JP2006215168A - Heat developable photosensitive material and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material having high sensitivity and excellent image preservability, and also to provide an image forming method. <P>SOLUTION: The heat developable photosensitive material has an image forming layer at least including photosensitive silver halide, a nonphotosensitive organic silver salt, a reducing agent, and a binder. The average silver iodide content in the photosensitive silver halide is ≥40 mol%, and a compound expressed by general formula (I) or the salt thereof is comprised. In the formula, R<SB>1</SB>and R<SB>1</SB>' are a hydrogen atom, or a substituted or unsubstituted alkyl group, aryl group or hetero ring group, independently of each other; wherein, they are not simultaneously a hydrogen atom. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material and an image forming method, and more particularly to a photothermographic material and an image forming method having high sensitivity and improved image storage stability.

  In recent years, in the medical diagnostic film field and the photoengraving film field, it is strongly desired to reduce the amount of processing waste liquid from the viewpoint of environmental protection and space saving. Therefore, heat as a medical diagnostic film and a photoengraving film that can be efficiently exposed by a laser image setter or a laser imager and can form a clear black image with high resolution and sharpness. There is a need for techniques relating to developed image recording materials. According to these heat-developable image recording materials, a heat-development processing system that does not require solution-based processing chemicals and that is simpler and does not impair the environment can be supplied to customers.

  There are similar demands in the field of general image recording materials, but medical diagnostic images in particular require fine depiction, so they require high image quality with excellent sharpness and graininess, and ease of diagnosis. From the viewpoint, a cool black 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, but none of them are satisfactory as a medical image output system.

  On the other hand, thermal imaging systems using organic silver salts are disclosed in, for example, U.S. Pat. Nos. 3,152,904 and 3,457,075 and D.C. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials), 8th edition, J. Sturge. (Walworth, A. Shepp, Chapter 9, 279, 1989). In particular, the photothermographic material generally contains a catalytically active amount of a photocatalyst (for example, silver halide), a reducing agent, a reducible silver salt (for example, an organic silver salt), and, if necessary, a toning agent that controls the color tone of silver. 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 a black silver image is formed by a redox reaction between a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form. 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.

  Such a photothermographic material using an organic silver salt has the great advantage that all components necessary for image formation are contained in the film in advance and an image can be formed only by heating. In order to avoid turbidity and opacification of the film due to light scattering and light absorption of silver halide grains, it is necessary to keep the amount of coating fine in a small amount, and there is a limit to increasing sensitivity. there were. In addition, various components for image formation remain in the unexposed areas after image formation, and reaction products remain in areas where an image formation reaction has occurred, so improvement in image storage stability is a major problem. there were.

Attempts have been made to apply photothermographic materials to photothermographic materials. The photographic photosensitive material mentioned here is not for writing image information by scanning exposure with a laser beam or the like, but for recording an image by one-shot exposure by camera shooting. Conventionally, it is commonly used in the field of wet-developable photosensitive materials, and in medical applications, various plate-making films for printing, such as direct or indirect X-ray films and mammographic films, industrial recording films, and films for photographing with general cameras are known. Yes. For example, a photothermographic material for double-coated X-rays using a blue fluorescent intensifying screen (see, for example, Patent Document 1), a photothermographic material using silver iodobromide tabular grains (for example, Patent Document) 2), or a medical photosensitive material in which tabular grains having a high silver chloride content and having a (100) main plane are coated on both sides of the support are also disclosed in Patent Literature (for example, see Patent Literature 3). ). The double-side coated photothermographic material is also disclosed in other patent documents (for example, see Patent Documents 4 to 7).
However, for X-ray image recording, the photothermographic material is required to have higher sensitivity in order to reduce the exposure dose. In the prior art described above, an increase in fog is unavoidable if higher sensitivity is desired, and means for keeping the fog low and improving the sensitivity has been demanded.
Further, in the light-sensitive material using a high-sensitivity emulsion, it is particularly difficult to ensure image storability as compared with a light-sensitive material using a low-sensitivity emulsion, and improvement has been desired.
Japanese Patent No. 3229344 JP 59-142539 A JP-A-10-282602 JP 2000-227642 A Japanese Patent Laid-Open No. 2001-22027 JP 2001-109101 A JP 2002-90941 A

  An object of the present inventor is to provide a photothermographic material and an image forming method which have low fog and high sensitivity and are excellent in image storability.

The above problems have been solved by the following means.
<1> A photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder on at least one surface of a support,
1) The average silver iodide content of the photosensitive silver halide is 40 mol% or more,
2) A photothermographic material comprising a compound represented by the following general formula (I) or a salt thereof:

(In the formula, R ₁ and R ₁ ′ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, or a heterocyclic group, provided that they are not simultaneously a hydrogen atom).
<2> The heat according to <1>, wherein in general formula (I), R ₁ ′ is a hydrogen atom, and R ₁ is a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group. Development photosensitive material.
<3> The photothermographic material according to <1> or <2>, wherein 50% or more of the total projected area of the photosensitive silver halide is a tabular grain having an aspect ratio of 2 or more.
<4> The photothermographic material according to <3>, wherein the tabular grains have an average equivalent-circle diameter of 0.3 μm or more and 5.0 μm or less.
<5> Any one of <1> to <4>, wherein the compound represented by the general formula (I) or a salt thereof is a compound represented by the following general formula (II) or a salt thereof. The photothermographic material according to item:

(Wherein R ₂ represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group, R ₃ represents a hydrogen atom or a substituent that can be substituted on a benzene ring, and n1 represents an integer of 1 to 5) N2 represents 0 or an integer of 1 to 4).
<6> The photothermographic material according to <5>, wherein the compound represented by the general formula (II) or a salt thereof is a compound represented by the following general formula (III) or a salt thereof:

(Wherein R ₂ has the same meaning as in formula (II)).
<7> The photothermographic material according to any one of <1> to <6>, wherein the photosensitive silver halide is gold sensitized.
<8> The photothermographic material according to any one of <3> to <7>, wherein the tabular grain has an aspect ratio of 5 to 100.
<9> The photothermographic material according to any one of <1> to <8>, wherein the photosensitive silver halide has an average silver iodide content of 60 mol% or more.
<10> The photothermographic material according to <9>, wherein the photosensitive silver halide has an average silver iodide content of 80 mol% or more.
<11> The photothermographic material according to any one of <1> to <10>, which contains a silver iodide complex forming agent.
<12> In any one of <1> to <11>, containing at least one thermal development accelerator represented by the following general formula (A-1) or (A-2) The photothermographic material described:

(Wherein 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 formula, 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, or an alkylthio group. Represents an arylthio group, an acyloxy group, or a carbonate group, R ₃ and R ₄ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring, and R ₃ and R ₄ are connected to each other to form a condensed ring. You may do it.)
<13> The photothermographic material according to any one of <1> to <12>, wherein the image forming layer is provided on both sides of a support.
<14> An X-ray image forming method using the photothermographic material according to any one of <1> to <13>,
1) a step of superposing the photothermographic material and a fluorescent intensifying screen to perform radiation image exposure and recording a latent image on the photothermographic material;
2) a thermal development step of converting the latent image into a visible image by thermal development;
An image forming method comprising:

  According to the present invention, it is possible to provide a photothermographic material and an image forming method which have low fog and high sensitivity and are excellent in image storability.

Hereinafter, the present invention will be described in detail.
The photothermographic material of the present invention is a photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder on at least one surface of a support. And the average silver iodide content of the said photosensitive silver halide is 40 mol% or more, and contains the compound or its salt represented by the following general formula (I).

In the formula, R ₁ and R ₁ ′ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, or a heterocyclic group. However, they are not simultaneously hydrogen atoms.
R ₁ ′ is preferably a hydrogen atom, and R ₁ is a substituted or unsubstituted alkyl group, aryl group, or hetero group.
Preferably, 50% or more of the total projected area of the photosensitive silver halide is tabular grains having an aspect ratio of 2 or more, more preferably an aspect ratio of 5 or more and 100 or less. Preferably, the average equivalent circle diameter of the tabular grains is 0.3 μm or more and 5.0 μm or less. Preferably, the compound represented by the general formula (I) or a salt thereof is a compound represented by the following general formula (II) or a salt thereof.

In the formula, R ₂ represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group, R ₃ represents a hydrogen atom or a substituent that can be substituted on a benzene ring, and n1 represents an integer of 1 to 5. , N2 represents 0 or an integer of 1 to 4.
More preferably, the compound represented by the general formula (II) or a salt thereof is a compound represented by the following general formula (III) or a salt thereof.

In the formula, R ₂ has the same meaning as in general formula (II).
Preferably, the photosensitive silver halide is gold sensitized.
Preferably, the average silver iodide content of the photosensitive silver halide is 80 mol% or more, and more preferably 90 mol% or more.
Preferably, the photothermographic material of the present invention contains a silver iodide complex forming agent.
Preferably, the photothermographic material of the invention contains at least one kind of heat development accelerator represented by the following general formula (A-1) or (A-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 formula, 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 independently represent a hydrogen atom or a group that can be substituted on a benzene ring. R ₃ and R ₄ may be connected to each other to form a condensed ring.

Preferably, the image forming layer is provided on both sides of the support.
The X-ray image forming method of the present invention comprises a step of superposing the above-mentioned photothermographic material and a fluorescent intensifying screen to perform radiation image exposure, recording a latent image on the photothermographic material, and the latent image by heat development. A heat development step of converting the image into a visible image;

(Description of compound represented by formula (I))
The photothermographic material of the present invention contains a compound represented by the general formula (I) or a salt thereof.

In the formula, R ₁ and R ₁ ′ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, or a heterocyclic group. However, they are not simultaneously hydrogen atoms.
In the general formula (I), R ₁ ′ is a hydrogen atom, and R ₁ is a substituted or unsubstituted alkyl group, aryl group, or hetero group. Preferably, the compound represented by the general formula (I) or a salt thereof is a compound represented by the following general formula (II) or a salt thereof.

In the formula, R ₂ represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group, R ₃ represents a hydrogen atom or a substituent that can be substituted on a benzene ring, and n1 represents an integer of 1 to 5. , N2 represents 0 or an integer of 1 to 4.
More preferably, the compound represented by the general formula (II) or a salt thereof is a compound represented by the following general formula (III) or a salt thereof.

In the formula, R ₂ has the same meaning as in general formula (II).
Examples of salts of the compounds represented by the general formulas (I), (II), and (III) include alkali metal salts (for example, lithium, sodium, potassium, etc.), ammonium salts, alkylammonia salts, phosphonium salts, and Metal salts (for example, salts of zinc, copper, mercury, silver, etc.) are preferred.

The general formulas (I), (II), and (III) will be described in detail below.
The alkyl group represented by R ₁ in the general formula (I) may be linear or branched. Examples of the alkyl group include butyl group, isobutyl group, hexyl group, hebutyl group, octyl group, dodecyl group, pentadecyl group. Examples of the substituent of the substituted alkyl group include an alkoxy group (such as a methoxy group), an acetylene group or a salt thereof, an aryloxy group, an acyloxy group, a heterocyclic oxy group, a hydroxy group, a carboxyl group, or the like Salt, formyl group, acyl group, substituted or unsubstituted carbamoyl group, alkoxycarbonyl group, aryloxycarbonyl group, mercapto group, alkylthio group, arylthio group, sulfino group or salt thereof, sulfo group or salt thereof, alkylsulfinyl group, Alkylsulfonyl group, arylsulfonyl group, substituted or unsubstituted Sulfamoyl group, alkoxysulfonyl group, aryloxysulfonyl group, acylamino group, substituted or unsubstituted ureido group, alkoxycarbonylamino group, aryloxycarbonylamino group, nitro group, nitroso group, cyano group, halogen atom, alkylsulfonylamino group , Arylsulfonylamino group, substituted or unsubstituted sulfamoylamino group, substituted or unsubstituted amino group, cycloalkyl group, alkenyl group, aryl group, aralkyl group, heterocyclic group, alkynyl group (for example, ethynyl group), etc. It is. Two or more of these substituents may be present.

Examples of the cycloalkyl group represented by R ₁ include a cyclobenzyl group, a cyclohexyl group, a decahydronaphthyl group and the like; examples of the alkenyl group include a propenyl group, an isopropenyl group and a styryl group; examples of the alkynyl group include an ethynyl group , Phenylethynyl group and the like; examples of the aralkyl group include a benzyl group and a phenethyl group. These groups may have the substituent described for the alkyl group. There may be two or more substituents.

Examples of the aryl group of R ₁ include a phenyl group and a naphthyl group. Examples of the substituent of the substituted aryl group include an alkyl group (such as a methyl group and a dodecyl group), an alkenyl group, an aryl group, and a cycloalkyl group. Group, aralkyl group, alkynyl group, cyano group, nitro group, nitroso group, substituted or unsubstituted amino group, acylamino group, acetylene group or salt thereof, alkylsulfonylamino group, arylsulfonylamino group, substituted or unsubstituted sulfur Famoylamino group, hydroxyl group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, heterocyclic oxy group, acyloxy group, heterocyclic group (5 to 6 membered ring, particularly nitrogen-containing heterocyclic ring is preferred) , Alkoxysulfonyl group, aryloxysulfonyl group, alkylsulfinyl group Arylsulfinyl group, alkylthio group, arylthio group, mercapto group, formyl group, acyl group, alkylsulfonyl group, arylsulfonyl group, carboxylic acid group or salt thereof, sulfonic acid group or salt thereof, sulfino group or salt thereof, halogen atom ( Fluorine, bromine, chlorine, iodine), substituted or unsubstituted ureido group, carbamoyl group, sulfamoyl group, and the like.
These substituents may be further substituted. There may be two or more substituents as exemplified above.

The heterocyclic group of R ₁ is preferably a 5-membered or 6-membered group, and examples thereof include a furyl group, a thienyl group, a benzothienyl group, a pyridyl group, and a quinoline group. These heterocyclic groups may have the same substituent as the above substituted aryl group.

Hereinafter, R ₂ in the general formula (II) will be described in detail.
In the case of an alkyl group, it may be linear or branched. Examples of the alkyl group include propyl group, isopropyl group, butyl group, isobutyl group, tertiary butyl group, benzyl group, hexyl group, hebutyl group, isohebutyl. Group, octyl group, nonyl group, decyl group, dodecyl group, or pentadecyl group. Examples of the substituent of the substituted alkyl group include cycloalkyl group, alkenyl group, alkynyl group, aryl group, aralkyl group, heterocyclic group, halogen atom (fluorine, chlorine, bromine, iodine), hydroxyl group, alkoxy group, aryl Oxy group, acyloxy group, heterocyclic oxy group, carboxyl group or salt thereof, formyl group, acyl group, substituted or unsubstituted carbamoyl group, alkoxycarbonyl group, aryloxycarbonyl group, cyano group, mercapto group, alkylthio group, arylthio Group, sulfino group or salt thereof, sulfo group or salt thereof, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, substituted or unsubstituted sulfamoyl group, alkoxysulfonyl group, aryloxysulfonyl group, substituted or Substituted amino group, acylamino group, substituted or unsubstituted ureido group, alkoxycarbonylamino group, aryloxycarbonylamino group, alkylsulfonylamino group, arylsulfonylamino group, substituted or unsubstituted sulfamoylamino group, nitro group Nitroso group and the like. Two or more of these groups may be present, and the substituents may be further substituted.

  Examples of the cycloalkyl group include a cyclobenzyl group, a cyclohexyl group, a decahydronaphthyl group, and the like; examples of the alkenyl group include a propenyl group, an isopropenyl group, and a styryl group. These groups may have the substituent described for the alkyl group. Two or more substituents may be present.

Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the substituent of the substituted aryl group include an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group, and a heterocyclic group. (5-membered to 6-membered ring, preferably nitrogen-containing heterocycle), halogen atom (fluorine, chlorine, bromine, iodine), hydroxyl group, alkoxy group, aryloxy group, acyloxy group, heterocyclic oxy group, carboxyl group or Salt, formyl group, acyl group, substituted or unsubstituted carbamoyl group, alkoxycarbonyl group, aryloxycarbonyl group, cyano group, mercapto group, alkylthio group, arylthio group, sulfino group or salt thereof, sulfo group or salt thereof, Alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, ant Rusulfonyl group, substituted or unsubstituted sulfamoyl group, alkoxysulfonyl group, aryloxysulfonyl group, substituted or unsubstituted amino group, acylamino group, substituted or unsubstituted ureido group, alkoxycarbonylamino group, aryloxycarbonylamino group Alkylsulfonylamino group, arylsulfonylamino group, substituted or unsubstituted sulfamoylamino group, nitro group, nitroso group and the like.
These substituents may be further substituted. There may be two or more substituents as exemplified above.

  Examples of aralkyl groups include benzyl and phenethyl groups. These substituents may have one or more substituents described for the alkyl group or aryl group, and the substituents may be further substituted.

  The heterocyclic group is preferably a 5-membered or 6-membered group such as a furyl group, a thienyl group, a benzothienyl group, a pyridyl group, or a quinoline group. These heterocyclic groups may have the same substituent as the above substituted aryl group.

Examples of alkylene groups are methylene, ethylene, trimethylene, propylene, etc .; examples of arylene are (o ⁻ , m ⁻ , p ⁻ ) phenylene, (1,4-etc.) Naphthylene, etc. Examples of cycloalkylene groups include cyclohexylene groups.

  The above divalent residue may have one or more of the substituents described for the alkyl group and aryl group, and the substituents may be further substituted.

Among these, R ₃ is preferably a compound having an alkyl group or a cycloalkyl group having 3 or more carbon atoms. More preferably, R ₃ is a compound having 3 to 10 carbon atoms or a cycloalkyl group.

R ₃ in the general formula (III) is an alkyl group (methyl group, dodecyl group, etc.), alkenyl group, aryl group, cycloalkyl group, aralkyl group, alkynyl group, cyano group, nitro group, nitroso group, substituted or non-substituted Substituted amino group, acylamino group, alkylsulfonylamino group, arylsulfonylamino group, substituted or unsubstituted sulfamoylamino group, hydroxyl group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, heterocyclic oxy group , Acyloxy group, heterocyclic group (5- to 6-membered ring, preferably nitrogen-containing heterocyclic ring), alkoxysulfonyl group, aryloxysulfonyl group, alkylsulfinyl group, arylsulfinyl group, alkylthio group, arylthio group, mercapto group , Formyl group, acyl group Alkylsulfonyl group, arylsulfonyl group, carboxylic acid group or salt thereof, sulfonic acid group or salt thereof, sulfino group or salt thereof, halogen atom (fluorine, bromine, chlorine, iodine), substituted or unsubstituted, ureido group, carbamoyl Group, sulfamoyl group and the like.
These substituents may be further substituted. There may be two or more substituents as exemplified above.

n1 is preferably 1 or 2. n2 is preferably 0.
Specific examples of the present invention are shown below.

  The acetylene compound represented by the general formula (III) in the present invention can be easily obtained from the condensation reaction of the following 4-ethynylaniline and an acid chloride of carboxylic acid.

  4-Ethynylaniline can be synthesized by the method described in HELVETICA CHIMICA ACTA, 54, 2066 (1971).

<Addition method>
The compound represented by formula (I) in the present invention may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, and a solid fine particle dispersion form, and may be contained in the photothermographic material.
Well-known emulsification and dispersion methods include oils such as dibutyl phthalate, tricresyl phosphate, dioctyl sebacate or tri (2-ethylhexyl) phosphate, and dissolution using an auxiliary solvent such as ethyl acetate or cyclohexanone, and dodecylbenzene. Examples thereof include a method of mechanically preparing an emulsified dispersion by adding a surfactant such as sodium sulfonate, oleoyl-N-methyl taurate, sodium di (2-ethylhexyl) sulfosuccinate. At this time, it is also preferable to add a polymer such as α-methylstyrene oligomer or poly (t-butylacrylamide) for the purpose of adjusting the viscosity and refractive index of the oil droplets.

In addition, as a solid fine particle dispersion method, the powder of the compound represented by the general formula (I) is dispersed in a suitable 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. And a method of producing a solid dispersion. 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 content of Zr 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).

<Additive layer>
The compound represented by the general formula (I) in the present invention is contained in any layer on the side having the image forming layer of the support. It is preferably added to the image forming layer or its adjacent layer, more preferably added to the image forming layer.

<Addition amount>
The addition amount of the compound represented by the general formula (I) in the present invention is 1.0 × 10 ⁻⁸ mol to 1.0 × 10 ⁻¹ mol per mol of the photosensitive silver halide. Preferably, it is 1.0 × 10 ⁻⁷ mol to 1.0 × 10 ⁻² mol, more preferably 1.0 × 10 ⁻⁶ mol to 1.0 × 10 ⁻² mol.

(Description of 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, 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 making the stearic acid content 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 stearic acid 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. In addition, short needle-shaped, rectangular parallelepiped, cubic or potato-shaped irregular particles having a major axis / uniaxial length ratio of less than 5 are also 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 length of the major axis to the uniaxial axis is 5 or more. 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, and the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped. 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 sphere equivalent 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 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, 2001-163825, 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 during the dispersion.
In the present invention, the amount of the photosensitive silver salt in the aqueous dispersion to be dispersed is preferably 1 mol% or less, more preferably 0.1 mol% relative to 1 mol of the organic acid silver salt in the liquid. The following is more preferable, and positive addition of 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 2 mol% to 20 mol%, and particularly preferably 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 Although the organic silver salt in the present invention can be used in a desired amount, the total coating silver amount including silver halide is preferably 0.1 g / m ² or more and 5.0 g / m ² or less, more preferably. It is 0.3 g / m ² or more and 3.0 g / m ² or less, more preferably 0.5 g / m ² or more and 2.0 g / m ² or less. In particular, in order to improve image storability, the total coated silver amount is preferably 1.8 g / m ² or less, more preferably 1.6 g / m ² or less. If the preferred reducing agent in the present invention is used, a sufficient image density can be obtained even with such a low silver amount.

(Description of reducing agent)
The photothermographic material of the present invention preferably contains a heat developer which is a reducing agent for the organic silver salt. The reducing agent for the organic silver salt 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 represents 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 a benzene ring. L represents a —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.
When referred to as an alkyl group in the following, a cycloalkyl group is also included in this unless otherwise specified.
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. The substituent of the alkyl group is not particularly limited, but preferably an aryl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acylamino group, a sulfonamido group, a sulfonyl group, a phosphoryl group, Examples thereof include an acyl group, a carbamoyl group, an ester group, a ureido group, a urethane group, and a halogen atom.

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 that can be substituted on a benzene ring, and X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group that can be substituted on 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 of 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, 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, Examples thereof include a carbamoyl group and a sulfamoyl group.

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 can be mentioned. R ¹¹ and R ¹¹ ′ are more preferably an alkyl group having 1 to 8 carbon atoms, and among them, a methyl group, a t-butyl group, a t-amyl group, and a 1-methylcyclohexyl group are more preferable, and a methyl group and a t-butyl group are preferable. The group is most preferred.

R ¹² and R ¹² ′ are preferably an alkyl group having 1 to 20 carbon atoms, and specifically include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a t-butyl group, a t-amyl group, and 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, an ethyl group, a propyl group, an isopropyl group, a 2,4,4-trimethylpentyl group, a cyclohexyl group, a 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, 2,4-dimethyl-3-cyclohexenyl group and the like).
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 color 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 in this invention including the compound represented by general formula (R) below is shown, this invention is not limited to these.

Examples of preferable reducing agents in 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.
In the present invention, the addition amount of the reducing agent is preferably 0.1 g / m ² or more and 3.0 g / m ² or less, more preferably 0.2 g / m ² or more and 2.0 g / m ² or less, and still more preferably. Is 0.3 g / m ² or more and 1.0 g / m ² or less. 5 mol% or more and 50 mol% or less is preferably contained with respect to 1 mol of silver on the surface having the image forming layer, more preferably 8 mol% or more and 30 mol% or less, and 10 mol% or more and 20 mol% or less. More preferably, it is contained. 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 emulsification and dispersion methods include oils such as dibutyl phthalate, tricresyl phosphate, dioctyl sebacate or tri (2-ethylhexyl) phosphate, and dissolution using an auxiliary solvent such as ethyl acetate or cyclohexanone, and dodecylbenzene. Examples thereof include a method of mechanically preparing an emulsified dispersion by adding a surfactant such as sodium sulfonate, oleoyl-N-methyl taurate, sodium di (2-ethylhexyl) sulfosuccinate. At this time, it is also preferable to add a polymer such as α-methylstyrene oligomer or poly (t-butylacrylamide) for the purpose of adjusting the viscosity and refractive index of the oil droplets.

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 content of Zr 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, in which 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 are added. Is preferred. In the present application, it is preferable to use other solid dispersions dispersed in a particle size within this range.

(Description of development accelerator)
The photothermographic material of the invention preferably contains a development accelerator. As a development accelerator, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, etc., or a general formula described in JP-A-2001-92075. Hindered phenol compounds represented by (II), general formula (I) described in JP-A-10-62895, JP-A-11-15116, etc., and general formulas in JP-A-2002-156727 (D), a hydrazine-based compound represented by the general formula (1) described in JP-A-2002-278017, and a general formula (2) described in JP-A-2001-264929. Phenol-based or naphthol-based compounds are preferably used. Moreover, the phenol type compound described in Unexamined-Japanese-Patent No. 2002-311533 and Unexamined-Japanese-Patent No. 2002-341484 is also preferable. In particular, naphthol compounds described in JP-A No. 2003-66558 are preferable. These development accelerators are used in the range of 0.1 mol% or more and 20 mol% or less, preferably 0.5 mol% or more and 10 mol% or less, more preferably 1 mol% or more with respect to the reducing agent. The range is 5 mol% or less. 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 that does not use a high-boiling solvent. It is preferable to add.
In the present invention, among the above development accelerators, hydrazine compounds described in JP-A Nos. 2002-156727 and 2002-278017 and naphthol compounds described in JP-A No. 2003-66558 are used. Is more preferable.

Particularly preferred development accelerators in the invention are compounds represented by the following general formulas (A-1) and (A-2).
Formula (A-1)
Q ₁ -NHNH-Q ₂
(Wherein 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 preferred, 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 Butylphenyl) 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, such as formyl, acetyl, 2-methylpropanoyl, cyclohexylcarbonyl, octanoyl, 2 -Hexyldecanoyl, dodecanoyl, chloroacetyl, trifluoroacetyl, benzoyl, 4-dodecyloxybenzoyl, 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 thereof 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- Examples include 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, N- (2-tetradecyloxyphenyl) sulfamoyl is mentioned. 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 the 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 independently represent a hydrogen atom or 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, a cyclohexyl group, etc.), an acylamino group (for example, an acetylamino group, a benzoylamino group, a methyl group). Ureido group, 4-cyanophenylureido group, etc.), carbamoyl group (n-butylcarbamoyl group, N, N-diethylcarbamoyl group, phenylcarbamoyl group, 2-chlorophenylcarbamoyl group, 2,4-dichlorophenylcarbamoyl group, etc.) acylamino Groups (including ureido groups and urethane groups) are more preferred. R ₂ is preferably a halogen atom (more preferably a chlorine atom or a bromine atom), an alkoxy group (for example, a methoxy group, a butoxy group, an n-hexyloxy group, an n-decyloxy group, a cyclohexyloxy group, a benzyloxy group), aryl An oxy group (phenoxy group, naphthoxy group, etc.).
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, 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, a naphthalene ring is particularly preferable as the condensed 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-based 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 in the present invention will be given. The present invention is not limited to these.

(Description of hydrogen bonding compounds)
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 aforementioned bisphenols, these groups and hydrogen bonds It is preferable to use together a non-reducing compound having a group capable of forming.
Examples of the group that forms a hydrogen bond with a hydroxyl group or an amino group include a phosphoryl group, a sulfoxide group, a sulfonyl group, a carbonyl group, an amide group, an ester group, a urethane group, a ureido group, a tertiary amino group, and a nitrogen-containing aromatic group. Can be 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 has no> 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, examples of the substituent include a halogen atom, an alkyl group, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamide group, an acyloxy group, 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, and a t-octyl group. Group, phenyl group, 4-alkoxyphenyl group, 4-acyloxyphenyl group and the like.
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 include 1-methylcyclohexyl group, benzyl group, phenethyl group, and 2-phenoxypropyl group.
Examples of the aryl group include phenyl group, cresyl group, xylyl group, naphthyl group, 4-t-butylphenyl group, 4-t-octylphenyl group, 4-anisidyl group, and 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 a phenoxy group, a cresyloxy group, an isopropylphenoxy group, a 4-t-butylphenoxy group, a naphthoxy group, and a 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. In view of the effects 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. Further, 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) in 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. These compounds form a hydrogen-bonding complex with a compound having a phenolic hydroxyl group or an amino group in a solution state. It can be isolated in the 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. Further, a method in which the reducing agent and the compound of the general formula (D) in 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) in 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%, based on the reducing agent. More preferably, it is the range of 20 mol% or more and 100 mol%.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose may be added to the image forming layer of the photothermographic material of the invention. The amount of these hydrophilic polymers added is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total binder of the image forming layer.

  The organic silver salt-containing layer (that is, the image forming layer) in the present invention is preferably formed using a polymer latex. The amount of binder in the image forming layer is such that the total binder / organic silver salt mass ratio is 1/10 to 10/1, more preferably 1/3 to 5/1, and still more preferably 1/1 to 3/1. Range.

  Further, such an organic silver salt-containing layer is usually a photosensitive layer (image forming layer) containing a photosensitive silver halide that is a photosensitive silver salt. The mass ratio of silver halide is 400-5, more preferably 200-10.

The total binder amount of the image forming layer in the present invention is preferably 0.2 g / m ² or more and 30 g / m ² or less, more preferably 1 g / m ² or more and 15 g / m ² or less, and further preferably 2 g / m ² or more and 10 g. / M ² or less. In the image forming layer of the present invention, a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like may be added.

(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 50% 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%).

(Photosensitive silver halide)
The photosensitive silver halide in the present invention is a tabular grain having an average silver iodide content of 40 mol% or more, preferably 50% or more of the total projected area having an aspect ratio of 2 or more. Preferably, it is a tabular grain having an average equivalent circle diameter of 0.3 μm or more and 5.0 μm or less.
More preferably, the aspect ratio is 5 or more and 100 or less. The average silver iodide content is preferably 60 mol% or more, more preferably 80 mol% or more.
Preferably, the photosensitive silver halide in the present invention is gold sensitized.

The photosensitive silver halide grains in the present invention will be described in more detail.
1) Silver halide tabular grains In the present invention, a silver halide tabular grain (hereinafter referred to as "tabular grain") refers to a silver halide grain having two opposing parallel main surfaces.
These tabular grains are often hexagonal, triangular, square, rectangular or round when they are viewed from a direction perpendicular to the main surface. There is no problem even if it exists. However, in order to uniformly perform epitaxial sensitization between grains, it is preferable that the size and shape be monodispersed as much as possible.

In the present invention, a tabular grain means a silver halide grain having an aspect ratio (equivalent circle diameter / thickness of main plane) of 2 or more. The equivalent-circle diameter of the tabular grains is obtained, for example, by taking a transmission electron micrograph by the replica method to obtain the diameter of a circle having an area equal to the projected area of each grain (equivalent circle diameter).
The thickness cannot be calculated simply from the length of the shadow of the replica due to epitaxial deposition. However, it can be calculated by measuring the length of the shadow of the replica before epitaxial deposition. Alternatively, even after epitaxial deposition, the sample coated with tabular grains can be cut and easily taken by taking an electron micrograph of the cross section.
If the aspect ratio is 2 or more, it corresponds to the tabular grain in the present invention, but preferably the aspect ratio is 5 or more and 100 or less, more preferably the aspect ratio is 7 or more and 100 or less, and most preferably the aspect ratio is 10 or more and 100 or less. Tabular grains.

2) Halogen composition The halogen composition of the tabular grains in the present invention is such that the silver iodide content is as high as 40 mol% or more. The rest is not particularly limited and can be selected from silver halides such as silver chloride and silver bromide, or organic silver salts such as silver thiocyanate and silver phosphate, but in particular silver bromide, silver chloride and silver thiocyanate. Preferably there is. The silver iodide content here is the silver iodide content contained in the silver halide grains including the epitaxial portion. By using silver halide having a composition having a high silver iodide content, a preferable photothermographic material can be designed in which image storage stability after development processing, in particular, an increase in fog due to light irradiation is remarkably small.

  The halogen composition of the tabular grains in the present invention preferably has a silver iodide content of 60 mol% or more, most preferably 80 mol% or more.

  As a method for examining the halogen composition in silver halide crystals, an X-ray diffraction method is generally known. The X-ray diffraction method is described in detail in Basic Analytical Chemistry Course 24 “X-ray diffraction” and the like. Typically, the diffraction angle is determined by a powder method using Cu Kβ rays as a radiation source.

When the diffraction angle 2θ is obtained, the lattice constant a is obtained from the black equation as follows.
2 dsin θ = λ
d = a / (h ² + k ² + l ² ) ^1/2
Here, 2θ is the diffraction angle of the (hkl) plane, λ is the X-ray wavelength, and d is the surface spacing of the (hkl) plane. Since the relationship between the halogen composition of the silver halide solid solution and the lattice constant a is already known (for example, it is described in TH James, “The Theory of Photographic Process. 4th Ed.”, Macmillian, New York). ) If the lattice constant is known, the halogen composition can be determined.

  The tabular grains in the present invention can have an arbitrary β phase and γ phase content. The β phase refers to a high silver iodide structure having a hexagonal wurtzite structure, and the γ phase refers to a high silver iodide structure having a cubic zinc blend structure. The γ phase content here is C.I. R. It is determined using the method proposed by Berry. This method is determined based on the peak ratio of the silver iodide β phase (100), (101), (002) and the γ phase (111) in the powder X-ray diffraction method. Physical Review, Vol. 161, no. 3, p. Reference may be made to 848-851 (1967).

In the tabular grains in the present invention, the distribution of the halogen composition of the host tabular 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 also 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 core high silver iodide structure having a high silver iodide content in the core part or a shell high silver iodide structure having a high silver iodide content in the shell part can also be preferably used. In designing a photothermographic material having an image storability after development processing, in particular, a photothermographic material in which the fog increase due to light irradiation is extremely small, the higher the silver iodide content of the host tabular grains, the more preferable, and more preferably 90 mol% or more. 100 mol% or less.

3) Grain size The tabular grains in the present invention preferably have an average sphere equivalent diameter of 0.2 μm or more and 5.0 μm or less, and a sufficiently large grain size necessary to achieve high sensitivity can be selected. The average sphere equivalent diameter of silver halide is more preferably 0.3 μm or more and 3.0 μm or less. The equivalent sphere diameter here means the diameter of a sphere having the same volume as the volume of one silver halide grain.
As a measuring method, it can be obtained by measuring the equivalent circle diameter and thickness in the same manner as the above-described aspect ratio measurement. As the equivalent circle diameter is smaller and the thickness is thinner, the number of particles is increased and the inter-particle distribution of the epitaxial junction is usually increased. Therefore, the effect of the present invention becomes remarkably remarkable.

4) Epitaxial Junction The tabular silver halide grain in the invention preferably has an epitaxial junction. The epitaxial junction may be a double structure, a triple structure, or a higher order multiple structure. For example, at least a double structure composed of a core part and a shell part, preferably, the silver chloride content of the core part is 40 mol% or more, and the silver chloride content of the shell part is 30 mol% or less, More preferably, the core part is silver chloride and the shell part is silver bromide.

  The triple structure has a core part, an intermediate part, and a shell part, and preferably at least one of the core part and the intermediate part has a silver iodide content of 4 mol% or more. More preferably, the intermediate part has a silver iodide content of 10 mol% or more, more preferably the core part is silver chloride or silver bromide, the intermediate part is silver iodide, and the shell part is silver bromide, Preferably, the core part is silver chloride.

  In the present invention, the epitaxial junction can be formed on the apex, main surface or edge of the tabular grain, but is preferably the apex. The number of epitaxial junctions is at least 1, preferably 2 or more, more preferably 4 or more in tabular grains.

Tabular grains having an epitaxial junction in the present invention preferably have dislocation lines. Although dislocation lines may be unintentionally introduced into the epitaxial portion due to the difference in halogen composition between the host tabular grains and the epitaxial portion, it is more preferable that the dislocation line is introduced as intended by controlling the epitaxial deposition conditions. .
At this time, it is preferable that dislocation lines are not substantially observed in the host tabular grains. The coexistence of dislocation lines in the host tabular grains and the epitaxial part tends to be lowered in sensitivity due to a decrease in latent image formation efficiency.

  In the present invention, the size of the epitaxial portion is preferably 1 mol% to 60 mol%, more preferably 3 mol% to 50 mol% in terms of the number of moles of silver ions with respect to the host particle portion. More preferably, it is 5 mol%-30 mol%, Most preferably, it is 10 mol%-20 mol%.

5) Coating amount In general, in the case of a photothermographic material that remains as it is after heat development, increasing the silver halide coating amount decreases the transparency of the film and is undesirable in terms of image quality. It was limited to a low level. However, in the case of the present invention, the haze of the film caused by silver halide can be reduced by heat development treatment, so that more silver halide can be applied. In this invention, it is more preferable that they are 0.5 mol% or more and 100 mol% or less with respect to 1 mol of silver of a nonphotosensitive organic silver salt, Preferably they are 5 mol% or more and 50 mol% or less.

6) Heavy Metal The photosensitive silver halide grain in the invention is preferably doped with a different metal other than silver atoms. As the dissimilar metal other than the silver atom, a metal or metal complex of Group 6 to Group 13 of the periodic table (showing Groups 1 to 18) is preferable. More preferably, it is a Group 6 to Group 10 metal or metal complex. The central metal of the Group 6 to Group 10 metal or metal complex is preferably rhodium, ruthenium, iridium, or iron. 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 with ^respect to 1 mol of silver. These heavy metals and metal complexes and methods for 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. The hexacyano metal complexes 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⁻ , [Re (CN) ₆ ] ^{3− and the} like. . In the present invention, a hexacyano Fe complex is preferred.

  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, amides, etc.). 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 silver nitrate aqueous 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.

Further, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a silver halide emulsion desalting method and a chemical sensitization method that can be contained in the silver halide grains used in the present invention, JP-A-11-11 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.

7) Chemical sensitization The photosensitive silver halide used in the present invention may be non-chemically sensitized, but chemically sensitized by at least one of chalcogen sensitization, gold sensitization, and reduction sensitization. Is preferred. Examples of the chalcogen sensitizing method include a sulfur sensitizing method, a selenium sensitizing method, and a tellurium sensitizing method.
More preferably, the photosensitive silver halide used in the present invention is preferably chemically sensitized by a gold sensitizing method and a chalcogen sensitizing method.

In sulfur sensitization, unstable sulfur compounds are used. The unstable sulfur compounds described in Grafkides, Chimie et Physique Photographic (published by Paul Momtel, 1987, 5th edition), Research Disclosure, Vol. 307, No. 307105 can be used.
Specifically, thiosulfate (for example, hypo), thioureas (for example, diphenylthiourea, triethylthiourea, N-ethyl-N ′-(4-methyl-2-thiazolyl) thiourea, carboxymethyltrimethylthiourea), thioamides (Eg, thioacetamide), rhodanines (eg, diethyl rhodanine, 5-benzylidene-N-ethyl rhodanine), phosphine sulfides (eg, trimethylphosphine sulfide), thiohydantoins, 4-oxo-oxazolidin-2 Known sulfur compounds such as thiones, disulfides or polysulfides (for example, dimorpholine disulfide, cystine, lenthionine (1,2,3,5,6-pentathiepane)), polythionates, elemental sulfur, and active gelatin Also use You can. Particularly preferred are thiosulfates, thioureas and rhodanines.

  In selenium sensitization, unstable selenium compounds are used, and Japanese Patent Publication Nos. 43-13489, 44-15748, JP-A-4-25832, 4-109340, 4-271341, and 5-40324. 5-11385, JP-A-6-51415, JP-A-6-175258, JP-A-6-180478, JP-A-6-208186, JP-A-6-208184, JP-A-6-317867, JP-A-7-92599, Selenium compounds described in JP-A-7-98483 and JP-A-7-140579 can be used.

  Specifically, colloidal metal selenium, selenoureas (for example, N, N-dimethylselenourea, trifluoromethylcarbonyl-trimethylselenourea, acetyl-trimethylselenourea), selenoamides (for example, selenoamide, N, N -Diethylphenylselenamide), phosphine selenides (eg, triphenylphosphine selenide, pentafluorophenyl-triphenylphosphine selenide), selenophosphates (eg, tri-p-tolylselenophosphate, Tri-n-butylselenophosphate), selenoketones (for example, selenobenzophenone), isoselenocyanates, selenocarboxylic acids, selenoesters, diacylselenides and the like may be used. Furthermore, non-labile selenium compounds described in JP-B Nos. 46-4553 and 52-34492, such as selenite, selenocyanate, selenazoles, and selenides can also be used. In particular, phosphine selenides, selenoureas and selenocyanates are preferred.

  In tellurium sensitization, an unstable tellurium compound is used, and JP-A-4-224595, JP-A-4-271341, JP-A-4-3333043, JP-A-5-303157, JP-A-6-27573, JP-A-6-175258, The unstable tellurium described in JP-A-6-180478, JP-A-6-208186, JP-A-6-208184, JP-A-6-317867, JP-A-7-140579, JP-A-7-301879, JP-A-7-301880, etc. Compounds can be used.

  Specifically, phosphine tellurides (for example, butyl-diisopropylphosphine telluride, tributylphosphine telluride, tributoxyphosphine telluride, ethoxy-diphenylphosphine telluride), diacyl (di) tellurides ( For example, bis (diphenylcarbamoyl) ditelluride, bis (N-phenyl-N-methylcarbamoyl) ditelluride, bis (N-phenyl-N-methylcarbamoyl) telluride, bis (N-phenyl-N-benzylcarbamoyl) telluride, bis ( Ethoxycarbonyl) telluride), telluroureas (for example, N, N′-dimethylethylenetellurourea, N, N′-diphenylethylenetellurourea) telluramides, telluroesters, etc. may be used. In particular, diacyl (di) tellurides and phosphine tellurides are preferable. Particularly, the compounds described in the literature described in paragraph No. 0030 of JP-A-11-65021, the general formula (II) in JP-A-5-313284, Compounds represented by (III) and (IV) are more preferred.

  In particular, in the chalcogen sensitization in the present invention, selenium sensitization and tellurium sensitization are preferable, and tellurium sensitization is particularly preferable.

In gold sensitization, P.I. Gold sensitizers described in Grafkides, Chimie et Physique Photographic (published by Paul Momtel, 1987, 5th edition), Research Disclosure, Vol. 307, No. 307105 can be used. Specifically, chloroauric acid, potassium chloroaurate, potassium aurithiocyanate, gold sulfide, gold selenide and the like, in addition to these, U.S. Pat. Nos. 2,642,361, 5,049,484, 5,049,485, 5,169,751, Gold compounds described in Japanese Patent No. 5252455 and Belgian Patent No. 691857 can also be used.
P. Other than gold described in Grafkides, Chimie et Physique Photographic (published by Paul Momtel, 1987, 5th edition), Research Disclosure, 307, 307105, platinum, palladium, iridium, etc. You can also.

  Although gold sensitization can be used alone, it is preferably used in combination with the chalcogen sensitization described above. Specifically, gold sulfur sensitization, gold selenium sensitization, gold tellurium sensitization, gold sulfur selenium sensitization, gold sulfur tellurium sensitization, gold selenium tellurium sensitization, and gold sulfur selenium tellurium sensitization.

  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 chalcogen sensitizer used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but is 10 ⁻⁸ mol or more and 10 ⁻¹ mol or less, preferably 10 ⁻ per mol of silver halide. ^{About 7 to} 10 ⁻² mol is used.
Similarly, the amount of the gold sensitizer used in the present invention varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol or more and 10 ⁻² mol or less, more preferably 10 ⁻⁶ mol per mol of silver halide. The amount is 5 × 10 ⁻³ mol or less. The environmental conditions for chemically sensitizing this emulsion can be selected under any conditions, but the pAg is 8 or less, preferably 7.0 or less to 6.5 or less, particularly 6.0 or less, and the pAg is 1.5 or less. Above, preferably 2.0 or more, particularly preferably 2.5 or more, pH 3 to 10, preferably 4 to 9, temperature 20 to 95 ° C., preferably 25 to 80 It is about ℃ or less.

In the present invention, reduction sensitization can be used in combination with chalcogen sensitization or gold sensitization. In particular, it is preferably used in combination with chalcogen sensitization.
As specific compounds for the reduction sensitization, ascorbic acid, thiourea dioxide, and dimethylamine borane are preferable. In addition, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds, etc. It is preferable to use it. 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 also preferable by ripening while maintaining the pH of the emulsion at 8 or higher or pAg at 4 or lower, and reduction sensitization by introducing a single addition portion of silver ions during grain formation. Is also preferable.
The amount of reduction sensitizer added varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol or more and 10 ⁻¹ mol or less, more preferably 10 ⁻⁶ mol or more and 5 × 10 5 mol per mol of silver halide. ^-2 mol or less.

A thiosulfonic acid compound may be added to the silver halide emulsion used in the present invention by the method shown in European Patent Publication No. 293,917.
The photosensitive silver halide grains in the invention are preferably chemically sensitized by at least one of gold sensitization and chalcogen sensitization from the viewpoint of designing a high-sensitivity photothermographic material.

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

The one-electron oxidant formed by one-electron oxidation contained in the silver halide photographic light-sensitive material of the present invention is a compound selected from the following types 1 and 2 as the compound capable of emitting one electron or more. It is.
(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: 28-) is a compound that is a type 1 compound, and a one-electron oxidant produced by one-electron oxidation can further emit one electron with a 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 to 36), JP2001-500996 (Specific examples: Compounds 1-74, 80-87, 92-122), US Pat. No. 5,747,235, US Pat. No. 5,747,236, European Patent 786692A1 (Specific examples: Compounds INV 1-35), "One-photon two-electron sensitizer" or "deprotonated electron" described in patents such as European Patent No. 893732A1, US Pat. No. 6,054,260, US Pat. No. 5,994,051 Compound called Azukazo sensitizers "it can be mentioned. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

  Further, as a compound of type 1 that can be emitted by one-electron oxidant formed by one-electron oxidation and further undergoing bond cleavage reaction, one or more electrons can be emitted from 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) (JP-A-2003-114487) 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), and 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). In the general formula (2)), the general formula (8) (Synonymous with the general formula (1) described in Japanese Patent Application No. 2003-25886), or the reaction represented by the chemical reaction formula (1) (synonymous with the chemical reaction formula (1) described in Japanese Patent Application No. 2003-33446). Among the compounds that can cause the above, there can be mentioned a compound represented by the general formula (9) (synonymous with the general formula (3) described in Japanese Patent Application No. 2003-33446). The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the general formulas (1) and (2), RED ₁ and RED ₂ represent a reducing group. R ₁ is a non-metallic atomic group capable of forming a cyclic structure corresponding to a tetrahydro form of a 5- or 6-membered aromatic ring (including an aromatic heterocycle) or a hexahydro form together with carbon atom (C) and RED _1. To express. R ₂ , R ₃ and R ₄ represent a hydrogen atom or a substituent. Lv ₁ and Lv ₂ represent a leaving group. ED represents an electron donating group.

In the general formulas (3), (4) and (5), Z ₁ represents an atomic group capable of forming a 6-membered ring together with the nitrogen atom and the two carbon atoms of the benzene ring. _{R 5, R 6, R 7} , R 9, R 10, R 11, R 13, R 14, R 15, R 16, R 17, R 18, R 19 represents a hydrogen atom or a substituent. R ₂₀ represents a hydrogen atom or a substituent. When R ₂₀ represents a group other than an aryl group, R ₁₆ and R ₁₇ are bonded to each other to form an aromatic ring or an aromatic heterocycle. R ₈ and R ₁₂ represent a substituent that can be substituted on the benzene ring, m1 represents an integer of 0 to 3, and m2 represents an integer of 0 to 4. Lv ₃ , Lv ₄ and Lv ₅ represent a leaving group.

In general formulas (6) and (7), RED ₃ and RED ₄ represent a reducing group. R _{21 to} R ₃₀ represent a hydrogen atom or a substituent. Z ₂ represents —CR ₁₁₁ R ₁₁₂ —, —NR ₁₁₃ —, or —O—. R ₁₁₁ and R ₁₁₂ each independently represents a hydrogen atom or a substituent. _R113 represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

In the general formula (8), RED ₅ is a reducing group and represents an arylamino group or a heterocyclic amino group. R ₃₁ represents a hydrogen atom or a substituent. X 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. Lv ₆ is a leaving group and represents a carboxy group or a salt thereof or a hydrogen atom.

The compound represented by the general formula (9) is a compound that undergoes a bond formation reaction represented by the chemical reaction formula (1) by further oxidation after two-electron oxidation accompanied by decarboxylation. In the chemical reaction formula (1), R ₃₂ and R ₃₃ represent a hydrogen atom or a substituent. Z ₃ represents a group which forms a 5-membered or 6-membered heterocycle with C═C. Z ₄ 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. In the general formula (9), R ₃₂ , R ₃₃ and Z ₃ have the same meaning as in the chemical reaction formula (1). Z ₅ represents a group which forms a 5- or 6-membered cyclic aliphatic hydrocarbon group or heterocyclic group together with C—C.

Next, the type 2 compound will be described.
As a compound in which a one-electron oxidant produced by one-electron oxidation with a type 2 compound can further emit one or more electrons with a subsequent bond formation reaction, a compound represented by the 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 Japanese Patent Application No. 2003-33446). And a compound represented by the general formula (11) (synonymous with the general formula (2) described in Japanese Patent Application No. 2003-33446). The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the general formula (10), RED ₆ represents a reducing group that is one-electron oxidized. Y reacts with a one-electron oxidant formed by one-electron oxidation of RED ₆ to form a new bond, a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site, or Reactive group containing a non-aromatic heterocyclic moiety of a benzo-fused ring. Q represents a linking group linking RED ₆ and Y.

The compound represented by the general formula (11) is a compound that causes a bond formation reaction represented by the chemical reaction formula (1) by being oxidized. In the chemical reaction formula (1), R ₃₂ and R ₃₃ represent a hydrogen atom or a substituent. Z ₃ represents a group which forms a 5-membered or 6-membered heterocycle with C═C. Z ₄ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. Z ₅ represents a group which forms a 5- or 6-membered cyclic aliphatic hydrocarbon group or heterocyclic group together with C—C. M represents a radical, a radical cation, or a cation. In the general formula (11), R ₃₂ , R ₃₃ , Z ₃ and Z ₄ have the same meanings as those in the chemical reaction formula (1).

  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 are 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, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group, etc.) or imino silver (> NAg) And a nitrogen-containing heterocyclic group having a —NH— group as a heterocyclic partial structure (for example, a benzotriazole group, a benzimidazole group, an indazole group, etc.). 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 -A 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 (trialkylphosphonio group, dialkylaryl (or heteroaryl) phosphonio group, alkyldiaryl (or heteroaryl) phosphonio group, triaryl (or heteroaryl) phosphonio group, etc.). Can be 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. It is done. When a group having a negative charge in the 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 type 1 or 2 having a quaternary salt structure of nitrogen or phosphorus as the adsorptive group is represented by the general formula (X).

In 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) — each independently 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 coating, 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.

  Examples of type 1 and type 2 compounds in the present invention are shown below, but the present invention is not limited thereto.

9) Adsorbing redox compound having an adsorbing group and a reducing group In the present invention, it is preferable to contain an adsorbing redox compound having an adsorbing group and a reducing group for silver halide in the molecule. The adsorptive redox compound is preferably a compound represented by the following formula (AF-I).

Formula (AF-I) A- (W) n-B
In the formula (AF-I), A represents a group that can be adsorbed 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 reduction. Represents a group.

  In the formula (AF-I), the adsorptive group represented by A is a group that directly adsorbs to silver halide, or a group that promotes adsorption to silver halide. Specifically, a mercapto group (or its group) Salt), a thione group (—C (═S) —), a nitrogen atom, a sulfur atom, a heterocyclic group containing at least one atom selected from a selenium atom and a tellurium atom, a sulfide group, a disulfide group, a cationic group, or An ethynyl group etc. are mentioned.

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 ⁺ , Zn ^2+, etc.), ammonium ion Examples thereof include a heterocyclic group containing a quaternized nitrogen atom, a phosphonium ion, and the like.
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 “—S—” group, a “—Se—” group, a “—Te—” group, or a “═N—” group that can be coordinated to a silver ion by a coordination bond. A heterocyclic group having a partial structure of benzotriazole group, triazole group, indazole group, pyrazole group, tetrazole group, benzimidazole group, imidazole group, purine group, etc. , Thiazole group, oxazole group, benzothiophene group, benzothiazole group, benzoxazole group, thiadiazole group, oxadiazole group, tri Jin group, seleno azole 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 adsorbing 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 (AF-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, 2,5-dimercapto-1,3-thiazole group, etc.) Or a nitrogen-containing heterocyclic group having a —NH— group that can form imino silver (> NAg) as a partial structure of the heterocyclic ring (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 the formula (AF-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 (for example, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, etc.), an alkenylene group having 2 to 20 carbon atoms, and an alkynylene group having 2 to 20 carbon atoms. , An 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, and the like. It is done. 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 the formula (AF-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, hydroxyl group Amines, hydroxamic acids, hydroxyureas, hydroxyurethanes, hydroxysemicarbazides, reductones (including reductone derivatives), anilines, phenols (chroman-6-ols, 2,3-dihydrobenzofuran-5-ol , Aminophenols, sulfonamidophenols, hydroquinones, catechols, resorcinols, benzenetriols, polyphenols such as bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. Remove one hydrogen atom Residues, and the like. Of course, these may have an arbitrary substituent.

In the formula (AF-I), the reducing group represented by B shows its oxidation potential according to Akira Fujishima's “Electrochemical Measurement Method” (pages 150-208, published by Gihodo Publishing Co., Ltd) It can be measured using the measurement method described in the 4th edition (Vol. 9, pages 282-344, Maruzen). For example, by rotating disk voltammetry, specifically, a sample is dissolved in a solution of methanol: pH 6.5, Briton-Robinson buffer (Britton-Robinson buffer) = 10%: 90% (volume%), and nitrogen is added for 10 minutes. After aeration of gas, a rotating disc electrode (RDE) made of glassy carbon 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. It can be measured at the 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 (AF-I), the reducing group represented by B is preferably hydroxylamines, hydroxamic acids, hydroxyureas, hydroxysemicarbazides, reductones, phenols, acylhydrazines, carbamoylhydrazines, 3-pyrazolidone It is a residue obtained by removing one hydrogen atom from a class.

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

  Although the compound of the formula (AF-I) in this invention is illustrated below, this invention is not limited to these.

  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 (AF-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 (AF-I) in the present invention is preferably added to the silver halide image forming layer, and more preferably added during 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 desalting process start, 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 add 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 the 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 (AF-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.

10) Compound that effectively reduces visible light absorption derived from photosensitive silver halide after heat development In the present invention, visible light absorption derived from photosensitive silver halide is performed after heat development compared to before heat development. It is preferable to contain a compound that reduces the amount of the chemical.
In the present invention, it is particularly preferable to use a silver iodide complex-forming agent as a compound that practically reduces visible light absorption derived from photosensitive silver halide after heat development.

<Silver iodide complex forming agent>
The silver iodide complex-forming agent can contribute to a Lewis acid-base reaction in which at least one of a nitrogen atom or a sulfur atom in a compound donates electrons to a silver ion as a coordination atom (electron donor: Lewis base). is there. The stability of the complex is defined by a sequential stability constant or a total stability constant, but depends on the combination of silver ion, iodide ion, and the silver complexing agent. As a general guideline, a large stability constant can be obtained by means such as a chelate effect due to intramolecular chelate ring formation and an increase in the acid-base dissociation constant of the ligand.

  The ultraviolet-visible absorption spectrum of the photosensitive silver halide can be measured by a transmission method or a reflection method. If the absorption derived from other compounds added to the photothermographic material overlaps with the absorption of the photosensitive silver halide, the difference spectrum or the removal of other compounds with a solvent can be used alone or in combination. The UV-visible absorption spectrum of photosensitive silver halide can be observed.

The silver iodide complex-forming agent in the present invention is preferably a 5-membered to 7-membered heterocyclic compound containing at least one nitrogen atom. When the compound does not have a mercapto group, sulfide group or thione group as a substituent, the nitrogen-containing 5-membered to 7-membered heterocyclic ring may be saturated or unsaturated, and has other substituents. You may do it. Moreover, the substituents on the heterocycle may be bonded to each other to form a ring.
Examples of preferred 5- to 7-membered heterocyclic compounds include pyrrole, pyridine, oxazole, isoxazole, thiazole, isothiazole, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, indole, isoindole, indolizine, quinoline, isoquinoline, Benzimidazole, 1H-imidazole, quinoxaline, quinazoline, cinnoline, phthalazine, naphthyridine, purine, pteridine, carbazole, acridine, phenanthridine, phenanthroline, phenazine, phenoxazine, phenothiazine, benzothiazole, benzoxazole, benzimidazole, 1,2 , 4-triazine, 1,3,5-triazine, pyrrolidine, imidazolidine, pyrazolidine, piperidine, piperazine, morpholine, i Dorin, and the like isoindoline. More preferably pyridine, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, indole, isoindole, indolizine, quinoline, isoquinoline, benzimidazole, 1H-imidazole, quinoxaline, quinazoline, cinnoline, phthalazine, 1,8-naphthyridine, 1, Examples thereof include 10-phenanthroline, benzimidazole, benzotriazole, 1,2,4-triazine, 1,3,5-triazine and the like. Particularly preferred are pyridine, imidazole, pyrazine, pyrimidine, pyridazine, phthalazine, triazine, 1,8-naphthyridine, 1,10-phenanthroline and the like.

These rings may have a substituent, and the substituent may be any substituent as long as it does not adversely affect photographic properties. Preferred examples include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group (a linear, branched, or cyclic alkyl group, including a bicycloalkyl group or an active methine group), an alkenyl group, or an alkynyl group. Group, aryl group, heterocyclic group (regarding the position of substitution), acyl group, alkoxycarbonyl group, aryloxycarbonyl group, heterocyclic oxycarbonyl group, carbamoyl group, N-acylcarbamoyl group, N-sulfonylcarbamoyl group, N-carbamoylcarbamoyl group, N-sulfamoylcarbamoyl group, carbazoyl group, carboxy group or a salt thereof, oxalyl group, oxamoyl group, cyano group, carbonimidoyl group (Carbonidoyl group), formyl group, hydroxy group, alkoxy group ( Ethyleneoxy group Or an aryloxy group, heterocyclic oxy group, acyloxy group, (alkoxy or aryloxy) carbonyloxy group, carbamoyloxy group, sulfonyloxy group, amino group, (alkyl, Aryl, or heterocyclic) amino group, acylamino group, sulfonamide group, ureido group, thioureido group, imide group, (alkoxy or aryloxy) carbonylamino group, sulfamoylamino group, semicarbazide group, ammonio group, oxamoylamino Group, N- (alkyl or aryl) sulfonylureido group, N-acylureido group, N-acylsulfamoylamino group, nitro group, heterocyclic group containing a quaternized nitrogen atom (for example, pyridinio group, imidazolio group, Kinori O group, isoquinolinio group), isocyano group, imino group, (alkyl or aryl) sulfonyl group, (alkyl or aryl) sulfinyl group, sulfo group or a salt thereof, sulfamoyl group, N-acylsulfamoyl group, N-sulfonylsulfur group Examples include a famoyl group or a salt thereof, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, and a silyl group. Here, the active methine group means a methine group substituted with two electron-withdrawing groups, and the electron-withdrawing group here means an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, An alkylsulfonyl group, an arylsulfonyl group, a sulfamoyl group, a trifluoromethyl group, a cyano group, a nitro group, or a carbonimidoyl group (Carbonimidoyl group) is meant.
Here, the two electron withdrawing groups may be bonded to each other to form a cyclic structure. The salt means a cation such as alkali metal, alkaline earth metal or heavy metal, or an organic cation such as ammonium ion or phosphonium ion. These substituents may be further substituted with these substituents.
These heterocycles may be further condensed with other rings. Further, the substituent is an anionic group _{^{(e.g., -CO 2 -, -SO 3 -}} , -S - , etc.), the nitrogen-containing heterocyclic cation (e.g., pyridinium, etc. triazolium) and Thus, an inner salt may be formed.

When the heterocyclic compound is a pyridine, pyrazine, pyrimidine, pyridazine, phthalazine, triazine, naphthyridine or phenanthroline derivative, a tetrahydrofuran / water (3/2) mixed solution of the conjugate acid of the nitrogen-containing heterocyclic moiety in the acid dissociation equilibrium of the compound The acid dissociation constant (pKa) at 25 ° C. is more preferably 3 to 8. More preferably, the pKa is 4 to 7.
Such a heterocyclic compound is preferably a pyridine, pyridazine or phthalazine derivative, and particularly preferably a pyridine or phthalazine derivative.

  When these heterocyclic compounds have a mercapto group, sulfide group or thione group as a substituent, pyridine, thiazole, isothiazole, oxazole, isoxazole, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, triazine, triazole, thiadiazole or oxadioxide A diazole derivative is preferable, and a thiazole, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, triazine, or triazole derivative is particularly preferable.

  For example, a compound represented by the following general formula (1) or general formula (2) can be used as the silver iodide complex forming agent.

In Formula (1), R ¹¹ and R ¹² represents a hydrogen atom or a substituent. In general formula (2), R ²¹ and R ²² represents a hydrogen atom or a substituent. However, R ¹¹ and R ¹² are not both hydrogen atoms, and R ²¹ and R ²² are not both hydrogen atoms. Examples of the substituent herein include those described as the substituent of the nitrogen-containing 5-membered to 7-membered heterocyclic silver iodide complex forming agent.

  Moreover, the compound represented by the following general formula (3) can also be preferably used.

In the general formula (3), R ^{31 to} R ³⁵ each independently represent a hydrogen atom or a substituent. Examples of the substituent represented by R ³¹ -R ³⁵ include those described as the substituent of the nitrogen-containing 5-membered to 7-membered heterocyclic silver iodide complex forming agent. When the compound represented by the general formula (3) has a substituent, preferred substitution positions are R ^{32 to} R ³⁴ . R ^{31 to} R ³⁵ may be bonded to each other to form a saturated or unsaturated ring. Preferably, a halogen atom, an alkyl group, an aryl group, a carbamoyl group, a hydroxy group, an alkoxy group, an aryloxy group, a carbamoyloxy group, an amino group, an acylamino group, a ureido group, or an (alkoxy or aryloxy) carbonylamino group, etc. is there.

  The compound represented by the general formula (3) has an acid dissociation constant (pKa) at 25 ° C. of 3 to 8 in a tetrahydrofuran / water (3/2) mixed solution of a conjugate acid of a pyridine ring portion. It is preferably 4 to 7, and particularly preferably.

  Furthermore, the compound represented by General formula (4) is also preferable.

In the general formula (4), R ⁴¹ -R ⁴⁴ each independently represent a hydrogen atom or a substituent.
R ^{41 to} R ⁴⁴ may be bonded to each other to form a saturated or unsaturated ring. Examples of the substituent represented by R ⁴¹ -R ⁴⁴ include those described above as the substituent of the nitrogen-containing 5-membered to 7-membered heterocyclic silver iodide complex forming agent. Preferred groups include alkyl groups, alkenyl groups, alkynyl groups, aryl groups, hydroxy groups, alkoxy groups, aryloxy groups, heterocyclic oxy groups, and the formation of phthalazine rings by benzo condensed rings. When a hydroxyl group is substituted on the carbon adjacent to the nitrogen atom of the compound represented by the general formula (4), an equilibrium exists with pyridazinone.

The compound represented by the general formula (4) more preferably forms a phthalazine ring represented by the following general formula (5), and the phthalazine ring further has at least one substituent. It is particularly preferable. Examples of R ⁵¹ -R ⁵⁶ in the general formula (5) include those described as substituents of the aforementioned nitrogen-containing 5-membered to 7-membered heterocyclic silver iodide complex forming agent. More preferable substituents include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a hydroxy group, an alkoxy group, and an aryloxy group.
An alkyl group, an alkenyl group, an aryl group, an alkoxy group, or an aryloxy group is preferable, and an alkyl group, an alkoxy group, or an aryloxy group is more preferable.

  A compound represented by the following general formula (6) is also a preferred form.

In the general formula (6), R ⁶¹ -R ⁶³ each independently represent a hydrogen atom or a substituent. Examples of the substituent represented by R ⁶² include those described as the substituent of the nitrogen-containing 5-membered to 7-membered heterocyclic silver iodide complex-forming agent.

  A compound represented by the following general formula (7) is preferably used.

In the general formula (7), R ⁷¹ -R ⁷² each independently represent a hydrogen atom or a substituent.
L represents a divalent linking group. n represents 0 or 1. Examples of the substituent represented by R ^{71 to} R ⁷² include an alkyl group (including a cycloalkyl group), an alkenyl group (including a cycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group, an acyl group, and aryloxycarbonyl. Examples include a group, an alkoxycarbonyl group, a carbamoyl group, an imide group, and a composite substituent containing these. The divalent linking group represented by L is preferably a linking group having a length of 1 to 6 atoms, more preferably 1 to 3 atoms, and may further have a substituent.

  One of the compounds preferably used is a compound represented by the general formula (8).

In the general formula (8), R ^{81 to} R ⁸⁴ each independently represents a hydrogen atom or a substituent. Examples of the substituent represented by R ^{81 to} R ⁸⁴ include an alkyl group (including a cycloalkyl group), an alkenyl group (including a cycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group, an acyl group, and an aryloxycarbonyl. Examples include a group, an alkoxycarbonyl group, a carbamoyl group, and an imide group.

  More preferable among the silver iodide complex-forming agents are compounds represented by the general formulas (3), (4), (5), (6) and (7), and the general formula (3), The compound represented by (5) is particularly preferred.

  Although the preferable example of the silver iodide complex formation agent in this invention is given to the following, this invention is not limited to these.

  The silver iodide complex-forming agent in the present invention may be a common compound with the color tone agent when it functions as a conventionally known color tone agent. The silver iodide complex-forming agent in the present invention can be used in combination with a toning agent. Two or more silver iodide complex forming agents may be used in combination.

  The silver iodide complex-forming agent in the present invention is preferably present in the film in a state separated from the photosensitive silver halide, such as being present in the film in a solid state. It is also preferable to add to the adjacent layer. It is preferable to adjust the melting point of the compound to an appropriate range so that the silver iodide complex-forming agent in the present invention melts when heated to the heat development temperature.

  In the present invention, the absorption intensity of the ultraviolet-visible absorption spectrum of the photosensitive silver halide after heat development is preferably 80% or less, more preferably 40% or less, compared with that before heat development. It is particularly preferable that

The silver iodide complex-forming agent in the present invention 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.

As the solid fine particle dispersion method, the silver iodide complex-forming powder in the present invention 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. And a method of producing a solid dispersion.
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 content of Zr 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).
The silver iodide complex-forming agent in the present invention is preferably used as a solid dispersion.

  The silver iodide complex-forming agent in the present invention is preferably used in the range of 1 mol% to 5000 mol%, more preferably in the range of 10 mol% to 1000 mol%, relative to the photosensitive silver halide. More preferably, it is the range of 50 mol% or more and 300 mol% or less.

11) Combination of a plurality of silver halides The photosensitive silver halide emulsion in the photothermographic material used in the invention may be only one kind, or two or more kinds (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. As techniques relating to these, there are JP-A-57-119341, 53-106125, 47-3929, 48-55730, 46-5187, 50-73627, 57-150841, and the like. 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. / 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. In addition, 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.

(Description of antifogging agent)
Antifogging agents, stabilizers and stabilizer precursors that can be used in the present invention are paragraph No. 0070 of JP-A No. 10-62899, European Patent Publication No. 0803764A, page 20, line 57 to page 21, line 7. And the compounds described in JP-A-9-281737 and JP-A-9-329864, and the compounds described in US Pat. No. 6,083,681 and European Patent 1048875.

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 in 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 the 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 are a halogen atom, a carbamoyl group and 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) -, - SO 2 N (R) - , more preferably -C ( ═O) —, —SO ₂ —, —C (═O) N (R) —, and 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 bis type, tris type, 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.

  Specific examples of the compound represented by formula (H) in 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. 5,346,737, US Pat. No. 5,466,537, JP-A-50-137126, 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 formula (H) in the present invention is preferably used in the range of 10 ⁻⁴ mol to 1 mol, more preferably 10 ⁻³ , per mol of the non-photosensitive silver salt in the image forming layer. It is preferable to use in the range of not less than 0.5 mol and not more than 0.5 mol, more preferably not less than 1 × 10 ⁻² mol and not more than 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 added layer is preferably added to the layer having the image forming layer, and more preferably added to the image forming layer. The azolium salt may be added at any step during the preparation of the coating solution, and 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 it is preferably 1 × 10 ⁻⁶ mol or more and 2 mol or less, and more preferably 1 × 10 ⁻³ mol or more and 0.5 mol or less per 1 mol of silver.

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used for the purpose of controlling development by suppressing or promoting development, improving spectral sensitization efficiency, and improving 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-2002-303954, 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) Combinations; phthalazines (phthalazine, phthalazine derivatives or metal salts; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine And 2,3-dihydrophthalazine); a combination of phthalazines and phthalic acids is preferable, and a combination of phthalazines and phthalic acids is particularly preferable. Among them, a particularly preferable combination is a combination of 6-isopropylphthalazine and phthalic acid or 4-methylphthalic acid.

3) Plasticizers and lubricants In the present invention, known plasticizers and lubricants can be used to improve film physical properties. In particular, it is preferable to use a lubricant such as liquid paraffin, long chain fatty acid, fatty acid amide, fatty acid ester, etc., in order to improve handling at the time of manufacture and scratch resistance at the time of heat development. In particular, liquid paraffin from which low-boiling components have been removed and fatty acid esters having a branched structure and having a molecular weight of 1000 or more are preferred.
Regarding the plasticizer and lubricant that can be used in the image forming layer and the non-photosensitive layer, JP-A No. 11-65021, paragraph No. 0117, JP-A No. 2000-5137, Japanese Patent Application No. 2003-8015, Japanese Patent Application No. 2003-8071, The compounds described in Japanese Patent Application No. 2003-132815 are preferred.

4) Dye and Pigment In the image forming layer of the present invention, various dyes and pigments (for example, CI Pigment Blue 60, C.I. 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.

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, the addition method and the addition amount thereof, paragraph No. 0118 of JP-A No. 11-65021, paragraph Nos. 0136 to 0193 of JP-A No. 11-223898, and formula (H) of JP-A No. 2000-284399. , Compounds of formulas (1) to (3), formulas (A) and (B), compounds of general formulas (III) to (V) described in JP-A 2000-347345 (specific compounds: The nucleation promoter is described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

The addition amount of the nucleating agent is preferably in the range of 10 ⁻⁵ mol to 1 mol, more preferably 10 ⁻⁴ mol to 5 × 10 ⁻¹ mol, relative to 1 mol of the organic silver salt.
The nucleating 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 emulsification and dispersion methods include oils such as dibutyl phthalate, tricresyl phosphate, dioctyl sebacate or tri (2-ethylhexyl) phosphate, and dissolution using an auxiliary solvent such as ethyl acetate or cyclohexanone, and dodecylbenzene. Examples thereof include a method of mechanically preparing an emulsified dispersion by adding a surfactant such as sodium sulfonate, oleoyl-N-methyl taurate, sodium di (2-ethylhexyl) sulfosuccinate. At this time, it is also preferable to add a polymer such as α-methylstyrene oligomer or poly (t-butylacrylamide) for the purpose of adjusting the viscosity and refractive index of the oil droplets.

In addition, as a solid fine particle dispersion method, a nucleating agent powder is dispersed in a suitable 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 ultrasonic waves to produce a solid dispersion. The method of doing 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 content of Zr 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 nucleating agent, which is preferably added as 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.

  Specific examples of the nucleating agent that can be used in the present invention are listed below, but the present invention is not limited thereto.

When a nucleating agent is used in the photothermographic material of the present 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), hexametalin An acid (salt) etc. can be mentioned. 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 the} photosensitive material) may be a desired amount according to the performance such as sensitivity and fogging, but is 0.1 mg / m ^2. It is preferably 500 mg / m ² or less, more preferably 0.5 mg / m ² or more and 100 mg / m ² or less.

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution in the invention is preferably from 30 ° C. to 65 ° C., more preferably from 35 ° C. to less than 60 ° C., and more preferably from 35 ° C. to 55 ° C. 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 image forming layer in the invention is composed of one or more layers on a support. In the case of a single layer, it consists of an organic silver salt, a photosensitive silver halide, a reducing agent and a binder, and optionally contains additional materials such as toning agents, coating aids and other auxiliary agents. In the case of two or more layers, the first image forming layer (usually a layer adjacent to the support) contains an organic silver salt and a light-sensitive silver halide, and some of the second image forming layer or both layers include Must contain other ingredients. The construction of a multicolor photosensitive photothermographic material may include a combination of these two layers for each color and all components in a single layer as described in US Pat. No. 4,708,928. May be included. In the case of multi-dye multicolor photosensitive photothermographic materials, each image forming layer is generally functional or non-functional between each image forming layer as described in US Pat. No. 4,460,681. By using a sex barrier layer, they are kept distinct from each other.
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.

  In addition, although a layer acting as an optical filter can be provided, it 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 in 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), or 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.

The total coating amount (including water-soluble polymer and latex polymer) of the surface protective layer (per layer) is preferably 0.3 g / m ² or more and 5.0 g / m ² or less as the coating amount (per 1 m ^{2 of the} support). .3g / m ² or more 2.0 g / m ² or less is more preferable.
In addition, it is preferable to use a lubricant such as liquid paraffin and aliphatic ester for the surface protective layer. The amount of the lubricant used is in the range of 1 mg / m ^{2 to} 200 mg / m ² , preferably 10 mg / m ^{2 to} 150 mg / m ² , more preferably 20 mg / m ^{2 to} 100 mg / m ^2. .

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 range, it is preferable that substantially no dye color remains after image formation, and a means for decoloring by the heat of heat development is used. In particular, it is preferable to add a thermally decolorable dye and a base precursor to the non-photosensitive layer to function as an antihalation layer. These techniques are described in JP-A-11-231457 and the like.

The amount of decoloring dye added is determined by the use of the dye. In general, an optical density (absorbance) when measured at a 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.

When the dye is decolored in this way, the optical density after heat development can be reduced to 0.1 or less. Two or more kinds of decoloring dyes may be used in combination in a heat decoloring type recording material or a photothermographic material. Similarly, 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 and the like.

3) Matting Agent In the present invention, it is preferable to add a matting agent for improving the transportability. The matting agent is described in paragraph Nos. 0126 to 0127 of JP-A No. 11-65021. The matting agent is preferably 1 mg / m ² or more and 400 mg / m ² or less, more preferably 5 mg / m ² or more and 300 mg / m ² or less when expressed in terms of the coating amount per 1 m ^{2 of the} photothermographic material.
In the present invention, the shape of the matting agent may be either a regular shape or an irregular shape, but is preferably a regular shape, and a spherical shape is preferably used.
The volume weighted average of the equivalent sphere diameters of the matting agent used on the image forming layer surface side is preferably from 0.3 μm to 10 μm, and more preferably from 0.5 μm to 7 μm. Further, the variation coefficient of the size distribution of the matting agent is preferably 5% or more and 80% or less, and more preferably 20% or more and 80% or less. Here, the coefficient of variation is a value represented by (standard deviation of particle size) / (average value of particle size) × 100. Further, two or more kinds of matting agents having different average particle sizes can be used as the matting agent on the image forming layer surface. In this case, the difference in particle size between the matting agent having the largest average particle size and the smallest matting agent is preferably 2 μm or more and 8 μm or less, and more preferably 2 μm or more and 6 μm or less.
The volume weighted average of the equivalent sphere diameters of the matting agent used for the back surface is preferably 1 μm or more and 15 μm or less, and more preferably 3 μm or more and 10 μm or less. The variation coefficient of the size distribution of the matting agent is preferably 3% or more and 50% or less, and more preferably 5% or more and 30% or less. Further, two or more kinds of matting agents having different average particle sizes can be used as the matting agent for the back surface. In that case, the difference in particle size between the matting agent having the largest average particle size and the smallest matting agent is preferably 2 μm or more and 14 μm or less, and more preferably 2 μm or more and 9 μm or less.

  The matting degree of the image forming layer surface may be any as long as no stardust failure occurs, but the Beck smoothness is preferably 30 seconds or more and 2000 seconds or less, particularly preferably 40 seconds or more and 1500 seconds or less. The Beck smoothness can be easily determined by Japanese Industrial Standard (JIS) P8119 “Smoothness test method using Beck tester for paper and paperboard” and TAPPI standard method T479.

  In the present invention, the matte degree of the back layer is preferably a Beck smoothness of 1200 seconds or less and 10 seconds or more, preferably 800 seconds or less and 20 seconds or more, and more preferably 500 seconds or less and 40 seconds or more.

  In the present invention, the matting agent is preferably contained in the outermost surface layer of the photothermographic material, the layer functioning as the outermost surface layer, or a layer close to the outer surface, and also contained in a layer acting as a so-called protective layer. It is preferred that

4) Polymer Latex The non-photosensitive layer of the photothermographic material of the invention preferably contains a polymer latex. For such polymer latex, “Synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki, published by Kobunshi Publishing (1978))”, “Application of synthetic latex (Takaaki Sugimura, Ikuo Kataoka, Junichi Suzuki, Keiji Kasahara, Takashi "Molecular Publications (1993))" and "Synthetic Latex Chemistry (Muroichi Muroi, published by High Polymers Publication (1970))", specifically methyl methacrylate (33.5% by mass) / Ethyl acrylate (50 wt%) / Methacrylic acid (16.5 wt%) copolymer latex, Methyl methacrylate (47.5 wt%) / Butadiene (47.5 wt%) / Itaconic acid (5 wt%) copolymer Latex, latex of ethyl acrylate / methacrylic acid copolymer, methyl methacrylate (58.9% by mass) / 2-ethyl A latex of xyl acrylate (25.4% by weight) / styrene (8.6% by weight) / 2-hydroxyethyl methacrylate (5.1% by weight) / acrylic acid (2.0% by weight) copolymer, methyl methacrylate (64. 0 mass%) / styrene (9.0 mass%) / butyl acrylate (20.0 mass%) / 2-hydroxyethyl methacrylate (5.0 mass%) / acrylic acid (2.0 mass%) copolymer latex, etc. Is mentioned. Furthermore, as a binder for the surface protective layer, a combination of polymer latex described in Japanese Patent Application No. 11-6872, the technique described in Paragraph Nos. 0021 to 0025 of Japanese Patent Application Laid-Open No. 2000-267226, and Japanese Patent Application No. 11-6872. The technology described in paragraph numbers 0027 to 0028 of the specification and the technology described in paragraph numbers 0023 to 0041 of JP 2000-19678 may be applied. The ratio of the polymer latex in the surface protective layer is preferably 10% by mass or more and 90% by mass or less, and particularly preferably 20% by mass or more and 80% by mass or less of the total binder.

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 for each layer such as the image forming layer, protective layer, and back layer in 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 vinylsulfone 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 Are described in paragraph No. 0135 of the same number, paragraph No. 0136 of the same number about the method of obtaining a color image, paragraph numbers 0061 to 0064 of JP-A No. 11-84573 and paragraph numbers 0049 to 0062 of JP-A No. 2001-83679 about the slip agent. ing.
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, 2003-057780, and 2003-149766. In particular, the fluorosurfactants described in JP-A-2003-057780 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 double as an undercoat layer or a surface protective layer, 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 are preferably 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%, and 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 in the present invention may be disposed at any layer position, but is preferably disposed in the vicinity of the undercoat layer or the undercoat layer of the support. Specific examples of the antistatic layer are disclosed in paragraph No. 0135 of JP-A No. 11-65021, JP-A Nos. 56-143430, 56-143431, 58-62646, No. 56-120519 and JP-A No. 11-84573. Paragraph Nos. 0040 to 0051, US Pat. No. 5,575,957, and JP-A-11-223898, paragraph Nos. 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 coated simultaneously 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 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 0.1 S ⁻¹ is preferably 400 mPa · s or more and 100,000 mPa · s or less, more preferably 500 mPa · s or more and 20,000 mPa · s or less. Further, at a shear rate of 1000 S ⁻¹ , 1 mPa · s to 200 mPa · s is preferable, and 5 mPa · s to 80 mPa · s is more preferable.

In the case of preparing the coating liquid, a known in-line mixer or implant mixer is preferably used when mixing two kinds of liquids. A preferable in-line mixer in 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 in the present invention is the method described in JP-A No. 2002-66431.
When applying the coating solution, 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. Preferred drying methods in the present invention are 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 in 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.

  The photothermographic material is preferably a mono-sheet type (a type capable of forming an image on the photothermographic material without using another sheet such as an image receiving material).

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, 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 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, 10-171603, 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, 2000-187298 2001-200414, 2001-234635, 2002-020699, 2001-275471, 2001-275461, 2000-313204, 2001-292844, 2000-324888, Examples include 2001-293864 and 2001-348546.

(Image forming method)
The photothermographic material of the present invention is preferably a double-sided type having image forming layers on both sides of a support.

The photothermographic material of the present invention can be preferably used in an image forming method for recording an X-ray image using a fluorescent intensifying screen.
The process of forming an image using these photothermographic materials comprises the following processes.
(I) A step of superposing the photothermographic material and a fluorescent intensifying screen to perform radiation image exposure and recording a latent image on the photothermographic material.
(Ii) A thermal development step of converting the latent image into a visible image by thermal development.

The photothermographic material used in the assembly of the present invention is an image obtained by performing stair exposure with X-rays, and the image obtained by heat development on orthogonal coordinates having the same optical axis (D) and exposure amount (log E) coordinate axis unit length. In the characteristic curve, the average gamma (γ) formed by the point of minimum density (Dmin) + density 0.1 and the point of minimum density (Dmin) + density 0.5 is 0.5 to 0.9, and Prepared to have a characteristic curve having an average gamma (γ) of 3.2 to 4.0 formed by a point of minimum density (Dmin) + density 1.2 and minimum density (Dmin) + density 1.6. It is preferable that
In the X-ray imaging system of the present invention, when a photothermographic material having such a characteristic curve is used, an X-ray image having excellent photographic characteristics such that the legs are extremely extended and the gamma is high in the medium density portion. Is obtained. Due to this photographic characteristic, the description of the low density region such as the mediastinum with a small amount of X-ray transmission and heart shadow is good, and the density becomes easy to see even in the image of the lung field with a large amount of X-ray transmission. In addition, there is an advantage that the contrast becomes good.

In the photothermographic material having the preferable characteristic curve as described above, for example, each of the image forming layers on both sides is composed of two or more silver halide emulsion layers (image forming layers) having different sensitivities. It can be easily manufactured by a simple method.
In particular, it is preferable to form an image forming layer using a high-sensitivity emulsion for the upper layer and an emulsion having low sensitivity and high photographic characteristics for the lower layer.
When such an image forming layer comprising two layers is used, the difference in sensitivity of the silver halide emulsions between the respective layers is 1.5 to 20 times, preferably 2 to 15 times.
The ratio of the amount of emulsion used to form each layer varies depending on the sensitivity difference and covering power of the emulsion used. In general, the larger the sensitivity difference, the lower the usage ratio of the emulsion on the high sensitivity side. For example, when the difference in sensitivity is double, the preferable ratio of each emulsion is 1:20 or more and 1:50 or less as a high-sensitivity emulsion and a low-sensitivity emulsion in terms of silver when the covering power is almost equal. It is adjusted to be a range value.

  The technique of crossover cut (double-sided photosensitive material) and antihalation (single-sided photosensitive material) is described in JP-A-2-68539, page 13, lower left column, line 1 to page 14, lower left column, line 9; Dyes or dyes and mordants can be used.

1) Fluorescent Intensifying Screen Next, the fluorescent intensifying screen of the present invention will be described. The fluorescent intensifying screen includes, as a basic structure, a support and a phosphor layer formed on one side thereof. The phosphor layer is a layer in which a phosphor is dispersed in a binder. In general, a transparent protective film is provided on the surface of the phosphor layer opposite to the support (the surface not facing the support), and the phosphor layer is chemically altered or Protects against physical shock.

In the X-ray fluorescent intensifying screen more preferably used in the present invention, 50% or more of emitted light has a wavelength of 350 nm or more and 420 nm or less. In particular, the phosphor is preferably a divalent Eu-activated phosphor, and more preferably a divalent Eu-activated barium halide phosphor. The emission wavelength region is preferably 360 nm to 420 nm, more preferably 370 nm to 420 nm. More preferably, the fluorescent screen has light emission of 70% or more, more preferably 85% or more in the same region.
The ratio of the emitted light is calculated by the following method. That is, the emission spectrum is measured with the emission wavelength on the horizontal axis at equal intervals with a true number and the number of emitted photons on the vertical axis. A value obtained by dividing the area of 350 nm to 420 nm on this chart by the area of the entire emission spectrum is defined as the ratio of light emitted at a wavelength of 350 nm to 420 nm. By having light emission at such a wavelength, high sensitivity can be achieved in combination with the photothermographic material of the present invention.

  In order to have most of the emitted light of the phosphor in such a wavelength range, it is preferable that the half width of the emitted light is narrow. The preferred half-value width is 1 nm to 70 nm, more preferably 5 nm to 50 nm, and still more preferably 10 nm to 40 nm.

  The phosphor to be used is not particularly limited as long as such light emission is obtained. However, in order to achieve high sensitivity, which is the object of the present invention, the phosphor may be an Eu-activated phosphor having a divalent Eu as the emission center. The preferred present invention is not limited to this.

BaFCl: Eu, BaFBr: Eu, BaFI: Eu and those modified in halogen composition, BaSO ₄ : Eu, SrFBr: Eu, SrFCl: Eu, SrFI: Eu, (Sr, Ba) Al ₂ Si ₂ O ₈ : Eu, SrB ₄ O ₇ F: Eu, SrMgP ₂ O ₇ : Eu, Sr ₃ (PO ₄ ) ₂ : Eu, Sr ₂ P ₂ O ₇ : Eu, and the like.

A more preferable phosphor is a divalent Eu-activated barium halide phosphor represented by the general formula MX ₁ X ₂ : Eu. Here, M contains Ba as a main component, but it is possible to preferably contain a small amount of other compounds such as Mg, Ca and Sr. X ₁ and X ₂ are halogen atoms, and can be arbitrarily selected from F, Cl, Br, and I. Here, X ₁ is preferably fluorine. X ₂ can be selected from Cl, Br, and I, and a mixture of some of these halogen compositions can also be preferably used. More preferably, X ₂ = Br. Eu is europium. Eu as the emission center is preferably contained at a ratio of 10 ^{−7 to} 0.1 with respect to Ba. More preferably, it is 10 ⁻⁴ or more and 0.05 or less. It is also preferable to mix a small amount of other compounds. Most preferred phosphors include BaFCl: Eu, BaFBr: Eu, and BaFBr _1-X I _X : Eu.

The fluorescent intensifying screen is preferably composed of a support, an undercoat layer on the support, a phosphor layer, and a surface protective layer.
The phosphor layer is prepared by dispersing the phosphor layer in an organic solvent solution containing the phosphor particles and a binder resin, and then dispersing the dispersion into a support (an undercoat layer such as a light reflection layer on the support). Can be formed by directly coating and drying on the subbing layer). Alternatively, after applying this dispersion on a separately prepared temporary support and drying to form a phosphor sheet, the phosphor sheet is peeled off from the temporary support and attached to the support using an adhesive. May be.

  There is no restriction | limiting in particular in the particle size of fluorescent substance particle, Usually, it is the range of about 1 micrometer-15 micrometers, Preferably it is the range of about 2 micrometers-10 micrometers. The volume filling rate of the phosphor particles in the phosphor layer is preferably higher, usually in the range of 60% to 85%, preferably in the range of 65 to 80%, particularly preferably in the range of 68% to 75%. It is a range. (The ratio of the phosphor particles in the phosphor layer is usually 80% by mass or more, preferably 90% by mass or more, and particularly preferably 95% by mass or more.) Binder resin used for forming the phosphor layer, organic Solvents and various additives that can optionally be used are described in various known documents. The thickness of the phosphor layer can be arbitrarily set according to the target sensitivity, but is preferably in the range of 70 μm to 150 μm for the front side screen and in the range of 80 μm to 400 μm for the back side screen. . The X-ray absorption rate of the phosphor layer is determined by the amount of phosphor particles applied.

The phosphor layer may be a single layer or may be composed of two or more layers. One to three layers are preferable, and one or two layers are more preferable. For example, layers composed of phosphor particles having a relatively narrow particle size distribution and different particle sizes may be laminated. In that case, the layer closer to the support may have a smaller particle size. In particular, it is preferable to apply phosphor particles having a large particle size to the surface protective layer side, and to apply phosphor particles having a small particle size to the support side, and those having a small particle size are 0.5 μm to 2.0 μm. The thing of a particle size has the preferable range of 10 micrometers-30 micrometers.
Further, phosphor layers having different particle diameters may be mixed to form a phosphor layer, or in Japanese Patent Publication No. 55-33560, page 3, left column, line 3 to page 4, left column, line 39. As described, the phosphor layer may have a structure in which the particle size distribution of the phosphor particles is inclined. Usually, the variation coefficient of the particle size distribution of the phosphor is in the range of 30% to 50%, but monodispersed phosphor particles having a variation coefficient of 30% or less can also be preferably used.

Efforts are made to produce a preferable sharpness by dyeing the phosphor layer with respect to the emission wavelength. However, a layer design with as little dyeing as possible is preferably used. The absorption length of the phosphor layer is preferably 100 μm or more, more preferably 1000 μm or more.
The scattering length is preferably designed to be 0.1 μm or more and 100 μm or less. More preferably, it is 1 μm or more and 100 μm or less. The scattering length and the absorption length can be calculated by a calculation formula based on the Kubelka-Munk theory described later.

  The support can be appropriately selected from various supports used for known fluorescent intensifying screens according to the purpose. For example, a polymer film containing a white pigment such as titanium dioxide or a polymer film containing a black pigment such as carbon black is preferably used. An undercoat layer such as a light reflecting layer containing a light reflecting material may be provided on the surface of the support (the surface on the side where the phosphor layer is provided). A light reflecting layer as described in JP-A-2001-124898 is also preferably used. In particular, the light reflecting layer made of yttrium oxide described in Patent Example 1 and the light reflecting layer described in Patent Example 4 are preferably used. As for a preferred light reflecting layer, the description of JP-A 23001-124898, from the third term on the 15th line on the right to the fourth term on the right on the 23rd line can be referred to.

  A surface protective layer is preferably provided on the surface of the phosphor layer. The light scattering length measured at the main emission wavelength of the phosphor is preferably in the range of 5 μm to 80 μm, more preferably in the range of 10 μm to 70 μm, and particularly preferably in the range of 10 μm to 60 μm. Here, the light scattering length represents an average distance in which light travels straight before being scattered once, and the shorter the scattering length, the higher the light scattering property. The light absorption length representing the mean free distance until light is absorbed is arbitrary, but from the viewpoint of screen sensitivity, it is preferable that the surface protective layer does not absorb because the desensitization is less. In order to make up for the lack of scattering, it is possible to provide a slight absorption. The absorption length is preferably 800 μm or more, particularly preferably 1200 μm or more. The light scattering length and the light absorption length can be calculated by a calculation formula based on the Kubelka-Munk theory using the measured values measured by the following method.

  First, three or more film samples having the same composition as the surface protective layer to be measured and having different layer thicknesses are prepared. Next, the thickness (μm) and diffuse transmittance (%) of each film sample are measured. The diffuse transmittance can be measured by a device in which an integrating sphere is attached to a normal spectrophotometer. In the measurement in the present invention, a 150φ integrating sphere (150-0901) is attached to a self-recording spectrophotometer (U-3210, manufactured by Hitachi, Ltd.). The measurement wavelength needs to match the peak wavelength of the main light emission of the phosphor of the target phosphor layer to which the surface protective layer is attached. Next, the measured value of the film thickness (μm) and diffuse transmittance (%) are introduced into the following formula (A) derived from Kubelka-Munk's theoretical formula. Formula (A) can be expressed, for example, from “Phosphor Handbook” (Edited by Phosphors Association, Ohm Co., Ltd., published in 1987), pages 403, formulas 5 · 1 · 12 to 5 · 1 · 15 and diffuse transmittance T (%) Can be easily derived under the boundary condition.

  Where T is the diffuse transmittance (%), d is the film thickness (μm), and α and β are defined by the following equations, respectively.

  T (diffusion transmittance:%) and d (film thickness: μm) measured for three or more films are respectively introduced into the above equation (A), and K and S satisfying the equation (A) are calculated. The scattering length (μm) is defined by 1 / S and the absorption length (μm) is defined by 1 / K.

  The surface protective layer preferably has a structure in which light scattering particles are dispersed and contained in a resin material. The light refractive index of the light-scattering particles is usually 1.6 or more, preferably 1.9 or more. The particle diameter of the light scattering particles is usually in the range of 0.1 μm to 1.0 μm. Examples of such light-scattering particles include aluminum oxide, magnesium oxide, zinc oxide, zinc sulfide, titanium oxide, niobium oxide, barium sulfate, lead carbonate, silicon oxide, polymethyl methacrylate, styrene, and melamine fine particles. Can be mentioned.

  The resin material used for forming the surface protective layer is not particularly limited, but polyethylene terephthalate, polyethylene naphthalate, polyamide, aramid, fluororesin, polyester, and the like can be preferably used. The surface protective layer is prepared by dispersing the light scattering particles in an organic solvent solution containing a resin material (binder resin), and then preparing the dispersion on the phosphor layer (or any auxiliary material). It can be formed by coating and drying directly (through the layer). Or you may attach the sheet | seat for protective layers formed separately on the fluorescent substance layer using an adhesive agent. The thickness of the surface protective layer is usually in the range of 2 μm to 12 μm, and preferably in the range of 3.5 μm to 10 μm.

  Further, for a preferred method for producing a fluorescent intensifying screen and materials used therefor, for example, JP-A-9-21899, page 6, left column, line 47 to page 8, left column, line 5, JP-A-6-347598. There are detailed descriptions on page 2, right column, line 17 to page 3, left column, line 33, and page 3, left column, line 42 to page 4, left column, line 22 of the publication. be able to.

  The fluorescent intensifying screen used in the present invention is preferably filled with a phosphor with an inclined particle size structure. In particular, it is preferable to apply phosphor particles having a large particle size to the surface protective layer side, and to apply phosphor particles having a small particle size to the support side, and those having a small particle size are 0.5 μm to 2.0 μm. The thing of a particle size has the preferable range of 10 micrometers-30 micrometers.

  As an image forming method using the photothermographic material of the present invention, a method of forming an image by combining with a phosphor having a main peak preferably at 400 nm or less can be used. More preferably, a method of forming an image in combination with a phosphor having a main peak at 380 nm or less is preferable. Either a double-sided sensitive material or a single-sided sensitive material can be used as an assembly. As the screen having a main emission peak at 400 nm or less, the screens described in JP-A-6-11804 and WO93 / 01521 are used, but not limited thereto. As a technique of ultraviolet crossover cut (double-sided photosensitive material) and antihalation (single-sided photosensitive material), the technique described in JP-A-8-76307 can be used. As the ultraviolet absorbing dye, the dye described in JP-A No. 2001-144030 is particularly preferable.

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. The preferred development temperature is 80 ° C to 250 ° C, more preferably 100 ° C to 140 ° C. The development time is preferably 1 second to 60 seconds, more preferably 5 seconds to 30 seconds, and particularly preferably 5 seconds to 20 seconds.

A plate heater method is preferred as the heat development method. The heat development method using the plate heater method is preferably the method described in JP-A-11-133572. The heat development photosensitive material having the latent image formed thereon is brought into contact with the heating means in the heat development section to obtain a visible image. In the developing device, 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 heat is interposed between the press roller and the plate heater. A thermal development apparatus that performs thermal development by passing a development photosensitive material. It is preferable to divide the plate heater into two to six stages and lower the temperature at the tip by about 1 ° C. to 10 ° C.
For the heat development of the double-sided photothermographic material, it is preferable to arrange a plurality of heating means facing back along the transport direction of the photothermographic material so that both sides can be heated.

  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 changes in the shape of the support of the photothermographic material due to heating of the photothermographic material.

(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 The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
1. 1. Production of PET support and undercoat 1-1. Film formation

  Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured at 25 ° C. in phenol / tetrachloroethane = 6/4 (mass ratio)) was obtained according to a conventional method. This was pelletized and dried at 130 ° C. for 4 hours. The film was colored blue with a blue dye (1,4-bis (2,6-diethylanilinoanthraquinone), then extruded from a T-die and quenched 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.

1-2. 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.

1-3. Preparation of undercoat support 1) Preparation formulation of undercoat layer coating solution (1) (for photosensitive layer side undercoat layer)
46.8 g of pesresin A520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Bailonal MD1200 10.4g, manufactured by Toyobo Co., Ltd.
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number: 8.5) 1% by mass solution 11.0 g
MP1000 (PMMA polymer fine particles, average particle size 0.4 μm) manufactured by Soken Chemical Co., Ltd.
0.91g
931 ml of distilled water

2) Undercoat After each of the two surfaces of the 175 μm-thick biaxially stretched polyethylene terephthalate support was subjected to the corona discharge treatment, the undercoat coating solution formulation (1) was coated with a wire bar at a wet coating amount of 6.6 ml / m. ² (per one side) was applied and dried at 180 ° C. for 5 minutes, and this was applied to both sides to prepare an undercoat support.

2. Preparation of coating materials 1) Preparation of photosensitive silver halide emulsion A-Preparation of host grains-
4.3 ml of 1% by weight potassium iodide solution is added to 1421 ml of distilled water, and 3.5 ml of 0.5 mol / L sulfuric acid, 36.5 g of phthalated gelatin, and 5 mass of 2,2 ′-(ethylenedithio) diethanol. The solution to which 160 ml of methanol solution was added was stirred in a stainless steel reaction vessel while maintaining the liquid temperature at 75 ° C., and 22.22 g of silver nitrate was added to distilled water and diluted to 218 ml. Solution B in which 6 g was diluted to 366 ml with distilled water was added in a total amount over 16 minutes at a constant flow rate, and solution B was added by the control double jet method while maintaining pAg at 10.2.
Thereafter, 10 ml of a 3.5% by mass aqueous hydrogen peroxide solution was added, and 10.8 ml of a 10% by mass aqueous solution of benzimidazole was further added. Further, a solution C in which distilled water was added to 51.86 g of silver nitrate and diluted to 508.2 ml, and a solution D in which 63.9 g of potassium iodide were diluted to 639 ml with distilled water, and solution C was added at a constant flow rate over 80 minutes. The entire amount was added, and Solution D was added by the control double jet method while maintaining pAg at 10.2.
The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so that it would be 1 × 10 ⁻⁴ mole per mole of silver. Further, 5 seconds after the completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver.
The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 11.0.
Thus, an unripe pure silver iodide emulsion was prepared.

  The obtained silver halide grains had an average projected area diameter of 0.93 μm, an average projected area diameter variation coefficient of 17.7%, an average thickness of 0.057 μm, and an average aspect ratio of 16.3 tabular grains having a total projected area. It accounted for over 80%. The equivalent sphere diameter was 0.42 μm. As a result of analysis by X-ray powder diffraction analysis, 30% or more of silver iodide was present in the γ phase.

-Preparation of epitaxial junction-
One mole of the unripe emulsion was placed in a reaction vessel. The pAg was 10.2 measured at 38 ° C. Then, by double jet addition, a 0.5 mol / L KBr solution and a 0.5 mol / L AgNO ₃ solution were added at 10 ml / min over 20 minutes to substantially add 10 mol% silver bromide to the AgI host. It was precipitated epitaxially on the particles. During operation, pAg was maintained at 10.2. Further, the pH was adjusted to 3.8 using sulfuric acid having a concentration of 0.5 mol / L, 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 11.0.

-Chemical sensitization-
The silver halide emulsion provided with the epitaxial junction was maintained at 38 ° C. while stirring, 5 ml of a methanol solution of 0.34% by mass of 1,2-benzisothiazolin-3-one was added, and after 47 minutes, 47 ° C. The temperature was raised to. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per 1 mol of silver, and 5 minutes later, tellurium sensitizer C was added in a methanol solution to a ratio of 2. 9 × 10 ⁻⁵ mol was added and aged for 91 minutes.
Thereafter, 1.3 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ and N ″ -diethylmelamine was added, and after another 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the silver solution with a methanol solution. 4.8 × 10 ⁻³ mole per mole, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in methanol solution with 5.4 × 10 ⁻³ mole per mole of silver and 1- (3-Methylureidophenyl) -5-mercaptotetrazole was added in an aqueous solution to 8.5 × 10 ⁻³ mol per mol of silver.

<Preparation of mixed emulsion for coating solution>
The above silver halide emulsion was dissolved, and 7 × 10 ⁻³ mol of benzothiazolium iodide was added as a 1% by mass aqueous solution per mol of silver. Further, the amount of the compound compounds 1, 2 and 3 that can be emitted by one-electron oxidation by one-electron oxidant to emit one or more electrons is 2 × 10 ⁻³ mol per mol of silver halide. Was added.
Further, compounds 1 and 2 having an adsorbing group and a reducing group were added in an amount of 8 × 10 ⁻³ mol per mol of silver halide.
Further, water was added so that the silver halide content per liter of the mixed emulsion for coating solution was 15.6 g as silver.

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 agitation, the total amount of the previous sodium behenate solution and the total amount of silver nitrate aqueous solution were kept at a constant flow rate of 93 minutes and 15 seconds, respectively. And added over 90 minutes.
At this time, only the silver nitrate aqueous solution is added for 11 minutes after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution is started. After the addition of the aqueous silver nitrate solution, only the sodium behenate solution is added for 14 minutes and 15 seconds. It was made to be.
At this time, the temperature in the reaction vessel was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant.
The pipe of the addition system for the sodium behenate solution was kept warm by circulating hot water outside the double pipe so that the liquid temperature at the outlet at the tip of the addition nozzle was 75 ° C. Moreover, the piping of the addition system of the silver nitrate aqueous solution was kept warm by circulating cold water outside the double pipe. The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically around the stirring axis, and were adjusted so as not to contact the reaction solution.

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

  When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average values were a = 0.21 μm, b = 0.4 μm, c = 0.4 μm, average aspect ratio 2.1, and equivalent sphere diameter. The crystal had a coefficient of variation of 11%. (A, b, and c are the text provisions)

  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 to make a total amount of 1000 kg, and then slurried with a dissolver blade, and a pipeline mixer (manufactured by Mizuho Kogyo Co., Ltd.). : PM-10 type).

Next, the pre-dispersed stock 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-1 dispersion>
10 masses of reducing agent-1 (1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane) 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, dispersed for 3 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 0. 2 g and water were added to prepare a reducing agent concentration of 25% by mass. This dispersion was heat-treated at 60 ° C. for 5 hours to obtain a reducing agent-1 dispersion.
The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.4 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 nucleating agent dispersion To nucleating agent SH-7 (10 g), 2.5 g of polyvinyl alcohol (PVA-217 manufactured by Kuraray Co., Ltd.) and 87.5 g of water were added and stirred well to obtain a slurry. Left for 3 hours.
Thereafter, 240 g of 0.5 mm zirconia beads are put in a vessel together with the slurry, and dispersed for 10 hours with a disperser (1/4 G sand grinder mill: manufactured by IMEX Co., Ltd.) to prepare a solid fine particle dispersion of a nucleating agent. did. As for the particle size, 80% by mass of the particles was 0.10 μm to 1.0 μm, and the average particle size was 0.5 μm.

5) Preparation of hydrogen bonding compound dispersion 10 kg of 10% by weight aqueous solution of hydrogen bonding compound-1 (tri (4-t-butylphenyl) phosphine oxide) 10 kg and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added 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 prepare a hydrogen bonding compound concentration of 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.

6) Preparation of development accelerator dispersion and color adjusting agent dispersion <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 to 10 kg of water 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 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.

<Solid Dispersion of Development Accelerator-2 and Color Toner-1>
The solid dispersions of the development accelerator-2 and the color tone modifier-1 were also dispersed by the same method as the development accelerator-1, and 20% by mass and 15% by mass of dispersions were obtained, respectively.

7) Preparation of polyhalogen compound dispersion <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. The slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to prepare an organic polyhalogen compound concentration of 30% 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.

<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 prepare an organic polyhalogen compound concentration of 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 silver iodide complex-forming agent 8 kg of modified polyvinyl alcohol MP203 was dissolved in 174.57 kg of water, then 3.15 kg of a 20% by weight aqueous solution of sodium triisopropylnaphthalenesulfonate and 70% by weight of 6-isopropylphthalazine. 14.28 kg of an aqueous solution was added to prepare a 5% by mass solution of a silver iodide complex forming compound.

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

<< Preparation of Mercapto Compound-2 Aqueous Solution >>
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 compounds of general formulas (I) to (III) of the present invention.
Compounds A to E were dissolved in methanol to prepare a 0.002M solution.

11) Preparation of binder latex liquid << Preparation of SBR latex liquid >>
SBR latex (TP-1) 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, 14.06 ml of NaOH, 0.15 g of ethylenediaminetetraacetic acid tetrasodium salt, 255 g of styrene, 11.25 g of acrylic acid, 3.0 g of tert-dodecyl mercaptan, 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 and the internal temperature was raised 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 the mixture was 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: 1 using 1 mol / L NaOH and NH ₄ OH. 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 with 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 (TP-1) 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 Toa Denki Kogyo Co., Ltd. conductivity meter CM-30S was used, latex stock solution (44% by mass) measured at 25 ° C), SBR latex with a different pH of 8.4 Tg, the ratio of styrene and butadiene was changed as appropriate. It can be prepared by the method.

<< Preparation of isoprene latex liquid >>
Isoprene latex (TP-2) was prepared as follows.
Add 1500g 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 stirrer 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 in which 5.22 g of acrylic acid was dissolved in 46.98 g of water was added, 10 g of water was subsequently added, and a solution in which 1.30 g of ammonium persulfate was dissolved in 50.7 ml of water was further added. 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 ⁺ ions: NH ₄ ⁺ ions were used with 1 mol / L NaOH and NH ₄ OH. = 1: 5.3 (molar ratio) was added and adjusted to pH 8.3. Thereafter, the mixture was filtered with a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored to obtain 1248 g of isoprene latex (TP-2). 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). Measurement was conducted at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.).

3. Preparation of coating solution 1) Preparation of image forming layer coating solutions-1 to 6 To 1000 g of the fatty acid silver dispersion obtained above, water, organic polyhalogen compound-1 dispersion, organic polyhalogen compound-2 dispersion, Dispersions of compounds of general formula (I) of the present invention (shown in Table 1), SBR latex (TP-1) liquid, isoprene latex (TP-2) liquid, reducing agent-1 dispersion, reducing agent-2 Dispersion, nucleating agent dispersion, hydrogen bonding compound-1 dispersion, development accelerator-1 dispersion, development accelerator-2 dispersion, color modifier-1 dispersion, mercapto compound-1 aqueous solution, and mercapto Compound-2 aqueous solution was added sequentially, and after the silver iodide complex forming agent was added, 0.22 mol of the mixed emulsion for coating solution was added in silver amount per mol of fatty acid silver immediately before coating, mixed well, and left as it was. The solution was fed to the coating die.

2) Preparation of intermediate layer coating solution A 1000 g of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), 163 g of pigment-1 dispersion, blue dye compound (manufactured by Nippon Kayaku Co., Ltd .: Kayafect Turquoise RN Liquid 150) 18 33 g of a 5% by weight aqueous solution, 27 ml of a 5% by weight aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28 / 5/2) 27% 5% aqueous solution of aerosol OT (manufactured by American Cyanamid Co., Ltd.) in 4200 ml of 19% by weight latex, 135 ml of 20% by weight aqueous solution of diammonium phthalate, total amount 10000g Add water and NaOH to pH 7.5 The intermediate layer coating solution was adjusted to 8.9 ml / m ² and fed to the coating die.
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 840 ml of water, and methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio) 57/8/28/5/2) Latex 19% by weight solution 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. The mixture was mixed, and immediately before coating, 40 ml of 4% by weight chromium alum was mixed with a static mixer and fed to the coating die so that the amount of the coating solution was 26.1 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, 10 g of 10% by weight emulsion of liquid paraffin, 10% by weight of dipentaerythritol hexaisostearate 30 g of emulsion, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer "quantity ratio 57/8/28/5/2" latex 19% by weight liquid 180 g, phthalic acid 15 mass 40 ml of methanol solution, 5.5 ml of 1% by weight solution of fluorosurfactant (F-1), 5.5 ml of 1% by weight aqueous solution of fluorosurfactant (F-2), disulfosuccinate (2 -28 ml of a 5% by weight aqueous solution of -ethylhexyl) sodium salt, polymethyl methacrylate fine particles (flat A mixture of 4 g of average particle size 0.7 μm, volume weighted average distribution 30%) and 21 g of polymethyl methacrylate fine particles (average particle size 3.6 μm, volume weighted average distribution 60%) is used as a surface protective layer coating solution, The solution was fed to the coating die so as to be 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).

4). Production of photothermographic material 1) Production of photothermographic material-101 From the undercoat surface, a slide bead is applied in the order of a crossover cut layer, an image forming layer, an intermediate layer, a surface protective layer first layer, and a surface protective layer second layer. Samples of the photothermographic material were prepared by simultaneous multi-layer coating by the method.
At this time, the image forming layer and the intermediate layer were adjusted to 31 ° C., the first surface protective layer was adjusted to 36 ° C., and the second surface protective layer was adjusted to 37 ° C. The amount of silver applied to the image forming layer was 0.862 g / m ² per side in total for the fatty acid silver and the silver halide. This was applied to both sides of the support.

The total coating amount (g / m ² ) per side of each compound in the image forming layer is as follows.
Fatty acid silver 2.85
Polyhalogen compound-1 0.028
Polyhalogen compound-2 0.094
Dispersions of compounds of general formula (I) according to the invention (described in Table 1)
Silver iodide complex forming agent 0.46
SBR latex 2.08
Isoprene Latex 3.12
Reducing agent-1 0.46
Nucleator-1 0.036
Hydrogen bonding compound-1 0.15
Development accelerator-1 0.005
Development accelerator-2 0.035
Color tone adjusting agent-1 0.002
Mercapto Compound-1 0.001
Mercapto compound-2 0.003
Silver halide (as Ag) 0.175

The coating and drying conditions are as follows.
The support was neutralized with ion wind before coating, and coating was performed at a speed of 160 m / min. The coating and drying conditions were adjusted within the following ranges for each sample, and were set to conditions that would provide the most stable surface shape.
The gap between the coating die tip and the support is 0.10 mm to 0.30 mm.
The pressure in the decompression chamber is set to 196 Pa to 882 Pa lower than the atmospheric pressure.
In the subsequent chilling zone, the coating solution is cooled with wind at a dry bulb temperature of 10 ° C to 20 ° C.
It is transported in a non-contact manner and dried with a dry air having a dry bulb temperature of 23 ° C. to 45 ° C. and a wet bulb temperature of 15 ° C. to 21 ° C. in a helical contact type non-contact dryer.
After drying, humidity is adjusted at 25 ° C. and humidity 40% RH-60% RH.
Subsequently, the film surface was heated to 70 ° C. to 90 ° C., and after the heating, the film surface was cooled to 25 ° C.

  The resulting photothermographic material had a matte degree of Beck smoothness of 550 seconds. Moreover, it was 6.0 when pH of the film surface was measured.

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

5. Evaluation of Performance 1) 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 in which PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% by mass of carbon is laminated:
Oxygen permeability: 0.02 ml / atm · m ² · 25 ° C · day,
Moisture permeability: 0.10 g / atm · m ² · 25 ° C · day.

2) Exposure and heat development The double-sided coated photosensitive material thus prepared was evaluated as follows.
An X-ray regular screen HI-SCREEN-B3 (CaWO ₄ is used as a phosphor, emission peak wavelength 425 m) manufactured by Fuji Film Co., Ltd. is used, and a sample is sandwiched between them to produce an image forming assembly. did.
This assembly was subjected to X-ray exposure for 0.05 seconds, and X-ray sensitometry was performed. The X-ray apparatus used was a trade name DRX-3724HD manufactured by Toshiba Corporation, and a tungsten target was used. A voltage of 80 kVp was applied with a three-phase full-wave rectification type pulse generator, and X-rays passed through a 7 cm water filter having absorption almost equivalent to that of the human body were used as a light source. The X-ray exposure was changed by the distance method, and step exposure was performed with a width of logE = 0.15. After the exposure, heat development was performed under the following heat development conditions. The obtained image was evaluated with a densitometer.

  The heat development section of the Fuji Medical Dry Laser Imager FM-DPL was modified to produce a heat development machine that can be heated from both sides. In addition, the film was remodeled so that the film sheet could be conveyed by changing the conveyance roller of the heat developing unit to a heat drum. Four panel heaters were set to 112 ° C-118 ° C-120 ° C-120 ° C, and the temperature of the heat drum was set to 120 ° C. The conveyance speed was adjusted so that the total heat development time was 24 seconds.

3) Evaluation items (photo performance)
The obtained image was subjected to density measurement with a Macbeth densitometer to produce a density characteristic curve with respect to the logarithm of the exposure amount.
Fog: The density of the non-image area was measured with a Macbeth densitometer.
Sensitivity: Sensitivity is represented by the reciprocal of the exposure amount giving a blackening density of fog + 1.0. The sensitivity of 1 is taken as 100, and the relative value is shown. A larger value indicates higher sensitivity.
Gradation (γ): a gradient of a straight line connecting a point of minimum density (Dmin) + density 1.2 and a point of minimum density (Dmin) + density 1.6.

(Image preservation)
The heat-developed sample was left in an environment of 25 ° C., 60% RH, and 500 LUX under a fluorescent lamp for 20 days. Image storability was evaluated by the difference in fog (ΔDmin) immediately after heat development and after standing. The smaller the increase in fog, the better.
ΔDmin = Dmin (after standing) −Dmin (immediately after heat development)

  The obtained results are shown in Table 1.

4) Results As shown in Table 1, the compound of the present invention suppressed fogging immediately after development and suppressed fogging during image storage. Among them, the compounds D and E represented by the general formula (III) showed a high improvement effect, and particularly the compound D showed a remarkable improvement effect.

Example 2
1. Preparation of silver halide emulsion B <Preparation of gold-sensitized AgI tabular emulsion>
The unchemically sensitized silver halide dispersion prepared in the same manner as in Example 1 was maintained at 45 ° C. with stirring, and sodium benzenethiosulfonate was added to a mole of silver with a methanol solution per mole of silver. 3.0 × 10 ⁻⁵ mol and sulfur sensitizer 4-oxo-3-benzyl-oxazolidine-2-thione was added in a methanol solution to 4.5 × 10 ⁻⁵ . After 5 minutes, 1.2 × 10 ⁻⁵ moles of chloroauric acid and 5.0 × 10 ⁻³ moles of potassium thiocyanate were added as aqueous solutions per mole of silver and aged for 60 minutes.
Thereafter, 0.7 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″, N ″ -diethylmelamine was added per 1 mol of silver, and further, 4-methyl-2-mercaptobenzimidazole was added after 4 minutes. 4.8 × 10 ⁻⁴ mol per mol of silver in a methanol solution, and 5.4 × 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole per mol of silver in a methanol solution. 10 ⁻⁴ mol and 1- (3-methylureidophenyl) -5-mercaptotetrazole were added in an aqueous solution to 8.5 × 10 ⁻⁴ mol per mol of silver.
A silver halide emulsion B was prepared in the same manner as in Example 1 except that the chemical sensitization was changed as described above.
2. Preparation of Coating Samples Samples 21 to 26 were prepared in the same manner as in Example 1 except that silver halide emulsion B was used in place of photosensitive silver halide emulsion A.

3. Performance Evaluation The results evaluated in the same manner as in Example 1 are shown in Table 2.
In the case of the gold-sulfur sensitized emulsion, the fog immediately after development was suppressed, and the fog during image storage was suppressed. Among them, the compounds D and E represented by the general formula (III) showed a high improvement effect, and especially the compound D showed a remarkable improvement effect as in Example 1. Furthermore, although a problem that the gradation is soft in the gold-sulfur sensitized emulsion has been found, it has been found that the compound of the present invention has an unexpected effect of making it harder than when not added. .

Example 3
In Example 2, the same experiment as in Example 2 was performed except that the following fluorescent intensifying screen A was used instead of the X-ray regular screen HI-SCREEN-B3.
As a result, the photothermographic material of the present invention showed good results as in Example 2.

(Preparation of fluorescent intensifying screen A)
1) Preparation of undercoat layer In the same manner as in Example 4 of Japanese Patent Application Laid-Open No. 2001-124898, a light reflecting layer having a dried film thickness of 50 μm formed of alumina powder is formed on a 250 μm polyethylene terephthalate (support). did.

2) Production of phosphor sheet BaFBr: Eu phosphor (average particle size 3.5 μm) 250 g, polyurethane binder resin (manufactured by Dainippon Ink and Chemicals, trade name: Pandex T5265M) 8 g, epoxy binder resin 2 g (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 1001) and 0.5 g of isocyanate compound (trade name: Coronate HX, produced by Nippon Polyurethane Industry Co., Ltd.) are added to methyl ethyl ketone and dispersed with a propeller mixer. A phosphor layer forming coating solution having a viscosity of 25 PS (25 ° C.) was prepared. This coating solution was applied to the surface of a temporary support (polyethylene terephthalate sheet previously coated with a silicone-based release agent) and dried to form a phosphor layer. The phosphor layer was peeled off from the temporary support to obtain a phosphor sheet.

3) Attaching the phosphor sheet on the light reflecting layer The above phosphor sheet is superimposed on the surface of the light reflecting layer of the support with the light reflecting layer produced in the above step 1), and the pressure is 400 kgw with a calender roll. A pressure was applied under the conditions of / cm ² and a temperature of 80 ° C. to provide a phosphor layer on the light reflection layer. The thickness of the obtained phosphor layer was 125 μm, and the volume filling factor of the phosphor particles in the phosphor layer was 68%.

4) Formation of surface protective layer A polyester adhesive was applied to one side of polyethylene terephthalate (PET) having a thickness of 6 μm, and a surface protective layer was provided on the phosphor layer by a laminating method. Thus, a fluorescent intensifying screen A comprising a support, a light reflecting layer, a phosphor layer, and a surface protective layer was obtained.

5) Luminescent characteristics The fluorescent intensifying screen A emitted light with a narrow half-value width having a peak at 390 nm.

Claims (14)

A photothermographic material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder on at least one surface of a support,
1) The average silver iodide content of the photosensitive silver halide is 40 mol% or more,
2) A photothermographic material comprising a compound represented by the following general formula (I) or a salt thereof:

(In the formula, R ₁ and R ₁ ′ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, or a heterocyclic group, provided that they are not simultaneously a hydrogen atom). 2. The photothermographic material according to claim 1, wherein, in the general formula (I), R ₁ ′ is a hydrogen atom, and R ₁ is a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group. .   3. The photothermographic material according to claim 1, wherein 50% or more of the total projected area of the photosensitive silver halide is a tabular grain having an aspect ratio of 2 or more.   4. The photothermographic material according to claim 3, wherein the average equivalent circle diameter of the tabular grains is from 0.3 [mu] m to 5.0 [mu] m. 5. The compound represented by the general formula (I) or a salt thereof is a compound represented by the following general formula (II) or a salt thereof. 5. Photothermographic material:

(Wherein R ₂ represents a substituted or unsubstituted alkyl group, aryl group, or heterocyclic group, R ₃ represents a hydrogen atom or a substituent that can be substituted on a benzene ring, and n1 represents an integer of 1 to 5) N2 represents 0 or an integer of 1 to 4). 6. The photothermographic material according to claim 5, wherein the compound represented by the general formula (II) or a salt thereof is a compound represented by the following general formula (III) or a salt thereof.

(Wherein R ₂ has the same meaning as in formula (II)).   7. The photothermographic material according to claim 1, wherein the photosensitive silver halide is gold sensitized.   The photothermographic material according to claim 3, wherein the tabular grain has an aspect ratio of 5 or more and 100 or less.   9. The photothermographic material according to claim 1, wherein an average silver iodide content of the photosensitive silver halide is 60 mol% or more.   The photothermographic material according to claim 9, wherein the average silver iodide content of the photosensitive silver halide is 80 mol% or more.   11. The photothermographic material according to claim 1, further comprising a silver iodide complex forming agent. The heat according to any one of claims 1 to 11, comprising at least one thermal development accelerator represented by the following general formula (A-1) or (A-2). Photosensitive material:

(Wherein 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 formula, 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, or an alkylthio group. Represents an arylthio group, an acyloxy group, or a carbonate group, R ₃ and R ₄ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring, and R ₃ and R ₄ are connected to each other to form a condensed ring. You may do it.)   The photothermographic material according to claim 1, wherein the image forming layer is provided on both sides of a support. An X-ray image forming method using the photothermographic material according to any one of claims 1 to 13,
1) a step of superposing the photothermographic material and a fluorescent intensifying screen to perform radiation image exposure and recording a latent image on the photothermographic material;
2) a thermal development step of converting the latent image into a visible image by thermal development;
An image forming method comprising: