The image formation of laser light on the photoconductor in the image writing means of a laser printer or digital copying machine is for one line from the image formation position of one laser light for the purpose of writing an image by a plurality of lines in one scan. The next laser beam is imaged by shifting. Specifically, the two light beams are close to each other on the image plane in the sub-scanning direction at an order of several tens of μm, and the print density is 400 dpi (dpi is the number of dots per inch = 2.54 cm). The sub-scanning direction pitch of the two beams is 63.5 μm, and 42.3 μm at 600 dpi. Unlike the method of shifting the resolution in the sub-scanning direction as described above, in the present invention, it is preferable to form an image by condensing two or more lasers at the same place on the exposure surface while changing the incident angle. At this time, the exposure energy on the exposure surface when writing with one normal laser beam (wavelength λ [nm]) is E, and N laser beams used for exposure have the same wavelength (wavelength λ [nm]). ), In the case of the same exposure energy (En), the range of 0.9 × E ≦ En × N ≦ 1.1 × E is preferable. By doing so, energy is secured on the exposure surface, but the reflection of each laser beam to the image forming layer is reduced because the exposure energy of the laser is low, and thus the occurrence of interference fringes is suppressed.

  In the above description, the wavelengths of the plurality of laser beams are the same as λ, but those having different wavelengths may be used. In this case, it is preferable that (λ−30) <λ1, λ2,... Λn ≦ (λ + 30) with respect to λ [nm].

  In the image recording methods of the first, second, and third aspects described above, as lasers used for scanning exposure, generally well-known solid lasers such as ruby lasers, YAG lasers, glass lasers; Ne laser, Ar ion laser, Kr ion laser, CO2 laser, CO laser, He-Cd laser, N2 laser, excimer laser and other gas lasers; InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP2 laser, Semiconductor lasers such as GaSb lasers; chemical lasers, dye lasers, etc. can be selected and used in a timely manner. Among these, lasers with a semiconductor laser having a wavelength of 600 to 1200 nm due to maintenance and light source size problems. It is preferable to use light. In the laser light used in a laser imager or a laser image setter, the beam spot diameter on the exposed surface of the material when scanned with the photothermographic material is generally 5 to 75 μm as the minor axis diameter, and the major axis. The diameter is in the range of 5 to 100 μm, and the laser beam scanning speed can be set to an optimum value for each photothermographic material depending on the sensitivity and laser power at the laser oscillation wavelength specific to the photothermographic material.

(Heat development processing equipment)
The heat development processing apparatus referred to in the present invention is composed of a film supply unit represented by a film tray, a laser image recording unit, a heat development unit for supplying uniform and stable heat to the entire surface of the photothermographic material, and a film supply. It is composed of a conveying section from the section through laser recording to the discharge of the photothermographic material image-formed by thermal development to the outside of the apparatus. A specific example of the heat development processing apparatus of this embodiment is shown in FIG.

  The heat development apparatus 100 includes a feeding unit 110 that feeds a sheet-like photothermographic material (photothermographic element or simply a film) one by one, an exposure unit 120 that exposes the fed film F, and an exposure. A developing unit 130 for developing the developed film F, a cooling unit 150 for stopping development, and a stacking unit 160, a supply roller pair 140 for supplying the film F from the feeding unit, and for feeding the film to the developing unit Supply roller pair 144, and a plurality of roller pairs such as transport roller pairs 141, 142, 143, and 145 for smoothly transferring the film F between the respective parts. The heat developing part is a heating means for developing the film F, and peeling the heat drum 1 having a plurality of opposed rollers 2 that can be heated while being held in close contact with the outer periphery, and the developed film F to be sent to the cooling part. It consists of nails 6 etc.

  The transport speed of the photothermographic material in the heat developing section is preferably in the range of 10 to 200 mm / sec, more preferably 20 to 200 mm / sec. By setting the conveyance speed within this range, density unevenness during heat development can be improved and the processing time can be shortened.

The development conditions of the photothermographic material vary depending on the equipment, apparatus, or means used. Typically, development is performed by heating the photothermographic material exposed imagewise at a suitable high temperature. Is. The latent image obtained after exposure is moderately hot (about 80-200 ° C., preferably about 100-140 ° C., more preferably 110-130 ° C.) for a sufficient amount of time (generally about 1 second to intersecond). , Preferably 3 to 30 seconds, more preferably 5 to 20 seconds.)
If the heating temperature is less than 80 ° C, a sufficient image density cannot be obtained in a short time. If the heating temperature exceeds 200 ° C, the binder melts, and not only the image itself such as transfer to a roller but also transportability and a developing machine. Adversely affect. By heating, a silver image is generated by an oxidation-reduction reaction between an organic silver salt (which functions as an oxidizing agent) and a reducing agent. This reaction process proceeds without any supply of treatment liquid such as water from the outside.

  The heating device, apparatus or means may be a heating means typical as a heat generator using, for example, a hot plate, iron, hot roller, carbon or white titanium. More preferably, the heat-developable material provided with the protective layer is subjected to heat treatment by bringing the surface having the protective layer into contact with the heating means. It is preferable from the viewpoint, and it is preferable that the surface on the side having the protective layer is conveyed while being in contact with the heat roller, and is developed by heat treatment.

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

Example 1
<Preparation of undercoated photographic support>
8 W / m ² · min on both sides of a PET film colored with the following blue dye at a commercially available biaxially stretched heat-fixed thickness of 175 μm and an optical density of 0.170 (measured with Konica Densitometer PDA-65) The following undercoat coating solution a-1 is applied on one surface to a dry film thickness of 0.8 μm and dried to form an undercoat layer A-1, and on the opposite surface The undercoat coating solution b-1 shown below was applied to a dry film thickness of 0.8 μm and dried to form an undercoat layer B-1.

(Undercoating liquid a-1)
Butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (30/20/25/25% ratio) copolymer latex liquid (solid content 30%) 270 g
(C-1) 0.6g
Hexamethylene-1,6-bis (ethylene urea) 0.8g
Finish to 1L with water (undercoat coating solution b-1)
Butyl acrylate / styrene / glycidyl acrylate (40/20 /
40% ratio) copolymer latex liquid (solid content 30%) 270 g
(C-1) 0.6g
Hexamethylene-1,6-bis (ethylene urea) 0.8g
Finish to 1L with water.

Subsequently, the surface of the undercoat layer A-1 and the undercoat layer B-1 was subjected to a corona discharge of 8 W / m ² · min, and the following undercoat upper layer coating solution a- 2 is the undercoating upper layer A-2 so that the dry film thickness is 0.1 μm, and the following undercoating upper layer coating liquid b-2 is applied on the undercoating layer B-1 so that the dry film thickness is 0.4 μm. It was coated as an undercoat upper layer B-2 having an antistatic function.
(Undercoat upper layer coating solution a-2)
Gelatin 0.4g / m ² (C-1) 0.2g
(C-2) 0.2g
(C-3) 0.1 g
Silica particles (average particle size 3μm) 0.1g
Finish to 1L with water (undercoat upper layer coating solution b-2)
Sb-doped SnO ₂ (SNS10M: manufactured by Ishihara Sangyo Co., Ltd.) 60g
80 g of latex liquid (solid content 20%) containing (C-4) as a component
Ammonium sulfate 0.5g
(C-5) 12g
Polyethylene glycol (mass average molecular weight 600) 6g
Finish to 1L with water.

<Preparation of backcoat layer coating solution>
While stirring 830 g of methyl ethyl ketone (MEK), 84.2 g of cellulose acetate propionate (manufactured by Eastman Chemical: CAP482-20) and 4.5 g of polyester resin (Bostic: VitelPE2200B) were added and dissolved. Next, 0.30 g of the following infrared dye 1 is added to the dissolved liquid, and 4.5 g of a fluorine-based surfactant (manufactured by Asahi Glass Co., Ltd .: Surflon KH40) dissolved in 43.2 g of methanol and a fluorine-based surfactant. 2.3 g (Dainippon Ink Co., Ltd .: MegaFag F120K) was added and stirred well until dissolved. Next, 2.5 g of oleyl oleate was added and stirred to prepare a backcoat layer coating solution.

<Preparation of backcoat layer protective layer (surface protective layer) coating solution>
The backcoat layer protective layer was also prepared in the same manner as the backcoat layer coating solution at the following composition ratio. Silica was dispersed in MEK at a concentration of 1% with a dissolver type homogenizer, and finally added.

Cellulose acetate propionate (10% MEK solution) 15g
(Manufactured by Eastman Chemical: CAP482-20
Monodispersed silica with a monodispersity of 15% (average particle size: 10 μm))
(Surface treatment with 1% aluminum of the total mass of silica) 0.03 g
C ₈ F ₁₇ (CH ₂ CH ₂ O) ₁₂ C ₈ F ₁₇ 0.05 g
Fluorine-based surfactant (SF-17) 0.01g
Stearic acid 0.1g
Oleyl oleate 0.1g
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of photosensitive silver halide emulsion A>
(A1)
Phenylcarbamoylated gelatin 88.3g
10% aqueous methanol solution of compound (AO-1) 10ml
Potassium bromide 0.32g
Finish to 5429 ml with water (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(C1)
Potassium bromide 50.69g
Potassium iodide 2.66g
Finish to 660ml with water (D1)
Potassium bromide 151.6g
Potassium iodide 7.67g
0.93ml potassium hexachloroiridium (IV) (1% aqueous solution)
K ₂ (IrCl ₆ )
Potassium hexacyanoferrate (II) 0.004g
Hexachloroosmium (IV) potassium salt 0.004g
Finish to 1982ml with water (E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount (F1)
Potassium hydroxide 0.71g
Finish to 20ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
(H1)
Anhydrous sodium carbonate 1.72 g
Water finish 151ml AO-1: HO (CH 2 CH 2 O) n [CH (CH ₃₎ CH ₂ O] _{17 (CH 2 CH 2 O)} m H (m + n = 5~7).

  Using the mixing stirrer shown in Japanese Patent Publication No. 58-58288, while controlling 1/4 of the solution (B1) and the total amount of the solution (C1) to 20 ° C. and pAg 8.09 using the mixing stirrer Was added for 4 minutes and 45 seconds to nucleate. After 1 minute, the entire amount of solution (F1) was added. During this time, pAg was adjusted as appropriate using (E1). After 6 minutes, 3/4 amount of the solution (B1) and the total amount of the solution (D1) were added by a simultaneous mixing method over 14 minutes and 15 seconds while controlling at 20 ° 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 allowed to settle. After leaving 1500 ml of the sedimented portion and removing the supernatant, the solution (H1) was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount of silver was 1161 g per mole of silver, whereby photosensitive silver halide emulsion A was obtained.

  This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of photosensitive silver halide emulsion B>
The same procedure as in the preparation of photosensitive silver halide emulsion A was carried out except that the temperature during addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of powdered organic silver salt A>
130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved in 4720 ml of pure water at 80 ° C. Next, 540.2 ml of 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., 36.2 g of photosensitive silver halide emulsion A, 9.1 g of silver halide emulsion B and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 468.4 ml of 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an organic silver salt dispersion. Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 2 μS / cm, and centrifugal dehydration was carried out. Then, the obtained cake-like organic silver salt was converted into an air-flow dryer Flashjet dryer (Seishin). The powder organic silver salt A was dried by drying until the water content became 0.1% according to the operating conditions of the nitrogen gas atmosphere and the hot air temperature at the dryer entrance. The photothermographic material sample 1 (described later) prepared using this organic silver salt was analyzed using an electron microscope. The average particle diameter (equivalent circle diameter) was 0.08 μm, the aspect ratio was 5, and the monodispersity was 10%. Tabular grains.

  In addition, the infrared moisture meter was used for the moisture content measurement of an organic silver salt composition.

<Preparation of preliminary dispersion A>
As the image forming layer binder, 14.57 g of SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of —SO ₃ K group) was dissolved in 1457 g of MEK, and dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN While stirring in a mold, 500 g of the powdered organic silver salt A was gradually added and mixed thoroughly to prepare a preliminary dispersion A.

<Preparation of photosensitive emulsion dispersion 1>
Media type disperser DISPERMAT filled with 80% of the internal volume of 0.5 mm zirconia beads (Toray Industries, Inc .: Treceram) so that the residence time in the mill is 1.5 minutes using a pump. Photosensitive emulsion dispersion 1 was prepared by supplying to SL-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>
9.6 mg of infrared sensitizing dye 1, 9.6 mg of infrared sensitizing dye 2, 1.488 g of 2-chlorobenzoic acid, 2.779 g of stabilizer 2 and 365 mg of 5-methyl-2-mercaptobenz Infrared sensitizing dye solution A was prepared by dissolving imidazole in 31.3 ml of MEK in the dark.

<Preparation of additive solution a>
1. Reducing agent (compound and amount described in Table 1), 0.159 g of compound (YA-1) of general formula (YB), compound of general formula (L) (compound and amount described in Table 1), 54 g of 4-methylphthalic acid and 0.48 g of the infrared dye 1 were dissolved in 110 g of MEK to obtain an additive solution a.

<Preparation of additive liquid b>
1.56 g of antifogging agent 2, 0.5 g of antifogging agent 3, 0.5 g of antifogging agent 4, 0.5 g of antifogging agent 5, 3.43 g of phthalazine are dissolved in 40.9 g of MEK and added. b.

<Preparation of additive liquid c>
Silver addition agent (A1) 0.1g was melt | dissolved in MEK39.9g, and it was set as the addition liquid c.

<Preparation of additive liquid d>
0.1 g of supersensitizer 1 was dissolved in 9.9 g of MEK to obtain additive solution d.

<Preparation of additive liquid e>
0.5 g of potassium p-toluenethiosulfonate and 0.5 g of antifogging agent 6 were dissolved in 9.0 g of MEK to obtain an additive solution e.

<Preparation of additive liquid f>
An antifogging agent containing 1.0 g of vinyl sulfone [(CH ₂ ═CH—SO ₂ CH ₂ ) ₂ CHOH] was dissolved in 9.0 g of MEK to obtain an additive solution f.

<Preparation of image forming layer coating solution>
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion 1 and 15.11 g of MEK were kept at 21 ° C. with stirring, and the chemical sensitizer S-5 (0.5% methanol solution) 1000 μl was added, and after 2 minutes, 390 μl of antifoggant 1 (10% methanol solution) was added and stirred for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 10 minutes, then gold sensitizer Au-5 corresponding to 1/20 mole of the above organic chemical sensitizer was added, and further 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 maintaining the temperature at 13 ° C., 0.5 g of additive d, 0.5 g of additive e, 0.5 g of additive f, and 13.31 g of binder used in the preliminary dispersion A were added and stirred for 30 minutes. Thereafter, 1.084 g of tetrachlorophthalic acid (9.4% MEK solution) was added and stirred for 15 minutes. While continuing to stir, 12.43 g of additive a, 1.6 ml of Desmodur N3300 / Mobayic aliphatic isocyanate (10% MEK solution), 4.27 g of additive b, 4.0 g of additive c By sequentially adding and stirring, an image forming layer coating solution was obtained.

  The structures of the additives used for the preparation of each coating solution including the stabilizer solution and the image forming layer coating solution are shown below.

<Preparation of image forming layer protective layer lower layer (surface protective layer lower layer)>
Acetone 5g
MEK 21g
Cellulose acetate propionate 2.3g
(Manufactured by Eastman Chemical: CAP-141-20,
(Glass transition temperature Tg = 190 ° C)
7g of methanol
Phthalazine 0.25g
Monodispersed 15% monodispersed silica (average particle size: 3 μm) 0.170 g
(Surface treatment with 1% aluminum of the total mass of silica)
_{CH 2 = CHSO 2 CH 2 CH} 2 OCH 2 CH 2 SO 2 CH = CH 2 0.035g
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 0.01 g
Fluorine-based surfactant (SF-17: supra) 0.01g
Stearic acid 0.1g
0.1 g butyl stearate
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of image forming layer protective layer upper layer (surface protective layer upper layer)>
Acetone 5g
21g of methyl ethyl ketone
Cellulose acetate propionate 2.3g
(Manufactured by Eastman Chemical: CAP-141-20
(Glass transition temperature Tg = 190 ° C)
7g of methanol
Phthalazine 0.25g
Monodispersed 15% monodispersed silica (average particle size: 3 μm) 0.140 g
(Surface treatment with 1% by mass of aluminum based on the total mass of silica)
_{CH 2 = CHSO 2 CH 2 CH} 2 OCH 2 CH 2 SO 2 CH = CH 2 0.035g
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 0.01 g
Fluorine-based surfactant (SF-17: supra) 0.01g
Stearic acid 0.1g
0.1 g butyl stearate
α-Alumina (Mohs hardness 9) 0.1g
The upper layer and the lower layer of the image forming layer protective layer were formed by the same method as the preparation of the backcoat layer coating solution at the above composition ratio. For silica, similarly to the backcoat layer protective layer, MEK was dispersed with a dissolver type homogenizer at a concentration of 1% by mass, and finally added and stirred to obtain a coating solution for the upper and lower layers of the image forming layer protective layer. .

<Preparation of photothermographic material>
The backcoat layer coating solution and the backcoat layer protective layer coating solution prepared as described above were extruded onto the undercoating upper layer B-2 so that the dry film thickness was 3.5 μm, respectively, and the coating speed was 50 m / Application was performed in min. The drying was performed for 5 minutes using a drying air having a drying temperature of 100 ° C. and a dew point temperature of 10 ° C.

The image forming layer coating solution and the image forming layer protective layer (surface protective layer) coating solution are simultaneously coated on the subbing upper layer A-2 at an application speed of 50 m / min using an extrusion coater. Thus, photosensitive material samples 1 to 24 shown in Table 1 were prepared. As for coating, the image forming layer has a coated silver amount of 1.2 g / m ² , and the image forming layer protective layer (surface protective layer) has a dry film thickness of 3.0 μm (surface protective layer upper layer 1.5 μm, surface protective layer lower layer 1. 5 μm), followed by drying for 10 minutes using drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

The film surface pH of the obtained photothermographic material on the image forming layer side is 5.3, the Beck smoothness is 5000 seconds, the film surface pH on the backcoat layer side is 5.5, and the Beck smoothness is 6000 seconds. there were.
For sample 14, in the preparation of powdered organic silver salt A in sample 1, behenic acid 259. instead of 130.8 g behenic acid, 67.7 g arachidic acid, 43.6 g stearic acid, and 2.3 g palmitic acid. A sample was prepared in the same manner as Sample 1 except that 9 g was used.

  For sample 15, in the preparation of powdered organic silver salt A in sample 1, 540.2 ml of 1.5 mol / L potassium hydroxide aqueous solution was used instead of 540.2 ml of 1.5 mol / L sodium hydroxide aqueous solution. A sample was prepared in the same manner as Sample 1 except that it was used.

Sample 16 is the same as Sample 1 except that the fluorine-based activator of the backcoat layer protective layer and the image forming layer protective layer (upper layer and lower layer) in Sample 1 is changed from SF-17 to C ₈ F ₁₇ SO ₃ Li. A sample was prepared.

Sample 17 was replaced with SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of SO ₃ K) as the image-forming layer binder in the preparation of Preliminary Dispersion A in Sample 1. _A sample was prepared in the same manner as Sample 1 except that ₃ K group-containing polyvinyl butyral (Tg 65 ° C., SO ₃ K was contained 0.2 mmol / g) was used.

<Exposure and development processing>
The photothermographic material samples 1 to 24 prepared as described above were processed into half-cut sizes (34.5 cm × 43.0 cm), and then packaged in the following packaging materials in an environment of 25 ° C. and 50%, and room temperature for 2 weeks. Following storage, the following evaluations were made.
(Packaging material)
PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% carbon, oxygen transmission rate: 0 ml / atm · m ² · 25 ° C. · day, moisture transmission rate: 0 g / atm · m ² · 25 ° C./day. Uses a tray with paper balls.

  Evaluation was performed in the following manner using the heat development processing apparatus shown in FIG.

  After taking the photothermographic material sample from the film tray and transporting it to the laser exposure unit, from the image forming layer surface side, a semiconductor laser that has been converted to a longitudinal multimode with a high frequency superposition of 810 nm (two one with a maximum output of 35 mW). The exposure was performed by laser scanning with an exposure machine using an exposure source having a maximum output of 70 mW. At this time, an image was formed by setting the angle of the exposure surface of the photothermographic material and the exposure laser beam to 75 degrees. Thereafter, the photothermographic material is conveyed to a heat developing unit, and the heat drum is heat-developed at 123 ° C. for 13.5 seconds so that the protective layer on the image forming layer side of the photothermographic material is in contact with the drum surface. After the processing, the photothermographic material was carried out of the apparatus. At this time, the conveyance speed from the photosensitive material supply section to the image exposure section, the conveyance speed in the image exposure section, and the conveyance speed in the heat development section are each 25 mm / sec to prepare an image sample for sensitometry evaluation. did. The exposure and development were performed in a room adjusted to 23 ° C. and 50% RH. The exposure was performed in a stepped manner while reducing the exposure energy amount by log E0.05 step by step from the maximum output.

<Performance evaluation>
The following performance was evaluated for each heat-developed image.

<Image density>
The value of the highest density portion of the image obtained under the above conditions was measured with a densitometer and indicated as the image density.

《Silver tone》
A chest X-ray image was printed on each photothermographic material sample, and the silver tone after processing was visually evaluated using a Schaukasten. A wet processed laser imager film manufactured by Konica was used as a standard sample at this time, and the relative color tone with respect to the standard sample was evaluated visually by 0.5 increments according to the following criteria.

5: The same color tone as the standard sample 4: Almost the same preferred color tone as the standard sample 3: Level slightly different from the standard sample, but practically no problem 2: Color tone clearly different from the standard sample 1: Unpleasant color tone different from the standard sample << Light Irradiation Image Preservability >>
Each heat-developable photosensitive material sample was exposed and developed in the same manner as in the evaluation of silver tone, and then the change in the image was visually observed after being pasted on a Schaukasten with a luminance of 1000 lux and allowed to stand for 10 days. Evaluation was performed in 0.5 increments.

5: Almost no change 4: Slight color change is observed 3: Color change and fog increase are observed in part 2: Color change and fog increase are observed in a considerable part 1: Color change and fog change The increase in density is remarkable and strong density unevenness occurs on the entire surface.
The produced photothermographic material was placed in a sealed container whose interior was kept at 25 ° C. and 55% humidity, and then stored at 55 ° C. for 7 days (forced aging). For comparison, the same photothermographic material was stored for 7 days in a light-shielding container at 25 ° C. and 55% humidity. These samples were subjected to the same treatment as that used for evaluation of sensitometry, and the density of the fogged part was measured. Over time fogging was observed as follows.

ΔDmin (increased fog) = (fogging over time) − (fogging over time for comparison)
<< Evaluation of surface roughness >>
About the sample before the process of heat development, it measured by the method shown below using the non-contact three-dimensional surface analyzer (WYKO company RST / PLUS).

1) Objective lens: × 10.0 Intermediate lens: × 1.0
2) Measurement range: 463.4 μm × 623.9 μm
3) Pixel size: 368 × 238
4) Filter: Cylindrical correction and tilt correction 5) Smoothing: Medium smoothing 6) Scanning speed: Low
In addition, the definition of Rz and Ra followed JIS surface roughness (B0601). For each sample of 10 cm × 10 cm, the sample was divided into 100 in a grid pattern at 1 cm intervals, the center of each square region was measured, and the average value was obtained from 100 measurements.

<Evaluation of density unevenness after heat development>
The image samples for sensitometric evaluation were evaluated visually according to the following five-grade rank for density unevenness after heat development, and the results are shown in Table 1.

Rank 1: Strong density unevenness occurs on the entire surface. Rank 2: Strong density unevenness occurs on a part. Rank 3: Some weak density unevenness occurs. Rank 4: Slight density unevenness occurs. Rank 5: Generation of density unevenness is observed. In the above evaluation, ranks 4 and 5 were judged to be practically satisfactory levels.

  The results are also shown in Table 1.

  A: Reducing agent A (comparison)

  From Table 1, compared with the comparative photothermographic material, the photothermographic material of the present invention has a high density, silver tone, light-irradiated image storability, fog characteristics over time, and density unevenness after heat development. It is clear that it is excellent.

  Further, comparing Samples 16 and 1, it was found that Sample 1 has superior characteristics in terms of transportability and environmental suitability (accumulation in vivo).

  Further, comparing Samples 17 and 1, it was found that Sample 1 has superior characteristics with respect to image storage stability during high-temperature storage.

  Moreover, when the centerline average roughness (Ra) of the outermost surface by the side of the image formation layer of a sample was measured about the samples 1-20, all were 90 nm. Further, when the ten-point average roughness (Rz) of the outermost surface on the image forming layer side of the sample was measured, all were 1.4 μm. The Rz (E) / Rz (B) was determined by measuring the ten-point average roughness of the front and back surfaces, and both were 0.45.

1 is a diagram showing an example of a heat development processing apparatus for processing a photothermographic material of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat drum 2 Opposed roller 6 Peeling nail | claw 100 Heat developing apparatus 110 Feeding part 120 Exposure part 130 Developing part 140 Supply roller pair 141,142,143,145 Transport roller pair 144 Supply roller pair 150 Cooling part 160 Accumulation part F Film C Film tray L Laser beam

Claims (9)

In a photothermographic material having an image forming layer containing at least an organic silver salt, a silver halide, a binder and a reducing agent on one side of the support, a compound represented by the following general formula (1) as the reducing agent And a compound represented by the following general formula (L), a molar ratio of the compound represented by the general formula (L) and the compound represented by the general formula (1) [general formula (L) The compound (mol)] / [the compound (mol) of the general formula (1)] is 0.001 to 0.2.

[Wherein, X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₂ represents an alkyl group and may be the same or different. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2. ]

[Wherein, X represents S, O, or N—R (R represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group); Y represents a —CONH—R ₇ group, —CO—R; ₇ group, -CO-O-R ₇ group or -SO ₂ -R ₇ group (R ₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ each independently represent a hydrogen atom or a group capable of substituting for a benzene ring. W and Z are each independently a hydrogen atom, halogen atom, alkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, alkoxy group, alkylthio group, acyl group, acyloxy group, hydroxyl group, mercapto group, or —NR _{8 represents an} R ₉ group (R ₈ and R ₉ each independently represents a hydrogen atom, an alkyl group, an aryl group or an acyl group). ] 2. The photothermographic material according to claim 1, wherein the silver halide contains silver halide grains having an average grain size of 10 to 50 nm. 3. The photothermographic material according to claim 1, further comprising silver halide grains having an average grain size of 55 to 100 nm as the silver halide. 4. The photothermographic material according to claim 1, wherein the silver halide grains contain silver halide grains chemically sensitized with a compound containing a chalcogen atom as the silver halide. The photothermographic material according to claim 1, wherein the amount of silver contained in the image forming layer is 0.3 to 1.5 g / m ² . The average particle size of the largest average particle size of the matting agent contained in the image forming layer side across the support is Le (μm), and is contained in the layer opposite to the image forming layer across the support. 6. Any one of claims 1 to 5, wherein Lb / Le is 2.0 or more and 10.0 or less when the average particle size of the matting agent having the largest average particle size is Lb (μm). 2. The photothermographic material according to item 1. When the ten-point average roughness of the outermost surface on the image forming layer side is Rz (E) and the ten-point average roughness of the outermost surface on the opposite side of the image forming layer across the support is Rz (B), 6. The photothermographic material according to claim 1, wherein the value of Rz (E) / Rz (B) is 0.1 or more and 0.7 or less. The Ra (E) is 40 nm or more and 150 nm or less, when Ra (E) is the center line average roughness of the outermost surface on the image forming layer side with the support interposed therebetween. The photothermographic material according to any one of the above items. An image forming method, wherein the photothermographic material according to any one of claims 1 to 8 is thermally developed at a conveying speed of a heat developing portion of 20 to 200 mm / sec using a heat development processing apparatus. .

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