JP2002207270A - Photo-thermal photographic image forming material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-thermal photographic image forming material with suppressed fog and superior sensitivity, to provide a photo-thermal photographic image forming material with superior raw storage property or image storage property, and to provide a photo-thermal photographic image forming material with excellent tone. SOLUTION: In the photo-thermal photographic image forming material having a photosensitive layer containing photosensitive silver halide particles, organic silver salts, a reducing agent and a binder on a supporting body, the organic silver salts are formed in the presence of at least one kind selected from enhancing color sensitizers, chemical sensitizers, fog suppressing agents, improving agents for light resistance, high contrast agents and toning agents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photothermographic image-forming material which forms an image by thermal development after exposure, and more particularly to a photothermographic image which suppresses fog, has excellent sensitivity, and has excellent raw storability and image storability. For forming material.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand in the medical field for photographic materials which form an image by light or heat treatment which does not generate waste liquid due to wet processing from the viewpoint of environmental protection and workability. Techniques relating to photothermographic image forming materials for photographic technology, which can form a high-resolution and clear black image by development using the same, have been commercialized and rapidly spread.
Since these photothermographic image forming materials are usually developed at a temperature of 80 ° C. or higher, they are called photothermographic image forming materials to be distinguished from conventional wet photosensitive materials which are liquid-developed in the range of 25 ° C. to 45 ° C.

Conventionally, a photothermographic image forming material of this type contains a reducing agent and an organic silver salt as essential components in addition to photosensitive silver halide, so that fog tends to increase during storage and the technology is used to suppress this. Was needed. The term "preservation" refers to the period of time from when the photothermographic image forming material is applied and dried at the factory, cut and packaged to the size for each application, shipped from the factory, and thermally developed by customers. It means performance, and it is desired that the performance does not fluctuate even when stored for a long period of time. As a simple test method of this performance, there is a heat resistance test method which is shown as a raw preservability of an evaluation method in Examples described later. The image storability is the storability after exposure and development by the customer, and there is a simple heat resistance test method similar to the raw storability.

[0004] As a method for suppressing fog during storage, a mercapto compound is generally used. However, 1-phenyl-5-mercaptotetrazole, 5-methylbenzotriazole or 5-methylbenzotriazole used in conventional silver halide grains is used. Sufficient effects were not obtained with 5-methylbenzimidazole and the like. In addition, when a strong inhibitor is used, there are problems such as deterioration of sensitivity, deterioration of contrast, and deterioration of silver tone.

Further, this type of photothermographic image forming material has a weak point that it is weak in light fastness because fogging increases when exposed to light due to the presence of unexposed silver halide grains and a reducing agent even after development. was there. As a technique for overcoming this, polyhalomethane compounds are effective, and various polyhalomethane compounds have been developed, but not sufficiently.

Further, there is a technique using hydrazine to efficiently use silver. However, hydrazine is disadvantageous in that fog is increased and storability (raw and image storability) is easily deteriorated. Many searches for the structure of hydrazine have been made, but none have been found satisfactory.

[0007] The pursuit of excellent sensitivity and suppressed fogging not only deteriorates the storage stability, but also deteriorates the color tone of silver. In medical materials and printing materials that secure image density with silver particles, the black tone of the silver image is regarded as important, and in order to obtain a black image, an additive called a toning agent is used as an essential additive. . Among them, phthalazine compounds are used as usual additives because they give good color tone and improve developability, but they sacrifice image preservation, so the search for compounds around them has been advanced, but sufficient compounds have been found Not.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a photothermographic image forming material which suppresses fog and has excellent sensitivity. A second object is to provide a photothermographic image-forming material having excellent raw storability or image storability. A third object is to provide a photothermographic image forming material having excellent color tone.

[0009]

[Means for Solving the Problems] In a photothermographic image-forming material having a photosensitive layer containing a photosensitive silver halide particle, an organic silver salt, a reducing agent and a binder on a support, the formation of the organic silver salt can be supersensitized, a chemical sensitizer can be used. , Fog inhibitors,
A photothermographic image forming material, wherein the photothermographic image forming material is performed in the presence of at least one selected from a lightfastness improver, a high contrast agent and a toning agent.

[0010] 2. 2. The photothermographic image forming material according to 1, wherein the supersensitizer is a thyuronium salt compound and the chemical sensitizer is a thiourea compound, a phosphosulfide compound or a phosphoselenide compound.

3. 3. The photothermographic image-forming material according to 1 or 2, wherein the fog inhibitor is a disulfide compound.

4. The photothermographic image forming material according to any one of claims 1 to 3, wherein the light fastness improver is a polyhalomethane compound.

5. The photothermographic image forming material according to any one of claims 1 to 4, wherein the contrast agent is a hydrazine compound.

6. Any one of 1 to 5, wherein the toning agent is a phthalazine compound or a phthalic acid compound
Item.

Hereinafter, the present invention will be described in detail. The photothermographic image forming material for medical use of the present invention has at least two layers including a photosensitive layer and a protective layer on one side of a support, and a BC layer on the side opposite to the photosensitive layer side with respect to the support. (Back coat layer), and in some cases, a BC protective layer is provided on the BC layer. The photosensitive layer of the photothermographic image-forming material contains photosensitive silver halide grains which may be sensitized with a spectral sensitizing dye, and an organic source serving as a silver source is contained in the photosensitive layer or in a layer adjacent thereto. It contains a silver salt and a reducing agent for developing the silver salt to form a silver image.

(Organic Silver Salt) The organic silver salt contained in the photothermographic image forming material of the present invention is a reducible silver source, and an organic acid, a heteroorganic acid and an acid polymer containing a reducible silver ion source. Silver salts of the like are used. Also, the ligand is
Organic or inorganic silver salt complexes having a total stability constant for silver ions of 4.0 to 10.0 are also useful. Examples of silver salts are
Research Disclosure No. 17029
And 29963, and preferred organic silver salts include, for example, silver salts such as gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, lauric acid, arachidic acid, arachidonic acid, and erucic acid. Silver salts of stearic, arachidic and behenic acids are useful.
The organic silver salt is prepared by mixing one or more alkali metal salts of an organic acid and silver nitrate as an inorganic compound serving as a silver ion supply source at a predetermined temperature (usually 1 ° C to 100 ° C) to form an organic silver salt. However, nitrate ions and alkali metal ions such as sodium and potassium can usually be obtained by desalting to 2% or less. After desalting, it can be dehydrated and dried in terms of productivity. When an alkali metal salt of an organic acid and silver nitrate are mixed, there are a method in which silver halide grains are present and a method in which silver halide grains are not present, but the present invention does not limit the presence of silver halide grains. However, the following chemical sensitizers, fogging inhibitors, lightfastness improvers, high contrast agents and toning agents (hereinafter simply referred to as compounds of the present invention) which are present at the time of mixing, that is, at the time of organic silver salt formation, And these compounds of the present invention
A single type or a plurality of types may be used. Regarding the method of addition, it may be added in the presence of an alkali metal salt solution of an organic acid, may be added in the presence of a silver nitrate solution, or may be added as a separate solution. A preferred method of addition is to prepare and add as a separate solution. The timing of the addition may be simultaneous mixing, or the compound of the present invention may be added in advance, and then the alkali metal salt of an organic acid and silver nitrate may be added. Further, the compound of the present invention may be added during the period from the start of mixing of the alkali metal salt of an organic acid and silver nitrate to the end thereof. Hereinafter, the chemical sensitizer, the fog inhibitor, the light fastness improver, the high contrast agent, and the toning agent which are present at the time of forming the organic silver salt will be described.

(Supersensitizer and Chemical Sensitizer) The supersensitizer of the present invention which is present at the time of forming an organic silver salt means a compound which enhances the spectral sensitization of silver halide grains, and is particularly preferable. Examples thereof include a thiuronium salt compound containing a sulfur atom and a nitrogen atom and having a heterocyclic group (a group derived from imidazole, tetrazole, triazole, or the like).

The chemical sensitizer of the present invention to be present at the time of forming the organic silver salt is a compound containing an unstable sulfur atom which sensitizes the intrinsic sensitivity of silver halide grains, a compound containing a selenium atom, or the like. Particularly preferred compounds include thiourea derivatives each having a phenyl group, phosphosulfide compounds, and phosphoselenide compounds. Preferred specific examples of the supersensitizer and the chemical sensitizer are shown below, but the invention is not limited thereto.

[0019]

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[0020]

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The fogging inhibitor of the present invention which is present at the time of forming the organic silver salt may be a compound having a mercapto group, but a disulfide compound is particularly preferred. The disulfide compound is not particularly limited as long as the disulfide group is present in the molecule, and is preferably a compound in which an aliphatic group, an aromatic group, a heterocyclic group or the like is bonded to the disulfide group. Specific examples of preferred disulfide compounds are shown below, but the present invention is not limited thereto.

[0022]

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(Light fastness improver) As the light fastness improver of the present invention to be present at the time of forming the organic silver salt, a polyhalomethane compound which releases a halogen radical is preferable. Polyhalomethane compounds include polyhalomethyl groups (tribromomethyl group, dibromomethyl group, trichloromethyl group, etc.)
Is directly bonded to an aliphatic group (aliphatic group having 1 to 40 carbon atoms), an aromatic group (phenyl group, naphthyl group, etc.) or a heterocyclic group (pyridyl group, furyl group, imidazolyl group, tetrazolyl group, etc.) A polyhalomethane compound having the structure:
And a polyhalomethane compound having a structure linked via a linking group such as a sulfonyl group and a carbonyl group. Specific examples of particularly preferred polyhalomethane compounds are shown below, but the present invention is not limited thereto. .

[0024]

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The high-contrast agent of the present invention to be present during the formation of the organic silver salt is preferably a hydrazine compound having a -NHNH- group, and a particularly preferred hydrazine compound is -NHN.
H- group to a carbonyl group (-CO- group) or a sulfonyl group - compound (-SO ₂ group) is bonded is preferable. When adding the alkali metal salt of an organic acid and silver nitrate in the presence of a hydrazine compound, it is preferable to add them in the presence of the above-mentioned disulfide compound. Specific examples of preferred contrast agents are shown below, but the present invention is not limited thereto.

[0026]

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The toning agent of the present invention to be present at the time of forming the organic silver salt is preferably a phthalazine compound, particularly preferably a compound having a substituent at the 3- to 8-position of the phthalazine group. 1 to 36 optionally substituted alkyl or alkenyl groups, or aromatic groups such as phenyl group and naphthyl group, pyridyl group, furyl group,
A pyrimidyl group, an imidazolyl group, a thiophenyl group and the like are preferred. Specific examples of particularly preferred phthalazine compounds are shown below, but the present invention is not limited thereto.

[0028]

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The phthalazine compound is a phthalic oxide compound.
Is preferably used in combination with a phthalazine compound.
Orthophthalic acid is a preferred phthalic acid compound
And those having a substituent at the 3-position to 5-position are preferred.
No. As a substituent of phthalic acid, a halogen atom (fluorine
Atom, chlorine atom, etc.), alkyl group having 1 to 16 carbon atoms (meth
Tyl, ethyl, butyl, octyl, etc.), aromatic
Group (phenyl group, naphthyl group, etc.), heterocyclic group (pyridi
, An imidazole group, a furyl group, etc.). H
Preferred of phthalic acid compounds used in combination with thalazine compounds
Specific examples are shown below, but the present invention is not limited to these. (PT1) 4-methylorthophthalic acid (PT2) 4-fluoroorthophthalic acid (PT3) 6-fluoroorthophthalic acid (PT4) 4-isopropylphthalic acid (PT5) 4,5-dimethylphthalic acid (PT6) 4- Trifluoromethylphthalic acid The chemical sensitizer of the present invention added during the formation of the organic silver salt,
Antifoggants, lightfastness improvers, contrasting agents and toning agents
(Including tallic acid) in an amount of 10 ^-8~ 5 mo
Is preferably added in the range of More preferably 1
0^-7-10^-1Moles, particularly preferably in the range of 10^-6Mo
10^-3Is a mole. The above compound was dispersed in water
Dissolved in an organic solvent. As an organic solvent,
Alcohols such as methanol and ethanol; acetone,
Ketones such as methyl ethyl ketone; toluene, xylene
Can be selected arbitrarily.
You. The addition method is to mix the organic acid solution and the silver nitrate solution.
And mixing with an organic acid solution is preferable,
In the case of a small size, the average particle size is usually in the range of 1 nm to 10 μm.
The fine particles may be separately added to the surrounding fine particles.

(Reducing Agent) Examples of preferred reducing agents contained in the photothermographic image-forming material of the present invention are described in US Pat.
70,448, 3,773,512, 3,59
No. 3,863, Research Disclosur
e, Nos. 17029 and 29963, and particularly preferred specific examples include the following bisphenols. (K1) 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane (K2) bis (2-hydroxy-3-t-butyl-5)
-Methylphenyl) methane (K3) 2,2-bis (4-hydroxy-3-methylphenyl) propane (K4) 4,4-ethylidene-bis (2-t-butyl-6-methylphenol) (K5) 2 , 2-bis (3,5-dimethyl-4-hydroxyphenyl) propane The reducing agent is used by dispersing in water or dissolving in an organic solvent. As the organic solvent, alcohols such as methanol and ethanol; ketones such as acetone and methyl ethyl ketone; aromatic organic solvents such as toluene and xylene can be arbitrarily selected. The amount of reducing agent used is 1 silver
It is preferably 1 × 10 ⁻² to 10 mol per mol,
More preferably, it is 1 × 10 ^{-2 to} 1.5 mol.

(Photosensitive Silver Halide Particles) The photosensitive silver halide particles contained in the photosensitive layer of the photothermographic image forming material of the present invention are known in the field of photographic technology such as a single jet or double jet method. By any method,
For example, it can be prepared in advance by any method such as an ammonia method emulsion, a neutral method, and an acid method. The photosensitive silver halide grains are
In order to suppress white turbidity after image formation and obtain good image quality, particles having a small particle size are preferable. Usually 0.1 μm or less in average particle size, preferably 0.01 μm
To 0.1 μm, particularly preferably 0.02 to 0.08 μm. The shape of the photosensitive silver halide grains is not particularly limited, and may be cubic, octahedral, so-called normal crystals or non-normal crystals, such as spherical, rod-like, and tabular grains. The silver halide composition is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide.

The amount of the photosensitive silver halide grains is usually 50 to the total amount of the photosensitive silver halide grains and the organic silver salt described below.
% By mass, preferably from 25 to 0.1% by mass, more preferably from 15 to 0.1% by mass. Various conditions such as a reaction temperature, a reaction time, and a reaction pressure in the step of converting a part of the organic silver salt into silver halide using the above-mentioned silver halide forming component can be appropriately set according to the purpose of production. Usually, the reaction temperature is −23 ° C. to 74 ° C., the reaction time is 0.1 second to 72 hours, and the reaction pressure is preferably set to the atmospheric pressure.

The photosensitive silver halide grains prepared by the above-mentioned various methods can be chemically sensitized with, for example, a sulfur-containing compound, a gold compound, a platinum compound, a palladium compound, a silver compound, a tin compound, a chromium compound or a combination thereof. can do. The method and procedure of the chemical sensitization are described in, for example, U.S. Pat. No. 4,036,650, British Patent 1,518,850, and JP-A-51-2243.
No. 0, No. 51-78319, No. 51-81124 and the like.

The photosensitive silver halide grains of the present invention can be sensitized with a spectral sensitizing dye, if necessary. For example, JP-A-63-159814, JP-A-60-140335, JP-A-63-231437, and JP-A-63-231437. 63-259651, 6
3-304242, 63-15245, U.S. Pat. Nos. 4,639,414 and 4,740,455,
Nos. 4,741,966 and 4,751,175
No. 4,835,096 and the like. In particular, a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various laser light sources can be advantageously selected. For example, JP-A-9-34078, 9
Compounds described in JP-A-54409 and JP-A-9-80679 are preferably used.

(Binder) The polymer binder used as a binder in the photosensitive layer or the non-photosensitive layer of the photothermographic image-forming material of the present invention includes polyvinyl butyral, polyacrylamide, polystyrene, polyvinyl acetate, polyurethane, and poly (vinyl acetate). Acrylic ester, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, styrene-butadiene-
Acrylic copolymers and the like can be mentioned. After further drying, after forming a film, those having a low equilibrium water content of the coating film are preferred, and particularly those having a low water content include, for example, organic solvent-based cellulose acetate, cellulose acetate butyrate and polyacetal. it can. Polyacetal refers to a polymer obtained by producing polyvinyl alcohol by saponifying polyvinyl acetate and reacting the polyvinyl alcohol with an aldehyde compound.A preferred polyacetal of the present invention is a polyacetal that has been acetalized with butyraldehyde. Butyral,
Polyacetals acetalized with acetaldehyde (polyacetals in a narrow sense) are preferred. Acetalization is theoretically present up to 1% to 100%, but practically preferably 20% to 95%. Acetalization degree is 20
If it is less than 10%, the hydroxyl groups are increased, and the photographic performance may be weak against humidity. The acetalization degree is 95
%, The reaction temperature becomes severe, it takes time, and the cost productivity becomes disadvantageous.

(Crosslinking agent) The binder alone can maintain the adhesion to the lower layer and the upper layer and can provide a film strength that is hardly damaged by forming a film alone. Film adhesion and film strength can be increased. Also,
The cross-linking agent that cross-links between the binders also reacts with the organic or inorganic fine particles having a reactive group used in the present invention, and chemically bonds the organic or inorganic fine-particle binder to the binder with the cross-linking agent and fixes the binder. To Preferred crosslinking agents used in the present invention include crosslinking agents having an isocyanate group, a vinylsulfonyl group, an epoxy group and the like. Particularly preferred crosslinking agents include polyfunctional crosslinking agents having at least two isocyanate groups. Preferred crosslinking agents are shown below. (H1) hexamethylene diisocyanate (H2) trimer of hexamethylene diisocyanate (H3) tolylene diisocyanate (H4) phenylene isocyanate (H5) xylylene diisocyanate The crosslinking agent is water, alcohols , Ketones or non-polar organic solvents, or may be added as a solid in the coating solution. The addition amount is preferably equivalent to the group to be crosslinked, but may be increased to 10 times or less, or may be decreased to 1/10 or more. If it is less than 1/10, the crosslinking reaction may not easily proceed. If the ratio exceeds 10 times, the unreacted crosslinking agent may deteriorate photographic performance.

(Dye Used in AH Layer or BC Layer) The photothermographic image forming material of the present invention may be provided with an antihalation layer (hereinafter simply referred to as AH) of the photothermographic image forming material, if necessary.
Layer) or a back coat layer (hereinafter, also simply referred to as a BC layer). The dye used in the AH layer or the BC layer may be any dye that absorbs image exposure light. Preferred examples thereof include JP-A-2-216140 and JP-A-7-216140.
-13295, 7-11432, U.S. Pat.
380, 380, 635 and the like.

(Support) The support is preferably a support such as polyethylene terephthalate, polyethylene naphthalate or syndiotactic polystyrene.
A film having a thickness of 50 μm to 400 μm, which has high optical isotropy by axial stretching or heat fixing and good dimensional stability, is preferable.

<Image Exposure> The exposure method is described in
JP-A-304869, JP-A-9-311403 and JP-A-2
000-10230 can be used for laser exposure. For exposure of the photothermographic image forming material of the present invention, it is desirable to use a light source appropriate for the color sensitivity imparted to the photosensitive material. For example, if the light-sensitive material can be sensed by infrared light, any light source can be applied as long as it is in the infrared light range, but the laser power is high and the light-sensitive material can be made transparent. In view of the above, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

<Heat Developing Apparatus> An apparatus for developing the photothermographic image forming material of the present invention is described in JP-A-11-65067.
Nos. 11-72897 and 84619 can be used.

[0041]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1 <Preparation of Subbed Substrate> A polyethylene terephthalate support having a thickness of 175 μm was subjected to a corona discharge treatment of 12 W / m ² · min on both sides, and the following subbing coating solution a- 1
Is applied to a dry film thickness of 0.6 μm and dried to form an undercoat layer A-1.
-1 was applied to a dry film thickness of 0.6 μm and dried to form an undercoat layer B-1.

<< Undercoating Coating Solution a-1 >> Copolymer latex liquid of butyl acrylate (30% by mass) t-butyl acrylate (20% by mass) styrene (25% by mass) 2-hydroxyethyl acrylate (25% by mass) (30% solids) is diluted 15-fold.

<< Undercoat Coating Solution b-1 >> A copolymer latex liquid (solid content: 30%) of butyl acrylate (40% by weight) styrene (20% by weight) glycidyl acrylate (40% by weight) is diluted 15 times. .

Subsequently, the undercoat layer A-1 and the undercoat layer B-1
A 12 W / m ² · min corona discharge is applied to the upper surface of the undercoating layer A-1. On the undercoat layer B-1, and a lower undercoat layer B-2 (for BC layer) having an antistatic function by coating and drying the following undercoat upper layer coating solution b-2. .

<< Coating solution a-2 for lower undercoat >> 1: 2 copolymer of styrene and butadiene 0.4 g / m ² butyl acrylate (30 mass%) t-butyl acrylate (20 mass%) styrene (25 mass% 2.) 2-hydroxyethyl acrylate (20% by mass) methacrylic acid (5% by mass) copolymer latex liquid (solid content 30%) 0.3 g / m ² Matting agent fine particles (silica fine particles, average particle diameter 3 μm) 05 g / m ² Crosslinking agent: hexamethylene diisocyanate 0.1 g / m ² << Coating solution b-2 for undercoating layer >> 1: 2 copolymer of styrene and butadiene 0.4 g / m ² Conductive tin oxide fine particles ( average particle diameter 16 nm) 0.023 g / m ² butyl acrylate (30 wt%) t-butyl acrylate (20 wt%) styrene (25 wt%) of 2-hydroxyethyl A Relate (20 wt%) copolymer latex liquid methacrylic acid (5 weight%) (solid content 30%) 0.3 g / m ² Matting agent particles (silica particles, average particle size 3 [mu] m) 0.05 g / m ² cross Agent: hexamethylene diisocyanate 0.1 g / m ² AH layer having the following composition on the undercoated support prepared above,
A photosensitive layer and a photosensitive layer protective layer were simultaneously coated. First, a silver halide grain emulsion was prepared before coating, and then an organic silver salt was prepared using the prepared silver halide grain emulsion.

<Preparation of silver halide grain emulsion A> Water 90
7.5 g of inert gelatin and potassium bromide in 0 ml
Dissolve 10 mg and adjust the temperature to 28 ° C and the pH to 3.0
After that, 370 ml of an aqueous solution containing 74 g of silver nitrate and (98 /
Water solution containing potassium bromide and potassium iodide in molar ratio of 2)
While maintaining the solution at pAg 7.7,
It was added over 10 minutes by the wet method. Same as adding silver nitrate
1 x 1 sodium salt of hexachloroiridium
0 ^-6Mol / silver was added. Then 4-hydroxy-
6-methyl-1,3,3a, 7-tetrazaindene
Add 3 g, adjust the pH to 5 with NaOH, and adjust the average particle size.
Size 0.036 μm, coefficient of variation of projected diameter area 8%,
[100] Cubic silver iodobromide grains having an area ratio of 87% (photosensitive
An emulsion containing (silver halide grains) was obtained. Table 1
The compound (10)^-3Mole / silver mole, provided the compound is 2
5 × 10 when using each type^-FourMol / silver
Was added and stirred for another 20 minutes. Later, gelatin
After coagulation and sedimentation using a collecting agent and desalination treatment,
Finished to 0 ml. This is designated as silver halide grain emulsion A.
You.

<Preparation of Organic Silver Salt A> 111.4 g of behenic acid, 83.8 g of arachidic acid and 54.9 g of stearic acid were dissolved in 3980 ml of pure water at 80 ° C. Next, while stirring at a high speed, a 1.5 mol sodium hydroxide aqueous solution 54 was added.
After adding 0.2 ml of concentrated nitric acid and 6.9 ml of concentrated nitric acid,
It cooled to ° C and obtained the organic acid sodium solution. While maintaining the temperature of the above-mentioned organic acid sodium salt solution at 55 ° C., the silver halide grain emulsion A (containing 0.038 mol of silver) and 420 ml of pure water were added and stirred for 5 minutes. Next, 760.6 ml of a 1 mol silver nitrate solution and the compound (1
0 ^-3 mol / silver 1 mol, when using two kinds of compounds, 5 × 10 ^-4 mol / silver 1 mol each) over 2 minutes, and the mixture is further stirred for 20 minutes. Was removed. Thereafter, the conductivity of the filtrate is 2 μS / c.
m, washing with deionized water and filtration repeatedly,
Finally, it was dried after centrifugal dehydration. This is referred to as organic silver salt A.

<Coating of photosensitive layer and BC layer> The following layers on the photosensitive layer side and on the BC side were coated on the support provided with the undercoat layer. The drying was performed on both the photosensitive layer side and the BC side by 4 times.
Performed at 5 ° C. for 1 minute.

<Coating on BC Layer Side> On the back surface side, a coating solution prepared from the following composition was simultaneously coated and dried in the following amounts to form a BC layer.

<< Coating of BC Layer >> Binder: PVB-1 1.8 g / m ² Dye: C1

[0052]

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<< Coating of BC protective layer >> Binder: PVB-1 1.1 g / m ² Crosslinking agent: hexamethylene diisocyanate 1 × 10 ⁻⁴ mol / m ² <Coating on photosensitive layer side><< Coating of AH layer Coating> Binder: PVB-1 0.4 g / m ² Dye: C1 1.3 × 10 ⁻⁵ mol / m ² << Coating of photosensitive layer >> A coating solution of the following composition was prepared for forming a photosensitive layer, Coating and drying were performed so that the following amounts were obtained.
An amount of the organic silver salt A in which the amount of silver becomes 1.36 g / m ^2.
Was mixed with the polymer binder.

Organic silver salt A 1.36 g / m ^{2 in} terms of silver Binder: PVB-1 2.6 g / m ² Matting agent fine particles (silica fine particles, average particle diameter 2.5 μm) 0.01 g / m ² spectral increase sensitive dye A1 2 × 10 ^-5 mol / m ² antifoggant -1: pyridinium hydrobromide perbromide 0.3 mg / m ² antifoggant -2: isothiazolone 1.2 mg / m ² reducing agent: K1 3 × 10 ^{- 4} mol / m ²

[0055]

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<< Surface Protective Layer >> A coating solution prepared by adding the following composition was applied onto the photosensitive layer so as to have the following coating amount and dried to form a surface protective layer.

Binder: PVB-1 1.2 g / m ² phthalazinone 0.2 g / m ² 4-methylphthalic acid 0.7 g / m ² Tetrachlorophthalic acid 0.2 g / m ² Tetrachlorophthalic anhydride 0. 5 g / m ^{2 As} the binder, polyvinyl butyral (PVB-1) was selected, and methyl ethyl ketone (MEK) was used as the organic solvent.
It was used. PVB-1 was used after saponifying 98% of polyvinyl acetate having a polymerization degree of 500% and then butyralizing 86% of the remaining hydroxyl groups. PVB-1 was also used as a binder in the BC layer.

<< Evaluation Method >> (Immediate Photographic Performance) After leaving the photothermographic image forming material sample prepared above at 25 ° C. in an atmosphere of 48% relative humidity for 18 hours, a 810 nm photometer for semiconductor laser exposure was used. After exposure, and after heat development at 120 ° C. for 8 seconds, fog (density of unexposed portion) and sensitivity of the obtained sample were determined. The sensitivity is obtained as a reciprocal of the exposure amount that gives an optical density of 0.3, and is expressed as a relative sensitivity where the sensitivity of the reference sample 101 is 100. The infrared laser exposure was set to a double mode with an incident angle of 76 degrees.

(Raw storage stability) The photothermographic image forming material sample prepared as described above was exposed to an atmosphere at 25 ° C. and a relative humidity of 48%.
After leaving it for 4 hours, it was heat-sealed and sealed in a bag coated on both sides with polyethylene having a thickness of 20 μm, left at 55 ° C. for 55 hours, returned to room temperature, and immediately fogged in the same manner as in the evaluation of photographic performance. I asked.

(Image preservation property)
After leaving for 24 hours in an atmosphere of a relative humidity of 5 ° C. and 48%, heat sealed in a bag coated on both sides with polyethylene having a thickness of 20 μm, sealed and left for 55 hours at 55 ° C.
After returning to room temperature, fog was determined in the same manner as above.

Table 1 shows the above progress and results.

[0062]

[Table 1]

As can be seen from Table 1, the sample of the present invention in which an organic silver salt was prepared in the presence of the supersensitizer and / or the chemical sensitizer of the present invention exhibited high photographic performance with little fog and raw storage. It can be seen that the properties and the image preservability are also good.

Example 2 Samples were prepared and images were evaluated in the same manner as in Example 1, except that the disulfide compound (10 ^-4 mol / mol of silver), which is a fog inhibitor of the present invention, was used as shown in Table 2. ) Were prepared in the presence of an organic silver salt and a photosensitive silver halide grain, respectively. The progress and results are shown in Table 2.

[0065]

[Table 2]

From Table 2, it can be seen that the sample of the present invention in which an organic silver salt was prepared in the presence of a disulfide compound which is a fog inhibitor of the present invention had little fog, obtained high-sensitivity photographic performance, and had a long shelf life. Also, it can be seen that the image storability is good.

Example 3 Samples were prepared and images were evaluated in the same manner as in Examples 1 and 2, except that the polyhalomethane compound (10 ^-4 mol / l) as a light fastness improver of the present invention was used as shown in Table 3. (1 mol of silver) in the presence of an organic silver salt and photosensitive silver halide grains, respectively. The course and results are shown in Table 3.

[0068]

[Table 3]

From Table 3, it can be seen that the sample of the present invention in which an organic silver salt was prepared in the presence of a polyhalomethane compound as a lightfastness improver of the present invention had little fog, high photographic performance with high sensitivity, and was preserved raw. It can be seen that the properties and the image preservability are also good.

Example 4 Samples were prepared and images were evaluated in the same manner as in Examples 1, 2 and 3, except that the hydrazine compound (10 ^-4 mol (1 mol / silver) to prepare organic silver salts and photosensitive silver halide grains, respectively. The course and results are shown in Table 4.

[0071]

[Table 4]

From Table 4, it can be seen that the sample of the present invention in which an organic silver salt was prepared in the presence of a hydrazine compound as a high contrast agent of the present invention had little fog, obtained high-sensitivity photographic performance, and had good raw storability. Also, it can be seen that the image storability is good.

Example 5 Samples were prepared and images were evaluated in the same manner as in Examples 1, 2, 3 and 4, except that the phthalazine compound (tonal compound) of the present invention was used as shown in Tables 5 and 6. 10 ^-4 mol / silver 1 mol) and / or phthalic acid compound (10 ^-4 mol / silver 1 mol)
Mol) in the presence of an organic silver salt and light-sensitive silver halide grains. Here, the color tone was also evaluated.

The evaluation of the color tone was performed by visually evaluating the color tone of an image finished to have a density of 1.0 ± 0.1. The best level at which a black image was obtained was 5, the worst level at brown was 1, and the practically acceptable level was 3.

The progress is shown in Tables 5 and 6, and the results are shown in Table 6.

[0076]

[Table 5]

[0077]

[Table 6]

From Tables 5 and 6, it can be seen that the samples of the present invention in which the organic silver salt was prepared in the presence of the phthalazine compound as the toning agent of the present invention had good color tone, little fog, and high sensitivity. It can be seen that performance was obtained and raw storability and image storability were good. It can also be seen that when used in combination with phthalic acid, photographic performance and storage stability are more excellent.

[0079]

According to the present invention, it is possible to provide a photothermographic image-forming material in which fog is suppressed and sensitivity is excellent. Further, a photothermographic image forming material having excellent raw storability or image storability can be provided. Further, a photothermographic image forming material having an excellent color tone can be provided.

Claims (6)

[Claims] 1. A photothermographic image-forming material having a photosensitive layer containing photosensitive silver halide grains, an organic silver salt, a reducing agent and a binder on a support, a supersensitizer for forming an organic silver salt. A photothermographic image forming material, which is carried out in the presence of at least one selected from a chemical sensitizer, a fogging inhibitor, a light fastness improver, a high contrast agent and a toning agent. 2. The photothermographic image forming material according to claim 1, wherein the supersensitizer is a thiuronium salt compound, and the chemical sensitizer is a thiourea compound, a phosphosulfide compound or a phosphoselenide compound. . 3. The photothermographic image forming material according to claim 1, wherein the fog inhibitor is a disulfide compound. 4. The photothermographic image forming material according to claim 1, wherein the light fastness improver is a polyhalomethane compound. 5. The photothermographic image forming material according to claim 1, wherein the contrast agent is a hydrazine compound. 6. The photothermographic image forming material according to claim 1, wherein the toning agent is a phthalazine compound or a phthalic acid compound.