JP2008009307A - Method for manufacturing heat developable photosensitive material and heat developable photosensitive material manufactured by the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a heat developable photosensitive material with a low impact on the environment, and a heat developable photosensitive material manufactured by the same. <P>SOLUTION: In the method for manufacturing a heat developable photosensitive material containing at least a photosensitive silver halide, a non-photosensitive organic silver salt and a reducing agent for the organic silver salt on one surface of a support, the heat developable photosensitive material contains a polymer dispersion containing ≥0.01 mass% of a surfactant of which the biochemical oxygen demand (BOD) is ≥60% of theoretical oxygen demand (ThOD) and 10-500 ppm of a preservative. The manufacturing method includes at least a step of storing such a polymer dispersion in a container, a step of drawing the polymer dispersion from the container and preparing a coating liquid, and a step of applying and drying the coating liquid, wherein a sterilized container is used as the container for storing the polymer dispersion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a photothermographic material and a photothermographic material produced thereby. In particular, the present invention relates to a method for producing a photothermographic material having a low environmental impact and a photothermographic material produced thereby.

  In recent years, in the medical field, reduction of waste processing liquid has been strongly desired from the viewpoint of environmental protection and space saving. Therefore, photosensitive thermal development for medical diagnosis and photographic technology that can be efficiently exposed by a laser image setter or laser imager and can form a clear black image with high resolution and sharpness. There is a need for technology relating to photographic materials. These photosensitive heat-developable photographic materials eliminate the use of solution processing chemicals and can provide customers with a heat-development processing system that is simpler and does not impair the environment.

  Although there is a similar requirement in the field of general image forming materials, medical images are required to have high image quality with excellent sharpness and graininess because they are required to be finely drawn, and are cooled from the viewpoint of ease of diagnosis. There is a feature that a black tone image is preferred. At present, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed as general image forming systems. However, there is no satisfactory output system for medical images.

  On the other hand, a thermal image forming system using an organic silver salt is known. In particular, the photothermographic material generally contains a catalytically active amount of a photocatalyst (eg, silver halide), a reducing agent, a reducible silver salt (eg, an organic silver salt), and a color tone that controls the color tone of silver if necessary. And an image forming layer dispersed in a binder matrix. The photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, and is blackened by an oxidation-reduction reaction between silver halide or a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form a silver image. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure. Therefore, a black silver image is formed in the exposure area. This method is disclosed in many documents, and Fuji Medical Dry Imager FM-DPL is on sale as a medical image forming system using a photothermographic material.

  Examples of the photothermographic material include a solvent-coated photothermographic material produced by coating with an organic solvent and an aqueous coating type photothermographic material produced using an aqueous solvent using a polymer latex as a main binder. Since the latter method does not require a process such as solvent recovery, the manufacturing equipment is simple, the environmental load is small, and it is advantageous for mass production.

Since many of the materials used for the water-based photothermographic material are water-insoluble or hardly soluble, their aqueous dispersions are prepared and then added to the coating solution (see, for example, Patent Documents 1 and 2). .
In preparing an aqueous dispersion, many surfactants have been used as dispersants, dispersion stabilizers, and emulsifiers in emulsion polymerization.
However, when a polymer dispersion stored for a long period of time is used, there is a problem that a coated surface failure occurs (for example, Patent Document 3).

In recent years, surfactants have flowed into rivers or accumulated in soil, and the effects on human beings have become a problem due to the food chain of fish, plants and animals. Therefore, the development of surfactants with good biodegradability has progressed, and in many fields, switching to environmentally friendly surfactants with good biodegradability is desired. In the production of photothermographic materials, it has been desired to use a surfactant having good biodegradability.
Japanese Patent Laid-Open No. 10-10669 Japanese Patent Laid-Open No. 10-10670 JP 2002-99054 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a photothermographic material production method and a photothermographic material produced by the photothermographic material, which are less burdened on the environment and cause no coating surface failure.

The object of the present invention has been achieved by the following photothermographic materials.
<1> A method for producing a photothermographic material comprising, on one side of a support, at least a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent for the organic silver salt, The photothermographic material contains 0.01% by mass or more of a surfactant having a biochemical oxygen demand (BOD value) of 60% or more of the theoretical oxygen demand (ThOD value) and 10 ppm or more and 500 ppm or less of a preservative. And the manufacturing method includes storing at least the polymer dispersion in a container, removing the polymer dispersion from the container to prepare a coating liquid, and applying and drying the coating liquid. A method for producing a photothermographic material, comprising a step of using a sterilized container as a container for storing the polymer dispersion.
<2> The method for producing a photothermographic material according to <1>, wherein the surfactant has a primary to tertiary carbon atom and does not have a quaternary carbon atom.
<3> The photothermographic material according to <1> or <2>, wherein the concentration of the surfactant in the polymer dispersion is 0.01% by mass or more and 5.0% by mass or less. Production method.
<4> The method for producing a photothermographic material according to any one of <1> to <3>, wherein the preservative is isothiazolinone or a derivative thereof.
<5> The method for producing a photothermographic material according to <4>, wherein the preservative is benzoisothiazolinone.
<6> The heat according to any one of <1> to <5>, wherein the concentration of the preservative in the polymer dispersion is 0.001% by mass or more and 0.05% by mass or less. A method for producing a development photosensitive material.
<7> The method for producing a photothermographic material according to any one of <1> to <6>, wherein the polymer dispersion is a polymer latex.
<8> The method for producing a photothermographic material according to <7>, wherein the polymer latex is an acrylic resin latex.
<9> The method for producing a photothermographic material according to <7>, wherein the polymer latex is SBR latex.
<10> The method for producing a photothermographic material according to <7>, wherein the polymer latex is isoprene latex.
<11> The method for producing a photothermographic material according to any one of <1> to <6>, wherein the polymer dispersion is a polymer matting agent.
<12> The method for producing a photothermographic material according to any one of <1> to <11>, wherein the sterilization treatment is a heat sterilization treatment.
<13> The method for producing a photothermographic material according to any one of <1> to <12>, wherein the coating solution contains gelatin.
<14> A photothermographic material produced by the production method according to any one of <1> to <13>.

  The present invention provides a method for producing a photothermographic material having a low environmental impact and a photothermographic material produced thereby.

  In addition, the numerical value described before and behind "-" in description of this application means the minimum and upper limit including the numerical value. For example, when “2 to 100” is described, it means “2 to 100”.

1. Method for Producing Photothermographic Material The method for producing a photothermographic material of the present invention comprises reducing at least a photosensitive silver halide, a non-photosensitive organic silver salt, and an organic silver salt on one side of a support. A method for producing a photothermographic material containing an agent, wherein the photothermographic material comprises 0.01% by mass or more of a surfactant having a BOD value of 60% or more of the ThOD value and 10 ppm or more and 500 ppm or less of a preservative. Containing the polymer dispersion, and the manufacturing method includes at least a step of storing the polymer dispersion in a container, a step of removing the polymer dispersion from the container to prepare a coating solution, and applying and drying the coating solution. And a sterilized container is used as a container for storing the polymer dispersion.

The present inventors diligently studied the use of a surfactant having good biodegradability when producing a photothermographic material. However, the surface area of the photothermographic material coated with the dispersion has been greatly deteriorated as the storage period of the polymer dispersion used for production becomes longer after the dispersion is prepared.
The deterioration of the coated surface was particularly large when a surfactant with good biodegradability was used.
As a result of searching for cause analysis and improvement means, the inventors have reached the invention of the production method of the present invention.
At this time, it has been clarified that when the amount of the preservative is increased, the polymer dispersion easily aggregates and adversely affects the coated surface.

BOD is a biochemical oxygen demand, which is determined from the amount of dissolved oxygen consumed when stored with stirring for 28 days at 25 ° C., according to OECDTG301C.
ThOD is a theoretical oxygen demand, which is obtained by calculating the amount of oxygen required when the corresponding chemical is fully oxidized.
On the other hand, when the BOD value of the surfactant used in the aqueous dispersion for the photothermographic material is 60% or more of the ThOD value, the biodegradability is good and the environmental load when discharged into the environment is small. There is a problem in the storage stability of the polymer dispersion, and if it is less than 60%, the environmental burden is large, which is not preferable.

  If the addition amount of the preservative is less than 10 ppm, it is not preferable because a sufficient effect of improving the storage stability cannot be obtained, and if the addition amount of the preservative exceeds 500 ppm, the aggregation property of the polymer dispersion is deteriorated. Absent.

Preferably, the surfactant does not have two or more carbon atoms in total including tertiary or quaternary carbon. Preferably, the concentration of the surfactant in the polymer dispersion is 0.01% by mass or more and 5.0% by mass or less.
Preferably, the preservative is isothiazolinone, and more preferably, the preservative is benzoisothiazolinone. Preferably, the concentration of the preservative in the polymer dispersion is 0.001% by mass or more and 0.05% by mass or less.
Preferably, the polymer dispersion is a polymer latex. Preferably, the polymer latex is an acrylic resin latex, SBR latex, or isoprene latex.
In another preferred embodiment, the polymer dispersion is a polymer matting agent.
Preferably, the sterilization process is a heat sterilization process.
Preferably, the coating solution contains gelatin.

  The present invention is described in detail below.

  In the present invention, a surfactant having a BOD value in OECD Test Guideline 301C of 60% or more of the ThOD value is used. A surfactant having a degradation rate represented by the BOD / ThOD of less than 60% is not preferable because of poor biodegradability in the environment. Specific examples of the surfactant having a decomposition rate of 60% or more include alkylbenzene sulfonate (soft type), α-olefin sulfonate, polyoxyethylene alkyl ether and the like, but are not limited thereto. Absent.

  In addition, it has been conventionally known that the branching of the hydrophobic part greatly affects the biodegradability of the surfactant, and the biodegradability is lowered by increasing the branching of the hydrophobic part. By using such a surfactant, the storage stability of the dispersion can be improved, but the burden on the environment is large, which is not preferable. In the present invention, it is preferable to use a surfactant that does not have two or more saturated tertiary or quaternary carbons in the hydrophobic portion, and particularly preferably does not have two or more methyl groups.

The surfactant may be used alone or in combination of two or more. However, when two or more surfactants are used in combination, the total amount of surfactant satisfying BOD / ThOD ≧ 60% is added to the polymer dispersion. It is preferable that it is 0.01 mass%-5.0 mass%, and it is more preferable that it is 0.5 mass%-3.0 mass%.
When a plurality of surfactants are used in combination, an arbitrary amount of BOD / ThOD <60% surfactant can be added as long as the surfactant satisfying BOD / ThOD ≧ 60% is the above amount. The total amount of the surfactant is preferably 0.01% by mass to 5% by mass, and from the viewpoint of the environment, the surfactant amount (decomposition rate ≧ 60%) / surfactant amount (decomposition rate <60% ) Ratio is preferably 1/1 or more.

There are no particular restrictions on the preservative used in the present invention, but photographic preservatives such as those described in JP-A-2002-99054, paragraphs 35 to 49, are preferred, and release into the environment during heat development Therefore, the preservative preferably has a boiling point of 120 ° C. or higher, more preferably 160 ° C. or higher.
Among the above-mentioned photographic preservatives, since the influence on fogging is small, in the publication, an isothiazolinone-based preservative represented by the general formula [II] is more preferable. The benzoisothiazolinone-type preservative represented is more preferred because it has little effect on sensitivity, and 1,2-benzisothiazolin-3-one is particularly preferred.

The sterilization treatment in the present invention, the number of containers inside the aerobic vessel volume 1 cm ³ per 100c. f. u. It refers to the following operations. The number of bacteria can be determined by spreading sterile water until the entire container is spread immediately after the sterilization operation, and counting the number of aerobic bacteria in the liquid immediately after filling by the agar medium method or the like.

The container sterilization method is not particularly limited, and a known method can be used. Specific examples include sterilization with steam or hot water, sterilization with a gas such as ethylene oxide, sterilization with chemicals such as formalin and ethanol, or sterilization with microwaves or UV irradiation.
Of these, sterilization by steam or hot water or sterilization by irradiation with electromagnetic waves is preferred because there is no effect on the photographic properties of the residual drug. For a container having a complicated structure such as a container having a ball valve, sterilization with steam or hot water is more preferable to sterilize the structure, and sterilization with hot water is particularly preferable.

Sterilization with hot water is performed by filling the container with hot water, maintaining the state where the hot water has spread throughout the container, and then discharging the hot water. At this time, hot water is preferably 60 ° C. or higher, and more preferably 80 ° C. or higher. In addition, hot water may stay or flow as long as the hot water reaches the entire container, but the hot water preferably keeps the hot water spread for at least 5 minutes and is held for at least 30 minutes. More preferably.
When the temperature of the hot water is lower than 60 ° C. or the holding time is shorter than 5 minutes, it is not preferable because sufficient sterilization cannot be performed and a desired effect cannot be obtained.

Storage of the polymer dispersion in a sterilized container is preferably performed within one day after sterilization, and more preferably within 5 hours. It is not preferable to perform storage after 1 day or more after sterilization because bacteria mixed in from the atmosphere may propagate inside the container. Furthermore, in order to reduce bacterial contamination per unit amount of material, the area of the inner wall of the container is preferably 1 cm ² or less per 1 mL of polymer dispersion stored, and more preferably 0.1 cm ² or less.

(Description of polymer dispersion)
In the present invention, the polymer dispersion stored in the sterilized container may be any polymer contained in the photothermographic material. Examples thereof include a polymer latex used for an image forming layer, an intermediate layer, a surface protective layer or a back layer, and a polymer matting agent used for a surface protective layer or a back layer.

  When a surfactant having BOD / ThOD ≧ 60% in the present invention is added to the polymer dispersion, it is preferably added so as to be 0.01% by mass to 5.0% by mass with respect to the polymer component. More preferably, the content is from mass% to 3.0 mass%. It is not preferable to use an excessive amount of a surfactant because the fog is deteriorated. The pH of the polymer dispersion is preferably 5 or more, and more preferably 6-9. If the pH is too low, the aggregation stability of the polymer decreases, which is not preferable. If the pH is too high, the color tone of the photothermographic material is affected.

1) Polymer Latex In the present invention, the average particle size of the polymer latex is 1 nm or more and 50000 nm or less, preferably 5 nm or more and 1000 nm or less, more preferably 10 nm or more and 500 nm or less, and further preferably 50 nm or more and 200 nm or less. is there. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution. Mixing two or more types having a monodispersed particle size distribution is also a preferable method for controlling the physical properties of the coating solution.

In the present invention, the polymer is not particularly limited, but rubbers (for example, SBR resin, isoprene resin, etc.), acrylic polymers, poly (esters), poly (urethanes), poly (vinyl chloride) s, poly (vinyl chlorides) Hydrophobic polymers such as vinyl acetate), poly (vinylidene chloride) s, and poly (olefins) can be preferably used. These polymers may be linear polymers, branched polymers, crosslinked polymers, so-called homopolymers obtained by polymerizing a single monomer, or copolymers obtained by polymerizing two or more types of monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of these polymers is from 5,000 to 1,000,000, preferably from 10,000 to 200,000 in terms of number average molecular weight. When the molecular weight is too small, the mechanical strength of the image forming layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable. A crosslinkable polymer latex is particularly preferably used.
The Tg of the hydrophobic polymer of the present invention is preferably in the range of −30 ° C. or more and 70 ° C. or less. More preferably, it is -10 degreeC or more and 35 degrees C or less, Most preferably, it is 0 degreeC or more and 35 degrees C or less. When Tg is lower than −30 ° C., the film formability is excellent, but the film has weak heat resistance strength. When it is higher than 70 ° C., the polymer has excellent heat resistance strength, but the film formability is poor. Since it becomes a sufficient film | membrane, it is not preferable. However, in order to obtain such a Tg, it is also possible to prepare using two or more kinds of polymers. That is, even if the polymer has a Tg outside the above range, the mass average Tg is preferably within the above range.
The polymer used for the image forming layer preferably has an I / O value of 0.025 or more and 0.5 or less. More preferably, it is 0.05 or more and 0.3 or less. The I / O value is a value obtained by dividing an inorganic group based on an organic conceptual diagram by an organic group. When the I / O value is lower than 0.025, the affinity with an aqueous solvent is poor, and it becomes difficult to apply with an aqueous coating solution. When the I / O value is higher than 0.5, the resulting film is hydrophilic. It is not preferable because the film becomes a thick film, affects the photographic properties with respect to humidity, and remarkably deteriorates photographic performance. The I / O value can be determined by the method described in “Organic Conceptual Diagram-Basics and Applications” (1984 Yoshio Koda, Sankyo Publishing).

  Here, an organic conceptual diagram is an orthogonal coordinate system in which the properties of a compound are divided into an organic group representing a covalent bond and an inorganic group representing an ionic bond, and all organic compounds are named organic and inorganic axes. The inorganic value based on this is determined based on the hydroxyl group based on the inorganicity, that is, the influence of various substituents on the boiling point. If the distance between the boiling point curve of the straight-chain paraffin and the straight-line paraffin is about 100 ° C., the influence of one hydroxyl group is 100. On the other hand, the organic value is based on the number of carbon atoms that represent the methylene group in units of the number of methylene groups in the molecule. The average value of the boiling point increase due to addition of one carbon in the vicinity of 5 to 10 carbon atoms of the linear compound is 20 ° C., and this is a value determined as 20 on the basis of this. The inorganic value and the organic value are determined so as to correspond one-to-one on the graph. The I / O value is calculated from these values.

  Preferred polymer latexes in the present invention are rubbers (for example, SBR resin, isoprene resin, etc.) and acrylic polymer latex. Among these, rubber latex is preferably used for the image forming layer, and acrylic latex is preferably used for the intermediate layer and the protective layer.

《Rubber latex》
More preferable as the polymer latex in the present invention is a polymer obtained by copolymerizing the monomer represented by the general formula (M).

General formula (M)
CH ₂ = CR ⁰¹ -CR ⁰² = CH ₂
In the formula, R ⁰¹ and R ⁰² are groups selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group.

A preferable alkyl group for R ⁰¹ and R ^{02 is} an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 2 carbon atoms. As the halogen atom, a fluorine atom, a chlorine atom or a bromine atom is preferable, and a chlorine atom is more preferable.
As R ⁰¹ and R ⁰² , particularly preferably, both are hydrogen atoms, or one is a hydrogen atom and the other is a methyl group or a chlorine atom.

  Specific examples of the monomer represented by formula (M) in the present invention include 1,3-butadiene, 2-ethyl-1,3-butadiene, 2-n-propyl-1,3-butadiene, 2,3. -Dimethyl-1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-fluoro-1,3-butadiene, 2 , 3-dichloro-1,3-butadiene and 2-cyano-1,3-butadiene.

In the present invention, the other monomer that can be copolymerized with the monomer represented by formula (M) is not particularly limited, and any monomer that can be polymerized by a normal radical polymerization or ionic polymerization method is preferably used. be able to.
The monomers that can be preferably used can be selected independently and freely in combination from the monomer groups (a) to (j) shown below.

-Monomer group (a)-(j)-
(A) Conjugated dienes: 1,3-butadiene, 1,3-pentadiene, 1-phenyl-1,3-butadiene, 1-α-naphthyl-1,3-butadiene, 1-β-naphthyl-1,3 -Butadiene, 1-bromo-1,3-butadiene, 1-chloro-1,3-butadiene, 1,1,2-trichloro-1,3-butadiene, cyclopentadiene, and the like.
(B) Olefin: ethylene, propylene, vinyl chloride, vinylidene chloride, 6-hydroxy-1-hexene, 4-pentenoic acid, methyl 8-nonenoate, vinylsulfonic acid, trimethylvinylsilane, trimethoxyvinylsilane, 1,4- Divinylcyclohexane or 1,2,5-trivinylcyclohexane.
(C) α, β-unsaturated carboxylic acid and salts thereof: acrylic acid, methacrylic acid, itaconic acid, maleic acid, sodium acrylate, ammonium methacrylate, or potassium itaconate.

  (D) α, β-unsaturated carboxylic acid esters: alkyl acrylate (for example, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, or dodecyl) Acrylates, etc.), substituted alkyl acrylates (eg 2-chloroethyl acrylate, benzyl acrylate, 2-cyanoethyl acrylate etc.), alkyl methacrylates (eg methyl Methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, etc.), substituted alkyl methacrylate (for example, 2-hydroxyethyl methacrylate, glycidyl methacrylate). -Glycerol monomethacrylate, 2-acetoxyethyl methacrylate, tetrahydrosulfate Rufuryl methacrylate, 2-methoxyethyl methacrylate, polypropylene glycol monomethacrylate (added mole number of polyoxypropylene = 2 to 100), 3-N, N-dimethylaminopropyl methacrylate Rate, chloro-3-N, N, N-trimethylammoniopropyl methacrylate, 2-carboxyethyl methacrylate, 3-sulfopropyl methacrylate, 4-oxysulfobutyl methacrylate , 3-trimethoxysilylpropyl methacrylate, aryl methacrylate, 2-isocyanatoethyl methacrylate, etc.), derivatives of unsaturated dicarboxylic acids (eg monobutyl maleate, dimethyl maleate, itaconic acid) Monomethyl, dibutyl itaconate, etc.), polyfunctional esters (eg ethylene glycol) Ludiaacrylate, ethylene glycol dimethacrylate, 1,4-cyclohexane diacrylate, pentaerythritol tetramethacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate Trimethylol ethane triacrylate, dipentaerythritol pentamethacrylate, pentaerythritol hexaacrylate, 1,2,4-cyclohexanetetramethacrylate, etc.).

(E) Amides of β-unsaturated carboxylic acid: for example, acrylamide, methacrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-methyl-N-hydroxyethylmethacrylamide, N-tertbutylacrylamide, N- tert-octylmethacrylamide, N-cyclohexylacrylamide, N-phenylacrylamide, N- (2-acetoacetoxyethyl) acrylamide, N-acryloylmorpholine, diacetoneacrylamide, itaconic acid diamide, N-methylmaleimide, 2-acrylamido-methyl Propanesulfonic acid, methylenebisacrylamide, dimethacryloylpiperazine, etc.
(F) Unsaturated nitriles: acrylonitrile, methacrylonitrile and the like.
(G) Styrene and its derivatives: styrene, vinyl toluene, p-tertbutyl styrene, vinyl benzoic acid, methyl vinyl benzoate, α-methyl styrene, p-chloromethyl styrene, vinyl naphthalene, p-hydroxymethyl styrene, p- Styrene sulfonic acid sodium salt, p-styrene sulfinic acid potassium salt, p-aminomethylstyrene, 1,4-divinylbenzene and the like.
(H) Vinyl ethers: methyl vinyl ether, butyl vinyl ether, methoxyethyl vinyl ether, and the like.
(I) Vinyl esters: vinyl acetate, vinyl propionate, vinyl benzoate, vinyl salicylate, vinyl chloroacetate, and the like.
(J) Other polymerizable monomers: N-vinylimidazole, 4-vinylpyridine, N-vinylpyrrolidone, 2-vinyloxazoline, 2-isopropenyloxazoline, divinylsulfone, and the like.

Preference is given to copolymerization with styrene, acrylic acid and / or acrylic esters. Furthermore, a copolymer having styrene and acrylic acid as monomer units is preferable from the viewpoint that the completed hydrophobic polymer can be used as an aqueous dispersion having good dispersion stability.
The copolymerization ratio between the monomer represented by the general formula (M) and another monomer is not particularly limited, but preferably the monomer represented by the general formula (M) is 10% by mass or more and 70% by mass or less. The copolymerization is preferably 15% by mass or more and 65% by mass or less, more preferably 20% by mass or more and 60% by mass or less.

<Description of acrylic polymer latex>
Another preferred polymer latex for use in the present invention is an acrylic latex. The acrylic polymer latex referred to here is a latex containing 20 to 99.9 mol% of acrylic acid esters, methacrylic acid esters, acrylamides, and methacrylamides as a copolymerization monomer component. Particularly preferred are latexes containing acrylic esters and methacrylic esters derived from alcohol components having 2 to 12 carbon atoms, acrylamides derived from amine components having 4 to 12 carbon atoms, and methacrylamides. It is also preferable to use a small amount of an acid component such as acrylic acid, methacrylic acid or itaconic acid or a hydrophilic monomer such as hydroxyethyl (meth) acrylate as a copolymerization component of the latex.

<Specific examples of polymer>
Specific examples of preferred hydrophobic polymers include the following. Below, it represents using a raw material monomer, the numerical value in a parenthesis is the mass%, and molecular weight is a number average molecular weight. When a polyfunctional monomer was used, the concept of molecular weight was not applicable because a crosslinked structure was formed, so it was described as crosslinkable and the molecular weight description was omitted. Tg represents the glass transition temperature.

LP-1; latex of -MMA (55) -EA (42) -MAA (3)-(Tg 39 ° C., I / O value 0.636)
LP-2; -MMA (47) -EA (50) -MAA (3) -latex (Tg 29 ° C., I / O value 0.636)
LP-3; Latex of -MMA (17) -EA (80) -MAA (3)-(Tg-4 ° C, I / O value 0.636)
LP-4; Latex of -EA (97) -MAA (3)-(Tg-20 ° C, I / O value 0.636)
LP-5; Latex of -EA (97) -AA (3)-(Tg-21 ° C, I / O value 0.648)
LP-6; Latex of -EA (90) -AA (10)-(Tg-15 ° C, I / O value 0.761)
LP-7; -MMA (50) -2EHA (35) -St (10) -AA (5) -latex (Tg 34 ° C., I / O value 0.461)
LP-8; Latex of -MMA (30) -2EHA (55) -St (10) -AA (5)-(Tg 3 ° C., I / O value 0.398)
LP-9; latex of MMA (10) -2EHA (75) -St (10) -AA (5)-(Tg-23 ° C, I / O value 0.339)
LP-10; latex of -MMA (60) -BA (36) -AA (4)-(Tg 29 ° C., I / O value 0.581)
LP-11; latex of -MMA (40) -BA (56) -AA (4)-(Tg-2 ° C, I / O value 0.545)
LP-12; latex of -MMA (25) -BA (71) -AA (4)-(Tg-22 ° C, I / O value 0.519)
LP-13; -MMA (42) -BA (56) -AA (2)-(molecular weight 540000, Tg-4 ° C, I / O value 0.530)
LP-14; Latex of -St (40) -BA (55) -AA (5)-(Tg-2 ° C, I / O value 0.319)
LP-15; Latex of -St (25) -BA (70) -AA (5)-(Tg-21 ° C, I / O value 0.377)
LP-16; Latex of -MMA (58) -St (8) -BA (32) -AA (2)-(Tg 34 ° C., I / O value 0.515)
LP-17; latex of MMA (50) -St (8) -BA (35) -HEMA (5) -AA (2)-(Tg 27 ° C., I / O value 0.542)
LP-18; -MMA (42) -St (8) -BA (43) -HEMA (5) -AA (2)-latex (Tg 14 ° C., I / O value 0.528)
LP-19; -MMA (24) -St (8) -BA (61) -HEMA (5) -AA (2)-latex (Tg-12 ° C, I / O value 0.498)
LP-20; latex of MMA (48) -St (8) -BA (27) -HEMA (15) -AA (2)-(Tg 39 ° C., I / O value 0.619)
LP-21; Latex of -EA (96) -AA (4)-(Tg-21 ° C, I / O value 0.664)
LP-22; Latex of -EA (46) -MA (50) -AA (4)-(Tg-4 ° C, I / O value 0.739)
LP-23; -EA (80) -HEMA (16) -AA (4)-latex (Tg-9 ° C, I / O value 0.775)
LP-24; Latex of -EA (86) -HEMA (10) -AA (4)-(Tg-13 ° C, I / O value 0.733)
LP-25; Latex of -St (45) -Bu (52) -MAA (3)-(Tg-26 ° C, I / O value 0.990)
LP-26; Latex of -St (55) -Bu (42) -MAA (3)-(Tg-9 ° C, I / O value 0.105)
LP-27; Latex of -St (60) -Bu (37) -MAA (3)-(Tg 1 ° C, I / O value 0.109)
LP-28; latex of -St (68) -Bu (29) -MAA (3)-(Tg 17 ° C, I / O value 0.114)
LP-29; -St (75) -Bu (22) -MAA (3)-latex (Tg 34 ° C., I / O value 0.119)
LP-30; Latex of -St (40) -BA (58) -AA (2)-(Tg-8.1 ° C, I / O value 0.293)
LP-31; Latex of -St (40) -BA (58) -MAA (2)-(Tg-7.1 ° C, I / O value 0.287)
LP-32; -St (57.2) -BA (27.7) -MMA (8.7) -HEMA (4.8) -AA (1.6) latex (Tg 37.8 ° C, I / O Value 0.269)
LP-33; -St (49.6) -BA (40) -MMA (4) -HEMA (4.8) -AA (1.6) latex (Tg 16.7 ° C., I / O value 0.289) )
LP-34; Latex of -St (80) -2EHA (18) -AA (2)-(Tg 59.7 ° C, I / O value 0.148)
LP-35; -St (70) -2EHA (28) -AA (2)-latex (Tg 40.9 ° C, I / O value 0.164)
LP-36; Latex of -St (10) -2EHA (38) -MMA (50) -AA (2)-(Tg 25.6 ° C, I / O value 0.427)
LP-37; Latex of -St (10) -2EHA (58) -MMA (30) -AA (2)-(Tg-3.9 ° C, I / O value 0.365)
LP-38; Latex of -St (10) -2EHA (78) -MMA (10) -AA (2)-(Tg-28.1 ° C, I / O value 0.308)
LP-39; Latex of -St (20) -2EHA (68) -MMA (10) -AA (2)-(Tg-16.8 ° C, I / O value 0.285)
LP-40; Latex of -St (30) -2EHA (58) -MMA (10) -AA (2)-(Tg-4.4 ° C, I / O value 0.263)
LP-41; -MMA (45) -BA (52) -Itaconic acid (3) -latex (Tg 4 ° C., I / O value 0.560)

LP-42; Latex of -St (62) -Bu (35) -MAA (3)-(crosslinkability, Tg 5 ° C)
LP-43; Latex of -St (68) -Bu (29) -AA (3)-(crosslinkability, Tg 17 ° C.)
LP-44; latex of -St (71) -Bu (26) -AA (3)-(crosslinkability, Tg 24 ° C)
LP-45; latex of -St (70) -Bu (27) -IA (3)-(crosslinkability, Tg 23 ° C)
LP-46; -St (75) -Bu (24) -AA (1)-latex (crosslinkable, Tg 29 ° C)
LP-47; Latex of -St (60) -Bu (35) -DVB (3) -MAA (2)-(crosslinkability, Tg 6 ° C.)
LP-48; -St (70) -Bu (25) -DVB (2) -AA (3)-latex (crosslinkable, Tg 26 ° C)
LP-49; Latex of -St (70.5) -Bu (26.5) -AA (3)-(crosslinkability, Tg 23 ° C.)
LP-50; -St (69.5) -Bu (27.5) -AA (3)-latex (crosslinkable, Tg 20.5 ° C)
LP-51; Latex of -St (61.3) -isoprene (35.5) -AA (3)-(crosslinkability, Tg 17 ° C)
LP-52; Latex of -St (67) -isoprene (28) -Bu (2) -AA (3)-(crosslinkability, Tg 27 ° C.)
LP-53: MMA / BA / St / 2-HEMA / AA = 58/27/8/5/2 (Tg 42 ° C., I / O value 0.552)

  The abbreviations for the above structures represent the following monomers. MMA; methyl methacrylate, EA; ethyl acrylate, MA; methyl acrylate, MAA; methacrylic acid, 2EHA; 2-ethylhexyl acrylate, HEMA; hydroxyethyl methacrylate, St; styrene, Bu; butadiene, AA; acrylic acid, DVB; IA; Itaconic acid.

  The above-mentioned hydrophobic polymer latex is commercially available, and the following polymers can be used. Examples of the acrylic polymer include Sebian A-4635, 4718, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.), etc. Examples of poly (esters) include poly (urethane) such as FINETEX ES650, 611, 675, 850 (above, Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (above, Eastman Chemical). Examples of rubbers include HYDRAN AP10, 20, 30, 40 (manufactured by Dainippon Ink Chemical Co., Ltd.), and examples of rubbers include LACSTAR 7310K, 3307B, 4700H, 7132C (above, Dainippon Ink Chemical Co., Ltd.). (Made by Co., Ltd.), Nipol Lx416, 410, 438C, 2507 (above, Nippon Zeo) As examples of poly (vinyl chloride) such as G351 and G576 (above, manufactured by Nippon Zeon Co., Ltd.), examples of poly (vinylidene chloride) such as L502, L513 (above Examples of poly (olefin) s such as Asahi Kasei Kogyo Co., Ltd. include Chemipearl S120 and SA100 (above, Mitsui Chemicals, Inc.).

As the latex of styrene-butadiene copolymer that is preferably used in the present invention, the above-mentioned LP-42 to LP-50, commercially available LACSTAR-3307B and 7132C (above, manufactured by Dainippon Ink & Chemicals, Inc.) , Nipol Lx416 (manufactured by Zeon Corporation) and the like.
Examples of the latex of the styrene-isoprene copolymer include the aforementioned LP-51 and LP-52.
Examples of the acrylic latex include the above-mentioned LP-53.

  These aqueous dispersions of hydrophobic polymers may be used alone or in combination of two or more as required.

《Binder that can be used together》
If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, or carboxymethyl cellulose may be added to the polymer latex in the present invention. The amount of the hydrophilic polymer added is preferably 30% by mass or less, more preferably 20% by mass or less, based on the solid content of the polymer latex.

<< Coating aids that can be used together >>
A film-forming auxiliary may be added to the polymer latex in the present invention in order to control the minimum film-forming temperature. The film-forming aid is also called a temporary plasticizer, and is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of polymer latex. For example, “Synthetic latex chemistry (written by Soichi Muroi, published by Kobunshi Publishing Co., Ltd.) (1970)) Preferred film-forming aids are the following compounds, but the compounds that can be used in the present invention are not limited to the following specific examples.
Z-1: benzyl alcohol Z-2: 2,2,2,4-trimethylpentanediol-1,3-monoisobutyrate Z-3: 2-dimethylaminoethanol Z-4: diethylene glycol

<Amount applied>
When the polymer latex in the present invention is used for the image forming layer, it is preferably 0.2 g / m ^{2 to} 30 g / m ² , more preferably 1 g / m ^{2 to} 15 g / m ² , and still more preferably 2 g / m ^{2 to} 11 g / m ² . it is in the range of m ^2. The polymer latex solid content / organic silver salt mass ratio in the image forming layer is 1/10 to 10/1, more preferably 1/3 to 5/1, and still more preferably 1/1 to 3/1. is there. Moreover, it is also an image forming layer containing photosensitive silver halide. In such a case, the mass ratio of polymer latex solids / silver halide is preferably 400 to 5, more preferably 200 to 10. is there.

When the polymer latex of the present invention is used for the non-photosensitive intermediate layer, the surface protective layer, or the back layer, the coating amount is preferably 0.1 g / m ² or more and 10 g / m ² or less, more preferably 0. .3g / ^{m 2} or more 7 g / ^{m 2} or less, most preferably 0.5 g / ^{m 2} or more 5 g / ^{m 2} or less.

2) Polymer matting agent In the present invention, it is preferable to add a matting agent to at least one of the surface protective layer and the back layer.
The matting agent used for the back surface is preferably a fine particle matting agent having an average particle size of 1 to 15 μm at 50% by mass or more. More preferably, the average particle size is 3 μm or more and 10 μm or less. The matting agent may be added to any layer on the back surface, but more preferably, the back layer contains at least two non-photosensitive layers, and the matting agent is contained in the outermost non-photosensitive layer.
On the other hand, the matting agent used on the side having the image forming layer has an average particle size of 0.5 μm or more and 10 μm or less, and more preferably an average particle size of 2 μm or more and 6 μm or less. Preferably, the image forming layer has at least one non-photosensitive layer on the side opposite to the support, and the matting agent is contained in the outermost non-photosensitive layer.
The matting agent particles used in the present invention are preferably monodisperse particles, and the size distribution coefficient of variation is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less. Here, the coefficient of variation is a value represented by (standard deviation of particle size) / (average value of particle size) × 100. It is also preferable to use two types of matting agents having a small coefficient of variation and having an average particle size ratio larger than 3.
The matting agent particles used in the present invention are organic particles or inorganic particles, preferably organic particles.

  The matting agent particles used in the present invention are preferably dispersed in advance with a binder and used as a matting agent particle dispersion. Preferably, the binder is gelatin.

<Specific examples of matting agent particles>
Examples of matting agents preferably used in the present invention are shown below, but the present invention is not limited to the following compounds.

  The polymer composition is preferably a vinyl polymer, for example, those mainly composed of polystyrene, polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, etc., but as a good example of a crosslinked polymer latex, Examples thereof include styrene-divinylbenzene copolymer and poly (ethylene glycol dimethacrylate co-methyl methacrylate).

These products are also commercially available, and commercially available products can be used.
Examples of matting agents preferably used in the present invention are shown below, but the present invention is not limited to the following compounds.
M-1: Polyethylene particles (Flow beads LE-1080, manufactured by Sumitomo Seika Co., Ltd.)
M-2: Polyethylene particles (Flow beads EA-209, manufactured by Sumitomo Seika Co., Ltd.)
M-3: Polyethylene particles (Flow beads HE-3040, manufactured by Sumitomo Seika Co., Ltd.)
M-4: Silicone particles (specific gravity 0.97)
M-5: Silicone particles (specific gravity 1.00) (E701 manufactured by Toray Dow Silicone Co., Ltd.)
M-6: Silicone particles (specific gravity 1.03)
M-7: Polystyrene particles (specific gravity 1.05) (SB-6 manufactured by Sekisui Plastics Co., Ltd.)
M-8: Poly (St / MAA = 97/3) copolymer particles M-9: Poly (St / MAA = 90/10) copolymer particles M-10: Poly (St / MMA / MAA = 50 / 40/10) Copolymer particles M-11: Cross-linked polyethylene particles (specific gravity 0.92)
M-12: Cross-linked polyethylene particles (specific gravity 0.95)
M-13: Cross-linked polyethylene particles (specific gravity 0.98)
M-14: Cross-linked silicone particles (specific gravity 0.99)
M-15: Cross-linked silicone particles (specific gravity 1.02)
M-16: Cross-linked silicone particles (specific gravity 1.04)
M-17: Poly (St / DVB = 90/10) particles (SX-713, manufactured by Soken Chemical Co., Ltd.)
M-18: Poly (St / DVB = 80/20) particles (SX-713, manufactured by Soken Chemical Co., Ltd.)
M-19: Poly (St / DVB = 70/30) particles (SX-713, manufactured by Soken Chemical Co., Ltd.)
M-20: Poly (St / MAA / DVB = 87/3/10) copolymer particles (SX-713α, manufactured by Soken Chemical Co., Ltd.)
M-21: Poly (St / MAA / DVB = 80/10/10) copolymer particles (SX-713α, manufactured by Soken Chemical Co., Ltd.)
M-22: Poly (St / MMA / MAA / DVB = 40/40/10/10) copolymer particles M-23: PMMA particles (MX-675, manufactured by Soken Chemical Co., Ltd.)

<Amount of matting agent particles applied>
The coating amount of the matting agent particles on the back surface is such that the ratio of the surface glossiness of the surface having the image forming layer to the surface glossiness of the surface having the back layer is 1.1 or more, preferably 1.4 or more. The amount is sufficient. Addition amount varies depending particle size and size distribution, but approximately ^{1mg / m 2 ~400mg / m 2} , preferably from ^{10mg / m 2 ~200mg / m 2} .
On the other hand, the coating amount of the matting agent particles on the surface of the image forming layer is preferably a minimum amount necessary to ensure adhesion failure and slipperiness on the surface, and the surface glossiness is maintained at 70 or more, preferably 90 or more. Is kept within a possible range. The coating amount of the matting agent particles of the image forming layer surface is approximately ^{1mg / m 2 ~400mg / m 2} , preferably from ^{10mg / m 2 ~200mg / m 2} .

  When the matting agent is contained on the image forming layer surface side, the matting agent content is generally adjusted so as not to cause stardust failure, and preferably the Beck smoothness is 500 seconds or more and 10,000 seconds or less. And more preferably 500 seconds or more and 2,000 seconds or less. When the back layer contains a matting agent, it is preferable that the Beck smoothness is 2000 seconds or less and 10 seconds or more, and more preferably 1500 seconds or less and 50 seconds or more. The Beck smoothness in this specification is obtained from JIS P8119 and TAPPI T479.

In the method of dispersing the matting agent particles, an aqueous medium containing a binder is previously present as a dispersion aid in an aqueous solvent, and known high-speed stirring means (for example, a disperser emulsifier, a homomixer, a turbine mixer, or It can be mechanically dispersed using a homogenizer) or an ultrasonic emulsifier. In dispersing, in order to suppress foaming, means for dispersing in a reduced pressure state rather than atmospheric pressure can be used in combination. The dispersion aid to be used is generally dissolved in an aqueous medium in advance and then the matting agent particles are generally added. However, in the case of an organic synthetic compound, the matting agent particles were previously obtained by polymerization. It may be added as an aqueous dispersion (without passing through a drying step). The dispersion aid can also be added to the dispersion during dispersion. Moreover, it can also add to a dispersion liquid for stabilization of the physical property after dispersion | distribution. In either case, it is common that a solvent (for example, water / alcohol) coexists. You may control pH by a suitable pH adjuster before and after dispersion | distribution or during dispersion | distribution.
In addition to the mechanical dispersion means, the stability of the dispersed matting agent particles may be increased by controlling the pH. In addition, a very small amount of a low-boiling organic solvent may be used for dispersion, and the organic solvent is usually removed after the formation of fine particles.
The prepared dispersion is stored with stirring for the purpose of suppressing sedimentation of the matting agent particles during storage, or stored in a highly viscous state (for example, using gelatin to make a jelly state). You can also. Moreover, it is preferable to add a preservative for the purpose of preventing the propagation of various germs during storage.
The binder is preferably added and dispersed so as to be 5% by mass or more and 300% by mass or less with respect to the matting agent particles. More preferably, it adds so that it may become 10 mass% or more and 200 mass or less.

(Non-photosensitive organic silver salt)
1) Composition The organic silver salt that can be used in the present invention is relatively stable to light, but is heated to 80 ° C. or higher in the presence of exposed photosensitive silver halide and a reducing agent. In this case, the silver salt functions as a silver ion supplier to form a silver image. The organic silver salt may be any organic substance that can supply silver ions that can be reduced by a reducing agent. As for such non-photosensitive organic silver salt, paragraph numbers 0048 to 0049 of JP-A-10-62899, page 18 line 24 to page 19 line 37 of European Patent Publication No. 0803764A1, European Patent Publication. No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, and the like. Silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30 carbon atoms, preferably 15 to 28 carbon atoms) are preferred. Preferred examples of the fatty acid silver salt include silver lignocerate, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver erucate and the like. Including a mixture of In the present invention, among these fatty acid silvers, the silver behenate content is preferably 50 mol% to 100 mol%, more preferably 85 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%. The following fatty acid silver is preferably used. Furthermore, it is preferable to use fatty acid silver having a silver erucate content of 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0.1 mol% or less.

  Moreover, it is preferable that silver stearate content rate is 1 mol% or less. By setting the silver stearate content to 1 mol% or less, a silver salt of an organic acid having a low Dmin, high sensitivity and excellent image storage stability can be obtained. As said silver stearate content rate, 0.5 mol% or less is preferable and it is especially preferable not to contain substantially.

  Furthermore, when silver arachidate is included as the silver salt of the organic acid, the silver arachidate content is 6 mol% or less to obtain a low Dmin and an organic acid silver salt excellent in image storability. It is preferable at a point and it is still more preferable that it is 3 mol% or less.

2) Shape The shape of the organic silver salt that can be used in the present invention is not particularly limited, and may be any of a needle shape, a rod shape, a flat plate shape, and a flake shape.
In the present invention, scaly organic silver salts are preferred. Also, short needle-shaped, rectangular parallelepiped, cubic or potato-shaped amorphous particles having a major axis / uniaxial length ratio of 5 or less are preferably used. These organic silver particles have a feature that the fog at the time of heat development is less than that of long needle-like particles in which the ratio of the long axis to the single axis exceeds 5. In particular, particles having a major axis / uniaxial ratio of 3 or less are preferable because the mechanical stability of the coating film is improved. In the present specification, the scaly organic silver salt is defined as follows. The organic acid silver salt was observed with an electron microscope, the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped were designated a, b, and c from the shortest side (c was the same as b). Then, the shorter numerical values a and b are calculated, and x is obtained as follows.
x = b / a

  In this way, x is obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of x (average) ≧ 1.5 are defined as flakes. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 15 ≧ x (average) ≧ 1.5. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

  In the flake shaped particle, a can be regarded as a thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 μm or more and 0.3 μm or less, and more preferably 0.1 μm or more and 0.23 μm or less. The average c / b is preferably 1 or more and 9 or less, more preferably 1 or more and 6 or less, still more preferably 1 or more and 4 or less, and most preferably 1 or more and 3 or less.

By setting the equivalent sphere diameter to 0.05 μm or more and 1 μm or less, aggregation is hardly caused in the photothermographic material, and image storability is improved. The sphere equivalent diameter is preferably 0.1 μm or more and 1 μm or less. In the present invention, the method for measuring the equivalent sphere diameter is obtained by directly photographing a sample using an electron microscope and then image-processing the negative.
In the flake shaped particles, the spherical equivalent diameter / a of the particles is defined as the aspect ratio. The aspect ratio of the flake shaped particles is preferably 1.1 or more and 30 or less, and preferably 1.1 or more and 15 or less, from the viewpoint of preventing aggregation in the photothermographic material and improving the image storage stability. More preferred.

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

3) Preparation Known methods and the like can be applied to the production and dispersion method of the organic acid silver used in the present invention. For example, the above-mentioned JP-A-10-62899, European Patent Publication No. 0803763A1, European Patent Publication No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, JP-A-2001-163889, 2001-163890, 2001-163828, 2001-33907, 2001-188313, 2001-83651, 2002-6442, 2002-49117, 2002-31870, 2002-107868 You can refer to the issue.

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

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

4) Addition Amount organic silver salt in the invention can be used in a desired amount, preferably 0.1g ^{/ m 2} ~3.0g ^/ m 2 as the total amount of coated silver halide silver was also included, and more preferably 0 ^{.5g / m 2 ~2.0g / m 2} , more preferably from ^{0.8g / m 2 ~1.7g / m 2} . In particular, in order to improve image storability, the total coated silver amount is preferably 1.5 g / m ² or less, more preferably 1.3 g / m ² or less. If the preferred reducing agent of the present invention is used, a sufficient image density can be obtained even with such a low silver amount.

(Reducing agent)
The photothermographic material of the present invention preferably contains a heat developer that is a reducing agent for silver ions. The reducing agent may be any substance (preferably an organic substance) that reduces silver ions to metallic silver. Examples of such reducing agents are described in JP-A No. 11-65021, paragraphs 0043 to 0045, and European Patent Publication No. 0803764A1, page 7, line 34 to page 18, line 12.

  In the present invention, the reducing agent is preferably a so-called hindered phenol-based reducing agent or bisphenol-based reducing agent having a substituent at the ortho position of the phenolic hydroxyl group, and more preferably a compound represented by the following general formula (R).

In the general formula (R), R ¹¹ and R ¹¹ ′ each independently represent an alkyl group having 1 to 20 carbon atoms. R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent that can be substituted on the benzene ring. L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring.

The general formula (R) will be described in detail.
1) R ¹¹ and R ¹¹ '
R ¹¹ and R ¹¹ ′ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the substituent of the alkyl group is not particularly limited, but is preferably an aryl group, a hydroxy group, Examples include alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, acylamino groups, sulfonamido groups, sulfonyl groups, phosphoryl groups, acyl groups, carbamoyl groups, ester groups, ureido groups, urethane groups, and halogen atoms.

2) R ¹² and R ¹² ′, X ¹ and X ¹ ′
R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent capable of substituting for a benzene ring, and X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group capable of substituting for a benzene ring. Preferred examples of the group that can be substituted on the benzene ring include an alkyl group, an aryl group, a halogen atom, an alkoxy group, and an acylamino group.

3) L
L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and the alkyl group may have a substituent. Specific examples of the unsubstituted alkyl group for R ¹³ are methyl group, ethyl group, propyl group, butyl group, heptyl group, undecyl group, isopropyl group, 1-ethylpentyl group, 2,4,4-trimethylpentyl group, cyclohexyl group. Group, 2,4-dimethyl-3-cyclohexenyl group, 3,5-dimethyl-3-cyclohexenyl group and the like. Examples of the substituent of the alkyl group are the same as the substituent of R ¹¹ , and are a halogen atom, alkoxy group, alkylthio group, aryloxy group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, oxycarbonyl group, A carbamoyl group, a sulfamoyl group, etc. are mentioned.

4) Preferred substituents R ¹¹ and R ¹¹ ′ are preferably primary, secondary or tertiary alkyl groups having 1 to 15 carbon atoms, specifically methyl, isopropyl, t-butyl, t -Amyl group, t-octyl group, cyclohexyl group, cyclopentyl group, 1-methylcyclohexyl group, 1-methylcyclopropyl group and the like. R ¹¹ and R ¹¹ ′ are more preferably an alkyl group having 1 to 4 carbon atoms, and among them, a methyl group, a t-butyl group, a t-amyl group, or a 1-methylcyclohexyl group is more preferable, and a methyl group, t- A butyl group is most preferred.

R ¹² and R ¹² ′ are preferably an alkyl group having 1 to 20 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a t-butyl group, a t-amyl group, a cyclohexyl group. Group, 1-methylcyclohexyl group, benzyl group, methoxymethyl group, methoxyethyl group and the like. More preferred are a methyl group, an ethyl group, a propyl group, an isopropyl group, or a t-butyl group, and particularly preferred are a methyl group and an ethyl group.
X ¹ and X ¹ ′ are preferably a hydrogen atom, a halogen atom, or an alkyl group, and more preferably a hydrogen atom.

L is preferably a —CHR ¹³ — group.
R ¹³ is preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms. As the alkyl group, a cyclic alkyl group is also preferably used in addition to a chain alkyl group. Moreover, what has a C = C bond in these alkyl groups can also be used preferably. Examples of the alkyl group include a methyl group, ethyl group, propyl group, isopropyl group, 2,4,4-trimethylpentyl group, cyclohexyl group, 2,4-dimethyl-3-cyclohexenyl group, or 3,5-dimethyl-3. -A cyclohexenyl group and the like are preferable. R ¹³ is particularly preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a 2,4-dimethyl-3-cyclohexenyl group.

When R ¹¹ and R ¹¹ ′ are tertiary alkyl groups and R ¹² and R ¹² ′ are methyl groups, R ¹³ is a primary or secondary alkyl group having 1 to 8 carbon atoms (methyl group, ethyl group, propyl group). Group, isopropyl group, or 2,4-dimethyl-3-cyclohexenyl group).
When R ¹¹ and R ¹¹ ′ are tertiary alkyl groups and R ¹² and R ¹² ′ are alkyl groups other than methyl groups, R ¹³ is preferably a hydrogen atom.
When R ¹¹ and R ¹¹ ′ are not a tertiary alkyl group, R ¹³ is preferably a hydrogen atom or a secondary alkyl group, and particularly preferably a secondary alkyl group. Preferred groups as the secondary alkyl group for R ¹³ are isopropyl group and 2,4-dimethyl-3-cyclohexenyl group.
The reducing agent has different heat developability, developed silver tone, and the like depending on the combination of R ¹¹ , R ¹¹ ′, R ¹² , R ¹² ′ and R ¹³ . Since these can be prepared by combining two or more reducing agents, it is preferable to use a combination of two or more depending on the purpose.

  Although the specific example of the reducing agent of this invention including the compound represented by general formula (R) of this invention below is shown, this invention is not limited to these.

  Examples of preferable reducing agents of the present invention other than the above are the compounds described in JP-A Nos. 2001-188314, 2001-209145, 2001-350235, 2002-156727, and EP1278101A2.

The addition amount of the reducing agent is preferably a ^{0.1g / m 2 ~3.0g / m 2} , more preferably ^{0.2g / m 2 ~1.5g / m 2} , more preferably 0 .3 g / m ^{2 to} 1.0 g / m ² . 5 mol% to 50 mol% is preferably contained with respect to 1 mol of silver on the surface having the image forming layer, more preferably 8 mol% to 30 mol%, and 10 mol% to 20 mol%. More preferably. The reducing agent is preferably contained in the image forming layer.

The reducing agent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form or a solid fine particle dispersion form, and may be contained in the photothermographic material.
Well-known emulsifying dispersion methods include dissolving oil using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, or an auxiliary solvent such as ethyl acetate or cyclohexanone, and mechanically dispersing the emulsified dispersion. The method of producing is mentioned.

  Further, as a solid fine particle dispersion method, a reducing agent powder is dispersed in an appropriate solvent such as water by a ball mill, a colloid mill, a vibration ball mill, a sand mill, a jet mill, a roller mill, or an ultrasonic wave to produce a solid dispersion. A method is mentioned. In this case, a protective colloid (for example, polyvinyl alcohol) or a surfactant (for example, an anionic surfactant such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used. Good. In the mills, beads such as zirconia are usually used as a dispersion medium, and Zr and the like eluted from these beads may be mixed in the dispersion. Although it depends on the dispersion conditions, it is usually in the range of 1 ppm to 1000 ppm. If the Zr content in the light-sensitive material is 0.5 mg or less per 1 g of silver, there is no practical problem.

  The aqueous dispersion preferably contains a preservative (for example, benzoisothiazolinone sodium salt).

  Particularly preferred is a solid particle dispersion method of a reducing agent, and it is preferable to add fine particles having an average particle size of 0.01 μm to 10 μm, preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 2 μm. In the present application, it is preferable to use other solid dispersions dispersed in a particle size within this range.

(Photosensitive silver halide)
1) Halogen composition The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and is silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide, or iodide. Silver can be used. Of these, silver bromide, silver iodobromide and silver iodide are preferred. The distribution of the halogen composition in the grains may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Further, silver halide grains having a core / shell structure can be preferably used. A preferable structure is a 2- to 5-fold structure, and more preferably 2- to 4-fold core / shell particles can be used. A technique for localizing silver bromide or silver iodide on the surface of silver chloride, silver bromide or silver chlorobromide grains can also be preferably used.

2) Grain Forming Methods Methods for forming photosensitive silver halide are well known in the art and are described, for example, in Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458. In particular, a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound into gelatin or another polymer solution, and then mixed with an organic silver salt. Use the method. In addition, the method described in paragraph Nos. 0217 to 0224 of JP-A No. 11-119374, and the methods described in JP-A Nos. 11-352627 and 2000-347335 are also preferable.

3) Grain size The grain size of the photosensitive silver halide is preferably small for the purpose of reducing the cloudiness after image formation, specifically 0.20 μm or less, more preferably 0.01 μm or more and 0.15 μm or less. More preferably, it is 0.02 μm or more and 0.12 μm or less. The grain size here means the diameter when converted into a circular image having the same area as the projected area of silver halide grains (in the case of tabular grains, the projected area of the main plane).

4) Grain shape Examples of the shape of the silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-like grains, and potato grains. In the present invention, cubic grains are particularly preferred. Grains with rounded corners of silver halide grains can also be preferably used. The surface index (Miller index) of the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the [100] plane having high spectral sensitization efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The proportion is preferably 50% or more, more preferably 65% or more, and further preferably 80% or more. The ratio of the Miller index [100] plane is determined by T.T. Tani; Imaging Sci. 29, 165 (1985).

5) Heavy Metal The photosensitive silver halide grain of the present invention can contain a metal or metal complex of Group 6 to Group 13 of the Periodic Table (showing Groups 1 to 18). Preferably, it is a Group 6 to Group 10 metal or metal complex. As the central metal of Group 6 to Group 10 metal or metal complex of the periodic table, iron, rhodium, ruthenium, and iridium are preferable. One kind of these metal complexes may be used, or two or more kinds of complexes of the same metal and different metals may be used in combination. The preferred content is in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol per mol of silver. These heavy metals and metal complexes and methods of adding them are described in JP-A-7-225449, JP-A-11-65021, paragraphs 0018 to 0024, and JP-A-11-119374, paragraphs 0227 to 0240.

In the present invention, silver halide grains in which a hexacyano metal complex is present on the outermost surface of the grains are preferred. Examples of the hexacyano metal complex include [Fe (CN) ₆ ] ⁴⁻ , [Fe (CN) ₆ ] ³⁻ , [Ru (CN) ₆ ] ⁴⁻ , [Os (CN) ₆ ] ⁴⁻ , [Co ( CN) ₆ ] ³⁻ , [Rh (CN) ₆ ] ³⁻ , [Ir (CN) ₆ ] ³⁻ , [Cr (CN) ₆ ] ³⁻ , and [Re (CN) ₆ ] ^3−. It is done.
In the present invention, a hexacyano Fe complex is preferred.

  The hexacyano metal complex is present in the form of ions in aqueous solution, so the counter cation is not important, but it is easy to mix with water and is suitable for precipitation of silver halide emulsions. Sodium ion, potassium ion, rubidium It is preferable to use alkali metal ions such as ions, cesium ions and lithium ions, ammonium ions, alkylammonium ions (for example, tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, or tetra (n-butyl) ammonium ions). .

  In addition to water, the hexacyano metal complex is miscible with a mixed solvent or gelatin with an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters, or amides). Can be added.

The addition amount of the hexacyano metal complex is preferably 1 × 10 ⁻⁵ mol or more and 1 × 10 ⁻² mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻³ mol or less per mol of silver.

  In order for the hexacyano metal complex to be present on the outermost surface of the silver halide grain, the chalcogen sensitization of sulfur sensitization, selenium sensitization and tellurium sensitization is completed after the addition of the aqueous silver nitrate solution used for grain formation. It is added directly before the completion of the preparation step before the chemical sensitization step for performing noble metal sensitization such as sensitization and gold sensitization, during the washing step, during the dispersion step, or before the chemical sensitization step. In order to prevent the silver halide fine grains from growing, it is preferable to add the hexacyano metal complex immediately after the grain formation, and it is preferable to add it before the completion of the preparation step.

  The addition of the hexacyano metal complex may be started after adding 96% by mass of the total amount of silver nitrate to be added to form grains, more preferably starting after adding 98% by mass, The addition of 99% by mass is particularly preferable.

  When these hexacyanometal complexes are added after the addition of the aqueous silver nitrate solution just before the completion of grain formation, they can be adsorbed on the outermost surface of the silver halide grains, and most of them form slightly soluble salts with silver ions on the grain surface. To do. Since this silver salt of hexacyanoiron (II) is a less soluble salt than AgI, it is possible to prevent re-dissolution by fine particles and to produce silver halide fine particles having a small particle size. .

Further, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a silver salt emulsion desalting method and a chemical sensitization method which can be contained in the silver halide grains used in the present invention, JP-A-11- No. 84574, paragraph numbers 0046 to 0050, JP-A No. 11-65021, paragraph numbers 0025 to 0031, and JP-A No. 11-119374, paragraph numbers 0242 to 0250.

6) Gelatin As the gelatin contained in the photosensitive silver halide emulsion used in the present invention, various gelatins can be used. It is necessary to keep the dispersion state of the photosensitive silver halide emulsion in the organic silver salt-containing coating solution, and gelatin having a molecular weight of 10,000 to 1,000,000 is preferably used. It is also preferable to phthalate the gelatin substituent. These gelatins may be used at the time of grain formation or at the time of dispersion after desalting, but are preferably used at the time of grain formation.

7) Sensitizing Dye Sensitizing dyes applicable to the present invention are those that can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed on silver halide grains, and are suitable for the spectral characteristics of the exposure light source. Sensitizing dyes with sensitivity can be advantageously selected. Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A No. 11-65021, compounds represented by formula (II) of JP-A No. 10-186572, and formulas (I of JP-A No. 11-119374) ) And the dye described in Example 5 of U.S. Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59-48753. No. 19, page 38 to line 20, page 35 of European Patent Publication No. 0803764A1, JP 2001-272747, JP 2001-290238, JP 2002-23306, etc. It is described in. These sensitizing dyes may be used alone or in combination of two or more. In the present invention, the time when the sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from desalting to the end of chemical ripening.
The addition amount of the sensitizing dye in the present invention can be set to a desired amount in accordance with sensitivity and fogging performance, but is preferably 10 ⁻⁶ mol to 1 mol per mol of silver halide in the image forming layer, and Preferably it is 10 ^<-4> mol-10 < ^{-1 >} mol.

In the present invention, a supersensitizer can be used to improve spectral sensitization efficiency.
As the supersensitizer used in the present invention, European Patent Publication No. 587,338, US Pat. Nos. 3,877,943, 4,873,184, JP-A-5-341432, 11- 109547, 10-111543, etc. are mentioned.

8) Chemical Sensitization The photosensitive silver halide grain in the invention is preferably chemically sensitized by sulfur sensitizing method, selenium sensitizing method or tellurium sensitizing method. As the compound preferably used in the sulfur sensitization method, selenium sensitization method, and tellurium sensitization method, known compounds such as compounds described in JP-A-7-128768 can be used. In the present invention, tellurium sensitization is particularly preferred. The compounds described in the literature described in paragraph No. 0030 of JP-A-11-65021, and the general formulas (II), (III), (IV) described in JP-A-5-313284 The compound shown by is more preferable.

  The photosensitive silver halide grains in the present invention are preferably chemically sensitized by gold sensitization alone or in combination with the chalcogen sensitization described above. As the gold sensitizer, the valence of gold is preferably +1 or +3, and the gold sensitizer is preferably a gold compound that is usually used. Typical examples include chloroauric acid, bromoauric acid, potassium chloroaurate, potassium bromoaurate, auric trichloride, potassium auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, or pyridyltrichloro. Gold or the like is preferable. Further, gold sensitizers described in US Pat. No. 5,858,637 and JP-A No. 2002-278016 are also preferably used.

In the present invention, chemical sensitization can be performed at any time after particle formation and before coating. After desalting, (1) before spectral sensitization, (2) simultaneously with spectral sensitization, (3) spectral After sensitization, there may be (4) immediately before application.
The amount of sulfur, selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but preferably 10 ⁻⁸ mol to 10 ⁻² mol per mol of silver halide. Is about 10 ⁻⁷ mol to 10 ⁻³ mol.
The addition amount of the gold sensitizer varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol to 10 ⁻³ mol, more preferably 10 ⁻⁶ mol to 5 × 10 ⁻⁴ mol per mol of silver halide. .
The conditions for chemical sensitization in the present invention are not particularly limited, but the pH is 5 to 8, the pAg is 6 to 11, and the temperature is about 40 ° C to 95 ° C.
A thiosulfonic acid compound may be added to the silver halide emulsion used in the present invention by the method described in European Patent Publication No. 293,917.

  A reducing agent is preferably used for the photosensitive silver halide grains in the present invention. As specific compounds for the reduction sensitization, ascorbic acid and thiourea dioxide are preferable, and stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, or polyamine compounds may be used. preferable. The reduction sensitizer may be added at any stage in the photosensitive emulsion production process from crystal growth to the preparation process immediately before coating. Further, reduction sensitization is preferred by ripening while maintaining the pH of the emulsion at 7 or higher or pAg at 8.3 or lower, and reduction sensitization is achieved by introducing a single addition portion of silver ions during grain formation. It is also preferable to do.

9) Compound in which 1-electron oxidant produced by 1-electron oxidation can emit 1 electron or more electrons In the photothermographic material of the present invention, 1-electron oxidant produced by 1-electron oxidation is 1 electron or 1 electron or more. It is preferable to contain a compound capable of emitting more electrons. The compound can be used alone or in combination with the above-mentioned various chemical sensitizers, and can increase the sensitivity of silver halide.

In the present invention, the one-electron oxidant produced by one-electron oxidation contained in the photothermographic material is a compound selected from the following types 1 and 2 that can emit one electron or more.
(Type 1)
A compound in which a one-electron oxidant produced by one-electron oxidation can further emit one or more electrons with a subsequent bond cleavage reaction.
(Type 2)
A compound capable of emitting one or more electrons after a one-electron oxidant produced by one-electron oxidation undergoes a subsequent bond formation reaction.

First, the compound of type 1 will be described.
JP-A-9-211769 (specific example: page 28) is a compound of type 1 that can be further released by one-electron oxidant produced by one-electron oxidation with subsequent bond cleavage reaction. Compounds PMT-1 to S-37 described in Table E and Table F on page 32), JP-A-9-211774, JP-A-11-95355 (specific examples: compounds INV1-36), JP 2001-500996 No. (specific examples: compounds 1 to 74, 80 to 87, 92 to 122), US Pat. No. 5,747,235, US Pat. No. 5,747,236, European Patent No. 786692A1 (specific examples: compounds INV 1 to 35) "One-photon two-electron sensitizer" or "deprotonated electric child" described in European Patent No. 893732A1, US Patent No. 6,054,260, US Patent No. 5,994,051, etc. It referred compounds as sensitizers ". The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

  In addition, as a compound of type 1 that can be emitted by one-electron oxidant produced by one-electron oxidation and further releasing one electron or more with a subsequent bond cleavage reaction, a compound represented by the general formula (1) ( General formula (1) described in JP-A-2003-114487), general formula (2) (synonymous with general formula (2) described in JP-A-2003-114487), general formula (3) General formula (1) described in 2003-114488), general formula (4) (synonymous with general formula (2) described in Japanese Patent Application Laid-Open No. 2003-114488), general formula (5) (Japanese Patent Application Laid-Open No. 2003-114488). 114488 (synonymous with general formula (3)), general formula (6) (synonymous with general formula (1) described in JP-A-2003-75950), and general formula (7) (JP-A-2003-75950). Synonymous with general formula (2) described in , General formula (8) (synonymous with general formula (1) described in JP-A-2004-239934), or chemical reaction formula (1) (synonymous with chemical reaction formula (1) described in JP-A-2004-245929) Among the compounds capable of causing the reaction represented by (), a compound represented by the general formula (9) (synonymous with the general formula (3) described in JP-A-2004-245929) can be given. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the formula, RED ₁ and RED ₂ represent a reducing group. R ₁ represents a non-metallic atomic group capable of forming a cyclic structure corresponding to a tetrahydro form of a 5-membered or 6-membered aromatic ring (including an aromatic heterocycle) or an octahydro form together with the carbon atom (C) and RED _1. To express. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. L ₁ represents a leaving group. ED represents an electron donating group. Z ₁ represents an atomic group capable of forming a 6-membered ring with a nitrogen atom and two carbon atoms of a benzene ring. X ₁ represents a substituent, and m 1 represents an integer of 0 to 3. Z ₂ represents —CR ₁₁ R ₁₂ —, —NR ₁₃ —, or —O—.
R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent. R ₁₃ represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. X ₁ represents an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylamino group, an arylamino group, or a heterocyclic amino group. L ₂ represents a carboxy group or a salt thereof, or a hydrogen atom. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

Next, the type 2 compound will be described.
A compound that can be emitted by one-electron oxidant produced by one-electron oxidation with a type 2 compound and further generating one or more electrons with a subsequent bond formation reaction is represented by general formula (10) A compound capable of causing a reaction represented by the general formula (1) described in 2003-140287) and the chemical reaction formula (1) (synonymous with the chemical reaction formula (1) described in JP-A-2004-245929). And a compound represented by the general formula (11) (synonymous with the general formula (2) described in JP-A No. 2004-245929). The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the formula, X represents a reducing group that is one-electron oxidized. Y reacts with a one-electron oxidant formed by one-electron oxidation of X to form a new bond, a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site, or a benzo The reactive group containing the non-aromatic heterocyclic part of a condensed ring is represented. L ₂ represents a linking group for linking X and Y. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

  Of the compounds of types 1 and 2, “a compound having an adsorptive group to silver halide in the molecule” or “a compound having a partial structure of a spectral sensitizing dye in the molecule” is preferable. Typical examples of the adsorptive group to silver halide include those described in JP-A No. 2003-156823, page 16, right line 1 to page 17, right line 12. The partial structure of the spectral sensitizing dye is a structure described on page 17, right line 34 to page 18, left line 6 of the same specification.

  More preferably, the compound of type 1 or 2 is “a compound having at least one adsorptive group to silver halide in the molecule”. More preferred is “a compound having two or more adsorptive groups to silver halide in the same molecule”. When two or more adsorptive groups are present in a single molecule, these adsorptive groups may be the same or different.

  The adsorptive group is preferably a mercapto-substituted nitrogen-containing heterocyclic group (for example, 2-mercaptothiadiazole group, 3-mercapto-1,2,4-triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4). -Oxadiazole group, 2-mercaptobenzoxazole group, 2-mercaptobenzthiazole group, or 1,5-dimethyl-1,2,4-triazolium-3-thiolate group), or imino silver (> NAg) A nitrogen-containing heterocyclic group having a —NH— group that can be formed as a heterocyclic partial structure (for example, a benzotriazole group, a benzimidazole group, or an indazole group). Particularly preferred are a 5-mercaptotetrazole group, a 3-mercapto-1,2,4-triazole group, and a benzotriazole group, and most preferred are a 3-mercapto-1,2,4-triazole group, and 5 -Mercaptotetrazole group.

  It is also particularly preferred that the adsorptive group has two or more mercapto groups as a partial structure in the molecule. Here, the mercapto group (—SH) may be a thione group if it can be tautomerized. Preferred examples of the adsorptive group having two or more mercapto groups as a partial structure (such as a dimercapto-substituted nitrogen-containing heterocyclic group) include 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, and 3 , 5-dimercapto-1,2,4-triazole group.

  A quaternary salt structure of nitrogen or phosphorus is also preferably used as the adsorptive group. Specific examples of the quaternary salt structure of nitrogen include an ammonio group (such as a trialkylammonio group, a dialkylaryl (or heteroaryl) ammonio group, an alkyldiaryl (or heteroaryl) ammonio group) or a quaternized nitrogen atom. A group containing a nitrogen-containing heterocyclic group containing The quaternary salt structure of phosphorus includes a phosphonio group (trialkyl phosphonio group, dialkylaryl (or heteroaryl) phosphonio group, alkyldiaryl (or heteroaryl) phosphonio group, triaryl (or heteroaryl) phosphonio group, etc.) Is mentioned. More preferably, a quaternary salt structure of nitrogen is used, and more preferably a 5-membered or 6-membered nitrogen-containing aromatic heterocyclic group containing a quaternized nitrogen atom is used. Particularly preferably, a pyridinio group, a quinolinio group, or an isoquinolinio group is used. These nitrogen-containing heterocyclic groups containing a quaternized nitrogen atom may have an arbitrary substituent.

Examples of counter anions of quaternary salts include halogen ions, carboxylate ions, sulfonate ions, sulfate ions, perchlorate ions, carbonate ions, nitrate ions, BF ₄ ⁻ , PF ₆ ⁻ , Ph ₄ B ^{− and the} like. Can be mentioned. When a group having a negative charge in a carboxylate group or the like is present in the molecule, an inner salt may be formed together with the group. As the counter anion not present in the molecule, a chlorine ion, a bromo ion or a methanesulfonate ion is particularly preferable.

  A preferred structure of the compound represented by types 1 and 2 having a quaternary salt structure of nitrogen or phosphorus as the adsorptive group is represented by the general formula (X).

Formula _{(X) (P-Q 1} -) i -R (-Q 2 -S) j

In the general formula (X), P and R each independently represent a quaternary salt structure of nitrogen or phosphorus that is not a partial structure of a sensitizing dye. Q ₁ and Q ₂ each independently represent a linking group. Specifically, a single bond, an alkylene group, an arylene group, a heterocyclic group, —O—, —S—, —NR _N —, —C (= O) —, —SO ₂ —, —SO—, —P (═O) — represents a group consisting of a single group or a combination of these groups. Here, _RN represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. S is a residue obtained by removing one atom from a compound represented by type (1) or (2). i and j are integers of 1 or more, and i + j is selected from the range of 2-6. Preferably, i is 1 to 3, and j is 1 to 2, more preferably i is 1 or 2, and j is 1, and particularly preferably i is 1 and j is 1. The compound represented by the general formula (X) preferably has a total carbon number of 10 to 100. More preferably, it is 10-70, More preferably, it is 11-60, Most preferably, it is 12-50.

  The compounds of type 1 and type 2 in the present invention may be used at any time during the preparation of the photosensitive silver halide emulsion and during the process of producing the photothermographic material. For example, at the time of photosensitive silver halide grain formation, desalting step, chemical sensitization, before coating. Moreover, it can also add in several steps in these processes. The addition position is preferably from the end of formation of the photosensitive silver halide grains to before the desalting step, at the time of chemical sensitization (immediately after the start of chemical sensitization to immediately after completion), and before application, more preferably from the time of chemical sensitization. Until before mixing with the non-photosensitive organic silver salt.

  The compounds of type 1 and type 2 in the present invention are preferably added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. When the compound is dissolved in water, the compound having higher solubility when the pH is raised or lowered may be dissolved at a higher or lower pH and added.

The compounds of type 1 and type 2 in the present invention are preferably used in an image forming layer containing a photosensitive silver halide and a non-photosensitive organic silver salt, but the photosensitive silver halide and the non-photosensitive organic silver salt are used. It may be added to the protective layer and the intermediate layer together with the image forming layer containing, and diffused during coating. The addition timing of these compounds is preferably 1 × 10 ⁻⁹ mol to 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁸ mol, per mol of silver halide, regardless of before and after the sensitizing dye. It is contained in a silver halide emulsion layer (image forming layer) at a ratio of ˜5 × 10 ⁻² mol.

10) Adsorbing redox compound having an adsorbing group and a reducing group In the present invention, an adsorbing redox compound having an adsorbing group and a reducing group for silver halide is preferably contained in the molecule. The adsorptive redox compound is preferably a compound represented by the following formula (I).

Formula (I) A- (W) n-B
In the formula (I), A represents a group capable of adsorbing to silver halide (hereinafter referred to as an adsorbing group), W represents a divalent linking group, n represents 0 or 1, and B represents a reducing group. To express.

  In the formula (I), the adsorption group represented by A is a group that directly adsorbs to silver halide, or a group that promotes adsorption to silver halide, and specifically, a mercapto group (or a salt thereof). , A thione group (—C (═S) —), a heterocyclic group, a sulfide group, a disulfide group, a cationic group, or an ethynyl group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom, and a tellurium atom Etc.

The mercapto group (or salt thereof) as the adsorptive group means the mercapto group (or salt thereof) itself, and more preferably a heterocyclic group or aryl group substituted with at least one mercapto group (or salt thereof) or Represents an alkyl group. Here, the heterocyclic group is at least a 5- to 7-membered monocyclic or condensed aromatic or non-aromatic heterocyclic group such as an imidazole ring group, a thiazole ring group, an oxazole ring group, or a benzimidazole ring. Group, benzothiazole ring group, benzoxazole ring group, triazole ring group, thiadiazole ring group, oxadiazole ring group, tetrazole ring group, purine ring group, pyridine ring group, quinoline ring group, isoquinoline ring group, pyrimidine ring group, And triazine ring group. Moreover, the heterocyclic group containing the quaternized nitrogen atom may be sufficient, and in this case, the substituted mercapto group may dissociate and it may become a meso ion. When the mercapto group forms a salt, the counter ion includes a cation such as alkali metal, alkaline earth metal, heavy metal (Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ag ⁺ , or Zn ²⁺ ), ammonium ion, Examples thereof include a heterocyclic group containing a quaternized nitrogen atom, and a phosphonium ion.
Further, the mercapto group as the adsorptive group may be tautomerized into a thione group.
The thione group as an adsorptive group includes a chain or cyclic thioamide group, thioureido group, thiourethane group, or dithiocarbamate group.
A heterocyclic group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom and a tellurium atom as the adsorptive group is a -NH- group capable of forming imino silver (> NAg) as a partial structure of the heterocyclic ring. A nitrogen-containing heterocyclic group, or a heterocyclic group having a -S- group, a -Se- group, a -Te- group, or a = N- group as a partial structure of the heterocyclic ring, which can be coordinated to a silver ion by a coordination bond In the former example, benzotriazole group, triazole group, indazole group, pyrazole group, tetrazole group, benzimidazole group, imidazole group, or purine group, and the latter examples include thiophene group, thiazole group, oxazole group, Benzothiophene group, benzothiazole group, benzoxazole group, thiadiazole group, oxadiazole group, triazine group, Renoazoru group, benzoselenazole group, tellurium azole group, and the like benzo tellurium azole group.
Examples of the sulfide group or disulfide group as the adsorptive group include all groups having a partial structure of -S- or -SS-.
The cationic group as the adsorptive group means a group containing a quaternized nitrogen atom, specifically, an ammonio group or a group containing a nitrogen-containing heterocyclic group containing a quaternized nitrogen atom. Examples of the nitrogen-containing heterocyclic group containing a quaternized nitrogen atom include a pyridinio group, a quinolinio group, an isoquinolinio group, an imidazolio group, and the like.
An ethynyl group as an adsorptive group means a —C≡CH group, and the hydrogen atom may be substituted.
The adsorbing group may have an arbitrary substituent.

  Further, specific examples of the adsorbing group include those described in the specifications p4 to p7 of JP-A No. 11-95355.

  In the formula (I), preferred as the adsorptive group represented by A is a mercapto-substituted heterocyclic group (for example, 2-mercaptothiadiazole group, 2-mercapto-5-aminothiadiazole group, 3-mercapto-1,2,4). -Triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4-oxadiazole group, 2-mercaptobenzimidazole group, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, 3,5-dimercapto-1,2,4-triazole group, or 2,5-dimercapto-1,3-thiazole group), Alternatively, a nitrogen-containing heterocyclic group having a —NH— group that can form imino silver (> NAg) as a heterocyclic partial structure (for example, benzoto) Azole group, benzimidazole group, an indazole group), more preferable as an adsorptive group is a 2-mercaptobenzimidazole group, a 3,5-dimercapto-1,2,4-triazole group.

In formula (I), W represents a divalent linking group. Any linking group may be used as long as it does not adversely affect photographic properties. For example, a divalent linking group composed of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom can be used. Specifically, an alkylene group having 1 to 20 carbon atoms (such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, or a hexamethylene group), an alkenylene group having 2 to 20 carbon atoms, and an alkynylene having 2 to 20 carbon atoms. Group, arylene group having 6 to 20 carbon atoms (eg, phenylene group, naphthylene group, etc.), —CO—, —SO ₂ —, —O—, —S—, —NR ₁ —, combinations of these linking groups, etc. Is mentioned. Here, R ₁ represents a hydrogen atom, an alkyl group, a heterocyclic group, or an aryl group.
The linking group represented by W may have an arbitrary substituent.

  In formula (I), the reducing group represented by B represents a group capable of reducing silver ions. For example, a triple bond group such as formyl group, amino group, acetylene group or propargyl group, mercapto group, hydroxylamines. Hydroxamic acids, hydroxyureas, hydroxyurethanes, hydroxysemicarbazides, reductones (including reductone derivatives), anilines, phenols (chroman-6-ols, 2,3-dihydrobenzofuran-5-ols, (Including aminophenols, sulfonamidophenols, and hydroquinones, catechols, resorcinols, polyphenols such as benzenetriols, bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. Residue with one removed And the like. Of course, these may have an arbitrary substituent.

In the formula (I), the reducing group represented by B shows its oxidation potential, Akira Fujishima “Electrochemical Measurement Method” (pages 150-208, published by Gihodo Publishing) and the Chemical Society of Japan “Experimental Chemistry Course” 4th edition. It can be measured using the measurement method described in (Vol. 9, pages 282 to 344, Maruzen). For example, by a rotating disk voltammetry technique, specifically, a sample is dissolved in a solution of methanol: pH 6.5 Briton-Robinson buffer (10%: 90% (volume%)) and nitrogen gas is used for 10 minutes. , A glassy rotating disk electrode (RDE) is used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, 25 ° C., 1000 rev / min, 20 mV / sec. Can be measured at sweep speed. A half-wave potential (E1 / 2) can be obtained from the obtained voltammogram.
In the present invention, the reducing group represented by B preferably has an oxidation potential in the range of about -0.3 V to about 1.0 V when measured by the above measurement method. More preferably, it is in the range of about -0.1V to about 0.8V, and particularly preferably in the range of about 0V to about 0.7V.

  In the formula (I), the reducing group represented by B is preferably selected from hydroxylamines, hydroxamic acids, hydroxyureas, hydroxysemicarbazides, reductones, phenols, acylhydrazines, carbamoylhydrazines, and 3-pyrazolidones. A residue obtained by removing one hydrogen atom.

  The compound of the formula (I) in the present invention may be one in which a ballast group or polymer chain commonly used in an immobile photographic additive such as a coupler is incorporated. Examples of the polymer include those described in JP-A-1-100530.

  The compound of the formula (I) in the present invention may be a bis form or a tris form. The molecular weight of the compound of formula (I) in the present invention is preferably between 100 and 10000, more preferably between 120 and 1000, particularly preferably between 150 and 500.

  Examples of the compound of formula (I) in the present invention are shown below, but the present invention is not limited thereto.

  Furthermore, specific compounds 1 to 30 and 1 ″ -1 to 1 ″ -77 described in European Patent No. 1308776A2 p73 to p87 are also preferable examples of the compound having an adsorbing group and a reducing group in the present invention.

  These compounds can be easily synthesized according to known methods. As the compound of the formula (I) in the present invention, one kind of compound may be used alone, but it is also preferred to use two or more kinds of compounds at the same time. When two or more kinds of compounds are used, they may be added in the same layer or in different layers, and the addition method may be different.

The compound of formula (I) in the present invention is preferably added to the silver halide emulsion layer (image forming layer), and more preferably added during the preparation of the emulsion. When added at the time of emulsion preparation, it can be added at any time during the process. For example, silver halide grain formation process, before the start of desalting process, desalting process, chemical ripening Examples include a step before starting, a chemical ripening step, and a step before preparing a finished emulsion. Moreover, it can also be added in several steps in these processes. Although it is preferably used for the image forming layer, it may be added to the adjacent protective layer or intermediate layer together with the image forming layer and diffused during coating.
The preferred addition amount largely depends on the above-mentioned addition method and the kind of compound to be added, but generally 1 × 10 ⁻⁶ mol to 1 mol, preferably 1 × 10 ⁻⁵ mol per mol of photosensitive silver halide. The amount is 5 × 10 ⁻¹ mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻¹ mol or less.

  The compound of the formula (I) in the present invention can be added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. At this time, the pH may be appropriately adjusted with an acid or a base, and a surfactant may be allowed to coexist. Furthermore, it can also be dissolved in a high boiling point organic solvent and added as an emulsified dispersion. It can also be added as a solid dispersion.

11) Two or more silver halides used in combination The photosensitive silver halide emulsion in the photothermographic material used in the invention may be only one type, or two or more types (for example, those having different average grain sizes or different halogen compositions). Those having different crystal habits, those having different chemical sensitization conditions) may be used in combination. The gradation can be adjusted by using a plurality of types of photosensitive silver halides having different sensitivities. Examples of these technologies include JP-A-57-119341, JP-A-53-106125, JP-A-47-3929, JP-A-48-55730, JP-A-46-5187, JP-A-50-73627, and JP-A-57-150841. Can be mentioned. The sensitivity difference is preferably 0.2 log E or more for each emulsion.

12) Coating amount The addition amount of the photosensitive silver halide is preferably 0.03 g / m ² or more and 0.6 g / m ² or less, expressed as the coating silver amount per 1 m ² of the light-sensitive material, and 0.05 g. / M ² or more and 0.4 g / m ² or less is more preferable, and 0.07 g / m ² or more and 0.3 g / m ² or less is most preferable. The functional silver halide is preferably from 0.01 mol to 0.5 mol, more preferably from 0.02 mol to 0.3 mol, and still more preferably from 0.03 mol to 0.2 mol.

13) Mixing of photosensitive silver halide and organic silver salt Regarding the mixing method and mixing conditions of separately prepared photosensitive silver halide and organic silver salt, the silver halide grains and the organic silver salt that were prepared are respectively stirred at high speed. Prepare an organic silver salt by mixing with a machine, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc., or by mixing photosensitive silver halide that has been prepared at any time during the preparation of the organic silver salt However, there is no particular limitation as long as the effects of the present invention are sufficiently exhibited. Moreover, mixing two or more organic silver salt aqueous dispersions and two or more photosensitive silver salt aqueous dispersions when mixing is a preferred method for adjusting photographic characteristics.

14) Mixing of silver halide into coating solution The preferred addition time of silver halide into the image forming layer coating solution is from 180 minutes before application, preferably from 60 minutes to 10 seconds before application. The method and mixing conditions are not particularly limited as long as the effects of the present invention are sufficiently exhibited. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is the desired time, and N.I. Harnby, M.M. F. Edwards, A.D. W. There is a method using a static mixer described in Chapter 8 of Nienow's "Liquid Mixing Technology" (Nikkan Kogyo Shimbun, 1989), translated by Koji Takahashi.

(Preferable solvent for coating solution)
In the present invention, the solvent of the image forming layer coating solution of the photothermographic material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is preferably an aqueous solvent containing 30% by mass or more of water. As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, and ethyl acetate may be used. The water content of the solvent of the coating solution is preferably 50% by mass or more, more preferably 70% by mass or more. Examples of preferred solvent compositions include water, water / methyl alcohol = 90/10, water / methyl alcohol = 70/30, water / methyl alcohol / dimethylformamide = 80/15/5, water / methyl alcohol / There are ethyl cellosolve = 85/10/5, water / methyl alcohol / isopropyl alcohol = 85/10/5, etc. (numerical value is mass%).

(Development accelerator)
In the photothermographic material of the present invention, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, or the like as a development accelerator, Hindered phenol compounds represented by general formula (II) described in JP-A No. 2001-92075, general formula (I) described in JP-A No. 10-62895, JP-A No. 11-15116 and the like, A hydrazine-based compound represented by general formula (D) of JP-A No. 2002-156727 or general formula (1) described in JP-A No. 2002-278017, and described in JP-A No. 2001-264929 A phenolic or naphtholic compound represented by the general formula (2) is preferably used. These development accelerators are used in the range of 0.1 mol% to 20 mol% with respect to the reducing agent, preferably in the range of 0.5 mol% to 10 mol%, more preferably 1 mol% to 5 mol. % Range. The introduction method to the light-sensitive material includes the same method as the reducing agent, but it is particularly preferable to add as a solid dispersion or an emulsified dispersion. When added as an emulsified dispersion, it is added as an emulsified dispersion dispersed using a high-boiling solvent and a low-boiling auxiliary solvent that are solid at room temperature, or as a so-called oilless emulsified dispersion without using a high-boiling solvent It is preferable to add.
In the present invention, among the development accelerators described above, hydrazine compounds represented by the general formula (D) described in JP-A No. 2002-156727 and those described in JP-A No. 2001-264929 A phenol-based or naphthol-based compound represented by the formula (2) is more preferable.

Particularly preferred development accelerators of the present invention are compounds represented by the following general formulas (A-1) and (A-2).
Formula (A-1)
Q ₁ -NHNH-Q ₂
In the formula, Q ₁ represents an aromatic group or a heterocyclic group bonded to —NHNH—Q ₂ at a carbon atom, and Q ₂ represents a carbamoyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group, or Represents a sulfamoyl group.

In the general formula (A-1), the aromatic group or heterocyclic group represented by Q ₁ is preferably a 5- to 7-membered unsaturated ring. Preferred examples include benzene ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, 1,2,4-triazine ring, 1,3,5-triazine ring, pyrrole ring, imidazole ring, pyrazole ring, 1,2 , 3-triazole ring, 1,2,4-triazole ring, tetrazole ring, 1,3,4-thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,3,4 -Oxadiazole ring, 1,2,4-oxadiazole ring, 1,2,5-oxadiazole ring, thiazole ring, oxazole ring, isothiazole ring, isoxazole ring, or thiophene ring are preferable, A condensed ring in which these rings are condensed with each other is also preferable.

  These rings may have a substituent, and when they have two or more substituents, these substituents may be the same or different. Examples of substituents include halogen atoms, alkyl groups, aryl groups, carbonamido groups, alkylsulfonamido groups, arylsulfonamido groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, carbamoyl groups, sulfamoyl groups, cyano Groups, alkylsulfonyl groups, arylsulfonyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, and acyl groups. When these substituents are substitutable groups, they may further have substituents. Examples of preferred substituents include halogen atoms, alkyl groups, aryl groups, carbonamido groups, alkylsulfonamido groups, aryls. Sulfonamide group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, cyano group, sulfamoyl group, alkylsulfonyl group, arylsulfonyl group, and acyloxy group Can be mentioned.

The carbamoyl group represented by Q ₂ is preferably a carbamoyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms. For example, unsubstituted carbamoyl, methylcarbamoyl, N-ethylcarbamoyl, N-propylcarbamoyl N-sec-butylcarbamoyl, N-octylcarbamoyl, N-cyclohexylcarbamoyl, N-tert-butylcarbamoyl, N-dodecylcarbamoyl, N- (3-dodecyloxypropyl) carbamoyl, N-octadecylcarbamoyl, N- {3 -(2,4-tert-pentylphenoxy) propyl} carbamoyl, N- (2-hexyldecyl) carbamoyl, N-phenylcarbamoyl, N- (4-dodecyloxyphenyl) carbamoyl, N- (2-chloro-5 Dodecyloxycarbo Nylphenyl) carbamoyl, N-naphthylcarbamoyl, N-3-pyridylcarbamoyl, and N-benzylcarbamoyl.

The acyl group represented by Q ₂ is preferably an acyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms. For example, formyl, acetyl, 2-methylpropanoyl, cyclohexylcarbonyl, octanoyl, 2 -Hexyldecanoyl, dodecanoyl, chloroacetyl, trifluoroacetyl, benzoyl, 4-dodecyloxybenzoyl, and 2-hydroxymethylbenzoyl. The alkoxycarbonyl group represented by Q ₂ is preferably an alkoxycarbonyl group having 2 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, isobutyloxycarbonyl, cyclohexyloxycarbonyl, Examples include dodecyloxycarbonyl and benzyloxycarbonyl.

The aryloxycarbonyl group represented by Q ₂ is preferably an aryloxycarbonyl group having 7 to 50 carbon atoms, more preferably 7 to 40 carbon atoms, such as phenoxycarbonyl, 4-octyloxyphenoxycarbonyl, 2-hydroxy Examples include methylphenoxycarbonyl, and 4-dodecyloxyphenoxycarbonyl. The sulfonyl group represented by Q ₂ is preferably a sulfonyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as methylsulfonyl, butylsulfonyl, octylsulfonyl, 2-hexadecylsulfonyl, 3- Dodecyloxypropylsulfonyl, 2-octyloxy-5-tert-octylphenylsulfonyl, and 4-dodecyloxyphenylsulfonyl.

The sulfamoyl group represented by Q ₂ is preferably a sulfamoyl group having 0 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as an unsubstituted sulfamoyl group, an N-ethylsulfamoyl group, N- (2- Ethylhexyl) sulfamoyl, N-decylsulfamoyl, N-hexadecylsulfamoyl, N- {3- (2-ethylhexyloxy) propyl} sulfamoyl, N- (2-chloro-5-dodecyloxycarbonylphenyl) sulfamoyl, And N- (2-tetradecyloxyphenyl) sulfamoyl. The group represented by Q ₂ may further have a group listed as an example of the substituent of the 5-membered to 7-membered unsaturated ring represented by Q ₁ at a substitutable position, When it has two or more substituents, these substituents may be the same or different.

Next, preferred range for the compound represented by formula (A-1) is to be described. Q ₁ is preferably a 5- to 6-membered unsaturated ring, such as a benzene ring, pyrimidine ring, 1,2,3-triazole ring, 1,2,4-triazole ring, tetrazole ring, 1,3,4-thiadiazole. Ring, 1,2,4-thiadiazole ring, 1,3,4-oxadiazole ring, 1,2,4-oxadiazole ring, thiazole ring, oxazole ring, isothiazole ring, isoxazole ring, and these More preferred are rings in which the ring is fused with a benzene ring or an unsaturated heterocycle. Q ₂ is preferably a carbamoyl group, particularly preferably a carbamoyl group having a hydrogen atom on a nitrogen atom.

In General Formula (A-2), R ₁ represents an alkyl group, an acyl group, an acylamino group, a sulfonamide group, an alkoxycarbonyl group, or a carbamoyl group. R ₂ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acyloxy group, or a carbonate group. R ₃ and R ₄ each represents a group that can be substituted on the benzene ring mentioned in the example of the substituent of formula (A-1). R ₃ and R ₄ may be connected to each other to form a condensed ring.

R ₁ is preferably an alkyl group having 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, an isopropyl group, a butyl group, a tert-octyl group, or a cyclohexyl group), an acylamino group (for example, an acetylamino group, a benzoylamino group, Methylureido group or 4-cyanophenylureido group), carbamoyl group (n-butylcarbamoyl group, N, N-diethylcarbamoyl group, phenylcarbamoyl group, 2-chlorophenylcarbamoyl group, 2,4-dichlorophenylcarbamoyl group, etc.) ) Is more preferably an acylamino group (including a ureido group and a urethane group). R ₂ is preferably a halogen atom (more preferably a chlorine atom or a bromine atom), an alkoxy group (such as a methoxy group, a butoxy group, an n-hexyloxy group, an n-decyloxy group, a cyclohexyloxy group, or a benzyloxy group), An aryloxy group (such as a phenoxy group or a naphthoxy group);

R ₃ is preferably a hydrogen atom, a halogen atom, or an alkyl group having 1 to 20 carbon atoms, and most preferably a halogen atom. R ₄ is preferably a hydrogen atom, an alkyl group, or an acylamino group, and more preferably an alkyl group or an acylamino group. Examples of these preferable substituents are the same as those for R ₁ . When R ₄ is an acylamino group, R ₄ is preferably linked to R ₃ to form a carbostyryl ring.

In the general formula (A-2), when R ₃ and R ₄ are connected to each other to form a condensed ring, the condensed ring is particularly preferably a naphthalene ring. The same substituent as the example of a substituent quoted by general formula (A-1) may couple | bond with the naphthalene ring. When general formula (A-2) is a naphthol compound, R ₁ is preferably a carbamoyl group. Of these, a benzoyl group is particularly preferable. R ₂ is preferably an alkoxy group or an aryloxy group, and particularly preferably an alkoxy group.

  Hereinafter, preferred specific examples of the development accelerator of the present invention will be given. The present invention is not limited to these.

(Hydrogen bonding compound)
When the reducing agent in the present invention has an aromatic hydroxyl group (—OH) or amino group (—NHR, R is a hydrogen atom or an alkyl group), particularly in the case of the bisphenols described above, these groups and hydrogen bonds It is preferable to use together a non-reducing compound having a group capable of forming.
Examples of groups that form hydrogen bonds with hydroxyl groups or amino groups include phosphoryl groups, sulfoxide groups, sulfonyl groups, carbonyl groups, amide groups, ester groups, urethane groups, ureido groups, tertiary amino groups, and nitrogen-containing aromatic groups. Is mentioned. Among them, preferred are a phosphoryl group, a sulfoxide group, an amide group (however, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a urethane group. (However, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a ureido group (however, it does not have a> N—H group, N-Ra (Ra is a substituent other than H).)
In the present invention, a particularly preferred hydrogen bonding compound is a compound represented by the following general formula (D).

In the general formula (D), R ²¹ to R ²³ each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group or a heterocyclic group, and these groups may be substituted even if they are unsubstituted. You may have.
When R ²¹ to R ²³ have a substituent, the substituent is a halogen atom, alkyl group, aryl group, alkoxy group, amino group, acyl group, acylamino group, alkylthio group, arylthio group, sulfonamide group, acyloxy group, Examples thereof include an oxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, and a phosphoryl group. Preferred examples of the substituent include an alkyl group or an aryl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a t-butyl group. Examples include an octyl group, a phenyl group, a 4-alkoxyphenyl group, and a 4-acyloxyphenyl group.

Specific examples of the alkyl group of R ²¹ to R ²³ include a methyl group, an ethyl group, a butyl group, an octyl group, a dodecyl group, an isopropyl group, a t-butyl group, a t-amyl group, a t-octyl group, a cyclohexyl group, Examples thereof include 1-methylcyclohexyl group, benzyl group, phenethyl group, and 2-phenoxypropyl group.
Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-t-butylphenyl group, a 4-t-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group.

Alkoxy groups include methoxy, ethoxy, butoxy, octyloxy, 2-ethylhexyloxy, 3,5,5-trimethylhexyloxy, dodecyloxy, cyclohexyloxy, 4-methylcyclohexyloxy, and A benzyloxy group etc. are mentioned.
Examples of the aryloxy group include phenoxy group, cresyloxy group, isopropylphenoxy group, 4-t-butylphenoxy group, naphthoxy group, and biphenyloxy group.
Examples of the amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, a dioctylamino group, an N-methyl-N-hexylamino group, a dicyclohexylamino group, a diphenylamino group, and an N-methyl-N-phenylamino group. It is done.

R ²¹ to R ²³ are preferably an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. From the viewpoint of the effect of the present invention, at least one of R ²¹ to R ²³ is preferably an alkyl group or an aryl group, and more preferably two or more are an alkyl group or an aryl group. In addition, it is preferable that R ²¹ to R ²³ are the same group in that they can be obtained at low cost.

  Specific examples of the hydrogen bonding compound including the compound of the general formula (D) in the present invention are shown below, but the present invention is not limited thereto.

Specific examples of the hydrogen bonding compound include those described in European Patent No. 1096310, JP-A No. 2002-156727, and JP-A No. 2002-318431 in addition to the above.
The compound of the general formula (D) of the present invention can be used in a photothermographic material by being incorporated in a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersion fine particle dispersion in the same manner as the reducing agent. It is preferably used as a solid dispersion. The compound of the present invention forms a hydrogen-bonding complex with a compound having a phenolic hydroxyl group or amino group in a solution state, and depending on the combination of the reducing agent and the compound of the general formula (D) of the present invention, It can be isolated in the crystalline state.

The use of the crystal powder isolated in this way as a solid dispersed fine particle dispersion is particularly preferable for obtaining stable performance. In addition, a method in which a reducing agent and the compound of the general formula (D) of the present invention are mixed in a powder and complexed at the time of dispersion with a sand grinder mill or the like using an appropriate dispersant can be preferably used.
The compound of the general formula (D) of the present invention is preferably used in the range of 1 mol% to 200 mol%, more preferably in the range of 10 mol% to 150 mol%, still more preferably relative to the reducing agent. It is in the range of 20 mol% to 100 mol%.

(Anti-fogging agent)
1) Organic polyhalogen compound Hereinafter, preferred organic polyhalogen compounds that can be used in the present invention will be described in detail. A preferred polyhalogen compound of the present invention is a compound represented by the following general formula (H).

General formula (H)
Q- (Y) n-C (Z ₁ ) (Z ₂ ) X

In General Formula (H), Q represents an alkyl group, an aryl group, or a heterocyclic group, Y represents a divalent linking group, n represents 0 to ₁ , Z ₁ and Z ₂ represent a halogen atom, X represents a hydrogen atom or an electron withdrawing group.
In general formula (H), Q is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heterocyclic group containing at least one nitrogen atom (pyridine, quinoline group, etc.).

In the general formula (H), when Q is an aryl group, Q preferably represents a phenyl group substituted with an electron-withdrawing group having a positive Hammett's substituent constant σp. For Hammett's substituent constants, see Journal of Medicinal Chemistry, 1973, Vol. 16, no. 11, 1207-1216 etc. can be referred to.
Examples of such an electron withdrawing group include a halogen atom, an alkyl group substituted with an electron withdrawing group, an aryl group substituted with an electron withdrawing group, a heterocyclic group, an alkyl or arylsulfonyl group, acyl Group, alkoxycarbonyl group, carbamoyl group, sulfamoyl group and the like. Particularly preferred as the electron withdrawing group is a halogen atom, a carbamoyl group, or an arylsulfonyl group, and a carbamoyl group is particularly preferred.

X is preferably an electron withdrawing group. Preferred electron withdrawing groups are halogen atoms, aliphatic / aryl or heterocyclic sulfonyl groups, aliphatic / aryl or heterocyclic acyl groups, aliphatic / aryl or heterocyclic oxycarbonyl groups, carbamoyl groups, sulfamoyl groups, More preferred are a halogen atom and a carbamoyl group, and particularly preferred is a bromine atom.
Z ₁ and Z ₂ are preferably a bromine atom or an iodine atom, and more preferably a bromine atom.

Y preferably represents -C (= O) -, - SO -, - SO 2 -, - C (= O) N (R) -, or _-SO 2 N (R) -, more preferably -C (═O) —, —SO ₂ —, or —C (═O) N (R) —, particularly preferably —SO ₂ —, —C (═O) N (R) —.
R here represents a hydrogen atom, an aryl group or an alkyl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.
n represents 0 or 1, and is preferably 1.

In general formula (H), when Q is an alkyl group, preferred Y is —C (═O) N (R) —, and when Q is an aryl group or a heterocyclic group, preferred Y is —SO ₂ —. is there.
In the general formula (H), a form in which residues obtained by removing a hydrogen atom from the compound are bonded to each other (generally referred to as a bis type, a tris type, or a tetrakis type) can also be preferably used.
In the general formula (H), a dissociable group (for example, a COOH group or a salt thereof, a SO ₃ H group or a salt thereof, a PO ₃ H group or a salt thereof), a group containing a quaternary nitrogen cation (for example, an ammonium group or a pyridinium group) Etc.), those having a polyethyleneoxy group, a hydroxyl group or the like as a substituent are also preferred forms.

  Specific examples of the compound of the general formula (H) of the present invention are shown below.

  Polyhalogen compounds that can be used in the present invention other than those described above include US Pat. No. 3,874,946, US Pat. No. 4,756,999, US Pat. No. 5,340,712, US Pat. No. 5,369,000, US Pat. No. 5,464,537, US Pat. 119624, 59-57234, JP-A-7-2781, 7-5621, 9-160164, 9-244177, 9-244178, 9-160167, 9- 319022, 9-258367, 9-265150, 9-319022, 10-197988, 10-197989, 11-242304, JP 2000-2963, JP 2000-11270 , JP2000-284410, JP2 The compounds listed as exemplary compounds of the invention in 00-284212, JP-A-2001-33911, JP-A-2001-31644, JP-A-2001-312027, and JP-A-2003-50441 are preferably used. In particular, compounds specifically exemplified in JP-A-7-2781, JP-A-2001-33911, and JP-A-2001-312027 are preferred.

The compound represented by the general formula (H) of the present invention is preferably used in the range of 10 ⁻⁴ mol to 1 mol, more preferably 10 ⁻³ mol, per mol of the non-photosensitive silver salt of the image forming layer. It is preferable to use in the range of ˜0.5 mol, more preferably in the range of 1 × 10 ⁻² mol to 0.2 mol.
In the present invention, examples of the method for incorporating the antifoggant into the photothermographic material include the methods described in the method for containing a reducing agent, and the organic polyhalogen compound is also preferably added as a solid fine particle dispersion.

2) Other antifoggants Other antifoggants include mercury (II) salts described in paragraph No. 0113 of JP-A No. 11-65021, benzoic acids described in paragraph No. 0114 of the same, salicylic acid derivatives of JP-A No. 2000-206642, A formalin scavenger compound represented by the formula (S) in JP-A-2000-221634, a triazine compound according to claim 9 in JP-A-11-352624, and a compound represented by the general formula (III) in JP-A-6-11791 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene and the like.

The photothermographic material in the invention may contain an azolium salt for the purpose of preventing fogging. Examples of the azolium salt include compounds represented by general formula (XI) described in JP-A-59-193447, compounds described in JP-B-55-12581, and general formula (II) described in JP-A-60-153039. And the compounds represented. The azolium salt may be added to any part of the photothermographic material, but the addition layer is preferably added to the layer having the image forming layer, and more preferably to the image forming layer. The azolium salt may be added at any step in the coating solution preparation. When added to the image forming layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. Immediately before is preferable. The azolium salt may be added by any method such as powder, solution, or fine particle dispersion.
Moreover, you may add as a solution mixed with other additives, such as a sensitizing dye, a reducing agent, and a color toning agent.
In the present invention, the azolium salt may be added in any amount, but preferably 1 × 10 ⁻⁶ mol to 2 mol, and more preferably 1 × 10 ⁻³ mol to 0.5 mol, per mol of silver.

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used to control development by suppressing or accelerating development, to improve spectral sensitization efficiency, and to improve storage stability before and after development. And thione compounds, paragraphs 0067 to 0069 of JP-A-10-62899, compounds represented by formula (I) of JP-A-10-186572, and specific examples thereof include paragraph numbers 0033 to 0052. , European Patent Publication No. 0803764A1, page 20, lines 36-56. Of these, mercapto-substituted heteroaromatic compounds described in JP-A-9-297367, JP-A-9-304875, JP-A-2001-100388, JP-A-2002-303955, JP-A-2002-303951, and the like are preferable.

2) Toning agent In the photothermographic material of the invention, it is preferable to add a toning agent. For the toning agent, paragraph numbers 0054 to 0055 of JP-A-10-62899, page 21 to 23 of European Patent Publication No. 0803764A1. Line 48, described in JP-A No. 2000-356317 and JP-A No. 2000-187298, and in particular, phthalazinones (phthalazinone, phthalazinone derivatives or metal salts; for example, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone. 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione); phthalazinones and phthalic acids (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, diammonium phthalate) , Sodium phthalate, potassium phthalate and tetrachlorophthalic anhydride) Phthalazines (phthalazine, phthalazine derivatives or metal salts; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxy Phthalazine and 2,3-dihydrophthalazine); a combination of phthalazines and phthalic acids is preferred, and a combination of phthalazines and phthalic acids is particularly preferred. Among them, a particularly preferable combination is a combination of 6-isopropylphthalazine and phthalic acid or 4-methylphthalic acid.

3) Plasticizers and lubricants The plasticizers and lubricants that can be used in the image forming layer of the invention are described in paragraph No. 0117 of JP-A No. 11-65021. The slip agent is described in JP-A No. 11-84573, paragraph numbers 0061 to 0064 and Japanese Patent Application No. 11-106881, paragraph numbers 0049 to 0062.

4) Dye, Pigment The image-forming layer of the present invention has various dyes and pigments (for example, CI Pigment Blue 60, CI) from the viewpoints of color tone improvement, prevention of interference fringes during laser exposure, and prevention of irradiation. Pigment Blue 64, CI Pigment Blue 15: 6) can be used. These are described in detail in WO98 / 36322, JP-A-10-268465, JP-A-11-338098 and the like. Moreover, it is preferable to use together the water-insoluble azomethine dye represented by the general formulas (I) to (IV) described in Japanese Patent Application No. 2005-049888.

5) Nucleating Agent In the photothermographic material of the invention, it is preferable to add a nucleating agent to the image forming layer. Regarding the nucleating agent and its addition method and addition amount, paragraphs No. 0118 of JP-A No. 11-65021, paragraph Nos. 0136 to 0193 of JP-A No. 11-223898, and formulas (H of JP-A No. 2000-284399) ), Formulas (1) to (3), compounds of formulas (A) and (B), compounds of general formulas (III) to (V) described in Japanese Patent Application No. 11-91652 (specific compounds: 21 to 24) and the nucleation promoter are described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

In order to use formic acid or formate as a strong fogging substance, it is preferably contained at 5 mmol or less, more preferably 1 mmol or less, per mol of silver on the side having the image forming layer containing photosensitive silver halide.
When a nucleating agent is used in the photothermographic material of the invention, it is preferable to use an acid formed by hydrating diphosphorus pentoxide or a salt thereof in combination. Acids or salts thereof formed by hydration of diphosphorus pentoxide include metaphosphoric acid (salt), pyrophosphoric acid (salt), orthophosphoric acid (salt), triphosphoric acid (salt), tetraphosphoric acid (salt), and Examples include hexametaphosphoric acid (salt). Examples of the acid or salt thereof formed by hydrating diphosphorus pentoxide particularly preferably include orthophosphoric acid (salt) and hexametaphosphoric acid (salt). Specific examples of the salt include sodium orthophosphate, sodium dihydrogen orthophosphate, sodium hexametaphosphate, and ammonium hexametaphosphate.
The amount of acid or salt thereof formed by hydration of diphosphorus pentoxide (the coating amount per 1 m ^{2 of} photothermographic material) may be a desired amount according to the performance such as sensitivity and fog, but is 0.1 mg / m ^{2 to} 500 mg / m ² is preferable, and 0.5 mg / m ^{2 to} 100 mg / m ² is more preferable.

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution of the present invention is preferably 30 ° C. or more and 65 ° C. or less, more preferably 35 ° C. or more and less than 60 ° C., and more preferably 35 ° C. or more and 55 ° C. or less. Moreover, it is preferable that the temperature of the image forming layer coating liquid immediately after the addition of the polymer latex is maintained at 30 ° C. or higher and 65 ° C. or lower.

(Layer structure and components)
The photothermographic material of the present invention can have a non-photosensitive layer in addition to the image forming layer. The non-photosensitive layer includes (a) a surface protective layer provided on the image forming layer (on the side farther than the support), (b) between the plurality of image forming layers and between the image forming layer and the protective layer. It can be classified into an intermediate layer provided therebetween, (c) an undercoat layer provided between the image forming layer and the support, and (d) a back layer provided on the opposite side of the image forming layer.

  The optical filter layer is provided as the layer (a) or (b). The antihalation layer is provided in the photothermographic material as the layer (c) or (d).

1) Surface protective layer The photothermographic material according to the invention may be provided with a surface protective layer for the purpose of preventing adhesion of the image forming layer. The surface protective layer may be a single layer or a plurality of layers.
The surface protective layer is described in JP-A No. 11-65021, paragraph numbers 0119 to 0120 and JP-A No. 2000-171936.
As the binder for the surface protective layer of the present invention, gelatin is preferable, but it is also preferable to use polyvinyl alcohol (PVA) or a combination thereof. As gelatin, inert gelatin (for example, Nitta gelatin 750), phthalated gelatin (for example, Nitta gelatin 801), and the like can be used. Examples of PVA include those described in paragraph Nos. 0009 to 0020 of JP-A No. 2000-171936. Completely saponified PVA-105, partially saponified PVA-205, PVA-335, and modified polyvinyl alcohol MP- Preferred is 203 (trade name, manufactured by Kuraray Co., Ltd.). Preferably 0.3g ^{/ m 2} ~4.0g ^/ m 2 as a polyvinyl alcohol coating amount (per support 1 m ²⁾ of the protective layer (per one ^{layer), 0.3g / m 2 ~2.0g /} m 2 Is more preferable.

All (including water-soluble polymer and latex polymer) binder preferably 0.3g ^{/ m 2} ~5.0g ^/ m 2 as a coating amount (per support 1 m ²⁾ of the surface protective layer (per one layer), 0. 3g ^{/ m 2} ~2.0g ^/ m 2 is more preferable.

2) Antihalation layer In the photothermographic material of the invention, the antihalation layer can be provided on the side farther from the light source than the image forming layer.

As for the antihalation layer, paragraphs 0123 to 0124 of JP-A-11-65021, JP-A-11-223898, 9-230531, 10-36695, 10-104779, 11-231457, 11 -352625, 11-352626 and the like.
The antihalation layer contains an antihalation dye having absorption at the exposure wavelength. When the exposure wavelength is in the infrared region, an infrared absorbing dye may be used, and in that case, a dye having no absorption in the visible region is preferable.
When antihalation is performed using a dye having absorption in the visible region, it is preferable to prevent the dye color from substantially remaining after image formation or to use a dye having low visibility.
As a method for decolorizing the dye after image formation, it is preferable to use a means for decoloring by the heat of heat development. In particular, a thermodecolorable dye and a base precursor are added to the non-photosensitive layer to function as an antihalation layer It is preferable to make it. These techniques are described in JP-A-11-231457 and the like.
Further, by using a dye having sharp absorption at the exposure wavelength, it is possible to obtain a sufficient antihalation effect with low visibility. When such a dye is used, it is not necessary to decolorize the dye after image formation. These techniques are described in Japanese Patent Application Laid-Open No. 2003-262934 and Japanese Patent Application No. 2004-085655.

The amount of antihalation dye added is determined by the use of the dye. In general, the optical density (absorbance) measured at the target wavelength is used in an amount exceeding 0.1. The optical density is preferably 0.15 to 2, and more preferably 0.2 to 1. The amount of the dye for obtaining such an optical density is generally 0.001g ^{/ m 2} ~1g ^/ m 2 approximately.

These dyes may be used in combination of two or more different dyes.
Similarly, in the method of decolorizing the dye, two or more kinds of base precursors may be used in combination.
In the thermal decoloration using such decoloring dye and base precursor, a substance (for example, diphenylsulfone, which lowers the melting point by 3 ° C. (deg) or more when mixed with a base precursor as described in JP-A No. 11-352626). 4-Chlorophenyl (phenyl) sulfone), 2-naphthyl benzoate and the like are preferably used in view of thermal decoloring properties.
These dyes are preferably used in the image forming layer for the purpose of preventing irradiation.

3) Non-photosensitive intermediate layer The photothermographic material of the invention preferably has a non-photosensitive intermediate layer.
In the non-photosensitive intermediate layer in the present invention, preferably 50% by mass or more of the binder contains the above-described polymer latex.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, hydroxypropylcellulose, carboxymethylcellulose may be added to the non-photosensitive intermediate layer of the present invention.

  The non-photosensitive intermediate layer in the present invention preferably contains a non-photosensitive organic silver salt and / or an inorganic silver compound.

4) Back layer The photothermographic material of the invention preferably has a back layer. The back layer is described in paragraph Nos. 0128 to 0130 of JP-A No. 11-65021.

In the present invention, a colorant having an absorption maximum at 300 nm to 450 nm can be added for the purpose of improving the silver tone and the temporal change of the image. Such colorants are disclosed in JP-A-62-210458, JP-A-63-104046, JP-A-63-103235, JP-A-63-208846, JP-A-63-306436, JP-A-63-141435, and JP-A-01-61745. No. 1, Japanese Patent Laid-Open No. 2001-100363, and the like.
Such a colorant is usually preferably added in the range of 0.1 mg / m ^{2 to} 1 g / m ² .
In order to adjust the base color tone, it is preferable to use a dye having an absorption peak at 580 nm to 680 nm. As the dyes for this purpose, azomethine oil-soluble dyes described in JP-A-4-359967 and JP-A-4-359968, which have low absorption intensity on the short wavelength side, and phthalocyanine-based water-soluble dyes described in JP-A-2003-295388 are preferable. The target dye may be added to any layer, but it is more preferable to add it to the image forming layer on the image forming layer side, the non-photosensitive layer or the back side.

The photothermographic material of the present invention is a so-called single-sided photosensitive material having an image forming layer containing at least one silver halide emulsion on one side of a support and a back layer on the other side. preferable.
The layer structure of the back layer is composed of two layers including a dye-containing layer and a protective layer. However, as described in Japanese Patent Application No. 2004-382012, between the layer containing the dye and the support. It is preferable to provide an undercoat layer for improving the coating property. These two or three layers are preferably applied simultaneously and dried.

5) Membrane surface pH
The photothermographic material of the present invention preferably has a film surface pH of 7.0 or less, more preferably 6.6 or less before heat development. The lower limit is not particularly limited, but is about 3. The most preferred pH range is in the range of 4 to 6.2. The film surface pH is preferably adjusted using an organic acid such as a phthalic acid derivative, a non-volatile acid such as sulfuric acid, or a volatile base such as ammonia from the viewpoint of reducing the film surface pH. In particular, ammonia is volatile and is preferable for achieving a low film surface pH because it can be removed before the coating process or heat development.
In addition, it is also preferable to use ammonia in combination with a nonvolatile base such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. A method for measuring the film surface pH is described in paragraph No. 0123 of JP-A No. 2000-284399.

6) Hardener A hardener may be used in each layer such as the image forming layer, protective layer, and back layer of the present invention. Examples of hardeners include T.W. H. There are various methods described in "THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION" by James (published by Macmillan Publishing Co., Inc., published in 1977), pages 77 to 87, Chrome Alum, 2,4-dichloro-6 In addition to hydroxy-s-triazine sodium salt, N, N-ethylenebis (vinylsulfoneacetamide), N, N-propylenebis (vinylsulfoneacetamide), polyvalent metal ions described on page 78 of the same document, US Pat. No. 4,281 , 060, and JP-A-6-208193, epoxy compounds such as US Pat. No. 4,791,042, and vinyl sulfone compounds such as JP-A-62-289048 are preferably used.

  The hardening agent is added as a solution, and the addition time of this solution into the protective layer coating solution is from 180 minutes before to immediately before application, preferably from 60 minutes to 10 seconds before application. As long as the effects of the present invention are sufficiently exhibited, there is no particular limitation. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is a desired time, and N.I. Harnby, M.M. F. Edwards, A.D. W. There is a method using a static mixer described in Chapter 8 of Nienow's “Liquid Mixing Technology” (Nikkan Kogyo Shimbun, 1989), translated by Koji Takahashi.

7) Surfactant As for the surfactant applicable to the present invention, paragraph No. 0132 of JP-A No. 11-65021, paragraph No. 0133 of the solvent, paragraph No. 0134 of the support, and antistatic or conductive layer Paragraph No. 0135 for the method of obtaining a color image, paragraph No. 0136 for JP-A No. 11-84573 and paragraph Nos. 0049 to 0062 of Japanese Patent Application No. 11-106881 for the slip agent. Has been.

In the present invention, it is preferable to use a fluorosurfactant. Specific examples of the fluorosurfactant include compounds described in JP-A Nos. 10-197985, 2000-19680, 2000-214554 and the like. Further, a polymeric fluorine-based surfactant described in JP-A-9-281636 is also preferably used.
In the photothermographic material of the present invention, it is preferable to use fluorine-based surfactants described in JP-A Nos. 2002-82411, 2003-57780, and 2001-264110. In particular, the fluorosurfactants described in JP-A-2003-57780 and JP-A-2001-264110 are preferable in terms of charge adjustment ability, stability of the coated surface, and smoothness when coating and production is performed with an aqueous coating solution. The fluorine-based surfactant described in JP-A No. 2001-264110 is most preferable because it has a high charge adjusting ability and requires a small amount of use.

In the present invention, the fluorosurfactant can be used on either the image forming layer surface or the back surface, and is preferably used on both surfaces. Further, it is particularly preferable to use in combination with a conductive layer containing the above-described metal oxide. In this case, sufficient performance can be obtained even if the amount of the fluorosurfactant used on the surface having the conductive layer is reduced or removed.
The preferred amount of the fluorocarbon surfactant is an image forming layer side, the range to the back surface each ^{0.1mg / m 2 ~100mg / m 2} , more preferably 0.3mg ^{/ m 2} ~30mg ^/ m 2 range, even more preferably from ^{1mg / m 2 ~10mg / m 2} . In particular JP fluorocarbon surfactant described in JP-A No. 2001-264110 is ^effective, and preferably in the range of ^{0.01mg / m 2 ~10mg / m 2} , more in the range of 0.1mg / ^{m 2} ~5mg / m 2 preferable.

8) Antistatic agent In this invention, it is preferable to have a conductive layer containing a metal oxide or a conductive polymer. The antistatic layer may serve as an undercoat layer, a back layer surface protective layer, or the like, or may be provided separately. As the conductive material for the antistatic layer, a metal oxide in which conductivity is improved by introducing oxygen defects or different metal atoms into the metal oxide is preferably used. Examples of metal oxides include ZnO, TiO ₂ and SnO _2. Addition of Al and In to ZnO, addition of Sb, Nb, P and halogen elements to SnO ₂ , and addition to TiO ₂ For example, addition of Nb, Ta or the like is preferable.
In particular, SnO ₂ added with Sb is preferable. The amount of different atoms added is preferably in the range of 0.01 mol% to 30 mol%, more preferably in the range of 0.1 mol% to 10 mol%. The shape of the metal oxide may be spherical, needle-like, or plate-like, but the long axis / uniaxial ratio is 2.0 or more, preferably 3.0 to 50 in terms of the effect of imparting conductivity. Good. Range amount preferably of ^1mg / ^{m 2 ~1000mg} / m 2 of metal oxide, more preferably 10mg ^{/ m 2} ~500mg ^/ m 2 range, more preferably at 20mg ^{/ m 2} ~200mg ^/ m 2 It is a range.

  The antistatic layer of the present invention may be disposed on either the image forming layer surface side or the back surface side, but is preferably disposed between the support and the back layer. Specific examples of the antistatic layer of the present invention include paragraph No. 0135 of JP-A No. 11-65021, JP-A Nos. 56-143430, 56-143431, 58-62646, No. 56-120519, JP-A No. 11-120. No. 84573, paragraph numbers 0040 to 0051, US Pat. No. 5,575,957, and JP-A No. 11-223898, paragraph numbers 0078 to 0084.

9) Support The transparent support is subjected to heat treatment in a temperature range of 130 ° C. to 185 ° C. in order to alleviate internal strain remaining in the film during biaxial stretching and to eliminate heat shrinkage strain generated during heat development processing. Polyester, especially polyethylene terephthalate, is preferably used. In the case of a photothermographic material for medical use, the transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored. Examples of the support include water-soluble polyesters disclosed in JP-A-11-84574, styrene-butadiene copolymers described in JP-A-10-186565, and vinylidene chloride described in JP-A-2000-39684 and Japanese Patent Application No. 11-106881, paragraph numbers 0063 to 0080. It is preferable to apply an undercoating technique such as a copolymer. When the image forming layer or the back layer is applied to the support, the moisture content of the support is preferably 0.5% by mass or less.

10) Other additives Antioxidants, stabilizers, plasticizers, ultraviolet absorbers or coating aids may be further added to the photothermographic material. Various additives are added to either the image forming layer or the non-photosensitive layer. With respect to these, WO 98/36322, EP 803764A1, JP-A-10-186567, 10-18568 and the like can be referred to.

11) Coating method The photothermographic material in the invention may be coated by any method. Specifically, various coating operations including extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating, or extrusion coating using a hopper of the type described in US Pat. No. 2,681,294. And Stephen F. Kistler, Peter M. et al. The extrusion coating described in “LIQUID FILM COATING” (CHAPMAN & HALL, 1997) by Schweizer (1997), pages 399 to 536 is preferably used, and slide coating is particularly preferably used. An example of the shape of a slide coater used for slide coating is shown in FIG. 11b. 1 If desired, two or more layers can be simultaneously coated by the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761,791 and British Patent No. 837,095. . In the present invention, particularly preferred coating methods are those described in JP-A Nos. 2001-194748, 2002-153808, 2002-153803, and 2002-182333.

The image forming layer coating solution in the present invention is preferably a so-called thixotropic fluid. Regarding this technique, JP-A-11-52509 can be referred to. In the image forming layer coating solution of the present invention, the viscosity at a shear rate of 0.1S- ¹ is preferably 400 mPa · s or more and 100,000 mPa · s or less, and more preferably 500 mPa · s or more and 20,000 mPa · s or less. Moreover, in shear rate 1000S- ¹ , 1 mPa * s or more and 200 mPa * s or less are preferable, More preferably, they are 5 mPa * s or more and 80 mPa * s or less.

In the case of preparing the coating liquid of the present invention, a known in-line mixer or implant mixer is preferably used when mixing two kinds of liquids. A preferred in-line mixer of the present invention is described in JP-A No. 2002-85948, and an implant mixer is described in JP-A No. 2002-90940.
The coating solution in the present invention is preferably subjected to defoaming treatment in order to keep the coated surface state good. A preferable defoaming treatment method of the present invention is the method described in JP-A No. 2002-66431.

When applying the coating solution of the present invention, it is preferable to perform static elimination in order to prevent adhesion of dust, dust, and the like due to electric resistance of the support. An example of a preferable static elimination method in the present invention is described in JP-A No. 2002-143747.
In the present invention, it is important to precisely control the drying air and the drying temperature in order to dry the non-setting image forming layer coating solution. The preferred drying method of the present invention is described in detail in JP-A Nos. 2001-194749 and 2002-139814.

  The photothermographic material of the present invention is preferably subjected to a heat treatment immediately after coating and drying in order to improve film formability. The temperature of the heat treatment is preferably in the range of 60 ° C. to 100 ° C. as the film surface temperature, and the heating time is preferably in the range of 1 second to 60 seconds. A more preferable range is a film surface temperature of 70 ° C. to 90 ° C. and a heating time of 2 seconds to 10 seconds. A preferable heat treatment method of the present invention is described in JP-A No. 2002-107872.

  In order to stably and continuously produce the photothermographic material of the present invention, the production methods described in JP-A Nos. 2002-156728 and 2002-182333 are preferably used.

12) Packaging material The photothermographic material of the present invention is a packaging material having a low oxygen permeability and / or moisture permeability in order to suppress fluctuations in photographic performance during raw storage or to improve curling and curling. It is preferable to package. The oxygen permeability is preferably 50 mL / atm · m ² · day or less at 25 ° C., more preferably 10 mL / atm · m ² · day or less, and even more preferably 1.0 mL / atm · m ² · day or less. is there. The moisture permeability is preferably 10 g / atm · m ² · day or less, more preferably 5 g / atm · m ² · day or less, and still more preferably 1 g / atm · m ² · day or less.
Specific examples of the packaging material having a low oxygen permeability and / or moisture permeability are disclosed in, for example, JP-A-8-254793. This is a packaging material described in JP-A-2000-206653.

13) Other technologies that can be used Techniques that can be used in the photothermographic material of the present invention include EP80364A1, EP883022A1, WO98 / 36322, JP-A-56-62648, JP-A-58-62644, and JP-A-5-62644. 9-43766, 9-281737, 9-297367, 9-304869, 9-31405, 9-329865, 10-10669, 10-62899, 10-69023 10-186568, 10-90823, 10-171663, 10-186565, 10-186567, 10-186567 to 10-186572, 10-197974, Nos. 10-197982, 10-197983, 10-197985 to 1 No. 0-197987, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10-307365, No. 10- No. 312038, No. 10-339934, No. 11-7100, No. 11-15105, No. 11-24200, No. 11-24201, No. 11-30832, No. 11-84574, No. 11-65021 11-109547, 11-125880, 11-129629, 11-133536 to 11-133539, 11-133542, 11-133543, 11-223898, 11-352627, 11-305377, 11-305378, 11-305 84, 11-305380, 11-316435, 11-327076, 11-338096, 11-338098, 11-338099, 11-343420, JP 2000-187298 , 2000-10229, 2000-47345, 2000-206642, 2000-98530, 2000-98531, 2000-112059, 2000-112060, 2000-112104, Examples thereof include 2000-112064 and 2000-171936.

(Image forming method)
1) Exposure The photothermographic material of the present invention may be exposed by any method, but scanning exposure with a laser is preferably used. As the laser, a red to infrared light emitting He—Ne laser, a red semiconductor laser, or a blue to green light emitting Ar ⁺ , He—Ne, He—Cd laser, or a blue semiconductor laser can be used. Preferred is a red to infrared semiconductor laser, and the peak wavelength of the laser light is 600 nm to 900 nm, preferably 620 nm to 850 nm.
On the other hand, in recent years, in particular, a module in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated and a blue semiconductor laser have been developed, and a laser output device in a short wavelength region has been closed up. The blue semiconductor laser is expected to increase in demand in the future because high-definition image recording is possible, the recording density is increased, and a stable output is obtained with a long lifetime. The peak wavelength of the blue laser light is preferably 300 nm to 500 nm, particularly preferably 400 nm to 500 nm.
It is also preferable that the laser light is oscillated in a vertical multi by a method such as high frequency superposition.

2) Photothermographic development The photothermographic material of the present invention may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. A preferred development temperature is 80 ° C to 250 ° C, preferably 100 ° C to 140 ° C, and more preferably 110 ° C to 130 ° C. The development time is preferably 1 second to 60 seconds, more preferably 3 seconds to 30 seconds, and even more preferably 5 seconds to 25 seconds.

Either a drum type heater or a plate type heater may be used as the thermal development method, but the plate type heater method is more preferable. The heat development method using the plate type heater method is preferably a method described in JP-A-11-133572, and a visible image is obtained by bringing a photothermographic material having a latent image formed thereon into contact with a heating means in a heat developing unit. In the heat development apparatus, the heating unit includes a plate heater, and a plurality of press rollers are disposed to face each other along one surface of the plate heater, and the press roller is disposed between the press roller and the plate heater. A heat development apparatus characterized in that heat development is performed by passing a photothermographic material. It is preferable to divide the plate heater into 2 to 6 stages and lower the temperature about 1 ° C. to 10 ° C. at the tip. For example, there are examples in which four sets of plate heaters that can be independently controlled are used and controlled so as to be 112 ° C., 119 ° C., 121 ° C., and 120 ° C., respectively.
Such a method is also described in JP-A-54-30032, which can exclude moisture and organic solvents contained in the photothermographic material out of the system, and rapidly develop the photothermographic material. It is also possible to suppress a change in the shape of the support of the photothermographic material due to the heating.

  In order to reduce the size of the heat developing machine and shorten the heat development time, it is preferable to be able to control the heater more stably. In addition, the exposure of one sheet of photosensitive material is started from the top and the exposure is finished to the rear end. It is desirable to start the heat development before the time. Imagers capable of rapid processing preferable for the present invention are described in, for example, JP-A Nos. 2002-289804 and 091114.

3) System As a medical laser imager provided with an exposure part and a heat development part, Fuji Medical Dry Laser Imager FM-DPL and DRYPIX7000 can be exemplified. Regarding FM-DPL, Fuji Medical Review No. 8, pages 39 to 55, and it goes without saying that these techniques are applied as a laser imager of the photothermographic material of the present invention. Further, it can also be applied as a photothermographic material for a laser imager in “AD network” proposed by Fuji Film Medical Co., Ltd. as a network system adapted to the DICOM standard.

(Use of the present invention)
The photothermographic material of the present invention preferably forms a black and white image by a silver image and is used as a photothermographic material for medical diagnosis.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1
(Preparation and storage of polymer dispersion)
<< LT-1: Preparation of Comparative Example >>
Methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) latex 20.5 mass% liquid 4600 mL synthesized by a usual emulsion polymerization method After adding 10 g of ABS-1 as a surfactant and 0.46 g of benzoisothiazolinone as a preservative and 60 mL of NaOH aqueous solution for pH adjustment, ion exchange water was added to 5160 mL.
The obtained polymer dispersion was stored in a storage tank that was not sterilized but washed only with water, sealed, and stored at room temperature.
The storage tank used here is a cylindrical polypropylene container (capacity 1 L) having a screw opening. The same container was used for LT-2 to 13 below.
The container was washed with 30% by volume of sterilized water with respect to the total volume of the container, and the wash water was sampled and passed for one day at room temperature. Table 1 shows the results of testing the washing water simple culture test (manufactured by Petrifilm AC 3M).

<< LT-2: Preparation of Comparative Example >>
In the preparation of LT-1, LAS-1 was used instead of ABS-1 as a surfactant, and the others were similarly prepared and stored.
The BOD / ThOD values of ABS-1 and LAS-1 are as follows.
BOD / ThOD
ABS-1 0%
LAS-1 73%

ABS-1: Hard dodecylbenzenesulfonic acid sodium salt
(Taika Co., Ltd., Teica Power BN 2070, effective concentration 27% by mass)
LAS-1: Soft dodecylbenzenesulfonic acid sodium salt
(Neopelex G-15, manufactured by Kao Corporation)

<< LT-3: Preparation of Comparative Example >>
The polymer latex obtained in the preparation of LT-2 was heat-treated at 80 ° C. for 1 hour before storage.

<< LT-4: Preparation of Comparative Example >>
The amount of benzoisothiazolinone added in the preparation of LT-2 was increased to 1000 ppm, and the others were prepared and stored in the same manner.

<< LT-5: Preparation according to the invention >>
The polymer latex obtained in the preparation of LT-2 was stored in a storage container subjected to the following sterilization treatment.

Sterilization treatment 100% by volume of hot water at 80 ° C. was filled with respect to the total volume of the container, and the container was covered and left standing for 1 hour. Thereafter, hot water in the container was discharged, and this was used as a sterilized container.

<< LT-6: Comparative Example >>
In the preparation of LT-5, the addition amount of benzoisothiazolinone was added at 1000 ppm, and the others were prepared and stored in the same manner.

<< LT-7: Preparation according to the invention >>
In the preparation of LT-5, the addition amount of benzoisothiazolinone was changed to 500 ppm, and the others were similarly prepared and stored.

<< LT-8: Preparation according to the invention >>
In the preparation of LT-5, the addition amount of benzoisothiazolinone was changed to 200 ppm, and the others were similarly prepared and stored.

<< LT-9: Preparation according to the invention >>
In the preparation of LT-5, the addition amount of benzoisothiazolinone was changed to 10 ppm, and the others were similarly prepared and stored.

<< LT-10, 11: Preparation according to the invention >>
In the preparation of LT-5, MIT or p-oxybenzoic acid was added as a preservative instead of benzoisothiazolinone, and the others were prepared and stored in the same manner.
The dispersion using MIT was LT-10, and the dispersion using p-oxybenzoic acid was LT-11.

<< LT-12, 13: Preparation according to the invention >>
In the preparation of LT-5, LOS-1 was used as a surfactant, AOS or C ₁₂ E ₁₀ was added instead, and the others were similarly prepared and stored.
The dispersion using AOS was LT-12, and the dispersion using C ₁₂ E ₁₀ was LT-13.
The BOD value and COD value of AOS or C ₁₂ E ₁₀ are as follows.
BOD / ThOD
AOS 85%
C ₁₂ E ₁₀ 73%

<< LT-14: Comparative Example >>
Methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) latex 20.5 mass% liquid 4600 mL synthesized by a usual emulsion polymerization method 10 g of ABS-1 as a surfactant and 10 g of C ₁₆ EO ₂₅ and 0.46 g of benzoisothiazolinone as a preservative and 60 mL of aqueous NaOH solution for pH adjustment were added to ion exchange water to 5160 mL. did.
The obtained polymer dispersion was stored in a storage tank that was not sterilized but washed only with water, sealed, and stored at room temperature.
C ₁₆ EO _{25 has} a BOD / ThOD of 45%.

≪LT-15, 16≫
LT-15 was prepared and stored in the same manner as LT-14 except that LAS-1 was added instead of ABS-1. Moreover, what stored the liquid prepared similarly in the sterilization processing container was set to LT-16.

<< LT-17: Comparative Example >>
LT-17 was prepared in the same manner as LT-14 except that the amount of preparation was increased by 1,000 times, and it was stored in a storage container that had been washed with water only, sealed, and stored at room temperature.
The storage container used here is a high-density polyethylene container (Yucatener, volume 1 m ³ ) with a pumping ball valve. Hereinafter, the same container was also used for LT-18 and 19.
≪LT-18, 19≫
5160 kg of LT-18 was prepared in the same manner as LT-15 except that the amount of preparation was increased by 1,000 times, housed in a storage container that had been washed only with water, sealed, and stored at room temperature. Moreover, what stored the liquid prepared similarly in the sterilization processing container was set to LT-19.

<Measurement of bacterial count in polymer dispersion>
The obtained polymer dispersion was stored in a container in a sealed state and stored at 25 ° C. for 5 days, and then subjected to application of a photothermographic material. Immediately before preparing the coating solution, each polymer latex was sampled, and the number of colony bacteria (cf / mL) after culturing at 30 ° C. for 2 days by a simple culture test (EasictTCTM) was measured.
The results are shown in Table 1.

(Preparation of PET support)
1. Film formation Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured in phenol / tetrachloroethane = 6/4 (mass ratio) at 25 ° C.) was obtained. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to prepare an unstretched film.

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

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

3. Undercoat <Preparation of undercoat layer coating solution>
Formula (1) (for photosensitive layer side undercoat layer)
59 g of pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 10% by mass solution 5.4 g
MP-1000 (polymer fine particles, average particle size 0.4 μm) 0.91 g manufactured by Soken Chemical Co., Ltd.
935 mL of distilled water

Formula (2) (for back layer 1st layer)
Styrene-butadiene copolymer latex 158g
(Solid content 40% by mass, styrene / butadiene mass ratio = 68/32)
2,4-dichloro-6-hydroxy-S-triazine sodium salt (8% by mass aqueous solution)
20g
10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
854 mL of distilled water

Formula (3) (for back side second layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion)
84g
Gelatin (10 mass% aqueous solution) 89.2g
8.6 g of Metroise TC-5 (2% by mass aqueous solution) manufactured by Shin-Etsu Chemical Co., Ltd.
MP-1000 0.01g manufactured by Soken Chemical Co., Ltd.
10 mL of 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 6 mL
Proxel (ICI) 1mL
805 mL of distilled water

<Undercoat>
After both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm are subjected to the corona discharge treatment, the undercoat coating solution formulation (1) is applied on one side (image forming layer surface) with a wire bar with a wet coating amount of 6. .6mL / m 2 was applied ^(per one side) and dried for 5 minutes at 180 ° C., then the amount of wet coating the coating solution for the undercoat was coated (2) by a wire bar on the rear surface (back surface) 5. was applied so as to 7 mL / ^{m 2} and dried 5 minutes at 180 ° C., wet coating amount is 7.7 mL / ^{m 2} further backside (the back face) the coating solution for the undercoat was coated (3) with a wire bar It was applied as described above and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

(Back layer)
1) Preparation of back layer coating solution << Back layer coating solution >>
Keep the container at 40 ° C. and add 100 g of gelatin, 400 mg of benzoisothiazolinone, 43 mL of 5% by weight aqueous solution of blue dye compound-2, 5.7 mL of 10% by weight aqueous solution of blue dye FRL-SF manufactured by Clariant, and 1600 mL of water. The gelatin was dissolved. Further, 80 mL of a 3% by weight aqueous polystyrene sulfonate solution and 200 g of a 10% by weight isoprene latex (TP-2) solution were mixed. Immediately before coating, 50 mL of a 4% by mass aqueous solution of N, N-ethylenebis (vinylsulfone acetamide) was mixed. The viscosity of the coating solution was 32 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm). The pH of the coating solution was 6.4 at 40 ° C.

2) Preparation of back surface protective layer coating solution The container was kept at 40 ° C., gelatin 100 g, monodispersed polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4) 5.7 g, benzoisothiazolinone 600 mg Then, 1700 mL of water was added to dissolve the gelatin. Furthermore, liquid paraffin emulsion is made into liquid paraffin 36g, sulfosuccinic acid di (2-ethylhexyl) sodium salt 5 mass% aqueous solution 24mL, polystyrene sulfonate 3 mass% aqueous solution 50mL, fluorine-type surfactant (F-1) 1 mass%. 12 mL of the solution, 2.4 mL of a 2% by mass solution of a fluorosurfactant (F-2), and 72 g of an ethyl acrylate / acrylic acid copolymer (copolymerization mass ratio 64/4) latex 20% by mass were mixed. Immediately before coating, 90 mL of a 4% by weight aqueous solution of N, N-ethylenebis (vinylsulfone acetamide) was mixed to prepare a back surface protective layer coating solution. The viscosity of the coating solution was 28 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm). The pH of the coating solution was 6.1 at 40 ° C.

On the back surface side of the coating the undercoat support 3) back layer, a back layer coating solution so as the coating amount of gelatin of 1.7 g / m ^2, also for the back surface protective layer coating solution coating amount of gelatin 0. A simultaneous multilayer coating was applied so as to be 52 g / m ² , followed by drying to produce a back layer.

(Image forming layer, intermediate layer, and surface protective layer)
1. Preparation of coating materials 1) Silver halide emulsion << Preparation of silver halide emulsion 1 >>
To a solution of 1421 mL of distilled water, 3.1 mL of a 1% by mass potassium bromide solution was added, and a solution containing 3.5 mL of 0.5 mol / L sulfuric acid and 31.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 30 ° C., the solution A diluted with 92.2 mL of distilled water added to 22.22 g of silver nitrate, 15.3 g of potassium bromide and 0.8 g of potassium iodide in a distilled water volume of 97.4 mL The whole amount of the solution B diluted to 1 was added at a constant flow rate over 45 seconds. Thereafter, 10 mL of a 3.5% by mass aqueous hydrogen peroxide solution was added, and further 10.8 mL of a 10% by mass aqueous solution of benzimidazole was added. Further, a solution C in which distilled water was added to 51.86 g of silver nitrate and diluted to 317.5 mL, a solution D in which 44.2 g of potassium bromide and 2.2 g of potassium iodide were diluted with distilled water to a volume of 400 mL were added to solution C. Was added at a constant flow rate over 20 minutes, and solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so as to be 1 × 10 ⁻⁴ mole per mole of silver. Further, 5 seconds after completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

The silver halide dispersion was maintained at 38 ° C. with stirring, 5 mL of a 0.34 mass% 1,2-benzisothiazolin-3-one methanol solution was added, and the temperature was raised to 47 ° C. after 40 minutes. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per mol of silver, and further 5 minutes later, tellurium sensitizer C was added in a methanol solution to a ratio of 2. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes. Thereafter, a methanol solution having a molar ratio of the spectral sensitizing dye A and the sensitizing dye B of 3: 1 was added in an amount of 1.2 × 10 ⁻³ mol as the total of the sensitizing dyes A and B per mol of silver, and N was added after 1 minute. , N′-dihydroxy-N ″ -diethylmelamine in 1.3 mL of a 0.8 wt% methanol solution was added, and after an additional 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the methanol solution at a rate of 4.8 per mole of silver. × 10 ⁻³ mol, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in methanol solution to 5.4 × 10 ⁻³ mol and 1- (3-methyl in 1 mol of silver A silver halide emulsion 1 was prepared by adding 8.5 × 10 ⁻³ mol of ureidophenyl) -5-mercaptotetrazole in an aqueous solution to 1 mol of silver.

  The grains in the prepared silver halide emulsion were silver iodobromide grains containing 3.5 mol% of iodine having an average sphere equivalent diameter of 0.042 μm and a sphere equivalent diameter variation coefficient of 20%. The particle size and the like were determined from an average of 1000 particles using an electron microscope. The {100} face ratio of the particles was determined to be 80% using the Kubelka-Munk method.

<< Preparation of silver halide emulsion 2 >>
In the preparation of silver halide emulsion 1, the liquid temperature 30 ° C. at the time of grain formation was changed to 47 ° C., and solution B was changed to diluting 15.9 g of potassium bromide to a volume of 97.4 mL with distilled water, Solution D was changed to diluting 45.8 g of potassium bromide with distilled water to a volume of 400 mL, and the addition time of solution C was changed to 30 minutes to remove potassium hexacyanoiron (II) in the same manner. A silver halide emulsion 2 was prepared. Precipitation / desalting / washing / dispersion was carried out in the same manner as silver halide emulsion 1. Further, the addition amount of tellurium sensitizer C is 1.1 × 10 ⁻⁴ mol per mol of silver, and the addition amount of methanol solution of 3: 1 in the molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is silver. The total of sensitizing dye A and sensitizing dye B per mole is 7.0 × 10 ⁻⁴ mole, and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole is added to 1 mole of silver. Same as Emulsion 1 except that 3.3 × 10 ⁻³ mol and 1- (3-methylureidophenyl) -5-mercaptotetrazole were changed to 4.7 × 10 ⁻³ mol added to 1 mol of silver. Spectral sensitization, chemical sensitization, and addition of 5-methyl-2-mercaptobenzimidazole and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole were carried out to obtain silver halide emulsion 2. . The emulsion grains of the silver halide emulsion 2 were pure silver bromide cubic grains having an average sphere equivalent diameter of 0.080 μm and a sphere equivalent diameter variation coefficient of 20%.

<< Preparation of silver halide emulsion 3 >>
In the preparation of silver halide emulsion 1, silver halide emulsion 3 was prepared in the same manner except that the liquid temperature at the time of grain formation was changed from 30 ° C. to 27 ° C. Further, precipitation / desalting / washing / dispersion was performed in the same manner as silver halide emulsion 1. The molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is 1: 1 as a solid dispersion (gelatin aqueous solution), and the addition amount is 6 × 10 ⁻ as the total of sensitizing dye A and sensitizing dye B per mole of silver. ³ moles, the amount of tellurium sensitizer C added was changed to 5.2 × 10 ⁻⁴ moles per mole of silver, and bromoauric acid was added 5 × 10 ⁻⁴ moles per silver 3 minutes after the addition of tellurium sensitizers. A silver halide emulsion 3 was obtained in the same manner as Emulsion 1 except that 2 × 10 ⁻³ mol of mol and potassium thiocyanate were added per mol of silver. The emulsion grains of the silver halide emulsion 3 were silver iodobromide grains containing 3.5 mol% of iodine having an average sphere equivalent diameter of 0.034 μm and a sphere equivalent diameter variation coefficient of 20%.

<< Preparation of mixed emulsion A for coating solution >>
70% by weight of silver halide emulsion 1, 15% by weight of silver halide emulsion 2 and 15% by weight of silver halide emulsion 3 were dissolved, and 7% by mole of silver in a 1% by weight aqueous solution of benzothiazolium iodide. × 10 ⁻³ mol was added. Further, water is added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution is 38.2 g as silver, and 1- (3-methylureidophenyl) is adjusted to 0.34 g per 1 kg of the mixed emulsion for coating solution. -5-mercaptotetrazole was added.

Further, as "a compound in which a one-electron oxidant produced by one-electron oxidation can emit one electron or more", each of compounds 1, 20 and 26 is 2 × 10 ⁻³ per mole of silver halide. Molar amounts were added.

2) Preparation of fatty acid silver dispersion <Preparation of recrystallized behenic acid>
100 kg of behenic acid (product name Edenor C22-85R) manufactured by Henkel was mixed in 1200 kg of isopropyl alcohol, dissolved at 50 ° C., filtered through a 10 μm filter, cooled to 30 ° C., and recrystallized. The cooling speed during recrystallization was controlled at 3 ° C./hour. The obtained crystals were centrifugally filtered, washed with 100 kg of isopropyl alcohol, and then dried. When the obtained crystals were esterified and subjected to GC-FID measurement, the behenic acid content was 96 mol%, and in addition, lignoceric acid was 2 mol%, arachidic acid was 2 mol%, and erucic acid was 0.001 mol%. It was.

<Preparation of fatty acid silver dispersion>
Recrystallized behenic acid 88 kg, distilled water 422 L, 5 mol / L NaOH aqueous solution 49.2 L and t-butyl alcohol 120 L were mixed and stirred at 75 ° C. for 1 hour to react to obtain sodium behenate solution B. Separately, 206.2 L (pH 4.0) of an aqueous solution containing 40.4 kg of silver nitrate was prepared and kept warm at 10 ° C. A reaction vessel containing 635 L of distilled water and 30 L of t-butyl alcohol was kept at 30 ° C., and with sufficient stirring, the total amount of the previous sodium behenate solution B and the total amount of silver nitrate aqueous solution were kept at a constant flow rate for 93 minutes 15 Added over seconds and 90 minutes. At this time, only the silver nitrate aqueous solution is added for 11 minutes after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution B is started. After the addition of the aqueous silver nitrate solution is completed, only the sodium behenate solution B is added for 14 minutes and 15 seconds. Was added. At this time, the temperature in the reaction vessel was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant. The pipe of the addition system for the sodium behenate solution B was kept warm by circulating hot water outside the double pipe so that the liquid temperature at the outlet at the tip of the addition nozzle was 75 ° C.
Moreover, the piping of the addition system of the silver nitrate aqueous solution was kept warm by circulating cold water outside the double pipe. The addition position of the sodium behenate solution B and the addition position of the silver nitrate aqueous solution were symmetrically arranged around the stirring axis, and were adjusted so as not to contact the reaction solution.

After completion of the addition of the sodium behenate solution B, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm. Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying.
When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average values were a = 0.21 μm, b = 0.4 μm, c = 0.4 μm, average aspect ratio 2.1, and equivalent sphere diameter. It was a crystal with a variation coefficient of 11% (a, b, and c are defined in the text).

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

Next, the pre-dispersed undiluted solution is adjusted to a pressure of 1150 kg / cm ² in a disperser (trade name: Microfluidizer M-610, manufactured by Microfluidics International Corporation, using a Z-type interaction chamber) three times. Treatment gave a silver behenate dispersion. The cooling operation was carried out by installing a serpentine heat exchanger before and after the interaction chamber, and adjusting the temperature of the refrigerant to a dispersion temperature of 18 ° C.

3) Preparation of reducing agent dispersion << Preparation of reducing agent-2 dispersion >>
10 masses of reducing agent-2 (6,6′-di-t-butyl-4,4′-dimethyl-2,2′-butylidenediphenol) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 16 kg of% aqueous solution and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the reducing agent to 25% by mass. This dispersion was heated at 40 ° C. for 1 hour, and then further heated at 80 ° C. for 1 hour to obtain a reducing agent-2 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.50 μm and a maximum particle diameter of 1.6 μm or less.
The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

4) Preparation of hydrogen bonding compound-1 dispersion 10 kg of hydrogen bonding compound-1 (tri (4-t-butylphenyl) phosphine oxide) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 16 kg of the aqueous solution and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump, and dispersed for 4 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to adjust the concentration of the hydrogen bonding compound to 25% by mass. The dispersion was heated at 40 ° C. for 1 hour and then further heated at 80 ° C. for 1 hour to obtain a hydrogen bonding compound-1 dispersion. The hydrogen bonding compound particles contained in the hydrogen bonding compound dispersion thus obtained had a median diameter of 0.45 μm and a maximum particle diameter of 1.3 μm or less. The obtained hydrogen bonding compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

5) Preparation of Development Accelerator-1 Dispersion 10 kg of Development Accelerator-1 and 20 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) were added with 10 kg of water and mixed well. To make a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the development accelerator to 20% by mass to obtain a development accelerator-1 dispersion. The development accelerator particles contained in the development accelerator dispersion thus obtained had a median diameter of 0.48 μm and a maximum particle diameter of 1.4 μm or less. The obtained development accelerator dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.
6) Preparation of Development Accelerator-2 Dispersion The solid dispersion of Development Accelerator-2 was also dispersed in the same manner as in Development Accelerator-1, and a 20 mass% dispersion was obtained.

7) Preparation of polyhalogen compound << Preparation of organic polyhalogen compound-1 dispersion >>
10 kg of organic polyhalogen compound-1 (tribromomethanesulfonylbenzene), 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), 0.4 kg of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, Then, 14 kg of water was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 26% by mass to obtain an organic polyhalogen compound-1 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of organic polyhalogen compound-2 dispersion >>
10 kg of an organic polyhalogen compound-2 (N-butyl-3-tribromomethanesulfonylbenzoamide), 20 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and 20 of sodium triisopropylnaphthalenesulfonate 0.4 kg of a mass% aqueous solution was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 30% by mass. This dispersion was heated at 40 ° C. for 5 hours to obtain an organic polyhalogen compound-2 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.3 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

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

9) Preparation of mercapto compound << Preparation of aqueous solution of mercapto compound-2 >>
20 g of mercapto compound-2 (1- (3-methylureidophenyl) -5-mercaptotetrazole) was dissolved in 980 g of water to obtain a 2.0 mass% aqueous solution.

10) Preparation of azomethine dye solid dispersion 1.0 kg of azomethine dye-A, 3.0 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and surfactant (Pionin A-43-S) 42 g (48% by mass aqueous solution of Takemoto Yushi Co., Ltd.) and 3.0 g of antifoaming agent (Surfinol 104E (Shin-Etsu Chemical Co., Ltd.)) were added and mixed well to obtain a slurry.
This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 1. 0 g and water were added to adjust the concentration of the water-insoluble azomethine dye to 10% by mass. This dispersion was heated at 40 ° C. for 2 hours to obtain an azomethine-27 dispersion. The azomethine dye particles contained in the azomethine dye dispersion thus obtained had a median diameter of 0.49 μm and a maximum particle diameter of 2.6 μm or less. The obtained azomethine dye dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

11) Preparation of benzotriazole silver dispersion 1 kg of benzotriazole is added to a solution obtained by dissolving 360 g of sodium hydroxide in 9100 mL of water, and the mixture is stirred for 60 minutes, and the dissolved solution is used as a sodium benzotriazole solution BT.
A solution obtained by adding 55.9 g of alkali-treated deionized gelatin to 1400 mL of distilled water, stirring the solution in a stainless steel reaction vessel, maintaining the liquid temperature at 70 ° C., and adding distilled water to 54.0 g of silver nitrate and diluting to 400 mL A solution B is prepared by diluting A and benzotriazole sodium solution BT397mL with distilled water to a volume of 420mL, and by double jet method, solution B is added to a stainless steel reaction tank at a constant flow rate of 20mL / min over a period of 11 minutes. 1 minute after the start of addition of solution B, 200 ml of solution A was added to a stainless steel reaction vessel at a constant flow rate of 20 mL / min over 10 minutes. Thereafter, after 6 minutes, solutions A and B were added simultaneously at a constant flow rate of 33.34 mL / min in 200 mL portions over 6 minutes. After the temperature dropped to 45 ° C., 92 mL of Demol N (10% aqueous solution, manufactured by Kao Corporation) was added with stirring, the pH was adjusted to 4.1 with 1 mol / L sulfuric acid, and stirring was stopped. Then, precipitation / desalting / water washing steps were performed.
Then, after adjusting the temperature to 50 ° C. and adding 51 ml of 1 mol / L sodium hydroxide with stirring, 11 mL of a methanol solution of benzoisothiazolinone (3.5%), a methanol solution of sodium benzenethiosulfonate ( 1%) 7.7 mL was added, and after stirring for 80 minutes, the pH was adjusted to 7.8 using 1 mol / L sulfuric acid to prepare a benzotriazole silver dispersion.

  The particles of the benzotriazole silver dispersion thus prepared had an average equivalent circle diameter of 0.172 μm (variation coefficient 18.5%), an average long side diameter of 0.32 μm, an average short side diameter of 0.09 μm, and an average long / short side ratio of 0.00. There were 298 particles. The particle size and the like were determined from the average of 300 particles using an electron microscope.

12) Preparation of SBR latex solution SBR latex was prepared as follows.
In a polymerization kettle of a gas monomer reactor (TAS-2J type manufactured by Pressure Glass Industrial Co., Ltd.), 287 g of distilled water and a surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)): solid content 48.5 (Mass%) 7.73 g, 1 mol / L, NaOH 14.06 mL, ethylenediaminetetraacetic acid tetrasodium salt 0.15 g, styrene 255 g, acrylic acid 11.25 g, tert-dodecyl mercaptan 3.0 g were put, and the reaction vessel was sealed and stirred. Stir at a speed of 200 rpm. After degassing with a vacuum pump and repeating nitrogen gas replacement several times, 108.75 g of 1,3-butadiene was injected to raise the internal temperature to 60 ° C. A solution prepared by dissolving 1.875 g of ammonium persulfate in 50 mL of water was added thereto and stirred as it was for 5 hours. The temperature was further raised to 90 ° C. and stirred for 3 hours. After completion of the reaction, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion = 1 using 1 mol / L NaOH and NH ₄ OH = 1. Addition treatment was performed so that the molar ratio was 5.3 (molar ratio), and the pH was adjusted to 8.4. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored, and 774.7 g of SBR latex was obtained. When the halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 145 ppm.

  The latex has an average particle size of 90 nm, Tg = 17 ° C., solid content concentration of 44 mass%, equilibrium moisture content at 25 ° C. and 60% RH, 0.6 mass%, ion conductivity of 4.80 mS / cm (measurement of ion conductivity is A latex stock solution (44 mass%) was measured at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.).

13) Preparation of isoprene latex liquid Isoprene latex (TP-2) was prepared as follows.
Add 1500 g of distilled water to the polymerization kettle of the gas monomer reactor (Pressure Glass Industry Co., Ltd. TAS-2J type), heat at 90 ° C. for 3 hours, and passivate to the stainless steel surface of the polymerization kettle and members of the stainless steel stirring device A film is formed. In this polymerized kettle, 582.28 g of distilled water bubbled with nitrogen gas for 1 hour, 9.49 g of surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)), 1 mol / L NaOH Of ethylenediaminetetraacetic acid tetrasodium salt 0.20 g, styrene 314.99 g, isoprene 190.87 g, acrylic acid 10.43 g, tert-dodecyl mercaptan 2.09 g, and the reaction vessel was sealed and stirred at 225 rpm. The mixture was stirred and heated to an internal temperature of 65 ° C. A solution prepared by dissolving 2.61 g of ammonium persulfate in 40 ml of water was added thereto, and the mixture was stirred as it was for 6 hours. At this time, the polymerization conversion rate was 90% from the measurement of the solid content. Here, a solution obtained by dissolving 5.22 g of acrylic acid in 46.98 g of water was added, followed by addition of 10 g of water, and further a solution obtained by dissolving 1.30 g of ammonium persulfate in 50.7 ml of water. After the addition, the temperature was raised to 90 ° C. and stirred for 3 hours. After the reaction was completed, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion was used using 1 mol / L NaOH and NH ₄ OH. = 1: 5.3 (molar ratio) was added and adjusted to pH 8.4. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored, and 1248 g of isoprene latex TP-2 was obtained.
When the halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 142 ppm.

  The latex has an average particle size of 113 nm, Tg = 15 ° C., solid content concentration of 41.3 mass%, equilibrium water content at 25 ° C. and 60% RH of 0.4 mass%, ionic conductivity of 5.23 mS / cm (of ionic conductivity). The measurement was conducted at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.).

2. Preparation of coating solution 1) Preparation of coating solution for image forming layer 1000 g of fatty acid silver dispersion, 135 ml of water, 24 ml of 5% by weight aqueous solution of blue dye-2, 5 g and 36 g of azomethine dye solid dispersion, dispersion of organic polyhalogen compound-1 25 g, organic polyhalogen compound-2 dispersion 39 g, phthalazine compound-1 solution 171 g, SBR latex (TP-1) solution 318 g, isoprene latex (TP-2) solution 742 g, reducing agent-2 dispersion 153 g, hydrogen bonding 22 g of Compound-1 dispersion, 4.8 g of development accelerator-1 dispersion, 5.2 g of development accelerator-2 dispersion, 2.1 g of color tone modifier-1 dispersion, and 8 ml of mercapto compound-2 aqueous solution were sequentially added. Immediately before coating, 140 g of silver halide mixed emulsion A 140 g was added and mixed well, and the image forming layer coating solution was directly fed to the coating die and coated. did.

2) Preparation of intermediate layer coating solution 1000 g of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), 27 mL of 5% aqueous solution of di (2-ethylhexyl) sodium salt of sulfosuccinate, polymer dispersion LT-1 as shown in Table 1 Add 4200 mL of LT-13, add 135 mL of 20% by weight aqueous solution of diammonium phthalate salt, add water so that the total amount is 10,000 g, and adjust with NaOH so that the pH is 7.5 to obtain an intermediate layer coating solution. The solution was fed to the coating die so as to be 8.9 mL / m ² .
The viscosity of the coating solution was 58 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3) Preparation of surface protective layer first layer coating solution 100 g of inert gelatin and 10 mg of benzoisothiazolinone were dissolved in 704 mL of water, 146 g of benzotriazole silver dispersion was added, and polymer dispersion LT-1 was added as shown in Table 1. ~ LT-13 180g, phthalic acid 15% by weight methanol solution 46mL, sulfosuccinic acid di (2-ethylhexyl) sodium salt 5% by weight aqueous solution 5.4mL was added and mixed. A mixture of 40 ml of chrome alum with a static mixer was fed to the coating die so that the amount of the coating solution was 35 ml / m ² .
The viscosity of the coating solution was 20 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

4) Preparation of surface protective layer second layer coating solution 100 g of inert gelatin and 10 mg of benzoisothiazolinone are dissolved in 800 mL of water, and the liquid paraffin emulsion is 8.0 g as liquid paraffin, and polymer dispersion LT as shown in Table 1 -1 to LT-13 180 g, phthalic acid 15% by mass methanol solution 40 mL, 1% by mass solution of fluorosurfactant (F-1) 5.5 mL, 1 of fluorosurfactant (F-2) 5.5 mL of a mass% aqueous solution, 28 mL of a 5 mass% aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate, 4 g of polymethyl methacrylate fine particles (average particle size 0.7 μm), and polymethyl methacrylate fine particles (average particle size 4. a mixture of 5 [mu] m) 21g and the surface protective layer coating solution was fed to a coating die to provide 8.3 mL / ^{m 2} .
The viscosity of the coating solution was 19 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3. Preparation of photothermographic materials 1 to 19 Simultaneously layered by the slide bead coating method in the order of the image forming layer, the intermediate layer, the surface protective layer first layer, and the surface protective layer second layer from the undercoat surface to the surface opposite to the back surface The sample was applied to prepare a photothermographic material sample. At this time, the coating solution for the image forming layer and the intermediate layer was adjusted to 31 ° C., the coating solution for the first surface protective layer was adjusted to 36 ° C., and the coating solution for the second surface protective layer was adjusted to 37 ° C.
The coating amount (g / m ² ) of each compound in the image forming layer is as follows.

Fatty acid silver 5.27
Blue dye compound-2 0.25
Magenta dye solid dispersion 0.09
Polyhalogen compound-1 0.14
Polyhalogen compound-2 0.28
Phthalazine Compound-1 0.18
SBR latex (TP-1) 2.83
Isoprene latex (TP-2) 6.60
Reducing agent-2 0.77
Hydrogen bonding compound-1 0.112
Development accelerator-1 0.019
Development accelerator-2 0.016
Color tone adjusting agent-1 0.006
Mercapto compound-2 0.003
Silver halide (as Ag) 0.13

The coating and drying conditions are as follows.
The coating was performed at a speed of 160 m / min, the gap between the coating die tip and the support was set to 0.10 mm to 0.30 mm, and the pressure in the decompression chamber was set to be 196 Pa to 882 Pa lower than the atmospheric pressure. The support was neutralized with an ion wind before coating. In the subsequent chilling zone, the coating liquid is cooled with a wind at a dry bulb temperature of 10 ° C. to 20 ° C., then transported in a non-contact manner, and dried at a dry bulb temperature of 23 ° C. to 45 ° C. It dried with the drying wind of 15 degreeC and the wet-bulb temperature of 15 to 21 degreeC. After drying, the humidity was adjusted at 25 ° C. and humidity of 40% RH to 60% RH, and then the film surface was heated to 70 ° C. to 90 ° C. After heating, the film surface was cooled to 25 ° C.

  The chemical structures of the compounds used in the examples of the present invention are shown below.

4). Evaluation of performance 4-1. Evaluation of coated surface condition For each polymer dispersion, a coated sample was prepared using two types, immediately after preparation and after standing for 6 months at room temperature. The coated sample was exposed and developed so as to have a density of 1.0, and foreign matter failures were visually observed to determine the number of foreign matter failures having a size of 100 μm or more per 10 m ^{2 of the} photothermographic material. .

4-2. Evaluation of photographic performance <Preparation>
The obtained sample was cut into half-cut sizes, packaged in the following packaging materials in an environment of 25 ° C. and 50% RH, stored at room temperature for 2 weeks, and then evaluated as follows.
<Packaging materials>
Laminate film consisting of PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 2% by mass of carbon:
Oxygen permeability: 0.02 mL / atm · m ² · 25 ° C · day;
Moisture permeability: 0.10 g / atm · m ² · 25 ° C · day.

<Exposure and development of photothermographic material>
Each sample was exposed by Fuji Medical Co., Ltd. dry laser imager DRYPIX7000 (mounted with a 660 nm semiconductor laser with a maximum output of 50 mW (IIIB)) and heat developed (three panel heaters set at 107 ° C-121 ° C-121 ° C) 14 seconds in total), and the obtained image was evaluated with a densitometer.

<Cover>
This is the density of the unexposed area.
<Sensitivity>
The reciprocal of the exposure amount for obtaining a density of fog + 1.0 was taken as sensitivity, and expressed as a relative value with respect to Sample 1.

<Evaluation of raw storage stability>
Each sample was stored for 7 days under the conditions of 50 ° C. and 40% RH in the above packaging bag as a forced storage condition, and then the photographic performance was evaluated by taking out from the bag.

4-3. Evaluation results The results obtained are shown in Table 1.
It was clear that the sample of the present invention had excellent photographic properties while having a small environmental load and excellent pot life of the material.
On the other hand, in Comparative Samples 1 and 6, bacteria were not detected from the polymer dispersion, and the storage stability of the dispersion was good, but the coated surface was poor. Further, Comparative Samples 2 and 3 had a large number of bacteria, and the coated surface was also poor.

Example 2
Samples obtained by changing the ethyl acrylate / acrylic acid copolymer (copolymerization mass ratio 64/4) latex of the back surface protective layer to the polymer latexes LT-1 to LT-13 of Example 1 in Sample 5 of Example 1 Produced.
As a result of evaluating the performance in the same manner as in Example 1, the sample using the polymer latex LT-7 to 13 according to the present invention was particularly good as the back surface.

Example 3
1. Preparation of Matting Agent <Comparative Example; MT-1>
To 860 mL of water, add 250 g of polymethyl methacrylate particles (particle size 6 μm) powder, 530 g of gelatin aqueous solution (19% by mass), 17 g of ABS-1 (30% by mass), and 100 ppm of benzoisothiazolinone, and use a homogenizer. Dispersion was carried out to obtain 1.7 kg of matting agent dispersion MT-1.

<Comparative example: MT-2 and present invention MT-3-7>
MT-2 to 7 were prepared in the same manner as MT-1 except that the surfactant type, the preservative amount, and the container cleaning method were changed as shown in Table 2.

2. Production of photothermographic material Except for Sample 5 of Example 1, the matting agent polymethyl methacrylate fine particles (average particle size 0.7 μm) and polymethyl methacrylate fine particles (average particle size 4.5 μm) of the surface protective second layer were excluded. Instead, Samples 21 to 27 were produced in the same manner as Sample 5 of Example 1 except that the matting agent prepared above was used.

3. Performance evaluation <Evaluation of coated surface>
About each mat agent dispersion, the sample apply | coated using two types immediately after preparation and after leaving for 6 months at 10 degreeC after preparation was produced. The coated sample was exposed and developed so as to have a density of 1.0, and foreign matter failures were visually observed to determine the number of foreign matter failures having a size of 100 μm or more per 10 m ^{2 of the} photothermographic material. .
For other evaluation items, the same evaluation as in Example 1 was performed.
The obtained results are shown in Table 2.
It was clear that the sample of the present invention had excellent photographic properties while having a small environmental load and excellent pot life of the material.
On the other hand, comparative sample MT-2 was inferior in the pot life of the material, which was not preferable.

Example 4
Samples obtained by changing the monodisperse polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4) of the back layer to the matting agents MT-1 to MT-7 of Example 3 in the sample 23 of Example 3. Produced.
As a result of evaluating the performance in the same manner as in Example 3, the samples using the matting agents MT-2 to MT-7 according to the present invention were particularly good as the coated surface of the back surface.

Claims (14)

  A method for producing a photothermographic material comprising, on one side of a support, at least a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent for the organic silver salt, Polymer dispersion in which the material contains 0.01% by mass or more of a surfactant whose biochemical oxygen demand (BOD value) is 60% or more of the theoretical oxygen demand (ThOD value) and 10 ppm or more and 500 ppm or less of a preservative. The manufacturing method includes at least a step of storing the polymer dispersion in a container, a step of removing the polymer dispersion from the container to prepare a coating solution, and a step of applying and drying the coating solution. A method for producing a photothermographic material, wherein a sterilized container is used as a container for storing the polymer dispersion.   2. The method for producing a photothermographic material according to claim 1, wherein the surfactant does not contain two or more tertiary or quaternary carbons.   3. The method for producing a photothermographic material according to claim 1, wherein the concentration of the surfactant in the polymer dispersion is 0.01% by mass or more and 5.0% by mass or less.   4. The method for producing a photothermographic material according to claim 1, wherein the preservative is an isothiazolinone preservative.   5. The method for producing a photothermographic material according to claim 4, wherein the preservative is benzoisothiazolinone.   The photothermographic material according to claim 1, wherein the concentration of the preservative in the polymer dispersion is 0.001% by mass or more and 0.05% by mass or less. Manufacturing method.   The method for producing a photothermographic material according to claim 1, wherein the polymer dispersion is a polymer latex.   8. The method for producing a photothermographic material according to claim 7, wherein the polymer latex is an acrylic resin latex.   8. The method for producing a photothermographic material according to claim 7, wherein the polymer latex is SBR latex.   8. The method for producing a photothermographic material according to claim 7, wherein the polymer latex is isoprene latex.   The method for producing a photothermographic material according to claim 1, wherein the polymer dispersion is a polymer matting agent.   The method for producing a photothermographic material according to claim 1, wherein the sterilization process is a heat sterilization process.   The method for producing a photothermographic material according to claim 1, wherein the coating solution contains gelatin.   A photothermographic material produced by the production method according to any one of claims 1 to 13.