JP2000122219A - Preparation of organic silver salt dispersion, and heat developable photosensitive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make preparable a photosensitive emulsion having high dispersibility and low fog and to suppress the inclusion of impurities due to the friction of an apparatus and media in dispersion by using a nonmetal as a material of a medium agitation type dispersing machine coming into contact with ceramic beads. SOLUTION: A medium agitation type dispersing machine agitates a stock fluid poured from the inlet 1 together with ceramic beads 3 by means of a rotor 2 and disperses the stock fluid. Parts of the rotor 2 and a stator 4 subjected to contact with the ceramic beads 3 comprise a nonmetal. An inorganic material such as a carbon or graphite material or ceramics or an organic material such as a resin is used as the nonmetal. The ceramic beads 3 preferably comprise yttrium stabilized zirconia or zirconia reinforced alumina less liable to produce impurities by the friction of the beads and the dispersing machine in dispersion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an organic silver salt dispersion and a photothermographic material containing the organic silver salt dispersion prepared by using the method.

[0002]

2. Description of the Related Art In recent years, in the medical field, X-ray CT, MR
As a means for outputting a diagnostic image such as I, a method has been adopted in which a photosensitive material is scanned with a laser beam and exposed to form an image. However, these photosensitive materials have been subjected to wet development processing after imagewise exposure by scanning with a laser beam and subjected to diagnosis.

In wet processing of photosensitive materials, waste liquid is a problem in terms of environmental protection. In recent years, it has been strongly desired to reduce the amount of processing waste liquid from the viewpoint of space saving.

Therefore, there has been a demand for a technique relating to a photothermographic material capable of efficiently exposing with a laser imager and forming a high-resolution and clear black image.

As this technique, for example, US Pat.
No. 152,904, No. 3,487,075 and D.C.
"Dry Silver Photographi" by Morgan
c Materials) "(Handbook of
Imaging Materials, Marcel
Dekker, Inc. 48, 1991), a photothermographic material containing an organic silver salt, photosensitive silver halide grains and a reducing agent on a support is known. Further, a heat-developable material which does not contain photosensitive silver halide grains and forms an image by thermal energy is widely known.

An essential component of the photothermographic material or the photothermographic material is an organic silver salt. A method for producing an organic silver salt dispersion containing silver halide is described, for example, in US Pat. No. 3,839. , 049 discloses a method of dispersing by a ball mill which is a rolling type medium dispersing machine.

However, in the dispersing method described in the above patent, the ball mill performs pulverization and dispersion by the avalanche motion of the medium filled with about 50% of the total volume of the pulverizing chamber. To 30%, the dispersion time is long, and the recovery rate is low. Further, in the medium stirring type disperser with higher productivity, the speed of stirring the medium is high, and impurities are mixed due to abrasion of the apparatus and the medium such as stainless steel, so that the fog of the produced photothermographic material is increased, This was an obstacle to practical application.

[0008]

An object of the present invention is to provide a method for producing an organic silver salt dispersion in which a raw material liquid comprising at least an organic silver salt and photosensitive silver halide particles is dispersed using a medium stirring type disperser. A method for producing an organic silver salt dispersion having good processability, which can produce a photosensitive emulsion having high dispersibility and low fogging, and reducing the contamination of impurities due to friction of a device or a medium during dispersion. An object of the present invention is to provide a photothermographic material containing an organic silver salt dispersion prepared using the method.

[0009]

The above objects of the present invention have been attained by the following items.

[0010] 1. In a method of producing an organic silver salt dispersion in which a raw material liquid comprising at least an organic silver salt, photosensitive silver halide particles, a solvent and a binder is dispersed using a medium stirring type disperser, ceramic beads are added to the medium stirring type disperser. A method for producing an organic silver salt dispersion, wherein a non-metal is used for part or all of the medium stirring type disperser that is filled and dispersed, and in contact with the ceramic beads.

2. 2. The method for producing an organic silver salt dispersion according to the above item 1, wherein the ceramic beads are yttrium-stabilized zirconia beads.

3. 2. The method for producing an organic silver salt dispersion according to item 1, wherein the ceramic beads are zirconia reinforced alumina beads.

4. 2. The method for producing an organic silver salt dispersion according to the above item 1, wherein the non-metal is a ceramic.

5. 2. The method for producing an organic silver salt dispersion according to the above 1, wherein the non-metal is a resin.

6. 5. The method for producing an organic silver salt dispersion according to item 4, wherein the ceramic is yttrium-stabilized zirconia.

[7] 5. The method for producing an organic silver salt dispersion according to the item 4, wherein the ceramic is zirconia reinforced alumina.

8. 6. The method for producing an organic silver salt dispersion according to the above item 5, wherein the resin is ultra-high molecular weight polyethylene.

9. 9. A photothermographic material containing the organic silver salt dispersion produced by the production method described in 1, 2, 3, 4, 5, 6, 7, or 8.

Hereinafter, the present invention will be described in detail.

The ceramic used for the ceramic beads used in the present invention includes, for example, Al
₂ O ₃ , BaTiO ₃ , SrTiO ₃ , MgO, ZrO, B
_{eO, Cr 2 O 3, SiO} 2, SiO 2 -Al 2 O 3, Cr 2
O ₃ -MgO, MgO-CaO, MgO-C, MgO-
Al ₂ O ₃ (spinel), SiC, TiO ₂ , K ₂ O, Na
₂ O, BaO, PbO, B ₂ O ₃ , SrTiO ₃ (strontium titanate), BeAl ₂ O ₄ , Y ₃ Al ₅ O ₁₂ , Zr
O ₂ —Y ₂ O ₃ (cubic zirconia), 3BeO—Al ₂ O
₃ -6SiO ₂ (Synthesis emerald), C _{(diamond), Si 2 O-nH 2} O, ticker silicon, yttrium stabilized zirconia, zirconia toughened alumina, and the like are preferable.

Further, a ceramic having a specific gravity of 3.0 or more is preferable, and a ceramic having a specific gravity of 4.0 or more is particularly preferable.

Among the above, for the reason that generation of impurities due to friction with beads and a dispersing machine during dispersion is small,
Yttrium-stabilized zirconia and zirconia-reinforced alumina are particularly preferably used.

An example of the above-mentioned yttrium-stabilized zirconia is a ceramic comprising about 95% of Zr and about 5% of Y. The zirconia-reinforced alumina used in the present invention is ZrO ₂ of 20%. % Represents Al ₂ O ₃ mixed therein.

As the nonmetal used for part or all of the medium stirring type dispersing machine in contact with the ceramic beads used in the present invention, an inorganic material or an organic material is used.

As shown in FIG. 1, the medium stirring type disperser used in the present invention is such that a raw material liquid injected from an inlet 1 is stirred together with ceramic beads 3 using a rotor 2 to disperse the raw material liquid. Device.

The part or all of the medium stirring type dispersing machine in contact with the ceramic beads used in the present invention refers to the rotor (rotating part) 2 and the stator (fixing part) in the dispersing part of the medium stirring type dispersing machine shown in FIG. 4 is a portion in contact with the ceramic beads 3.

As the above-mentioned inorganic material, carbon and graphite materials, glasses, ceramics and the like are preferably used, but ceramics are more preferable, and yttrium-stabilized zirconia or zirconia reinforced alumina is particularly preferably used. is there.

The ceramic has the same meaning as the ceramic used for the ceramic beads.

As the organic material described above, a resin is preferably used.

As the resin described above, hard polyvinyl chloride, polypropylene, polyfukkavinylidene, high-molecular polyethylene, ultra-high-molecular polyethylene, polyurethane and the like are preferably used, and more preferable are ultra-high-molecular polyethylene and polypropylene. Ultra-high molecular polyethylene is particularly preferably used.

The silver halide grains used in the present invention function as an optical sensor. In the present invention, the average particle size is preferably 0.1 μm or less, more preferably 0.01 μm to 0.1 μm, particularly preferably 0.01 μm to 0.1 μm, in order to suppress white turbidity after image formation and obtain good image quality. It is 0.02 μm to 0.08 μm.

When the silver halide grains are cubic or octahedral so-called normal crystals, the grain size refers to the length of the edges of the silver halide grains. In the case of non-normal crystals, for example, in the case of spherical, rod-shaped, or tabular grains, the diameter of a sphere equivalent to the volume of silver halide grains is indicated. Further, the silver halide is preferably monodispersed.

The term “monodispersion” as used herein means a case where the degree of monodispersion determined by the following equation is 40% or less. In the present invention, the monodispersity is more preferably 30% or less, particularly preferably 0.1% or more and 20% or less.

Monodispersity = (standard deviation of particle size) / (average value of particle size) × 100 In the present invention, the silver halide particles have an average particle size of 0.1.
μm or less and more preferably monodisperse particles,
By setting it in this range, the granularity of the image is also improved.

The shape of the silver halide grains is not particularly limited, but the proportion occupied by the Miller index [100] plane is preferably high, and this proportion is 50% or more, more preferably 7%.
It is preferably at least 0%, particularly preferably at least 80%. The ratio of the Miller index [100] plane is determined by the T.M. Tani, J .; Imaging Sci. , 29,
165 (1985).

Another preferred form of silver halide is tabular grains. The term "tabular grain" as used herein means that the thickness in the vertical direction is h.mu.
When m, the aspect ratio = r / h means 3 or more. Among them, the aspect ratio is more preferably 3 or more and 50 or less. The particle size is preferably 0.1 μm or less, more preferably 0.01 μm to 0.08 μm. These are described in U.S. Patent Nos. 5,264,337, 5,314,798, and 5,320,958, and the desired tabular grains can be obtained with reference to the above patents. .

When these tabular grains are used in the present invention, the sharpness of an image is further improved. The halogen composition is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide. AgX particles used in the present invention are P.A. Glafk
Chimie et Physique P
photographique (Paul Montel)
G., 1967); F. Duffin's Pho
graphical Emulsion Chemis
try (published by The Focal Press, 1966)
Year), V. L. Mak by Zelikman et al
ing and Coating Photograph
hic Emulsion (The Focal Pr
ess, 1964) and the like, and can be prepared using an Ag emulsion prepared by a method described in US Pat.

The silver halide used in the present invention is preferably contained in an amount of 0.75 to 30% by weight based on the organic silver salt.

The silver halide used in the present invention preferably contains metal ions belonging to groups 6 to 11 of the periodic table. As the above metals, W, Fe, Co,
Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, P
t and Au are preferred.

These metal ions can be introduced into silver halide in the form of a metal complex or a metal complex ion. As these metal complexes or metal complex ions, hexacoordinate metal complexes represented by the following general formula are preferable.

In the formula [ML ₆ ] ^m , M is a transition metal selected from elements of Groups 6 to 11 of the periodic table, L is a ligand, and m is 0,-, 2-, 3- or 4-
Represents 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 or different.

Particularly preferred examples of M are rhodium (Rh), ruthenium (Ru), rhenium (Re), iridium (Ir) and osmium (Os).

Specific examples of transition metal complex ions are shown below, but the present invention is not limited to these.

[0044] 1: [RhCl _6] ^3- 2: [RuCl _6] ^3- 3: [ReCl _6] ^3- 4: [RuBr _6] ^3- 5: [OsCl _6] ^3- 6: [IrCl _6] ^{4 -} 7: [Ru (NO) Cl _5] ^2- 8: [RuBr ₄ (H ₂ O)] ^2- 9: _{[Ru (NO) (H 2 O} ) Cl 4 ] ^- 10: [RhCl ₅ (H ₂ O)] ^2- 11: [Re (NO) Cl _5] ^2- 12: [Re (NO) CN _5] ^2- 13: [Re (NO) ClCN _4] ^2- 14: [Rh (NO) ₂ Cl _4] ^- 15: _{[Rh (NO) (H 2 O} ) Cl 4 ] ^- 16: [Ru (NO) CN _5] ^2- 17: [Fe (CN) _6] ^3- 18: [Rh (NS) Cl _5] ^2- 19: [Os (NO) Cl _5] ^2- 20: [Cr (NO) Cl _5] ^2- 21: [Re (NO) Cl _5] ^- 22: [Os (NS) Cl ₄ (TeCN )] ^2-23: [R (NS) Cl _5] ^2- 24: _{[Re (NS) Cl 4 (SeCN} ) ] ^2- 25: [Os (NS) Cl (SCN) 4 ] ^2- 26: [Ir (NO) Cl _5] ^2- 27: [Ir (NS) Cl _5] ^2- these metal ions may be a metal complex or metal complex ions one type, the metal of the same kind of metal or different may be used alone or in combination. The content of these metal ions, metal complexes or metal complex ions, generally is suitably 1 × 10 ^-9 ~1 × 10 ^-2 mol per mol of silver halide, preferably 1 × 10 ^{- It is 8} to 1 × 10 ^-4 mol.

Compounds which provide these metal ions or complex ions are added when silver halide grains are formed,
It is preferably incorporated into silver halide grains, and may be added at any stage before and after preparation of silver halide grains, that is, nucleation, growth, physical ripening, and chemical sensitization. It is preferably added at the stage of physical ripening, more preferably at the stage of nucleation and growth, and most preferably at the stage of nucleation.

In the addition, it may be added in several divided portions, may be added uniformly in the silver halide grains, or may be added to silver halide grains.
-306236, 3-167545, 4-76
No. 534, No. 6-110146, No. 5-273683
As described in Japanese Patent Application Laid-Open No. H10-284, etc., the particles can be contained in the particles with a distribution. Preferably, a distribution can be provided inside the particles.

These metal compounds can be added by dissolving them in water or a suitable organic solvent (eg, alcohols, ethers, glycols, ketones, esters, amides). A method in which an aqueous solution of a powder or an aqueous solution in which a metal compound and NaCl and KCl are dissolved together is added to a water-soluble silver salt solution or a water-soluble halide solution during grain formation, or a silver salt solution and a halide solution are used. When they are mixed simultaneously, they are added as a third aqueous solution to prepare silver halide grains by a three-liquid 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 a method in which halogen is added. There is a method in which another silver halide grain doped with metal ions or complex ions in advance during the preparation of silver halide is added and dissolved. In particular, a method of adding an aqueous solution of a powder of a metal compound or an aqueous solution in which a metal compound and NaCl and KCl are dissolved together is added to a water-soluble halide solution.

When adding to the particle surface, a necessary 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 silver halide grains used in the present invention may or may not be desalted after grain formation. When desalting is performed, methods known in the art such as a noodle method and a flocculation method are used. Can be desalted by washing with water.

The silver halide grains used in the present invention are preferably chemically sensitized. Preferred chemical sensitization methods are sulfur sensitization, as is well known in the art,
Selenium sensitization and tellurium sensitization can be used. Further, a noble metal sensitization method or a reduction sensitization method of a gold compound, platinum, palladium, an iridium compound or the like can be used. As the compound preferably used in the sulfur sensitization method, the selenium sensitization method, and the tellurium sensitization method, known compounds can be used, and the compounds described in JP-A-7-128768 can be used. Examples of tellurium sensitizers include diacyl tellurides, bis (oxycarbonyl) tellurides,
Bis (carbamoyl) tellurides, diacyl tellurides, bis (oxycarbonyl) ditellurides, bis (carbamoyl) ditellurides, compounds having a P = Te bond, tellurocarboxylates, Te-organyltellurocarboxylates, Use of (poly) tellurides, tellurides, tellurols, telluroacetals, tellurosulfonates, compounds having a P-Te bond, Te-containing heterocycles, tellurocarbonyl compounds, inorganic tellurium compounds, colloidal tellurium, etc. Can be. Compounds preferably used for the noble metal sensitization method include, for example, chloroauric acid, potassium chloroaurate, potassium aurithiocyanate, gold sulfide, gold selenide, US Pat. No. 2,448,060, British Patent No. 618,061 and the like. Can be preferably used.

Specific compounds for the reduction sensitization method include, for example, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds and the like in addition to ascorbic acid and thiourea dioxide. be able to. 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. Further, reduction sensitization can be achieved by introducing a single addition portion of silver ion during grain formation.

The organic silver salt used in the present invention is a reducible silver source and is an organic acid containing a reducible silver ion source. Examples of the organic acid used in the present invention include an aliphatic carboxylic acid, a carbocyclic carboxylic acid, a heterocyclic carboxylic acid, and a heterocyclic compound.
An aliphatic carboxylic acid having 0, preferably 15 to 25 carbon atoms) and a heterocyclic carboxylic acid having a nitrogen-containing heterocyclic ring are preferably used. Moreover, when the ligand is 4.0-10.
Organic silver salt complexes having a total stability constant for silver ions of 0 are also useful.

Examples of the silver salt of an organic acid used in the present invention include Research Disclosure No. 170.
And silver salts of fatty acids (eg, silver salts of gallic acid, oxalic acid, behenic acid, arachidic acid, stearic acid, palmitic acid, lauric acid, etc.); Carboxyalkylthiourea salts (eg, 1- (3-carboxypropyl) thiourea, 1- (3-carboxypropyl) -3,3-dimethylthiourea); polymerization reaction products of aldehydes and hydroxy-substituted aromatic carboxylic acids (E.g., aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) and hydroxy-substituted aromatic carboxylic acids (e.g., salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid, etc.) Silver complex or the like of a polymerization reaction product of), a silver salt or complex of a thione (for example, 3- (2-carbo) (Silethyl) -4-hydroxymethyl-4-thiazoline-2-thione and 3-carboxymethyl-4-thiazoline-2-thione), imidazole, pyrazole, urazole, 1,2,4-thiazole and 1H-tetrazole, -Amino-5-benzylthio-1,2,4-triazole and benzotriazole, and complexes and salts of silver with nitrogen acids; silver salts such as saccharin and 5-chlorosalicylaldoxime; and silver salts of mercaptides . Among the organic silver salts described above, silver salts of fatty acids are preferably used, and silver behenate, silver arachidate and silver stearate are more preferably used.

The dispersion of the aqueous organic silver salt used in the present invention can be obtained by mixing silver nitrate and an alkali metal salt of an organic acid. When the organic silver salt is formed, silver nitrate and silver halide are simultaneously added and mixed. It is preferably produced using a mixing method.

For example, an organic acid alkali metal salt soap (eg, sodium behenate, sodium arachidate, etc.) is prepared by adding an alkali metal hydroxide (eg, sodium hydroxide, potassium hydroxide, etc.) to an organic acid. By using a control double jet method, silver nitrate and silver halide can be simultaneously added and mixed to prepare an aqueous organic silver salt dispersion used in the present invention.

Further, the aqueous organic silver salt dispersion used in the present invention can be prepared by a so-called control triple jet method in which an alkali metal salt of an organic acid, silver nitrate and silver halide are simultaneously added and mixed, respectively. .

In the present invention, from the viewpoint of simplicity in the production process, the method for producing an aqueous organic silver salt dispersion using the above-described controlled double jet method is preferably used. From the viewpoint of producing a high-sensitivity photothermographic material, the method for producing an aqueous organic silver salt dispersion using the above-described control triple jet method is preferably used.

In the method for producing an organic silver salt dispersion of the present invention, the organic silver salt dispersion containing photosensitive silver halide particles is converted into a solid such as powder from the aqueous organic silver salt dispersion obtained above. The organic silver salt dispersion is taken out by oil layer separation or the like using a solvent, and then dispersed together with a binder and a solvent using a medium stirring type disperser filled with ceramic beads. Can be prepared.

As the solvent used in the present invention, water, alcohols, esters, aromatic hydrocarbons, ketones and the like are preferable.

The alcohols include methanol,
Ethanol, propanol and the like can be mentioned.

Examples of the esters include ethyl acetate, butyl acetate and the like.

The aromatic hydrocarbons include benzene, toluene, xylene and the like.

Examples of the ketones include acetone, methyl ethyl ketone and the like.

Among the above-mentioned solvents, acetone and methyl ethyl ketone are preferably used from the viewpoint of the dispersibility of the organic silver salt and the narrowness of the particle size distribution of the organic silver salt particles, and methyl ethyl ketone is particularly preferably used. is there.

The ratio of the organic silver salt used in the present invention to the solvent is such that the amount of the organic silver salt is 10 to the solvent.
50 wt% is preferable, and 20 to 40 wt% is more preferable.
%.

The binder used in the present invention includes:
Natural polymer synthetic resins and polymers and copolymers, other film-forming media such as: gelatin, gum arabic, poly (vinyl alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, Poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-
Butadiene), poly (vinyl acetal) s (for example,
Poly (vinyl formal) and poly (vinyl butyral)), poly (ester) s, poly (urethane) s, phenoxy resins, poly (vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate) ), Cellulose esters and poly (amides) are preferably used.

The binder used in the present invention may be hydrophilic or non-hydrophilic. Further, in order to protect the surface of the photosensitive material or to prevent scratches, it is possible to have a non-photosensitive layer outside the photosensitive layer, as a binder used in these non-photosensitive layers, the binder described above Can be used.

In the present invention, in order to increase the speed of thermal development, the amount of binder in the photosensitive layer is 1.5 to 10 g / m ^2.
It is preferred that More preferably, 1.7 to 8 g
/ M ² .

The photothermographic material of the present invention preferably contains a reducing agent. Examples of suitable reducing agents are described in U.S. Patent Nos. 3,770,448, 3,773,512,
No. 3,593,863 and Research D
No. 17029 and 29996, and include the following: Aminohydroxycycloalkenonone compounds (eg, 2-hydroxypiperidino-2-cyclohexenone); aminoreductones esters (eg, piperidinohexose reductone monoacetate) as precursors of reducing agents; N- Hydroxyurea derivatives (e.g., Np-methylphenyl-N-hydroxyurea); hydrazones of aldehydes or ketones (e.g., anthracenaldehyde phenylhydrazone); phosphoramidophenols; phosphoramidoanilines; polyhydroxybenzenes (Eg, hydroquinone, t-butyl-hydroquinone, isopropylhydroquinone, and (2,5-dihydroxy-phenyl) methylsulfone); sulfhydroxamic acids (eg, benzenesulfhydroxam) ); Sulfonamides anilines (e.g., 4-(N-
Methanesulfonamido) aniline); 2-tetrazolylthiohydroquinones (for example, 2-methyl-5- (1-
Phenyl-5-tetrazolylthio) hydroquinone); tetrahydroquinoxalines (e.g., 1,2,3,4-
Amidooxins; Azines (for example, a combination of an aliphatic carboxylic acid arylhydrazide and ascorbic acid); a combination of polyhydroxybenzene and hydroxylamine, reductone and / or hydrazine; Hydroxamic acids; Azines and sulfone Combinations of amidophenols; α-cyanophenylacetic acid derivatives; bis-β-naphthol and 1,3
5-pyrazolones; sulfonamidophenol reducing agents; 2-phenylindane-1,3-dione and the like; chromans;
Dihydropyridines (for example, 2,6-dimethoxy-
3,5-dicarbethoxy-1,4-dihydropyridine); bisphenols (for example, bis (2-hydroxy-3-t-butyl-5-methylphenyl) methane, bis (6-hydroxy-m-tri) mesitol (Mesi
tol), 2,2-bis (4-hydroxy-3-methylphenyl) propane, 4,5-ethylidene-bis (2-
t-butyl-6-methyl) phenol), ultraviolet-sensitive ascorbic acid derivatives and 3-pyrazolidones. Among them, particularly preferred reducing agents are hindered phenols.
Examples of the hindered phenols include compounds represented by the following general formula (A).

[0070]

Embedded image

In the formula, R is a hydrogen atom or a group having 1 carbon atom.
To 10 alkyl groups (for example, butyl group, 2,4,4-
R ′ and R ″ represent an alkyl group having 1 to 5 carbon atoms (eg, a methyl group, an ethyl group, a t-butyl group, etc.).

Specific examples of the compound represented by formula (A) are shown below. However, the present invention is not limited to these.

[0073]

Embedded image

[0074]

Embedded image

The amount of the reducing agent including the compound represented by formula (A) is preferably 1 × 1 per mol of silver.
It is from 0 ^-2 to 10 mol, especially from 1 x 10 ^{-2 to} 1.5 mol.

The photothermographic material of the present invention may contain an antifoggant. 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. 075 and 4,452,885 and JP-A-59
Preferred are antifoggants such as those disclosed in US Pat.

Particularly preferred non-mercury antifoggants are described in US Pat. Nos. 3,874,946 and 4,756,99.
No.9, -C (X ₁ )
(X ₂ ) (X ₃ ) (where X ₁ and X ₂ represent a halogen atom, and X ₃ represents a hydrogen atom or a halogen atom) and is a heterocyclic compound provided with one or more substituents. As examples of suitable antifoggants, compounds described in paragraphs [0030] to [0036] of JP-A-9-288328 are preferably used.

As another example of the preferred antifoggant, JP-A-9-90550, paragraph [006]
2] to [0063]. Still other suitable antifoggants are described in U.S. Pat.
8,523 and British Patent Application No. 9300147.7.
No. 9311790.1.

It is preferable to add a toning agent to the photothermographic material of the present invention for the purpose of improving the silver tone after development. Examples of suitable toning agents are Research Discl
No. 17029, which includes the following:

Imides (eg, phthalimide); cyclic imides, pyrazolin-5-ones, and quinazolinones (eg, succinimide, 3-phenyl-2-pyrazolin-5-one, 1-phenylurazole, quinazoline and , 4-thiazolidinedione); naphthalimides (eg, N-hydroxy-1,8-naphthalimide); cobalt complexes (eg, hexamine trifluoroacetate of cobalt); mercaptans (eg, 3
-Mercapto-1,2,4-triazole); N- (aminomethyl) aryldicarboximides (for example,
N- (dimethylaminomethyl) phthalimide); blocked pyrazoles, isothiuronium (isoth
uronium) derivatives and certain photobleaching combinations (eg, N, N'-hexamethylene (1-carbamoyl-3,5-dimethylpyrazole), 1,8-
A combination of (3,6-dioxaoctane) bis (isothiuronium trifluoroacetate) and 2- (tribromomethylsulfonyl) benzothiazole; a merocyanine dye (e.g., 3-ethyl-5-((3-ethyl -2-benzothiazolinylidene (benzothiazolinylidene))-1-methylethylidene) -2-thio-2,4
Oxazolidinedione); phthalazinone, a phthalazinone derivative or a metal salt of these derivatives (for example, 4-
(1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3
-Dihydro-1,4-phthalazinedione); a combination of phthalazinone and a sulfinic acid derivative (for example, 6-chlorophthalazinone + sodium benzenesulfinate or 8-methylphthalazinone + sodium p-trisulfonate); phthalazine + phthalate Combinations of acids; phthalazine (including adducts of phthalazine) and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivatives and anhydrides thereof (for example,
Combination with at least one compound selected from phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride; quinazolinediones, benzoxazine, naloxazine derivatives; benzoxazine-2,4-dione (Eg, 1,3-benzoxazine-2,4-dione); pyrimidines and asymmetric-triazines (eg, 2,4-dihydroxypyrimidine), and tetraazapentalene derivatives (eg,
3,6-dimercapto-1,4-diphenyl-1H, 4
H-2,3a, 5,6a-tetraazapentalene). Preferred toning agents are phthalazone or phthalazine.

The photothermographic materials of the present invention include, for example, JP-A-63-159814, JP-A-60-140335, JP-A-63-231437, JP-A-63-259651 and JP-A-6-259561.
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.

Useful sensitizing dyes for use in the present invention include, for example, Research Disclosure Item
17643 IV-A (p. 23, December 1978) and Item 1831X (p. 437, August 1978). In particular, a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various scanner light sources can be advantageously selected. For example, JP-A-9-34078, JP-A-9-54409, and JP-A-9-806
The compounds described in No. 79 are preferably used.

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

When a mercapto compound is used in the present invention, it may be of any structure,
Those represented by -SS-Ar are preferred. In the formula, M is a hydrogen atom or an alkali metal atom, and Ar represents an aromatic ring or a condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium or tellurium atoms.

As the aromatic ring, an aromatic carbocyclic ring and a heteroaromatic ring are used. In the present invention, a heteroaromatic ring is preferably used. As the heteroaromatic ring, for example, benzimidazole, naphthymidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzotellurazole, imidazole, oxazole, pyrazole, triazole, thiadiazole, tetrazole, triazine, pyrimidine, Pyridazine, pyrazine, pyridine, purine, quinoline or quinazolinone. The heteroaromatic ring includes, for example, a halogen atom (eg, Br and Cl), a hydroxy group, an amino group, a carboxy group, an alkyl group (eg, one or more carbon atoms, preferably
Having a substituent selected from the group consisting of those having from 1 to 4 carbon atoms) and alkoxy groups (e.g., having at least one carbon atom, preferably having from 1 to 4 carbon atoms). Is also good. Examples of the mercapto-substituted heteroaromatic compound include 2-mercaptobenzimidazole and 2-mercaptobenzimidazole.
Mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-mercapto-5-methylbenzothiazole, 3-mercapto-1,2,4-triazole,
-Mercaptoquinoline, 8-mercaptopurine, 2,
3,5,6-tetrachloro-4-pyridinethiol,
-Hydroxy-2-mercaptopyrimidine, 2-mercapto-4-phenyloxazole and the like,
The present invention is not limited to these.

In the present invention, a matting agent is preferably contained on the photosensitive layer side, and it is preferable to provide a matting agent on the surface of the photosensitive material in order to prevent the image after thermal development from being damaged. It is preferable that the content of the agent is 0.5 to 30% by weight based on all binders on the emulsion layer side.
The material of the matting agent used in the present invention may be either an organic substance or an inorganic substance.

For example, as the inorganic substance, Swiss Patent No. 3
Silica described in No. 30,158, French Patent No. 1,29
No. 6,995, etc., British Patent No. 1,17
Alkaline earth metals or carbonates such as cadmium and zinc described in 3,181 and the like can be used as a matting agent. As organic substances, US Pat. No. 2,322,03
7, starch derivatives described in Belgian Patent No. 625,451 and British Patent No. 981,198, polyvinyl alcohol described in Japanese Patent Publication No. 44-3643, and Swiss Patent No. 330,158. Polystyrene or polymethacrylate described in U.S. Pat.
Organic matting agents such as polyacrylonitrile described in No. 79,257 and polycarbonate described in No. 3,022,169 can be used.

The shape of the matting agent may be either regular or irregular, but is 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. In the present invention, the particle diameter of the matting agent indicates the diameter converted into a sphere.

The matting agent used in the present invention preferably has an average particle size of 0.5 μm to 10 μm, more preferably 1.0 μm to 8.0 μm. The matting agent has a coefficient of variation of the particle size distribution of 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 used in the present invention can be contained in any constituent layer, but in order to achieve the object of the present invention, It is preferably a constituent layer other than the photosensitive layer, and more preferably the outermost layer as viewed from the support.

The method of adding the matting agent used in the present invention may be a method in which the matting agent is dispersed in a coating solution in advance, or may be sprayed after the coating solution is applied and before the drying is completed. May be used. When a plurality of types of matting agents are added, both methods may be used in combination.

In the present invention, a conductive compound such as a metal oxide and / or a conductive polymer can be contained in the constituent layer in order to improve the chargeability. These may be contained in any layer, but are preferably contained in an undercoat layer, a backing layer, a layer between the photosensitive layer and the undercoat, and the like.

In the present invention, US Pat.
The conductive compounds described in No. 773 columns 14 to 20 are preferably used.

Various additives may be added to any of the photosensitive layer, the non-photosensitive layer, and other constituent layers. In the photothermographic material of the present invention, for example, a surfactant, an antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber, a coating aid, and the like may be used in addition to the above. These additives and the other additives mentioned above are used in Research Disclosure.
re Item 17029 (June 1978, p. 9-
The compound described in 15) can be preferably used.

Binders suitable for the photothermographic material of the present invention are transparent or translucent, generally colorless, and include natural polymer synthetic resins, polymers and copolymers, and other film-forming media such as gelatin, gum arabic,
Poly (vinyl alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid) ), Copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (ester) ), Poly (urethane), phenoxy resin, poly (vinylidene chloride), poly (epoxide),
Poly (carbonate) s, poly (vinyl acetate),
There are cellulose esters and poly (amides). It may be hydrophilic or non-hydrophilic. In order to protect the surface of the light-sensitive material and prevent abrasion, a non-light-sensitive layer may be provided outside the light-sensitive layer. The binder used for these non-photosensitive layers may be the same as or different from the binder used for the photosensitive layers.

In the present invention, in order to increase the speed of thermal development, the amount of the binder in the photosensitive layer is 1.5 to 10 g / m ^2.
It is preferred that More preferably, 1.7 to 8 g
/ M ² .

The support used in the present invention may be formed of a plastic film (for example, polyethylene terephthalate, polycarbonate, or the like) in order to prevent deformation of an image after development processing.
Polyimide, nylon, cellulose triacetate, polyethylene naphthalate) are preferred.

Among them, a preferred support is a support of polyethylene terephthalate (hereinafter abbreviated as PET) and a plastic (hereinafter abbreviated as SPS) containing a styrene polymer having a syndiotactic structure. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

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 forming these supports and before the photosensitive layer is applied, at a temperature higher than the glass transition point of the support by 30 ° C. or more,
Preferably at a temperature higher than 35 ° C., more preferably 40 ° C.
It is preferable to heat at a temperature higher than ℃. 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 a polyester in which all of the polyester components are made of polyethylene terephthalate. 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.

SPS, unlike ordinary polystyrene (atactic polystyrene), is polystyrene having steric regularity. The regular stereoregular structure part of SPS is called a racemo chain, and it is preferable that there are more regular parts such as two, three, five or more. In the present invention, the racemo chain is 2 It is preferably 85% or more in the chain, 75% or more in the three chains, 50% or more in the five chains, and 30% or more in the further chains. The polymerization of SPS can be carried out according to the method described in JP-A-3-131843.

As the method of forming a support and the method of producing an undercoat used in the present invention, known methods can be used, and preferably, paragraph [0030] of JP-A-9-50094 is used.
To [0070].

The photothermographic material of the present invention, which forms a photographic image by heat development, comprises a reducible silver source (organic silver salt), a photosensitive silver halide, a reducing agent and, if necessary, silver. It is preferable that the photothermographic material contains a color toning agent which suppresses the color tone of the present invention in a state of being usually dispersed in an (organic) binder matrix. The photothermographic material of the present invention is stable at room temperature, but is exposed to a high temperature (for example, 80 ° C. to 14 ° C.).
(0 ° C.). Heating generates silver through an oxidation-reduction reaction between an organic silver salt (functioning as an oxidizing agent) 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, resulting in the formation of 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 a photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer. To control the amount or wavelength distribution of light passing through the photosensitive layer, a filter dye layer on the same side as the photosensitive layer and / or an antihalation dye layer, a so-called backing layer, may be formed on the opposite side. A dye or pigment may be included in the active layer. As the dye to be used, any compound may be used as long as it has a desired absorption in a desired wavelength range, and examples thereof include JP-A-59-6481 and JP-A-59-1.
No. 82436, U.S. Pat. Nos. 4,271,263 and 4,594,312, European Patent Publication 533,008.
No. 652,473, JP-A-2-216140,
4-348339, 7-191432, 7-
Compounds described in No. 301890 are preferably used.

These non-photosensitive layers preferably contain the binder or matting agent described above, and may further contain a sliding agent such as a polysiloxane compound, wax or liquid paraffin.

The light-sensitive layer may be composed of a plurality of layers, and the sensitivity may be changed to a high-sensitivity layer / low-sensitivity layer or a low-sensitivity layer / high-sensitivity layer for adjusting the gradation.

The details of the photothermographic material are described in, for example, US Pat. Nos. 3,152,904 and 3,457,
No. 075, and D.A. “Dry Silver Photographic Materials (Dry Silver P) by Morgan
photographic Material) ”and D.C.
Morgan and B.A. Shelley
y) "Heat treated silver system (The
rmally Processed SilverSy
stems) "(Imaging Processes and Materials)
s and Materials) Neblette
Eighth Edition, Sturge, V.S. Walworth, A .; Shepp
Editing, 2nd page, 1969). Among them, the present invention is characterized in that an image is formed by thermally developing a photosensitive material at 80 to 140 ° C., and no fixing is performed. Therefore, the silver halide and the organic silver salt remaining in the unexposed area remain in the photosensitive material without being removed.

In the present invention, after the heat development processing,
The optical transmission density of the light-sensitive material containing the support at 400 nm is preferably 0.2 or less. A more preferable value of the optical transmission density is 0.02 or more and 0.2 or less.

[0111]

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 << Preparation of Silver Halide Emulsion A >> 7.5 g of ossein gelatin and 10 mg of potassium bromide were dissolved in 900 ml of water, the temperature was adjusted to 35 ° C. and the pH was adjusted to 3.0.
g of an aqueous solution containing 370 ml of an aqueous solution containing potassium bromide and potassium iodide (equivalent to the above silver nitrate) in a molar ratio of (98/2) and K ₂ [Ir (NO) Cl ₅ ] per mol of silver. 1 × 10 ^-4 mol was added over 10 minutes by the controlled double jet method while maintaining the pAg at 7.7. Thereafter, 4-hydroxy-6-methyl-1,
Add 3,3a, 7-tetrazaindene and add NaOH to p.
By adjusting H to 5, cubic silver iodobromide grains having an average grain size of 0.06 μm, a grain size variation coefficient of 11%, and a [100] face ratio of 87% were obtained. This emulsion was subjected to coagulation sedimentation using a gelatin coagulant and desalting treatment, and then 0.1 g of phenoxyethanol was added to adjust the pH to 5.9 and the pAg to 7.5. Further, it was optimally subjected to chemical sensitization with sodium thiosulfate and chloroauric acid to obtain a silver halide emulsion A.

<< Preparation of Sodium Salt Solution of Fatty Acid >>
8. 32.4 g of behenic acid and arachidic acid in 5 ml of pure water.
9 g and stearic acid 5.6 g were dissolved at 90 ° C. Next, 98 ml of a 1.5 M aqueous sodium hydroxide solution was added while stirring at a high speed. Next, after adding 0.93 ml of concentrated nitric acid, the mixture was cooled to 55 ° C. and stirred for 30 minutes to obtain a sodium salt solution of a fatty acid.

<< Preparation and Drying of Aqueous Mixture 1 of Fatty Acid Silver >> 15.1 g of the above silver halide emulsion A was added to the above fatty acid sodium salt solution, and pH was adjusted with sodium hydroxide solution.
After adjusting to 8.1, 147 ml of a 1M silver nitrate solution was added over 7 minutes, and the mixture was further stirred for 20 minutes, and water-soluble salts were removed by ultrafiltration while adding pure water. The resulting fatty acid silver particles had an average major axis particle size of 0.8 μm and a coefficient of variation of 10%. This was filtered under reduced pressure and sufficiently dried with a vacuum dryer at 45 ° C. to obtain a powder of an aqueous mixture 1.

<< Photosensitive Emulsion No. Preparation of 1 to 9 >> 120 g of polyvinyl butyral (average molecular weight: 3000) was dissolved in 700 g of methyl ethyl ketone and 80 g of toluene, and then 100 g of an aqueous mixture 1 of fatty acid silver was added, and a liquid stirred with a disper was prepared.

Next, this liquid was added to a horizontal bead mill (0.5 liter, bead filling rate 80%, rotor peripheral speed 13 m / sec).
c: Dispermat SL-C50, Getzma
nn under the respective conditions shown in Table 1.
After circulating and dispersing for 0 minute, 1 to 8 photosensitive emulsions were obtained.

Also, 1 liter of 5 mm and 2 mm zirconia balls were placed in a 2 liter alumina ball mill, 500 g of the liquid stirred with the above disperser was sealed, and the mixture was dispersed for 12 hours. Thus, photosensitive emulsion No. 9 was obtained.

[0118]

[Table 1]

In Table 1, ZrO ₂ alone represents yttrium-stabilized zirconia.

In Table 1, ZrO ₂ / Al ₂ O ₃ represents zirconia reinforced alumina.

<< Preparation of PET-Subbed Photographic Support >> A corona discharge treatment of 8 W / m ² · min. Was performed on both sides of a commercially available biaxially stretched heat-fixed PET film having a thickness of 100 μm.
On one surface, the following undercoating coating solution a-1 was dried to a thickness of 0.8 μm.
And then dried to form a subbing layer A-1. On the other side, the following antistatic coating subbing coating solution b-1 is applied to a dry film thickness of 0.8 μm and dried. In this way, an antistatic subbing layer B-1 was obtained.

<< Undercoat Coating Solution a-1 >> Butyl acrylate (30% by weight) t-butyl acrylate (20% by weight) Styrene (25% by weight) Copolymer latex liquid of 2-hydroxyethyl acrylate (25% by weight) (Solid content 30%) 270 g (C-1) 0.6 g hexamethylene-1,6-bis (ethylene urea) 0.8 g Finish to 1 liter with water << Subtraction coating solution b-1 >> Butyl acrylate (40 weight %) Styrene (20% by weight) Glycidyl acrylate (40% by weight) copolymer latex liquid (solid content 30%) 270 g (C-1) 0.6 g Hexamethylene-1,6-bis (ethylene urea) 8g Finished to 1 liter with water Then, on the upper surface of the undercoat layer A-1 and the undercoat layer B-1,
A corona discharge of 8 W / m ² · min. Was performed, and the following lower coating liquid a-2 was coated on the lower coating layer A-1 with a dry film thickness of 0.1 μm.
The lower coating layer B-2 is coated with the following coating liquid b-2 on the lower coating layer B-1 so as to have a dry film thickness of 0.8 μm. Coated as B-2.

<< Underdrawing upper layer coating solution a-2 >> Gelatin 0.4 g / m ² Weight (C-1) 0.2 g (C-2) 0.2 g (C-3) 0.1 g Silica particles ( (Average particle size: 3 μm) 0.1 g Finished to 1 liter with water << Lower coating solution for upper layer b-2 >> (C-4) 60 g Latex liquid containing (C-5) as a component (solid content: 20%) 80 g Ammonium sulfate 0 0.5 g (C-6) 12 g Polyethylene glycol (weight average molecular weight 600) 6 g Finish to 1 liter with water

[0124]

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[0125]

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<< Heat Treatment of Support >> In the above-mentioned undercoat drying step of the undercoated support, the support was heated at 140 ° C.
Thereafter, it was gradually cooled.

<< Preparation of Photosensitive Material >> Samples 1 to 9 were prepared by sequentially forming the following layers on the support. The drying was performed at 60 ° C. for 15 minutes.

Back side coating: A solution having the following composition was applied onto the undercoating upper layer B-2.

Cellulose acetate (10% methyl ethyl ketone solution) 15 ml / m ² dye-B 7 mg / m ² dye-C 7 mg / m ² Matting agent: monodispersity 15% Average particle size 10 μm monodisperse silica 30 mg / m ² C _{9 H 19 -C 6 H 4 -SO 3} Na 10mg / m 2

[0130]

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Photosensitive layer surface side coating Photosensitive layer 1: A solution having the following composition was coated and the silver amount was 2.1 g / m ^2.
Was applied on the undercoating upper layer A-2 so that

Photosensitive emulsion shown in Table 1 240 g Sensitizing dye-1 (0.1% methanol solution) 1.7 ml Pyridinium bromide perbromide (6% methanol solution) 3 ml Calcium bromide (0.1% methanol solution) 1.7 ml Antifoggant-2 (10% methanol solution) 1.2 ml 2- (4-chlorobenzoyl) benzoic acid (12% methanol solution) 9.2 ml 2-mercaptobenzimidazole (1% methanol solution) 11 ml tribromo Methylsulfoquinoline (5% methanol solution) 17 ml Reducing agent A-4 (20% methanol solution) 29.5 ml High contrast agent H (1% methanol solution) 3 ml

[0133]

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[0134]

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Surface protective layer: A solution having the following composition was applied on the photosensitive layer.

Acetone 35 ml / m ² Methyl ethyl ketone 17 ml / m ² Cellulose acetate 2.3 g / m ² Methanol 7 ml / m ² Phthalazine 250 mg / m ² 4-Methylphthalic acid 180 mg / m ² Tetrachlorophthalic acid 150 mg / m ² Tetrachlorophthale Acid anhydride 170 mg / m ² Matting agent: monodispersity 10% Average particle size 4 μm monodisperse silica 70 mg / m ² C ₉ H ₁₉ -C ₆ H ₄ -SO ₃ Na 10 mg / m ² << dispersibility of photosensitive emulsion Evaluation> The photosensitive emulsion obtained by dispersion was applied to a slide glass, and the magnification of an optical microscope was 100.
The size and number of the aggregates were compared at five times in five steps. A sample having small and small aggregates was designated as 1, and a sample having large aggregates and a large number was designated as 5.

<< Evaluation of Process Suitability >> The process suitability in the production of the dispersion was relatively evaluated, such as abrasion and breakage of the medium used during dispersion, abrasion of the rotor of the disperser, and the time required for dispersing the organic silver salt. , Good ones and bad ones.

<< Evaluation of Fogging Performance >> After exposing the photosensitive material with a laser sensitometer equipped with an 820 nm diode, the photographic material was processed (developed) at 120 ° C. for 15 seconds, and the fog density was measured. The fog density referred to here is the density of a portion where a halftone dot is exposed to 0%. The smaller the fog density, the more practically preferable.

<< Evaluation of Density of Photothermographic Material >> The developed photothermographic material was measured with a PDA-65 (Konica Digital Densitometer). The obtained evaluation results are shown in Table 2 below.

[0140]

[Table 2]

From Table 2, it can be seen that in Comparative Samples 1 and 2, abrasion and breakage of the beads used during dispersion, abrasion of the rotor of the dispersing machine, etc. occurred, and the process suitability was poor. The photothermographic material produced is highly fogged due to significant contamination due to abrasion, breakage, and rotor abrasion, and the dispersibility of the organic silver salt is poor, so that the density of the developed image is reduced.

In Comparative Sample 9, since a ball mill, which is a tumbling medium disperser, was used for dispersion, even when dispersion was performed for as long as 12 hours, an organic silver salt dispersion having good dispersibility was obtained. It cannot be obtained, the process suitability is clearly poor, and the density of the produced photothermographic material after the development is significantly reduced.

The sample 3 of the present invention was compared with the comparative sample.
To 8 can reduce the amount of impurities mixed during dispersion and can produce an organic silver salt dispersion having good dispersibility.
It is apparent that the use of a photothermographic material produced using the same results in a small decrease in density after development.

[0144]

According to the present invention, a high-dispersion, low-fogging photosensitive emulsion can be prepared, impurities can be reduced by friction of a device and a medium at the time of dispersion, and thermal development with good process suitability can be achieved. A method for producing a light-sensitive material and a heat-developable light-sensitive material with a small decrease in density after heat development could be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a dispersion section of a medium stirring type dispersion machine (bead mill) used in the production method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inlet 2 Rotor (rotating part) 3 Ceramic beads 4 Stator (fixed part) 5 Outlet

Claims (9)

[Claims] 1. A method for producing an organic silver salt dispersion comprising dispersing a raw material liquid comprising at least an organic silver salt, photosensitive silver halide particles, a solvent and a binder using a medium stirring type dispersion machine. A method for producing an organic silver salt dispersion, characterized in that a non-metal is used for filling or dispersing ceramic beads in a disperser and for part or all of the medium stirring type disperser in contact with the ceramic beads. 2. The method for producing an organic silver salt dispersion according to claim 1, wherein the ceramic beads are yttrium-stabilized zirconia beads. 3. The method for producing an organic silver salt dispersion according to claim 1, wherein the ceramic beads are zirconia reinforced alumina beads. 4. The method for producing an organic silver salt dispersion according to claim 1, wherein the non-metal is a ceramic. 5. The method for producing an organic silver salt dispersion according to claim 1, wherein the non-metal is a resin. 6. The method for producing an organic silver salt dispersion according to claim 4, wherein the ceramic is yttrium-stabilized zirconia. 7. The method for producing an organic silver salt dispersion according to claim 4, wherein the ceramic is zirconia reinforced alumina. 8. The method for producing an organic silver salt dispersion according to claim 5, wherein the resin is ultra-high molecular weight polyethylene. 9. A photothermographic material containing the organic silver salt dispersion produced by the production method according to claim 1, 2, 3, 4, 5, 6, 7, or 8.