JP2006195282A - Heat-developable photosensitive material and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-developable photosensitive material that uses high silver iodide and its manufacturing method, and that is superior in image preservability and has low fogging, with high sensitivity. <P>SOLUTION: The manufacturing method of heat-developable photosensitive material is provided with an image forming layer at least on one side of the support, containing a non-photosensitive silver salt, photosensitive silver halide, and an image forming layer containing a reducing agent. The manufacturing method comprises at least a process of particle formation of the photosensitive silver halide; a process of mixing with the non-photosensitive silver salt; a process of preparation of coating liquid for image formation layer; and a process of coating the coating liquid on the support. Thiocyanate is added, after the chemical sensitizing process and before the coating process, when the chemical sensitizing process is included; or thiocyanate is added, after the particle formation process and before the coating process, if the chemical sensitization is not included. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material and a method for producing the same, and relates to a photothermographic material having high sensitivity and low fog and a method for producing the same.

  In recent years, in the medical field and the printing plate making field, dry development of photographic development processing is strongly desired from the viewpoint of environmental protection and space saving. In these fields, digitization has progressed, and image information is taken into a computer, stored, processed if necessary, and photothermographic material is developed by laser image setter or laser imager at the required place by communication. Systems that produce images on the spot and develop images on the spot are rapidly spreading. As a photothermographic material, it is necessary to form a clear black image having high resolution and sharpness that can be recorded by laser exposure with high illuminance. As such digital imaging recording materials, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed as general image forming systems, but the diagnostic ability is determined like medical images. It is unsatisfactory in terms of image quality (sharpness, graininess, gradation, color tone) and recording speed (sensitivity), and has not yet reached a level that can replace the conventional silver salt film for wet development.

  On the other hand, a thermal image forming system using an organic silver salt is already known. A photothermographic material is generally an image in which a photosensitive silver halide, a reducing agent, a reducible silver salt (eg, an organic silver salt) and, if necessary, a toning agent for controlling the color tone of silver are dispersed in a binder matrix. It has a formation layer.

  The photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, and is blackened by an oxidation-reduction reaction between silver halide or a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form a silver image. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure. As a result, a black silver image is formed in the exposed area. The photothermographic material is disclosed in many documents, and Fuji Medical Dry Imager FM-DPL has been put on the market as a medical image forming system.

  On the other hand, attempts have been made to apply the photothermographic material to a photographic material. 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 surface exposure. 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 (for example, see Patent Document 1), a photothermographic material using silver iodobromide tabular grains (for example, Patent Document 2). Or a photosensitive material for medical use 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.

However, these prior arts have insufficient sensitivity to be used as imaging materials. In particular, with silver iodide, sufficient sensitivity cannot be obtained even if tabular grains are used and the grain cross-sectional area is increased.
As means for increasing the sensitivity, it is disclosed in the patent literature that silver chloride, silver bromide and silver thiocyanate are deposited by epitaxial growth on the tabular silver iodide grains of the host, and silver chloride is particularly preferably mentioned ( For example, see Patent Document 4).
However, since these chemical sensitizations cause an increase in fogging, they have not reached sensitization until sufficient sensitivity is obtained.

In order to be used as a photographic photosensitive material, the photothermographic material is required to have higher sensitivity, and the image quality such as haze of the obtained image is further increased.
Japanese Patent No. 3229344 JP 59-142539 A JP-A-10-282606 JP 59-119344 A

  An object of the present invention is to provide a photothermographic material having high sensitivity and low fog and a method for producing the same. A more specific object of the present invention is to provide a photothermographic material having high sensitivity and low fog suitable for direct photographing applications and excellent stability of fog and sensitivity in storage before photographing, and a method for producing the same. is there.

The above object of the present invention has been achieved by the following means.
<1> A method for producing a photothermographic material having an image forming layer containing a non-photosensitive silver salt, a photosensitive silver halide, and a reducing agent on at least one surface of a support, the production method comprising: At least a step of forming a grain of the photosensitive silver halide, a step of mixing with the non-photosensitive silver salt, a step of preparing the image forming layer coating solution, and a step of coating the coating solution on the support; A method for producing a photothermographic material, comprising adding a thiocyanate after the grain formation step and before the coating step.
<2> A chemical sensitization step is provided between the particle formation step and the mixing step of the non-photosensitive silver salt, and the thiocyanate is added in the step after the chemical sensitization step and before the coating step. The method for producing a photothermographic material according to <1>, wherein the photothermographic material is added.
<3> The photothermographic material according to <1> or <2>, wherein the thiocyanate is added in an amount of 1 × 10 ⁻⁵ mol% to 1 mol% with respect to the photosensitive silver halide. Manufacturing method.
<4> The photothermographic material according to <3>, wherein the thiocyanate is added in an amount of 1 × 10 ⁻⁴ mol% or more and 1 × 10 ⁻¹ mol% or less based on the photosensitive silver halide. Manufacturing method.
<5> The photothermographic material according to <4>, wherein the thiocyanate is added to the photosensitive silver halide in an amount of 1 × 10 ⁻³ mol% to 1 × 10 ⁻¹ mol%. Manufacturing method.
<6> The method for producing a photothermographic material according to any one of <1> to <5>, wherein the thiocyanate is an alkali metal salt of thiocyanate.
<7> The method for producing a photothermographic material according to any one of <2> to <6>, wherein the chemical sensitization step of the photosensitive silver halide includes chalcogen sensitization.
<8> The method for producing a photothermographic material according to <7>, wherein the chalcogen sensitization is at least one selected from sulfur sensitization, selenium sensitization, and tellurium sensitization.
<9> The method for producing a photothermographic material according to any one of <2> to <8>, wherein the chemical sensitization step of the photosensitive silver halide includes gold sensitization.
<10> The photothermographic material according to any one of <1> to <9>, wherein the thiocyanate is added in a step prior to the step of mixing with the non-photosensitive silver salt. Production method.
<11> The method for producing a photothermographic material according to any one of <1> to <9>, wherein the thiocyanate is added in a mixing step with the non-photosensitive silver salt.
<12> The method for producing a photothermographic material according to any one of <1> to <9>, wherein the thiocyanate is added in the step of preparing the image forming layer coating solution.
<13> The thermal development according to any one of <1> to <12>, wherein 50% or more of the projected area of the photosensitive silver halide is a tabular grain having an aspect ratio of 2 or more. A method for producing a photosensitive material.
<14> The method for producing a photothermographic material according to <13>, wherein the tabular grain has an average equivalent sphere diameter of 0.3 μm or more and 8.0 μm or less.
<15> The method for producing a photothermographic material according to any one of <1> to <14>, wherein the photosensitive silver halide has an average silver iodide content of 40 mol% or more.
<16> The method for producing a photothermographic material according to <15>, wherein the photosensitive silver halide has an average silver iodide content of 80 mol% or more.
<17> The method for producing a photothermographic material according to <16>, wherein the photosensitive silver halide has an average silver iodide content of 90 mol% or more.
<18> A photothermographic material produced by the method for producing a photothermographic material according to any one of <1> to <17>.
<19> The photothermographic material according to <18>, wherein the thiocyanate is contained in an amount of 1 × 10 ⁻⁴ mol% to 1 mol% with respect to the photosensitive silver halide.
<20> The photothermographic material according to <19>, wherein the thiocyanate salt is contained in an amount of 1 × 10 ⁻³ mol% to 1 × 10 ⁻¹ mol% with respect to the photosensitive silver halide. .

  According to the present invention, it is possible to provide a photothermographic material having high sensitivity and low fog and having excellent stability of fog and sensitivity during storage before photographing, and a method for producing the same.

1. Photothermographic material The photothermographic material of the invention has an image forming layer containing a photosensitive silver halide, a non-photosensitive organic silver salt, and a reducing agent on at least one surface of a support. Further, a surface protective layer may be provided on the image forming layer, and a back layer or a back surface protective layer may be provided on the opposite surface.

(Method for producing photothermographic material)
The method for producing a photothermographic material of the present invention comprises at least a photosensitive silver halide grain forming step, a mixing step with a non-photosensitive silver salt, an image forming layer coating solution preparing step, and the coating solution on a support. The process of apply | coating to.
In the method for producing a photothermographic material of the present invention, when a chemical sensitization step is present, the chemical sensitization step is performed after the chemical sensitization step, before the coating step, and when no chemical sensitization step is present, The thiocyanate is added after the silver halide grain forming step and before the coating step. Preferably, the chemical sensitization step is added in at least one of a step following the chemical sensitization step substantially completed, a step of mixing with a non-photosensitive silver salt, and a step of preparing an image forming layer coating solution. More preferably, it is a mixing step with a non-photosensitive silver salt, or a step of preparing an image forming layer coating solution. You may divide and add to the mixing process with a non-photosensitive silver salt, and the preparation process of an image forming layer coating liquid.

Conventionally, it is known that silver halide by thiocyanate is present during chemical sensitization, or that silver thiocyanate is joined to silver halide grains for chemical sensitization. However, since silver thiocyanate is conventionally present in a light-sensitive material, it has been considered to have adverse effects such as fogging during storage before photographing and change in sensitivity. In addition, thiocyanate is a silver halide solvent, and in the case of fine grain emulsions commonly used in heat development and silver halide having a fine structure such as an epitaxial part on the host grain, silver halide is dissolved or grains. Due to the change in shape, it was necessary to pay sufficient attention to its use.
The present inventor diligently studied the effect of thiocyanate on the photosensitive silver halide. As a result, the thiocyanate was formed in a step after the formation of the photosensitive silver halide grains and chemical sensitization were substantially completed. When added, a substantial sensitizing effect is not recognized, but it has been found that it has an effect of suppressing an increase in fog during storage of the photothermographic material. In particular, it was effective in suppressing fog when a tabular silver halide emulsion was subjected to chemical sensitization such as chalcogen sensitization or gold sensitization. Conventional thiocyanate can obtain an effective increase in sensitivity by being present during chemical sensitization, but it has been generally recognized that it involves a change in fog and sensitivity over time. The effect was totally unexpected.

  The substantial increase in sensitivity in the present invention means that the change in exposure necessary to obtain a density of 1.0 becomes 1 / 1.5 or less by the addition of thiocyanate.

  Examples of thiocyanate include alkali metal salts of thiocyanic acid (eg, lithium salt, sodium salt, potassium salt), alkaline earth salts (eg, calcium salt, barium salt, strontium salt), and ammonium salt (ammonium salt). Trimethylammonium salt, tetramethylammonium salt, triethylammonium salt, tetraethylammonium salt, etc.) can be used, and an alkali metal salt of thiocyanic acid is preferred.

In the present invention, the thiocyanate can be added as an aqueous solution or as a dispersion when water-insoluble.
In the present invention, the addition amount of thiocyanate is preferably 1 × 10 ⁻⁵ mol to 1 mol, and more preferably 1 × 10 ⁻⁴ mol to 1 × 10, with respect to 1 mol of silver halide. ⁻¹ mol, more preferably 1 × 10 ⁻³ mol to 1 × 10 ⁻¹ mol.

(Photosensitive silver halide)
1) Halogen composition The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and is silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide, silver iodide. Can be used. Silver bromide, silver iodobromide and silver iodide are preferred. More preferably, it is a high silver iodide grain having a silver iodide content of 40 mol% or more. The rest of the silver halide composition is not particularly limited, and can be arbitrarily selected from organic silver salts such as silver chloride, silver bromide, silver thiocyanate or silver phosphate.

  More preferably, the photosensitive silver halide used in the present invention has a silver iodide content of 80 mol% or more, and most preferably 90 mol% or more.

  The distribution of the halogen composition in the grains may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Moreover, as a structure in which silver halide grains having a core / shell structure can be preferably used, those having a 2- to 5-fold structure are preferable, and core-shell grains having a 2- to 4-fold structure can be used more preferably. 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.

  Silver iodide that can be preferably used in the present invention can have any 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, Volume 161, No. 3, p. Reference may be made to 848-851 (1967).

2) Grain size and grain shape The silver halide having a high silver iodide content that can be preferably used in the present invention can take a complicated form. L. JENKINS et al. J of Photo. Sci. Vol. 28 (1980), p164, FIG. FIG. Tabular grains as shown in Fig. 1 are also preferably used. Grains with rounded corners of silver halide grains can also be preferably used.
The surface index (Miller index) of the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the [100] plane having high spectral sensitization efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The ratio is preferably 50% or more, more preferably 65% or more, and still more preferably 80% or more. The ratio of the Miller index [100] plane is determined by T.T. Tani; Imaging Sci. , Vol. 29, p. 165 (1985).

The photosensitive silver halide according to the present invention is also a preferred embodiment in which the silver halide grains are tabular silver halide grains having a projected area of 50% or more and an aspect ratio of 2 or more and 100 or less. More preferable are tabular grains having an aspect ratio of 3 to 50, and more preferable are tabular grains having an aspect ratio of 5 to 30.
The present invention can have the effects of the present invention in any size, but in the case of large-sized grains and tabular grains with higher sensitivity, fogging during storage of the light-sensitive material, and large fluctuations in sensitivity, The effect of the present invention is more remarkable. The tabular grains preferably have an average sphere equivalent diameter of 0.3 μm or more and 8.0 μm or less, and more preferably 0.5 μm or more and 5.0 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 obtain | require by calculating | requiring the particle | grain volume from each projected area and thickness observed with the electron microscope, and converting into the sphere of the same volume as the volume.
The tabular grains in the present invention preferably have an average projected area equivalent diameter of 0.1 μm to 10 μm, and more preferably 0.2 μm to 5 μm.

  The tabular silver halide grains that can be preferably used in the present invention are preferably those obtained by (1) epitaxially growing a silver salt on a flat plate, or (2) having one or more dislocation lines.

Epitaxial particles are in a form that can be more preferably used in the present invention.
The terms “epitaxy” and “epitaxial” as used herein are recognized in the art to point out that the silver salt is a crystalline form with an orientation controlled by the host tabular grains. Used in meaning.
In order to create a sensitized site on the tabular host grain, a silver salt deposited by epitaxial growth can be used. By controlling the adhesion site by epitaxial growth, selective local sensitization of tabular host grains can be performed. Thus, sensitization sites can be provided at one or more regular sites. “Regular” means that the sensitized sites have a predictable and ordered relationship, preferably with each other, with respect to the main crystal planes of the tabular grains. By controlling the epitaxial adhesion with respect to the main crystal plane of the tabular grains, it is possible to control the number of sensitized sites and the spacing in the lateral direction.

In particular, it is preferable to control silver salt epitaxy and substantially eliminate epitaxial adhesion in at least a part of the main crystal plane of the tabular host grain. In tabular host grains, silver salt epitaxial deposition tends to occur at grain edges and / or corners.
When the epitaxial deposition is limited to selected portions of the tabular grains, the sensitivity is improved as compared with the case where the silver salt is randomly deposited on the main surface of the tabular grains by epitaxial growth. The silver salt is adhered to the selected portion within a limited range so that the silver salt is not substantially epitaxially deposited on at least a part of the main crystal plane. The deposition range can be varied over a wide range without departing from the invention. In general, as the amount of epitaxial coating on the main crystal plane decreases, the increase in sensitivity increases. The silver salt deposited by epitaxial growth is preferably less than half of the area of the main crystal plane of the tabular grains, preferably less than 25%. When silver salt is deposited by epitaxial growth at the corners of the tabular silver halide grains, it is preferable to limit the area to less than 10%, more preferably less than 5%, of the area of the main crystal plane of the tabular grains. In certain embodiments, it has been observed that epitaxial deposition begins on the edge surfaces of tabular grains. Therefore, depending on conditions, epitaxy is limited to the selected edge portion, and epitaxy on the main crystal plane is effectively eliminated.

  When particles with latent image centers are fully developed, the location and number of latent image centers cannot be determined. However, if the development is stopped before the development range is expanded from the immediate vicinity of the latent image center and the partially developed particles are enlarged and observed, the partial development site can be clearly seen. These portions generally correspond to the latent image center, and such latent image center generally corresponds to the sensitized portion.

  The silver salt deposited by epitaxy can be selected from any silver salt that is conventionally known to be epitaxially grown on silver halide grains and to be effective in photography. In particular, the silver salt is preferably selected from those conventionally known to be effective for forming a shell of a core-shell silver halide emulsion. In addition to all known photographically useful silver halides, other silver salts known to be capable of depositing on silver halide grains as silver salts, such as silver thiocyanate, silver cyanide, silver carbonate Silver ferricyanide, silver arsenate or silver arsenite, and silver chromate. Among these, silver chloride or silver bromide is preferable.

Depending on the silver salt chosen and the intended use, the silver salt can be effectively deposited in the presence of the modifying compound along with the tabular silver halide grains.
From the host grains, iodide can enter the silver salt epitaxy. The host particles can contain anions other than iodine ions up to the solubility limit in silver iodide.

The silver halide in the present invention preferably has one or more dislocation lines. More preferred is a silver halide having 5 or more dislocation lines, and particularly preferred is a silver halide having 10 or more dislocation lines.
It is preferable that the tabular grains containing one or more dislocation lines have a projected area of 50% or more, more preferably 80% or more of the total silver halide grains. In particular, it is preferable that the silver halide grains containing 10 or more dislocation lines are 80% or more.
Regarding dislocations in silver halide crystals,
・ C. R Berry, J .; Appl. Phys. , Vol. 27, p. 636 (1956)
・ C. R Berry, D.C. C. Skilman, J.M. Appl. Phys. , Vol. 35, p. 2165 (1964)
・ J. F. Hamilton, Photo. Sci. Eng. , Vol. 11, p. 57 (1967)
・ T. Shiozawa, J. et al. Soc. Photo. Sci. JAP. , Vol. 34, p. 16 (1971)
・ T. Shiozawa, J. et al. Soc. Photo. Sci. JAP. , Vol. 35, p. 213 (1972)
It is possible to observe dislocations in the crystal by X-ray diffraction or low-temperature transmission electron microscopy, and various dislocations are generated in the crystal by applying strain to the crystal. What happens is described.

On the other hand, as an effect of dislocations on photographic performance, G. C. Fame 11, R.E. B. Flint, and J.M. B. Chanter, J .; Photo. Sci. , Vol. 13, p. 25 (1965), it is shown that in a large-sized high-aspect-ratio tabular silver bromide grain, the place where the latent image nucleus is formed and the defect in the grain are closely related.
JP-A-62-220238 and JP-A-1-201649 disclose tabular silver halide grains into which dislocations are intentionally introduced. Tabular grains incorporating dislocations are superior in photographic properties such as sensitivity and reciprocity, compared to tabular grains without dislocations, and when these are used in photothermographic materials, sharpness and graininess may be excellent. It is shown. However, in these grains, dislocation lines are irregularly introduced at the edges of the tabular grains, and the number of dislocations varies from grain to grain.

3) Coating amount Generally, in the case of a photothermographic material in which silver halide remains as it is after heat development, increasing the silver halide coating amount lowers the transparency of the film and is undesirable from the viewpoint of image quality. Despite the request, it was low and limited. 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.

4) Heavy Metal The photosensitive silver halide grain of the present invention can contain a metal or metal complex of Group 8 to Group 10 of the Periodic Table (showing Groups 1 to 18). The metal of Group 8 to Group 10 of the periodic table or the central metal of the metal complex is preferably iron, rhodium, ruthenium or iridium. 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 containing a hexacyano metal complex 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. .

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

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.

5) Gelatin As the gelatin contained in the photosensitive silver halide emulsion used in the present invention, various gelatins can be used. In order to satisfactorily maintain the dispersion state of the photosensitive silver halide emulsion in the organic silver salt-containing coating solution, it is preferable to use low molecular weight gelatin having a molecular weight of 500 to 60,000. These low molecular weight gelatins may be used at the time of particle formation or dispersion after desalting, but are preferably used at the time of dispersion after desalting.

6) Chemical sensitization The photosensitive silver halide used in the present invention may be non-chemically sensitized, but is preferably chemically sensitized.
The chemical sensitization referred to in the present invention means a chalcogen sensitization method and a gold sensitization method.
The reduction sensitization generally known as chemical sensitization, the sensitization method using a compound in which a one-electron oxidant formed by one-electron oxidation can emit one or more electrons, and the like are used in the present invention. Is not included. Examples of the chalcogen sensitizing method include a sulfur sensitizing method, a selenium sensitizing method, and a tellurium 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 (eg, dimorpholine disulfide, cystine, lenthionine (1,2,3,5,6-pentathiepane)), polythionates, elemental sulfur and active gelatin Etc. Rukoto 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, 6-175258, 6-180478, 6-208186, 6-208184, 6-317867, 7-92599, Selenium compounds described in JP-A-7-98483 and JP-A-7-140579 can be used.

Specifically, colloidal metal selenium, selenoureas (eg, N, N-dimethylselenourea, trifluoromethylcarbonyl-trimethylselenourea, acetyl-trimethylselenourea), selenoamides (eg, selenoamide, N, N-diethyl) Phenylselenoamide), phosphine selenides (eg, triphenylphosphine selenide, pentafluorophenyl-triphenylphosphine selenide), selenophosphates (eg, tri-p-tolylselenophosphate, tri-n) -Butylselenophosphate), selenoketones (for example, selenobenzophenone), isoselenocyanates, selenocarboxylic acids, selenoesters, diacyl selenides, 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, or 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. A compound can be used.

  Specifically, phosphine tellurides (for example, butyl-diisopropylphosphine telluride, tributylphosphine telluride, tributoxyphosphine telluride, ethoxydiphenylphosphine 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, and the like 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.

  Particularly, in the chalcogen sensitization of 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 5252455, Belgian Patent No. 691857 and the like can also be used. P. Platinum, palladium, or iridium other than gold described in Grafkides, Chimie et Physique Photographic (published by Paul Momtel, 1987, 5th edition), Research Disclosure magazine, 307, 307105, etc. It can also be used.

  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 in the presence of a silver halide solvent.
Specifically, thiocyanate (for example, potassium thiocyanate), a thioether compound (for example, compounds described in U.S. Pat. Nos. 3,021,215 and 3,271,157, JP-B-58-30571, JP-A-60-136736, 3,6-dithia 1.8-octanediol), tetrasubstituted thiourea compounds (for example, compounds described in JP-B-59-11892, US Pat. No. 4,221,863, etc., particularly tetramethylthiourea), and JP-B-60-11341 A thione compound described in JP-B-63-29727, a mesoionic compound described in JP-A-60-163042, a selenoether compound described in US Pat. No. 4,78,2013, and JP-A-2-118566 The described telluro ether compounds and sulfites can be mentioned. Among these, thiocyanate, thioether compound, tetrasubstituted thiourea compound and thione compound are preferable, and thiocyanate is particularly preferable. The amount used can be about 10 ⁻⁵ mol to 10 ⁻² mol per mol of silver halide. Unlike the thiocyanate of the present invention, the thiocyanate present at the time of chemical sensitization is substantially accompanied by an increase in sensitivity. Can be added.

  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 There may be (4) immediately before application after sensitization.

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 to 10 ⁻¹ mol, preferably 10 ⁻⁷ mol per mol of silver halide. About 10 to 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 to 10 ⁻² mol, more preferably 10 ⁻⁶ mol to 1 mol of silver halide. 5 × 10 ⁻³ mol. 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 is 3 to 10, preferably 4 to 9, temperature is 20 ° C. to 95 ° C., preferably 25 ° C. to 80 ° C. Degree.

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 more or pAg at 4 or less, and reduction sensitization is performed by introducing a single addition portion of silver ions during grain formation. Is also preferable.
The amount of the reduction sensitizer, likewise may vary depending on various conditions, per mol of silver halide 10 ^-7 mol to 10 ^-1 mol as a guide, and more preferably 10 ^-6 mol to 5 × 10 ^{- 2} moles.

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.

7) Compound in which 1-electron oxidant produced by 1-electron oxidation can emit 1 electron or more electrons In the photothermographic material of the present invention, 1-electron oxidant produced by 1-electron oxidation is 1 electron or 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: page 28) is a compound of type 1 that can be further released by one-electron oxidant produced by one-electron oxidation with subsequent bond cleavage reaction. Compounds PMT-1 to S-37 described in Table E and Table F on page 32), JP-A-9-211774, JP-A-11-95355 (specific examples: compounds INV1-36), JP-T 2001-500996 No. (specific examples: compounds 1 to 74, 80 to 87, 92 to 122), US Pat. No. 5,747,235, US Pat. No. 5,747,236, European Patent No. 786692A1 (specific examples: compounds INV 1 to 35) European Patent 893732A1, US Pat. No. 6,054,260, US Pat. No. 5,994,051, etc. Compound called donor sensitizer "and the like. 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 5-mercaptotetrazole group, 3-mercapto-1,2,4-triazole group, and benzotriazole group, most preferred are 3-mercapto-1,2,4-triazole group, and 5 -Mercaptotetrazole group.

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

  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 quaternary salt counter anions include halogen ions, carboxylate ions, sulfonate ions, sulfate ions, perchlorate ions, carbonate ions, nitrate ions, BF ₄ ⁻ , PF ₆ ⁻ , or Ph ₄ B ^−. Can be mentioned. 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 type 1 and type 2 compounds of 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 of 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 increased or decreased may be dissolved at a higher or lower pH and added.

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

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

Formula (I) A- (W) n-B
[In Formula (I), A represents a group capable of being 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 reducing group. Represents. ]

  In formula (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 a salt thereof) , A thione group (—C (═S) —), a heterocyclic group, a sulfide group, a disulfide group, a cationic group, or an ethynyl group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom, and a tellurium atom Etc.

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

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

In formula (I), W represents a divalent linking group. Any linking group may be used as long as it does not adversely affect photographic properties. For example, a divalent linking group composed of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom can be used. Specifically, an alkylene group having 1 to 20 carbon atoms (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 formula (I), the reducing group represented by B represents a group capable of reducing silver ions. For example, a triple bond group such as formyl group, amino group, acetylene group or propargyl group, mercapto group, hydroxylamines. Hydroxamic acids, hydroxyureas, hydroxyurethanes, hydroxysemicarbazides, reductones (including reductone derivatives), anilines, phenols (chroman-6-ols, 2,3-dihydrobenzofuran-5-ols, Aminophenols, sulfonamidophenols, and hydroquinones, catechols, resorcinols, benzenetriols, polyphenols such as bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. The residue after removing one And the like. Of course, these may have an arbitrary substituent.

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

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

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

  The compound of the formula (I) of the present invention may be a bis form or a tris form. The molecular weight of the compound of formula (I) of the present invention is preferably between 100 and 10,000, more preferably between 120 and 1000, particularly preferably between 150 and 500.

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

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

  The compounds of the present invention can be easily synthesized according to known methods. As the compound of the formula (I) of 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 the formula (I) of the present invention is preferably added to the silver halide emulsion layer (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 compound to be added, but generally 1 × 10 ⁻⁶ mol to 1 mol, preferably 1 × 10 ⁻⁵ mol to 1 mol of photosensitive silver halide. 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁴ mol to 1 × 10 ⁻¹ mol.

  The compound of the formula (I) of 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.

9) Sensitizing dye The sensitizing dye that can be applied to the present invention can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed on silver halide grains, and is suitable for the spectral characteristics of the exposure light source. Sensitizing dyes with sensitivity can be advantageously selected.
The photothermographic material of the present invention is preferably spectrally sensitized so as to have a spectral sensitivity peak at 600 nm to 900 nm, or 300 nm to 500 nm. Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A No. 11-65021, compounds represented by formula (II) of JP-A No. 10-186572, and formulas (I of JP-A No. 11-119374) ) And the dye described in Example 5 of U.S. Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59-48753. No. 19, page 38 to line 20, page 35 of European Patent Publication No. 0803764A1, JP 2001-272747, JP 2001-290238, JP 2002-23306, etc. It is described in. These sensitizing dyes may be used alone or in combination of two or more.

The addition amount of the sensitizing dye in the present invention, can be a desired amount depending on the property of sensitivity and fogging, silver halide in the image forming layer 1 mole per 10 ^-6 to 1 mol are preferred, Preferably, it is 10 ⁻⁴ mol to 10 ⁻¹ mol.

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

10) Concomitant use of silver halide 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, those having different halogen compositions). , Different crystal habits, different chemical sensitization conditions). 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.

11) Mixing of silver halide and organic silver salt It is particularly preferred that the photosensitive silver halide grains of the present invention are formed in the absence of non-photosensitive organic silver salt and chemically sensitized. This is because sufficient sensitivity may not be achieved by the method of forming silver halide by adding a halogenating agent to the organic silver salt. As a method of mixing silver halide and organic silver salt, separately prepared photosensitive silver halide and organic silver salt using a high-speed stirrer, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc. Alternatively, there may be mentioned a method of preparing an organic silver salt by mixing photosensitive silver halide which has been prepared at any timing during the preparation of the organic silver salt. In any method, the effects of the present invention can be preferably obtained.

12) Mixing of silver halide into coating solution The preferred addition time of the silver halide of the present invention to the image forming layer coating solution is from 180 minutes before application, preferably from 60 minutes to 10 seconds before application. However, the mixing 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.

(Compound that effectively reduces visible light absorption derived from photosensitive silver halide after heat development)
In the present invention, it is preferable to contain a compound that practically reduces visible light absorption derived from photosensitive silver halide after heat development compared to before heat development.
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.

<Description of silver iodide complex forming agent>
In the present invention, it is preferable to use a compound that can substantially reduce the spectral absorption intensity in the ultraviolet-visible range derived from photosensitive silver halide by heat development, and particularly preferably a 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 the sequential stability constant or the total stability constant, but depends on the combination of the three 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 Such as Dorin, or isoindoline, it can be mentioned.
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, or 1,3,5-triazine. 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, Alkynyl 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 (Carbonimidoyl group), formyl group, hydroxy group, alkoxy group (ethylene (Including groups containing a repeating unit of xy group or propyleneoxy group), 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, sulfonamido group, ureido group, thioureido group, imide group, (alkoxy or aryloxy) carbonylamino group, sulfamoylamino group, semicarbazide group, ammonio group, oxamoyl group Amino group, N- (alkyl or aryl) sulfonylureido group, N-acylureido group, N-acylsulfamoylamino group, nitro group, heterocyclic group containing a quaternized nitrogen atom (eg pyridinio group, imidazoli Group, quinolinio 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- Examples include a sulfonylsulfamoyl 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 ring of the present invention is a cation (e.g., pyridinium, triazolium Etc.) to form an inner salt.

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, a sulfide group, and a thione group as substituents, pyridine, thiazole, isothiazole, oxazole, isoxazole, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, triazine, triazole, thiadiazole or An oxadiazole 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 the general formula (1), R ¹¹ and R ¹² represent a hydrogen atom or a substituent. In the general formula (2), R ²¹ and R ²² represent 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 represents 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. Preferred are a halogen atom, alkyl group, aryl group, carbamoyl group, hydroxy group, alkoxy group, aryloxy group, carbamoyloxy group, amino group, acylamino group, ureido group, (alkoxy or aryloxy) carbonylamino group, and the like. .

  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, or 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 to} R ⁶³ each independently represents 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 an 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, or 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. The silver iodide complex forming agent in the present invention is preferably prepared so that the melting point of the compound is in an appropriate range so that it is melted 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 to 1000, still more preferably 50, relative to the photosensitive silver halide. The range is from mol% to 300 mol%.

(Phthalic acid and its derivatives)
In this invention, it is preferable to contain the compound chosen from a phthalic acid and its derivative with a silver iodide complex formation agent. As the phthalic acid and derivatives thereof used in the present invention, compounds represented by the following general formula (PH) are preferable.

  In the formula, T represents a halogen atom (fluorine, bromine, iodine), an alkyl group, an aryl group, an alkoxy group, or a nitro group, and k represents an integer of 0 to 4. When k is 2 or more, a plurality of k may be the same as or different from each other. k is preferably 0 to 2, and more preferably 0 or 1.

  The compound of the general formula (PH) may be used as it is, or may be used as an appropriate salt from the viewpoint of easy addition to the coating solution and pH adjustment. As the salt, an alkali metal salt, an ammonium salt, an alkaline earth metal salt, an amine salt, or the like can be used. Preference is given to alkali metal salts (Li, Na, K etc.) and ammonium salts.

  Specific examples of phthalic acid and derivatives thereof used in the present invention are listed below, but the present invention is not limited to these compounds.

In the present invention, phthalic acid and derivatives thereof are 1.0 × 10 ⁻⁴ mol to 1 mol, preferably 1.0 × 10 ⁻³ mol to 0.5 mol, more preferably per mol of silver applied. Is 2.0 × 10 ⁻³ mol to 0.2 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 at the time of dispersion. In the present invention, the amount of the photosensitive silver salt in the aqueous dispersion to be dispersed is preferably 1 mol% or less, more preferably 0.1 mol% or less with respect to 1 mol of the organic acid silver salt in the liquid. Further, it is more preferable that no positive photosensitive silver salt is added.

  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 ′ can each independently be substituted with a hydrogen atom or a benzene ring. represents a substituent .L is, -S- group or a -CHR ¹³ - .X ¹ and X ¹ .R ¹³ represents a group represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms' each independently represent a hydrogen atom Or represents a substitutable group on the 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 , such as a halogen atom, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an acylamino group, a sulfonamide group, a sulfonyl group, a phosphoryl group, an 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 4 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 or t- A butyl group is most preferred.

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

L is preferably a —CHR ¹³ — group.
R ¹³ is preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms. As the alkyl group, a cyclic alkyl group is also preferably used in addition to a chain alkyl group. Moreover, what has a C = C bond in these alkyl groups can also be used preferably. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, 2,4,4-trimethylpentyl group, cyclohexyl group, 2,4-dimethyl-3-cyclohexenyl group, 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 adjusted by combining two or more kinds of reducing agents, it is preferable to use two or more kinds in combination 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)
In the photothermographic material of the present invention, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, or the like as a development accelerator, Hindered phenol compounds represented by general formula (II) described in JP-A No. 2001-92075, general formula (I) described in JP-A Nos. 10-62895 and 11-15116, A hydrazine-based compound represented by the general formula (D) of JP-A No. 2002-156727 or the general formula (1) described in JP-A No. 2002-278017, and described in the specification of JP-A No. 2001-264929 Phenol-based or naphthol-based compounds represented by the general formula (2) 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 ester group. R ₃ and R ₄ each represents a group that can be substituted on the benzene ring mentioned in the example of the substituent of formula (A-1). R ₃ and R ₄ may be connected to each other to form a condensed ring.
R ₁ is preferably an alkyl group having 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, an isopropyl group, a butyl group, a tert-octyl group, 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. R2 is preferably a halogen atom (more preferably a chlorine atom or a bromine atom), an alkoxy group (for example, methoxy group, butoxy group, n-hexyloxy group, n-decyloxy group, cyclohexyloxy group, benzyloxy group, etc.), aryloxy A 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 as a substituent is 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 represented by R ²¹ to R ²³ include a methyl group, an ethyl group, a butyl group, an octyl group, a dodecyl group, an isopropyl group, a t-butyl group, a t-amyl group, a t-octyl group, a cyclohexyl group, Examples thereof include 1-methylcyclohexyl group, benzyl group, phenethyl group, 2-phenoxypropyl group and the like.
Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-t-butylphenyl group, a 4-t-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group.
Alkoxy groups include methoxy, ethoxy, butoxy, octyloxy, 2-ethylhexyloxy, 3,5,5-trimethylhexyloxy, dodecyloxy, cyclohexyloxy, 4-methylcyclohexyloxy, benzyl An oxy 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. .

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%.

(Description of binder)
The binder of the organic silver salt-containing layer in the present invention may be any polymer, and suitable binders are transparent or translucent and generally colorless, natural resins and polymers and copolymers, synthetic resins and polymers and copolymers, etc. Film forming media such as gelatins, gums, poly (vinyl alcohol) s, hydroxyethyl celluloses, cellulose acetates, cellulose acetate butyrates, poly (vinyl pyrrolidone) s, casein, starch, poly (acrylic acid) ), Poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers , Poly (vinyl acetals) (e.g., poly (vinyl Nilformal) and poly (vinyl butyral)), poly (esters), poly (urethanes), phenoxy resins, poly (vinylidene chloride) s, poly (epoxides), poly (carbonates), poly (vinyl acetate) , Poly (olefin) s, cellulose esters, and poly (amides). The binder may be formed from water, an organic solvent or an emulsion.

  In the present invention, the glass transition temperature of the binder of the layer containing the organic silver salt is preferably 10 ° C. or higher and 80 ° C. or lower, more preferably 20 ° C. to 70 ° C., and 23 ° C. or higher and 65 ° C. or lower. More preferably.

In this specification, Tg is calculated by the following formula.
1 / Tg = Σ (Xi / Tgi)

Here, it is assumed that n monomer components from i = 1 to n are copolymerized in the polymer. Xi is the weight fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n.
As the transition temperature value (Tgi) of the homopolymer glass of each monomer, the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)) was adopted.

  The polymer used as the binder may be used alone or in combination of two or more as required. Further, a glass transition temperature of 20 ° C. or higher and a glass transition temperature of less than 20 ° C. may be used in combination. When two or more kinds of polymers having different Tg are blended and used, the weight average Tg is preferably within the above range.

In the present invention, when the organic silver salt-containing layer is formed using a coating solution in which 30% by mass or more of the solvent is water and dried, the binder of the organic silver salt-containing layer is further added to an aqueous solvent ( When it is soluble or dispersible in an aqueous solvent), the performance is improved particularly when it is made of a latex of a polymer having an equilibrium water content of 2% by mass or less at 25 ° C. and 60% RH.
The most preferable form is one prepared so that the ionic conductivity is 2.5 mS / cm or less, and as such a preparation method, there is a method of purifying using a separation functional membrane after polymer synthesis.

The aqueous solvent in which the polymer is soluble or dispersible here is a mixture of water or water with 70% by mass or less of a water-miscible organic solvent.
Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, cellosolvs such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, ethyl acetate, and dimethylformamide.

The “equilibrium moisture content at 25 ° C. and 60% RH” is the following using the weight W1 of the polymer in the humidity-controlled equilibrium under the atmosphere of 25 ° C. and 60% RH and the weight W0 of the polymer in the absolutely dry state at 25 ° C. It can be expressed as
Equilibrium moisture content at 25 ° C. and 60% RH = {(W1−W0) / W0} × 100 (mass%)
For the definition and measurement method of the moisture content, for example, Polymer Engineering Course 14, Polymer Materials Testing Method (Edited by Polymer Society, Jinshokan) can be referred to.

  The equilibrium water content at 25 ° C. and 60% RH of the binder polymer in the present invention is preferably 2% by mass or less, more preferably 0.01% by mass or more and 1.5% by mass or less, and still more preferably 0.02%. Desirably, the content is from 1% by mass to 1% by mass.

  The binder in the present invention is particularly preferably a polymer that can be dispersed in an aqueous solvent. Examples of the dispersed state include latex in which fine particles of a water-insoluble hydrophobic polymer are dispersed and polymer molecules in which a molecular state or micelle is dispersed, and all are preferable. The average particle size of the dispersed particles is preferably 1 to 50000 nm, more preferably about 5 to 1000 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution.

  In the present invention, preferred embodiments of the polymer that can be dispersed in an aqueous solvent include acrylic polymers, poly (esters), rubbers (eg, SBR resin), poly (urethanes), poly (vinyl chloride) s, poly (acetic acid). Hydrophobic polymers such as vinyl), poly (vinylidene chloride) and poly (olefin) can be preferably used. These polymers may be linear polymers, branched polymers, crosslinked polymers, so-called homopolymers obtained by polymerizing a single monomer, or copolymers obtained by polymerizing two or more types of monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer.

  These polymers have a number average molecular weight of 5,000 to 1,000,000, preferably 10,000 to 200,000. When the molecular weight is too small, the mechanical strength of the image forming layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable.

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

Latex of P-1; -MMA (70) -EA (27) -MAA (3)-(molecular weight 37000, Tg 61 ° C.)
Latex of P-2; -MMA (70) -2EHA (20) -St (5) -AA (5)-(molecular weight 40000, Tg 59 ° C.)
P-3; latex of -St (50) -Bu (47) -MAA (3)-(crosslinkability, Tg-17 ° C)
Latex of P-4; -St (68) -Bu (29) -AA (3)-(crosslinkability, Tg 17 ° C.)
Latex of P-5; -St (71) -Bu (26) -AA (3)-(crosslinkability, Tg 24 ° C.)
Latex of P-6; -St (70) -Bu (27) -IA (3)-(crosslinkability)
Latex of P-7; -St (75) -Bu (24) -AA (1)-(crosslinkability, Tg 29 ° C.)
P-8; Latex (crosslinkable) of -St (60) -Bu (35) -DVB (3) -MAA (2)-
Latex (crosslinkability) of P-9; -St (70) -Bu (25) -DVB (2) -AA (3)-
P-10; Latex (molecular weight 80000) of -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-
P-11; latex of VDC (85) -MMA (5) -EA (5) -MAA (5)-(molecular weight 67000)
Latex of P-12; -Et (90) -MAA (10)-(molecular weight 12000)
Latex of P-13; -St (70) -2EHA (27) -AA (3) (molecular weight 130000, Tg 43 ° C.)
P-14; latex of MMA (63) -EA (35) -AA (2) (molecular weight 33,000, Tg 47 ° C.)
Latex of P-15; -St (70.5) -Bu (26.5) -AA (3)-(crosslinkability, Tg 23 ° C.)
Latex of P-16; -St (69.5) -Bu (27.5) -AA (3)-(crosslinkability, Tg 20.5 ° C)

  The abbreviations for the above structures represent the following monomers. MMA; methyl methacrylate, EA; ethyl acrylate, MAA; methacrylic acid, 2EHA; 2-ethylhexyl acrylate, St; styrene, Bu; butadiene, AA; acrylic acid, DVB; divinylbenzene, VC; vinyl chloride, AN; acrylonitrile, VDC Vinylidene chloride, Et; ethylene, IA; itaconic acid.

The polymer latex described above is also commercially available, and the following polymers can be used. Examples of the acrylic polymer include Sebian A-4635, 4718, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.), poly ( Examples of esters) include, for example, poly (urethanes) such as FINETEX ES650, 611, 675, 850 (above made by Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (more made by Eastman Chemical). Examples of rubbers such as HYDRAN AP10, 20, 30, and 40 (manufactured by Dainippon Ink Chemical Co., Ltd.) include LACSTAR 7310K, 3307B, 4700H, and 7132C (manufactured by Dainippon Ink Chemical Co., Ltd.), Nipol Lx416, 410, 438C, 2507 (all manufactured by Nippon Zeon Co., Ltd.), etc. Examples of poly (vinyl chloride) s include G351 and G576 (manufactured by Nippon Zeon Co., Ltd.), and examples of poly (vinylidene chloride) include L502 and L513 (manufactured by Asahi Kasei Kogyo Co., Ltd.) Examples of poly (olefin) s include Chemipearl S120, SA100 (manufactured by Mitsui Petrochemical Co., Ltd.).
These polymer latexes may be used alone or in combination of two or more as required.

  As the polymer latex used in the present invention, a styrene-butadiene copolymer latex is particularly preferable. The weight ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably 40:60 to 95: 5. The proportion of the styrene monomer unit and the butadiene monomer unit in the copolymer is preferably 60 to 99% by mass. The preferred molecular weight range is the same as described above.

  Examples of latexes of styrene-butadiene copolymer that are preferably used in the present invention include the aforementioned P-3 to P-8, 14, and 15, commercially available products LACSTAR-3307B and 7132C, Nipol Lx416, and the like.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, hydroxypropylcellulose, carboxymethylcellulose may be added to the organic silver salt-containing 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 organic silver salt-containing layer.

  The organic silver salt-containing layer (that is, the image forming layer) in the present invention is preferably formed using a polymer latex as a binder. The amount of the binder in the organic silver salt-containing layer is preferably such that the weight ratio of total binder / organic silver salt is 1/10 to 10/1, more preferably 1/5 to 4/1.

  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 weight ratio of silver halide is preferably 400-5, more preferably 200-10.

The total amount of binder in the image forming layer in the present ^{invention, 0.2g / m 2 ~30g / m} 2, more preferably from 1g / m ² ~15g / m ² is preferred. 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.

  In the present invention, the organic silver salt-containing layer coating solution of the photothermographic material is preferably an aqueous solvent containing 30% by mass or more of water for the sake of simplicity. 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 is more preferably 50% by mass or more, and still more preferably 70% by mass or more.

  Specific examples of the preferred solvent composition include water 100, water / methyl alcohol = 90/10, water / methyl alcohol = 70/30, water / methyl alcohol / dimethylformamide = 80/15/5, water / methyl. Alcohol / ethyl cellosolve = 85/10/5, water / methyl alcohol / isopropyl alcohol = 85/10/5, etc. (numerical values are mass%).

(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-10-62899, page 20 line 57 to page 21, line 7 of EP-A-0803764. Compounds described in JP-A-9-281737 and JP-A-9-329864, compounds described in US Pat. Nos. 6,083,681, 6,083,681, and European Patent 1048875 It is done.

1) Organic polyhalogen compound Hereinafter, preferred organic polyhalogen compounds that can be used in the present invention will be described in detail. A preferred polyhalogen compound of the present invention is a compound represented by the following general formula (H).
General formula (H)
Q- (Y) n-C (Z ₁ ) (Z ₂ ) X
In the general formula (H), Q represents an alkyl group, an aryl group or a heterocyclic group, Y represents a divalent linking group, n represents 0 to ₁ , Z ₁ and Z ₂ represent a halogen atom, X represents a hydrogen atom or an electron withdrawing group.
In general formula (H), Q is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heterocyclic group containing at least one nitrogen atom (pyridine, quinoline group, etc.).
In the general formula (H), when Q is an aryl group, Q preferably represents a phenyl group substituted with an electron-attracting 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, and 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 a bis type, a tris type, or a tetrakis type) can also be preferably used.
In 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, a pyridinium group Etc.), those having a polyethyleneoxy group, a hydroxyl group or the like as a substituent are also preferred forms.

  Examples of the polyhalogen compound that can be used in the present invention include US Pat. No. 3,874,946, US Pat. No. 4,756,999, US Pat. No. 5,340,712, US 5369000, US Pat. No. 5,464,737, US Pat. 59-57234, JP-A-7-2781, 7-7621, 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, JP 2000-284410, JP 2000-2 4412, JP-A-2001-33911, JP-A-2001-31644, JP-A-2001-312027, and JP-A-2003-50441 are preferably used. The compounds specifically exemplified in JP-A-7-2781, JP-A-2001-33911, and JP-A-2001-312027 are preferred.

The compound represented by the general formula (H) of the present invention is preferably used in the range of 10 ⁻⁴ mol to 0.8 mol, more preferably 10 ⁻ per mol of the non-photosensitive silver salt in the image forming layer. It is preferably used in the range of ³ mol to 0.1 mol, more preferably in the range of 5 × 10 ⁻³ mol to 0.05 mol.
In particular, when the silver halide having a high silver iodide content of the present invention is used, the amount of the compound of the general formula (H) is important in order to obtain a sufficient antifogging effect. Most preferably, it is used in the range of 10 ⁻³ mol to 0.03 mol.

  In the present invention, examples of the method for incorporating the compound represented by the general formula (H) into the photothermographic material include the methods described in the method for containing a reducing agent.

  The melting point of the compound represented by the general formula (H) is preferably 200 ° C. or lower, more preferably 170 ° C. or lower.

  Specific examples of the antifogging agent including the compound represented by formula (H) in the present invention are shown below, but the present invention is not limited thereto.

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.
Antifogging agent, stabilizer and stabilizer precursor that can be used in the present invention described in paragraph No. 0070 of JP-A No. 10-62899, page 20, line 57 to page 21, line 7 of European Patent No. 0803764A1 Patented compounds and compounds described in JP-A-9-281737 and JP-A-9-329864 are exemplified.

  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 organic silver salt-containing layer.

  The azolium salt may be added at any step in the coating solution preparation. When added to the organic silver salt-containing layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. To immediately before coating. 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 to control development by suppressing or accelerating development, to improve spectral sensitization efficiency, and to improve storage stability before and after development. And thione compounds, paragraphs 0067 to 0069 of JP-A-10-62899, compounds represented by formula (I) of JP-A-10-186572, and specific examples thereof include paragraph numbers 0033 to 0052. , European Patent Publication No. 0803764A1, page 20, lines 36 to 56, JP-A-2001-1003008 and the like. Of these, mercapto-substituted heteroaromatic compounds are preferred.

2) Toning agent In the photothermographic material of the invention, it is preferable to add a toning agent. For the toning agent, paragraphs 0054 to 0055 of JP-A No. 10-62899, p. Lines 21, 23 to 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, A combination of diammonium phthalate, sodium phthalate, potassium phthalate and tetrachlorophthalic anhydride); phthalazines (phthalazine, phthalazine derivatives or metal salts; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6 -T-butylphthalazine, 6-chloro (Talazine, 5.7-dimethoxyphthalazine, and 2,3-dihydrophthalazine) are preferable. In particular, in the combination with silver halide having a high silver iodide content, the combination of phthalazine and phthalic acid is preferable.

  The addition amount of phthalazines is preferably 0.01 mol to 0.3 mol, more preferably 0.02 mol to 0.2 mol, and particularly preferably 0.02 mol to 0.00 mol per mol of the organic silver salt. 1 mole. This addition amount is an important factor for promoting development, which is a problem in the silver halide emulsion having a high silver iodide content of the present invention. By selecting an appropriate addition amount, both sufficient developability and low fog are achieved. Is possible.

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

4) Dye, Pigment Various dyes and pigments (for example, CI Pigment Blue 60, CI Pigment, etc.) are used for the image forming layer of the present invention from the viewpoints of improving color tone, preventing interference fringes during laser exposure, and preventing irradiation. 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 according to the invention, it is preferable to add an agent nucleating agent to the image forming layer. Regarding the nucleating agent and the method and amount of addition thereof, JP-A-11-65021, paragraph No. 0118, JP-A-11-223898, paragraphs 0136-0193, JP-A-2001-284399, formula (H) , Compounds of formulas (1) to (3), formulas (A) and (B), compounds of general formulas (III) to (V) described in Japanese Patent Application No. 11-91652 (specific compounds: The nucleation accelerators are described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

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

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution of the present invention is preferably 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 other components)

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

  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 on 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. 2001-348546.

  As the binder for the surface protective layer of the present invention, gelatin is preferable, but it is also preferable to use polyvinyl alcohol (PVA) or a combination thereof. As gelatin, inert gelatin (for example, Nitta gelatin 750), phthalated gelatin (for example, Nitta gelatin 801), and the like can be used.

  Examples of PVA include those described in paragraph Nos. 0009 to 0020 of JP-A No. 2000-171936. Completely saponified PVA-105, partially saponified PVA-205, PVA-335, and modified polyvinyl alcohol MP- Preferred is 203 (trade name, manufactured by Kuraray Co., Ltd.).

Preferably 0.3g / m ² ~4.0g / m ² as a polyvinyl alcohol coating amount (per support 1 m ²⁾ of the protective layer (per one ^{layer), 0.3g / m 2 ~2.0g /} m 2 Is more preferable.

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

2) Antihalation layer In the photothermographic material of the invention, the antihalation layer can be provided on the side farther from the exposure 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 0.2-2. 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 thermal decoloration using such decoloring dyes and base precursors, substances that lower the melting point by 3 ° C. or more when mixed with a base precursor as described in JP-A No. 11-352626 (for example, diphenylsulfone, 4-chlorophenyl, etc.) (Phenyl) sulfone) is preferably used in view of thermal decoloring properties.

3) Back Layer Back layers that can be applied to the present invention are described in paragraph numbers 0128 to 0130 of JP-A No. 11-65021.

In the present invention, a colorant having an absorption maximum at 300 to 450 nm can be added for the purpose of improving the silver color tone and the temporal change of the image. Such colorants are disclosed in JP-A-62-210458, JP-A-63-104046, JP-A-63-103235, JP-A-63-208846, JP-A-63-306436, JP-A-63-141435, and JP-A-01-61745. And JP-A No. 2001-100363. Such a colorant is usually added in the range of 0.1 mg / m ^{2 to 1} g / m ² , and the back layer provided on the opposite side of the image forming layer is preferable as the layer to be added.

4) Matting agent In the present invention, it is preferable to add a matting agent to the surface protective layer and the back layer in order to improve transportability. Matting agents are described in JP-A No. 11-65021, paragraph numbers 0126 to 0127.
Matting agent case shown in the coating amount per photothermographic material 1 m ^2, preferably from ^{1mg / m 2 ~400mg / m 2} , more preferably ^{5mg / m 2 ~300mg / m 2} .

  Further, the degree of matting of the image forming layer surface may be any as long as so-called stardust failure in which small white spots occur in the image portion and light leakage occurs, but the Beck smoothness is preferably 30 seconds or more and 2000 seconds or less, In particular, it is preferably 40 seconds or more and 1500 seconds or less. The Beck smoothness can be easily obtained 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, the layer functioning as the outermost surface layer of the photothermographic material, 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

5) Polymer latex A polymer latex can be added to the surface protective layer or the back layer of the present invention.
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 Ethylhexyl acrylate (25.4 weight%) / styrene (8
. 6 mass%) / 2-hydroxyethyl methacrylate (5.1 mass%) / acrylic acid (2.0 mass%) copolymer latex, methyl methacrylate (64.0 mass%) / styrene (9.0 mass%) / Examples include latex of butyl acrylate (20.0 mass%) / 2-hydroxyethyl methacrylate (5.0 mass%) / acrylic acid (2.0 mass%) copolymer.

  The polymer latex is preferably used in an amount of 10% by mass to 90% by mass, particularly preferably 20% by mass to 80% by mass, based on the total binder (including the water-soluble polymer and latex polymer) of the surface protective layer or the back layer.

6) Membrane 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.

  For the adjustment of the film surface pH, it is preferable to use an organic acid such as a phthalic acid derivative, a non-volatile acid such as sulfuric acid, and 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 thermal 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.

7) Hardener A hardener may be used for each layer such as the image forming layer, protective layer, and back layer of the present invention.
Examples of hardeners include T.W. H. There are various methods described in "THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION" by James (published by Macmillan Publishing Co., Inc., published in 1977), pages 77 to 87, Chrome Alum, 2,4-dichloro-6 In addition to hydroxy-s-triazine sodium salt, N, N-ethylenebis (vinylsulfonacetamide), N, N-propylenebis (vinylsulfonacetamide), polyvalent metal ions described on page 78 of the same document, US Pat. No. 4,281 , 060, and JP-A-6-208193, epoxy compounds such as US Pat. No. 4,791,042, and vinyl sulfone compounds such as JP-A-62-89048 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.

8) Surfactant Surfactants applicable to the present invention are described in paragraph No. 0132 of JP-A No. 11-65021.
In the present invention, it is preferable to use a fluorochemical surfactant. Preferable 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 present invention, the use of a fluorosurfactant described in JP-A-2000-206560 is particularly preferred.

9) Antistatic agent In the present invention, an antistatic layer containing various known metal oxides or conductive polymers may be provided. The antistatic layer may also serve as the above-described undercoat layer, back layer surface protective layer, or the like, or may be provided separately. Regarding the antistatic layer, paragraph No. 0135 of JP-A No. 11-65021, paragraphs of JP-A Nos. 56-143430, 56-143431, 58-62646, No. 56-120519, and paragraphs of JP-A No. 11-84573. The techniques described in Paragraph Nos. 0078 to 0084 of Nos. 0040 to 0051, US Pat. No. 5,575,957 and JP-A-11-223898 can be applied.

10) Support The transparent support is subjected to heat treatment in a temperature range of 130 ° C to 185 ° C in order to relieve 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.

  PEN can be preferably used as a support for a thermosensitive material used in combination with an ultraviolet light emitting screen. However, it is not limited to this. PEN is preferably polyethylene-2,6-naphthalate. The polyethylene-2,6-naphthalate referred to in the present invention is not limited as long as the repeating structural unit is substantially composed of an ethylene-2,6-naphthalenedicarboxylate unit. 6-naphthalene dicarboxylate as well as copolymers in which not more than 10%, preferably not more than 5% of the number of repeating structural units are modified with other components, and mixtures and compositions with other polymers. It is a waste.

Polyethylene-2,6-naphthalate is synthesized by combining naphthalene-2,6-dicarboxylic acid, or a functional derivative thereof, and ethylene glycol or a functional derivative thereof in the presence of a catalyst under suitable reaction conditions. However, one or more appropriate third components (modifiers) are added to the polyethylene-2,6-naphthalate referred to in the present invention before the completion of polymerization of the polyethylene-2,6-naphthalate. Copolymerized or mixed polyester may be used. Suitable third components include compounds having a divalent ester-forming functional group, such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,7-dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid Dicarboxylic acids such as, lower alkyl esters thereof, oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid, or lower alkyl esters thereof, and dihydric alcohols such as propylene glycol and trimethylene glycol, etc. Compounds.
Polyethylene-2,6-naphthalate or a modified polymer thereof is obtained by blocking a terminal hydroxyl group and / or carboxyl group with a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, and methoxypolyalkylene glycol. Alternatively, it may be modified with a very small amount of a trifunctional or tetrafunctional ester-forming compound such as glycerin or pentaerythritol so long as a substantially linear copolymer is obtained. "

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.
Specific examples of the support are described in paragraph No. 0134 of JP-A No. 11-65021.

  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.

11) Other additives An antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber or a coating aid may be further added to the photothermographic material. A solvent described in paragraph No. 0133 of JP-A No. 11-65021 may be added. 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.

12) 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. Extrusion coating or slide coating described in pages 399 to 536 is preferably used, particularly preferably slide coating, by Schweizer, “LIQUID FILM COATING” (CHAPMAN & HALL, 1997).

  An example of the shape of a slide coater used for slide coating is shown in FIG. 11b. 1 If desired, two or more layers can be simultaneously coated by the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761,791 and British Patent No. 837,095. .

The organic silver salt-containing layer coating solution in the present invention is preferably a so-called thixotropic fluid. Regarding this technique, JP-A-11-52509 can be referred to.
The viscosity of the organic silver salt-containing layer coating solution in the present invention 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, at a shear rate of 0.1 S ⁻¹ .
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.

13) Packaging material The photothermographic material of the present invention is used to prevent deterioration of photographic performance during storage before use, or to prevent curling or curling in the case of a rolled product form. It is preferable to hermetically package with a packaging material having low oxygen permeability and / or moisture permeability. The oxygen permeability is preferably 50 ml / atm / m ² · day or less at 25 ° C., more preferably 10 ml / atm / m ² · day or less, and even more preferably 1.0 ml / atm / m ² · day. day or less. The moisture permeability is preferably 10 g / atm / m ² · day or less, more preferably 5 g / atm / m ² · day or less, and further preferably 1 g / atm / m ² · day or less. As specific examples of the packaging material having low oxygen permeability and / or moisture permeability, those described in, for example, JP-A-8-254793 and JP-A-2000-206653 can be used.

14) 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, JP 2000-187298 2001-2004414, 2001-234635, 2002-020699, 2001-275471, 2001-275461, 2000-313204, 2001-292844, 2000-324888, JP-A-2001-293864 and JP-A-2001-348546 are also included.

15) Color imaging The composition of a multicolor photothermographic material may include a combination of these two layers for each color, and within a single layer as described in US Pat. No. 4,708,928. May contain all the components.
In the case of a multicolor color photothermographic material, each image forming layer is generally a functional or non-functional barrier between each image forming layer as described in US Pat. No. 4,460,681. By using layers, they are kept distinct from each other.

2. Image forming method 2-1. Exposure The photothermographic material of the present invention may be a “single-sided type” having an image forming layer only on one side of a support or a double-sided type having image forming layers on both sides.
<Double-sided photothermographic material>
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.
(A) obtaining the image forming assembly by installing the photothermographic material between a pair of fluorescent intensifying screens;
(B) placing a subject between the assembly and the X-ray source;
(C) irradiating the subject with X-rays having an energy level in the range of 25 kVp to 125 kVp;
(D) removing the photothermographic material from the assembly;
(E) A step of heating the photothermographic material taken out at a temperature in the range of 90 ° C to 180 ° C.

  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.

  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 surface 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 present invention, preferred phosphors include those shown below. Tungstate phosphors (CaWO ₄ , MgWO ₄ , CaWO ₄ : Pb, etc.), terbium activated rare earth oxysulfide phosphors [Y ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Tb, La ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Tb, (Y, Gd) O ₂ S: Tb, Tm, etc.], terbium-activated rare earth phosphate phosphors (YPO ₄ : Tb, GdPO ₄ : Tb, LaPO ₄ : Tb, etc.), terbium activated rare earth oxyhalide phosphors (LaOBr: Tb, LaOBr: Tb, Tm, LaOCl: Tb, LaOCl: Tb, Tm, LaOBr: Tb, GdOBr: Tb, GdOCl: Tb, etc.) , Thulium activated rare earth oxyhalide phosphors (LaOBr: Tm, LaOCl: Tm, etc.), barium sulfate phosphors [BaSO ₄ : Pb, BaSO ₄ : Eu ²⁺ , (Ba , Sr) SO ₄ : Eu ²⁺ etc.], divalent europium activated alkaline earth metal phosphate phosphor [(Ba ₂ PO ₄ ) ₂ : Eu ²⁺ , (Ba ₂ PO ₄ ) ₂ : Eu ²⁺ Etc.] Divalent europium activated alkaline earth metal fluoride halide phosphor [BaFCl: Eu ²⁺ , BaFBr: Eu ²⁺ , BaFCl: Eu ²⁺ , Tb, BaFBr: Eu ²⁺ , Tb, BaF ₂ BaCl · KCl: Eu ²⁺ , (Ba, Mg) F ₂ .BaCl · KCl: Eu ²⁺ etc.], iodide phosphors (CsI: Na, CsI: Tl, NaI, KI: Tl etc.), sulfide Physical phosphors [ZnS: Ag (Zn, Cd) S: Ag, (Zn, Cd) S: Cu, (Zn, Cd) S: Cu, Al, etc.], hafnium phosphate phosphors (HfP ₂ O ₇ : Cu, etc.), was also added various activator as YTaO ₄ and the light emission center to it . However, the phosphor used in the present invention is not limited to these, and any phosphor that emits light in the visible or near ultraviolet region when irradiated with radiation can be used.

  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.

<Single-sided photothermographic material>
The single-sided photothermographic material of the present invention is particularly preferably used as a mammographic X-ray photosensitive material.
In the single-sided photothermographic material used for this purpose, it is important to design the contrast of the obtained image within an appropriate range.

  With respect to preferable constitutional requirements as an X-ray photosensitive material for mammography, the descriptions in JP-A-5-45807, JP-A-10-62881, JP-A-10-54900, and JP-A-11-109564 can be referred to. .

<Combination with ultraviolet fluorescent screen>
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.

2-2. Thermal 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 a method described in JP-A-11-133572. The heat development photosensitive material on which a latent image is formed is brought into contact with a heating means in a heat development part, and heat for obtaining 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.

  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.

2-3. System Fuji Medical Dry Imager-FM-DPL can be mentioned as a medical laser imager provided with an exposure unit and a thermal development unit. The system is Fuji Medical Review No. 8, pages 39 to 55, and these techniques can be used. Further, it can also be applied as a photothermographic material for a laser imager in “AD network” proposed by Fuji Medical Co., Ltd. as a network system conforming to the DICOM standard.

3. Use of the present invention The photothermographic material using the high silver iodide photographic emulsion of the present invention forms a black and white image by a silver image, and is used for medical diagnosis, photothermographic material for industrial photography, and printing. It is preferably used as a photothermographic material or a photothermographic material for COM.

  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 Treatment Both surfaces of the support were treated at room temperature at 20 m / min using a solid state corona treatment machine 6KVA model manufactured by Pillar. 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 A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Bailonal MD-1200 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
MP-1000 (PMMA polymer fine particles, average particle size 0.4 μm) manufactured by Soken Chemical Co., Ltd.
0.91g
931 ml of distilled water

After both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm are subjected to the corona discharge treatment, the undercoat coating solution formulation (1) is applied with a wire bar to a wet coating amount of 6.6 ml / m ² (single side And then 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) Silver halide emulsion (Preparation of silver halide emulsion A)
-Particle formation process-
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, 30.5 g of phthalated gelatin, and 5 mass of 2,2 ′-(ethylenedithio) diethanol. The solution to which 160 ml of a methanol solution was added was maintained in a stainless steel reaction vessel while maintaining the liquid temperature at 75 ° C., and 222.22 g of silver nitrate was added with distilled water and diluted to 218 ml with potassium iodide 36. 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.

The obtained silver halide emulsion is a pure silver iodide emulsion having an average projected area diameter of 0.91 μm, an average projected area diameter variation coefficient of 17.7%, an average thickness of 0.060 μm, and an average aspect ratio of 16.3. Tabular grains accounted for over 80% of the total projected area. The equivalent sphere diameter was 0.45 μm.
As a result of analysis by X-ray powder diffraction analysis, 30% of silver iodide was present in the γ phase.

-Formation of epitaxial junctions-
One mole of tabular grain AgI emulsion prepared with silver halide emulsion A was placed in a reaction vessel. The pAg was 10.2 measured at 38 ° C. Then, by double jet addition, a 0.5 mol / liter 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. Epitaxially precipitated on the emulsion. 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.

<< Preparation of silver halide B >>

-Chemical sensitization process-
The silver halide dispersion was maintained at 38 ° C. with stirring, 5 ml of a 0.34 mass% methanol solution of 1,2-benzisothiazolin-3-one was added, and the temperature was raised to 60 ° C. after 40 minutes. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ moles per 1 mole of silver, and 5 minutes later, tellurium sensitizer C was added in a methanol solution at a rate of 2. per mol of silver. 9 × 10 ⁻⁵ mol was added and aged for 90 minutes. Thereafter, 1.3 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ -diethylmelamine was added, and after 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the methanol solution per mole of silver. 4.8 × 10 ⁻³ mol, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole was added in methanol solution to 5.4 × 10 ⁻³ mol and 1- ( 3-methylureidophenyl) -5-mercaptotetrazole was added in an aqueous solution to 8.5 × 10 ⁻³ mol per mol of silver.

<< Preparation of silver halide emulsion C >>
In the same manner as in the preparation of silver halide emulsion B, after grain formation and epitaxial junction formation, 1 × 10 ⁻³ mol of potassium thiocyanate was added to 1 mol of silver just before the tellurium sensitizer was added. A chemical sensitization process was performed. The aging time was adjusted to be optimal.
<< Preparation of silver halide emulsion D >>
Under the chemical sensitization conditions of the silver halide emulsion B, 5 × 10 ⁻² mol of potassium thiocyanate was added to 1 mol of silver immediately before the tellurium sensitizer was added. The aging time was adjusted to be optimal.

<< Preparation of silver halide emulsion E >>
After the formation of grains and the formation of an epitaxial junction in the same manner as in the preparation of silver halide B, an aqueous solution of sodium thiosulfate was used instead of methanol solution of tellurium sensitizer C at 6.5 per mol of silver halide. Silver halide E was prepared in the same manner as silver halide emulsion B except that the amount was changed to × 10 ^-5 mol.

<< Preparation of silver halide emulsion F >>
After the formation of grains and the formation of an epitaxial junction in the same manner as the preparation of silver halide C, an aqueous solution of sodium thiosulfate was used instead of the tellurium sensitizer C in methanol solution at 6.5 per mol of silver halide. × 10 ^-5 mol was added.

<< Preparation of silver halide emulsion G >>
After the formation of grains and the formation of an epitaxial junction in the same manner as the preparation of silver halide D, an aqueous solution of sodium thiosulfate was used instead of the tellurium sensitizer C in methanol solution at 6.5 per mol of silver halide. × 10 ^-5 mol was added.
<< Preparation of silver halide emulsion H >>
After the formation of grains and the formation of an epitaxial junction in the same manner as the preparation of silver halide B, an aqueous solution of sodium thiosulfate was used instead of the tellurium sensitizer C in methanol solution at 6.5 per mole of silver halide. × 10 ^-5 mol and chloroauric acid were added in an amount of 1.2 × 10 ^-6 mol per mol of silver halide.

<< Preparation of silver halide emulsion I >>
After the formation of grains and the formation of an epitaxial junction in the same manner as the preparation of silver halide C, an aqueous solution of sodium thiosulfate was used instead of the tellurium sensitizer C in methanol solution at 6.5 per mol of silver halide. × 10 ^-5 mol and chloroauric acid were added in an amount of 1.2 × 10 ^-6 mol per mol of silver halide.

<< Preparation of silver halide emulsion J >>
After the formation of grains and the formation of an epitaxial junction in the same manner as the preparation of silver halide D, an aqueous solution of sodium thiosulfate was used instead of the tellurium sensitizer C in methanol solution at 6.5 per mol of silver halide. × 10 ^-5 mol and chloroauric acid were added in an amount of 1.2 × 10 ^-6 mol per mol of silver halide.
≪Preparation of mixed emulsion for coating liquid≫
After the silver halide emulsions A to J were dissolved at 38 ° C., 7 × 10 ⁻³ mol of silver benzothiazolium iodide was added in a 1% by mass aqueous solution per mol of silver, and then emulsions A, B, E, Divided into 2 for H and 4 for Emulsion I, A, B, E, and H for each, 5.0 × 10 ⁻² mol of potassium thiocyanate solution per mol of silver halide A-1, B-1, E-1, and H-1 were prepared as follows. For I, an aqueous solution of potassium thiocyanate, sodium thiocyanate, and ammonium thiocyanate was added to 1 mol of silver halide. Were added so as to be 4.9 × 10 ⁻² mol, respectively, to obtain I-1, I-2, and I-3. Emulsions to which no thiocyanic acid was added were Emulsions A to J.
Subsequently, the one-electron oxidant produced by one-electron oxidation yields 2 × 10 ⁻³ moles per mole of silver halide of compound compounds 1, 2 and 3 that can emit one electron or more. An amount 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 1 L 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. It was a crystal with a variation coefficient of 11% (a, b, and c are defined in the text).

  19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to a wet cake corresponding to a dry solid content of 260 kg 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 kg of water was added to 16 kg of a 10% by weight aqueous solution of reducing agent-1 (2,2′-methylenebis- (4-ethyl-6-tert-butylphenol)) and denatured polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203). Add and mix well to make 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.
<< Preparation of Reducing Agent-2 Dispersion >>
10 masses of reducing agent-2 (6,6′-di-t-butyl-4,4′-dimethyl-2,2′-butylidenediphenol) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 16 kg of% aqueous solution and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to prepare a reducing agent concentration of 25% by mass. This dispersion was heated at 40 ° C. for 1 hour, and then further heated at 80 ° C. for 1 hour to obtain a reducing agent-2 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.50 μm and a maximum particle diameter of 1.6 μm or less.
The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

4) Preparation of hydrogen bonding compound dispersion << Preparation of hydrogen bonding compound-1 dispersion >>
Add 10 kg of water to 10 kg of 10% aqueous solution of hydrogen bonding compound-1 (tri (4-t-butylphenyl) phosphine oxide) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203). Mix to make 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.

5) Preparation of development accelerator dispersion and color tone modifier dispersion << Preparation of development accelerator-1 dispersion >>
10 kg of development accelerator-1 and 20 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) were added 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.

  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.

6) Preparation of polyhalogen compound dispersion << Preparation of organic polyhalogen compound-1 dispersion >>
10 kg of organic polyhalogen compound-1 (tribromomethanesulfonylbenzene), 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), 0.4 kg of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, Then, 14 kg of water was added and mixed well to obtain a slurry. 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.

<< Preparation of organic polyhalogen compound-2 dispersion >>
10 kg of an organic polyhalogen compound-2 (N-butyl-3-tribromomethanesulfonylbenzoamide), 20 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and 20 of sodium triisopropylnaphthalenesulfonate 0.4 kg of a mass% aqueous solution was added and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to 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.

7) Preparation of silver iodide complex forming agent 8 kg of modified polyvinyl alcohol MP203 was dissolved in 174.57 kg of water, and 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.

8) 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.

9) 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.

10) 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.).

11) Preparation of nucleating agent dispersion Compound No. 1 was used as a nucleating agent. To 7 g of SH-7, 2.5 g of polyvinyl alcohol (Kuraray PVA-217) and 87.5 g of water were added and stirred well, and left as a slurry 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 0.1 μm to 1.0 μm, and the average particle size was 0.5 μm.

3. Preparation of coating solution 1) Preparation of image forming layer coating solutions-1 to 17 276 ml of water was added to 1000 g of the fatty acid silver dispersion obtained above, and the organic polyhalogen compound-1 dispersion and the organic polyhalogen compound-2 dispersion were sequentially added. , SBR latex (TP-1) liquid, isoprene latex (TP-2), reducing agent-1 dispersion, reducing agent-2 dispersion, nucleating agent dispersion, hydrogen bonding compound-1 dispersion, development acceleration Agent-1 Dispersion, Development Accelerator-2 Dispersion, Color Tone Modifier-1 Dispersion, Mercapto Compound-1 Aqueous Solution, and Mercapto Compound-2 Aqueous Solution are sequentially added, and a silver iodide complex forming agent is added. Immediately before coating, a silver halide mixed emulsion for coating solution (shown in Table 1) was added in a silver amount of 0.22 mol per mol of fatty acid silver, mixed well, and fed directly to the coating die.

2) Preparation of image forming layer coating solution-18 to 21 Image forming layer coating solution-18: In preparation of image forming layer coating solution-12, 1 mol of silver halide when potassium thiocyanate was applied to the fatty acid silver dispersion. It added so that it might become ^{4.9x10 -2} mol with respect to this.
Image forming layer coating solution-19: Immediately before the addition of the organic polyhalogen compound-2 in the preparation of the image forming layer coating solution-12, 4.9 × 10 4 with respect to 1 mol of silver halide at the time of coating. ^-2 mol was added.
Image forming layer coating solution -20: In preparation of image forming layer coating solution-12, after addition of isoprene latex (TP-2), potassium thiocyanate is added to 1 mol of silver before addition of reducing agent-1 dispersion. 4.9 × 10 ⁻² mol was added.
Image forming layer coating solution-21: Immediately before the addition of the silver halide mixed emulsion for coating solution in the preparation of image forming layer coating solution-12, 4.9 with respect to 1 mol of silver thiocyanate at the time of coating. × 10 ^-2 mol was added.

3) Preparation of intermediate layer coating solution 1000 g of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer mass ratio 64/9/20 / 5/2) 27% 5% by weight 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, water to a total amount of 10000 g Was added with NaOH so that the pH was 7.5 to obtain an intermediate layer coating solution, and the solution was fed to the coating die so as to be 9.1 ml / m ² .
The viscosity of the coating solution was 58 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

4) Preparation of surface protective layer first layer coating solution 64 g of inert gelatin was dissolved in water and a methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5). / 2) 112 g of latex 19.0 wt% solution, 30 ml of 15 wt% methanol solution of phthalic acid, 23 ml of 10 wt% aqueous solution of 4-methylphthalic acid, 28 ml of 0.5 mol / L sulfuric acid, Aerosol OT (American 5 ml of a 5% by weight aqueous solution (made by Cyanamid), 0.5 g of phenoxyethanol, and 0.1 g of benzoisothiazolinone are added to form a coating solution by adding water to a total amount of 750 g 26 ml of 4% by weight chromium alum consisting of which had been mixed with a static mixer to 18.6ml / m ² to immediately before coating It was fed to a coating die.
The viscosity of the coating solution was 20 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

5) Preparation of surface protective layer second layer coating solution 80 g of inert gelatin was dissolved in water, and methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5). / 2) 102 g of latex 27.5% by mass solution, 5.4 ml of 2% by mass solution of fluorosurfactant (F-1), and 5% by mass of 2% by mass aqueous solution of fluorosurfactant (F-2). 4 ml, 23 ml of a 5% by mass solution of aerosol OT (manufactured by American Cyanamid), 4 g of polymethyl methacrylate fine particles (average particle size 0.7 μm, volume weighted average distribution 30%), polymethyl methacrylate fine particles (average particle) Diameter 3.6 μm, volume weighted average distribution 60%) 21 g, 4-methylphthalic acid 1.6 g, phthalic acid 4.8 g, 0.5 mol / L concentration Water was added to 44 ml of sulfuric acid and 10 mg of benzoisothiazolinone to a total amount of 650 g, and 445 ml of an aqueous solution containing 4% by weight chromium alum and 0.67% by weight phthalic acid was mixed with a static mixer immediately before coating. The resulting solution was used as a surface protective layer coating solution and fed to a 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). Preparation of coated sample 4-1. Preparation of photothermographic material

A sample of a photothermographic material was prepared by simultaneously applying an image forming layer, an intermediate layer, a surface protective layer first layer, and a surface protective layer second layer in this order from the undercoat surface by a slide bead coating 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 0.865 g / m ² per side in total of fatty acid silver and silver halide. This was applied to both sides of the support.

The coating amount (g / m ² ) per side of each compound in the image forming layer is as follows.
Fatty acid silver (as silver) 0.69
Polyhalogen compound-1 0.028
Polyhalogen compound-2 0.094
Silver iodide complex forming agent 0.46
SBR latex 2.08
Isoprene Latex 3.12
Reducing agent-1 0.33
Reducing agent-2 0.13
Nucleating agent 0.036
Hydrogen bonding compound-1 0.15
Development accelerator-1 0.001
Development accelerator-2 0.009
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. Performance Evaluation 1) Preparation The obtained samples were 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>
A 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) Image exposure and thermal development Two fluorescent intensifying screens A described below were used, and a sample was sandwiched between them to produce an image forming assembly. 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 processing was performed under the heat development processing conditions by the heat development apparatus according to the present invention. The obtained image was evaluated with a densitometer.

<Preparation of fluorescent intensifying screen A>
(1) Preparation of undercoat layer In the same manner as in Example 4 of JP-A-2001-124898, a light-reflective layer having a dried film thickness of 50 μm made of alumina powder on a 250 μm polyethylene terephthalate (support). Formed.

(2) Production of phosphor sheet BaFBr: Eu phosphor (average particle size 3.5 μm) 250 g, polyurethane binder resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: Pandex T5265M), epoxy binder 2 g of resin (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 1001) and 0.5 g of isocyanate compound (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) are added to methyl ethyl ketone and dispersed with a propeller mixer. Thus, 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 phosphor sheet is overlaid 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 applied with a calendar roll. Pressurization was performed under the conditions of 400 kgw / cm ² and a temperature of 80 ° C., and a phosphor layer was provided 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 emission spectrum of the intensifying screen A measured with X-rays of 40 kVp is shown in FIG. The fluorescent intensifying screen A emitted light with a narrow half-value width having a peak at 390 nm.

  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. Furthermore, the conveyance speed was increased and set to a total of 14 seconds.

3) Evaluation of photographic performance Fog: The density of the unexposed area was defined as fog.
Sensitivity (S): The reciprocal of the exposure amount necessary to obtain a density of 1.0 is shown as sensitivity, and the sensitivity of sample 1 is shown as 100, which is shown as a relative value.
4) Evaluation of raw storage stability Storage stability until sample formation after sample preparation was evaluated under the following forced test conditions.
In the above packaging state, it was stored at 40 ° C for 8 weeks. Then, it returned to room temperature and opened, and photograph performance was investigated.
The fogging change (Δfog) and the sensitivity change (ΔS) are increments under forced conditions, respectively. The smaller the absolute value of both Δfog and ΔS, the smaller the change and the greater the stability.

5) Evaluation results The results are shown in Table 1. The sample of the present invention had a low fog, high sensitivity, and excellent raw storage. That is, the addition of thiocyanate in the present invention hardly increases the sensitivity, but suppresses the increase in fog and improves the storage stability. In addition, when thiocyanic acid is added during chemical sensitization, although an increase in sensitivity may be seen, the effect of the present invention is hardly seen, or conversely, the epitaxial portion is deformed and lowered in sensitivity. In spite of this, in the present invention, the effect of improving the storage stability was obtained while maintaining high sensitivity. Such an effect of thiocyanate is a new effect that cannot be predicted from the conventional knowledge.

Example 2
1. Preparation of undercoat support 1) Preparation formulation a of undercoat layer coating solution (for undercoat layer on photosensitive layer side)
46.8 g of pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Toyobo Co., Ltd. made baironal WD-1200 10.4g
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 1% by mass solution 11.0 g
MP-1000 manufactured by Soken Chemical Co., Ltd. (PMMA polymer fine particles, average particle size 0.4 μm)
0.91g
931 ml of distilled water

Formulation b (for back layer 1st layer)
Styrene-butadiene copolymer latex 130.8 g
(Solid content 40% by mass, styrene / butadiene weight ratio = 68/32)
2,4-Dichloro-6-hydroxy-S-triazine sodium salt (8% by mass aqueous solution) 5.2 g
10% 1% by weight aqueous solution of sodium laurylbenzenesulfonate
Polystyrene particle dispersion (average particle size 2 μm, 20 mass%) 0.5 g
854 ml of distilled water

Formulation c (for back side second layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.5 μm, 17 mass% dispersion)
84g
Gelatin 7.9g
10g Metros TC-5 (2 mass% aqueous solution) manufactured by Shin-Etsu Chemical Co., Ltd.
10% 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 7g
Proxel (Abyssia) 0.5g
Distilled water 881ml

After both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm are subjected to the corona discharge treatment, the undercoat coating solution formulation a is applied to one side with a wire bar at a wet coating amount of 6.6 ml / m ² (single side And then dried at 180 ° C. for 5 minutes, and then the above-mentioned undercoat coating liquid formulation b was applied to the back surface with a wire bar so that the wet coating amount was 5.7 ml / m ² . Dry at 5 ° C. for 5 minutes, and further apply the above-mentioned undercoat coating liquid formulation c on the back surface with a wire bar so that the wet coating amount is 8.4 ml / m ^2, and dry at 180 ° C. for 6 minutes. Produced.

2. Back layer

1) Preparation of antihalation layer coating solution 32.7 g of lime-processed gelatin in water kept at 40 ° C., 0.77 g of monodisperse polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4 μm), benzoisothiazo 0.08 g of linone, 0.3 g of sodium polystyrene sulfonate, 0.06 g of blue dye compound-1 and 1.5 g of ultraviolet light absorber-1, acrylic acid / ethyl acrylate copolymer latex (copolymerization ratio 5/95) 5.0 g, 1.7 g of N, N-ethylenebis (vinylsulfoneacetamide) are mixed, the pH is adjusted to 6.0 with 1 mol / L sodium hydroxide, and the whole is made up to 818 ml with water. A coating solution was prepared.

2) Preparation of back surface protective layer coating solution 66.5 g of lime-treated gelatin in water kept at 40 ° C., 5.4 g of liquid paraffin emulsion as liquid paraffin, 0.10 g of benzoisothiazolinone, disulfosuccinate (2- Ethylhexyl) sodium 0.5 g, polystyrene sulfonate sodium 0.27 g, fluorosurfactant (F-1) 2 mass% aqueous solution 13.6 ml, acrylic acid / ethyl acrylate copolymer (copolymerization weight ratio 5/95 ) 10.0 g was mixed, pH was adjusted to 6.0 with 1 mol / L sodium hydroxide, and the volume was adjusted to 1000 ml with water to obtain a back surface protective layer coating solution.
3) Coating On the back surface side of the undercoat support, the antihalation layer coating solution was applied to a gelatin coating amount of 1.70 g / m ^2, and the back surface protective layer coating solution was applied to a gelatin coating amount of 0.79 g / m ^2. A multilayer was simultaneously applied so as to be m ² and dried to produce a back layer.

3. 3. Image forming layer, intermediate layer, and surface protective layer 3-1. Preparation of coating materials 1) Preparation of silver halide emulsion <Preparation of silver halide emulsion 1>
To a solution of 1420 ml of distilled water was added 4.3 ml of a 1% by weight potassium iodide solution, and a solution containing 3.5 ml of 0.5 mol / L sulfuric acid and 36.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 42 ° C., a solution A in which distilled water was diluted to 22.56 g of silver nitrate and diluted to 195.6 ml and solution B in which 21.8 g of potassium iodide was diluted with distilled water to a volume of 218 ml were added at a constant flow rate. The whole amount was added over 9 minutes. 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, Solution C obtained by adding distilled water to 51.86 g of silver nitrate and diluting to 317.5 ml and Solution D obtained by diluting 60 g of potassium iodide to a volume of 600 ml with distilled water were added to Solution C over 120 minutes at a constant flow rate. Solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so 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 8.0.

The silver halide dispersion was maintained at 38 ° C. with stirring, 5 ml of a 0.34 mass% 1,2-benzisothiazolin-3-one methanol solution was added, and the temperature was raised to 47 ° C. 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 further 5 minutes later, tellurium sensitizer B was added in a methanol solution to a ratio of 2. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes.
Add 1.3 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″, N ″ -diethylmelamine, and after 4 minutes, add 1 mol of 5-methyl-2-mercaptobenzimidazole with a methanol solution. 4.8 × 10 ⁻³ mol per 1 mol and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole was added in a methanol solution to 5.4 × 10 ⁻³ mol with respect to 1 mol of silver. A silver halide emulsion 1 was prepared.

  The grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 0.040 μm and a sphere equivalent diameter variation coefficient of 18%. Moreover, it is a tetrahedral particle | grain which has (001), {100}, {101} face, The ratio of the (gamma) phase was 30% when measured using the X-ray powder diffraction analysis. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<Preparation of silver halide emulsion 2>
The temperature of the reaction solution was changed to 65 ° C., 5 ml of a 5% methanol solution of 2,2 ′-(ethylenedithio) diethanol was added after the addition of solutions A and B, and solution D while maintaining pAg at 10.5. Was added by the controlled double jet method, and 3 minutes after addition of the tellurium sensitizer at the time of chemical sensitization, 5 × 10 ⁻⁴ mol of bromide acid per mol of silver and 2 thiocyanate potassium per mol of silver A silver halide emulsion 2 was prepared in the same manner as Emulsion 1 except that x10 ^-3 mol was added.
Grains in the prepared silver halide emulsion have an average equivalent circle diameter of projected area of 0.164 μm, a grain thickness of 0.032 μm, an average aspect ratio of 5, an average sphere equivalent diameter of 0.11 μm, and a coefficient of variation of the equivalent sphere diameter of 23. % Pure silver iodide tabular grains. When measured using X-ray powder diffraction analysis, the proportion of the γ phase was 80%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<Preparation of silver halide emulsion 3>
Silver halide emulsion 3 in exactly the same manner as silver halide emulsion 1 except that the temperature of the reaction solution was changed to 27 ° C. and solution D was added by the controlled double jet method while maintaining pAg at 10.2. Was made.
The grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 0.022 μm and a sphere equivalent diameter variation coefficient of 17%. Further, they were dodecahedron grains having (001), {1 (-1) 0}, and {101} planes, and were silver iodide substantially consisting of a β phase as measured by X-ray powder diffraction analysis. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

In the silver halide emulsions 1, 2 and 3, silver halide emulsion 1 was similarly prepared except that an aqueous potassium thiocyanate solution was added so as to be 5 × 10 ⁻² mol per mol of silver before adding the tellurium sensitizer. Made '2', 3 '

<Preparation of mixed emulsion K for coating solution>
Silver halide emulsion 1, silver halide emulsion 2 and silver halide emulsion 3 are dissolved in a molar ratio of 5: 2: 3, and 1 mol of benzothiazolium iodide is added in a 1% by mass aqueous solution. 7 × 10 ⁻³ mol was added per unit.
Subsequently, the one-electron oxidant produced by one-electron oxidation yields 2 × 10 ⁻³ moles per mole of silver halide of compound compounds 1, 2 and 3 that can emit one electron or more. An amount was added.
Further, compounds 1 and 2 having an adsorbing group and a reducing group were added in amounts of 8 × 10 ⁻³ mol per mol of silver halide, respectively. Further, water was added so that the silver halide content per 1 L of the mixed emulsion for coating solution was 15.6 g as silver.

<Preparation of mixed emulsion L for coating solution>
A coating station mixed emulsion L was prepared in the same manner as the coating solution mixed emulsion K except that the silver halides 1, 2, and 3 were changed to silver halide emulsions 1 ′, 2 ′, and 3 ′, respectively.

<Preparation of mixed emulsion M for coating solution>
A mixed emulsion L for coating station was prepared in the same manner as mixed emulsion K for coating solution except that 5 × 10 ^{−2 of} potassium thiocyanate was added before addition of compound 1.

3-2. Preparation of Coating Sample 1) Preparation of Image Forming Layer Coating Solution An image forming layer coating solution was prepared using the mixed emulsion K or L for coating solution instead of the photosensitive silver halide emulsion A as in Example 1. (Shown in Table 2). Sample 24 5 × 10 ^-2 adding potassium thiocyanate at fatty acid silver salt prepared, samples 25 to 27 is a sample of potassium thiocyanate 5 × 10 ^-2 added at preparing the coating liquid, respectively, the organic polyhalogen Potassium thiocyanate was added immediately before the addition of the compound, immediately before the addition of isoprene latex (TP-2), and immediately before the addition of the silver halide mixed emulsion for coating solution.
2) Application On the surface opposite to the back surface, the image forming layer, the same intermediate layer as in Example 1, the surface protective first layer, and the surface protective second layer were applied to prepare a single-side coated sample.
The coating amount (g / m ² ) of each compound in the image forming layer is as follows.

Fatty acid silver 5.42
Polyhalogen compound-1 0.12
Polyhalogen compound-2 0.25
Silver iodide complex forming agent 0.92
SBR latex 3.23
Isoprene latex 6.47
Reducing agent-1 0.40
Reducing agent-2 0.40
Hydrogen bonding compound-1 0.58
Development accelerator-1 0.019
Development accelerator-2 0.016
Mercapto Compound-1 0.002
Mercapto compound-2 0.012
Silver halide (as Ag) 0.10

4). Performance Evaluation 1) Image exposure and heat development Each sample was mounted with a NLHV3000E semiconductor laser from Nichia Corporation as a semiconductor laser light source on the exposure part of the dry film imager DRYPIX7000 of FUJIFILM Medical Co., Ltd., and the beam diameter was reduced to 100 μm. . The illuminance on the photothermographic material surface of the laser light was exposed at 10 ^-5 seconds varied between 0 and ^{1mW / mm 2 ~1000mW / mm 2} . The oscillation wavelength of the laser beam was 405 nm. In the heat development, three panel heaters were set at 107 ° C.-121 ° C.-121 ° C. and developed so that the total time was 14 seconds.

2) Evaluation results Table 2 shows the results evaluated in the same manner as in Example 1. The sample of the present invention showed excellent performance as in Example 1. Sample No. In No. 22, an increase in the grain size of silver halide was observed.

Example 3
1. Preparation of materials 1-1. Crossover cut layer (preparation of solid fine particle dispersion (a) of base precursor)
2.5 kg of the base precursor compound 1 and 300 g of a surfactant (trade name: Demol N, manufactured by Kao Corporation), 800 g of diphenylsulfone, 1.0 g of benzoisothiazolinone sodium salt and distilled water were added to make a total amount of 8 Then, the mixture was dispersed with beads using a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.). In the dispersion method, the mixed solution was fed to UVM-2 filled with zirconia beads having an average diameter of 0.5 mm by a diaphragm pump, and dispersed at an internal pressure of 50 hPa or more until a desired average particle size was obtained. The dispersion was subjected to spectral absorption measurement, and the ratio of the absorbance at 450 nm to the absorbance at 650 nm (D ₄₅₀ / D ₆₅₀ ) in the spectral absorption of the dispersion was dispersed to 3.0. The obtained dispersion was diluted with distilled water so that the concentration of the base precursor was 25% by weight, and was filtered for removal of dust (filter made of polypropylene having an average pore size of 3 μm) for practical use.

(Preparation of ortho heat decoloring dye solid fine particle dispersion)
6.0 kg of ortho heat decoloring dye-1 (λmax = 566 nm) described in JP-A No. 11-231457, 3.0 kg of sodium p-dodecylbenzenesulfonate, 0.6 kg of surfactant Demol SNB manufactured by Kao Corporation, and 0.15 kg of an antifoaming agent (trade name: Surfynol 104E, manufactured by Nissin Chemical Co., Ltd.) was mixed with distilled water to make a total liquid volume of 60 kg. The mixed solution was dispersed with 0.5 mm zirconia beads using a horizontal sand mill (UVM-2: manufactured by Imex Corporation). The dispersion was dispersed until the ratio of the absorbance at 650 nm to the absorbance at 750 nm (D ₆₅₀ / D ₇₅₀ ) in the spectral absorption of the dispersion was 5.0 or more. The obtained dispersion was diluted with distilled water so that the concentration of the cyanine dye was 6% by mass, and subjected to filter filtration (average pore size: 1 μm) for removing dust.

(Preparation of crossover cut layer coating solution)
Polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.) 17 g, polyacrylamide 9.6 g, base precursor solid fine particle dispersion (a) 70 g, ortho dye solid fine particle dispersion (dye solid content 3 mass%) 56 g, benzo A crossover cut layer coating solution was prepared by mixing 0.03 g of isothiazolinone, 2.2 g of sodium polyethylene sulfonate, and 844 ml of water.

1-2. Image forming layer 1) Preparation of silver halide emulsion N A tabular emulsion of silver bromide was prepared.
(Particle formation)
1178 ml of an aqueous solution containing 0.8 g of KBr and 3.2 g of oxidized gelatin having an average molecular weight of 20000 was kept at 35 ° C. and stirred. Each aqueous solution of 1.6 g of silver nitrate, 1.16 g of KBr, and 1.1 g of oxidized gelatin having an average molecular weight of 20000 was added over 45 seconds by the triple jet method. The concentration of silver nitrate was 0.3 mol / L. Thereafter, the temperature was raised to 76 ° C. over 20 minutes, and 26 g of succinylated gelatin having an average molecular weight of 100,000 was added. A silver nitrate 209 g aqueous solution and a KBr aqueous solution were added over 75 minutes while accelerating the flow rate by a control double jet method while maintaining pAg 8.0. Gelatin having an average molecular weight of 100,000 was added and then desalted according to a conventional method. Thereafter, gelatin having an average molecular weight of 100,000 was added and dispersed, and adjusted to pH 5.8 and pAg 8.0 at 40 ° C. The obtained emulsion contained 1 mol of silver and 40 g of gelatin per 1 kg of the emulsion.

(Chemical sensitization)
Each of the emulsions prepared as described above was chemically sensitized while being kept at 56 ° C. with stirring. First, 10 ⁻⁴ mol of the following thiosulfonic acid compound-1 was added per mol of silver halide, and then 0.03 μm of AgI grains were added in an amount of 0.15 mol% based on the total silver amount. Three minutes later, 1 × 10 ⁻⁶ mol / Ag mol of thiourea dioxide was added and held for 22 minutes for reduction sensitization. Next, 4-hydroxy-6-6-methyl-1,3,3a, 7-tetrazaindene is added in an amount equivalent to 3 × 10 ⁻⁴ mol per mol of silver halide to sensitize sensitizing dye-3. 1 × 10 ⁻³ mol equivalent per 1 mol of silver and 1 × 10 ⁻⁴ mol equivalent of sensitizing dyes-1 and 2 were added, and calcium chloride was further added.

Subsequently, after the silver halide per mole 6 × 10 ^-6 mol equivalent selenium compound-1 sodium thiosulfate was added 4 × 10 ^-6 mol equivalent per 1 mol of silver halide, the silver halide of chloroauric acid 2 × 10 ⁻³ mole equivalent was added per mole. Further, 67 mg of a nucleic acid (trade name RNA-F, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) was added per mole of silver halide. After 40 minutes, 1 × 10 ⁻⁴ mole equivalent of water-soluble mercapto compound-1 was added per mole of silver halide and cooled to 35 ° C. Thus, chemical sensitization of emulsion N was completed.

(Shape of the obtained particles)
The obtained silver bromide tabular grains had an average projected area equivalent diameter of 1.117 μm, an average sphere equivalent diameter of 0.472 μm, an average thickness of 0.056 μm, and an average aspect ratio of 19.9 from electron microscope observation. The interparticle variation coefficient of the average projected area equivalent diameter was 23%.

2) Preparation of silver halide emulsion O A silver halide emulsion O was prepared in the same manner as in the preparation of silver halide emulsion N described above except that the chemical sensitization step was changed to the following conditions.
Chemical sensitization conditions: Under the chemical sensitization conditions of silver halide emulsion N, potassium thiocyanate was added in an amount of 5 × 10 ^-5 mol per mol of silver immediately before addition of sensitizing dye-3.

3) Preparation of silver halide emulsion P Silver halide emulsion P was prepared in the same manner as in the preparation of silver halide emulsion N described above except that the chemical sensitization step was changed to the following conditions.
Chemical sensitization conditions: Under the chemical sensitization conditions of silver halide emulsion N, potassium thiocyanate was added in an amount of 5 × 10 ⁻⁵ mol per mol of silver immediately after addition of water-soluble mercapto compound-1.

4) Preparation of image forming layer coating solution (1) Preparation of image forming layer coating solutions 31-33 Into 1000 g of fatty acid silver dispersion and 276 ml of water, organic polyhalogen compound-1 dispersion, organic poly Halogen compound-2 dispersion, SBR latex (TP-1) (Tg: 17 ° C.) liquid, isoprene latex (TP-2), reducing agent-1 dispersion, reducing agent-2 dispersion, hydrogen bonding compound-1 Dispersion, development accelerator-1 dispersion, development accelerator-2 dispersion, color tone modifier-1 dispersion, 5-isopropylphthalazine aqueous dispersion, mercapto compound-1 aqueous solution, mercapto compound-2 aqueous solution are sequentially added. Thereafter, immediately before coating, silver halide emulsions N to P of silver halide were added in an amount of 0.22 mol per mol of silver fatty acid, mixed well, and fed to the coating die as it was.

(2) Preparation of Image Forming Layer Coating Solution-34 to 36 Image Formation Layer Coating Solution-34: In Preparation of Image Forming Layer Coating Solution-31, potassium thiocyanate was added to 1 mol of silver halide in the fatty acid silver dispersion. 5 × 10 ⁻² mol was added.
Image forming layer coating solution-35: In the preparation of image forming layer coating solution-31, 5 × 10 ^-2 mol of potassium thiocyanate was added to 1 mol of silver halide immediately before the addition of the organic polyhalogen compound.
Image forming layer coating solution-36: Immediately before the addition of the silver halide mixed emulsion for coating solution in the preparation of image forming layer coating solution-31, 5 × 10 ⁻² mol of potassium thiocyanate was added to 1 mol of silver. .

2. Preparation of coated sample A double-sided coated sample was prepared in the same manner as in Example 1. However, a crossover cut layer was provided between the image forming layer and the support, and Samples 31 to 36 were obtained in the same manner using the image forming layer coating liquids 31 to 36.

The crossover cut layer was applied so that the solid content of the ortho heat decoloring dye was 0.04 g / m ² . The coating amounts of the other layers were the same as in Example 1.
The chemical structures of the compounds used in the examples of the present invention are shown below.

3. Performance Evaluation Example 1 except that X-ray orthoscreen HG-M (using terbium-activated gadolinium oxysulfide phosphor as the phosphor, emission peak wavelength 545 nm) was used as the phosphor screen. Similarly, X-ray exposure and thermal development were performed.

  The crossover was measured in the same manner as in Example 1 of JP-A No. 11-142723 except that the development process was changed to a thermal development process. As a result, the crossover was 7%.

Results evaluated in the same manner as in Example 1 are shown in Table 3.
As a result, the photothermographic material of the present invention had high sensitivity, low fog, and excellent raw storability. However, in contrast to the photothermographic material of Example 1 using silver iodide, the haze after heat development remained high in the silver bromide tabular grains of Example 3.

Example 4
1. Preparation of coated sample A single-side coated sample was prepared in the same manner as in Example 2. However, the following were used for the silver halide emulsion of the back layer and the image forming layer.

(Back layer)
1) Preparation of back layer coating solution (preparation of solid fine particle dispersion (a) of base precursor)
Add 2.5 kg of Base Precursor Compound 1 and 300 g of a surfactant (trade name: Demol N, manufactured by Kao Corporation), 800 g of diphenylsulfone, 1.0 g of benzoisothiazolinone sodium salt and distilled water to make a total amount. The mixture was mixed to 8.0 kg, and the mixed solution was dispersed with beads using a horizontal sand mill (UVM-2: manufactured by Imex Corporation). In the dispersion method, the mixed solution was fed to UVM-2 filled with zirconia beads having an average diameter of 0.5 mm by a diaphragm pump, and dispersed at an internal pressure of 50 hPa or more until a desired average particle size was obtained.
The dispersion was subjected to spectral absorption measurement, and the ratio of the absorbance at 450 nm to the absorbance at 650 nm (D ₄₅₀ / D ₆₅₀ ) in the spectral absorption of the dispersion was dispersed to 3.0. The obtained dispersion was diluted with distilled water so that the concentration of the base precursor was 25% by weight, and was filtered for removal of dust (filter made of polypropylene having an average pore size of 3 μm) for practical use.

2) Preparation of Dye Solid Fine Particle Dispersion 6.0 kg of cyanine dye compound-1 and 3.0 kg of sodium p-dodecylbenzenesulfonate, 0.6 kg of surfactant Demol SNB manufactured by Kao Corporation, and antifoaming agent (trade name) : Surfynol 104E, manufactured by Nissin Chemical Co., Ltd.) 0.15 kg was mixed with distilled water to make a total liquid volume of 60 kg. The mixed solution was dispersed with 0.5 mm zirconia beads using a horizontal sand mill (UVM-2: manufactured by Imex Corporation).
The dispersion was dispersed until the ratio of the absorbance at 650 nm to the absorbance at 750 nm (D ₆₅₀ / D ₇₅₀ ) in the spectral absorption of the dispersion was 5.0 or more. The obtained dispersion was diluted with distilled water so that the concentration of the cyanine dye was 6% by mass, and was subjected to filter filtration (average pore diameter: 1 μm) for removal of dust and put to practical use.

3) Preparation of antihalation layer coating solution Keep container at 40 ° C., gelatin 40 g, monodisperse polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4) 20 g, benzoisothiazolinone 0.1 g, 490 ml of water was added to dissolve the gelatin. Furthermore, 2.3 ml of 1 mol / L sodium hydroxide aqueous solution, 40 g of the dye solid fine particle dispersion, 90 g of the solid fine particle dispersion (a) of the base precursor, 12 ml of 3% by weight aqueous solution of sodium polystyrenesulfonate, 10% by weight of SBR latex 180 g of the liquid was mixed. Immediately before coating, 80 ml of a 4% by weight aqueous solution of N, N-ethylenebis (vinylsulfonacetamide) was mixed to prepare a coating solution for preventing halation.

4) Preparation of back surface protective layer coating solution The container was kept at 40 ° C., and 40 g of gelatin, 35 mg of benzoisothiazolinone and 840 ml of water were added to dissolve the gelatin. Further, 5.8 ml of 1 mol / L sodium hydroxide aqueous solution, 5 g of 10% by weight emulsion of liquid paraffin, 5 g of 10% by weight emulsion of trimethylolpropane triisostearate, di (2-ethylhexyl) sodium sulfosuccinate 5 10 ml of a mass% aqueous solution, 20 ml of a 3 mass% aqueous solution of sodium polystyrene sulfonate, 2.4 ml of a 2 mass% solution of a fluorosurfactant (F-1), and 2 of a 2 mass% solution of a fluorosurfactant (F-2) .4 ml, 32 g of a 19% by weight liquid of methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization weight ratio 57/8/28/5/2) latex was mixed. Immediately before coating, 25 ml of a 4% by weight aqueous solution of N, N-ethylenebis (vinylsulfonacetamide) was mixed to prepare a coating solution for the back surface protective layer.

5) Application of back layer On the back surface side of the undercoat support, the coating amount of the antihalation layer coating solution is 0.52 g / m ^2, and the coating amount of the back surface protective layer coating solution is 1 A simultaneous multilayer coating was applied so as to be 0.7 g / m ² , followed by drying to prepare a back layer.

(Image forming layer)
1) Silver halide emulsion << Preparation of silver halide emulsion 1 >>
To a solution of 1421 ml of distilled water, 3.1 ml of a 1% by mass potassium bromide solution was added, and a solution containing 3.5 ml of 0.5 mol / L sulfuric acid and 31.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 30 ° C., the solution A diluted with 95.4 ml of distilled water added to 22.22 g of silver nitrate, 15.3 g of potassium bromide and 0.8 g of potassium iodide in a distilled water volume of 97.4 ml. The whole amount of the solution B diluted to 1 was added at a constant flow rate over 45 seconds. Thereafter, 10 ml of a 3.5% by mass aqueous hydrogen peroxide solution was added, and 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 to be diluted to 317.5 ml, a solution D in which 44.2 g of potassium bromide and 2.2 g of potassium iodide were diluted with distilled water to a volume of 400 ml was added to solution C. Was added at a constant flow rate over 20 minutes, and solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of the solution C and the solution D so as to be 1 × 10 ⁻⁴ mol per mol of silver. Further, 5 seconds after the completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

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

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

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

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

<< Preparation of mixed emulsion Q for coating solution >>
70% by weight of silver halide emulsion 1, 15% by weight of silver halide emulsion 2 and 15% by weight of silver halide emulsion 3 were dissolved, and 7% by mole of silver in a 1% by weight aqueous solution of benzothiazolium iodide. × 10 ^-3 mol was added.
Furthermore, the amount of the one-electron oxidant produced by one-electron oxidation is 2 × 10 ⁻³ moles per mole of silver halide of each compound 1, 2, and 3 capable of emitting one electron or more. Added.
Adsorbing redox compounds 1 and 2 having an adsorbing group and a reducing group were added in an amount of 5 × 10 ⁻³ mol per mol of silver halide.
Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver. 1- (3-Methylureidophenyl) -5-mercaptotetrazole was added so as to give 0.34 g per kg of the mixed emulsion for coating solution.

<Addition of thiocyanate>
Similar to Example 2, thiocyanate was added in various steps.

2. Performance Evaluation Each sample was exposed with Fuji Medical Co., Ltd. dry laser imager DRYPIX7000 (mounted with a 660 nm semiconductor laser with a maximum output of 50 mW (IIIB)), and thermally developed (107 ° C-121 ° C-121 ° C) Total 14 seconds with panel heater).

  The evaluation results are shown in Table 4. As a result, the photothermographic material of the present invention had high sensitivity, low fog, and excellent raw storability. However, compared with the photothermographic material of Example 2 using silver iodide, the haze after heat development remained high in the silver bromide tabular grains of Example 4.

It is an emission spectrum of the fluorescent intensifying screen A.

Claims (20)

  A method for producing a photothermographic material having an image forming layer containing a non-photosensitive silver salt, a photosensitive silver halide, and a reducing agent on at least one surface of a support, the production method comprising at least the above-mentioned photosensitive A step of forming a silver halide grain, a step of mixing with the non-photosensitive silver salt, a step of preparing the coating solution for the image forming layer, and a step of coating the coating solution on the support. Thereafter, a method for producing a photothermographic material, wherein thiocyanate is added in a step before the coating step.   A chemical sensitization step is provided between the particle formation step and the mixing step of the non-photosensitive silver salt, and the thiocyanate is added after the chemical sensitization step and before the coating step. The method for producing a photothermographic material according to claim 1. 3. The method for producing a photothermographic material according to claim 1, wherein the thiocyanate is added in an amount of 1 × 10 ⁻⁵ mol% to 1 mol% with respect to the photosensitive silver halide. . 4. The method for producing a photothermographic material according to claim 3, wherein the thiocyanate is added in an amount of 1 × 10 ⁻⁴ mol% to 1 × 10 ⁻¹ mol% with respect to the photosensitive silver halide. . 5. The method for producing a photothermographic material according to claim 4, wherein the thiocyanate is added in an amount of 1 × 10 ⁻³ mol% to 1 × 10 ⁻¹ mol% with respect to the photosensitive silver halide. .   6. The method for producing a photothermographic material according to claim 1, wherein the thiocyanate is an alkali metal salt of thiocyanic acid.   7. The method for producing a photothermographic material according to claim 2, wherein the chemical sensitization step of the photosensitive silver halide includes chalcogen sensitization.   8. The method for producing a photothermographic material according to claim 7, wherein the chalcogen sensitization is at least one selected from sulfur sensitization, selenium sensitization, and tellurium sensitization.   9. The method for producing a photothermographic material according to claim 2, wherein the chemical sensitization step of the photosensitive silver halide includes gold sensitization.   The method for producing a photothermographic material according to claim 1, wherein the thiocyanate is added in a step prior to the step of mixing with the non-photosensitive silver salt.   10. The method for producing a photothermographic material according to claim 1, wherein the thiocyanate is added in a mixing step with the non-photosensitive silver salt.   The method for producing a photothermographic material according to claim 1, wherein the thiocyanate is added in the step of preparing the image forming layer coating solution.   13. The photothermographic material according to claim 1, wherein 50% or more of the projected area of the photosensitive silver halide is a tabular grain having an aspect ratio of 2 or more. Production method.   14. The method for producing a photothermographic material according to claim 13, wherein an average sphere equivalent diameter of the tabular grains is 0.3 μm or more and 8.0 μm or less.   15. The method for producing a photothermographic material according to claim 1, wherein an average silver iodide content of the photosensitive silver halide is 40 mol% or more.   The method for producing a photothermographic material according to claim 15, wherein an average silver iodide content of the photosensitive silver halide is 80 mol% or more.   The method for producing a photothermographic material according to claim 16, wherein the average silver iodide content of the photosensitive silver halide is 90 mol% or more.   A photothermographic material produced by the method for producing a photothermographic material according to claim 1. 19. The photothermographic material according to claim 18, wherein the thiocyanate is contained in an amount of 1 × 10 ⁻⁴ mol% to 1 mol% with respect to the photosensitive silver halide. 20. The photothermographic material according to claim 19, wherein the thiocyanate is contained in an amount of 1 × 10 ⁻³ mol% to 1 × 10 ⁻¹ mol% with respect to the photosensitive silver halide.

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