JP2005352211A - Heat developing sensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developing sensitive material which is highly sensitive, less fogging and hardly affected by temperatures and environments both before and after developing and having high Cp (covering power). <P>SOLUTION: This is a heat developing sensitive material having, at least, photosensitive silver halide particles and non-photo-sensitive organic silver salt particles, an ion reducing agent and a binder on the same surface of a support. The non-photo-sensitive organic silver salt particles have cores and shells different in silver salt composition. And the ratio of the average diameter of the organic silver salt particles in the cores and the average diameter including the shells satisfies the formula: 0.5≤L<SB>1</SB>/L<SB>2</SB><1, where L<SB>1</SB>is the average diameter of the organic silver salt particles in the cores, and L<SB>2</SB>the average diameter including organic silver salt particles in the shells. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material.

  In recent years, in the fields of medical treatment and printing plate making, reduction of waste liquid accompanying wet processing of image forming materials is strongly desired from the viewpoint of environmental protection and space saving.

  Therefore, technology related to photothermographic dry imaging materials for photographic technology that enables efficient exposure and can form clear black images with high resolution, such as laser imagers and laser imagesetters, is required. It has been said that.

  Examples of the technique relating to the photothermographic material include D.I. Morgan and B.M. U.S. Pat. Nos. 3,152,904, 3,487,075 by Shely or D.C. H. As described in “Dry Silver Photographic Materials” by Klosterboer (Handbook of Imaging Materials, page 48, 1991) and the like. A photothermographic material containing a photosensitive organic silver salt (sometimes simply referred to as an organic silver salt), a photosensitive silver halide and a reducing agent is known. Since this photothermographic material does not use any solution processing chemicals, it has the advantage of providing a user with a simpler system that does not impair the environment.

  These photothermographic materials have photosensitive silver halide grains installed in the photosensitive layer as an optical sensor, an organic silver salt as a silver ion supply source, and usually 80 to 200 ° C. depending on a built-in reducing agent. It is characterized in that an image is formed by heat development and fixing is not performed.

  However, since the photothermographic material contains an organic silver salt, photosensitive silver halide grains and a reducing agent, fog is likely to occur during the storage period before heat development. In addition, after the exposure, usually, heat development is usually performed at 80 to 200 ° C., and fixing is not performed. Therefore, even after heat development, all or part of silver halide, organic silver salt, reducing agent, and the like remain. In the storage process of the period, metallic silver is generated by heat and light, and there is a problem that the image quality such as the color tone of the silver image is easily changed.

  As a technique for preventing the fluctuation and deterioration of the silver image due to the influence of light, a technique using a halogen compound that oxidizes silver by light induction is disclosed. However, these compounds generally have a propensity to develop an oxidation function even by thermal decomposition, and thus have the effect of preventing the formation and growth of fog. It has also become clear that there are drawbacks that have the detrimental effect of reducing the coverage.

  On the other hand, these photothermographic materials always contain a developer, a silver supply source organic carboxylic acid silver salt and a photosensitive silver halide. Preservability is a big issue.

  As a technology for improving the stability of these photothermographic materials, by changing the ligand between the core and shell of the organic carboxylate silver salt particles to make the particles a core shell, the silver salt composition on the surface and inside is changed, A technique for improving developability at a relatively low temperature and obtaining a high Dmax is disclosed (for example, see Patent Document 1).

  In addition, as an eternal theme for photothermographic materials, there is a demand for higher image quality. In particular, in the field of medical images, there has been a demand for the development of high image quality technology including the color tone of silver images to enable more accurate diagnosis (see, for example, Patent Documents 2 and 3).

However, none of the technologies developed so far have an improvement effect, and cannot be said to be a complete solution to problems.
JP 2002-23303 A JP 2004-13000 A JP 2004-53985 A

  The present invention has been made in view of the above-mentioned background circumstances, and the object thereof is high sensitivity and low fog, and is hardly affected by environmental effects such as temperature and humidity both before and after the development processing. Another object of the present invention is to provide a photothermographic material that is excellent in storage stability and also has a high Cp (covering power).

  As a result of intensive studies, the inventors of the present invention have found that the thickness of the shell is important for improving the storage stability. If the shell is too thin, the storage stability is deteriorated. It has been found that fog and the like tend to deteriorate. The present invention has been made while studying countermeasures against these problems.

  That is, the object of the present invention is achieved by taking the following configuration.

(Claim 1)
In a photothermographic material having at least photosensitive silver halide particles, non-photosensitive organic silver salt particles, a silver ion reducing agent and a binder on the same surface of the support, the non-photosensitive organic silver salt particles have a silver salt composition. It has different core parts and shell parts, and the ratio of the average diameter of the organic silver salt particles in the core part to the average diameter of the organic silver salt particles including the shell part satisfies the following equation (1): A photothermographic material.

0.5 ≦ L ₁ / L ₂ <1 (1)
L ₁ : Average diameter of organic silver salt particles in the core portion L ₂ : Average diameter of organic silver salt particles including the shell portion (Claim 2)
_{2. The} photothermographic material according to claim 1, wherein the condition of the formula (1) is 0.6 ≦ L ₁ / L ₂ ≦ 0.9.

(Claim 3)
3. The photothermographic photosensitive material according to claim 1, wherein a dispersion degree of the particles composed only of the core portion of the non-photosensitive organic silver salt particles is 50% or less in a distribution range defined below. material.

Definition of width of distribution (standard deviation of particle size / average particle size) × 100 = width of distribution (%)
(Claim 4)
4. The photothermographic material according to claim 3, wherein a degree of dispersion of the non-photosensitive organic silver salt particles is 50% or less.

Definition of width of distribution (standard deviation of particle size / average particle size) × 100 = width of distribution (%)
(Claim 5)
The shell part is composed of a plurality of layers, and the ratio of the average molecular weight value of the organic silver salt constituting the outermost layer to the average molecular weight value of the organic silver salt in the core part is 1 on the basis of the core part. 5. The photothermographic material according to claim 1, wherein the photothermographic material is 1 or more and 1.4 or less.

In the present invention, the condition of the formula (1) is more preferably 0.6 ≦ L ₁ / L ₂ ≦ 0.9, and further preferably 0.65 ≦ L ₁ / L ₂ ≦ 0.75. The organic silver salt particles in the present invention preferably have an average particle size in the range of 0.01 to 3.0 μm, more preferably in the range of 0.1 to 1.0 μm.

  In the present invention, the average particle diameter refers to the length of a twill of a particle when the particle is a cubic or octahedral so-called normal crystal. Moreover, when it is not a normal crystal, for example, in the case of a spherical shape, a rod shape, or a flat shape, it means a diameter when a sphere equivalent to the volume of the particle is considered.

  The non-photosensitive organic silver salt particles are preferably monodispersed both in the core and in the core-shell structure. The monodispersion here means that the coefficient of variation (broadness of distribution) obtained by the following formula is preferably 80% or less, more preferably 50% or less.

Coefficient of variation = (standard deviation of particle size / average particle size) × 100
As a measuring method of the average particle diameter of organic silver salt, it can obtain | require, for example by transmission electron microscope observation of organic silver salt dispersion. In the present invention, the measurement of L ₁ shown in Formula (1) is obtained as an average particle diameter by taking an electron micrograph when the core is made. Then measurement of L ₂ is gradually covered with a shell on the core particles in the manner described below, taking an electron micrograph when the coating of the shell is completed, determined as the average particle size.

  According to the present invention, heat having high sensitivity and low fog, hardly affected by the environment such as temperature and humidity before and after the development process, excellent in storage stability, and high in Cp (covering power). A development photosensitive material can be provided.

  Details of the present invention will be described below.

  First, as the non-photosensitive organic silver salt, a non-photosensitive aliphatic carboxylic acid silver salt is preferable, and a general production method of the non-photosensitive aliphatic carboxylic acid silver salt will be described.

  The non-photosensitive aliphatic carboxylic acid silver salt is a reducible silver source, and a silver salt of a long-chain aliphatic carboxylic acid having 10 to 30, preferably 15 to 25 carbon atoms is preferably used. Examples of suitable silver salts include the following.

  Examples thereof include silver salts such as gallic acid, succinic acid, behenic acid, stearic acid, arachidic acid, palmitic acid and lauric acid, and preferable silver salts include silver behenate, silver arachidate and silver stearate.

  Further, in the present invention, a mixture of two or more aliphatic carboxylic acid silver salts is preferable for improving developability and forming a silver image having a high density and a high contrast. It is preferable to prepare by mixing a silver ion solution with an aromatic carboxylic acid mixture.

  On the other hand, from the viewpoint of the storage stability of the image after development, the melting point of the aliphatic carboxylic acid which is a raw material for the aliphatic carboxylate silver is 50 ° C or higher, preferably 60 ° C or higher. The content ratio is preferably 50% or more, preferably 70% or more, and more preferably 80% or more. From this viewpoint, specifically, it is preferable that the content of silver behenate is high.

  The non-photosensitive organic silver salt particles of the present invention are characterized by having a core and shell structure having different silver salt compositions. The non-photosensitive organic silver salt having a core-shell structure of the present invention has a structure of two or more layers.

  To prepare an organic silver salt having a core-shell structure, after preparing an organic silver salt to be the core in the reaction vessel, add an organic acid alkali salt solution having a composition different from that of the core and a solution containing Ag ions into the reaction vessel. However, it is necessary to perform grain formation under the condition that new organic silver salt grains are not substantially generated. That is, the “core part” refers to a part of an organic silver salt prepared in advance, and the “shell part” refers to a new organic silver salt using an organic acid alkali salt solution and a solution containing Ag ions having a composition different from that of the core part. This refers to the part where particle formation was carried out following the preparation of the core part under conditions where salt particles were not substantially generated. The shell portion may be a single layer or a multilayer of two or more layers.

  In order to prepare a shell having a structure of two or more layers, the shell can be prepared by repeating the above operation.

  In order to prevent the generation of new organic silver salt particles, it is necessary to control the concentration of the organic acid salt solution and the concentration of the water-soluble silver salt solution, the addition rate of these solutions, the temperature of the reaction field, etc. is there. In particular, it is important to control the reaction temperature, and it is preferable to confirm that there is no generation of new particles during particle formation with a transmission electron microscope or the like for confirmation. Moreover, when the organic silver salt having the core-shell structure of the present invention is analyzed by X-ray diffraction, it is preferable that diffraction images derived from different interlayer distances are confirmed.

  As other means for confirming the core-shell structure, a method of preparing a cross-section of organic silver particles and acquiring an image of an organic acid by secondary ion mass spectrometry, a method by electron diffraction, or a stable radical in the core or shell. And a method of preparing organic silver particles and taking a paramagnetic electron spin resonance spectrum.

  In the present invention, the average molecular weight of the organic silver salt of the outermost layer (outermost layer in the case where the shell part is composed of a plurality of layers) is higher than the organic silver salt of the core part. It is preferable that the ratio is 1.1 or more and 1.4 or less because there is less color change when stored in the dark.

  Preferred organic silver salts used for the core include organic silver salts selected from silver behenate, silver arachidate, silver stearate, silver palmitate, silver myristate, silver laurate, and silver caprate. Or a mixture of two or more organic silver salts.

  Preferable organic silver salts used for the shell portion include organic silver salts selected from silver behenate, silver arachidate, silver stearate, silver serinate, silver lignocerate, silver erucate, and silver oleate. These single organic silver salts or a mixture of two or more organic silver salts may be used.

  The organic silver salt having a core-shell structure in the present invention is preferably a non-photosensitive organic silver salt containing 50 mol% or more of silver behenate in the shell portion, and silver arachidate and stearic acid in the core portion. A non-photosensitive organic silver salt having a core-shell structure containing at least one of silver, silver palmitate and silver myristylate.

  Further, when the core part is composed of a non-photosensitive organic silver salt containing 50 mol% or more of silver behenate, the shell part has a core-shell structure containing at least one of silver lignocerate or silver serinate. Non-photosensitive organic silver salts are preferred.

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

  Examples of the alkali metal salt used in the present invention include sodium hydroxide, potassium hydroxide, and lithium hydroxide, and it is preferable to use sodium hydroxide and potassium hydroxide. When using both together, it is preferable that the molar ratio of both of the above-mentioned hydroxide salts is in the range of 10:90 to 75:25. When used in the above range when reacted with an aliphatic carboxylic acid to form an alkali metal salt of an aliphatic carboxylic acid, the viscosity of the reaction solution can be controlled in a good state.

  In addition, when preparing an aliphatic carboxylate silver salt in the presence of silver halide grains having an average particle diameter of 0.050 μm or less, the alkali metal of the alkali metal salt is preferably a halide having a higher potassium ratio. It is preferable because dissolution of silver particles and Ostwald ripening are prevented. Moreover, the size of the aliphatic carboxylic acid silver salt particles can be reduced as the ratio of the potassium salt is higher. A preferable ratio of the potassium salt is 50 to 100% based on the total alkali metal salt used in the step of producing the aliphatic carboxylate. The concentration of the alkali metal salt is preferably 0.1 to 0.3 mol / 1000 ml.

  When the aliphatic carboxylic acid silver salt particles according to the present invention are a mixture of a free aliphatic carboxylic acid and an aliphatic carboxylic acid silver salt in which the silver salt particles do not form a silver salt, the ratio of the former as a whole of the particles is It is preferable that it is lower than the latter from the viewpoint of image storage stability. That is, the aliphatic carboxylic acid silver salt particles according to the present invention preferably contain 3 to 10 mol% of an aliphatic carboxylic acid with respect to the aliphatic carboxylic acid silver salt. It is particularly preferably 4 to 8 mol%.

  Specifically, by determining the total aliphatic carboxylic acid amount and the free aliphatic carboxylic acid amount by the following method, respectively, the aliphatic carboxylic acid silver salt and the free aliphatic carboxylic acid amount and the respective ratios or The ratio of free fatty acid to total aliphatic carboxylic acid is calculated.

(Quantification of total aliphatic carboxylic acid content (total of those derived from both the above aliphatic carboxylic acid silver salts and free acids))
(1) About 10 mg of sample (the mass removed when peeling from the photosensitive material) is accurately weighed and placed in a 200 ml eggplant type flask.
(2) Add 15 ml of methanol and 3 ml of 4 mol / L hydrochloric acid and ultrasonically disperse for 1 minute.
(3) Put a Teflon (registered trademark) zeolite and reflux for 60 minutes.
(4) After cooling, add 5 ml of methanol from the top of the cooling tube, and wash the material adhering to the cooling tube into the eggplant-shaped flask (twice).
(5) The obtained reaction solution is extracted with ethyl acetate (100 ml of ethyl acetate and 70 ml of water are added and liquid separation extraction is performed twice).
(6) Vacuum dry at room temperature for 30 minutes.
(7) Add 1 ml of benzanthrone solution as an internal standard to a 10 ml volumetric flask (dissolve about 100 mg of benzanthrone in toluene and make up to 100 ml with toluene).
(8) Dissolve the sample in toluene and put it in the volumetric flask of (7), and make a constant volume with toluene.
(9) Perform gas chromatography (GC) measurement under the following measurement conditions.

Apparatus: HP-5890 + HP-Chemical station Column: HP-1 30 m × 0.32 mm × 0.25 μm (manufactured by HP)
Inlet: 250 ° C
Detector: 280 ° C
Oven: constant 250 ° C. Carrier gas: He
Head pressure: 80 kPa
(Quantification of free aliphatic carboxylic acid content)
(1) About 20 mg of a sample is accurately weighed, placed in a 200 ml eggplant-shaped flask, 10 ml of methanol is added, and ultrasonic dispersion is performed at 25 ° C. for 1 minute (free organic carboxylic acid is extracted).
(2) It is filtered, and the filtrate is put into a 200 ml eggplant type flask and dried (free organic carboxylic acid is separated).
(3) Add 15 ml of methanol and 3 ml of 4 mol / L hydrochloric acid and perform ultrasonic dispersion for 1 minute.
(4) Put a Teflon (registered trademark) boiling stone and reflux for 60 minutes.
(5) 60 ml of water and 60 ml of ethyl acetate are added to the resulting reaction solution, and the methyl esterified product of organic carboxylic acid is extracted into the ethyl acetate phase. Ethyl acetate extraction is performed twice.
(6) The ethyl acetate phase is dried and vacuum dried for 30 minutes.
(7) Add 1 ml of benzanthrone solution (internal standard: about 100 mg of benzanthrone dissolved in toluene to a constant volume of 100 ml) in a 10 ml volumetric flask.
(8) Dissolve (6) with toluene, put into the volumetric flask of (7), and make a constant volume with toluene.
(9) Perform GC measurement under the following measurement conditions.

Apparatus: HP-5890 + HP-Chemical station Column: HP-1 30 m × 0.32 mm × 0.25 μm (manufactured by HP)
Inlet: 250 ° C
Detector: 280 ° C
Oven: constant 250 ° C. Carrier gas: He
Head pressure: 80 kPa
[Structure and shape of aliphatic carboxylic acid silver salt particles]
In the aliphatic carboxylic acid silver salt particles according to the present invention, the average diameter (average equivalent circle diameter) is preferably 0.01 μm or more and 3.0 μm or less, and particularly preferably the average diameter is 0.1 μm or more, 1 In the case of a flat plate shape, the average thickness is 0.01 μm or more and 3.0 μm or less.

  When the average diameter is 0.01 μm or less, the transparency is excellent, but the image storage stability is poor, and when the average particle diameter is 3.0 μm or more, devitrification is severe. When the average thickness is 0.01 μm or less, the surface area is large and the supply of silver ions at the time of development is abruptly performed. Especially in the low density part, the silver ions are not used for the silver image and a large amount of silver ions remain in the film. The image storage stability is significantly deteriorated. On the other hand, when the average thickness is 3.0 μm or more, the surface area is small and the image stability is improved. However, the silver supply during development is slow, and the developed silver shape is uneven particularly in the high density portion, resulting in the highest result. Concentration tends to be low.

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

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

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

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

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

  A TEM image recorded on a suitable medium is preferably decomposed into at least 1024 pixels × 1024 pixels, preferably 2048 pixels × 2048 pixels or more, and image processing by a computer is performed. In order to perform image processing, it is preferable that an analog image recorded on a film is converted into a digital image by a scanner or the like, and shading correction, contrast / edge enhancement, and the like are performed as necessary. Thereafter, a histogram is prepared, and a portion corresponding to the aliphatic carboxylate silver is extracted by binarization processing.

  The thickness of the extracted aliphatic carboxylic acid silver salt particles is manually measured with an appropriate software of 300 or more, and an average value is obtained.

  The method for obtaining the aliphatic carboxylic acid silver salt particles having the above-mentioned shape is not particularly limited. For example, the mixed state at the time of forming the organic acid alkali metal salt soap or the mixed state at the time of adding silver nitrate to the soap. It is effective to keep it good, and to set the ratio of the organic acid to the soap and the ratio of the silver nitrate that reacts with the soap optimally.

  In the present invention, tabular aliphatic carboxylate silver salt particles (aliphatic silver carboxylate having an average diameter of 0.05 μm to 0.8 μm and an average thickness of 0.005 μm to 0.07 μm) The salt particles) are preferably pre-dispersed with a binder, a surfactant or the like, if necessary, and then dispersed and pulverized with a media disperser or a high-pressure homogenizer. As the preliminary dispersion method, for example, a general stirrer such as an anchor type or a propeller type, a high speed rotary centrifugal radiation type stirrer (dissolver), or a high speed rotary shear type stirrer (homomixer) can be used.

  Further, as the media disperser, for example, a rolling mill such as a ball mill, a planetary ball mill, a vibrating ball mill, a bead mill that is a medium agitation mill, an attritor, and other basket mills can be used, and as a high-pressure homogenizer Various types can be used, such as a type that collides with a wall, a plug, etc., a type in which liquids are collided with each other at high speed, and a type through which a thin orifice is passed.

  Ceramics used for the ceramic beads used when dispersing media include yttrium-stabilized zirconia and zirconia-reinforced alumina (ceramics containing these zirconia) because of the low generation of impurities due to friction with the beads and the dispersing machine during dispersion. Is abbreviated as zirconia in the following).

  In the apparatus used for dispersing the tabular aliphatic carboxylic acid silver salt particles according to the present invention, examples of the material of the member in contact with the aliphatic carboxylic acid silver salt particles include zirconia, alumina, silicon nitride, and boron nitride. It is preferable to use ceramics such as the above or diamond, and it is preferable to use zirconia. When the above dispersion is performed, the binder concentration is preferably added in an amount of 0.1 to 10% of the mass of the aliphatic silver carboxylate, and it is preferable that the liquid temperature does not exceed 45 ° C. from the preliminary dispersion through the main dispersion. As preferable operating conditions for this dispersion, for example, when a high-pressure homogenizer is used as the dispersing means, 29 to 100 MPa, and the number of operations is preferably 2 or more. Moreover, when using a media disperser as a dispersion | distribution means, a peripheral speed of 6-13 m / sec is mentioned as a preferable condition.

  In the present invention, it is preferable that the non-photosensitive aliphatic carboxylic acid silver salt particles are formed in the presence of a compound that functions as a crystal growth inhibitor or a dispersant. Moreover, it is preferable that the compound which functions as a crystal growth inhibitor or a dispersing agent is an organic compound having a hydroxyl group or a carboxyl group.

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

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

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

  Alcohols having 10 or less carbon atoms, preferably secondary alcohols such as isopropyl alcohol and tertiary alcohols such as t-butyl alcohol are used to increase the solubility of the alkali metal salt of aliphatic carboxylic acid in the particle production process. By reducing the viscosity and increasing the stirring efficiency, it is monodispersed and the particle size is reduced. Branched aliphatic carboxylic acids and aliphatic unsaturated carboxylic acids have higher steric hindrance than the main component linear aliphatic carboxylic acid silver when crystallization of the aliphatic carboxylic acid silver, and the disorder of the crystal lattice is large. Therefore, large crystals are not generated, and as a result, the particle size is reduced.

[Silver halide grains]
Photosensitive silver halide grains (hereinafter also simply referred to as silver halide grains) used in the photothermographic material (hereinafter also simply referred to as photosensitive material) of the present invention will be described.

  The photosensitive silver halide grains in the present invention can inherently absorb light as an intrinsic property of silver halide crystals, or artificially physicochemically emit visible light or infrared light. Physicochemical changes can occur in the silver halide crystal or on the crystal surface when absorbing light in any region within the light wavelength range from the ultraviolet light region to the infrared light region. The silver halide crystal grains processed and manufactured as described above.

  The silver halide grains themselves used in the present invention are P.I. Chifie et Physique Photographic (published by Paul Montel, 1967) by Glafkides. F. Duffin's Photographic Emission Chemistry (published by The Focal Press, 1966), V.C. L. It can be prepared as a silver halide grain emulsion using the method described in Making and Coating Photographic Emulsion (published by The Focal Press, 1964) by Zelikman et al. That is, any of an acidic method, a neutral method, an ammonia method, etc. may be used, and the formation 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, and a combination thereof. Of these methods, the so-called controlled double jet method, in which silver halide grains are prepared while controlling the formation conditions, is preferred.

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

  In the case of silver iodobromide, the iodine content is preferably in the range of 0.02 to 16 mol% / Ag mol. Even if iodine is contained so as to be distributed throughout the silver halide grains, the iodine concentration in a specific portion of the silver halide grains, for example, the central portion of the grains is increased, and the concentration in the vicinity of the surface is decreased or substantially reduced. It may be a core / shell structure that is zero.

  Grain formation is usually divided into two stages: silver halide seed grain (nuclear grain) generation and grain growth, and these may be performed continuously at one time, or nucleus (seed grain) formation and grain growth are separated. It is also possible to do this. As the particle forming conditions, a controlled double jet method in which particles are formed by controlling pAg, pH and the like is preferable in that the particle shape and size can be controlled. For example, in the case of a method in which nucleation and grain growth are performed separately, first, a soluble silver salt and a soluble halogen salt are uniformly and rapidly mixed in an aqueous gelatin solution to perform nucleation (nucleation step). Silver halide grains are prepared by a grain growth process in which grains are grown while supplying a soluble silver salt and a soluble halogen salt under controlled pAg, pH, and the like.

  The silver halide grains used in the present invention preferably have a smaller grain size of the silver halide grains in order to keep white turbidity and color tone (yellowishness) after image formation low and to obtain good image quality. As a value when particles having a diameter of less than 0.02 μm are excluded from measurement, 0.030 μm or more and 0.055 μm or less are preferable.

  Here, the grain size means the length of the edge of the silver halide grain when the silver halide grain is a so-called normal crystal of a cube or octahedron. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface.

  In the present invention, the silver halide grains are preferably monodispersed. The term “monodispersed” as used herein means that the coefficient of variation of the particle diameter obtained by the following formula is 30% or less. Preferably it is 20% or less, More preferably, it is 15% or less.

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

  When tabular silver halide grains are used, the average aspect ratio 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, 5,320,958, etc., and the desired tabular grains can be easily obtained. Further, grains having rounded corners of silver halide grains can be preferably used.

  The crystal habit on the outer surface of the silver halide grain is not particularly limited, but when a spectral sensitizing dye having crystal habit (plane) selectivity is used 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. Conversely, when using a sensitizing dye that selectively adsorbs on the crystal face of the Miller index [111], it is preferable to increase the proportion of the [111] face on the outer surface of the silver halide grains. 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 grain formation, and particularly preferably used at the time of nucleation of silver halide grains. The low molecular weight gelatin has an average molecular weight of 50,000 or less, preferably 2000 to 40000, more preferably 5000 to 25000. The average molecular weight of gelatin can be measured by gel filtration chromatography.

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

  As the silver halide grains used in the present invention, a polyethylene oxide compound represented by the following general formula can be used at the time of grain formation.

Formula _{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 is used in the production of a light-sensitive material in which a gelatin aqueous solution is produced, a water-soluble halide and a water-soluble silver salt are added to the gelatin solution, and a silver halide emulsion is supported. It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved, such as a coating step, and the technology used as the antifoaming agent is, for example, JP-A-44. No. 9497, the polyethylene oxide compound represented by the above general formula also functions as an antifoaming agent during nucleation.

  The polyethylene oxide compound represented by the above general formula is preferably used in an amount of 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, You may add and use for the silver salt aqueous solution and halide aqueous solution which are used at the time of nucleation. Preferably, it is used by adding 0.01 to 2.0% by mass to the aqueous halide solution or both aqueous solutions. Further, it is preferable to exist for at least 50% of the nucleation step, and more preferably for 70% or more. The polyethylene oxide 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 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 raised and the temperature at the end of nucleation is 40 ° C.) and vice versa.

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

  The silver halide grains of the present invention may be added to the photosensitive layer by any method. At this time, the silver halide grains are arranged so as to be close to a reducible silver source (aliphatic carboxylic acid silver salt). Is preferable in order to obtain a photothermographic material having high sensitivity and high covering power (CP).

  The silver halide grains of the present invention are prepared in advance and added to a solution for preparing aliphatic carboxylic acid silver salt grains, so that the silver halide grain preparation step and the aliphatic carboxylic acid silver salt can be added. The particle preparation process can be handled separately, and is most preferable for the control of the manufacturing process.

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

  Regarding the technology for preventing fogging and stabilizing the image, basically, the silver ions or metal silver is prevented from being reduced by the silver ions being reduced during storage before and after development. It is also important to consider the fact that the generated silver (metallic silver) is oxidized and disappeared, or that the metallic silver is prevented from functioning as a catalyst for the reaction of reducing silver ions. It is done.

  The antifogging and image stabilizer used in the photothermographic material of the invention will be specifically described below.

  In the photothermographic material of the present invention, bisphenols can be mainly used as the silver ion reducing agent, as will be described later. However, under the storage conditions before development of the imaging material, and heat development. It is preferred that a compound capable of inactivating the reducing agent under the subsequent storage conditions is contained. Preferably, a compound capable of preventing generation of a phenoxyl radical from the reducing agent or a compound capable of trapping the generated phenoxyl radical and stabilizing it so as not to function as a silver ion reducing agent Is preferred. Suitable compounds having such functions and functions include non-reducing compounds having a group capable of forming a hydrogen bond with the hydroxyl group of bisphenols, such as phosphoryl group, sulfoxide group, sulfonyl group, carbonyl group, amide And compounds having a group, an ester group, a urethane group, a ureido group, a tertiary amino group, a nitrogen-containing aromatic group, and the like. Particularly preferred are compounds having a sulfonyl group, a sulfoxide group, or a phosphoryl group. Specific examples are disclosed in JP-A-6-208192, JP-A-2001-215648, JP-A-350235, JP-A-2002-6444, JP-A-2002-18264, and the like. Further, specific compounds having a vinyl group are disclosed in JP 2000-515995 A, JP 2002-207273 A, JP 2003-140298 A, and the like.

  Also used in combination with compounds that can oxidize silver (metal silver), for example, compounds that can oxidize silver by releasing an oxidizing halogen radical or interacting with silver to form a charge transfer complex can do. Specific examples of compounds having such functions include JP-A-50-120328, JP-A-59-57234, JP-A-4-232939, JP-A-6-208193, JP-A-10-197989, and the United States. It is disclosed in Japanese Patent No. 5,460,938, Japanese Patent Application Laid-Open No. 7-2781, and the like. In particular, in the imaging material according to the present invention, specific examples of preferable compounds include halogen radical releasing compounds that can be represented by the following general formula (OFI).

Formula _{(OFI) Q 2 -Y-C} (X 1) (X 3) (X 2)
In general formula (OFI), Q ₂ represents an aryl group or a heterocyclic group. X ₁ , X ₂ and X ₃ each represent a hydrogen atom, a halogen atom, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group or an aryl group, at least one of which is a halogen atom. Y represents —C (═O) —, —SO— or —SO ₂ —.

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

The heterocyclic group represented by Q ₂ is a 3- to 10-membered saturated or unsaturated heterocyclic group containing at least one atom of N, O or S, which may be monocyclic, Furthermore, you may form a condensed ring with another ring.

  The heterocyclic group is preferably a 5- to 6-membered unsaturated heterocyclic group which may have a condensed ring, and more preferably a 5- to 6-membered aromatic heterocyclic ring which may have a condensed ring. It is a group. More preferably, it is a 5- to 6-membered aromatic heterocyclic group optionally having a condensed ring containing a nitrogen atom, and particularly preferably 5 a condensed ring containing 1 to 4 nitrogen atoms. A 6-membered aromatic heterocyclic group. The heterocyclic ring in such a heterocyclic group is preferably imidazole, pyrazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline Cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzthiazole, indolenine, tetrazaindene, more preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, Triazine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinoaline Zolin, cinnoline, tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzthiazole, tetrazaindene, more preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, thiadiazole, quinoline, phthalazine, naphthyridine, Quinoxaline, quinazoline, cinnoline, tetrazole, thiazole, benzimidazole, and benzthiazole are preferable, and pyridine, thiadiazole, quinoline, and benzthiazole are particularly preferable.

The aryl group and heterocyclic group represented by Q ₂ may have a substituent in addition to —Y—C (X ₁ ) (X ₂ ) (X ₃ ), and the substituent is preferably an alkyl group, Alkenyl group, aryl group, alkoxy group, aryloxy group, acyloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl Group, carbamoyl group, sulfonyl group, ureido group, phosphoric acid amide group, halogen atom, cyano group, sulfo group, carboxyl group, nitro group, heterocyclic group, more preferably alkyl group, aryl group, alkoxy group, aryl Oxy group, acyl group, acylamino group, alkoxycarbonylamino , Aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, ureido group, phosphoric acid amide group, halogen atom, cyano group, nitro group, heterocyclic group, more preferably alkyl group, aryl group, alkoxy group Group, aryloxy group, acyl group, acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, halogen atom, cyano group, nitro group, heterocyclic group, particularly preferably alkyl group, aryl group, halogen atom .

X ₁ , X ₂ and X ₃ are preferably a halogen atom, haloalkyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, sulfamoyl group, sulfonyl group or heterocyclic group, more preferably a halogen atom , A haloalkyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group and a sulfonyl group, more preferably a halogen atom and a trihalomethyl group, and particularly preferably a halogen atom. Of the halogen atoms, preferred are a chlorine atom, a bromine atom and an iodine atom, more preferred are a chlorine atom and a bromine atom, and particularly preferred is a bromine atom.

Y represents —C (═O) —, —SO— or —SO ₂ —, preferably —SO ₂ —.

The amount of these compounds added can be 1 × 10 ⁻⁴ to 1 mol, preferably 1 × 10 ^{−3 to} 5 × 10 ⁻² mol, per mol of silver.

  In addition, in the imaging material which concerns on this invention, the polyhalogen compound currently disclosed by Unexamined-Japanese-Patent No. 2003-5041 can be used similarly to the compound which can be represented by said general formula (OFI).

[Polymer PO inhibitor]
Furthermore, in the photothermographic imaging material according to the present invention, a polymer having at least one repeating unit of a monomer having a halogen radical releasing group as disclosed in JP-A No. 2003-91054 is used as an image stabilizer. However, the silver image can be further stabilized, and it is also preferable from the viewpoint of high sensitivity and high CP. In particular, the photothermographic imaging material according to the present invention provides unexpectedly good results.

  In addition to the above compounds, the photothermographic material of the invention may contain a compound conventionally known as an antifoggant. 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, No. 4,756,999, JP-A-9-288328 and JP-A-9-90550. Further, other antifoggants include compounds disclosed in US Pat. No. 5,028,523 and European Patents 600,587, 605,981, and 631,176. .

[Polycarboxyl compound]
In the photothermographic material according to the invention, it is also preferable to use a compound represented by the following general formula (PC) as an antifoggant and a storage stabilizer for the material.

Formula (PC) R- (CO-OM) _n
[Wherein, R represents an atom, an aliphatic group, an aromatic group, a heterocyclic group, or an atomic group that can be bonded to each other to form a ring. M represents a hydrogen atom, a metal atom, a quaternary ammonium group or a phosphonium group. n represents an integer of 2 to 20. ]
In the general formula (PC), examples of the connectable atom represented by R include atoms such as nitrogen, oxygen, sulfur, and phosphorus.

  Examples of the aliphatic group represented by R include a linear or branched alkyl, alkenyl, alkynyl or cycloalkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms. Specifically, for example, methyl, ethyl, propyl, butyl, hexyl, decyl, dodecyl, isopropyl, t-butyl, 2-ethylhexyl, allyl, 2-butenyl, 7-octenyl, propargyl, 2-butynyl, cyclopropyl, cyclopentyl , Cyclohexyl, cyclododecyl and the like.

  Examples of the aromatic group represented by R include those having 6 to 20 carbon atoms, and specific examples thereof include phenyl, naphthyl, and anthranyl groups.

  The heterocyclic group represented by R may be a monocyclic ring or a condensed ring, and includes a 5- to 6-membered heterocyclic group having at least one of O, S, and N atoms and an amine oxide group in the ring. . Specifically, for example, pyrrolidine, piperidine, tetrahydrofuran, tetrahydropyran, oxirane, morpholine, thiomorpholine, thiopyran, tetrahydrothiophene, pyrrole, pyridine, furan, thiophene, imidazole, pyrazole, oxazole, thiazole, isoxazole, isothiazole, triazole, And groups derived from tetrazole, thiadiazole, oxadiazole, and these benzerogues.

If R is formed by R ₁ and R _2, R ₁ and R ₂ have the same meanings as R, and, R ₁ is may be the same as or different from R _2. Examples of the ring forming with R ₁ and R ₂ include a 4- to 7-membered ring. Preferably it is a 5-7 membered ring. Preferred groups for R ₁ and R ₂ are aromatic groups and heterocyclic groups. The aliphatic group, aromatic group or heterocyclic group represented by R ₁ and R ₂ may be further substituted with a substituent, such as a halogen atom (for example, chlorine atom, bromine atom, etc.), alkyl Groups (eg, methyl, ethyl, isopropyl, hydroxyethyl, methoxymethyl, trifluoromethyl, t-butyl, etc.), cycloalkyl groups (eg, cyclopentyl, cyclohexyl, etc.), aralkyl groups (eg, benzyl) Group, 2-phenethyl group etc.), aryl group (eg phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group etc.), alkoxy group (eg methoxy group, ethoxy group, isopropoxy group, butoxy group etc.), Aryloxy groups (eg phenoxy group, 4-methoxyphenoxy group etc.), cyano groups, acylamino groups (eg Tilamino group, propionylamino group, etc.), alkylthio group (eg, methylthio group, ethylthio group, butylthio group, etc.), arylthio group (eg, phenylthio group, p-methylphenylthio group, etc.), sulfonylamino group (eg, methanesulfonylamino group, Benzenesulfonylamino group), ureido group (for example, 3-methylureido group, 3,3-dimethylureido group, 1,3-dimethylureido group, etc.), sulfamoylamino group (dimethylsulfamoylamino group, diethylsulfate) Famoylamino group, etc.), carbamoyl group (eg methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group etc.), sulfamoyl group (eg ethylsulfamoyl group, dimethylsulfamoyl group etc.), alkoxycarbonyl group (eg methoxycal Nyl group, ethoxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenoxycarbonyl group, p-chlorophenoxycarbonyl group, etc.), sulfonyl group (eg, methanesulfonyl group, butanesulfonyl group, phenylsulfonyl group, etc.), acyl group (eg, Acetyl group, propanoyl group, butyroyl group, etc.), amino group (methylamino group, ethylamino group, dimethylamino group etc.), hydroxy group, nitro group, nitroso group, amine oxide group (eg pyridine-oxide group etc.), imide Groups (for example, phthalimido group, etc.), disulfide groups (for example, benzene disulfide group, benzthiazolyl-2-disulfide group, etc.), heterocyclic groups (for example, pyridyl group, benzimidazolyl group, benzthiazolyl group, benzoxazolyl group, etc.) It is done. R ₁ and R ₂ may have one or more of these substituents. Further, each substituent may be further substituted with the above-described substituent. R ₁ and R ₂ may be the same or different. The general formula (PC) is also effective as an oligomer or polymer (R- (COOM) _n 0) _m . n is 2 to 20, and m is preferably 1 to 100 or a molecular weight of 50000 or less.

  JP-A-58-95338, JP-A-10-288824, JP-A-11-174621, JP-A-11-218877, JP-A-2000-10237, JP-A-2000-10236, JP-A-2000-10235, 2000-2000. The dicarboxylic acids described in Nos. -10233, 2000-10232, and 2000-10231 can be preferably used in combination.

[Thiosulfonic acid inhibitors]
The imaging material according to the present invention preferably contains a compound represented by the following general formula (ST).

General formula (ST) Z-SO ₂ · SM
In the formula, Z represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group, and M represents a metal atom or an organic cation.

  In the compound represented by the general formula (ST), the alkyl group, aryl group, heterocyclic group, aromatic ring and heterocyclic ring represented by Z in the formula may be substituted. Examples of the substituent include a lower alkyl group such as a methyl group and an ethyl group, an aryl group such as a phenyl group, an alkoxyl group having 1 to 8 carbon atoms, a halogen atom such as chlorine, a nitro group, an amino group, and a carboxyl group. be able to. Examples of the heterocycle represented by Z include thiazole, benzthiazole, imidazole, benzimidazole, and oxazole ring. The metal atom represented by M is preferably an alkali metal atom such as sodium ion or potassium ion, and the organic cation is preferably an ammonium ion or a guanidine group.

The amount of the compound represented by the general formula (ST) is not particularly limited, but is preferably in the range of 1 × 10 ^{−6 to} 1 g per mole of total silver including the organic silver salt and the silver halide.

  Similar compounds are disclosed in JP-A-8-314059.

[Vinyl type inhibitor having electron withdrawing group]
In this invention, it is preferable to use together the fog inhibitor which can be represented by the following general formula (CV).

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

  The electron withdrawing group represented by X is a substituent whose Hammett's substituent constant σp can take a positive value. Specifically, a substituted alkyl group (such as halogen-substituted alkyl), a substituted alkenyl group (such as cyanovinyl), a substituted or unsubstituted alkynyl group (such as trifluoromethylacetylenyl, cyanoacetylenyl, formylacetylenyl), Substituted aryl groups (cyanophenyl, etc.), substituted, unsubstituted heterocyclic groups (pyridyl, triazinyl, benzoxazolyl, etc.), halogen atoms, cyano groups, acyl groups (acetyl, trifluoroacetyl, formyl, etc.), thioacyl groups (Thioformyl, thioacetyl etc.), oxalyl group (methyl oxalyl etc.), oxyoxalyl group (ethoxalyl etc.), -S-oxalyl group (ethylthiooxalyl etc.), oxamoyl group (methyl oxamoyl etc.), oxycarbonyl group (ethoxycarbonyl) , Carboxyl, etc.), -S-carbonyl (Such as ethylthiocarbonyl), carbamoyl group, thiocarbamoyl group, sulfonyl group, sulfinyl group, oxysulfonyl group (such as ethoxysulfonyl), -S-sulfonyl group (such as ethylthiosulfonyl), sulfamoyl group, oxysulfinyl group (methoxysulfinyl) Etc.), -S-sulfinyl group (methylthiosulfinyl etc.), sulfinamoyl group, phosphoryl group, nitro group, imino group (imino, N-methylimino, N-phenylimino, N-pyridylimino, N-cyanoimino, N-nitroimino, etc.) N-carbonylimino group (N-acetylimino, N-ethoxycarbonylimino, N-ethoxalylimino, N-formylimino, N-trifluoroacetylimino, N-carbamoylimino, etc.), N-sulfonylimino group (N Methanesulfonylimino, N-trifluoromethanesulfonylimino, N-methoxysulfonylimino, N-sulfamoylimino, etc.), ammonium group, sulfonium group, phosphonium group, pyrylium group, immonium group and the like. A heterocyclic group in which a sulfonium group, a phosphonium group, an immonium group or the like forms a ring is also included. The σp value is preferably 0.2 or more, and more preferably 0.3 or more.

  W includes hydrogen atom, alkyl group (methyl, ethyl, trifluoromethyl, etc.) alkenyl group (vinyl, halogen-substituted vinyl, cyanovinyl, etc.), alkynyl group (acetylenyl, cyanoacetylenyl, etc.), aryl group (phenyl, chlorophenyl) , Nitrophenyl, cyanophenyl, pentafluorophenyl, etc.), heterocyclic groups (pyridyl, pyrimidyl, pyrazinyl, quinoxalinyl, triazinyl, succinimide, tetrazolyl, triazolyl, imidazolyl, benzoxazolyl, etc.) Halogen atom, cyano group, acyl group, thioacyl group, oxalyl group, oxyoxalyl group, -S-oxalyl group, oxamoyl group, oxycarbonyl group, -S-carbonyl group, carbamoyl group, thiocarbamoyl group, sulfonyl , Sulfinyl group, oxysulfonyl group, -S-sulfonyl group, sulfamoyl group, oxysulfinyl group, -S-sulfinyl group, sulfinamoyl group, phosphoryl group, nitro group, imino group, N-carbonylimino group, N-sulfonylimino group , Ammonium group, sulfonium group, phosphonium group, pyrylium group, immonium group and the like.

  W is preferably an aryl group and a heterocyclic group as described above, in addition to an electron-withdrawing group in which Hammett's substituent constant σp can take a positive value.

  X and W may be bonded to each other to form a cyclic structure. Examples of the ring formed by X and W include a saturated or unsaturated carbocyclic or heterocyclic ring which may have a condensed ring, and may be a cyclic ketone. Heterocycles preferably contain at least one atom, more preferably 1-2, of N, O and S.

R ₁ includes a hydroxyl group or an organic or inorganic salt of a hydroxyl group. Specific examples of the alkyl group, alkenyl group, alkynyl group, aryl group and heterocyclic group represented by R ₂ include the examples of the alkyl group, alkenyl group, alkynyl group, aryl group and heterocyclic group exemplified as W. It is done.

In the present invention, X, W and R ₂ may all contain a diffusion-resistant group. The anti-diffusion group is called a ballast group in a photographic coupler or the like, and has a bulky molecular weight so that the added compound does not move in the film of the photosensitive material.

In the present invention, X, W and R ₂ may contain an adsorption promoting group for silver salt. Adsorption promoting groups for silver salts include thioamide groups, aliphatic mercapto groups, aromatic mercapto groups, heterocyclic mercapto groups and benzotriazoles, triazoles, tetrazoles, indazoles, benzimidazoles, imidazoles, benzothiazoles, thiazoles, benzoxazoles, Examples include groups represented by 5- to 6-membered nitrogen-containing heterocycles such as oxazole, thiadiazole, oxadiazole, and triazine.

  In the present invention, it is preferable that at least one of X and W represents a cyano group, or X and W are bonded to each other to form a cyclic structure.

In the present invention, a compound containing a thioether group (—S—) in the substituents represented by X, W and R ₂ is preferred.

  Further, among X and W, those having at least one alkene group represented by the following general formula (CV1) are particularly preferred.

Formula (CV1) -C (R) = C (Y) (Z)
In the above formula, R represents a hydrogen atom or a substituent, and Y and Z each represent a hydrogen atom or a substituent, and at least one of Y and Z represents an electron-withdrawing group.

[Silver ion reducing agent]
In the present invention, US Pat. Nos. 3,589,903, 4,021,249 or British Patent 1,486,148 are used as silver ion reducing agents (sometimes referred to simply as reducing agents). And polyphenol compounds described in JP-A-51-51933, JP-A-50-36110, JP-A-50-116023, JP-A-52-84727 or JP-B-51-35727, such as 2,2′-dihydroxy- Bisnaphthols described in US Pat. No. 3,672,904 such as 1,1′-binaphthyl, 6,6′-dibromo-2,2′-dihydroxy-1,1′-binaphthyl, For example, 4-benzenesulfonamidophenol, 2-benzenesulfonamidophenol, 2,6-dichloro-4-benzenesulfonamidophenol , It can be used sulfonamidophenols or sulfonamidonaphthols, such as described in U.S. Patent No. 3,801,321, such as 4-benzenesulfonamide naphthol.

  However, in the present invention, the silver ion reducing agent is preferably a compound represented by the following general formula (RED).

In the formula, 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. 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.

The chalcogen atom represented by X ₁ is sulfur, selenium or tellurium, preferably a sulfur atom. CHR R ₁ in ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group, a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, the alkyl group substituted or An unsubstituted alkyl group having 1 to 20 carbon atoms is preferred. Specific examples include methyl, ethyl, propyl, butyl, hexyl, heptyl, cycloalkyl, etc. Examples of the alkenyl group include vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl- 3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, cyclohexenyl, etc., aryl groups such as benzene ring, naphthalene ring, etc., heterocyclic groups such as thiophene, furan, imidazole, pyrazole, pyrrole, etc. is there. In particular, a cyclic group such as a cycloalkyl group and a cycloalkenyl group is preferable.

  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.), potassium Boxyl 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 groups (methanesulfonamide, butanesulfonamide, etc.), alkylamino groups (amino, N, N-dimethylamino, N, N-diethylamino, etc.), sulfo groups, phosphono groups, sulfite Group, sulfino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl, etc.), alkylcarbonylaminosulfonyl group (acetamidosulfonyl, methoxyacetamidosulfonyl, etc.), alkynylaminocarbonyl group (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. 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, An ester group, a halogen atom, etc. are mentioned. 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 the group 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, acyloxy groups, Examples include acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, and heterocyclic group.

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 as the substituent, the substituents exemplified in the above R1 can be used.

R ₃ is more preferably an alkyl group having 1 to 10 carbon atoms. In particular, a hydroxyl group as disclosed in the specification of Japanese Patent Application No. 2002-120842, or an alkyl group having a group capable of forming a hydroxyl group by being deprotected, such as a 2-hydroxyethyl group, etc. Is mentioned. Such a reducing agent having an alkyl group should be used alone in order to obtain a high maximum density (Dmax) with a constant applied silver amount, that is, a silver image density with a high silver coverage (covering power, CP). Or it is preferable to use together with another kind of reducing agent.

The most preferred combination of R ₂ and R ₃ is that R ₂ is a tertiary alkyl group (t-butyl, 1-methylcyclohexyl, etc.), R ₃ is an alkyl group, and is a hydroxyl group or deprotected. An alkyl group having a group capable of forming a hydroxyl group as a substituent, for example, a 2-hydroxyethyl group. The 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) , Pyroxy, 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-pyridylaminos 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 group (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. A plurality of R ₄ may be the same or different.

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.

  Specific examples of the compound represented by the general formula (RED) are given below, but the present invention is not limited thereto.

  These compounds represented by the general formula (RED) (bisphenol compounds) can be easily synthesized by a conventionally known method.

  The amount of the silver ion reducing agent used in the photothermographic dry imaging material of the present invention varies depending on the type of organic silver salt, the reducing agent, and other additives. A suitable amount is from 05 mol to 10 mol, preferably from 0.1 mol to 3 mol. Within this range, two or more silver ion reducing agents of the present invention may be used in combination. That is, it is preferable from the viewpoints of obtaining a high-quality and high-CP image that the use of reducing agents having different reactivity due to having different chemical structures is excellent in storage stability.

  In the present invention, it may be preferable that the reducing agent is added to and mixed with a photosensitive emulsion solution composed of photosensitive silver halide and organic silver salt grains and a solvent immediately before coating, because photographic performance fluctuation due to stagnation time is small. is there.

  In the silver salt photothermographic material of the present invention, the general formulas (1) to (4) described in JP-A No. 2003-43614 and JP-A No. 2003-66559 are used as development accelerators used in combination with the above reducing agent. Hydrazine derivatives and phenol derivatives represented by the general formulas (1) to (3) described in Japanese Patent Publication No. 1 are preferably used.

  The oxidation potential of the development accelerator used in the silver salt photothermographic material of the present invention is preferably 0.01 V to 0.4 V lower than the compound represented by the general formula (RED). More preferably, it is 0.01 V to 0.3 V lower than the compound represented by (RED). The development accelerator has an oxidation potential of 0.2 V or more by polarography measurement at the SCE counter electrode in a tetrahydrofuran: Britton / Robinson buffer solution adjusted to pH = 6 = 3: 2 mixed solvent. It is preferably 6 V or less, more preferably 0.3 V or more and 0.55 V or less. The pKa value in a 3: 2 mixed solvent of tetrahydrofuran: water is preferably 3 or more and 12 or less, more preferably 5 or more and 10 or less. Tetrahydrofuran adjusted to pH = 6: Britton-Robinson buffer solution = 3: 2 In a mixed solvent, the oxidation potential measured by polarography at the SCE counter electrode is 0.3 V or more and 0.55 V or less, tetrahydrofuran: water The pKa value in the 3: 2 mixed solvent is particularly preferably 5 or more and 10 or less.

  As the silver ion reducing agent according to the present invention, various reducing agents disclosed in European Patent No. 1,278,101 and Japanese Patent Application Laid-Open No. 2003-15252 can also be used.

  The amount of the silver ion reducing agent used in the photothermographic dry imaging material of the present invention varies depending on the type of organic silver salt, the reducing agent, and other additives. A suitable amount is from 05 mol to 10 mol, preferably from 0.1 mol to 3 mol. Within this range, two or more silver ion reducing agents of the present invention may be used in combination. That is, it is preferable from the viewpoints of obtaining a high-quality and high-CP image that the use of reducing agents having different reactivity due to having different chemical structures is excellent in storage stability.

  In the present invention, it may be preferable that the reducing agent is added to and mixed with a photosensitive emulsion solution composed of photosensitive silver halide and organic silver salt grains and a solvent immediately before coating, because photographic performance fluctuation due to stagnation time is small. is there.

[Chemical sensitization]
The photosensitive silver halide grains according to the present invention can be chemically sensitized. For example, use of a compound that releases a chalcogen such as sulfur, selenium, tellurium, or a noble metal ion that releases a noble metal ion such as gold ion by the methods described in JP-A Nos. 2001-249428 and 2001-249426 Thus, it is possible to form and impart a chemical sensitization center (chemical sensitization nucleus) capable of capturing electrons or holes generated by photoexcitation of photosensitive silver halide grains or spectral sensitizing dyes on the grains. In particular, it is preferably chemically sensitized with an organic sensitizer containing a chalcogen atom.

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

  These organic sensitizers are disclosed in JP-A-60-150046, JP-A-4-109240, JP-A-11-218874, JP-A-11-218875, JP-A-11-218876, JP-A-11-194447, etc. Organic sensitizers having various structures can be used, and among them, 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 It is preferable. In particular, a thiourea derivative having a heterocyclic group and a triphenylphosphine sulfide derivative are preferred.

  As a method for chemical sensitization, techniques according to various chemical sensitization techniques conventionally used in the production of conventional silver halide light-sensitive materials for wet processing can be used (reference: (1) T Edited by H. James “The Theory of the Photographic Process” 4th edition, Macmillan Publishing Co., Ltd., 1977, (2) The Japan Photographic Society, “Basics of Photographic Engineering (Silver Salt Photography), Corona, 1979) In particular, when the silver halide grain emulsion is previously chemically sensitized and then mixed with non-photosensitive organic silver salt grains, it can be chemically sensitized by a conventional method.

The amount of the chalcogen compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, etc., but is 10 ⁻⁸ to 10 ⁻ per mol of silver halide. ² mol is preferred, more preferably 10 ⁻⁷ to 10 ⁻³ mol. The environmental conditions for chemical sensitization are 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. In particular, it may be preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei. The sensitizing conditions in this case are preferably 6 to 11 as pAg, more preferably 7 to 10, pH 4 to 10, more preferably 5 to 8, and the temperature increases at 30 ° C. or lower. It is preferable to give a feeling.

  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. Although the spectral sensitizing dye will be described later, preferred examples of the heteroatom-containing compound having adsorptivity to silver halide include nitrogen-containing heterocyclic compounds described in JP-A-3-24537. In the nitrogen-containing heterocyclic compound, examples of the heterocyclic ring include 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 rings Can be mentioned, 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, tetrahydroxyazaindene, 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 amount of the heterocyclic compound added varies over a wide range depending on the size, composition, and other conditions of the silver halide grains, but the approximate amount is 10 ^-6 per mole of silver halide. It is in the range of ˜1 mol, preferably in the range of 10 ⁻⁴ to 10 ⁻¹ mol.

  The photosensitive silver halide according to the present invention can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, a chloroaurate or an organic gold compound can be used as a gold sensitizer. The gold sensitization technique disclosed in JP-A-11-194447 is useful as a reference.

  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, A borane compound, a silane compound, a polyamine compound, or the like can be used. Further, reduction sensitization can be performed by ripening the emulsion while maintaining the pH at 7 or higher or the pAg at 8.3 or lower.

  In the present invention, the silver halide grains subjected to chemical sensitization may be formed in the presence of an aliphatic carboxylic acid silver salt, or in the absence of the organic silver salt, A mixture of the two may be used.

  In the present invention, when chemical sensitization is performed on the surface of the photosensitive silver halide grains, it is necessary that the chemical sensitization effect substantially disappears after the thermal development process. Here, the chemical sensitization effect substantially disappears when the sensitivity of the imaging material obtained by the chemical sensitization technique is 1.1 when the chemical sensitization is not performed after the thermal development process. Say to decrease below. In order to eliminate the chemical sensitization effect in the heat development process, an oxidant capable of destroying the chemical sensitization center (chemical sensitization nucleus) by an oxidation reaction at the time of heat development, for example, the above-mentioned halogen radical releasing compound, etc. It is necessary to contain an appropriate amount of the above in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the chemical sensitization effect, and the like.

[Spectral sensitization]
The photosensitive silver halide in the present invention is preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. As spectral sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes and the like can be used. For example, JP-A-63-159841, JP-A-60-140335, JP-A-63-231437, JP-A-63-259651, JP-A-63-304242, JP-A-63-15245, US Pat. No. 4,639,414, No. 4,740,455, No. 4,741,966, No. 4,751,175, No. 4,835,096 can be used.

  Useful sensitizing dyes used in the present invention include, for example, Research Disclosure (hereinafter abbreviated as RD) 17643IV-A (December 1978 p.23), RD18431X (August 1978 p.437). It is described in the literature described or cited. In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light sources of various laser imagers and scanners. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

  Useful cyanine dyes are, for example, 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, a sensitizing dye having spectral sensitivity particularly in the infrared can also be used. Examples of infrared spectral sensitizing dyes preferably used include infrared spectral sensitization disclosed in US Pat. Nos. 4,536,473, 4,515,888, 4,959,294, and the like. Examples include dyes.

  In the photothermographic material according to the present invention, a sensitizing dye represented by the following general formula (SD-1) as described in Japanese Patent Application No. 2003-102726 and the following general formula (SD-2) It is preferable to contain at least one selected from sensitizing dyes represented by

In the formula, Y ₁ and Y ₂ each represent an oxygen atom, a sulfur atom, a selenium atom, or a —CH═CH— group, and L _{1 to} L ₉ each represent a methine group. R ₁ and R ₂ each represents an aliphatic group. R ₃ , R ₄ , R ₂₃ and R ₂₄ each represent a lower alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group. W ₁ , W ₂ , W ₃ , and W ₄ are each a hydrogen atom, a substituent, or a nonmetallic atom necessary for bonding between W ₁ and W ₂ , W ₃ and W ₄ to form a condensed ring. Represents a group. Or R ₃ and W ₁ , R ₃ and W ₂ , R ₂₃ and W ₁ , R ₂₃ and W ₂ , R ₄ and W ₃ , R ₄ and W ₄ , R ₂₄ and W ₃ , R ₂₄ and W ₄ Represents a group of non-metallic atoms necessary to form a 5-membered or 6-membered condensed ring by bonding. X ₁ represents an ion necessary for canceling the charge in the molecule, and k 1 represents the number of ions necessary for canceling the charge in the molecule. m1 represents 0 or 1. n1 and n2 each represents 0, 1 or 2. However, n1 and n2 are not 0 at the same time.

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

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

  In the present invention, one kind of spectral sensitizing dye may be used alone, but as described above, it is preferable to use a combination of plural kinds of spectral sensitizing dyes. The combination is often used for the purpose of supersensitization and enlargement or adjustment of the photosensitive wavelength region.

  The emulsion containing the photosensitive silver halide and the aliphatic carboxylic acid silver salt used in the photothermographic material of the present invention substantially contains a dye having no spectral sensitizing action or visible light in addition to the sensitizing dye. The emulsion may contain a substance that does not absorb light and exhibits a supersensitization effect 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. Examples of supersensitizers include heteroaromatic mercapto represented by the following. A compound or a mercapto derivative compound is preferred.

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

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

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

  The heteroaromatic ring includes, for example, a halogen atom (for example, chlorine, bromine, iodine), a hydroxyl group, an amino group, a carboxyl group, and an alkyl group (for example, one or more carbon atoms, preferably 1 to 4 carbon atoms). It may have a substituent selected from the group consisting of those having a carbon atom) and alkoxy groups (for example, those having 1 or more carbon atoms, preferably 1 to 4 carbon atoms).

  In addition to the above supersensitizers, macrocycles having heteroatoms disclosed in JP-A-2001-330918 can also be used as supersensitizers.

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

In the present invention, it is necessary that the spectral sensitizing dye is adsorbed on the surface of the photosensitive silver halide grain to effect spectral sensitization, and that the spectral sensitizing effect should substantially disappear after the thermal development process. It is. Here, the spectral sensitization effect substantially disappears when the sensitivity of the imaging material obtained by a sensitizing dye, supersensitizer, etc. is the sensitivity when spectral sensitization is not performed after the thermal development process. It means to decrease to 1.1 times or less.
In order to eliminate the chemical sensitization effect in the thermal development process, a spectral sensitizing dye that is easily detached from the silver halide grains by heat is used during thermal development or / and the spectral sensitizing dye is destroyed by an oxidation reaction. It is necessary to contain an appropriate amount of an oxidizing agent that can be formed, for example, the above-mentioned halogen radical releasing compound in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the spectral sensitization effect, and the like.

[Silver saving agent]
In the present invention, the photosensitive layer or the non-photosensitive layer can contain a silver saving agent.

  The silver saving agent used in the present invention refers to a compound that can reduce the amount of silver necessary to obtain a certain silver image density. Various action mechanisms of the function of decreasing can be considered, but a compound having a function of improving the covering power of developed silver is preferable. Here, the covering power of developed silver refers to the optical density per unit amount of silver. This silver saving agent can be present in the photosensitive layer, the non-photosensitive layer, or both.

  Preferred examples of the silver saving agent include hydrazine derivatives represented by the following general formula (H), vinyl compounds represented by the following general formula (G), quaternary onium compounds represented by the following general formula (P), and the like. Can be mentioned.

In the general formula [H], A ₀ represents an aliphatic group, aromatic group, heterocyclic group or -G ₀ -D ₀ group which may have a substituent, and B ₀ represents a blocking group. , A ₁ and A ₂ both represent a hydrogen atom, or one represents a hydrogen atom and the other represents an acyl group, a sulfonyl group or an oxalyl group. Here, G ₀ is —CO— group, —COCO— group, —CS— group, —C (═NG ₁ D ₁ ) — group, —SO— group, —SO ₂ — group or —P (O) ( G ₁ D ₁ ) — group, G ₁ represents a simple bond, —O— group, —S— group or —N (D ₁ ) — group, D ₁ represents an aliphatic group, aromatic group, complex When a ring group or a hydrogen atom is represented and a plurality of D ₁ are present in the molecule, they may be the same or different. D ₀ represents a hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, an amino group, an alkoxy group, an aryloxy group, an alkylthio group, or an arylthio group. Preferred D ₀ includes a hydrogen atom, an alkyl group, an alkoxy group, an amino group and the like.

In the general formula [H], the aliphatic group represented by A ₀ is preferably one having 1 to 30 carbon atoms, particularly preferably a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms. Examples thereof include a methyl group, an ethyl group, a t-butyl group, an octyl group, a cyclohexyl group, and a benzyl group. These are further suitable substituents (for example, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a sulfoxy group). Group, sulfonamido group, sulfamoyl group, acylamino group, ureido group, etc.).

In the general formula [H], the aromatic group represented by A ₀ is preferably a monocyclic or condensed aryl group, such as a benzene ring or a naphthalene ring, and the heterocyclic group represented by A ₀ is A heterocyclic ring containing at least one heteroatom selected from nitrogen, sulfur and oxygen atoms in a single ring or a condensed ring is preferred, such as a pyrrolidine ring, an imidazole ring, a tetrahydrofuran ring, a morpholine ring, a pyridine ring, a pyrimidine ring, a quinoline ring, Examples include a thiazole ring, a benzothiazole ring, a thiophene ring, and a furan ring. Aromatic groups A _0, heterocyclic group or -G ₀ -D ₀ group may have a substituent. Particularly preferred as A ₀ are an aryl group and a —G ₀ -D ₀ group.

In the general formula [H], A ₀ preferably contains at least one anti-diffusion group or silver halide adsorption group. As the anti-diffusion group, a ballast group commonly used in an immobile photographic additive such as a coupler is preferable. As the ballast group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, phenyl, which are photographically inactive, are preferable. Group, phenoxy group, alkylphenoxy group and the like, and the total number of carbon atoms in the substituent portion is preferably 8 or more.

  In the general formula [H], examples of the silver halide adsorption promoting group include thiourea, thiourethane group, mercapto group, thioether group, thione group, heterocyclic group, thioamide heterocyclic group, mercapto heterocyclic group, and JP-A-64. And the adsorbing group described in -90439.

In the general formula [H], B ₀ represents a blocking group, preferably a -G ₀ -D ₀ group, and G ₀ represents a -CO- group, a -COCO- group, a -CS- group, -C (= NG ₁ D ₁ ) — group, —SO— group, —SO ₂ — group or —P (O) (G ₁ D ₁ ) — group. Preferred examples of G ₀ include —CO— group and —COCO— group, G ₁ represents a simple bond, —O— group, —S— group or —N (D ₁ ) — group, and D ₁ represents fatty acid. Represents a group, an aromatic group, a heterocyclic group or a hydrogen atom, and when a plurality of D1 are present in the molecule, they may be the same or different. D ₀ represents a hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, an amino group, an alkoxy group, an aryloxy group, an alkylthio group, or an arylthio group, and preferred D ₀ is a hydrogen atom, an alkyl group, an alkoxy group, An amino group etc. are mentioned. A ₁ and A ₂ are both hydrogen atoms, or one is a hydrogen atom and the other is an acyl group (acetyl group, trifluoroacetyl group, benzoyl group, etc.), sulfonyl group (methanesulfonyl group, toluenesulfonyl group, etc.), or oxalyl group (Etoxalyl group, etc.).

  These compounds represented by the general formula [H] can be easily synthesized by known methods. For example, it can be synthesized with reference to US Pat. Nos. 5,464,738 and 5,496,695.

  Other hydrazine derivatives that can be preferably used include compounds H-1 to H-29 described in U.S. Pat. No. 5,545,505 columns 11 to 20, and U.S. Pat. No. 5,464,738 columns 9 to 11. Compounds 1 to 12 described. These hydrazine derivatives can be synthesized by a known method.

  In the general formula (G), X and R are shown in a cis form, but a form in which X and R are trans is also included in the general formula (G). The same applies to the structure display of a specific compound.

  In General Formula (G), X represents an electron-withdrawing group, and W represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, a halogen atom, an acyl group, a thioacyl group, an oxalyl group, an oxy group. Oxalyl, thiooxalyl, oxamoyl, oxycarbonyl, thiocarbonyl, carbamoyl, thiocarbamoyl, sulfonyl, sulfinyl, oxysulfinyl, thiosulfinyl, sulfamoyl, oxysulfinyl, thiosulfinyl, Sulfinamoyl group, phosphoryl group, nitro group, imino group, N-carbonylimino group, N-sulfonylimino group, dicyanoethylene group, ammonium group, sulfonium group, phosphonium group, pyrylium group, immonium group are represented.

  R is a halogen atom, hydroxyl group, alkoxy group, aryloxy group, heterocyclic oxy group, alkenyloxy group, acyloxy group, alkoxycarbonyloxy group, aminocarbonyloxy group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group , An alkenylthio group, an acylthio group, an alkoxycarbonylthio group, an aminocarbonylthio group, an organic or inorganic salt of a hydroxyl group or a mercapto group (for example, sodium salt, potassium salt, silver salt, etc.), amino group, alkylamino group, Cyclic amino group (for example, pyrrolidino group), acylamino group, oxycarbonylamino group, heterocyclic group (5-6 membered nitrogen-containing heterocycle such as benztriazolyl group, imidazolyl group, triazolyl group, tetrazolyl group, etc.), Ureido group, sulfonamido It represents a group. X and W, X and R may be bonded to each other to form a cyclic structure. Examples of the ring formed by X and W include pyrazolone, pyrazolidinone, cyclopentanedione, β-ketolactone, β-ketolactam and the like.

  The general formula (G) will be further described. The electron-withdrawing group represented by X is a substituent whose substituent constant σp can take a positive value. Specifically, a substituted alkyl group (such as halogen-substituted alkyl), a substituted alkenyl group (such as cyanovinyl), a substituted / unsubstituted alkynyl group (such as trifluoromethylacetylenyl, cyanoacetylenyl), a substituted aryl group (such as cyano) Phenyl, etc.), substituted / unsubstituted heterocyclic groups (pyridyl, triazinyl, benzoxazolyl, etc.), halogen atoms, cyano groups, acyl groups (acetyl, trifluoroacetyl, formyl, etc.), thioacetyl groups (thioacetyl, thioformyl, etc.) ), Oxalyl group (such as methyloxalyl), oxyoxalyl group (such as etoxalyl), thiooxalyl group (such as ethylthiooxalyl), oxamoyl group (such as methyloxamoyl), oxycarbonyl group (such as ethoxycarbonyl), carboxyl group, thiol Carbonyl group (ethylthiocarboni ), Carbamoyl group, thiocarbamoyl group, sulfonyl group, sulfinyl group, oxysulfonyl group (ethoxysulfonyl etc.), thiosulfonyl group (ethylthiosulfonyl etc.), sulfamoyl group, oxysulfinyl group (methoxysulfinyl etc.), thiosulfinyl group (Such as methylthiosulfinyl), sulfinamoyl group, phosphoryl group, nitro group, imino group, N-carbonylimino group (N-acetylimino etc.), N-sulfonylimino group (N-methanesulfonylimino etc.), dicyanoethylene group, ammonium Group, sulfonium group, phosphonium group, pyrylium group, immonium group, and the like include a heterocyclic group in which an ammonium group, sulfonium group, phosphonium group, immonium group and the like form a ring. A substituent having a σp value of 0.30 or more is particularly preferable.

  Examples of the alkyl group represented by W include methyl, ethyl, trifluoromethyl, etc., examples of the alkenyl group include vinyl, halogen-substituted vinyl, cyanovinyl, etc., examples of the alkynyl group include acetylenyl, cyanoacetylenyl, and the like as the aryl group. Nitrophenyl, cyanophenyl, pentafluorophenyl and the like, and examples of the heterocyclic group include pyridyl, pyrimidyl, triazinyl, succinimide, tetrazolyl, triazolyl, imidazolyl and benzoxazolyl. W is preferably an electron-withdrawing group having a positive σp value, and more preferably 0.30 or more.

  Among the substituents of R, a hydroxyl group, a mercapto group, an alkoxy group, an alkylthio group, a halogen atom, an organic or inorganic salt of a hydroxyl group or a mercapto group, and a heterocyclic group are preferable, and a hydroxyl group, An organic or inorganic salt of an alkoxy group, a hydroxyl group or a mercapto group, or a heterocyclic group is exemplified, and an organic or inorganic salt of a hydroxyl group, a hydroxyl group or a mercapto group is particularly preferred.

  Of the substituents X and W, those having a thioether bond in the substituent are preferred.

In the general formula (P), Q ₃ represents a nitrogen atom or a phosphorus atom, R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom or a substituent, and X ⁻ represents an anion. R _{1 to} R ₄ may be connected to each other to form a ring.

Examples of the substituent represented by R _{1 to} R ₄ include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a cyclohexyl group), an alkenyl group (for example, an allyl group, a butenyl group). Group), alkynyl group (eg, propargyl group, butynyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), heterocyclic group (eg, piperidinyl group, piperazinyl group, morpholinyl group, pyridyl group, furyl group) , Thienyl group, tetrahydrofuryl group, tetrahydrothienyl group, sulfolanyl group, etc.), amino group and the like.

Examples of the ring that R _{1 to} R ₄ can be formed by connecting to each other include a piperidine ring, a morpholine ring, a piperazine ring, a quinuclidine ring, a pyridine ring, a pyrrole ring, an imidazole ring, a triazole ring, and a tetrazole ring.

The group represented by R _{1 to} R ₄ may have a substituent such as a hydroxyl group, an alkoxy group, an aryloxy group, a carboxyl group, a sulfo group, an alkyl group, or an aryl group. As R < ₁ > -R < ₄ >, a hydrogen atom and an alkyl group are preferable.

Examples of the anion represented by X ⁻ include inorganic and organic anions such as halogen ions, sulfate ions, nitrate ions, acetate ions, and p-toluenesulfonate ions.

The quaternary onium compound can be easily synthesized in accordance with a known method. For example, the tetrazolium compound can be synthesized by referring to Chemical Reviews vol. 55 p. The method described in 335-483 can be referred to. The amount of the silver saving agent added is in the range of 10 ⁻⁵ to 1 mol, preferably 10 ^{−4 to} 5 × 10 ⁻¹ mol, per mol of the aliphatic carboxylic acid silver salt.

  In the present invention, it is also preferred that at least one silver saving agent is a silane compound. In the present invention, the silane compound used as a silver saving agent is an alkoxysilane compound having two or more primary or secondary amino groups or a salt thereof as disclosed in Japanese Patent Application Laid-Open No. 2003-5324. Is preferred.

  As a silver saving agent, when an alkoxysilane compound or a salt thereof, or a Schiff base is added to the image forming layer, it is preferably added in a range of usually 0.00001 to 0.05 mol with respect to 1 mol of silver. . The same category applies when both an alkoxysilane compound or a salt thereof and a Schiff base are added to the image forming layer.

〔binder〕
The binder suitable for the photothermographic material of the present invention is transparent or translucent and generally colorless, and is a natural polymer synthetic resin, polymer and copolymer, or other media for forming a film such as gelatin, gum arabic, poly (vinyl). Alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (Styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), Poly (urethane) , Phenoxy resins, poly (vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, and polyamides. It may be hydrophilic or non-hydrophilic.

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

Such a binder is used in an effective range to function as a binder. The effective range can be easily determined by one skilled in the art. For example, as an index for holding at least an aliphatic carboxylic acid silver salt in the photosensitive layer, the ratio of the binder to the aliphatic carboxylic acid silver salt is 15: 1 to 1: 2, particularly 8: 1 to 1: 1. The range of is preferable. That is, it is preferable amount of the binder in the photosensitive layer is 1.5~6g / m ^2. More preferably, it is 1.7-5 g / m < ² >. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.

  In the present invention, the heat transition temperature after development at a temperature of 100 ° C. or higher is preferably 46 ° C. or higher and 200 ° C. or lower, more preferably 70 ° C. or higher and 105 ° C. or lower. The heat transition temperature referred to in the present invention is a value indicated by the VICAT softening point or ring-and-ball method, and is a differential scanning calorimeter (DSC), for example, EXSTAR 6000 (manufactured by Seiko Denshi), DSC220C (manufactured by Seiko Denshi Kogyo). DSC-7 (manufactured by Perkin Elmer) or the like is used to indicate the endothermic peak when the thermally developed photosensitive layer is isolated and measured. In general, a polymer compound has a glass transition point Tg, but in a photothermographic material, a large endothermic peak appears at a position lower than the Tg value of the binder resin used in the photosensitive layer. By setting the thermal transition temperature to 46 ° C. or higher and 200 ° C. or lower, not only the fastness of the formed coating film is increased, but also photographic performance such as sensitivity, maximum density and image storage stability can be greatly improved. Become.

  The glass transition temperature (Tg) was obtained by the method described in “Polymer Handbook” pages III-139 to III-179 (1966, Wiley and Sun, Inc.) by Brandrup et al. Tg in the case of a polymer resin is obtained by the following formula.

Tg (copolymer) (° C.) = V1Tg1 + v2Tg2 +... + VnTgn
[Wherein, v1, v2... Vn represents the mass fraction of monomers in the copolymer, and Tg1, Tg2... Tgn represents a single weight obtained from each monomer in the copolymer. Represents the Tg (° C.) of the coalescence. ]
The accuracy of Tg calculated according to the above equation is ± 5 ° C.

  In the photothermographic material of the present invention, a conventionally known polymer compound is used as a binder contained in a photosensitive layer containing an aliphatic carboxylic acid silver salt, photosensitive silver halide grains, a reducing agent, etc. on a support. Can be used. The Tg is 70 to 105 ° C., the number average molecular weight is 1,000 to 1,000,000, preferably 10,000 to 500,000, and the degree of polymerization is about 50 to 1,000. Examples of such include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, There are compounds made of a polymer or copolymer containing an ethylenically unsaturated monomer such as vinyl ether as a constituent unit, polyurethane resins, and various rubber resins.

  Moreover, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone resin, epoxy-polyamide resin, polyester resin, and the like can be given. These resins are described in detail in “Plastic Handbook” issued by Asakura Shoten. There is no restriction | limiting in particular in these high molecular compounds, A homopolymer or a copolymer may be sufficient if the glass transition temperature (Tg) of the induced | guided | derived polymer exists in the range of 70-105 degreeC.

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

  In addition, the following monomers can be used. Specific examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl chloroacetate, vinyl methoxyacetate, vinyl phenyl acetate, vinyl benzoate, vinyl salicylate. N-substituted acrylamides, N-substituted methacrylamides and acrylamides, methacrylamides: N-substituents include methyl, ethyl, propyl, butyl, tert-butyl, cyclohexyl, benzyl, hydroxymethyl, methoxyethyl, dimethyl Aminoethyl, phenyl, dimethyl, diethyl, β-cyanoethyl, N- (2-acetoacetoxyethyl), diacetone and the like; olefins: for example, dicyclopentadiene, ethylene, propylene, 1- Ten, 1-pentene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, 2,3-dimethylbutadiene, etc .; styrenes: for example, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, tert-butylstyrene , Chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl benzoic acid methyl ester, etc .; vinyl ethers: for example, methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethyl vinyl ether N-substituted maleimides: As N-substituent, methyl, ethyl, propyl, butyl, tert-butyl, cyclohexyl , Benzyl, n-dodecyl, phenyl, 2-methylphenyl, 2,6-diethylphenyl, 2-chlorophenyl, etc .; others include butyl crotonate, hexyl crotonate, dimethyl itaconate, dibutyl itaconate , Diethyl maleate, dimethyl maleate, dibutyl maleate, diethyl fumarate, dimethyl fumarate, dibutyl fumarate, methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone, glycidyl acrylate, glycidyl methacrylate, N-vinyl oxazolidone, N -Vinylpyrrolidone, acrylonitrile, methacrylonitrile, methylenemalonnitrile, vinylidene chloride and the like can be mentioned.

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

  As the polymer compound having an acetal group, a compound represented by the following general formula (V) is particularly preferable.

[Wherein, R ₁ represents an alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group, but is preferably a group other than an aryl group. R ₂ represents an unsubstituted alkyl group, a substituted alkyl group, an unsubstituted aryl group, a substituted aryl group, —COR ₃ or —CONHR ₃ . R ₃ has the same meaning as R ₁ . ]
The unsubstituted alkyl group represented by R ₁ , R ₂ , or R ₃ is preferably an alkyl group having 1 to 20 carbon atoms, particularly preferably 1 to 6 carbon atoms. These may be linear or branched, and preferably a linear alkyl group. Examples of such unsubstituted alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-amyl, t-amyl, n -Hexyl group, cyclohexyl group, n-heptyl group, n-octyl group, t-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-octadecyl group, etc. Is particularly preferably a methyl group or a propyl group.

  As an unsubstituted aryl group, a C6-C20 thing is preferable, for example, a phenyl group, a naphthyl group, etc. are mentioned. Examples of the group that can be substituted with the above alkyl group or aryl group include an alkyl group (for example, a methyl group, an n-propyl group, a t-amyl group, a t-octyl group, an n-nonyl group, a dodecyl group), an aryl group. (For example, phenyl group), nitro group, hydroxyl group, cyano group, sulfo group, alkoxy group (for example, methoxy group), aryloxy group (for example, phenoxy group), acyloxy group (for example, acetoxy group), Acylamino group (for example, acetylamino group), sulfonamide group (for example, methanesulfonamide group), sulfamoyl group (for example, methylsulfamoyl group), halogen atom (for example, fluorine atom, chlorine atom, bromine atom) ), Carboxy group, carbamoyl group (for example, methylcarbamoyl group, etc.), alkoxycarbonyl group (for example, metho Shiruboniru group), a sulfonyl group (e.g., methyl sulfonyl group). When there are two or more substituents, they may be the same or different. The total carbon number of the substituted alkyl group is preferably 1-20, and the total carbon number of the substituted aryl group is preferably 6-20.

The R _2, -COR ₃ (R ₃ is an alkyl group or an aryl group), - CONHR ₃ (R ₃ is an aryl group). a, b, and c are values indicating the mass of each repeating unit in mol (mol)%, a is 40 to 86 mol%, b is 0 to 30 mol%, and c is in the range of 0 to 60 mol%. A + b + c = 100 mol%, particularly preferably a is in the range of 50 to 86 mol%, b is 5 to 25 mol%, and c is 0 to 40 mol%. Each repeating unit having each composition ratio of a, b, and c may be composed of only the same one or may be composed of different ones.

As the polyurethane resin that can be used in the present invention, those having a known structure such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the polyurethane shown here, if _{necessary, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, -O-P = O (OM) 2, (M is hydrogen Represents an atom or an alkali metal base), —N (R ₄ ) ₂ , —N ⁺ (R ₄ ) ₃ (R ₄ represents a hydrocarbon group, and a plurality of R ₄ may be the same or different); It is preferable to use one in which at least one polar group selected from an epoxy group, —SH, —CN and the like is introduced by copolymerization or addition reaction. The amount of such a polar group is 10 ⁻¹ to 10 ⁻⁸ mol / g, preferably 10 ⁻² to 10 ⁻⁶ mol / g. In addition to these polar groups, it is preferable to have at least one OH group in total at least one at the polyurethane molecule end. Since OH groups are cross-linked with polyisocyanate which is a curing agent to form a three-dimensional network structure, it is more preferable that the OH groups are contained in the molecule. In particular, it is preferable that the OH group is at the molecular end because the reactivity with the curing agent is high. The polyurethane preferably has 3 or more OH groups at the molecular terminals, and particularly preferably 4 or more. When polyurethane is used, the glass transition temperature is preferably 70 to 105 ° C., the elongation at break is 100 to 2000%, and the stress at break is preferably 0.5 to 100 N / mm ² .

  In the present invention, the polymer compound represented by the general formula (V) is synthesized by a general synthesis method described in “vinyl acetate resin” edited by Ichiro Sakurada (Polymer Chemistry Publishing Society, 1962) and the like. Can do.

  Other polymer compounds (polymers) listed in Table 1 were synthesized in the same manner.

  These polymer compounds may be used alone as a binder, or two or more kinds may be blended and used. In the photosensitive silver salt-containing layer (preferably photosensitive layer) of the present invention, the above polymer is used as a main binder. The main binder as used herein refers to “a state in which the polymer occupies 50% by mass or more of the total binder of the photosensitive silver salt-containing layer”. Therefore, other polymers may be blended and used within a range of less than 50% by weight of the total binder. These polymers are not particularly limited as long as the polymers of the present invention are soluble. More preferably, polyvinyl acetate, a polyacrylic resin, a urethane resin, etc. are mentioned.

  Below, the structure of the high molecular compound preferably used for this invention is shown. In the table, Tg is a value measured by a differential scanning calorimeter (DSC) manufactured by Seiko Instruments Inc.

  In Table 1, P-9 is a polyvinyl butyral resin B-79 manufactured by Solusia.

  In the present invention, it is known that the use of a crosslinking agent with respect to the binder improves the film formation and reduces development unevenness. However, it prevents fogging during storage and produces printed silver after development. There is also an inhibitory effect.

  Examples of the crosslinking agent used in the present invention include various crosslinking agents conventionally used for silver halide photographic light-sensitive materials, such as aldehyde-based, epoxy-based, and ethyleneimine described in JP-A-50-96216. , Vinyl sulfone, sulfonic acid ester, acryloyl, carbodiimide, and silane compound crosslinking agents may be used, but the following isocyanate compounds, silane compounds, epoxy compounds, or acid anhydrides are preferred.

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

General formula [IC] X = C = N-L- (N = C = X) _v
In the formula, v is 1 or 2, L is an alkyl group, an alkenyl group, an aryl group or an alkylaryl group, a v + 1 valent linking group, and X is an oxygen or sulfur atom.

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

  The isocyanate-based crosslinking agent includes isocyanates having at least two isocyanate groups and adducts thereof (adducts), and more specifically, aliphatic diisocyanates and 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 with these isocyanates Examples include adducts with polyalcohols.

  As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used.

  Note that the adduct body of isocyanate and polyalcohol has particularly high ability to improve interlayer adhesion, and prevent layer peeling, image shift, and bubble generation. Such isocyanate may be placed in any part of the photothermographic material. For example, the photosensitivity of the support 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 on the layer side, 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 in the present invention is in the range of 0.001 to 2 mol, preferably 0.005 to 0.5 mol, with respect to 1 mol of silver.

  The isocyanate compound and thioisocyanate compound that can be contained in the present invention are preferably compounds that function as the above-mentioned crosslinking agent. However, in the above general formula, v is zero (0), that is, the functional group is one. Even if it is a compound which has only, a good result is obtained.

  Examples of the silane compound that can be used as a crosslinking agent in the present invention include compounds represented by general formula (1) or general formula (2) described in JP-A-2002-22203.

In these general formulas, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are each a linear, branched or cyclic carbon group having 1 to 30 carbon atoms which may be substituted. Alkyl group (methyl group, ethyl group, butyl group, octyl group, dodecyl group, cycloalkyl group, etc.), alkenyl group (propenyl group, butenyl group, nonenyl group, etc.), alkynyl group (acetylene group, bisacetylene group, phenylacetylene) Group), aryl group or heterocyclic group (phenyl group, naphthyl group, tetrahydropyran group, pyridyl group, furyl group, thiophenyl group, imidazole group, thiazole group, thiadiazole group, oxadiazole group, etc.), substituent As an electron-withdrawing substituent or an electron-donating substituent.

_{R 1, R 2, R 3} , R 4, preferably R _5, R _6, at least 1 Tsuga耐diffusion group or adsorptive group substituents selected from R ₇ and R _8, especially R ₂ It is preferably a diffusion-resistant group or an adsorptive group.

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

  The epoxy compound that can be used as the crosslinking agent is not particularly limited as long as it has one or more epoxy groups and the number of epoxy groups, molecular weight, and the like. The epoxy group is preferably contained in the molecule as a glycidyl group via an ether bond or an imino bond. Moreover, any of a monomer, an oligomer, a polymer, etc. may be sufficient as an epoxy compound, and the number of the epoxy groups which exist in a molecule | numerator is about 1-10 normally, Preferably it is 2-4. When the epoxy compound is a polymer, it may be a homopolymer or a copolymer, and the particularly preferred range of the number average molecular weight Mn is about 2000 to 20000.

  As an epoxy compound, the compound represented by the following general formula (EP) is preferable.

In the general formula (EP), the substituent of the alkylene group represented by R is preferably a group selected from a halogen atom, a hydroxyl group, a hydroxyalkyl group, or an amino group. The linking group represented by R preferably has an amide linking moiety, an ether linking moiety, or a thioether linking moiety. -SO ₂ The divalent linking group represented by _{X -, - SO 2 NH -} , - S -, - O-, or -NR ₁ - is preferred. Here, R ₁ is a monovalent group and is preferably an electron withdrawing group.

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

  The epoxy compound can be added to any layer on the photosensitive layer side of the support, such as a photosensitive layer, a surface protective layer, an intermediate layer, an antihalation layer, an undercoat layer, and one or two of these layers. It can be added to the above. Moreover, it can add to the arbitrary layer on the opposite side to the photosensitive layer of a support body collectively. In addition, any layer may be sufficient in the type of photosensitive material in which a photosensitive layer exists on both surfaces.

  An acid anhydride is a compound having at least one acid anhydride group represented by the following structural formula.

-CO-O-CO-
The acid anhydride is not particularly limited as long as it has one or more acid anhydride groups, and the number, molecular weight, and the like of the acid anhydride groups are not limited, but a compound represented by the following general formula (SA) is preferable.

  In the general formula (SA), Z represents an atomic group necessary for forming a monocyclic or polycyclic system. These ring systems may be unsubstituted or substituted. Examples of substituents include alkyl groups (eg, methyl, ethyl, hexyl), alkoxy groups (eg, methoxy, ethoxy, octyloxy), aryl groups (eg, phenyl, naphthyl, tolyl), hydroxyl groups, aryloxy groups (Eg, phenoxy), alkylthio group (eg, methylthio, butylthio), arylthio group (eg, phenylthio), acyl group (eg, acetyl, propionyl, butyryl), sulfonyl group (eg, methylsulfonyl, phenylsulfonyl), acylamino group Sulfonylamino group, acyloxy group (for example, acetoxy, benzoxy), carboxyl group, cyano group, sulfo group, and amino group. As the substituent, those not containing a halogen atom are preferable.

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

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

(Color adjustment)
Next, the color tone of an image obtained by heat developing the imaging 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 of a recorded image. Here, a cool image tone is a pure black tone or a bluish black tone with a black image, and a warm image tone is a black tone with a brown tone. However, in order to allow a more precise quantitative discussion, the following explanation is based on the expression recommended by the International Commission on Illumination (CIE).

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 uses the color coordinates a ^* and b ^* of the L ^* a ^* b ^* color space, which is a color space having a perceptually almost uniform rate recommended by the International Commission on Illumination (CIE) in 1976. The following formula is used.

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 silver salt photothermographic imaging material according to the present invention preferably has a hue angle hab range of 180 degrees <hab <270 degrees, more preferably Was found to be 200 degrees <hab <270 degrees, most preferably 220 degrees <hab <260 degrees. This is disclosed in Japanese Patent Application Laid-Open No. 2002-6463.

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

However, with regard to the silver salt photothermographic imaging material according to the present invention, as a result of further earnest studies, the horizontal axis is u in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space. ^* or a ^*, vertical axis v ^* or b ^* and the on the graph, u ^* at various photographic density, v ^* or a ^*, and b ^* are plotted when creating a linear regression line, its linear It was found that by adjusting the regression line to a specific range, it has a diagnostic ability equal to or higher than that of conventional wet silver halide photosensitive materials. In the following, preferred condition ranges will be described.

1) CIE 1976 (L ^* u ^* v ^*) was measured for the optical density of 0.5, 1.0, 1.5 and the lowest optical density of the silver image obtained after heat development processing of the photothermographic imaging material ^. ) Determination coefficient (multiple determination) R ^{2 of} the linear regression line created by arranging u ^* and v ^* at the above optical densities on two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^*. Is preferably 0.998 or more and 1.000 or less.

Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 or more and 5 or less, and the slope (v ^* / u ^* ) is 0.7 or more and 2.5 or less.

2) In addition, the optical density of the imaging 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 is defined as a ^*. The determination coefficient (multiple determination) R ^{2 of} the linear regression line created by arranging a ^* and b ^* at the above optical densities on two-dimensional coordinates with the vertical axis b ^* is 0.998 or more and 1.000 or less. It is preferable that

Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 or more and 5 or less, and the slope (b ^* / a ^* ) is 0.7 or more and 2.5 or less.

An example of a method for creating the above-described linear regression line, that is, a method for measuring u ^* , v ^* and a ^* , 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 (example: CM-3600d; manufactured by Minolta Co., Ltd.) to calculate u ^* , v ^* or a ^* , b ^* . The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 °, and the measurement is performed in the transmission measurement mode. Plot u ^* , v ^*, 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 determine coefficient (multiple determination) R ² Find the 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 shape is adjusted by adjusting the addition amount of the above-described toning agent, developer, silver halide grains, and compounds such as aliphatic carboxylic acid silver which are directly and indirectly involved in the development reaction process. Optimized and preferred 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 are RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, and 4,021,249. Is disclosed.

  In addition to such a toning agent, it is preferable to adjust the color tone using a coupler disclosed in JP-A-11-288057, EP11334611A2, etc. and a leuco dye described in detail below.

  Further, by using silver halide grains that are converted into the internal latent image type after heat development according to the present invention, it is possible to unexpectedly prevent color tone fluctuations during storage of silver images.

[Leuco dye]
A leuco dye is used in the photothermographic material of the present invention.

  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, indoalilin leuco dyes, acrylated azine leuco dyes, phenoxazine leuco dyes, phenodiazine leuco dyes. And phenothiazine leuco dye. Also useful are U.S. Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4 No. 4,022,617, No. 4,123,282, No. 4,368,247, No. 4,461,681, and JP-A-50-36110, No. 59-206931, JP-A-5-204087. No. 11-231460, JP-A Nos. 2002-169249, 2002-236334, and the like.

  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, the color tone is excessively yellowish with the use of a highly active reducing agent, or the image is excessively high at a high density portion of 2.0 or more by using fine silver halide. It is preferable to use a leuco dye that develops in cyan to prevent redness, but a yellow leuco dye and other leuco dyes that develop in cyan are also used for fine-tuning the color tone. It is preferable to do this.

  The color density is preferably adjusted appropriately in relation to the color tone of the developed silver itself. In the present invention, the sum of the maximum densities at the absorption maximum wavelength of the dye image formed by the leuco dye is usually 0.01 or more and 0.30 or less, preferably 0.02 or more and 0.20 or less, particularly preferably 0.02 or more. It is preferable to adjust the color tone so that the color is developed so as to have a value of 0.10 or less and an image having a preferable color tone range described later is obtained.

  The addition amount of the 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. It is.

  The addition method of the leuco dye can be added by the same method as the addition method of the reducing agent represented by the general formula (RED), and any method such as a solution form, an emulsified dispersion form, a solid fine particle dispersion form, etc. In the coating solution, it may be contained in the photosensitive material.

  The leuco dye is preferably contained in the image forming layer containing the organic silver salt, but 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. It 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.

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

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

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

  Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

(Standard deviation of particle size) / (Average value of particle size) × 100
The method for adding the matting agent according to the present invention may be a method in which the matting agent is dispersed and applied in advance in the coating solution, or a method in which the matting agent is sprayed after the coating solution is applied and before drying is completed. May be. When a plurality of types of matting agents are added, both methods may be used in combination.

[Fluorosurfactant]
In the imaging material according to the present invention, it is preferable to use fluorine-based surfactants represented by the following general formulas (SA-1) to (SA-3).

Formula (SA-1) (Rf-L) _p -Y- (A) _q
Formula _{(SA-2) LiO 3 S-} (CF 2) n -SO 3 Li
Formula _{(SA-3) MO 3 S-} (CF 2) n -SO 3 M
(In the formula, M represents a hydrogen atom, a sodium atom, a potassium atom, or an ammonium group, and n represents a positive integer, n = 1 to 6 and 8 when M = H, and n when M = Na. = 4, when M = K, n = 1 to 6, and when M = ammonium group, n = 1 to 8.)
In the general formula (SA-1), Rf represents a substituent containing a fluorine atom. Examples of the substituent containing a fluorine atom include an alkyl group having 1 to 25 carbon atoms (for example, a methyl group, an ethyl group, and the like). Group, butyl group, octyl group, dodecyl group, octadecyl group and the like) or alkenyl group (for example, propenyl group, butenyl group, nonenyl group, dodecenyl group, etc.) and the like.

  L 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, methylene group, ethylene group, butylene group, etc.), alkylene Oxy 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, oxy Ethyleneoxy 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 base thereof, for example, a carboxylic acid group or a base thereof (sodium salt, potassium salt and lithium salt), a sulfonic acid group or a base thereof (sodium salt, potassium salt and lithium salt) and a phosphoric acid group or Examples thereof include sodium base and potassium salt.

  Y represents a trivalent or tetravalent linking group having no fluorine atom. For example, an atom composed of a trivalent or tetravalent linking group having no fluorine atom and centering on a carbon atom or a nitrogen atom. Groups. p represents an integer of 1 to 3, and q represents an integer of 2 to 3.

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

  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.

  N in general formula (SA-2) represents the integer of 1-4.

  In General Formula (SA-3), M represents a hydrogen atom, a sodium atom, a potassium atom, or an ammonium group, n represents a positive integer, and when M = H, n = 1 to 6 and 8; When n = Na, n = 4, when M = K, n = 1-6, and when M = ammonium group, n = 1-8.

  As a method of adding the fluorine-based surfactant represented by the general formulas (SA1) to (SA-3) 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 of 1 μm or less can be dispersed in water or an organic solvent by sand mill dispersion, jet mill dispersion, ultrasonic dispersion or homogenizer dispersion, and added. Many techniques for fine particle dispersion are disclosed, but they can be dispersed according to these techniques. The fluorosurfactant is preferably added to the outermost protective layer.

The amount of the fluorosurfactant added is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ^2, particularly preferably 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol. If the range is less than the former range, charging characteristics cannot be obtained.

  Note that surfactants represented by the general formula (SA-1), the general formula (SA-2), and the general formula (SA-3) are disclosed in JP-A-2003-57786, Japanese Patent Application No. 2002-178386, and JP-A-2002-237882, respectively. It is disclosed in the specification.

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

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

  The photothermographic material of the present invention has at least one photosensitive layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer. For example, a protective layer is provided on the photosensitive layer for the purpose of protecting the photosensitive layer, and on the opposite side of the support to prevent sticking between the photosensitive materials or in the photosensitive material roll. A layer is preferably provided. Binders used in these protective layers and backcoat layers have a glass transition point higher than that of the heat-developable layer, and polymers such as scratches and deformations, such as cellulose acetate and cellulose acetate butyrate, are the above-mentioned binders. It is chosen from among them. For gradation adjustment and the like, in the present invention, the photosensitive layer is preferably composed of two or more layers. For example, two or more photosensitive layers may be provided on one side of the support, or the support. One or more layers may be installed on both sides.

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

  As the dye used, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the photosensitive material.

  For example, when the photothermographic material of the present invention is used as an image recording material by infrared light, a squarylium dye having a thiopyrylium nucleus as disclosed in Japanese Patent Application No. 11-255557 (in this specification, a thiopyridium dye). A squarylium dye having a pyrylium nucleus (referred to herein as a pyrylium squarylium dye), a thiopyrylium croconium dye similar to a squarylium dye, or a pyrylium croconium dye. preferable.

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

  As the dye, a compound described in JP-A-8-201959 is also preferable.

[Layer structure and coating conditions]
The photothermographic material of the present invention may be formed by preparing a coating solution in which the above-described constituent materials are dissolved or dispersed in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment. preferable. Here, "multiple simultaneous multi-layer coating" means that a coating solution for each constituent layer (for example, a photosensitive layer and a protective layer) is prepared, and each layer is repeatedly coated and dried when it is coated on a support. Rather, it means that each constituent layer can be formed in such a state that a multilayer coating and drying process can be performed simultaneously.

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

In the present invention, the silver coating amount is preferably 0.5 g / m ² or more and 2.0 g / m ² or less, more preferably 1.0 g / m ² or more and 1.5 g / m ² or less.

In the present invention, the silver equivalent of silver halide grains having a grain size of 0.030 μm or more and 0.055 μm or less in the silver halide grain emulsion has a silver coating amount of 0.5 g / m ² or more and 1.5 g. It is preferably 3% or more and 15% or less in the range of / m ² or less.

  Among the applied silver amount, those derived from silver halide preferably occupy 2 to 18%, more preferably 3 to 15%, based on the total silver amount.

In the present invention, the coating density of silver halide grains of 0.01 μm or more (equivalent particle diameter equivalent to 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 aliphatic carboxylic acid silver salt of the present invention is 10 ⁻¹⁷ g or more, 10 ⁻¹⁵ g or less, more preferably 10 μg per silver halide grain of 0.01 μm or more (equivalent particle diameter equivalent to sphere). ^-16 g or more and 10 ^-14 g or less is preferable.

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

[Exposure conditions]
In the exposure of the photothermographic material of the present invention, it is desirable to use an appropriate light source for the color sensitivity imparted to the photosensitive material. For example, when the photosensitive material is sensitive to infrared light, it can be applied to any light source as long as it is in the infrared light range. However, the laser power is high and the photosensitive material can be transparent. In view of the above, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

  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 exposure surface of the photosensitive material and the scanning laser beam is not substantially perpendicular.

  Here, “substantially not perpendicular” means that the angle closest to the vertical during laser scanning is preferably 55 degrees or more and 88 degrees or less, more preferably 60 degrees or more and 86 degrees or less, and further Preferably it is 65 degrees or more and 84 degrees or less, Most preferably, it is 70 degrees or more and 82 degrees or less.

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

  As a second method, it is preferable to perform exposure using a laser scanning exposure machine that emits scanning laser light that is a vertical multi. Compared with a longitudinal single mode scanning laser beam, image quality degradation such as occurrence of interference fringe-like unevenness is reduced.

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

In the image recording methods of the first and second aspects described above, the laser used for the scanning exposure is generally well-known solid laser such as ruby laser, YAG laser, glass laser; HeNe laser, Ar ion. Gas laser such as laser, Kr ion laser, CO ₂ laser, CO laser, HeCd laser, N ₂ laser, excimer laser; InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP ₂ laser, GaSb laser, etc. Semiconductor lasers; chemical lasers, dye lasers, and the like can be selected and used in a timely manner, but among these, it is preferable to use a semiconductor laser having a wavelength of 600 to 1200 nm from the viewpoint of maintenance and the size of the light source. In a laser used in a laser imager or a laser image setter, the beam spot diameter on the exposed surface of the material when scanned by a photothermographic material is generally 5 to 75 μm as the minor axis diameter, and the major axis diameter. The laser beam scanning speed can be set to an optimum value for each photosensitive material depending on the sensitivity and laser power at the laser oscillation wavelength unique to the photothermographic material.

[Development conditions]
In the present invention, the development conditions vary depending on the equipment, apparatus or means used, but typically involve heating the photothermographic material exposed imagewise at a suitable high temperature. The latent image obtained after exposure is developed by heating the photothermographic material at a moderately high temperature (for example, about 100 to 200 ° C.) for a sufficient time (generally about 1 second to about 2 minutes). Can do. When the heating temperature is 100 ° C. or lower, sufficient image density cannot be obtained in a short time, and when the heating temperature is 200 ° C. or higher, the binder melts, and not only the image itself, such as transfer to a roller, but also adversely affects the transportability and developing machine. Effect. By heating, a silver image is generated by an oxidation-reduction reaction between silver ions (which function as an oxidizing agent) supplied from an aliphatic carboxylic acid silver salt or the like and a reducing agent. This reaction process proceeds without any supply of treatment liquid such as water from the outside.

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

  Next, the present invention will be further described with reference to specific embodiments as examples, but of course, the embodiments of the present invention are not limited thereto.

[Example 1]
<< Preparation of photosensitive silver halide emulsion A >>
(Solution A1)
Phenylcarbamoylated gelatin 88.3g
Compound A (* 1) (10% aqueous methanol solution) 10 ml
Potassium bromide 0.32g
Finish to 5429 ml with water (Solution B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(Solution C1)
Potassium bromide 51.55g
Potassium iodide 1.47g
Finish to 660 ml with water (Solution D1)
Potassium bromide 154.9g
4.41 g of potassium iodide
K ₃ IrCl ₆ (equivalent to 4 × 10 ⁻⁵ mol / Ag) 50.0 ml
Finish to 1982 ml with water (Solution E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount (Solution F1)
Potassium hydroxide 0.71g
Finish to 20 ml with water (Solution G1)
56% acetic acid aqueous solution 18.0 ml
(Solution H1)
Anhydrous sodium carbonate 1.72 g
Finish to 151 ml with water (* 1) Compound A:
_{HO (CH 2 CH 2 O)} n (CH (CH 3) CH 2 O) 17 (CH 2 CH 2 O) m H
(M + n = 5-7)
Using a mixing stirrer described in Japanese Patent Publication No. 58-58288, the solution A1 was adjusted to 4 by simultaneous mixing while controlling the 1/4 amount of the solution B1 and the total amount of the solution C1 to 32 ° C. and pAg 8.09. Addition took 45 minutes to nucleate. After 1 minute, the entire amount of solution F1 was added. During this time, the pAg was adjusted as appropriate using the solution E1. After 6 minutes, 3/4 amount of the solution B1 and the total amount of the solution D1 were added over 14 minutes and 15 seconds by the simultaneous mixing method while controlling the temperature at 32 ° C. and pAg 8.09. After stirring for 5 minutes, the temperature was raised to 40 ° C., and the entire amount of the solution G1 was added to precipitate the silver halide emulsion. The supernatant was removed leaving 2000 ml of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was sedimented again. The remaining portion of 1500 ml was left, the supernatant was removed, 10 L of water was further added, and after stirring, the silver halide emulsion was allowed to settle. After leaving 1500 ml of the sedimented portion and removing the supernatant, the solution H1 was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount was 1161 g per mole of silver to obtain an emulsion.

  This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 0.040 μm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<< Preparation of organic silver salt particles >>
(Preparation of organic silver salt particles 1-1)
Organic silver salt particles 1-1 were prepared using an apparatus for producing organic silver salt particles whose configuration is shown in FIG.

  In the tank 11, 0.5 mol of stearic acid, 0.5 mol of behenic acid, 5750 g of pure water, and 206 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution. 1250 ml of an aqueous solution in which 157 g of silver nitrate was dissolved was prepared in the tank 12 and kept at 10 ° C. In a reaction tank 13, a solution obtained by mixing 6 L of pure water and 60 g of the above photosensitive silver halide emulsion A was kept at 30 ° C., and with sufficient stirring, the total amount of the organic acid alkali solution and the total amount of silver nitrate aqueous solution were changed. Each was added over 20 minutes at a constant flow rate.

  At this time, only the silver nitrate aqueous solution is added for 30 seconds after the start of the addition of the silver nitrate aqueous solution, and then the addition of the organic acid alkali solution is started. After the addition of the silver nitrate aqueous solution is completed, only the organic acid alkali solution is added. I did it. At this time, the temperature of the reaction tank 13 was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant.

  The piping of the addition system of the organic acid alkali solution was prepared by keeping warm water by circulating hot water outside the double tube so that the liquid temperature at the outlet of the addition nozzle tip was 80 ° C. Furthermore, the piping of the addition system of the silver nitrate aqueous solution was kept warm by circulating cold water outside the double pipe. The position of the addition nozzle was set so that the addition position of the organic acid alkali solution and the addition position of the aqueous silver nitrate solution were symmetrically arranged around the stirring axis.

  After completion of the addition, the mixture was stirred at the same temperature for 5 minutes to obtain an organic silver salt dispersion. Thereafter, the solid content was separated by suction filtration, and the solid content was washed with water until the conductivity of the permeated water reached 30 μS / cm. The obtained dehydrated cake was dried at 40 ° C./72 hours to obtain a dried powder of an organic silver salt dispersion containing photosensitive silver halide. When the form of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle diameter of 0.45 μm.

(Preparation of organic silver salt particles 1-2)
Organic silver salt particles 1-2 were prepared using an apparatus for producing organic silver salt particles whose configuration is shown in FIG.

  In the tank 21, 0.2 mol of stearic acid, 1150 g of pure water and 41 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for core. In the tank 26, 0.8 mol of behenic acid, 4600 g of pure water, and 165 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for shell. 1250 ml of an aqueous solution in which 157 g of silver nitrate was dissolved was prepared in the tank 22 and kept at 10 ° C. In a reaction tank 23, a solution obtained by mixing 6 L of pure water and 60 g of the photosensitive silver halide emulsion A was kept at 30 ° C.

  While sufficiently stirring the liquid in the reaction tank 23, the core organic acid alkali solution and the silver nitrate aqueous solution were added to form the core part. At this time, only the aqueous silver nitrate solution was added for 30 seconds after the start of the addition of the aqueous silver nitrate solution, and then the organic acid alkali solution for the core was added. Simultaneously with the completion of the addition of the organic acid alkali solution for the core, the addition of the aqueous silver nitrate solution was once stopped, and the mixture was stirred as it was for 5 minutes to prepare the core part. At that time, some samples for core evaluation were collected.

  Subsequent to the preparation of the core portion, the switching valve 27 was operated to add the shell organic acid alkali solution. At the same time, the addition of the aqueous silver nitrate solution was resumed to form a shell portion. At this time, only the organic acid alkali solution for shells was added for 30 seconds after the addition of the aqueous silver nitrate solution was completed. The total amount of the organic acid alkali solution for the core and shell and the total amount of the aqueous silver nitrate solution were each added at a constant flow rate over 20 minutes. At this time, the temperature of the reaction tank 23 was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 1-1. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle diameter of 0.44 μm. The average particle size of the core portion was 0.18 μm.

(Preparation of organic silver salt particles 1-3)
In the tank 21, 0.3 mol of stearic acid, 1725 g of pure water, 62 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for core. In the tank 26, 0.7 mol of behenic acid, 4025 g of pure water, 144 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for shell.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 1-2. When the form of the obtained organic silver salt particles was evaluated by electron microscope photography, the particles had an average particle diameter of 0.47 μm. The average particle size of the core part was 0.24 μm.

(Preparation of organic silver salt particles 1-4)
In the tank 21, 0.4 mol of stearic acid, 2300 g of pure water, and 82 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for core. In the tank 26, 0.6 mol of behenic acid, 3450 g of pure water and 124 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for shell.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 1-2. When the morphology of the obtained organic silver salt particles was evaluated by electron microscope photography, the average particle size was 0.48 μm. The average particle size of the core portion was 0.35 μm.

(Preparation of organic silver salt particles 1-5)
In the tank 21, 0.7 mol of stearic acid, 4025 g of pure water, 144 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for core. In the tank 26, 0.3 mol of behenic acid, 1725 g of pure water and 62 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for shell.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 1-2. When the form of the obtained organic silver salt particles was evaluated by electron microscope photography, the particles had an average particle diameter of 0.47 μm. The average particle size of the core portion was 0.42 μm.

<< Preparation of photosensitive emulsion dispersion A-1 >>
7.3 g of Exemplified Compound P-9 shown in Table 1 above was dissolved in 728.5 g of methyl ethyl ketone, and the above-mentioned silver halide grain-containing material was stirred with a dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN A preliminary dispersion A-1 was prepared by gradually adding 250 g of the powdered organic silver salt 1-1 and thoroughly mixing.

  Media type in which the preliminary dispersion A-1 is filled with 80% of the internal volume of 0.5 mm diameter zirconia beads (Traceram manufactured by Toray Industries, Inc.) using a pump so that the residence time in the mill is 1.5 minutes. This was supplied to a disperser DISPERMAT SL-C12EX type (manufactured by VMA-GETZMANN) and dispersed at a mill peripheral speed of 8 m / sec to prepare photosensitive emulsion dispersion A-1.

<< Preparation of photosensitive emulsion dispersions A-2 to A-5 >>
In the preparation of the photosensitive emulsion dispersion A-1, silver halide grain-containing powdered organic silver salts 1-2 to 1-5 were used instead of the silver halide grain-containing powdered organic silver salt 1-1, respectively. In the same manner as described above, photosensitive emulsion dispersions A-2 to A-5 were prepared.

<Production of support>
One side of a 175 μm-thick polyethylene terephthalate film colored blue with a concentration of 0.170 was subjected to a corona discharge treatment of 0.5 kV · A · min / m ² , and then the following undercoat coating solution A was applied thereon. The undercoat layer a was applied so that the dry film thickness was 0.2 μm. Further, the other surface was similarly subjected to a corona discharge treatment of 0.5 kV · A · min / m ² , and then the undercoat layer b was formed thereon using the following undercoat coating solution B to form a dry film The coating was applied so that the thickness was 0.1 μm. Thereafter, heat treatment was performed at 130 ° C. for 15 minutes in a heat treatment type oven having a film transport device composed of a plurality of roll groups.

(Undercoating liquid A)
270 g of copolymer latex liquid (solid content 30%) of butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (30/20/25/25%), 0 of surfactant (UL-1) .6 g and 0.5 g of methylcellulose were mixed. Further, 1.3 g of silica particles (Syloid 350: manufactured by Fuji Silysia) was added to 100 g of water, and dispersion treatment was performed for 30 minutes with an ultrasonic disperser (manufactured by ALEX Corporation: Ultrasonic Generator, frequency 25 kHz, 600 W). The resulting dispersion was added and finally made up to 1000 ml with water.

(Undercoating liquid B)
37.5 g of the following colloidal tin oxide dispersion, a copolymer latex liquid (solid content 30%) of butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (20/30/25/25%) 3.7 g, 14.8 g of a copolymer latex liquid (solid content 30%) of butyl acrylate / styrene / glycidyl methacrylate (40/20/40%) and 0.1 g of a surfactant (UL-1) The mixture was mixed and finished to 1000 ml with water.

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

<< Preparation of Sample 101 >>
In accordance with the following procedure, Sample 101 as a heat-developable image recording material was produced.

[Back side application]
While stirring 830 g of methyl ethyl ketone, 84.2 g of cellulose acetate butyrate (Eastman Chemical: CAB381-20) and 4.5 g of polyester resin (Bostic: VitelPE2200B) were added and dissolved. Next, 0.30 g of infrared dye 1, 4.5 g of fluorine-based activator-1 and 1.5 g of fluorine-based activator (Gemco: Ftop EF-105) are added to the dissolved liquid, Stir well until dissolved. Finally, 75 g of silica particles (manufactured by Fuji Silysia: Silicia 450) dispersed in methyl ethyl ketone at a concentration of 1% with a dissolver type homogenizer were added and stirred to prepare a back surface coating solution.

Fluorine-based activator-1: C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₂ C ₉ F ₁₇
Next, the prepared back surface coating solution was coated and dried on the surface coated with the undercoat layer b of the support using an extrusion coater so that the dry film thickness was 3.5 μm. It was dried for 5 minutes using a drying air having a drying temperature of 100 ° C. and a dew point temperature of 10 ° C.

[Coating on the photosensitive layer side]
(Preparation of each additive solution)
<Preparation of stabilizer solution>
A stabilizer liquid was prepared by dissolving 1.0 g of Stabilizer-1 and 0.31 g of potassium acetate in 4.97 g of methanol.

<Preparation of infrared sensitizing dye liquid A>
19.2 mg of infrared sensitizing dye-1, 1.488 g of 2-chloro-benzoic acid, 2.7779 g of stabilizer-2 and 365 mg of 5-methyl-2-mercaptobenzimidazole were added to 31.3 ml of methyl ethyl ketone. In the dark, an infrared sensitizing dye solution A was prepared.

<Preparation of additive solution a>
27.98 g of 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane (referred to as reducing agent A) as a developer, 1.54 g of 4-methylphthal The acid, 0.48 g of the infrared dye 1 was dissolved in 110 g of methyl ethyl ketone to obtain an additive solution a.

<Preparation of additive liquid b>
3.56 g of antifoggant-2, 3.43 g of phthalazine were dissolved in 40.9 g of methyl ethyl ketone to obtain additive solution b.

(Preparation of photosensitive layer coating liquid A-1)
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion A-1 and 15.11 g of methyl ethyl ketone were kept at 21 ° C. with stirring to prevent fogging 1 (10% methanol solution). 390 μl was added and stirred for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 20 minutes. Subsequently, 167 μl 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., 13.31 g of a polymer (Exemplary Compound P-9 described in Table 1) as a binder resin was added and stirred for 30 minutes, and then tetrachlorophthalic acid (9.4 mass% methyl ethyl ketone solution) 1 0.084 g was added and stirred for 15 minutes. Further, while continuing stirring, 12.43 g of additive solution a, 1.6 ml of Desmodur N3300 (Mobey aliphatic isocyanate 10% methyl ethyl ketone solution), and 4.27 g of additive solution b were sequentially added and stirred. The coating layer coating liquid A-1 was obtained.

(Preparation of surface protective layer coating solution)
While stirring 865 g of methyl ethyl ketone, 96 g of cellulose acetate butyrate (CAB171-15: supra), 4.5 g of polymethylmethacrylic acid (Rohm & Haas: Paraloid A-21), 1.0 g of benzotriazole Then, 1.0 g of a fluorine-based activator (Gemco Co., Ltd .: F-top EF-105) was added and dissolved. Next, 30 g of the following matting agent dispersion was added and stirred to prepare a surface protective layer coating solution.

<Preparation of matting agent dispersion>
Dissolve 7.5 g of cellulose acetate butyrate (Eastman Chemical: CAB171-15) in 42.5 g of MEK, add 5 g of silica particles (Fuji Silysia: Silysia 320), and use a dissolver type homogenizer. Dispersion was performed at 8000 rpm for 30 minutes to prepare a matting agent dispersion.

(Application)
The photosensitive layer coating solution A-1 and the surface protective layer coating solution prepared above were simultaneously applied by using a known extrusion coater. The coating was carried out so that the photosensitive layer had a coated silver amount of 1.7 g / m ² and the surface protective layer had a dry film thickness of 2.5 μm. Then, it dried for 10 minutes using the drying air with a drying temperature of 75 degreeC, and dew point temperature of 10 degreeC, and produced the sample 101. FIG.

<< Production of Samples 102 to 105 >>
Samples 102 to 105 were prepared in the same manner as in the preparation of Sample 101 except that the type of the photosensitive emulsion dispersion used for the preparation of the photosensitive layer coating solution A-1 was changed to A-2 to A-5. did.

<Evaluation of heat-developable image recording material>
Various evaluations were performed on the manufactured samples 101 to 105 according to the following methods.

<Evaluation of photographic performance>
The photosensitive material prepared as described above is exposed from the emulsion surface side using a laser sensitometer having a semiconductor laser having a wavelength of 810 nm, and then the protective layer and drum of the photothermographic material using an automatic processor having a heat drum. It was heat-developed at 123 ° C. for 10 seconds with the surface in contact. At that time, exposure and development were performed in a room adjusted to 23 ° C. and 50% RH.

[Immediate performance]
The maximum density (Dmax), fog density (Dmin) and sensitivity of the obtained image were measured. The optical density was measured with a Densitometer PDA-65 manufactured by Konica Minolta.
Dmax: The visual transmission density in the maximum exposed part of the exposed part (previously: PDA-65 up to two digits after the decimal point) was measured at 10 points, and the average value was taken as the maximum density (Dmax).
Dmin: The visual transmission density of the unexposed part (previously: PDA-65 up to 3 digits after the decimal point) was measured at 10 points, and the average value was defined as the fog density (Dmin).
Sensitivity: It was determined as the reciprocal of the ratio of the exposure amount that gives a density 1.0 higher than that of the unexposed portion, and is shown as a relative value with the sample 101 as 100.

[Storage over time]
Each of the photothermographic materials thus prepared was divided into two sets, each was sealed in a barrier bag at a humidity of 55%, and stored at 25 ° C. and 55 ° C. for 3 days, respectively. Thereafter, the same processing as in the immediate performance evaluation was performed, and the fogging and sensitivity of both were measured. The aging preservability of each sample was evaluated based on the fog and sensitivity (Δ fog, Δ sensitivity) of the photothermographic material stored at 25 ° C. and 55 ° C.

  The results are shown in Table 2.

  From Table 2, the photothermographic material of the present invention is a photosensitive material having high sensitivity, high covering power, little fogging, and excellent storage stability with time, whereby excellent image recording is possible. I understand.

Example 2
(Preparation of organic silver salt particles 2-1)
Organic silver salt particles 2-1 were prepared using the organic silver salt particle production apparatus of FIG. In the tank 21, 0.4 mol of stearic acid, 2300 g of pure water, and 82 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for core. In the tank 26, 0.6 mol of behenic acid, 3450 g of pure water and 124 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for shell. 1250 ml of an aqueous solution in which 157 g of silver nitrate was dissolved was prepared in the tank 22 and kept at 10 ° C. 6 L of pure water was kept at 30 ° C. in the reaction tank 23.

  While sufficiently stirring the liquid in the reaction tank 23, the core organic acid alkali solution and the silver nitrate aqueous solution were added to form the core part. At this time, only the aqueous silver nitrate solution was added for 30 seconds after the start of the addition of the aqueous silver nitrate solution, and then the organic acid alkali solution for the core was added. Simultaneously with the addition of the organic acid alkali solution for the core, the addition of the aqueous silver nitrate solution was once stopped, and the mixture was stirred for 5 minutes to adjust the core part. At that time, some samples for core evaluation were collected.

  Following the adjustment of the core part, a solution in which 60 g of the photosensitive silver halide emulsion A was mixed was added to the reaction tank 23 and stirred for 5 minutes, and then the switching valve 27 was operated to change the organic acid / alkali solution for shell. The addition was made. At the same time, the addition of the aqueous silver nitrate solution was resumed to form a shell portion. At this time, only the organic acid alkali solution for shells was added for 30 seconds after the addition of the aqueous silver nitrate solution was completed. The total amount of the organic acid alkali solution for the core and shell and the total amount of the aqueous silver nitrate solution were each added at a constant flow rate over 20 minutes. At this time, the temperature of the reaction tank 23 was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 1-1. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle diameter of 0.48 μm and a coefficient of variation of 63%. The average particle size of the core part was 0.34 μm and the coefficient of variation was 55%.

(Preparation of organic silver salt particles 2-2)
Organic silver salt particles 2-2 were prepared using an apparatus for producing organic silver salt particles whose configuration is shown in FIG. In the tank 31, 0.4 mol of stearic acid, 2417 g of pure water, and 82 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain a core organic acid alkali solution. In the tank 35, 0.6 mol of behenic acid, 3450 g of pure water and 124 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution for shell. In the tank 32, 2641 ml of an aqueous solution in which 62.5 g of silver nitrate for core was dissolved was prepared and kept at 10 ° C. In a tank 36, 750 ml of an aqueous solution in which 94.5 g of silver nitrate for shell was dissolved was prepared and kept at 10 ° C.

  The core portion was formed by adding the total amount of the organic acid alkali solution for core and the aqueous silver nitrate solution at a constant flow rate of 500 ml / min to the apparatus indicated by 33 in FIG. 3 (inner diameter of supply pipe and discharge pipe 2 mm). The formed core particles were stocked in the reaction tank 34, and the external temperature was controlled so that the liquid temperature became 30 ° C. At that time, some samples for core evaluation were collected.

  Following the adjustment of the core portion, a solution in which 60 g of the above photosensitive silver halide emulsion A was mixed was added to the reaction tank 34 and stirred for 5 minutes, and then an organic acid alkali solution for shell and an aqueous silver nitrate solution were added. The shell part was formed. At this time, only the aqueous silver nitrate solution was added for 30 seconds after the start of addition of the aqueous silver nitrate solution, and then the organic acid alkali solution was added. Further, only the organic acid alkali solution was added for 30 seconds after the addition of the aqueous silver nitrate solution. The total amount of the organic acid alkali solution and the total amount of the aqueous silver nitrate solution were each added at a constant flow rate over 12 minutes. At this time, the temperature of the reaction tank 23 was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 2-1. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.49 μm and a coefficient of variation of 48%. The average particle size of the core part was 0.35 μm and the coefficient of variation was 41%.

(Preparation of organic silver salt particles 2-3)
A dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 2-2 except that the organic acid alkali solution for the core and the aqueous silver nitrate solution were added at 1000 ml / min. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.47 μm and a coefficient of variation of 33%. The average particle size of the core part was 0.33 μm and the coefficient of variation was 28%.

<< Production of Samples 201 to 203 and Evaluation of Photographic Performance >>
Samples 201 to 203 as heat-developable image recording materials were prepared in the same manner as in Example 1 except that powdered organic silver salts 2-1 to 2-3 containing silver halide grains were used, and photographic performance was evaluated. went. The sensitivity is shown as a relative value with the sample 101 as 100.

  The results are shown in Table 3.

  From Table 3, the photothermographic material of the present invention is a photosensitive material having high sensitivity, high covering power, little fogging, and excellent storability over time, and this enables excellent image recording. Understand.

Example 3
(Preparation of organic silver salt particles 3-1)
Organic silver salt particles 3-1 were prepared using the apparatus for producing organic silver salt particles of FIG. In the tank 11, 1 mol of behenic acid, 5750 g of pure water, and 206 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes to obtain an organic acid alkali solution. 1250 ml of an aqueous solution in which 157 g of silver nitrate was dissolved was prepared in the tank 12 and kept at 10 ° C.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 1-1. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.51 μm and a coefficient of variation of 84%.

(Preparation of organic silver salt particles 3-2)
Organic silver salt particles 3-2 were prepared using the apparatus shown in FIG. In the tank 31, 0.37 mol of arachidic acid, 2000 g of pure water, and 75 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. Additional pure water was added to obtain 2500 ml of an organic acid alkali solution for the core finished. In the tank 35, 0.63 mol of behenic acid, 4000 g of pure water, and 131 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. 4500 ml of an organic acid alkali solution for a shell finished by adding additional pure water was obtained. In the tank 32, 2500 ml of an aqueous solution in which 57 g of core silver nitrate was dissolved was prepared and kept at 10 ° C. In a tank 36, 750 ml of an aqueous solution in which 100 g of silver nitrate for shell was dissolved was prepared and kept at 10 ° C.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 2-3. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.50 μm and a coefficient of variation of 30%. The average particle size of the core part was 0.36 μm and the coefficient of variation was 27%.

(Preparation of organic silver salt particles 3-3)
In the tank 31, 0.38 mol of stearic acid, 2000 g of pure water, and 78 ml of a 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. Additional pure water was added to obtain 2500 ml of an organic acid alkali solution for the core finished. In the tank 35, 0.62 mol of behenic acid, 4000 g of pure water and 128 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. 4500 ml of an organic acid alkali solution for a shell finished by adding additional pure water was obtained. In a tank 32, 2500 ml of an aqueous solution in which 60 g of core silver nitrate was dissolved was prepared and kept warm at 10 ° C. In a tank 36, 750 ml of an aqueous solution in which 97 g of silver nitrate for shell was dissolved was prepared and kept at 10 ° C.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 3-2. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.50 μm and a coefficient of variation of 28%. The average particle size of the core part was 0.35 μm and the coefficient of variation was 25%.

(Preparation of organic silver salt particles 3-4)
In tank 31, 0.40 mol of palmitic acid, 2000 g of pure water, 82 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. Additional pure water was added to obtain 2500 ml of an organic acid alkali solution for a core finished. In the tank 35, 0.60 mol of behenic acid, 4000 g of pure water and 124 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. Additional pure water was added to obtain 4500 ml of a shell organic acid alkali solution finished. 2500 ml of an aqueous solution in which 63 g of silver nitrate for core was dissolved was prepared in the tank 32 and kept at 10 ° C. In the tank 36, 750 ml of an aqueous solution in which 94 g of silver nitrate for shell was dissolved was prepared and kept at 10 ° C.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 3-2. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.50 μm and a coefficient of variation of 32%. The average particle size of the core part was 0.35 μm and the coefficient of variation was 28%.

(Preparation of organic silver salt particles 3-5)
In tank 31, 0.42 mol of myristylic acid, 2000 g of pure water, and 87 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. Additional pure water was added to obtain 2500 ml of an organic acid alkali solution for the core finished. In a tank 35, 0.58 mol of behenic acid, 4000 g of pure water, and 119 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. 4500 ml of an organic acid alkali solution for a shell finished by adding additional pure water was obtained. In the tank 32, 2500 ml of an aqueous solution in which 66 g of core silver nitrate was dissolved was prepared and kept at 10 ° C. In the tank 36, 750 ml of an aqueous solution in which 91 g of silver nitrate for shell was dissolved was prepared and kept at 10 ° C.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 3-2. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.49 μm and a variation coefficient of 33%. The average particle size of the core part was 0.35 μm and the coefficient of variation was 28%.

(Preparation of organic silver salt particles 3-6)
In the tank 31, 0.44 mol of lauric acid, 2000 g of pure water, 91 ml of a 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. Additional pure water was added to obtain 2500 ml of an organic acid alkali solution for the core finished. In the tank 35, 0.56 mol of behenic acid, 4000 g of pure water and 115 ml of 5 mol / L KOH aqueous solution were mixed and reacted at 80 ° C. for 60 minutes. 4500 ml of an organic acid alkali solution for a shell finished by adding additional pure water was obtained. In a tank 32, 2500 ml of an aqueous solution in which 69 g of silver nitrate for core was dissolved was prepared and kept warm at 10 ° C. In a tank 36, 750 ml of an aqueous solution in which 88 g of silver nitrate for shell was dissolved was prepared and kept at 10 ° C.

  Except for the above changes, a dried powder of the organic silver salt dispersion was obtained in the same manner as the organic silver salt particles 3-2. When the morphology of the obtained organic silver salt particles was evaluated by electron microscopic photography, the particles had an average particle size of 0.48 μm and a coefficient of variation of 29%. The average particle size of the core part was 0.34 μm and the coefficient of variation was 26%.

<< Production of Samples 301 to 306 and Evaluation of Photographic Performance >>
Samples 301 to 306, which are heat-developable image recording materials, were prepared in the same manner as in Example 1 except that powdered organic silver salts 3-1 to 3-6 containing silver halide grains were used, and photographic performance was evaluated. went. The sensitivity is expressed as a relative value where the sample 301 is 100.

  The results are shown in Table 4.

  From Table 4, the photothermographic material of the present invention is a photosensitive material having high sensitivity, high covering power, little fogging, and excellent storability over time, and this enables excellent image recording. Understand.

The block diagram of the manufacturing apparatus of organic silver salt particle | grains. The block diagram of the manufacturing apparatus of organic silver salt particle | grains. The block diagram of the manufacturing apparatus of organic silver salt particle | grains.

Explanation of symbols

11, 21, 31 Additive liquid 1 tank 12, 22, 32 Additive liquid 2 tank 13, 23, 34 Reaction tank 14, 24, 37 Flow meter 15, 25, 38 Pump 26, 35 Additive liquid 3 tank 27 Switching Valve 33 Mixer 36 Tank for additive 4

Claims (5)

In a photothermographic material having at least photosensitive silver halide particles, non-photosensitive organic silver salt particles, a silver ion reducing agent and a binder on the same surface of the support, the non-photosensitive organic silver salt particles have a silver salt composition. It has different core parts and shell parts, and the ratio of the average diameter of the organic silver salt particles in the core part to the average diameter of the organic silver salt particles including the shell part satisfies the following equation (1): A photothermographic material.
0.5 ≦ L ₁ / L ₂ <1 (1)
L ₁ : Average diameter of organic silver salt particles in the core portion L ₂ : Average diameter of organic silver salt particles including the shell portion _{2. The} photothermographic material according to claim 1, wherein the condition of the formula (1) is 0.6 ≦ L ₁ / L ₂ ≦ 0.9. 3. The photothermographic sensor according to claim 1, wherein a dispersion degree of the particles composed only of the core portion of the non-photosensitive organic silver salt particles is 50% or less in a distribution range defined below. material.
Definition of width of distribution (standard deviation of particle size / average particle size) × 100 = width of distribution (%) 4. The photothermographic material according to claim 3, wherein a degree of dispersion of the non-photosensitive organic silver salt particles is 50% or less.
Definition of width of distribution (standard deviation of particle size / average particle size) × 100 = width of distribution (%) The shell part is composed of a plurality of layers, and the ratio of the average molecular weight value of the organic silver salt constituting the outermost layer to the average molecular weight value of the organic silver salt in the core part is 1 on the basis of the core part. 5. The photothermographic material according to claim 1, wherein the photothermographic material is 1 or more and 1.4 or less.

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