JP2000029162A - Heat developable photosensitive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material having excellent sensitivity, good coating property and no devitrification after thermal development. SOLUTION: This heat developable photosensitive material has a photosensitive layer 13 containing an org. silver salt, photosensitive silver halide particles and reducing agent on a supporting body 11. In this material, a layer containing inorg. fine particles or a fluorine-contg. polymer layer 12 is formed on the surface of the supporting body 11. Preferably, the layer containing the inorg. fine particles or the fluorine-contg. polymer layer 12 has voids and/or has <=1.50 refractive index of the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recording material for forming an image by dry processing, and more particularly to a photothermographic material which forms an image by heat development using an organic silver salt.

[0002]

2. Description of the Related Art Conventionally, in the field of printing plate making and medical treatment, preparation of a solution accompanying wet processing of an image forming material has been a problem in terms of workability, and in recent years, from the viewpoint of further environmental conservation and space saving. There is a strong demand for reducing the amount of processing waste liquid. Therefore, there is a need for a technique relating to photothermographic materials for photographic technology, which enables efficient exposure with a laser imagesetter or laser imager and can form a high-resolution, clear black image. As this technique, there is known a photothermographic material in which a support contains an organic silver salt, photosensitive silver halide particles and a reducing agent, as in US Pat. No. 3,152,904.

[0003] These photothermographic materials are usually 80 to
It is characterized in that an image is formed by heat development at 140 ° C. and no fixing is performed. Efficiently transmitting heat to the photosensitive material during thermal development is an effective means for increasing the sensitivity.

On the other hand, in the case of medical light-sensitive materials, lesions are usually observed through a light-sensitive material on a shakasten. When observing the photosensitive material on the Schaukasten, if the transparency of the photosensitive material is low and fogged, it is not preferable for diagnosis.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a photothermographic material which is excellent in sensitivity, has no problem in coating properties, and has improved devitrification after heat development.

[0006]

Means for Solving the Problems The object of the present invention has been intensively studied, and as a result, a recording layer containing at least photosensitive silver halide grains, an organic silver salt, and a reducing agent for the organic silver salt on a support. (Photosensitive layer) is provided, and a layer containing inorganic fine particles is provided between the support and the photosensitive layer, or on the support opposite to the side having the photosensitive layer, This was achieved by a photothermographic material having a fluorine atom-containing polymer layer between the support and the photosensitive layer or on the support opposite to the side having the photosensitive layer.

[0007] The sensitivity of the photothermographic material is increased by the layer having a large number of voids. Further, when the refractive index of the layer is 1.50 or less, the devitrification of the sample on the Schaukasten is reduced. Improved. In addition, there was no problem in applicability.

Hereinafter, the present invention will be described in detail.

The photothermographic material of the present invention comprises a support, a layer containing inorganic fine particles or a fluorine atom-containing polymer layer (hereinafter, also referred to as a "layer on the support surface") provided on the surface of the support. And a photosensitive layer formed on a layer on the surface of the body or support.

A typical example of the basic constitution of the photothermographic material of the present invention will be described with reference to FIGS. In FIG.
A photosensitive layer 13 is formed on one surface of a transparent support 11, a protective layer 14 is formed on the photosensitive layer, and a layer containing inorganic fine particles or a fluorine atom-containing polymer layer 12 is formed on the other surface. The cross section of the photothermographic material on which is formed is shown. In FIG. 2, a layer containing inorganic fine particles or a fluorine atom-containing polymer layer 22 is formed on one surface of a transparent support 21, and a photosensitive layer 23 is further formed thereon. The cross section of the photothermographic material on which the protective layer 24 is formed is shown above. On the other surface of the transparent support 21, a layer containing inorganic fine particles or a fluorine atom-containing polymer layer may be further provided.

The layer on the surface of the support in the present invention can be formed as follows.

Examples of the material of the transparent support include polyesters such as polyethylene terephthalate (PET); cellulose esters such as nitrocellulose, cellulose acetate, cellulose acetate butyrate; and polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide and the like. Among them, PET is preferable.

The thickness of the transparent support is not particularly limited, but is preferably 50 to 200 μm for handling. Further, as the support, those subjected to a corona discharge treatment, a flame treatment, and an ultraviolet irradiation treatment may be used.

The refractive index of the layer on the surface of the support of the present invention is 1.5.
0 or less, more preferably 1.50
~ 1.00. It may be a multilayer having a low refractive index and layers having different refractive indexes alternately laminated, and having a refractive index of 1.50 or less. The refractive index of the present invention refers to light having a wavelength of 633 nm. The layer consists of CaF ₂ , NaF, LiF, Mg
A layer in which F ₂ or SiO ₂ is formed by a vacuum evaporation method or a sputtering method may be used, but a layer (coating layer) formed by coating is preferable from the viewpoint of productivity.

The layer capable of being formed by coating includes a coating layer obtained by coating a coating solution obtained by dissolving a fluorine atom-containing polymer soluble in an organic solvent in an organic solvent, and silica fine particles (preferably having an average primary particle diameter of 10 nm). The transparent layer having a large number of voids obtained by applying a coating liquid in which inorganic fine particles such as those described below are dispersed in a water-soluble resin.

Examples of the fluorine atom-containing polymer which can be applied include homopolymers of a fluorine atom-containing acrylate monomer, a fluorine atom-containing methacrylate monomer and a fluorine atom-containing vinyl monomer, and copolymers of these monomers with an acrylate monomer, a methacrylate monomer or a vinyl monomer. A fluorine atom-containing acrylic resin such as a polymer; or a fluorine resin having a hydroxyl group such as a copolymer of fluoroolein and vinyl ether (usually used in combination with a polyisocyanate as a crosslinking agent) can be given. Preferably a fluorine atom-containing acrylic resin, specifically polytrifluoroethyl acrylate,
Examples thereof include polytrifluoropropyl acrylate, polytrifluorobutyl acrylate, and polytrifluoroethyl methacrylate.

The formation of the layer of the fluorine atom-containing polymer on the support surface is carried out, for example, as follows. It can be formed by preparing a coating solution in which the above-mentioned fluorine-containing polymer soluble in an organic solvent is dissolved in an organic solvent, and coating and drying the solution on the surface of a transparent support.

As the organic solvent, acetone, methyl ethyl ketone, methyl-i-propyl ketone, methyl-i-
Ketones such as butyl ketone and cyclohexanone; alcohols such as methanol, ethanol, i-propanol and butanol; chlorinated hydrocarbons such as methyl chloride, methylene chloride, carbon tetrachloride and trichloroethane; methyl cellosolve, ethyl cellosolve and methyl cellosolve acetate , Cellosolves such as ethyl cellosolve acetate;
Aromatic hydrocarbons such as toluene and xylene; methyl formate;
Esters such as ethyl formate, methyl acetate and ethyl acetate;
Glycols such as propylene glycol monobutyl ether can be mentioned. The solvent is appropriately selected from these solvents, and preferably contains at least methyl ethyl ketone.

Examples of the coating method include a bar coating method, a dip coating method, a hopper coating method and the like.

The layer containing the inorganic fine particles can be formed as follows. That is, it can be formed by applying and drying a coating liquid (aqueous dispersion) in which inorganic fine particles such as silica fine particles are dispersed in a water-soluble resin on the surface of a transparent support. Examples of the water-soluble resin include polyvinyl alcohol (PV) as a resin having a hydroxyl group as a hydrophilic structural unit.
A), cellulosic resin (methylcellulose (MC),
Ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC)
Etc.), chitins and starch; polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PE) as a resin having an ether bond.
G) and polyvinyl ether (PVE); and as resins having amide groups or amide bonds, polyacrylamide (PAAM) and polyvinylpyrrolidone (PVP)
Can be mentioned. A polyacrylate, a maleate, an alginate and a gelatin having a carboxyl group as a dissociative group; a polystyrene sulfonate having a sulfo group, an amino group, an imino group, a tertiary amine and a quaternary ammonium salt. Polyallylamine (PA
A), polyethyleneimine (PEI), epoxidized polyamide (EPAM), polyvinylpyridine and gelatins.

Examples of the inorganic fine particles include silica fine particles, colloidal silica, calcium silicate, zeolite,
Examples include kaolinite, halloysite, muscovite, talc, calcium carbonate, calcium sulfate, boehmite and the like.

The weight ratio of the inorganic fine particles to the water-soluble resin is 1.
5: 1 to 10: 1 are preferred.

Since the refractive index of the layer is 1.50 or less, the inorganic fine particles preferably have a refractive index of 1.40 to 1.60. That is, since the transparent layer having a large number of voids has fine voids of air having a refractive index of 1.0, even if fine particles having a refractive index of more than 1.50 are used, the refractive index of the layer is 1.50 or less. And can be done.

Among the inorganic fine particles, silica fine particles are preferable, and further, the average primary particle diameter is 10 nm or less (preferably 3 nm or less).
Silica fine particles having a refractive index of 1.50 or less.

Since the silica particles are liable to adhere to each other due to hydrogen bonding due to silanol groups on the surface, the average primary particle diameter is 10 μm or less (preferably 3 to 10 μm) as described above.
nm), a structure having a large porosity can be formed.

The silica particles are roughly classified into a wet method and a dry method according to the production method. The wet method is mainly a method in which active silica is generated by acid decomposition of a silicate, which is appropriately polymerized, aggregated and precipitated to obtain hydrous silica. On the other hand, dry process silica is a method by high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated, reduced and vaporized in an electric furnace by an arc, and oxidized by air. The method of obtaining anhydrous silica by (arc method) is the mainstream. These hydrated silica and anhydrous silica have different properties, such as the density of silanol groups on the surface and the presence or absence of vacancies, but exhibit different properties, but in the case of silicic anhydride (anhydrous silica), the three-dimensional structure has a particularly high porosity. Is preferred because it is easy to form. The reason for this is not clear, but the density of silanol groups on the surface is as high as 5 to 8 particles / nm ^{2 in} the case of hydrous silica, and the particles are likely to be densely aggregated (aggregate).軟 3 / nm ² , so coarse soft coagulation (flocculate)
And it is estimated that the structure has a high porosity.

From the viewpoint of lowering the refractive index, it is necessary to form a large number of fine voids. For this purpose, the type of resin to be combined with the silica fine particles is important. In the case of anhydrous silica, PVA, especially low saponification degree (Preferably a saponification degree of 70 to
90%) PVA is preferred in terms of light transmission. Although PVA has a hydroxyl group in the structural unit, it is considered that the hydroxyl group and a silanol group on the surface of the silica particle form a hydrogen bond, and thus it is easy to form a three-dimensional network structure in which the secondary particle of the silica particle is a chain unit. . It is presumed that a transparent layer having a structure with a high porosity is thereby obtained. Thereby, a support surface layer having a low refractive index is obtained.

In the transparent layer having a large number of voids, the ratio of the inorganic fine particles (preferably silica fine particles) to the water-soluble resin (PB ratio: the weight of the inorganic fine particles with respect to the weight of the water-soluble resin of 1) has a layer structure. Also has a big impact. As the PB ratio increases, the porosity, pore volume, and surface area (per unit weight) increase. If it exceeds 10, there is no effect on film strength and cracking at the time of drying, and if it is less than 1.5, the voids are closed by the resin, the porosity decreases, and the refractive index increases. Therefore, the preferred PB ratio is 1.5 to 10.

For example, when the average primary particle size as described above is 1
0 nm or less of anhydrous silica and a water-soluble resin having a PB ratio of 2 to 5
When completely dispersed in an aqueous solution and coated and dried, a three-dimensional network structure having two-dimensional silica particles as a chain unit is formed, the average pore size is 30 μm or less, the porosity is 50% or more, and the pore specific volume. 0.5 ml / g or more, specific surface area 100 m ² / g
The light-transmitting porous layer described above can be easily formed.

The transparent layer having a large number of voids is provided on a support, for example, as follows. That is, the coating liquid for forming a transparent layer is prepared by adding silica fine particles having an average primary particle diameter of 10 nm or less to water (for example, 10 to 15% by weight),
Using a high-speed rotating wet colloid mill (for example, CLEARMIX: manufactured by M-Tech Co., Ltd.), a high-speed rotation of, for example, 10,000 rpm (normally, 5,000 to 20,000 rpm) is performed.
After dispersing for minutes (usually 10 to 30 minutes), an aqueous PVA solution (for example, PVA having a weight of about 1/3 of silica) is added, and dispersion is performed under the same conditions. The coating solution thus obtained is a uniform sol, and a coating layer is formed on a support by the following coating method using the sol to obtain a surface layer having a three-dimensional network structure of the present invention. In forming the surface layer, the coating solution of the uniform sol is coated on a support, and then dried to evaporate water as a solvent. A wet gel is formed when the coating film reaches the gelation concentration due to the evaporation, and further drying proceeds to form a porous xerogel, thereby obtaining a transparent layer having a large number of voids.

The thickness of the layer on the surface of the support of the present invention thus obtained is generally suitably less than 0.01 to 10 μm, preferably less than 0.05 to 10 μm, and more preferably less than 0.010 μm.
5-5 μm is preferred.

The photothermographic material of the present invention basically comprises a photosensitive silver halide, a non-photosensitive silver source such as a silver salt of an organic acid, and a reducing agent for the silver source. A photographic image is formed using a heat development processing method. For details of the photothermographic material, see, for example, US Pat. No. 3,152,904,
No. 3,457,075 and D.C. Morgan
an) "Dry silver photographic material (Dry Si
Lever Photographic Material
l) "and D.E. Morgan & B.M. Shelly Processed Sil by Shelly
verSystems) ", Sturge
e), V.I. Walworth, A .;
"Imaging Processes and Materials (Imaging), edited by Shepp
Processes and Material
s) "8th edition, page 2, Neblette, 1969)
Etc.

The photosensitive silver halide grains in the present invention will be described.

In order to suppress white turbidity after image formation and obtain good image quality, the average particle size is preferably small, and the average particle size is preferably 0.2 μm or less, more preferably 0.01 to 0.17 μm. Especially 0.02 to 0.14 μm
Is preferred. The grain size referred to here means that when the silver halide grains are cubic or octahedral so-called normal crystals,
The length of the edge of a silver halide grain. In the case where the silver halide grains are tabular grains, the diameter refers to the diameter when converted into a circular image having the same area as the projected area of the main surface.

The silver halide is preferably monodispersed. Here, the monodispersion means that the degree of monodispersion determined by the following equation is 40 or less. More preferably 30 or less,
Particularly preferred are particles of 0.1 to 20.

Monodispersity = (standard deviation of particle size / average value of particle size) × 100 The shape of the silver halide grains may be cubic, octahedral, tabular, spherical, rod-like, potato-like, or the like. Although cubic grains and tabular grains are particularly preferred in the present invention.

When tabular silver halide grains are used, the average aspect ratio is preferably from 2 to 100, and more preferably from 3 to 50. These are disclosed in US Pat. No. 5,264,3.
No. 37, 5,314,798, 5,320,95
No. 8, etc., and desired tabular grains can be easily obtained. Further, grains having rounded corners of silver halide grains can also be preferably used.

The outer surface of the silver halide grains is not particularly limited, but preferably has a high ratio of the Miller index {100} plane, and this ratio is 50% or more, and more preferably 70%.
It is preferably at least 80%. The ratio of the Miller index {100} plane is {1} in the adsorption of the sensitizing dye.
T. using the adsorption dependence between the {11} plane and the {100} plane.
Tani; Imaging Sci. , 29,16
5 (1985).

The halogen composition of the silver halide is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide and silver iodide. In the present invention,
Silver bromide or silver iodobromide can be preferably used. Particularly preferred is silver iodobromide, and the silver iodide content is O.I. 1 to 40 mol% is preferable. 1-20 mol% is more preferable. The distribution of the halogen composition in the grains may be uniform, the halogen composition may be changed stepwise, or may be changed continuously, but as a preferred example, the silver iodide content in the grains is preferred. High silver iodobromide grains can be used. Preferably, silver halide grains having a core / shell structure can be used.

The photographic emulsion used in the present invention is described in P.I. Gl
chimie et Physique
e Photographique (Paul Mon
tel, 1967); F. Duffin; P
photographic Emulsion Chem
istry (published by The Focal Press, 19
66); L. Zelikman et al; Making
and Coating Photographic
Emulsion (The Focal Press
Ed., 1964) and the like.

That is, any of an acidic method, a neutral method, an ammonia method and the like may be used, and a method of reacting a soluble silver salt with a soluble halide may be any of a one-side mixing method, a double-mixing method, a combination thereof and the like. May be used.

The silver halide may be added to the image forming layer by any method, and the silver halide is arranged so as to be close to the reducible silver source. Further, the silver halide may be prepared by converting a part or all of the silver in the organic acid silver by the reaction of the organic acid silver and the halogen ion into silver halide, or may be prepared by preparing silver halide in advance. In advance, this may be added to a solution for preparing an organic silver salt, or a combination of these methods is possible, but the latter is preferred.

In general, the silver halide is preferably contained in an amount of 0.75 to 30% by weight based on the organic silver salt.

The silver halide grains used in the present invention include F
It preferably contains a metal complex selected from e, Co, Ru, Rh, Re, Os, and Ir, and one or more of the same or different metal complexes may be used in combination. The content of the metal complex is 1 × 10 ^-9 to 1 × 1 per mole of silver.
The range is preferably from 0 to ² mol, more preferably from 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ .

The transition metal complex is represented by the following general formula:
Coordination complexes are preferred.

In the formula [ML ₆ ] ^m , M is a transition metal selected from the elements of Groups 6 to 10 of the periodic table, L is a bridging ligand, and m is 0, 1-, 2-, or 3-.
Or 4-. Specific examples of the ligand represented by L include halides (fluoride, chloride, bromide and iodide), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aquo. Ligand, nitrosyl, thionitrosyl and the like, preferably aquo, nitrosyl and thionitrosyl. If an aquo ligand is present, it preferably occupies one or two of the ligands. L may be the same,
May be different.

Preferred specific examples when M is rhodium (Rh), ruthenium (Ru), rhenium (Re), osmium (Os) and iridium (Ir) are shown below.

[0048] 1: [RhCl _6] ^3- 2: [RhCl ₅ (H ₂ O)] ^2- 3: [Rh (NO) ₂ Cl _4] ^- 4: _{[Rh (NO) (H 2 O} ) Cl 4 ] ^- 5: [Rh (NS) Cl _5] ^2- 6: [RuCl _6] ^3- 7: [RuBr _6] ^3- 8: [Ru (NO) Cl _5] ^2- 9: [Ru (NO) ( H ₂ O) Cl _4] ^- 10: [Ru (NS) Cl _5] ^2- 11: [RuBr ₄ (H ₂ O)] ^2- 12: [Ru (NO) (CN) _5] ^2- 13: [ ReCl _6] ^3- 14: [Re (NO) Cl _5] ^2- 15: [Re (NO) (CN) _5] ^2- 16: [Re (NO) Cl (CN) 4 ] ^2- 17: [Re (NO) Cl _5] ^- 18: _{[Re (NS) Cl 4 (SeCN} ) ] ^2- 19: [OsCl _6] ^3- 20: [Os (NO) Cl _5] ^2- 21: [Os (NS) Cl ₄ (TeCN)] ^2- 2: [Os (NS) Cl (SCN) 4 ] ^2- 23: [IrCl _6] ^2- 24: [Ir (NO) Cl _5] ^2- chromium, cobalt, 6-cyano metal complexes for iron compounds preferably Can be used. Specific examples are shown below.

25: [Cr (CN) ₆ ] ^3- 26: [Cr (CN) ₆ ] ^4-27 : [Fe (CN) ₆ ] ^4-28 : [Fe (CN) ₆ ] ^3-29 : [ Co (CN) ₆ ] ^3- A compound that provides an ion or a complex ion of these metals is preferably added during silver halide grain formation and incorporated into the silver halide grains. That is, nucleation, growth, physical ripening, may be added at any stage before and after chemical sensitization, but it is preferable to add at the stage of nucleation, growth, physical ripening, and further, at the stage of nucleation and growth. It is preferably added, most preferably at the stage of nucleation. During the addition, it may be added in several divided portions, may be uniformly contained in the silver halide grains, or may be added, as described in JP-A-63-29603.
JP-A-2-306236, JP-A-3-167545, JP-A-4-76534, JP-A-6-110146, and JP-A-5-27
As described in, for example, No. 3683, etc., it can be contained in the particles with a distribution. Preferably, a distribution can be provided inside the particles.

These metal compounds can be prepared by using water or a suitable organic solvent (alcohols, ethers, glycols,
Ketones, esters, amides, etc.). For example, an aqueous solution of a metal compound or an aqueous solution in which a metal compound and NaCl and KCl are dissolved together may be added to a water-soluble silver salt during grain formation. Solution or a water-soluble halide solution, or a method in which a silver salt solution and a halide solution are simultaneously mixed and added as a third aqueous solution to prepare silver halide grains by a three-solution simultaneous mixing method. A method in which a required amount of an aqueous solution of a metal compound is charged into a reaction vessel during grain formation, or another silver halide grain doped with metal ions or complex ions in advance during silver halide preparation is added and dissolved. There are methods. In particular, an aqueous solution of a metal compound or a metal compound and NaC
1, a method of adding an aqueous solution in which KCl is dissolved together to a water-soluble halide solution is preferable. When adding to the particle surface, a required amount of an aqueous solution of a metal compound can be charged into the reaction vessel immediately after the formation of the particles, during or at the end of physical ripening, or at the time of chemical ripening.

The photosensitive silver halide grains can be obtained by a noodle method,
Desalting can be performed by a known desalting method such as flocculation method, ultrafiltration method, and electrodialysis method.

The photosensitive silver halide grains in the present invention are preferably chemically sensitized. Examples of the sensitization method include known methods such as sulfur sensitization, selenium sensitization, tellurium sensitization, noble metal sensitization and reduction sensitization. Sensitization method can be used. These sensitization methods can be used in combination of two or more.

For sulfur sensitization, thiosulfates, thiourea compounds, inorganic sulfur and the like can be used. Compounds preferably used for selenium sensitization and tellurium sensitization include the compounds described in JP-A-9-230527. Compounds preferably used in the noble metal sensitization method include, for example, chloroauric acid, potassium chloroaurate, potassium aurithiocyanate, gold sulfide, gold selenide, US Pat. No. 2,448,060, and British Patent 618,0
No. 61 and the like.

As the shell-like compound in the reduction sensitization method, ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds and the like can be used. Further, reduction sensitization can be achieved by ripening the emulsion while maintaining the pH of the emulsion at 7 or more or the pAg at 8.3 or less.

In the photothermographic material, dyes such as cyanine, merocyanine, complex cyanine, complex merocyanine, holopolar cyanine, styryl, hemicyanine, oxonol and hemioxonol can be used as spectral sensitizing dyes. For example, JP-A-63
-159841, 60-14335, 63-
No. 231437, No. 63-259651, No. 63-3
04242, 63-15245, U.S. Pat.
39,414, 4,740,455, 4,74
1,966, 4,751,175, 4,83
Sensitizing dyes described in US Pat. No. 5,096 can be used.

Useful sensitizing dyes for use in the present invention include, for example, Research Disclosure (hereinafter, referred to as “Research Disclosure”).
RD), Item 17643, Section IV-A (197
December 1983, page 23), Item 1831, Item X (1
(August 978, p. 437). In particular, a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light source of the photothermographic material for various laser imagers and scanners can be advantageously selected. For example, JP-A-9-34078 and JP-A-9-5440
Compounds described in Nos. 9 and 9-80679 are preferably used.

Useful cyanine dyes are 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 a thiohydantoin nucleus, a rhodanine nucleus, an oxazolidinedione nucleus, a thiazolinedione nucleus, a barbituric acid nucleus, a thiazolinone nucleus, a malononitrile nucleus and a pyrazolone nucleus. Including.

These sensitizing dyes may be used alone or in combination, and the combination of sensitizing dyes is often used particularly 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 represented by R
D, Item 17643 (described above), page 23, section 1V-J,
Or, the aforementioned Japanese Patent Publication No. 9-25500 and 43-4933.
JP-A-59-19032 and JP-A-59-192242.
No. etc.

In the present invention, the organic silver salt is a reducible silver source, and a silver salt of an organic acid or a heteroorganic acid containing a reducible silver ion source, particularly a long chain (10 to 30, preferably 15 to 30, Silver salts of aliphatic carboxylic acids having 28 carbon atoms) are preferred. Organic or inorganic silver salt complexes wherein the ligand has a complex stability constant for silver ions of 4.0 to 10.0 are also useful.

Examples include: silver salts of organic acids (gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, lauric acid, oleic acid, caproic acid, myristic acid, palmitic acid, maleic acid, linoleic acid Salt, etc.);
Silver carboxyalkylthiourea salts (1- (3-carboxypropyl) thiourea, 1- (3-carboxypropyl) -3,3-dimethylthiourea, etc.); polymer reaction products of aldehydes and hydroxy-substituted aromatic carboxylic acids (Eg, formaldehyde, acetaldehyde, butyraldehyde), hydroxy-substituted acids (eg, salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid), and silver salts or complexes of thiones (3-carboxyethyl-4-hydroxymethyl-4-thiazoline-2-thione, 3-carboxymethyl-4-thiazoline-2-thione, etc.); imidazole, pyrazole, urazole, 1,2,4-thiazole and 1
H-tetrazole, 3-amino-5-benzylthio-
Complexes or salts of silver with a nitrogen acid selected from 1,2,4-triazole and benzotriazole; saccharin, 5
Silver salts such as chlorosalicylaldoxime; and silver salts of mercaptides. Examples of suitable silver salts are described in RD, Item 17
029 and 29996, and a particularly preferred silver source is silver behenate.

The organic silver salt compound can be obtained by mixing a water-soluble silver compound and a compound which forms a complex with silver, and can be obtained by a forward mixing method, a reverse mixing method, a simultaneous mixing method, and a method described in JP-A-9-12764.
A controlled double jet method as described in No. 3 is preferably used.

The shape of the organic silver salt used in the present invention is not particularly limited, but a needle crystal having a short axis and a long axis is preferable. As is well known for silver halide photosensitive materials,
The inverse relationship between the size of the silver salt crystal grains and the covering power is also established in the photothermographic material of the present invention. That is, when the organic silver salt particles which are the image forming portions of the photothermographic material are large, the covering power is large. Therefore, it is necessary to reduce the size of the organic silver salt.

In the present invention, the short axis is 0.01 to 0.20.
μm, the major axis is preferably 0.10 to 5.0 μm, and the minor axis is 0.1 μm.
More preferably, the length is from 0.1 to 0.15 μm and the major axis is from 0.10 μm to 4.0 μm. The particle size distribution of the organic silver salt is preferably monodispersed. Monodispersion means that the percentage of the value obtained by dividing the standard deviation of the length of each of the minor axis and major axis by the minor axis and major axis is preferably 100% or less, more preferably 80% or less, and even more preferably 50% or less. Good. The shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion.

As another method for measuring the monodispersity, there is a method of obtaining the standard deviation of the volume-weighted average diameter of the organic silver salt, and the percentage (coefficient of variation) of the value divided by the volume-weighted average diameter is known.
Is preferably 100% or less, more preferably 80% or less, and still more preferably 50% or less. As a measuring method, for example, the organic silver salt dispersed in a liquid is irradiated with laser light, and the autocorrelation coefficient with respect to the time variation of the fluctuation of the scattered light is obtained, from the particle size (volume weight average diameter) obtained. You can ask.

[0065] The coating amount of the organic silver salt, in particular an organic acid silver in the photosensitive material of the present invention the light-sensitive material per m ² O. 5-5.0
g is preferable, and 1.0 to 3.0 g is more preferable.

Examples of reducing agents suitable for the photothermographic material of the present invention are described in US Pat. Nos. 3,770,448 and 3,773.
No. 512, No. 3,593,863, and RD1702
9 and 29996, and include the following.

Aminohydroxycycloalkenonone compounds (such as 2-hydroxypiperidino-2-cyclohexenone); amino reductone esters (such as piperidinohexose reductone monoacetate) as precursors of reducing agents; N-hydroxyurea Derivatives (such as Np-methylphenyl-N-hydroxyurea); hydrazones of aldehydes or ketones (such as anthracenaldehyde phenylhydrazone); phosphoramidophenols; phosphoramidoanilines; polyhydroxybenzenes (hydroquinone, t -Butyl-hydroquinone, isopropylhydroquinone and (2,5-dihydroxy-phenyl) methylsulfone and the like); sulfhydroxamic acids (such as benzenesulfhydroxamic acid); and sulfonamidoanilines (4- (N-methanes Hon'amido) aniline); 2
-Tetrazolylthiohydroquinones (2-methyl-5-
(1-phenyl-5-tetrazolylthio) hydroquinone and the like); tetrahydroquinoxalines (1,2,3,4-
Amidoxins; azines (such as a combination of aliphatic carboxylic acid arylhydrazides and ascorbic acid); combinations of polyhydroxybenzene and hydroxylamine, reductone and / or hydrazine; hydroxanoic acids; azines and sulfonamides Combinations of phenols; α-cyanophenylacetic acid derivatives; combinations of bis-β-naphthol and 1,3-dihydroxybenzene derivatives; 5-pyrazolones; sulfonamide phenol reducing agents; 2-phenylindane-1,3-
Dione, etc .; chroman; 1,4-dihydropyridines (2,6-dimethoxy-3,5-dicarboethoxy-
Bisphenols (bis (2-hydroxy-3-t-butyl-5-methylphenyl) methane, bis (6-hydroxy-m-tri) mesitol), 2,2-bis (4 -Hydroxy-3-methylphenyl) propane, 4,5-ethylidene-bis (2-
t-butyl-6-methyl) phenol and the like); UV-sensitive ascorbic acid derivatives and 3-pyrazolidones.

Among these, particularly preferred reducing agents are hindered phenols. Examples of the hindered phenols include compounds represented by the following general formula (A).

[0069]

Embedded image

In the formula, R ₁ is a hydrogen atom or a group having 1 to 1 carbon atoms.
Represents 10 alkyl groups (methyl, ethyl, propyl, i-propyl, 2,4,4-trimethylpentyl, etc.),
R ₂ and R ₃ each represent an alkyl group having 1 to 5 carbon atoms (eg, methyl, ethyl, propyl, t-butyl).

Specific examples of the compound represented by the formula (A) (hereinafter referred to as the reducing agent of the present invention) are shown below, but the present invention is not limited thereto.

[0072]

Embedded image

The amount of the reducing agent used in the present invention is preferably 1 × 10 ⁻² to 10 mol, more preferably 1 × 10 ⁻² to 10 mol, per mol of silver.
× 10 ^{-2 to} 1.5 mol.

Binders suitable for the photothermographic material 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, polyvinyl alcohol, and hydroxy. Ethyl cellulose, cellulose acetate, cellulose acetate butyrate, polyvinylpyrrolidone, casein, starch, polyacrylic acid, polymethyl methacrylate, polyvinyl chloride, polymethacrylic acid, styrene-maleic anhydride copolymer, styrene-acrylonitrile copolymer, styrene -Butadiene copolymer, polyvinyl acetal (polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resin, polyvinylidene chloride, polyepoxides, Polycarbonate, polyvinyl acetate, cellulose esters, and polyamides.
The binder may be hydrophilic or non-hydrophilic.

In the present invention, a matting agent is preferably provided on the surface of the light-sensitive material in order to prevent the image after thermal development from being damaged, and the matting agent is used in a weight ratio to the total binder on the emulsion layer side. Is preferably 0.5 to 10%.

The material of the matting agent used in the present invention may be either an organic substance or an inorganic substance. For example, as inorganic substances, silica described in Swiss Patent No. 330,158, glass powder described in French Patent No. 1,296,995, alkaline earth metal described in British Patent No. 1,173,181 or the like can be used. An inorganic matting agent such as a carbonate such as cadmium and zinc can be used. As organic substances, U.S. Pat.
2,037, etc., Belgian Patent 625,4
No. 51 and British Patent Nos. 981,198, etc .; polyvinyl alcohol described in JP-B-44-3643, etc .; polystyrene or polymethacrylate described in Swiss Patent No. 330,158, U.S. Pat.
Organic matting agents such as polyacrylonitrile described in US Pat. No. 9,257 and the like and polycarbonate described in US Pat. No. 3,022,169 can be used.

The shape of the matting agent may be either regular or irregular, but preferably regular and spherical. The size of the matting agent is represented by a diameter when the volume of the matting agent is converted into a sphere. The particle diameter of the matting agent in the present invention indicates the diameter converted into a sphere.

The matting agent used in the present invention preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm. The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less. Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

(Standard deviation of particle size / average value of particle size) × 100 The matting agent can be contained in any constituent layer, but in order to achieve the object of the present invention, it is preferable to use a matting agent other than the photosensitive layer. It is a constituent layer, particularly preferably the outermost layer as viewed from the support.

The method of adding the matting agent may be a method of dispersing in a coating solution in advance and applying the same, or a method of applying the coating solution and spraying the matting agent before drying is completed. Is also good. When a plurality of types of matting agents are added, both methods may be used in combination.

The photothermographic material of the present invention forms a photographic image by a heat development process, and includes a reducible silver source (organic silver salt), a catalytically active amount of silver halide, a hydrazine derivative,
A reducing agent and, if necessary, a color tone agent for adjusting the color tone of silver,
In general, it is preferable that the binder resin is contained in a dispersed state in an (organic) binder matrix.

Although the photothermographic material is stable at room temperature, it is developed by heating to a high temperature (80 ° C. to 140 ° C.) after exposure. Organic silver salt by heating (acts as oxidizing agent)
Silver is produced through an oxidation-reduction reaction between the catalyst and a reducing agent.
This oxidation-reduction reaction is accelerated by the catalytic action of the latent image generated on the silver halide upon exposure. The silver formed by the reaction of the organic silver salt in the exposed areas provides a black image, which contrasts with the unexposed areas to form an image. This reaction process proceeds without supplying a processing liquid such as water from the outside.

The photothermographic material of the present invention has at least one photosensitive layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to have at least one non-photosensitive layer on the photosensitive layer. In order to control the amount or wavelength distribution of light passing through the photosensitive layer, a filter layer may be provided on the same side or the opposite side as the photosensitive layer, or a dye or pigment may be included in the photosensitive layer. . As the dye, compounds described in JP-A-8-201959 are preferred.
The photosensitive layer may be composed of a plurality of layers.
The photosensitive layer may be a high-sensitivity layer / low-sensitivity layer or a low-sensitivity layer / high-sensitivity layer.

Various additives may be added to any of the photosensitive layer, the non-photosensitive layer and other forming layers. As an additive, for example, a surfactant, an antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber, a coating aid, or the like may be used.

In the present invention, it is preferable to add a color tone agent. Toning agents are disclosed in U.S. Pat. No. 3,080,254,
As shown in JP-A-3,847,612 and JP-A-4,123,282, it is a material well known in the photographic art.
Examples of suitable toning agents are disclosed in RD, Item 17029 and include:

Imides (succinimide, phthalimide, etc.); cyclic imides, pyrazolin-5-ones, quinazolinones (3-phenyl-2-pyrazolin-5-one,
1-phenylurazole, quinazoline, 2,4-thiazolidinedione, etc.); naphthalimides (N-hydroxy-1,8-naphthalimide, etc.); cobalt complexes (hexamine trifluoroacetate of cobalt, etc.); mercaptans (3-mercapto N- (aminomethyl) aryldicarboximides (N- (dimethylaminomethyl) phthalimide, etc.); blocked pyrazoles, isothiuronium derivatives, and certain photobleaching Combinations of agents (N, N'-hexamethylene (1-carbamoyl-3,5-dimethylpyrazole), 1,8- (3,6-dioxaoctane) bis (isothiuronium trifluoroacetate), 2-
(Combination of (tribromomethylsulfonyl) benzothiazole and the like); merocyanine dye (3-ethyl-5- (2-
(3-ethyl-2-benzothiazolinylidene))-1-
Methylethylidene) -2-thio-2,4-oxazolidinedione, etc.); phthalazinone, phthalazinone derivatives or metal salts of these derivatives (4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxy) Phthalazinone, 2,3-dihydro-1,4-phthalazinedione, etc.); a combination of phthalazinone and a sulfinic acid derivative (6-chlorophthalazinone + sodium benzenesulfinate or 8-methylphthalazinone + p-trisulfonic acid) Sodium, etc.); a combination of phthalazine and phthalic acid; phthalazine (including an adduct of phthalazine) and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or an o-phenylene acid derivative and its anhydride (phthalic acid) , 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic Combination with at least one compound selected from the anhydrous and the like); quinazoline compounds, benzoxazine, Narutokisajin derivatives; benzoxazine-2,4-diones (1,3-benzoxazin -
2,4-dione and the like); pyrimidines and asymmetric triazines (2,4-dihydroxypyrimidine and the like), and tetraazapentalene derivatives (3,6-dimercapto-1,
4-diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene and the like).

The preferred toning agent is phthalazone or phthalazine.

In the present invention, a mercapto compound, a disulfide compound, a thione compound, or a thione compound is used for the purpose of controlling or developing by controlling or accelerating the development, or for improving the spectral sensitization efficiency, or for improving the storage stability before and after the development. Compounds can be included.

When a mercapto compound is used, it may have any structure, but may be ArSM or Ar-SS-
Compounds represented by Ar are preferred. In the formula, M is a hydrogen atom or an alkali metal atom, Ar is one or more nitrogen,
An aromatic ring or a condensed aromatic ring having a sulfur, oxygen, selenium or tellurium atom. Preferably a heteroaromatic ring,
Benzimidazole, naphthymidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzoterzole, imidazole, oxazole, pyrazole, triazole, thiadiazole, tetrazole, triazine,
Pyrimidine, pyridazine, pyrazine, pyridine, purine, quinoline, quinazolinone and the like. The heteroaromatic ring includes a halogen (chlorine, bromine, etc.), a hydroxyl group, an amino group, a carboxyl group, an alkyl group (preferably 1-4).
May have a substituent selected from the group consisting of a substituent having one carbon atom and an alkoxy group (preferably having one to four carbon atoms). Examples of the mercapto-substituted heteroaromatic compound include 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-mercapto-5-methylbenzimidazole, 6-ethoxy-2-mercaptobenzothiazole, and 2,2. '-Dithiobisbenzothiazole, 3-mercapto-1,2,4-triazole,
4,5-diphenyl-2-imidazolethiol, 2-
Mercaptoimidazole, 1-ethyl-2-mercaptobenzimidazole, 2-mercaptoquinoline, 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-hydroxy-
2-mercaptopyrimidine, 2-mercaptopyrimidine, 4,6-diamino-2mercaptopyrimidine, 2-mercaptopyrimidine
Mercapto-4-methylpyrimidine hydrochloride, 3
-Mercapto-5-phenyl-1,2,4-triazole, 2-mercapto-4-phenyloxazole and the like, but are not limited thereto.

The amount of the mercapto compound to be added is preferably in the range of 0.001 to 1.0 mol, more preferably 0.01 to 0.3 mol, per mol of silver in the emulsion layer.

What is known as the most effective antifoggant is mercury ion. The use of a mercury compound as an antifoggant in a light-sensitive material is disclosed in, for example, US Pat. No. 3,589,903. However, mercury compounds are environmentally unfriendly. Non-mercury antifoggants include, for example, US Pat. No. 4,546,075.
No. 4,452,885 and JP-A-59-5723.
No. 4 is preferred.

Particularly preferred non-mercury antifoggants are compounds such as those disclosed in US Pat. Nos. 3,874,946 and 4,756,999, —C (X ₁ ) (X ₂ )
(X ₃ ) (where X ₁ and X ₂ are each a halogen atom,
X ₃ is a heterocyclic compound having one or more substituents represented by a hydrogen atom or a halogen atom). As preferred examples of the antifoggant, compounds described in JP-A-9-90550, paragraphs [0062] to [0063] are preferably used. Further, more preferred antifoggants are
U.S. Pat. No. 5,028,523 and British Patent Application 922
Nos. 21383.4, 9300147.7, 931
No. 1790.1.

In the photosensitive layer of the present invention, a polyhydric alcohol (US Pat. No. 2,960,40) is used as a plasticizer and a lubricant.
Glycerin and diols of the type described in US Pat. No. 4,588,765 and US Pat. No. 3,121,060.
Fatty acids or esters described in British Patent No. 955,06
For example, the silicone resin described in No. 1 can be used.

A hardener may be used in each of the layers such as the photosensitive layer, the protective layer and the back layer. Examples of the hardener include isocyanate compounds, epoxy compounds described in U.S. Pat. No. 4,791,042, and vinylsulfone compounds described in JP-A-62-89048.

A surfactant may be used for the purpose of improving coating properties and charging. As an example of the surfactant, any surfactant such as anionic, cationic, betaine, nonionic, and fluorine can be appropriately used. Specifically, fluorine polymer surfactants described in JP-A-62-170950, U.S. Pat. No. 5,382,504, and the like;
Fluorinated surfactants described in JP-A Nos. 4945 and 63-188135, polysiloxane-based surfactants described in U.S. Pat. No. 3,885,965, JP-A-6-301140
And the like, polyalkylene oxides and anionic surfactants.

The photographic emulsion for heat development can be prepared by dip coating, air knife coating, flow coating, or US Pat.
Various coating methods can be used, including extrusion coating using a hopper of the type described in U.S. Pat.
If desired, two or more layers can be applied simultaneously by the methods described in U.S. Pat. No. 2,761,791 and British Patent 837,095.

The photographic emulsion for thermal development of the present invention can be prepared by various coating methods including a dip coating method, an air knife coating method, a flow coating method, and an extrusion coating method using a hopper of the kind described in US Pat. No. 2,681,294. Can be used. If necessary, two or more layers can be applied simultaneously by the methods described in US Pat. No. 2,761,791 and British Patent 837,095.

The support used for the photothermographic material is made of a plastic film (polyethylene terephthalate, polycarbonate, polyimide, nylon, cellulose, etc.) in order to obtain a predetermined optical density after development and to prevent deformation of the image after development. Triacetate, polyethylene naphthalate, etc.). Among them, preferred supports include polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
And a plastic (SPS) support containing a styrene-based polymer having a syndiotactic structure.
The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

Further, a plastic support which has been heat-treated can also be used. The plastics to be employed include the above-mentioned plastics. The heat treatment of the support means that after the support is formed, before the photosensitive layer is coated, the glass transition point of the support is 30 ° C. or higher (preferably 35 ° C. or higher, more preferably 40 ° C. or higher). (° C. or higher). However, the effect of the present invention cannot be obtained by heating at a temperature exceeding the melting point of the support.

Next, the plastic used will be described.

PET is made of polyethylene terephthalate in which all polyester components are used. In addition to polyethylene terephthalate, terephthalic acid, naphthalene-2,6-dicarboxylic acid, isophthalic acid, butylene dicarboxylic acid, and 5-sodium sulfo acid are used as acid components. A polyester containing a modified polyester component of isophthalic acid, adipic acid or the like and a glycol component such as ethylene glycol, propylene glycol, butanediol, cyclohexanedimethanol or the like in an amount of 10 mol% or less of the entire polyester may be used.

As PEN, polyethylene-2,6-
Preference is given to naphthalate, copolyesters composed of terephthalic acid, 2,6-naphthalenedicarboxylic acid and ethylene glycol, and polyesters whose main constituent is a mixture of two or more of these polyesters. Further, another copolymerization component may be copolymerized, or another polyester may be mixed.

SPS is different from ordinary polystyrene (atactic polystyrene) and is a polystyrene having steric regularity. The regular stereoregular structure part of SPS is called a racemo chain, and it is preferable that there be more regular parts such as two, three, five or more. In the present invention, the racemo chain is two-chain. Is preferably 85% or more, 75% or more for 3 chains, 50% or more for 5 chains, and 30% or more for further chains. The polymerization of SPS can be carried out according to the method described in JP-A-3-131843.

As a method for forming a film and a method for producing an undercoat, known methods can be used.
No. 50094, paragraphs [0030] to [0070].

[0105]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1 A photothermographic material was prepared according to the following procedure.

(Preparation of Photosensitive Silver Halide Emulsion A) Water 9
After dissolving 7.5 g of inert gelatin and 10 mg of potassium bromide in 00 ml and adjusting the temperature to 35 ° C. and pH 3.0, 370 ml of an aqueous solution containing 74 g of silver nitrate, potassium bromide and potassium iodide (98/2 molar ratio). And an [Ir (NO) Cl ₅ ] salt in an amount of 1 × 10
^-6 mol and a rhodium chloride salt of 1 × 10 ^-4 per mol of silver
Mole was added in a controlled double jet manner, keeping the pAg at 7.7. Thereafter, 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene was added as a stabilizer, the pH was adjusted to 5 with sodium hydroxide, and the average particle size was 0.06 μm and the projected diameter area was Cubic silver iodobromide grains having a coefficient of variation of 8% and a {100} face ratio of 87% were obtained.

The emulsion was coagulated and precipitated using a gelatin coagulant. After desalting, 0.1 g of phenoxyethanol was added to adjust the pH to 5.9 and the pAg to 7.5 to obtain a silver halide emulsion. Next, 3 × 10 ^-2 mol of sodium thiosulfate per mol of silver was added to this silver halide emulsion, and
The reaction was carried out at 5 ° C. for 60 minutes for chemical sensitization.

(Preparation of silver behenate) JP-A-9-1276
No. 43 According to the method of Example 1, silver behenate was prepared as follows.

34 g of behenic acid was dissolved in 340 ml of i-propanol at 65 ° C. Then 0.25 with stirring
A sodium hydroxide aqueous solution of N was added to adjust the pH to 8.7. At this time, the sodium hydroxide aqueous solution was about 400 m
1 needed. Next, this aqueous solution was concentrated under reduced pressure to adjust the concentration of sodium behenate to 8.9% by weight.

To a solution in which 30 g of ossein gelatin was dissolved in 750 ml of distilled water, a 2.94 M silver nitrate solution was added to adjust the silver potential to 400 mV. Into this, 374 ml of the above sodium behenate solution was added at a temperature of 78 ° C. using a controlled double jet method, and at the same time, 2.
A 94M aqueous silver nitrate solution was added. The amounts of sodium behenate and silver nitrate used at the time of addition were 0.092 mol and 0.101 mol, respectively.

After the addition was completed, the mixture was further stirred for 30 minutes, and the water-soluble salts were removed by ultrafiltration.

(Preparation of Photosensitive Emulsion) To this silver behenate dispersion, 0.01 mol of the above-mentioned silver halide emulsion was added, and while stirring, a butyl acetate solution of polyvinyl acetate (1.2 watts) was added.
(t%) 100 g was gradually added to form flocs of the dispersion, water was removed, and water was washed twice and water was removed. Then, 2.5 wt% of polyvinyl butyral (average molecular weight 3000) was used as a binder. 60 g of a 1: 2 mixed solution of butyl acetate and i-propanol was added with stirring, and then the mixture of gel-like behenic acid and silver halide thus obtained was added with polyvinyl butyral (average molecular weight 4000) and i. -Propanol was added and dispersed.

(Formation of Layer on Support Surface) Hereinafter, "parts" indicating the amounts of the respective coating liquids represent "parts by weight" of solids or nonvolatile components.

[0115] support layer forming coating liquid of the surface dry silica fine particles (average primary particle diameter: 7 nm, refractive index: 1.45, Aerosil A300: manufactured by Nippon Aerosil Co., Ltd.) Table 1, wherein the amount of polyvinyl alcohol (saponification degree: 88 %, Degree of polymerization: 3500, PVA235: manufactured by Kuraray Co., Ltd.) Table 1 Amount of ion-exchanged water 100 parts Dry fine silica particles were added to ion-exchanged water (70 parts), and a high-speed rotating wet colloid mill (CLEARMIX: M Technic) 20) under the conditions of 10,000 rpm for 20 minutes, and then an aqueous solution of polyvinyl alcohol (dissolved in the remaining 60 parts of ion-exchanged water) was added, followed by dispersion under the same conditions as described above. A coating solution for forming a layer on the surface was prepared.

The coating solution for forming a layer on the surface of the support was applied to the surface of a biaxially stretched PET film (refractive index: 1.64) having a thickness of 175 μm and having a corona discharge treatment, using an air knife coater. 70 ℃ by hot air dryer
After drying at a wind speed of 5 m / sec for 1 minute, the film was further dried at 100 ° C. for 10 minutes. Thus, a support surface layer having a dry film thickness of 0.1 μm was formed.

(Formation of Photosensitive Layer) A coating solution for forming a photosensitive layer having the following composition was applied so that the amount of silver applied was 2.0 g / m ² and polyvinyl butyral as a binder was 6.5 g / m ² .

Coating solution for forming photosensitive layer Photosensitive silver halide emulsion A 0.1 g / m ² (in terms of silver) Silver behenate 1.9 g / m ² (in terms of silver) Sensitizing dye-1 (0.1% dimethyl Formamide solution) 2 mg Antifoggant-1 (0.01% methanol solution) 3 ml Antifoggant-2 (1.5% methanol solution) 8 ml Antifoggant-3 (2.4% dimethylformamide solution) 5 ml Phthalazone (4 8% dimethylformamide solution)

[0119]

Embedded image

(Formation of Surface Protective Layer) A solution having the following composition was coated on each photosensitive layer so as to have a wet thickness of 100 μm. However, the reducing agent A-4 (10% acetone solution) was adjusted and added so that the optical transmission density of the unexposed portion after development was 0.15.

Coating solution for forming surface protective layer Acetone 175 ml i-propanol 40 ml methanol 15 ml cellulose acetate 8.0 g phthalazine 1.0 g 4-methylphthalic acid 0.72 g tetrachlorophthalic acid 0.22 g tetrachlorophthalic anhydride 0.5 g 1% by weight based on monodisperse silica binder having an average particle size of 4 μm In this way, photothermographic materials (samples 1 to 6) as shown in FIG. 1 were obtained.

(Exposure and Development Processing) Each of the photothermographic materials prepared above was exposed to a step wedge image using a laser imager having a 820 nm semiconductor laser. Thereafter, heat development was performed at 110 ° C. for 15 seconds using an automatic developing machine having a heat drum. At that time, exposure and development were performed in a room conditioned at 23 ° C. and 50% RH.

For each photothermographic material, the refractive index of the layer on the surface of the support was measured. In addition, applicability, sensitivity, and transparency on Schaukasten were evaluated.

<< The refractive index of the layer on the surface of the support >> The coating solution for forming the layer on the surface of the support is applied on the PET film (the side on which the photosensitive layer is not formed), and the film thickness is adjusted in the same manner as described above. A 0.1 μm transparent layer was formed, and this was measured at a wavelength of 633 nm using an automatic ellipsometer (DHA-XA: manufactured by Mizojiri Optical Industrial Co., Ltd.).

<< Applicability >> When coating each sample, the coating solution could be applied without any problem, and x otherwise.
Displayed with.

<< Sensitivity >> For each sample, fog +1.0
The reciprocal of the exposure required to obtain the density of
The relative sensitivity was represented by setting the sensitivity of the sample to 100.

<< Transparency on Shakasten >> The sample after the heat development was placed on the shakasten and observed, and evaluated by visual observation on a three-point scale.

1: good without clouding 2: slightly cloudy 3: the whole sample is cloudy and difficult to see on diagnosis Table 1 also shows the obtained results.

[0129]

[Table 1]

The evaluations of the samples of the present invention were favorable.

Example 2 Photothermographic materials (samples 11 to 16) were prepared by changing the layer on the support surface in Example 1 as follows.

(Formation of Layer on Support Surface ) Coating Solution for Forming Layer on Support Surface Fluorine-containing polymer (polytrifluoroethyl acrylate) The amount described in Table 2 Methyl ethyl ketone The amount described in Table 2 Acetone 25 parts 175 μm thick biaxially stretched. The PET surface is subjected to a corona discharge treatment, and the coating solution for forming a layer on the support surface is applied to the surface using a bar coater # 26, and dried at 120 ° C. for 20 minutes to form a layer having a thickness of 2 μm on the support surface. Was formed.

A coating solution for forming a photosensitive layer and a surface protective layer was prepared in the same manner as in Example 1, and a support surface layer, a photosensitive layer,
A photothermographic material provided with a protective layer in this order was obtained (see FIG. 2). The refractive index, applicability, sensitivity, and transparency on Schaukasten were measured in the same manner as in Example 1.

Table 2 shows the results.

[0135]

[Table 2]

The samples of the present invention were favorable in all evaluations.

[0137]

According to the present invention, a photothermographic material having excellent sensitivity, no problem in coating property, and no devitrification after heat development can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a basic configuration of a photothermographic material according to the present invention.

FIG. 2 is a sectional view showing another example of the basic structure of the photothermographic material of the present invention.

[Explanation of symbols]

 11, 21 Support 12, 22 Layer on Support 13, 13, Photosensitive Layer 14, 24 Protective Layer

Claims (4)

[Claims] 1. A photothermographic material having a photosensitive layer containing an organic silver salt, photosensitive silver halide grains and a reducing agent on a support, wherein a photoconductive layer is provided between the support and the photosensitive layer. A photothermographic material comprising a layer containing inorganic fine particles on a support opposite to the side having the fine particles. 2. A photothermographic material having a photosensitive layer containing an organic silver salt, photosensitive silver halide grains and a reducing agent on a support, wherein a photoconductive layer is provided between the support and the photosensitive layer. A photothermographic material comprising a fluorine atom-containing polymer layer on a support opposite to the side having the polymer. 3. The layer containing inorganic fine particles or the fluorine atom-containing polymer layer has voids.
Or a photothermographic material according to item 2. 4. The photothermographic material according to claim 1, wherein the refractive index of the layer containing inorganic fine particles or the fluorine atom-containing polymer layer is 1.50 or less.