JP2000112059A - Heat-developable photosensitive material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-developable photosensitive material high in sensitivity, low in fog and excellent in storage property. SOLUTION: This photosensitive material has a photosensitive layer satisfying all of the requirements described in (1) to (3). (1) The coating liquid used to form the photosensitive layer has a pAg of >=2.5 to <=6.5 at 40 deg.C. (2) The photosensitive silver halide particles have an equivalent spherical diameter of between 10 nm and 50 nm. (3) The photosensitive silver halide particles are spectrally sensitized with a spectral sensitizing dye.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photothermographic material (hereinafter sometimes referred to as a photothermographic material) and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand in the medical field to reduce the amount of waste liquid from the viewpoint of environmental protection and space saving. Photosensitive thermal development for medical diagnostics and photographic technology, which can be efficiently exposed by a laser imagesetter or laser imager and can form a sharp black image with high resolution and sharpness Techniques for photographic materials are needed. These photothermographic materials can eliminate the use of solution processing chemicals and provide a simpler and more environmentally friendly thermal development system to customers.

In a photothermographic material comprising a non-photosensitive organic silver salt, a photosensitive silver halide and a reducing agent, a spectral sensitizing dye is easily desorbed, the spectral sensitizing efficiency is low, the sensitivity is low, and a large amount of Dye required. In addition, because of the built-in reducing agent, silver halide is easily reduced due to reduction during storage, and a large amount of silver ion-adsorbed substances is adsorbed on the silver halide surface to stabilize it. Although it was necessary, as a result, desorption of dye and suppression of development occurred, and the sensitivity was apt to be lowered. In addition, the use of a large amount of adsorbed substances to silver ions caused suppression of development and deterioration of silver tone. In the case of a heat-developable photosensitive material in which high-illuminance exposure is important, improvement of reciprocity failure was important in order to increase sensitivity. The illuminance sensitivity was remarkably reduced, and sufficient sensitivity could not be increased particularly in the spectral sensitization region even when polyvalent metal dope was used.

The photothermographic material described in the present invention is composed of a material having high hydrophobicity such as silver organic fatty acid and a reducing agent during heat development. Therefore, the sensitizing dye which is originally easily adsorbed to silver halide is also easily adsorbed to another material and easily desorbed from silver halide. Therefore, a large amount of dye is used, but this leads to residual color, preservability and deterioration of fogging, even for a heat-developable photosensitive material. This tendency of desensitization was particularly remarkable when a sensitizing dye having an absorption maximum at 600 nm or more was used, or when the particle size was very small such as less than 50 nm.

It is widely used in the art to add a compound having a mercapto group or a nitrogen-containing heterocyclic compound to a light-sensitive material in order to increase spectral sensitization efficiency or improve storage stability. However, in the system of photothermographic materials, desensitization due to desorption of the sensitizing dye, deterioration of silver tone, and suppression of development during thermal development are likely to occur. It was an accompanying technology.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photothermographic material having high sensitivity, low fog, and excellent storage stability, and a method for producing the same.

[0007]

This and other objects are achieved by the following (1) to (7). (1) In a photothermographic material having at least one photosensitive layer containing at least a non-photosensitive organic silver salt, a reducing agent and photosensitive silver halide grains on a support, the photosensitive layer is preferably A photothermographic material which satisfies all of the above requirements. PA of a coating solution used for coating the photosensitive layer
g is not less than 2.5 and not more than 6.5 at 40 ° C. The sphere equivalent diameter of the photosensitive silver halide grains is 10 nm or more and 50 nm or less. The photosensitive silver halide grains are spectrally sensitized by a spectral sensitizing dye. (2) The photothermographic material according to the above (1), wherein the photothermographic material does not contain a substance adsorbed on the surface of the silver halide in an amount exceeding an amount that reduces the ionic conductivity of the photosensitive silver halide emulsion to 1/10 or less. (3) The above (1), wherein the photosensitive silver halide emulsion contains a polyvalent metal compound in an amount of 1 × 10 ⁻⁵ mol / Ag mol or more.
Or the photothermographic material according to (2). (4) The amount of the spectral sensitizing dye added is 1
The photothermographic material according to any one of the above (1) to (3), wherein the amount is 1 × 10 ^-3 mol or more and 1 × 10 ^-1 mol per mol. (5) Any one of the above (1) to (4), wherein the main binder of the photosensitive layer is a water-soluble polymer and / or a water-dispersible polymer, and 30% by weight or more of the solvent of the coating solution is water. 2. The photothermographic material according to item 1. (6) The photothermographic material according to any one of the above (1) to (5), wherein the spectral sensitizing dye has an absorption maximum at 600 nm or more. (7) A photothermographic material in which at least one photosensitive layer is provided by applying and drying a coating solution containing at least a non-photosensitive organic silver salt, a reducing agent and photosensitive silver halide particles on a support. Wherein the coating solution satisfies all of the following requirements (1) to (4). The coating solution has a pAg of 2.5 or more and 6.5 or less at 40 ° C. The sphere equivalent diameter of the photosensitive silver halide grains is 10 nm or more and 50 nm or less. The photosensitive silver halide grains are spectrally sensitized by a spectral sensitizing dye.

[0008] In a normal silver halide light-sensitive material, a coating solution for an emulsion layer is prepared with a pAg of 7 to 9. The major tendency is that the lower the pAg, the higher the sensitivity and the better the progress of development. However, the pAg tends to suffer, and storage fouling and pressure blackening tend to occur. When the pAg is high, storage fogging and pressure fogging are reduced, but the sensitivity may be lowered or the development stability may be lowered. Therefore, it is an unpredictable effect that a system having excellent storage stability and high color sensitization efficiency can be obtained in a region having a higher potential (lower pAg) so as to include a region where silver ions are excessive as in the present invention. there were.

However, as a result of intensive studies, the present inventors have found that in a system using ultra-small silver halide grains having a grain size of less than 50 nm, this low pAg region is
In particular, it has been found that the color sensitization sensitivity is high and the storage stability is excellent.

Further, in such a system, even if a small amount of a compound which easily adsorbs to silver ions on the surface of the silver halide grains is used, good preservability can be ensured, so that developability and silver tone are improved. It has been found to be an excellent light-sensitive material.

Further, in such a system, in particular, when recording with a high illuminance light source such as a laser, by doping a polyvalent metal such as iridium ion of 1 × 10 ⁻⁵ mol or more,
It was confirmed that the composition exhibited superchemical properties with respect to the increase in high-intensity sensitivity. This phenomenon is particularly noticeable in the color sensitized region.

Although the details of the technical contents of the present invention are not clear, what is expected will be described below.

It has long been known that ultrafine silver halide particles exhibit high ionic conductivity (that is, high interstitial silver ion concentration) due to silver ions diffusing from the surface of the grains to interstitial spaces. This tendency is more remarkable as the particles become finer.

It is generally known in the art that this high ionic conductivity causes inefficiency, which is called latent image dispersion, which occurs particularly in high illuminance and color sensitizing particles, and significantly lowers the sensitivity of a light-sensitive material. Are known.

It is known that a compound that adsorbs to silver ions on the surface of the particles, for example, a compound having a mercapto group, a nitrogen-containing heterocyclic compound, and the like are effective in reducing the ionic conductivity. However, in order to cover the surface of an extremely small silver halide grain as in the present invention, for example, an adsorbing substance in an amount of about 10 ⁻² mol per mol of silver is required. However, the addition of such a large amount of an adsorptive material (generally also used as an anti-fogging / stabilizing agent) causes not only the above-described suppression of development and deterioration of silver tone, but also hinders color sensitization.

On the other hand, when the pAg is set in the range of the present invention, the concentration of recommended silver ions in the lattice can be suppressed, and the ionic conductivity can be reduced. Therefore, the same effect can be realized in a region where the amount of the adsorbent is small.

However, in this case, it is expected from the prior art that the silver ion concentration outside the silver halide becomes high, which usually causes fogging and increases storage fog. .

However, in a photothermographic material system, particularly in a region below a particle diameter of 50 nm, particularly in a color sensitizing system,
Surprisingly, it has been newly found that the problems of increased fogging and storage fogging due to low pAg are eliminated.

The discovery of this synergistic effect is the gist of the present invention.

In terms of increasing the sensitivity, under the above conditions,
In particular, when a polyvalent metal ion such as iridium is doped into grains at 10 ^-5 mol or more per mol of silver halide, p
In a system having a high Ag or a system having a particle size larger than 50 nm, the sensitizing effect of high illuminance sensitivity, which was not sufficient, has come to be remarkably exhibited.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. <Coating solution pAg> pAg of the coating solution for the photosensitive layer of the present invention
Is preferably 2.5 to 6.5 at 40 ° C.

Further, the range is preferably 3.0 to 6.0, more preferably 3.0 to 5.5, and particularly preferably the range of 3.0 to 5.5.

The pAg of the coating solution can be adjusted by changing the addition amount of the aqueous silver nitrate solution when preparing the organic silver salt dispersion, which is effective for adjusting the pAg of the coating solution. However, finally, silver nitrate and KBr were added to the coating solution.
It is preferable to achieve the above method by adjusting the amount of the aqueous solution to be added.

The pAg of the coating solution can be measured by a conventional method, for example, DA-300 manufactured by Kyoto Electronics Industry Co., Ltd.

The photosensitive layer of the present invention is formed by applying the above coating solution on a support and drying the coating solution.
g is preferably 3 to 7.

<Water-soluble polymer and / or water-dispersible polymer> The effect of the present invention is that the photosensitive layer is formed by applying and drying a coating solution in which 30% by weight or more of the solvent is water (aqueous solvent). In some cases, the binder of the photosensitive layer (hereinafter referred to as “the polymer of the present invention”) is soluble or dispersible in an aqueous solvent (aqueous solvent), and particularly has an equilibrium water content of 2 wt% or less at 25 ° C. and 60% RH. It improves when it is composed of a polymer latex. The most preferred form has an ionic conductivity of 2.5 mS
/ cm or less. Examples of such a preparation method include a method of purifying a polymer using a separation functional membrane after synthesis.

The aqueous solvent in which the polymer of the present invention is soluble or dispersible is water or a mixture of water and less than 70% by weight of a water-miscible organic solvent. Examples of the water-miscible organic solvent include, for example, alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol;
Examples thereof include cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, ethyl acetate, and dimethylformamide.

In the case where the polymer is not thermodynamically dissolved but exists in a so-called dispersed state, the term "aqueous solvent" is used herein.

The "equilibrium water content at 25 ° C. and 60% RH" referred to in the present invention refers to the weight W1 of a polymer in humidity control equilibrium in an atmosphere of 25 ° C. and 60% RH and the weight of a polymer in an absolutely dry state at 25 ° C. It can be expressed as follows using the weight W0.

Equilibrium water content at 25 ° C. and 60% RH = {(W1-W
0) / W0} × 100 (wt%) For the definition and measurement method of water content, for example, Polymer Engineering Course 14, Polymer Material Testing Method (edited by the Society of Polymer Science, Jinjinshokan) .

The equilibrium water content at 25 ° C. and 60% RH of the polymer of the present invention is preferably 2% by weight or less, more preferably 0.01% by weight or more and 1.5% by weight or less, further preferably 0.02% by weight or more. 1 wt% or less is desirable.

The polymer of the present invention is not particularly limited as long as it is soluble or dispersible in the above-mentioned aqueous solvent and has an equilibrium water content at 25 ° C. and 60% RH of 2% by weight or less. Among these polymers, polymers that can be dispersed in an aqueous solvent are particularly preferred.

Examples of the dispersion state include a latex in which fine particles of a solid polymer are dispersed, a polymer in which a molecule having a hydrophilic portion in a molecule is dispersed in a molecular state, or a dispersion by forming micelles. And emulsified and dispersed ones, all of which are preferred, with latex being particularly preferred.

In a preferred embodiment of the present invention, acrylic resin, polyester resin, rubber resin (for example, S
(BR resin), a polyurethane resin, a vinyl chloride resin, a vinyl acetate resin, a vinylidene chloride resin, a hydrophobic polymer such as a polyolefin resin. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized, or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The polymer has a number average molecular weight of 5,000 to 1,000,000, preferably 10,000 to 200,000, in terms of number average molecular weight. If the molecular weight is too small, the mechanical strength of the emulsion layer is insufficient, and if it is too large, the film-forming properties are poor, which is not preferable.

Specific examples of preferred polymers include the following. In the following, the raw material monomers are used, and the numerical values in parentheses are wt%, and the molecular weight is the number average molecular weight.

Latex of P-1; -MMA (70) -EA (27) -MAA (3)-(molecular weight 37000) P-2; -MMA (70) -2EHA (20) -St (5) -AA (5) -Latex (molecular weight 40000) P-3; -St (50) -Bu (47) -MAA (3) -latex (molecular weight 4500
0) P-4; -St (68) -Bu (29) -AA (3)-latex (MW 60000) P-5; -St (70) -Bu (27) -IA (3)-latex (Molecular weight 12000
0) Latex of P-6; -St (75) -Bu (24) -AA (1)-(molecular weight 10800
0) P-7; -St (60) -Bu (35) -DVB (3) -MAA (2)-latex (molecular weight 150,000) P-8; -St (70) -Bu (25) -DVB ( 2) -AA (3)-latex (molecular weight 280000) P-9; -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-latex (molecular weight 80000) P-10; -VDC (85) -MMA (5) -EA (5) -MAA (5)-latex (molecular weight 67,000) P-11; -Et (90) -MAA (10)-latex (molecular weight) 12000)

The abbreviations of 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 polymers described above are commercially available, and the following polymers can be used. Examples of acrylic resin include Sebian A-4635, 46683, 4601 (all manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 85
Examples of polyester resins such as 7 (all manufactured by Zeon Corporation) include FINETEX ES650, 611, 675, 850 (all manufactured by Dainippon Ink and Chemicals), WD-size, WMS (all manufactured by Eastman Chemical Co., Ltd.) HYDRA is an example of a polyurethane resin.
Examples of rubber resins such as NAP10, 20, 30, 40 (all manufactured by Dainippon Ink and Chemicals, Inc.) include LACSTAR 7310K, 3307B,
4700H, 7132C (all manufactured by Dainippon Ink and Chemicals, Inc.), Nipol Lx
Examples of vinyl chloride resins such as 416, 410, 438C, and 2507 (all manufactured by Nippon Zeon Co., Ltd.)
Examples of vinylidene chloride resin, such as L502,
Examples of olefin resins such as L513 (manufactured by Asahi Chemical Industry Co., Ltd.) include Chemipearl S120 and SA100 (Mitsui Petrochemical
And the like).

These polymers may be used alone as a polymer latex, or two or more may be blended if necessary.

The polymer latex used in the present invention is particularly preferably a styrene-butadiene copolymer latex. The weight ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably from 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 weight. The preferred molecular weight range is the same as described above.

Styrene which is preferably used in the present invention
As the butadiene copolymer latex, the above-mentioned P-3
~ P-8, commercial products LACSTAR-3307B, 7132C, Nipol Lx4
16, and the like.

The organic silver salt-containing layer of the light-sensitive material of the present invention may optionally contain a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose and hydroxypropylcellulose. The amount of these hydrophilic polymers added is 30 wt% or less of the total binder in the organic silver salt-containing layer,
More preferably, it is 20 wt% or less.

The organic silver salt-containing layer of the present invention is formed using a polymer latex. The amount of the binder in the organic silver salt-containing layer is such that the weight ratio of total binder / organic silver salt is 1/100. The range is preferably 10 to 10/1, more preferably 1/5 to 4/1.

The organic silver salt-containing layer is usually a photosensitive layer (emulsion layer) containing a photosensitive silver halide, which is a photosensitive silver salt. The weight ratio of silver halide is preferably in the range of 400 to 5, more preferably 200 to 10.

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

In the present invention, the solvent of the coating solution for the organic silver salt-containing layer of the light-sensitive material (herein, the solvent and the dispersion medium are collectively referred to as a solvent for simplicity) is an aqueous solvent containing 30% by weight or more of water. As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, and ethyl acetate may be used. The water content of the solvent in the coating solution is preferably at least 50 wt%, more preferably at least 70 wt%. Examples of preferred solvent compositions include 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, and the like.

<Description of Silver Halide Fine Particles> The grain size of the photosensitive silver halide of the present invention is specifically from 10 nm to 50 nm, more preferably from 20 nm to 45 nm,
More preferably, the thickness is 20 nm or more and 35 nm or less. The grain size referred to here is the sphere equivalent diameter of the silver halide grains when the silver halide grains are cubic or octahedral so-called normal crystals. In the case where the silver halide grains are tabular grains, the diameter refers to a diameter when converted into a circular image having the same area as the projected area of the main surface. In the case of other than normal crystals, for example, in the case of spherical grains, rod-shaped grains, etc., it refers to the diameter of a sphere equivalent to the volume of silver halide grains.

As a method for preparing such a silver halide microcrystal having an extremely small grain size, not only the method described in the Examples but also a method as described in, for example, Japanese Patent Application Laid-Open No. H10-111541. Various methods such as instantaneous mixing of a silver ion solution and a halogen solution while performing high-speed mixing in a reaction vessel can be preferably used.

The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide, and silver iodochlorobromide can be used. . The distribution of the halogen composition in the grains may be uniform, the halogen composition may change stepwise, or may change continuously. Further, silver halide grains having a core / shell structure can be preferably used. The preferred structure is 2
Core / shell particles having a 55-fold structure, more preferably a 2- to 4-fold structure, can be used. A technique for localizing silver bromide on the surface of silver chloride or silver chlorobromide grains can also be preferably used.

The shape of the silver halide grains is cubic,
Octahedral, tabular particles, spherical particles, rod-like particles, potato-like particles and the like can be mentioned. In the present invention, cubic particles and normal crystal particles are particularly preferable. When tabular silver halide grains are used, the average aspect ratio is preferably 100: 1 to 2: 1, more preferably 50: 1.
３3: 1. Further, grains having rounded corners of silver halide grains can also be preferably used. The surface index (mirror index) of the outer surface of the photosensitive silver halide grains is not particularly limited, but the spectral sensitizing efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The ratio is preferably 50% or more,
It is more preferably at least 65%, further preferably at least 80%. The ratio of the {100} Miller index is determined by T. Tani, which utilizes the dependence of the adsorption of the sensitizing dye on the {111} and {100} planes.
It can be determined by the method described in J. Imaging Sci., 29, 165 (1985).

Methods for forming photosensitive silver halide are well known in the art, for example, Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458.
Can be used.Specifically, a photosensitive silver halide is prepared by adding a silver-supplying compound and a halogen-supplying compound to gelatin or another polymer solution, and then the organic silver halide is added. A method of mixing with a silver salt can be used.

<Polyvalent Metal Compound> The photosensitive silver halide emulsion of the present invention can contain a polyvalent metal compound. Examples of the polyvalent metal compound include a metal complex of Group VII or Group VIII of the periodic table. Rhodium, rhenium, ruthenium, preferably as the central metal of the metal complex of Group VII or Group VIII of the periodic table,
Osnium, iridium and iron. One kind of these metal complexes may be used, or a complex of the same kind of metal and a different kind of metal may be used.
More than one species may be used in combination. Preferably it is iridium.
The preferred content of the polyvalent metal compound is 1 × 1 per mole of silver.
0 ranging from ^-9 moles of 1 × 10 ^-2 mol appropriate, 1 as the lower limit
× 10 ^-5 mol or more is more preferable, from 1 × 10 ^-5 mol to 1 × 10 mol
A range of ^-3 mol is more preferred. As a specific structure of the metal complex, a metal complex having a structure described in JP-A-7-225449 or the like can be used.

As the rhodium compound used in the present invention, a water-soluble rhodium compound can be used. For example, a rhodium (III) halide compound or a rhodium complex salt having a ligand such as halogen, amines, oxalato, etc., for example, hexachlororhodium (III)
Complex salt, pentachloroacolodium (III) complex salt, tetrachlorodiachodium (III) complex salt, hexabromorhodium
(III) complex salts, hexaammine rhodium (III) complex salts, and trizalatrodium (III) complex salts. These rhodium compounds are used by dissolving them in water or a suitable solvent. A method generally used for stabilizing a solution of a rhodium compound, that is, an aqueous hydrogen halide solution (for example, hydrochloric acid, hydrobromic acid, hydrofluoric acid) Etc.) or a method of adding an alkali halide (eg, KCl, NaCl, KBr, NaBr, etc.). Instead of using water-soluble rhodium, it is also possible to add and dissolve other silver halide grains doped with rhodium during the preparation of silver halide.

These compounds can be appropriately added at the time of production of silver halide emulsion grains and at each stage before coating the emulsion.
It is preferably incorporated into silver halide grains.

Rhenium, ruthenium and osmium used in the present invention are described in JP-A-63-2042 and JP-A-1-285941.
, 2-20852, 2-20855, etc. in the form of a water-soluble complex salt. Particularly preferred is a six-coordinate complex represented by the following formula. [ML ₆ ] ^n- where M represents Ru, Re or Os, L represents a ligand, n
Represents 0, 1, 2, 3 or 4.

In this case, the counter ion is not important, and an ammonium or alkali metal ion is used.

Preferred ligands include halide ligands, cyanide ligands, cyanide ligands, nitrosyl ligands, thionitrosyl ligands and the like.
Examples of specific complexes used in the present invention are shown below, but the present invention is not limited thereto.

[ReCl ₆ ] ^3- , [ReBr ₆ ] ^3- , [ReCl ₅ (NO)] ^2- ,
_{[Re (NS) Br 5]} 2-, [Re (NO) (CN) 5] 2-, [Re (O) 2 (CN) 4] 3-,
[RuCl ₆ ] ^3- [RuCl ₄ (H ₂ O) ₂ ] ^- , [RuCl ₅ (H ₂ O)] ^2- , [RuCl ₅ (NO)] ^2- , [Ru
^{_{Br 5 (NS)] 2-,}} [Ru (CO) 3 Cl 3] 2-, [Ru (CO) Cl 5] 2- [Ru (CO) Br 5] 2-, [OsCl 6] 3-, [ OsCl ₅ (NO)] ^2- , [Os (NO)
^{_{(CN) 5] 2-, [}} Os (NS) Br 5] 2 -, [Os (O) 2 (CN) 4] 4-

These compounds can be appropriately added at the time of production of silver halide emulsion grains and at each stage before coating the emulsion.
It is preferably incorporated into silver halide grains.

In order to add these compounds into silver halide grains by adding them during silver halide grain formation, a metal complex powder or an aqueous solution dissolved together with NaCl and KCl is added to the aqueous solution during grain formation. A method in which a silver halide grain is prepared by a method in which a silver salt and a halide solution are added simultaneously as a third solution when the silver salt and the halide solution are simultaneously mixed, Alternatively, there is a method in which a required amount of an aqueous solution of a metal complex is charged into a reaction vessel during particle formation. In particular, a method in which a powder or an aqueous solution dissolved together with NaCl and KCl is added to a water-soluble halide solution is preferable.

For the addition to the particle surface, a required amount of an aqueous solution of a metal complex can be charged into the reaction vessel immediately after the formation of the particles, during or during physical ripening, or at the time of chemical ripening.

Various compounds can be used as the iridium compound used in the present invention, and examples thereof include hexachloroiridium, hexaammineiridium, trioxalatoiridium, hexacyanoiridium, and pentachloronitrosyliridium. These iridium compounds are used after being dissolved in water or a suitable solvent. However, a method generally used for stabilizing a solution of the iridium compound, that is, an aqueous solution of hydrogen halide (for example, hydrochloric acid, hydrobromic acid, hydrofluoric acid) is used. Etc.) or a method of adding an alkali halide (eg, KCl, NaCl, KBr, NaBr, etc.). Instead of using water-soluble iridium, it is also possible to add and dissolve another iridium-doped silver halide grain during silver halide preparation.

Further, the silver halide emulsion used in the present invention includes cobalt, iron, nickel, chromium, palladium,
It may contain metal atoms such as platinum, gold, thallium, copper and lead. For compounds of cobalt, iron, chromium, and ruthenium, hexacyano metal complexes can be preferably used. Specific examples include ferricyanate ion, ferrocyanate ion, hexacyanocobaltate ion,
Examples include, but are not limited to, hexacyanochromate ions and hexacyanoruthenate ions. The phase containing the metal complex in the silver halide may be uniform, may be contained in the core at a high concentration, or may be contained in the shell at a high concentration, and there is no particular limitation.

The above metal is 1 × 1 per mole of silver halide.
It is preferably from 0 ^-9 to 1 × 10 ^-4 mol. Further, in order to incorporate the metal, a metal salt in the form of a single salt, a double salt, or a complex salt can be added at the time of preparing particles.

The photosensitive silver halide grains can be desalted by washing with a method known in the art such as a noodle method, flocculation method and ultrafiltration method. You don't have to.

As the gold sensitizer used for sensitizing the silver halide emulsion of the present invention to gold, the oxidation number of gold may be +1 or +3, and is usually used as a gold sensitizer. Gold compounds can be used. Representative examples include chloroauric acid, potassium chloroaurate, auric trichloride, potassium auric thiocyanate, potassium iodooleate, tetracyano auric acidide, ammonium aurothiocyanate, pyridyl trichlorogold and the like.

The amount of the gold sensitizer to be added varies depending on various conditions. As a guide, the amount is from 1 × 10 ⁻⁷ mol to 1 × 10 ⁻³ mol, more preferably 1 × 10 ⁻⁶ mol, per mol of silver halide. Mol or more
5 × 10 ^-4 or less.

The silver halide emulsion of the present invention is preferably used in combination with gold sensitization and another chemical sensitization. As other chemical sensitization methods, known methods such as a sulfur sensitization method, a selenium sensitization method, a tellurium sensitization method, and a noble metal sensitization method can be used. When used in combination with the gold sensitization method,
For example, sulfur sensitization and gold sensitization, selenium sensitization and gold sensitization, sulfur sensitization and selenium sensitization and gold sensitization, sulfur sensitization and tellurium sensitization and gold sensitization Preferred methods include sulfur sensitization, selenium sensitization, tellurium sensitization, and gold sensitization.

The sulfur sensitization preferably used in the present invention is
Usually, a sulfur sensitizer is added, and the emulsion is stirred at a high temperature of 40 ° C. or higher for a certain period of time. As the sulfur sensitizer, known compounds can be used.For example, in addition to the sulfur compound contained in gelatin, various sulfur compounds such as thiosulfates, thioureas, thiazoles, and rhodanines are used. be able to. Preferred sulfur compounds are thiosulfates and thiourea compounds. The addition amount of the sulfur sensitizer varies under various conditions such as the pH, temperature, and size of silver halide grains during chemical ripening.
It is 1 × 10 ⁻⁷ to 1 × 10 ⁻² mol per mol, more preferably 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol.

As the selenium sensitizer used in the present invention, known selenium compounds can be used. That is, it is usually carried out by adding an unstable and / or non-unstable selenium compound and stirring the emulsion at a high temperature of 40 ° C. or higher for a certain time. As unstable selenium compounds, JP-B-44-15748, JP-B-43-13489, JP-A-4-25832
And the compounds described in JP-A Nos. 4-109240 and 3-217798 can be used. In particular, the general formula (V
It is preferable to use the compounds represented by III) and (IX).

The tellurium sensitizer used in the present invention is a compound which forms silver telluride which is presumed to be a sensitizing nucleus on the surface or inside of silver halide grains. The formation rate of silver telluride in a silver halide emulsion is described in JP-A-5-3132.
It can be tested by the method described in No. 84. Examples of tellurium sensitizers include diacyl tellurides, bis (oxycarbonyl) tellurides, bis (carbamoyl) tellurides, diacyl tellurides, bis (oxycarbonyl) ditellurides, bis (carbamoyl) ditellurides, P = Te Compounds having a bond, tellurocarboxylates, Te-organyltellurocarboxylates, di (poly) tellurides,
Tellurides, tellurols, telluroacetals, tellurosulfonates, compounds having a P-Te bond, Te-containing heterocycles, tellurocarbonyl compounds, inorganic tellurium compounds,
Colloidal tellurium or the like can be used. Specifically, U.S. Patent Nos. 1,623,499, 3,320,069,
No. 772,031, British Patent No. 235,211 and No. 1,121,496,
No. 1,295,462, No. 1,396,696, Canadian Patent No. 800,
No. 958, JP-A-4-204640, JP-A-3-53693, JP-A-3-31598
No. 4-129787, Journal of Chemical Society Chemical Communication (J. Chem. So
c.Chem.Commun.), 635 (1980), ibid, 1102 (1979), ibi
d, 645 (1979), Journal of Chemical Society Parkin Transaction 1 (J. Chem. Soc. Pe
rkin.Trans.1), 2191 (1980), edited by S. Patai, edited by The Chemistry of Or, Selenium and Tellurium Campounds
ganic Serenium and Tellunium Compounds), Vol 1 (198
6) and the compounds described in Vol. 2 (1987) can be used. In particular, JP-A-5-313284 discloses general formulas (II), (III) and (I).
Compounds represented by V) are preferred.

The amount of the selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains to be used, the conditions of chemical ripening, etc., but is generally from 1 × 10 ^-8 to 1 × 10 ⁸ per mol of silver halide. ^-2 mol, preferably 1 × 10 ^-7 to 1 × 10
^Use about ^-3 moles. The conditions for chemical sensitization in the present invention are not particularly limited, but the pH is 5 to 8, the pAg is 6 to 11, preferably 7 to 10, and the temperature is 40 to 95 ° C, preferably 45 to 95 ° C. 85 ° C.

In the silver halide emulsion used in the present invention, a cadmium salt, a sulfite, a lead salt, a thallium salt and the like may be coexistent during the formation of silver halide grains or physical ripening.

In the present invention, reduction sensitization can be used. As specific compounds of the reduction sensitization method, in addition to ascorbic acid and thiourea dioxide, for example, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds and the like can be used. . When the pH of the emulsion is 7 or more,
Reduction sensitization can be achieved by aging while maintaining the pAg at 8.3 or less. Further, reduction sensitization can be achieved by introducing a single addition portion of silver ion during grain formation.

The silver halide emulsion of the present invention can be obtained from European Patent 293,
A thiosulfonic acid compound may be added by the method described in No. 917.

The silver halide emulsion in the light-sensitive material used in the present invention may be only one kind or two or more kinds (for example,
Those with different average grain sizes, different halogen compositions, different crystal habits, different chemical sensitization conditions)
You may use together.

The photosensitive silver halide of the present invention may be prepared by mixing a separately prepared photosensitive silver halide and an organic silver salt with each other by using a high-speed stirrer. Or a method of mixing with a ball mill, a sand mill, a colloid mill, a vibration mill, a homogenizer, or a photosensitive silver halide prepared at any timing during the preparation of an organic silver salt to prepare an organic silver salt. Although there are methods and the like, it is necessary to separately adjust the silver halide and the organic silver salt as long as the effects of the present invention are sufficiently exhibited. Otherwise, the distribution of the distance between the silver halide grains becomes large or it becomes difficult to maintain the desired distance depending on the dispersion state of the organic silver salt in the film, the ratio to the binder, and the size.

The timing of adding the silver halide of the present invention to the coating solution for the image forming layer is preferably from 180 minutes to immediately before coating, and preferably from 60 minutes to 10 seconds before coating. Is not particularly limited as long as the effects of the present invention are sufficiently exhibited. As a specific mixing method, a method of mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid sent to the coater is set to a desired time, by N. Harnby, MFE Edwards, AW Nienow, translated by Koji Takahashi "Liquid mixing technology" (Nikkan Kogyo Shimbun, 1989)
There is a method using a static mixer or the like described in Chapter 8 or the like.

<Spectral Sensitizing and Sensitizing Dye> The sensitizing dye used in the present invention can spectrally sensitize silver halide grains in a desired (600 nm to 1,700 nm) wavelength region when adsorbed on silver halide grains. Anything is acceptable if it is. That is, as the sensitizing dye of the present invention, 600 nm
Any material having an absorption maximum as described above may be used. As the sensitizing dye, a cyanine dye, a merocyanine dye, a complex cyanine dye, a complex merocyanine dye, a holo-holerocyanine dye, a styryl dye, a hemicyanine dye, an oxonol dye, a hemioxonol dye, and the like can be used. Useful sensitizing dyes for use in the present invention include, for example, RESEARCH DISCLOSURE
Item 17643 IV-A (p.23, December 1978), Item 1831X (1973
P.437, Aug. 09). Especially various laser imagers, scanners,
A sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of a light source of an image setter or a plate making camera can be advantageously selected.

As an example of spectral sensitization to red light, He-Ne
For a so-called red light source such as a laser, a red semiconductor laser or an LED, a compound of I-1 to I-38 described in JP-A-54-18726, and a compound of I-1 described in JP-A-6-75322. I-3
5 and the compounds I-1 to I- described in JP-A-7-287338.
34 compounds, dyes 1 to 20 described in JP-B-55-39818,
The compounds I-1 to I-37 described in JP-A-62-284343 and the compounds I-1 to I-34 described in JP-A-7-287338 are advantageously selected.

For semiconductor laser light sources in the 750-1400 nm wavelength range, various known dyes, including cyanine, merocyanine, styryl, hemicyanine, oxonol, hemioxonol and xanthene dyes,
Sensitization can be advantageously performed spectrally. Useful cyanine dyes are, for example, cyanine dyes having basic nuclei such as thiazoline nuclei, oxazoline nuclei, pyrroline nuclei, pyridine nuclei, oxazole nuclei, thiazole nuclei, selenazole nuclei and imidazole nuclei. Preferred useful merocyanine dyes include, in addition to the above basic nuclei, acidic nuclei such as thiohydantoin nucleus, rhodanine nucleus, oxazolidinedione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus. Including. Among the above cyanine and merocyanine dyes, those having an imino group or a carboxyl group are particularly effective. For example, U.S. Patent 3,761,279,
3,719,495 and 3,877,943, British Patent 1,466,201
No. 1,469,117, No. 1,422,057, Tokuhei 3-10391
No. 6-52387, JP-A-5-341432, 6-94781,
It may be appropriately selected from known dyes as described in JP-A-6-301141.

Particularly preferred as the structure of the dye used in the present invention is a cyanine dye having a thioether bond-containing substituent (for example, see JP-A-62-58239 and JP-A-3-13863).
No.8, No.3-138642, No.4-255840, No.5-72659, No.5-
72661, 6-222491, 2-230506, 6-258757
No., 6-317868, 6-324425, Tokuyohei 7-500926,
Dyes described in U.S. Pat.No. 5,541,054), dyes having a carboxylic acid group (for example, JP-A-3-163440, 6-30114
No. 1, U.S. Pat.No. 5,441,899), merocyanine dyes, polynuclear merocyanine dyes and polynuclear cyanine dyes
(JP 47-6329, JP 49-105524, JP 51-127719, JP
52-80829, 54-61517, 59-214846, 60-6750
No. 63-159841, JP-A-6-35109, JP-A-6-59381,
Nos. 7-146537, 7-46537, JP-T-55-50111, British Patent 1,467,638, and US Pat. No. 5,281,515).

Further, dyes described in Example 5 of US Pat. Nos. 5,510,236 and 3,871,887 as dyes forming a J-band,
JP-A-2-96131 and JP-A-59-48753 are disclosed and can be preferably used in the present invention.

In the present invention, merocyanine-based dyes, which are conventionally weakly adsorbed and hardly used for addition before chemical sensitization, are particularly preferred.

These sensitizing dyes may be used alone.
Two or more kinds may be used in combination. Combinations of sensitizing dyes are often used, especially for supersensitization. Along with the sensitizing dye, the emulsion may contain a dye which does not itself have a spectral sensitizing effect or a substance which does not substantially absorb visible light and exhibits supersensitization.

Useful sensitizing dyes, combinations of dyes exhibiting supersensitization and substances exhibiting supersensitization are described in Research Disclosure 17
Vol. 6, 17643 (issued in December 1978), page 23, IV, J, or JP-B Nos. 49-25500, 43-4933, JP-A-59-19032, 5
No. 9-192242.

The sensitizing dyes may be added to the silver halide emulsion by dispersing them directly in the emulsion or by adding water, methanol, ethanol, propanol, acetone, methylcellosolve, 2,2, 3,3-tetrafluoropropanol, 2,2,2-trifluoroethanol, 3-methoxy
It may be added to the emulsion by dissolving it in a solvent such as 1-propanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol, N, N-dimethylformamide, alone or in a mixed solvent.

As disclosed in US Pat. No. 3,469,987, a dye is dissolved in a volatile organic solvent, the solution is dispersed in water or a hydrophilic colloid, and this dispersion is dispersed in an emulsion. To Japanese Patent Publication No. 44-23389,
As disclosed in 44-27555, 57-22091, etc.,
A method in which a dye is dissolved in an acid and the solution is added to the emulsion, or a method in which an acid or a base is added to the emulsion as an aqueous solution in the coexistence thereof, as disclosed in U.S. Pat.Nos. 3,822,135 and 4,006,025, etc. A method of adding an aqueous solution or a colloidal dispersion in the presence of a surfactant to an emulsion, as disclosed in JP-A-53-102733 and JP-A-58-105141. Is directly dispersed, and the dispersion is added to the emulsion, as disclosed in JP-A-51-74624, the dye is dissolved using a compound that causes a red shift, and the solution is added to the emulsion. Can be used. Also, ultrasonic waves can be used for the solution.

The sensitizing dye to be used in the present invention may be added to the silver halide emulsion of the present invention at any time during the preparation of the emulsion which has been found to be useful. For example, U.S. Patents 2,735,766 and 3,628,960,
4,183,756, 4,225,666, JP-A-58-184142,
As disclosed in the specification of JP-A-60-196749 and the like, the timing before the step of forming silver halide grains and / or before desalting, during and / or after desalting and before the start of chemical ripening. As disclosed in the specification such as JP-A-58-113920, any time immediately before the chemical ripening or during the process, after the chemical ripening, and before the application of the emulsion before coating, It may be added during the process.
Further, as disclosed in the specification of U.S. Pat. No. 4,225,666, JP-A-58-7629, etc., the same compound may be used alone or in combination with a compound having a different structure, for example, during the particle forming step. The compound may be divided and added during the ripening step or after the completion of the chemical ripening, or may be added separately before or during the chemical ripening or after the completion of the chemical ripening. May be added.

Although various addition methods can be adopted as described above, it is necessary to add the dye so that the dye is present at the time of chemical sensitization.

The amount of the sensitizing dye used in the present invention may be a desired amount according to the performance such as sensitivity and fogging, but is preferably from 10 ^-4 to 10 ^-1 mol per mol of silver halide in the photosensitive layer. Is preferably 10 ^-3 to 10 ^-1 mol, and 2 × 10 ^{-3 to} 5 × 10
^-2 mol is more preferred.

<Adsorbed Substances / Anti-Fogging Agent on Silver Halide Surface> Examples of the adsorbed substances on the silver halide surface in the present invention include anti-fogging agents.

The silver halide emulsion or //
And organic silver salts can be further protected against the formation of additional fog by antifoggants, stabilizers and stabilizer precursors, and can be stabilized against reduced sensitivity during inventory storage. Suitable antifoggants, stabilizers and stabilizer precursors which can be used alone or in combination are the thiazonium salts described in U.S. Pat.Nos. 2,131,038 and 2,694,716; U.S. Pat.Nos. 2,886,437 and 2, 44
Azaindene described in 4,605, mercury salt described in U.S. Pat.No. 2,728,663, urazole described in U.S. Pat.No. 3,287,135, sulfocatechol described in U.S. Pat. , Nitroindazole, polyvalent metal salts described in U.S. Pat.No. 2,839,405, thiuronium salts described in U.S. Pat.No. 3,220,839, and palladium, platinum and gold salts described in U.S. Pat.Nos. 2,566,263 and 2,597,915,
Halogen-substituted organic compounds described in U.S. Pat.Nos. 4,108,665 and 4,442,202, U.S. Pat.Nos. 4,128,557 and 4,137,079, 4,138,365 and 4,459,35
No. 0 and the phosphorus compounds described in US Pat. No. 4,411,985.

In the present invention, a mercapto compound, a disulfide compound, and a thione compound are contained in order to control development by suppressing or accelerating development, to improve spectral sensitization efficiency, and to improve storage stability before and after development. be able to.

When a mercapto compound is used in the present invention, it may have any structure, but it may be Ar-SM, Ar-SSA
Those represented by r are preferred. Wherein M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic or fused aromatic ring having one or more nitrogen, sulfur, oxygen, selenium or tellurium atoms. Preferably, the heteroaromatic ring is benzimidazole, naphthimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzotellurazole, imidazole, oxazole, pyrazole, triazole, thiadiazole, tetrazole, triazine, pyrimidine, pyridazine , Pyrazine, pyridine, purine, quinoline or quinazolinone. The heteroaromatic ring includes, for example, halogens (e.g., Br and Cl), hydroxy, amino, carboxy, alkyl (e.g., those having one or more carbon atoms, preferably 1-4 carbon atoms) and alkoxy ( For example, it may have a substituent selected from the group consisting of one or more carbon atoms, preferably those having 1 to 4 carbon atoms. As mercapto-substituted heteroaromatic compounds, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-mercapto-5-methylbenzimidazole, 6-ethoxy-2-mercaptobenzothiazole, 2, 2'-dithiobis- (benzothiazole, 3-mercapto-1,2,4-triazole, 4,5-diphenyl-2-imidazolethiol, 2-mercaptoimidazole, 1-ethyl-2-mercaptobenzimidazole, 2-mercapto Quinoline, 8-mercaptopurine, 2-mercapto-4 (3H) -quinazolinone, 7-trifluoromethyl-4-quinolinethiol, 2,3,5,6-tetrachloro-4-pyridinethiol, 4-amino-6 -Hydroxy-2-mercaptopyrimidine monohydrate 2-amino-5-mercapto-1,3,4-thiadiazole, 3-amino-5-mercapto-1,2,4-triazole, 4-hydrocyanic acid
2-mercaptopyrimidine, 2-mercaptopyrimidine,
4,6-diamino-2-mercapto, pyrimidine, 2-mercapto-4-methylpyrimidine hydrochloride, 3-mercapto-
Examples thereof include 5-phenyl-1,2,4-triazole and 2-mercapto-4-phenyloxazole, but the present invention is not limited thereto.

The substances adsorbed on these silver halide surfaces are:
In the case where they are not present, it is desirable to use them in an amount that does not reduce the ionic conductivity of the particles to 1/10 or less. That is, it is preferable that the photothermographic material of the present invention does not contain a substance adsorbed on the surface of the silver halide in an amount exceeding the amount that reduces the ionic conductivity of the photosensitive silver halide emulsion to 1/10 or less.

To define the preferred use range by the amount,
It is difficult because the amount of organic silver salt such as silver behenate varies depending on the coating amount.
1 × 10 ⁻⁶ to 1 × 10 ⁻² mol, preferably 5 × 10 ⁻⁵ to
An amount of 5 × 10 ⁻³ mol.

<Regarding the Organic Silver Salt of the Present Invention> The organic silver salt that can be used in the present invention is relatively stable to light, but is exposed to a photocatalyst (such as a latent image of photosensitive silver halide). And a silver salt that forms a silver image when heated to 80 ° C. or higher in the presence of a reducing agent. The organic silver salt can be any organic substance including a source capable of reducing silver ions. Silver salts of organic acids, in particular silver salts of long-chain fatty carboxylic acids (with 10 to 30, preferably 15 to 28 carbon atoms) are preferred.
Also preferred are organic or inorganic silver salt complexes in which the ligand has a complex stability constant in the range of 4.0 to 10.0. The silver donor material can preferably comprise about 5-70% by weight of the imaging layer. Preferred organic silver salts include silver salts of organic compounds having a carboxyl group. Examples of these include, but are not limited to, silver salts of aliphatic carboxylic acids and silver salts of aromatic carboxylic acids. Preferred examples of the silver salt of an aliphatic carboxylic acid include silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate,
Silver myristate, silver palmitate, silver maleate, silver fumarate, silver tartrate, silver linoleate, silver butyrate and silver camphorate, and mixtures thereof.

The organic acid silver preferably used in the present invention is
It is prepared by reacting silver nitrate with an alkali metal salt (eg, Na salt, K salt, Li salt, etc.) solution or suspension of the organic acid described above. The alkali metal salt of an organic acid of the present invention is obtained by treating the above organic acid with an alkali. The organic acid silver salt of the present invention can be performed palindrically or continuously in any suitable container. The stirring in the reaction vessel can be performed by any stirring method depending on the required characteristics of the particles. The silver salt of an organic acid can be prepared by gradually or rapidly adding an aqueous solution of silver nitrate to a reaction vessel containing a solution or suspension of an alkali metal salt of an organic acid, or by preparing an organic acid prepared in advance in a reaction vessel containing an aqueous solution of silver nitrate. Preferably, a method of gradually or rapidly adding an alkali metal salt solution or suspension, and a method of simultaneously adding a previously prepared aqueous solution of silver nitrate and a solution or suspension of an organic acid alkali metal salt into a reaction vessel are preferably used. Can be.

The silver nitrate aqueous solution and the organic acid alkali metal salt solution or suspension may be of any concentration for controlling the particle size of the organic acid silver, and may be added at any addition rate. it can. The silver nitrate aqueous solution and the organic acid alkali metal salt solution or suspension can be added by a method of adding at a constant addition rate, an accelerated addition method by an arbitrary time function, or a deceleration addition method. Also, the reaction solution may be added to the liquid surface,
Further, it may be added to the liquid. In the case of a method in which a previously prepared aqueous silver nitrate solution and an organic acid alkali metal salt solution or suspension are simultaneously added to the reaction vessel, either the silver nitrate aqueous solution or the organic acid alkali metal salt solution or suspension is preceded. Although it can be added, it is preferable to add the silver nitrate aqueous solution in advance. The degree of precedence is preferably from 0 to 50% of the total added amount, particularly preferably from 0 to 25%. Further, as described in JP-A-9-127643, a method of adding while controlling the pH or silver potential of the reaction solution during the reaction can be preferably used.

The added aqueous solution of silver nitrate or the solution or suspension of the organic acid alkali metal salt depends on the required properties of the particles.
pH can be adjusted. Any acid or alkali can be added for pH adjustment. Depending on the required characteristics of the particles, for example, the temperature in the reaction vessel can be arbitrarily set for controlling the particle size of the organic silver salt to be adjusted. Alternatively, the suspension can also be adjusted to any temperature. The organic acid alkali metal salt solution or suspension is preferably heated and kept at 50 ° C. or higher in order to ensure fluidity of the solution.

The organic acid silver used in the present invention is preferably prepared in the presence of a tertiary alcohol. The tertiary alcohol used in the present invention is preferably one having a total carbon number of 15 or less,
Particularly preferred is 0 or less. Preferred examples of the tertiary alcohol include tert-butanol, but the present invention is not limited thereto.

The tertiary alcohol used in the present invention may be added at any time during the preparation of the silver salt of the organic acid, but may be added during the preparation of the alkali metal salt of the organic acid to dissolve the alkali metal salt of the organic acid. Is preferred. The amount of the tertiary alcohol of the present invention can be arbitrarily used in a weight ratio of 0.01 to 10 with respect to H2O as a solvent at the time of preparing the silver salt of organic acid. Is preferable.

A silver salt of a compound containing a mercapto group or a thione group and derivatives thereof can also be used. Preferred examples of these compounds include 3-mercapto-4-
Silver salt of phenyl-1,2,4-triazole, silver salt of 2-mercaptobenzimidazole, silver salt of 2-mercapto-5-aminothiadiazole, silver salt of 2- (ethylglycolamide) benzothiazole, S-alkylthio Silver salts of thioglycolic acid such as silver salts of glycolic acid (where the alkyl group has 12 to 22 carbon atoms); silver salts of dithiocarboxylic acids such as silver salts of dithioacetic acid; silver salts of thioamide; Silver salt of carboxyl-1-methyl-2-phenyl-4-thiopyridine,
Silver salts of mercaptotriazine, silver salts of 2-mercaptobenzoxazole, silver salts described in U.S. Pat.No.4,123,274, such as 1,2, such as silver salts of 3-amino-5-benzylthio-1,2,4-thiazole , 4-silver salts of mercaptothiazole derivatives, including silver salts of thione compounds such as silver salt of 3- (3-carboxyethyl) -4-methyl-4-thiazoline-2-thione described in U.S. Patent No. 3,301,678. . Furthermore, compounds containing an imino group can also be used. Preferred examples of these compounds include silver salts of benzotriazole and derivatives thereof, for example, silver salts of benzotriazole such as silver methylbenzotriazole, silver salts of halogen-substituted benzotriazole such as silver 5-chlorobenzotriazole, and US Pat. No. 4,220,709, silver salts of 1,2,4-triazole or 1-H-tetrazole, and silver salts of imidazole and imidazole derivatives. For example, U.S. Pat.
Various silver acetylide compounds as described in 1,361 and 4,775,613 can also be used.

The shape of the organic silver salt that can be used in the present invention is not particularly limited, but a needle crystal having a short axis and a long axis is preferable. In the present invention, the minor axis is preferably from 0.01 μm to 0.20 μm, the major axis is preferably from 0.10 μm to 5.0 μm, and the minor axis is from 0.01 μm to 0.15 μm,
The major axis is more preferably 0.10 μm or more and 4.0 μm or less. The particle size distribution of the organic silver salt is preferably monodispersed. The monodispersion is preferably 100% or less, more preferably 80% or less, and still more preferably 50% of a value obtained by dividing the standard deviation of the length of each of the short axis and the long axis by each of the short axis and the long axis. It is as follows. The shape of the organic silver salt can be measured from a transmission electron microscope image of the organic silver salt dispersion. As another method of measuring monodispersity, there is a method of calculating the standard deviation of the volume-weighted average diameter of the organic silver salt, and the percentage (coefficient of variation) divided by the volume-weighted average diameter is preferably 100% or less, more preferably Preferably 80% or less,
More preferably, it is 50% or less. As a measuring method, for example, a particle size (volume weighted average diameter) obtained by irradiating a laser beam to an organic silver salt dispersed in a liquid and obtaining an autocorrelation function with respect to a time change of fluctuation of the scattered light.
Can be obtained from

The organic silver salt that can be used in the present invention includes:
Preferably, desalting can be performed. The method for desalting is not particularly limited, and a known method can be used. However, a known filtration method such as centrifugal filtration, suction filtration, ultrafiltration, or floc-forming water washing by a coagulation method can be preferably used.

In the present invention, in order to obtain a solid dispersion of an organic silver salt having a high S / N, a small particle size, and no aggregation, an organic silver salt which is an image forming medium and a photosensitive silver salt are substantially contained. It is preferable to use a dispersion method in which a water dispersion liquid which is not included in the liquid is converted into a high-speed flow and then the pressure is reduced.

After passing through such steps, the mixture is mixed with a photosensitive silver salt aqueous solution to prepare a photosensitive image forming medium coating solution. When a photothermographic material is prepared using such a coating solution, a high-sensitivity photothermographic material having low haze, low coverage and high sensitivity can be obtained. On the other hand, when the photosensitive silver salt is coexistent when the light is converted into a high-pressure, high-speed flow and dispersed, the fogging increases and the sensitivity remarkably decreases. When an organic solvent is used instead of water as a dispersion medium, haze increases, fogging increases, and sensitivity tends to decrease. On the other hand, when a conversion method for converting a part of the organic silver salt in the dispersion to the photosensitive silver salt is used instead of the method of mixing the aqueous solution of the photosensitive silver salt, the sensitivity is reduced.

In the above, the aqueous dispersion converted and converted to high pressure and high speed is substantially free of a photosensitive silver salt, and has a water content relative to that of a non-photosensitive organic silver salt. 0.
The content is 1 mol% or less, and the photosensitive silver salt is not positively added.

In the present invention, the solid dispersion apparatus and the technique used for carrying out the dispersion method as described above are described in, for example, “Dispersion Rheology and Dispersion Technique” (Toshio Kajiuchi, Hiroki Usui, 1991, Shinzansha Publishing Co., Ltd., p357
-P403), "The 24th Progress of Chemical Engineering", edited by The Society of Chemical Engineers, Tokai Branch, 1990, Maki Shoten, p184-p185),
Although detailed in the dispersing method of the present invention, the aqueous dispersion containing at least an organic silver salt is pressurized by a high-pressure pump or the like and sent into a pipe, and then passed through a narrow slit provided in the pipe, Thereafter, the dispersion is finely dispersed by causing an abrupt pressure drop in the dispersion.

The high-pressure homogenizer to which the present invention relates is generally composed of (a) a "shear force" generated when the dispersoid passes through a narrow gap at a high pressure and a high speed, and (b) a dispersoid is supplied from a high pressure to a normal pressure. It is considered that the particles are dispersed into fine particles by a dispersing force such as "cavitation force" generated when the particles are released. As an example of this type of dispersing apparatus, a Gaulin homogenizer is mentioned in the past.In this apparatus, the liquid to be dispersed sent at a high pressure is converted into a high-speed flow through a narrow gap on a cylindrical surface, and the force is applied to the surrounding wall by the force. The particles collide and are emulsified and dispersed by the impact force. Working pressure is generally 1
100-600 kg / cm ² , the flow rate is in the range of several meters to 30 m / sec, and in order to increase the dispersion efficiency, a high flow rate part is made into a saw-tooth shape to increase the number of collisions. I have. On the other hand, in recent years, devices capable of dispersing at higher pressure and higher flow rate have been developed, and a typical example thereof is a microfluidizer (Microfluidex.
International Corporation), Nanomizer (Special Kika Kogyo Co., Ltd.) and the like.

Examples of the dispersing apparatus suitable for the present invention include a microfluidizer M-110S-EH (with a G10Z interaction chamber), M-110Y (with a H10Z interaction chamber), and a microfluidizer manufactured by Microfluidics International Corporation. -140K (with G10Z interaction chamber), HC-5000 (with L30Z or H230Z interaction chamber), HC-8000 (with E230Z or L3
0Z interaction chamber).

Using these devices, an aqueous dispersion containing at least an organic silver salt is pressurized by a high-pressure pump or the like and fed into a pipe, and then passed through a narrow slit provided in the pipe to obtain a desired pressure. Is applied, and thereafter, the pressure in the pipe is rapidly returned to the atmospheric pressure, or the like, and a sudden pressure drop is caused in the dispersion to obtain an organic silver salt dispersion optimal for the present invention. .

It is preferable that the raw material liquid is preliminarily dispersed before the dispersion operation. As means for preliminary dispersion, known dispersion means (e.g., high-speed mixer, homogenizer, high-speed impact mill, Banbury mixer, homomixer, kneader, ball mill, vibration ball mill, planetary ball mill, attritor, sand mill, bead mill, colloid mill,
Jet mill, roller mill, tron mill, high-speed stone mill) can be used. Instead of mechanically dispersing, fine particles may be formed by coarsely dispersing in a solvent by controlling the pH and then changing the pH in the presence of a dispersing agent. At this time, an organic solvent may be used as a solvent used for the coarse dispersion, and the organic solvent is usually removed after the completion of the fine particle formation.

In the organic silver salt dispersion of the present invention, the flow rate,
It is possible to disperse to a desired particle size by adjusting the pressure difference at the time of pressure drop and the number of treatments, but from the viewpoint of photographic characteristics and particle size, the flow rate is 200 m / sec to 600 m / sec, The pressure is preferably in the range of 900 to 3000 kg / cm ² , the flow rate is more preferably in the range of 300 to 600 m / sec, and the differential pressure at the time of pressure drop is more preferably in the range of 1500 to 3000 kg / cm ² . The number of times of dispersion processing can be selected as needed, but usually 1 to 10 times is selected, but from the viewpoint of productivity, about 1 to 3 times is selected. It is not preferable to raise the temperature of such an aqueous dispersion under high pressure from the viewpoints of dispersibility and photographic properties. At a temperature higher than 90 ° C., the particle size tends to increase and the fogging tends to increase. is there. Therefore, in the present invention, the high pressure,
A step before the conversion to a high flow rate or a step after the pressure is reduced, or both of these steps include a cooling step, and the temperature of such water dispersion is kept in the range of 5 to 90 ° C. by the cooling step. Preferably, more preferably 5-
It is preferable that the temperature is kept in the range of 80 ° C, particularly in the range of 5 to 65 ° C. In particular, it is effective to provide the above cooling step at the time of high pressure dispersion in the range of 1500 to 3000 kg / cm ² . As the cooler, a double tube, a double tube using a static mixer, a multi-tube heat exchanger, a coiled tube heat exchanger, or the like can be appropriately selected according to the required heat exchange amount. Further, in order to increase the efficiency of heat exchange, it is sufficient to select a suitable one such as a pipe thickness, a wall thickness and a material in consideration of a working pressure. The refrigerant used for the cooler is 20
Well water at 5 ° C., cold water at 5 to 10 ° C. treated with a refrigerator, or a refrigerant such as ethylene glycol / water at −30 ° C. can be used if necessary.

In the dispersion operation of the present invention, it is preferable to disperse the organic silver salt in the presence of an aqueous solvent-soluble dispersant (dispersion aid). Examples of the dispersing agent include polyacrylic acid, a copolymer of acrylic acid, a maleic acid copolymer, a maleic acid monoester copolymer, a synthetic anionic polymer such as an acrylomethylpropanesulfonic acid copolymer, and carboxymethyl. Starch, semi-synthetic anionic polymers such as carboxymethyl cellulose, alginic acid, anionic polymers such as pectic acid, the compounds described in JP-A-7-350753, or known anionic, nonionic, cationic surfactants and other polyvinyl Known polymers such as alcohol, polyvinylpyrrolidone, carboxymethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose, and naturally occurring polymer compounds such as gelatin can be appropriately selected and used. Le compounds, particularly preferred water-soluble cellulose derivatives.

It is a general method to mix a dispersion aid with an organic silver salt powder or an organic silver salt in a wet cake state before dispersion and to send the mixture as a slurry to a dispersing machine. Heat treatment or treatment with a solvent may be performed in the combined state to obtain an organic silver salt powder or a wet cake. The pH may be controlled by a suitable pH adjuster before, during or after dispersion.

In addition to the mechanical dispersion, the particles may be coarsely dispersed in a solvent by controlling the pH, and then the pH may be changed in the presence of a dispersing aid to form fine particles. At this time, an organic solvent may be used as a solvent used for the coarse dispersion, and the organic solvent is usually removed after the completion of the fine particle formation.

The prepared dispersion is stored with stirring for the purpose of suppressing sedimentation of fine particles during storage, or stored in a highly viscous state (for example, in a jelly state using gelatin) by means of a hydrophilic colloid. You can also do.
Further, a preservative can be added for the purpose of preventing the propagation of various bacteria during storage.

The particle size (average volume weight diameter) of the organic silver salt solid fine particle dispersion of the present invention is determined, for example, by irradiating a solid fine particle dispersion dispersed in a liquid with a laser beam and changing the fluctuation of the scattered light with time. It can be obtained from the particle size (volume weight average diameter) obtained by obtaining the autocorrelation function. A solid fine particle dispersion having an average particle size of 0 μm or more and 10.0 μm or less is preferable. The average particle size is more preferably 0.1 μm or more and 5.0 μm or less, and even more preferably the average particle size is 0.1 μm or more and 2.0 μm or less.

The particle size distribution of the organic silver salt is preferably monodispersed. Specifically, the percentage of the standard deviation of the volume load average diameter divided by the volume load average diameter (coefficient of variation)
Is at most 80%, more preferably at most 50%, even more preferably at most 30%.

The shape of the organic silver salt can be measured from a transmission electron microscope image of the organic silver salt dispersion.

<Reducing Agent for Silver Ions> The photothermographic material of the present invention preferably contains a reducing agent for an organic silver salt. The reducing agent for the organic silver salt may be any substance that reduces silver ions to metallic silver, preferably an organic substance. Conventional photographic developers such as phenidone, hydroquinone and catechol are useful, but hindered phenol reducing agents are preferred. The reducing agent is preferably contained in an amount of 5 to 50% by mole, more preferably 10 to 40% by mole, based on 1 mole of silver on the surface having the image forming layer. The layer to which the reducing agent is added may be any layer on the side having the image forming layer. When it is added to a layer other than the image forming layer, it is preferable to use a relatively large amount of 10 to 50 mol% based on 1 mol of silver. Further, the reducing agent may be a so-called precursor which is derivatized so as to have a function effectively only during development.

In photothermographic materials utilizing organic silver salts, a wide range of reducing agents are disclosed in JP-A-46-6074 and JP-A-47-1238.
47-33621, 49-46427, 49-115540, 50-14
No. 334, No. 50-36110, No. 50-147711, No. 51-32632,
No. 51-1023721, No. 51-32324, No. 51-51933, No. 52-8
4727, 55-108654, 56-146133, 57-82828
No. 57-82829, JP-A-6-3793, U.S. Pat.
No. 86, No. 3,679,426, No. 3,751,252, No. 3,751,255
Nos. 3,761,270, 3,782,949, 3,839,048,
3,928,686, 5,464,738, German patent 2321328,
It is disclosed in European Patent No. 692732 and the like. For example, phenylamide oxime, 2-thienylamide oxime and
amide oximes such as p-phenoxyphenylamide oxime; azines such as 4-hydroxy-3,5-dimethoxybenzaldehyde azine; combinations of 2,2′-bis (hydroxymethyl) propionyl-β-phenylhydrazine with ascorbic acid Combinations of such aliphatic carboxylic acid aryl hydrazides with ascorbic acid; polyhydroxybenzene, hydroxylamine, reductone and / or
Or a combination of hydrazines (e.g., hydroquinone,
Bis (ethoxyethyl) hydroxylamine, piperidinohexose reductone or a combination of formyl-4-methylphenylhydrazine); hydroxamic acids such as phenylhydroxamic acid, p-hydroxyphenylhydroxamic acid and β-alinine hydroxamic acid; Combinations of azines and sulfonamidophenols (e.g., phenothiazine and 2,6-dichloro-4-benzenesulfonamidophenol); alphas such as ethyl-α-cyano-2-methylphenyl acetate, ethyl-α-cyanophenyl acetate -Cyanophenylacetic acid derivative; 2,2'-dihydroxy-1,
1'-binaphthyl, 6,6'-dibromo-2,2'-dihydroxy-
Bis-β-naphthol as exemplified by 1,1′-binaphthyl and bis (2-hydroxy-1-naphthyl) methane; bis-β-naphthol and 1,3-dihydroxybenzene derivatives
(E.g., 2,4-dihydroxybenzophenone or 2 ',
4-pyrazolone, such as 3-methyl-1-phenyl-5-pyrazolone;
Reductones as exemplified by dimethylaminohexose reductone, anhydrodihydroaminohexose reductone and anhydrodihydropiperidone hexose reductone; 2,6-dichloro-4-benzenesulfonamidophenol and p-benzenesulfone Sulfonamidophenol reducing agents such as amidophenol; 2-phenylindane-1,3-dione; 2,2-dimethyl-7-t-butyl-
Chromans such as 6-hydroxychroman; 2,6-dimethoxy
1, such as -3,5-dicarbethoxy-1,4-dihydropyridine
4-dihydropyridine; bisphenol (eg, bis (2-
(Hydroxy-3-t-butyl-5-methylphenyl) methane, 2,2
-Bis (4-hydroxy-3-methylphenyl) propane, 4,4-
Ethylidene-bis (2-t-butyl-6-methylphenol),
1,1, -bis (such as 2-hydroxy-3,5-dimethylphenyl-3,5,5-trimethylhexane and 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propanol); ascorbic acid Derivatives (eg, 1-ascorbyl palmitate, ascorbyl stearate, etc.); and aldehydes and ketones, such as benzyl and biacetyl; 3-pyrazolidones and certain indan-1,3-diones; Particularly preferred reducing agents are bisphenol and chromanol.

The reducing agent of the present invention may be added by any method such as a solution, a powder, and a dispersion of solid fine particles. The dispersion of the solid fine particles is carried out by a known means for making fine (for example, a ball mill, a vibration ball mill, a sand mill, a colloid mill, a jet mill, a roller mill, etc.). When dispersing the solid fine particles, a dispersing aid may be used.

<Toning Agent> When an additive known as a “toning agent” for improving an image is included, the optical density may be increased. The toning agent may also be advantageous in forming a black silver image. The toning agent is preferably contained in an amount of 0.1 to 50 mol% per mol of silver, more preferably 0.5 to 20 mol%, on the surface having the image forming layer. Further, the toning agent may be a so-called precursor which is derivatized so as to have a function effectively only during development.

In a photothermographic material using an organic silver salt, a wide range of color toning agents are disclosed in JP-A-46-6077 and JP-A-47-10282.
Nos. 49-5019, 49-5020, 49-91215, 49-9
No. 1215, No. 50-2524, No. 50-32927, No. 50-67132,
No. 50-67641, No. 50-114217, No. 51-3223, No. 51-279
No. 23, No. 52-14788, No. 52-99813, No. 53-1020, No. 5
3-76020, 54-156524, 54-156525, 61-1836
No. 42, JP-A-4-56848, JP-B-49-10727, 54-2033
No. 3, U.S. Pat.Nos. 3,080,254, 3,446,648, 3,782,9
No. 41, No. 4,123,282, No. 4,510,236, British Patent 138079
No. 5, Belgian Patent No. 841910 and the like. Examples of toning agents are phthalimide and N-hydroxyphthalimide; succinimide, pyrazolin-5-one and quinazolinone, 3-phenyl-2-pyrazolin-5-one, 1-phenylurazole, quinazoline and 2,4-thiazolidinedione Cyclic imides such as; naphthalimides (eg, N
-Hydroxy-1,8-naphthalimide); cobalt complexes (eg, cobalt hexamine trifluoroacetate); 3-
Mercapto-1,2,4-triazole, 2,4-dimercaptopyrimidine, 3-mercapto-4,5-diphenyl-1,2,4-triazole and 2,5-dimercapto-1,3,4-thiadiazole N- (aminomethyl) aryldicarboximides, such as (N, N-dimethylaminomethyl) phthalimide and N, N- (dimethylaminomethyl) -naphthalene-2,3-dicarboximide ); And blocked pyrazoles, isothiuronium derivatives and certain photobleaching agents (eg, N, N'-hexamethylenebis (1-
Carbamoyl-3,5-dimethylpyrazole), 1,8- (3,6-diazaoctane) bis (isothiuronium trifluoroacetate) and 2-tribromomethylsulfonyl)-(benzothiazole)); and 3-ethyl- 5 [(3-ethyl-2-benzothiazolinylidene) -1-methylethylidene] -2-thio-2,4
-Oxazolidinedione; phthalazinone, phthalazinone derivative or metal salt, or 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione A combination of phthalazinone and a phthalic acid derivative (for example, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride, etc.); phthalazine,
Phthalazine derivatives or metal salts, or derivatives such as 4- (1-naphthyl) phthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine and 2,3-dihydrophthalazine; phthalazine and phthalic acid derivatives (for example, phthalic acid) Acid, 4
-Methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride); quinazolinedione,
Benzoxazine or naphthoxazine derivatives; rhodium complexes that function not only as color tone regulators but also in-situ as sources of halide ions for silver halide formation, such as ammonium hexachlororhodate (III), rhodium bromide, rhodium nitrate And potassium hexachlororhodate (III); inorganic peroxides and persulfates, such as ammonium disulfide and hydrogen peroxide; 1,3-benzoxazine-2,4-dione, 8-methyl-
1,3-benzoxazine-2,4-dione and 6-nitro-1,3-
Benzoxazines such as benzoxazine-2,4-dione
2,4-dione; pyrimidine and asymmetric-triazine (eg, 2,4-dihydroxypyrimidine, 2-hydroxy-4-aminopyrimidine, etc.), azauracil, and tetraazapentalene derivatives (eg, 3,6-dimercapto- 1,4-diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene, and 1,4-di (o-chlorophenyl) -3,6-dimercapto-1H, 4
H-2,3a, 5,6a-tetraazapentalene).

The color-toning agent of the present invention may be added by any method such as a solution, a powder and a dispersion of solid fine particles. The dispersion of the solid fine particles is carried out by a known means for making fine (for example, a ball mill, a vibration ball mill, a sand mill, a colloid mill, a jet mill, a roller mill, etc.). When dispersing the solid fine particles, a dispersing aid may be used.

<Other Preferred Embodiments> The ion-adhesive antifogging agent for silver halide surfaces preferably used in the present invention is an organic halide.
50-119624, 50-120328, 51-121332, 54-58
No. 022, No. 56-70543, No. 56-99335, No. 59-90842,
Nos. 61-129642, 62-129845, JP-A-6-208191,
Nos. 7-5621, 7-2781, 8-15809, U.S. Pat.
Compounds such as those disclosed in JP-A Nos. 12, 5369000 and 5464737 can be mentioned.

The anti-fogging agent of the present invention may be added by any method such as a solution, a powder, and a dispersion of solid fine particles. Solid fine particle dispersion is known micronization means (for example, ball mill,
Vibration ball mill, sand mill, colloid mill, jet mill, roller mill, etc.). When dispersing the solid fine particles, a dispersing aid may be used.

Although not required to practice the present invention,
It may be advantageous to add mercury (II) salts as antifoggants to the emulsion layers. Preferred mercury (II) salts for this purpose are mercury acetate and mercury bromide. The amount of mercury used in the present invention is preferably 1 to 1 mol of silver applied.
The range is from × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol, more preferably from 1 × 10 ⁻⁹ mol to 1 × 10 ⁻⁴ mol.

The photothermographic material of the present invention may contain benzoic acids for the purpose of increasing the sensitivity and preventing fogging.

The benzoic acids of the present invention may be any benzoic acid derivatives. Examples of preferred structures include those described in US Pat.
4,784,939, 4,152,160, Japanese Patent Application No. 8-151242, 8-
Compounds described in Nos. 151241 and 8-98051 are exemplified. The benzoic acids of the present invention may be added to any part of the light-sensitive material. However, the added layer is preferably added to a layer having a light-sensitive layer, more preferably to an organic silver salt-containing layer. . The addition time of the benzoic acids of the present invention may be performed in any step of the coating solution preparation,
When it is 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, but it is preferable after the preparation of the organic silver salt and immediately before the coating. The benzoic acid of the present invention may be added by any method such as powder, solution, and fine particle dispersion. Further, it may be added as a solution mixed with other additives such as a sensitizing dye, a reducing agent and a color tone agent. The benzoic acid of the present invention may be added in any amount,
1 × 10 ^-6 mol or more per mol is preferably 2 mol or less, 1 ×
It is more preferably from 10 ^-3 mol to 0.5 mol.

In the photosensitive layer according to the present invention, a polyhydric alcohol (for example, US Pat.
Glycerin and diols of the type described in U.S. Pat. No. 60,404), fatty acids or esters described in U.S. Pat. Nos. 2,588,765 and 3,121,060, and silicone resins described in British Patent No. 955,061.

The image forming material of the present invention may have a surface protective layer for the purpose of preventing adhesion of the image forming layer.

The binder for the surface protective layer of the present invention may be any polymer, but preferably contains a polymer having a carboxylic acid residue in an amount of 100 mg / m ^{2 to} 5 g / m ² . Examples of the polymer having a carboxyl residue include natural polymers (gelatin, alginic acid, etc.), modified natural polymers (carboxymethylcellulose, phthalated gelatin, etc.), synthetic polymers (polymethacrylate, polyacrylate, polyalkyl methacrylate / acrylate). Copolymer, polystyrene / polymethacrylate copolymer) and the like.

The carboxy residue content of the polymer is preferably from 1 × 10 ^-2 mol to 1.4 mol per 100 g of the polymer. Further, the carboxylic acid residue may form a salt with an alkali metal ion, an alkaline earth metal ion, an organic cation, or the like.

As the surface protective layer of the present invention, any anti-adhesion material may be used. Examples of anti-adhesion materials include waxes, silica particles, styrene-containing elastomeric block copolymers (e.g., styrene-butadiene-
Styrene, styrene-isoprene-styrene), cellulose acetate, cellulose acetate butyrate, cellulose propionate, and mixtures thereof. Further, a crosslinking agent for crosslinking and a surfactant for improving coating properties may be added to the surface protective layer.

In the image forming layer or the protective layer of the image forming layer in the present invention, US Pat. Nos. 3,253,921 and 2,27
It can be used in photographic elements containing light absorbing materials and filter dyes as described in 4,782, 2,527,583 and 2,956,879. Also, dyes can be mordanted, for example, as described in US Pat. No. 3,282,699. The amount of the filter dye used is preferably such that the absorbance at the exposure wavelength is 0.1 to 3.0, and 0.1.
2-1.5 is particularly preferred.

The image-forming layer or the image-forming layer of the emulsion layer according to the present invention may comprise a matting agent such as starch, titanium dioxide, zinc oxide, silica, of the type described in US Pat. Nos. 2,992,101 and 2,701,245. Polymer beads, including beads, can be included. The matte degree of the emulsion surface may be any value as long as stardust failure does not occur, but the Bekk smoothness is preferably from 200 seconds to 10,000 seconds, and particularly preferably from 300 seconds to 10,000 seconds.

The photothermographic material of the present invention is a so-called single-sided light-sensitive material having at least one photosensitive layer containing a silver halide emulsion on one side of a support and a back layer on the other side. Preferably, there is.

In the present invention, a matting agent may be added to the single-sided photosensitive material in order to improve transportability. The matting agent is generally fine particles of an organic or inorganic compound insoluble in water. Any matting agent can be used, for example, U.S. Patent Nos. 1,939,213, 2,701,245, and 2,322,037.
No. 3,262,782, No. 3,539,344, No. 3,767,448, etc.
2,192,241, 3,257,206, 3,370,951, 3,52
Inorganic matting agents well-known in the art, such as inorganic matting agents described in the respective specifications such as 3,022 and 3,769,020, can be used. For example, specifically, examples of organic compounds that can be used as a matting agent include, as examples of water-dispersible vinyl polymers, polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, acrylonitrile-α-methylstyrene copolymer, and polystyrene. , Styrene-divinylbenzene copolymer, polyvinyl acetate, polyethylene carbonate, polytetrafluoroethylene, etc., examples of cellulose derivatives such as methylcellulose,
Examples of starch derivatives such as cellulose acetate, cellulose acetate propionate, carboxy starch, carboxynitrophenyl starch, urea-formaldehyde-
Gelatin hardened with a known hardener such as a starch reactant and hardened gelatin obtained by coacervate hardening to form fine capsule hollow particles can be preferably used. As examples of the inorganic compound, silicon dioxide, titanium dioxide, magnesium dioxide, aluminum oxide, barium sulfate, calcium carbonate, silver chloride desensitized by a known method, silver bromide, and diatomaceous earth are preferably used. The above matting agents can be used by mixing different types of substances as necessary. The size and shape of the matting agent are not particularly limited, and those having an arbitrary particle size can be used.
In practicing the present invention, it is preferable to use one having a particle size of 0.1 μm to 30 μm. Further, the particle size distribution of the matting agent may be narrow or wide. On the other hand, since the matting agent greatly affects the haze and surface gloss of the light-sensitive material, the particle size, shape, and particle size distribution can be changed as necessary during the preparation of the matting agent or by mixing a plurality of matting agents. preferable.

In the present invention, the matte degree of the back layer is preferably such that the Beck smoothness is 250 seconds or less and 10 seconds or more.
More preferably, it is 180 seconds or less and 50 seconds or more.

In the present invention, the matting agent is preferably contained in the outermost surface layer of the light-sensitive material, a layer functioning as the outermost surface layer, or a layer close to the outer surface. It is preferable to be contained.

In the present invention, suitable binders for the back layer are transparent or translucent, generally colorless, and include natural polymer synthetic resins, polymers and copolymers, and other film-forming media such as gelatin, gum arabic,
Poly (vinyl alcohol), hydroxyethylcellulose, cellulose acetate, cellulose acetate butyrate, poly (vinylpyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid) ), Copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (e.g., poly (vinyl formal) and poly (vinyl formal))
(Vinyl butyral)), poly (ester) s, poly (urethanes), phenoxy resin, poly (vinylidene chloride), poly (vinylidene chloride)
(Epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, and poly (amides). The binder may be coated from water or an organic solvent or emulsion.

In the present invention, the back layer preferably has a maximum absorption of 0.3 or more and 2 or less in a desired wavelength range.
The absorption is more preferably 0.5 or more and 2 or less, and the absorption in the visible region after the treatment is preferably 0.001 or more and less than 5, and more preferably 0.001 or less.
It is preferable that the layer has an optical density of not less than 0.3 and less than 0.3. Examples of the antihalation dye used in the back layer are the same as those of the antihalation layer described above.

US Pat. Nos. 4,460,681 and 4,374,9
Backside resistive heating layer as shown in No. 21
stive heating layer) can also be used in a photosensitive heat developed photographic image system.

A hardener may be used for each layer such as the photosensitive layer, the protective layer and the back layer of the present invention. Examples of hardeners include H.
“THE THEORY OF THE PHOTOGRAPHIC PROCESS FO by James
URTHEDITION ”(published by Macmillan Publishing Co., Inc., 19
There are various methods described on pages 77 to 87, polyvalent metal ions described on page 78 of the same book, U.S. Pat.No. 4,281,060, polyisocyanates such as JP-A-6-208193, U.S. Pat.
Epoxy compounds such as 4,791,042, JP-A-62-89048
And vinylsulfone-based compounds such as

The hardener is added as a solution, and the solution is added to the coating solution for the protective layer from 180 minutes to immediately before coating, preferably from 60 minutes to 10 seconds before coating. The mixing conditions are not particularly limited as long as the effects of the present invention are sufficiently exhibited. As a specific mixing method, a method of mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid sent to the coater is set to a desired time, by N. Harnby, F. Edwards, AWNienow, Takahashi There is a method using a static mixer or the like described in Chapter 8 of Koji Translated "Liquid Mixing Technology" (Nikkan Kogyo Shimbun, 1989).

In the present invention, a surfactant may be used for the purpose of improving coating properties and charging. As the surfactant, any surfactant such as nonionic, anionic, cationic, and fluorine can be used as appropriate. Specifically,
No. 62-170950, Fluoropolymer surfactants described in U.S. Pat.No. 5,380,644, JP-A-60-244945, JP-A-63-18
8135 No. fluorinated surfactants described in U.S. Pat.
No. 5,965, and the like, and polysiloxy acid-based surfactants described in JP-A-6-301140 and the like, and polyalkylene oxide and anionic surfactants.

Examples of the solvent used in the present invention include New Solvent Pocket Book (Ohm Co., 1994), but the present invention is not limited thereto. The solvent used in the present invention has a boiling point of 40 ° C or more and 180 ° C or more.
C. or lower is preferred. Examples of the solvent of the present invention include hexane, cyclohexane, toluene, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, ethyl acetate, 1,1,1-trichloroethane, tetrahydrofuran, triethylamine, thiophene, trifluoroethanol, perfluoropentane, xylene , N-
Butanol, phenol, methyl isobutyl ketone, cyclohexanone, butyl acetate, diethyl carbonate, chlorobenzene, dibutyl ether, anisole, ethylene glycol diethyl ether, N, N-dimethylformamide,
Examples include morpholine, propane sultone, perfluorotributylamine, water and the like.

The emulsion for a photothermographic material according to the present invention comprises:
It can be coated on various supports. Typical supports are polyester films, primed polyester films, poly (ethylene terephthalate) filled polyethylene naphthalate films, cellulose nitrate films, cellulose ester films, poly (vinyl acetal) films, polycarbonate films and related or resinous materials , As well as glass, paper, metal and the like. Flexible substrates, especially partially acetylated or baryta and / or α-olefin polymers, especially polymers of α-olefins having 2 to 10 carbon atoms, such as polyethylene, polypropylene, ethylene-butene copolymers. A coated paper support is typically used. The support may be transparent or opaque, but is preferably transparent.

The light-sensitive material of the present invention comprises an antistatic or conductive layer such as a soluble salt (for example, chloride or nitrate), a vapor-deposited metal layer, US Pat. Nos. 2,861,056 and
It may have a layer containing an ionic polymer as described in US Pat. No. 3,206,312 or an insoluble inorganic salt as described in US Pat. No. 3,428,451.

As a method for obtaining a color image using the heat-developable photosensitive material of the present invention, there is a method described in JP-A-7-13295, page 10, left column, line 43 to 11 left column, line 40. Further, as a color dye image stabilizer, British Patent No. 1,326,889, U.S. Patent No. 3,432,300, No. 3,698,909, No. 3,574,62
No. 7, No. 3,573,050, No. 3,764,337 and No. 4,0
No. 42,394.

The photothermographic material of the present invention may be applied by any method. Specifically, extrusion coating, slide coating, curtain coating, dip coating, knife coating,
Various coating operations are used, including flow coating or extrusion coating using a hopper of the type described in U.S. Pat. No. 2,681,294, and are described by Stephen F. Kistl.
er, "LIQUID FILM COATING" by Peter M. Schweizer (C
Extrusion coating or slide coating described on pages 399 to 536, published by HAPMAN & HALL (1997) is preferably used, and particularly preferably slide coating is used. An example of the shape of the slide coater used for slide coating is shown in Figure 11 on page 427 of the same book.
in b.1. Also, if desired, the method described on page 399 to 536 of the same book, U.S. Pat.No. 2,761,791 and British Patent 837,0
Two or more layers can be coated simultaneously by the method described in No. 95.

Additional layers in the photothermographic material of the present invention, such as a dye-receiving layer for receiving a moving dye image, an opaque layer if reflective printing is desired, a protective topcoat layer and photothermographic techniques It may include a known primer layer and the like. The light-sensitive material of the present invention is preferably capable of forming an image with only one light-sensitive material, and it is preferable that a functional layer required for image formation such as an image receiving layer does not become another light-sensitive material.

Additional layers in the photothermographic material of the present invention, such as a dye-receiving layer for receiving a moving dye image, an opaque layer if reflective printing is desired, a protective topcoat layer and photothermographic techniques It may include a known primer layer and the like. The light-sensitive material of the present invention is preferably capable of forming an image with only one light-sensitive material, and it is preferable that a functional layer required for image formation such as an image receiving layer does not become another light-sensitive material.

The light-sensitive material of the present invention may be developed by any method, but is usually developed by elevating the temperature of the light-sensitive material exposed imagewise. The preferred development temperature is 80 to
The temperature is 250 ° C, more preferably 100 to 140 ° C. The development time is preferably from 1 to 180 seconds, more preferably from 10 to 90 seconds.

The light-sensitive material of the present invention may be exposed by any method, but a laser beam is preferred as an exposure light source.
As the laser beam according to the present invention, gas laser, YAG
Lasers, dye lasers, semiconductor lasers and the like are preferred. Further, a semiconductor laser and a second harmonic generation element can be used.

The light-sensitive material of the present invention has a low haze at the time of exposure and tends to cause interference fringes. As this interference fringe generation prevention technology, a technology disclosed in Japanese Patent Application Laid-Open No. 5-113548 or the like, in which a laser beam is obliquely incident on a photosensitive material, or a multi-mode laser disclosed in WO95 / 31754 or the like is used. There are known methods for performing these methods, and it is preferable to use these techniques.

For exposing the photosensitive material of the present invention, SPIE vo
l.169 Laser Printing 116-128 (1979), JP-A-4-5104
3. As disclosed in WO95 / 31754 and the like, it is preferable to expose the laser beams so that they overlap each other so that the scanning lines are not visible.

[0162]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 << Preparation of PET Support >> Terephthalic acid and ethylene glycol
PE having an intrinsic viscosity IV = 0.66 (measured in phenol / tetrachloroethane = 6/4 (weight ratio) at 25 ° C.) according to a conventional method using
Got T. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to prepare an unstretched film having a thickness of 175 μm after heat setting. .

This is performed by using rolls having different peripheral speeds.
The film was stretched twice in the longitudinal direction and then stretched in the transverse direction by a tenter 4.5 times. The temperatures at this time were 110 ° C. and 130 ° C., respectively. After that, it was heat-set at 240 ° C. for 20 seconds and relaxed 4% in the horizontal direction at the same temperature. Then, after slitting the chuck part of the tenter, knurling is performed on both ends and 4 kg
The roll was wound at a rate of 175 μm / cm ² .

<< Surface Corona Treatment >> Using a solid state corona treatment machine 6KVA model manufactured by Pillar Co., both surfaces of the support were treated at room temperature at 20 m / min. From the current and voltage readings at this time, 0.375 kV · A · min /
processing m ² was found to have been made. At this time, the processing frequency was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

<< Preparation of Undercoating Support >> (Preparation of Undercoating Coating Solution A) Aqueous dispersion of polyester copolymer Pesresin A-515GB (30%, manufactured by Takamatsu Oil & Fat Co., Ltd.) 200 m
To 1 l, 1 g of polystyrene fine particles (average particle size: 0.2 μm) and 20 ml of surfactant A (1 wt% aqueous solution) were added, and distilled water was added thereto to make 1000 ml, thereby obtaining an undercoating coating solution A.

(Preparation of Undercoating Coating Solution B) An aqueous dispersion of styrene-butadiene copolymer (styrene / butadiene / itaconic acid = 47/50/3 (weight ratio), concentration: 30) was added to 680 ml of distilled water.
wt%,) 200 ml, polystyrene fine particles (average particle size 2.5
μm), add distilled water, and add distilled water
Was used as an undercoating coating solution B.

(Preparation of Undercoating Coating Solution C) Inert gelatin (10 g) was dissolved in distilled water (500 ml).
40 g of an aqueous dispersion (40 wt%) of tin oxide-antimony oxide composite fine particles described in the specification of JP-A No. 33 was added, and distilled water was added to make 1000 ml, thereby obtaining an undercoating coating solution C.

(Preparation of Undercoating Support) After the above-mentioned corona discharge treatment, the undercoating coating solution A was applied by a bar coater so that the wet coating amount was 5 ml / m ² , and dried at 180 ° C. for 5 minutes. The dry film thickness was about 0.3 μm. Next, after applying a corona discharge treatment to the back surface (back surface), the undercoating coating solution B was applied using a bar coater so that the wet coating amount was 5 ml / m ² and the dry film thickness was about 0.3 μm. At 5
After drying for 1 minute, the undercoating solution C was further coated thereon with a bar coater at a wet application amount of 3 ml / m ² and a dry film thickness of about 0.03.
It was coated to a thickness of μm and dried at 180 ° C. for 5 minutes to prepare an undercoat support.

<< Preparation of Organic Acid Silver Dispersion >> 43.8 g of behenic acid (product name: Edenor C22-85R) manufactured by Henkel, distilled water 7
While stirring 30 ml of tert-butanol at 79 ° C. and 117 ml of 1N-NaOH aqueous solution over 55 minutes,
Minutes. Then, an aqueous solution of 19.2 g of silver nitrate 11
2.5 ml was added over 45 seconds, allowed to stand for 20 minutes, and cooled to 30 ° C. Thereafter, the solid content was separated by suction filtration, and the solid content was washed with water until the conductivity of the filtrate became 30 μS / cm. The solid content thus obtained was handled as a wet cake without drying, and 7.4 g of polyvinyl alcohol (trade name: PVA-205) and water were added to a wet cake equivalent to 100 g of dry solid content, so that the total amount was 38.
After 5 g, the mixture was preliminarily dispersed with a homomixer.

Next, the pre-dispersed stock solution is dispersed in a dispersing machine (trade name: Microfluidizer M-110S-EH, manufactured by Microfluidics International Corporation, using G10Z interaction chamber).
The pressure was adjusted to 1750 kg / cm ² and the mixture was treated three times to obtain a silver behenate dispersion B. The silver behenate particles contained in the silver behenate dispersion thus obtained were needle-shaped particles having an average minor axis of 0.04 μm, an average major axis of 0.8 μm, and a variation coefficient of 30%. Particle size measurement was performed by Malvern Instruments Ltd.
It was performed with SizerX. In the cooling operation, a coiled heat exchanger was mounted before and after the interaction chamber, and the temperature of the refrigerant was adjusted to a desired dispersion temperature.

<< Preparation of 25% Dispersion of Reducing Agent >> 1,1-bis
80 g of (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane and modified Poval MP203 2 manufactured by Kuraray Co., Ltd.
176 g of water was added to 64 g of a 0% aqueous solution and mixed well to form a slurry. Zirconia beads 80 having an average diameter of 0.5 mm
Prepare 0 g, put it in a vessel together with the slurry, and use a dispersing machine (1 / 4G sand grinder mill: IMEX Co., Ltd.)
For 5 hours to obtain a reducing agent dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained have an average particle size of 0.7.
It was 2 μm.

<< Preparation of 20% Dispersion of Mercapto Compound >> 64 g of 3-mercapto-4-phenyl-5-heptyl-1,2,4-triazole and modified Poval MP203-2 manufactured by Kuraray Co., Ltd.
224 g of water was added to 32 g of a 0% aqueous solution and mixed well to form a slurry. Zirconia beads 80 having an average diameter of 0.5 mm
Prepare 0 g, put it in a vessel together with the slurry, and use a dispersing machine (1 / 4G sand grinder mill: IMEX Co., Ltd.)
For 10 hours to obtain a mercapto dispersion. The mercapto compound particles contained in the thus obtained mercapto compound dispersion had an average particle size of 0.67 μm.

<< Preparation of 30% Dispersion of Organic Polyhalogen Compound >> 48 g of tribromomethylphenylsulfone and 3-g
Tribromomethylsulfonyl-4-phenyl-5-tridecyl
48 g of -1,2,4-triazole and modified Poval manufactured by Kuraray Co., Ltd.
224 g of water was added to 48 g of a 20% aqueous solution of MP203 and mixed well to form a slurry. 800 g of zirconia beads having an average diameter of 0.5 mm were prepared, put into a vessel together with the slurry, and dispersed with a disperser (1 / 4G sand grinder mill: manufactured by Imex Co., Ltd.) for 5 hours to obtain a polyhalogen compound dispersion. . The polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had an average particle size of 0.74 μm.
m.

<< Preparation of methanol solution of phthalazine compound >> 26 g of 6-isopropylphthalazine was added to methanol 10
It was dissolved in 0 ml and used.

<< Preparation of 20% Dispersion of Pigment >> CI Pigme
To 64 g of nt Blue 60 and 6.4 g of Demol N manufactured by Kao Corporation, 250 g of water was added and mixed well to form a slurry. 800 g of zirconia beads having an average diameter of 0.5 mm were prepared, placed in a vessel together with the slurry, and dispersed with a disperser (1 / 4G sand grinder mill: manufactured by Imex Co., Ltd.) for 25 hours to obtain a pigment dispersion. The pigment particles contained in the pigment dispersion thus obtained had an average particle size of 0.21 μm.

<< Preparation of Silver Halide Grain 1 >> Distilled Water 14
6.7 cc of a 1 wt% potassium bromide solution was added to 21 cc, and further
While stirring a liquid containing 8.2 cc of 1N nitric acid and 21.8 g of phthalated gelatin in a titanium-coated stainless steel reaction pot, the liquid temperature was maintained at 30 ° C., and distilled water was added to 37.04 g of silver nitrate to 159 cc. A solution b1 prepared by diluting a diluted solution a1 and potassium bromide 32.6 g with distilled water to a volume of 200 cc.
7. Prepare pAg by the control double jet method.
While maintaining the value of 1, the entire amount of the solution a1 was added at a constant flow rate over 1 minute. (The solution b1 was added by a controlled double jet method.) Thereafter, 30 cc of a 3.5% aqueous hydrogen peroxide solution was added, and 36 cc of a 3 wt% aqueous solution of benzimidazole was further added. Thereafter, the solution a1 was again diluted with distilled water to make 317.5 cc, and the solution b1 was dissolved with potassium trichloride iridate at a concentration of 1 × 10 ^-4 mol per mol of silver. Make the liquid volume 40 times twice that of solution b1.
Using solution b2 diluted with distilled water to 0 cc, the entire amount of solution a2 was added over 10 minutes at a constant flow rate by the controlled double jet method while maintaining the pAg at 8.25. (The solution b2 was added by a controlled double jet method.) Then, 50 cc of a 0.5% methanol solution of 2-mercapto-5-methylbenzimidazole was added, and the pAg was further reduced to 7.5 with silver nitrate, and then 1N sulfuric acid was added. PH using 3.
Adjust the pH to 8, stop stirring, perform sedimentation / desalting / washing steps, add 3.5 g of deionized gelatin, add 1N sodium hydroxide, and adjust to pH 6.0 and pAg 7.9 at 40 ° C. Thus, a silver halide dispersion was prepared.

The grains in the completed silver halide emulsion are pure silver bromide grains having an average equivalent sphere diameter of 0.022 μm and a coefficient of variation of the equivalent sphere diameter of 20%. The particle size and the like were determined from the average of 1000 particles using an electron microscope. The {100} plane ratio of these particles is 75% using the Kubelka-Munk method.
Was asked.

The temperature of the above agent was raised to 40 ° C. while stirring, and N,
5 ml of a 0.5 wt% methanol solution of N′-dihydroxy-N ″, N ″ -diethylmelamine and 5 cc of a 3.5 wt% methanol solution of phenoxyethanol were added, and after 1 minute, sodium benzenethiosulfonate was added to 1 mol of silver. 3 × 1
0 ^-5 mol was added. After 2 minutes, a solid dispersion of the spectral sensitizing dye 1 (aqueous gelatin solution) was added in an amount of 5 × 10 ⁻³ mol per mol of silver, and after 2 minutes, the tellurium compound was added in an amount of 5 × 10 ⁻⁵ per mol of silver.
Mol was added and the mixture was aged for 50 minutes. Immediately before ripening, 2-mercapto-5-methylbenzimidazole is added in an amount of 1 per mole of silver.
The temperature was lowered by adding × 10 ^-3 mol, and the chemical sensitization was completed to prepare silver halide grains 1.

The grain size was changed in exactly the same manner as for Emulsion 1, except that the liquid temperature during grain formation was changed.
Emulsions 2 to 5 in Table 1 were prepared in exactly the same manner except that the amounts of the chemical sensitizer and the sensitizing dye were adjusted to give optimum sensitivity in sensitometry described below.

[0181]

[Table 1]

<< Preparation of Emulsion Layer Coating Solution >> (Emulsion Layer Coating Solution No. 1) Organic Silver Dispersion 103 Obtained Above
g, 20 of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.)
5 g of a wt% aqueous solution was mixed and kept at 40 ° C.
23.2 g of reducing agent dispersion, 1.2 g of 20% aqueous dispersion of pigment CI Pigment Blue 60, organic polyhalogen compound 3
10.7 g of a 0% dispersion and 1.0 g of a 20% dispersion of a mercapto compound were added. Thereafter, 40 wt% of UF-purified SBR latex kept at 40 ° C. was added, and the mixture was sufficiently stirred. Then, 6 ml of a methanol solution of a phthalazine compound was added to obtain a liquid containing an organic silver salt. Further, silver halide grains 1 to 5 were well mixed in advance, and mixed with a liquid containing an organic acid silver by a static mixer immediately before coating to prepare a coating solution for an emulsion layer. At this time, the pAg of the coating solution was adjusted as shown in the table using an aqueous solution of silver nitrate and KBr. Then, the solution was fed such that the amount of silver applied was as follows.

Silver behenate coating amount (in terms of silver) 1.5 g / m ² Silver halide coating amount (in terms of silver) 0.15 g / m ² Emulsion layer thickness 18 μm

[0184]

[Table 2]

The viscosity of the emulsion layer coating solution was measured with a B-type viscometer (using a No. 1 rotor) manufactured by Tokyo Keiki Co., Ltd.
[mPa · s]. The viscosity of the coating solution at 25 ° C. using an RFS Fluid Spectrometer manufactured by Rheometrics Far East Co., Ltd. was determined at a shear rate of 0.1, 1, 10, 10
1500, 220, 70, 40, 20 at 0, 1000 [1 / sec]
[mPa · s].

The UF-purified SBR latex was obtained as follows. The following SBR latex diluted 10 times with distilled water was used for UF-purification module, FS03-FC-FUY03A1
(Daisen Membrane System Co., Ltd.) was used after dilution and purification until the ionic conductivity became 1.5 mS / cm. At this time, the latex concentration was 40%.

(SBR latex: -St (68) -Bu (29) -AA (3)-
Latex) average particle size 0.1μm, concentration 45%, ionic conductivity
4.2 mS / cm (Ion conductivity was measured using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd. at 25 ° C. with a latex stock solution (40%)), pH 8.2.

<< Preparation of Emulsion Surface Intermediate Layer Coating Solution >> (Intermediate Layer Coating Solution) Polyvinyl alcohol PVA-205 (Kuraray)
772 g of a 10% by weight aqueous solution of a methyl methacrylate / styrene / 2-ethylhexyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer weight ratio 59/9/26/5/1) 27.5% latex To 226 g of the liquid, 2 ml of a 5 wt% aqueous solution of aerosol OT (manufactured by American Cyanamid), 4 g of benzyl alcohol, 2,
1 g of 2,4-trimethyl-1,3-pentanediol monoisobutyrate and 10 mg of benzoisothiazolinone were added to prepare an intermediate layer coating solution, which was fed to a coating die at 5 ml / m ² . The viscosity of the coating solution was 21 mPa · s at 40 ° C. using a B-type viscometer (using a No. 1 rotor).

<< Preparation of Coating Solution for Emulsion Surface Protective Layer First Layer >> (Protective Layer First Layer Coating Solution No. 1) Inert gelatin (80 g) was dissolved in water, and a 10% methanol solution of phthalic acid was added to 138 ml.
l, 28 ml of 1N sulfuric acid, 5 ml of a 5 wt% aqueous solution of Aerosol OT (manufactured by American Cyanamid Co.), 1 g of phenoxyethanol, and water to make a total amount of 1000 g, make a coating solution to 10 ml / m ² . The solution was sent to a coating die. The viscosity of the coating solution was 17 mPa · s at 40 ° C. using a B-type viscometer (using a No. 1 rotor).

<< Preparation of Emulsion Surface Protective Layer Second Layer Coating Solution >> (Protective Layer Second Layer Coating Solution) Inert gelatin (100 g) was dissolved in water, and N-perfluorooctylsulfonyl-N-propylalanine potassium salt 5% 20 ml of the solution and 1% of a 5 wt% solution of Aerosol OT (American Cyanamid)
6 ml, polymethyl methacrylate fine particles (average particle size: 4.
(0 μm) 25 g, 44 ml of 1N sulfuric acid, 10 mg of benzoisothiazolinone, water were added to make a total amount of 1555 g, and 445 ml of an aqueous solution containing 4 wt% of chromium alum and 0.67 wt% of phthalic acid was added immediately before coating. The mixture mixed with a tick mixer was used as the coating solution for the surface protective layer, and 10 ml / m
^The solution was fed to the coating die so as to be ² . The viscosity of the coating solution was 9 mPa at 40 ° C using a B-type viscometer (using a No. 1 rotor).
[S].

<< Preparation of Back Surface Coating Liquid >> (Preparation of Solid Precursor Dispersion of Base Precursor) 64 g of the base precursor compound and 10 g of Demol N surfactant manufactured by Kao Corporation were mixed with 246 ml of distilled water. The beads were dispersed using a sand mill (1/4 Gallon Sand Grinder Mill, manufactured by AIMEX Co., Ltd.) to obtain a solid precursor dispersion liquid of a base precursor having an average particle diameter of 0.2 μm.

(Preparation of Dye Solid Fine Particle Dispersion) 9.6 g of a cyanine dye compound and 5.8 g of sodium p-alkylbenzenesulfonate were mixed with 305 ml of distilled water, and the mixed solution was subjected to a sand mill (1/4 Gallon sand grinder mill, Amimex). The dispersion of beads was carried out using the above method to obtain a dispersion of solid dye fine particles having an average particle diameter of 0.2 μm.

(Preparation of antihalation layer coating solution) Gelatin (17 g), polyacrylamide (9.6 g), solid fine particle dispersion of base precursor (70 g), solid fine particle dispersion of dye (56 g), polymethyl methacrylate fine particles (average particle size 6.5 μm) ) 1.5 g, 2.2 g of sodium polyethylene sulfonate, 0.2 g of a 1% aqueous solution of a coloring dye compound and 844 ml of H ₂ O were mixed to prepare a coating solution for an antihalation layer.

(Preparation of Coating Solution for Protective Layer) The container was kept warm at 40 ° C., and 50 g of gelatin, 0.2 g of sodium polystyrene sulfonate, 2.4 g of N, N′-ethylenebis (vinylsulfoneacetamide), t-octylphenoxyethoxy were used. ethanesulfonic acid sodium 1g, benzisothiazolinone 30mg, a _{C 8 F 17 SO 3 K 32mg} , C 8 F 17 SO 2 N (C 3 H 7)
(CH ₂ CH ₂ O) ₄ (CH ₂ ) ₄ -SO ₃ Na (64 mg) and H ₂ O (950 ml) were mixed to prepare a protective layer coating solution.

[0195]

Embedded image

<< Preparation of Photothermographic Material >> The undercoated support was coated with the antihalation layer coating solution at a coating weight of 0.04 g / m ² of the solid fine particle dye, and the protective layer coating solution was gelatinized. Coating is applied simultaneously to give a coating weight of 1 g / m ^2, and dried to form an antihalation back layer. Then, the emulsion layer, intermediate layer, protective layer first layer and protective layer are formed on the opposite side of the back surface from the undercoat surface. Layers were coated simultaneously in the order of the second layer by a slide bead coating method to prepare a photothermographic material sample.
The emulsion surface was applied without winding after coating the back surface.

The coating was performed at a speed of 160 m / min, the distance between the tip of the coating die and the support was set to 0.18 mm, and the pressure in the decompression chamber was set 392 Pa lower than the atmospheric pressure. In the subsequent chilling zone, air with a dry-bulb temperature of 18 ° C and a wet-bulb temperature of 12 ° C is blown at an average wind speed of 7 m / sec for 30 seconds to cool the coating liquid, and then a sloating floating type drying zone. A dry air having a dry-bulb temperature of 30 ° C. and a wet-bulb temperature of 18 ° C. was blown out from the holes at an air velocity of 20 m / sec for 200 seconds to volatilize the solvent in the coating solution. Table 3 shows the results of the above evaluation performed for each light-sensitive material.

(Evaluation of photographic performance) After exposing the photographic material with a 647 nm Kr laser sensitometer (maximum output: 500 mW) at an inclination of 8 degrees with respect to the normal, the photographic material was processed at 120 ° C. for 15 seconds.
(Development), and the density of the obtained image was evaluated using a densitometer.

[0199]

[Table 3]

Example 2 Comparative silver halide emulsion 6 was prepared in exactly the same manner as in emulsions 2 and 4 prepared in Example 1 except that the amount of iridium tripotassium hexachloride added during grain formation was changed. ~
11 was created.

When the doping ratio of iridium was examined, it was clarified from the experiment of the atomic absorption method that the emulsions 2, 4 and 6 to 11 were almost 100%.

[0202]

[Table 4]

Using the above emulsion, 40% of the coating solution for the emulsion layer was prepared.
Coating samples in Table 5 were prepared in exactly the same manner as the coating sample preparation method in Example 1 except that the pAg at 5.0 ° C. was changed to 5.0.

[0204]

[Table 5]

When the sensitivity, fogging and storage fog resistance of this light-sensitive material were evaluated in the same manner as in Example 1, the results shown in Table 6 were obtained.

[0206]

[Table 6]

Table 6 shows that in the present invention, doping with 1 × 10 ⁻⁵ mol / Ag mol or more of iridium leads to higher sensitivity.

Example-3 In coating samples 4 and 9 prepared in Example 1, the ion conductivity was changed as shown in Table 7 by changing the pAg of the emulsion layer coating solution and the amount of the added mercapto compound. The ionic conductivity of the silver halide in the thickly coated (about 200 μm) emulsion layer film was confirmed by a dielectric loss method. By changing this ionic conductivity, the pA of the emulsion layer coating solution at the time of the final coating product preparation
Except for changing g, coating samples 21 to 25 were prepared in exactly the same conditions as the coating sample preparation conditions of Example 1.

[0209]

[Table 7]

The coating samples in Table 7 were evaluated according to the evaluation method of Example 1 except that the silver tone was evaluated by visual sensory evaluation. ○ Slightly bluish silver tone is preferable. Δ: Somewhat unfavorable in reddish silver tone. × Unfavorable reddish color tone.

[0211]

[Table 8]

Example-4 A silver halide emulsion and a coated sample were prepared in exactly the same manner as in Example 1, except that no sensitizing dye was added. It was confirmed that the effect of the present invention was hardly exhibited in a system without a sensitizing dye.

Example-5 In the present invention, when the method of forming fine grains of the main kind described in JP-A-10-111541 was applied to the formation of silver halide grains, good results were obtained.

Claims (7)

[Claims] 1. A photothermographic material wherein at least one photosensitive layer containing at least a non-photosensitive organic silver salt, a reducing agent and photosensitive silver halide grains is coated on a support. Is a photothermographic material satisfying all of the following requirements: PA of a coating solution used for coating the photosensitive layer
g is not less than 2.5 and not more than 6.5 at 40 ° C. The sphere equivalent diameter of the photosensitive silver halide grains is 10 nm or more and 50 nm or less. The photosensitive silver halide grains are spectrally sensitized by a spectral sensitizing dye. 2. The photothermographic material according to claim 1, wherein the photothermographic material does not contain a substance adsorbed on the surface of the silver halide in an amount exceeding an amount that reduces the ionic conductivity of the photosensitive silver halide emulsion to 1/10 or less. 3. The method according to claim 1, wherein the photosensitive silver halide emulsion is 1 × 10
3. The photothermographic material according to claim 1, comprising a polyvalent metal compound in an amount of ^-5 mol / Ag mol or more. 4. The heat according to claim 1, wherein the amount of the spectral sensitizing dye added is 1 × 10 ^-3 mol or more and 1 × 10 ^-1 mol per mol of silver halide. Developed photosensitive material. 5. The method according to claim 1, wherein a main binder of the photosensitive layer is a water-soluble polymer and / or a water-dispersible polymer, and 30% by weight or more of a solvent of the coating solution is water. The photothermographic material according to the above. 6. The photothermographic material according to claim 1, wherein the spectral sensitizing dye has an absorption maximum at 600 nm or more. 7. Thermal development in which a coating solution containing at least a non-photosensitive organic silver salt, a reducing agent and photosensitive silver halide particles is coated on a support and dried to provide at least one photosensitive layer. A method for producing a photothermographic material, wherein the coating solution satisfies all of the following requirements (1) to (4). The coating solution has a pAg of 2.5 or more and 6.5 or less at 40 ° C. The sphere equivalent diameter of the photosensitive silver halide grains is 10 nm or more and 50 nm or less. The photosensitive silver halide grains are spectrally sensitized by a spectral sensitizing dye.