JP2000072777A - Image formation using heat developable photosensitive material, production of organic silver salt dispersion and heat developable photosensitive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat developable photosensitive material improved in photographic performances such as sensitivity, halation and image storing property and provide an image-forming method and obtain an organic silver salt dispersion. SOLUTION: In this image-forming method using a heat developable photosensitive material having a recording layer containing an organic silver salt, a photosensitive silver halide and a reducing agent, heat developing temperature is boiling point or above of an organic solvent used in producing process of the organic silver salt. This method for producing the organic silver dispersion comprises adding silver nitrate to aqueous dispersion in which alkali metal salt fine particles of an organic silver salt is dispersed to prepare aqueous dispersion of organic silver salt and adding an organic solvent having a boiling point of heat developing temperature or below to aqueous dispersion of the organic silver salt to carry out layer conversion of the organic silver salt from water layer to a solvent layer and separating the organic solvent layer from the water layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser imager, an image forming method using a photothermographic material for a laser image setter, a method for producing an organic silver salt dispersion for producing the photothermographic material, and thermal development. It relates to a photosensitive material.

[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, in the field of printing plate making, a method has been adopted in which an output image of a plate making original plate of a laser image setter is exposed to a photosensitive material by scanning a laser beam with a laser beam 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 have been provided for demand.

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 is a need for a technique relating to a photothermographic material capable of performing efficient exposure with a laser imager or a laser image setter and forming a high-resolution and clear black image.

As this technique, for example, US Pat.
Nos. 152,904, 3,487,075 and D.I. "Dry Silver Photographic" by Morgan
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 above-mentioned image forming material is an organic silver salt, and many methods for producing the same have been disclosed. As one of them, a method of forming an organic silver salt in an aqueous system, desalting, drying and redispersing in an organic solvent system is disclosed in U.S. Pat. No. 5,434,043.
No. 368 describes that a flushing method (an operation of transferring solid fine particles suspended in water to an organic solvent layer) without a drying step is used. However, the photothermographic material using an organic silver salt prepared by any of the above methods has a disadvantage that the image storability is particularly poor over time, and a solution has been desired.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming method having improved photographic properties such as sensitivity, fog and image storability, a photothermographic material and a method for producing an organic silver salt dispersion used therein. It is to provide.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventor has found that by satisfying the condition that the heat development temperature is higher than the boiling point of the organic solvent used in the production of the organic silver salt, it remains in the photosensitive material during development. It has been found that the unnecessary solvent is removed and the image storability is improved, and the above object of the present invention has been achieved by the following constitution.

1. In an image forming method using a photothermographic material having a recording layer containing an organic silver salt, a photosensitive silver halide, and a reducing agent on a support, the heat development temperature was used in the production process of the organic silver salt. An image forming method using a photothermographic material characterized by having a boiling point of an organic solvent or higher.

[0010] 2. The organic silver salt is an organic silver salt produced by performing a layer transition from an aqueous layer to an organic solvent layer by adding an organic solvent having a boiling point not higher than the thermal development temperature and then separating the organic solvent layer and the aqueous layer. 2. An image forming method using the photothermographic material according to item 1.

3. 3. The image forming method using the photothermographic material according to 1 or 2, wherein the solubility of the organic solvent in water at 20 ° C. is 5 wt% or less.

4. An aqueous dispersion of an organic silver salt is prepared by adding silver nitrate to an aqueous dispersion in which fine particles of an alkali metal salt of an organic acid are dispersed, and an organic solvent having a boiling point equal to or lower than the thermal development temperature is prepared in the aqueous dispersion of the organic silver salt. And converting the organic silver salt from an aqueous layer to an organic solvent layer, and then separating the organic solvent layer and the aqueous layer, thereby producing an organic silver salt dispersion.

5. 5. The method for producing an organic silver salt dispersion according to 4, wherein the solubility of the organic solvent in water at 20 ° C. is 5 wt% or less.

6. In a photothermographic material having a recording layer containing an organic silver salt, a photosensitive silver halide and a reducing agent on a support, the organic silver salt may be added by adding an organic solvent having a boiling point not higher than the heat development temperature. A photothermographic material obtained by subjecting the aqueous dispersion of the above to a layer conversion process from an aqueous layer to an organic solvent layer.

Hereinafter, the present invention will be described in detail.

The photothermographic material of the present invention, which forms a photographic image by heat development processing, comprises a reducible silver source (organic silver salt), a photosensitive silver halide, a reducing agent and, if necessary, silver. This is a photothermographic material containing a color tone agent or the like which suppresses the color tone of an organic binder matrix in a dispersed state.

The photothermographic material of the present invention is stable at room temperature, but after exposure, is heated to a high temperature (for example, 80 to 140 ° C.) and thermally developed. That is, when heated, the organic silver salt functions as an oxidizing agent and generates silver through an oxidation-reduction reaction with the 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 forms a black image, which forms the image in contrast to the unexposed areas. 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 provided on the support, it is preferable to form 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 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. Dyes or pigments may be included in the 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-59-18.
2436, U.S. Pat. Nos. 4,271,263, 4,594,312, EP 533008,
No. 652473, JP-A-2-216140, 4-
348339, 7-191432, 7-301
Compounds described in No. 890 and the like are preferably used.

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

The photosensitive layer may be composed of a plurality of layers, or may be composed of a high-sensitivity layer, a low-sensitivity layer or a low-sensitivity layer, and a high-sensitivity layer for adjusting the gradation.

Details of the photothermographic material are described in, for example, US Pat. Nos. 3,152,904 and 3,457,075 and D.C. Morgan Dry Silver Photo
Ophthalmic Materials and D.O. Morga
n, B. Shelly Thermally Process
ssed Silversystems, Imaging
Processes and Materials,
Sturge, V .; Walorth, A .; (Edited by Shepp, Neblette, 8th edition, 2nd page, 1969).

In the present invention, the light-sensitive material is 80 to 14
An image is formed by heat development at 0 ° C., and no fixing is performed. Therefore, the silver halide and the organic silver salt remaining in the unexposed areas remain in the photosensitive material without being removed.

Therefore, the transmission optical density of the photosensitive material including the support at 400 nm light after the heat development processing is preferably 0.2 or less, more preferably 0.02 to 0.2. When the transmission optical density exceeds 0.2, the devitrification property is remarkably lost, and when the transmission optical density is less than 0.02, the sensitivity is low and it may not be practically used.

The organic silver salt of the present invention is a reducible silver source. Silver salts of organic acids and heteroorganic acids containing a reducible silver ion source, especially long chains (10 to 30, preferably 15 to 15).
Silver salts of aliphatic carboxylic acids having up to 28 carbon atoms) are preferred.

Organic or inorganic silver complexes whose ligands have a complex stability constant for silver ions of 4.0 to 10.0 are also useful. Examples of the organic acids of the present invention include: Organic acids (eg, gallic acid, oxalic acid, behenic acid,
Silver salts of stearic acid, palmitic acid, lauric acid, oleic acid, caproic acid, myristic acid, palmitic acid, maleic acid, linoleic acid, etc., carboxyalkylthioureas (eg, 1- (3-carboxypropyl) thiourea, Silver salt of-(3-carboxypropyl) -3,3-dimethylthiourea or the like, or a polymer reaction product of an aldehyde with a hydroxy-substituted aromatic carboxylic acid (for example, silver of aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) Complexes, silver salts or silver complexes of hydroxy-substituted acids (eg, salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid, etc.), thioenes (eg, 3- (2-carboxyethyl) -4-Hydroxymethyl-4- (thiazoline-2-
Thioene, 3-carboxymethyl-4-thiazoline-2-thioene and the like), a silver salt or a complex thereof, imidazole,
Pyrazole, urazole, 1,2,4-thiazole or 1H-tetrazole, 3-amino-5-benzylthio-
A complex or salt of silver and a nitrogen acid selected from 1,2,4-triazole or benzotriazole; saccharin,
Silver salts such as 5-chlorosalicylaldoxime or silver salts of mercaptides. An example of a suitable silver salt is RD No. 17029
And 29963, a particularly preferred silver salt 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 includes 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. For example, after preparing an organic acid alkali metal salt soap (eg, sodium behenate, sodium alginate, etc.) by adding an alkali metal (eg, sodium hydroxide, potassium hydroxide, etc.) to an organic acid, a controlled double jet method is used. Thus, the soap, silver nitrate and the like are added to produce organic acid salt crystals. At that time, silver halide grains may be mixed.

In the present invention, the average particle size of the organic silver salt is preferably 1 μm or less, and is preferably monodispersed.

The average particle size of the organic silver salt refers to the diameter of a sphere equivalent to the volume of the particles of the organic silver salt when the particles of the organic silver salt are, for example, rod-shaped or plate-shaped particles. Say.
The average particle size is preferably from 0.01 to 0.8 μm, particularly preferably from 0.05 to 0.5 μm.

The term "monodispersion" is synonymous with the monodispersion in the case of the silver halide grains, preferably from 1 to 30. In the present invention, the organic silver salt is more preferably monodisperse particles having an average particle size of 1 μm or less. By setting the average particle size in this range, an image having a high density can be obtained.

In order to improve the monodispersity of the organic silver salt, it is preferred that the preparation of the organic silver salt does not go through a drying step. That is, the organic silver salt re-aggregates in the drying step, and the monodispersity deteriorates. Therefore, a flushing method without a drying step of the organic silver salt is more preferable in improving the monodispersibility of the organic silver salt.

Further, the organic silver salt preferably has tabular grains containing at least 60% of the total organic silver salt.

In the present invention, the preferably used tabular grains are those having an aspect ratio (abbreviated as AR) of 3 or more, which is a ratio between an average particle diameter and an average thickness, which is represented by the following formula.

AR = Average particle size (μm) / Average thickness (μm) In order to prevent the devitrification of the photosensitive material, the total amount of silver halide and organic silver salt is converted to silver amount to be 0.1 to 1 / m ² . 5-
It is preferably 2.2 g. With this range, a high-contrast image can be obtained. The amount of silver halide relative to the total amount of silver is at most 50% by weight, particularly preferably at most 25%.
%, More preferably in the range of 0.1 to 15%. The silver halide may be added to the organic silver salt dispersion by any method, but it is preferable that the silver halide is arranged close to the organic silver salt.

The shape of the organic silver salt fine particles is not particularly limited, but needle-like crystals having a short axis and a long axis are preferred. As is well known in the photosensitive silver halide light-sensitive material, the inversely proportional relationship existing 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 size of the organic silver salt particles as the image forming portion of the photothermographic material is large, it means that the covering power is small and the image density is low. Therefore, it is necessary to reduce the size of the organic silver salt particles.

The short axis of the organic silver salt particles of the present invention is from 0.01 to
0.20 μm, the major axis is preferably 0.10 to 5.0 μm, the minor axis is 0.01 to 0.15 μm, and the major axis is 0.10 to 4.0 μm.
0 μm is more preferred.

The particle size distribution of the organic silver salt is preferably monodispersed. The monodispersion rate is expressed as a percentage of the value obtained by dividing the standard deviation of the length of each of the minor axis and major axis by the average of the minor axis and major axis. Preferred monodispersion rate is 100% or less,
It is more preferably at most 80%, further preferably at most 50%.

As a method for measuring the shape of the organic silver salt particles,
It can be determined from a transmission electron microscope image of the organic silver salt dispersion. Another method for measuring monodispersity is to determine the standard deviation of the volume-weighted average diameter of the organic silver salt particles. In this case, the percentage (coefficient of variation) of the value divided by the volume-weighted average diameter is preferably It is 100% or less, more preferably 80% or less, and further preferably 50% or less.

As a measuring method, for example, a particle size (volume load) obtained by irradiating a laser beam to organic silver salt particles dispersed in a solution and obtaining an autocorrelation coefficient with respect to a time change of the fluctuation of the scattered light is obtained. Average diameter).

In the photothermographic material of the present invention, the coating amount of the organic silver salt, especially the organic acid silver, is 1 m ^{2 of the} photothermographic material.
0.5 to 5.0 g is preferable, and 1.0 to 5.0 g is preferable.
3.0 g is preferred.

If the coating amount of the organic acid silver is less than 0.5 / m ² , the sensitivity is insufficient, and if it exceeds 5.0 g / m ² , devitrification is lost and a high contrast image cannot be obtained.

As the alkali used for the alkali metal salt fine particles of the present invention, potassium hydroxide and sodium hydroxide are preferable.

The preparation of the organic silver salt dispersion according to the present invention comprises the steps of forming an organic silver salt in an aqueous system, desalting, drying and redispersing with an organic solvent having a boiling point below the development temperature. In the preparation, there is a flushing method which does not go through a drying step.

The organic solvent used in the flushing method is
The solubility in water at 20 ° C. is preferably 5% by weight or less.

As a method for producing an organic silver salt dispersion when the flushing method is used, an aqueous dispersion of an organic silver salt is prepared by adding silver nitrate to an aqueous dispersion in which fine particles of an organic acid alkali salt are dispersed. I do. Thereafter, an organic solvent having a boiling point not higher than the developing temperature is slowly added while stirring the aqueous dispersion, and then the stirring is stopped and the mixture is allowed to stand, and the organic silver salt contained in the aqueous dispersion is removed from the aqueous layer by the organic solvent. And the aqueous layer is separated to give an organic silver salt dispersion.

The organic solvent used for preparing the organic silver salt dispersion of the present invention includes methanol, ethanol, acetone, chloroform, toluene, cyclohexane and acetic acid.
-Butyl, n-butyl acetate, methyl isobutyl ketone, etc., and the solubility in water at 20 ° C. is 5 wt.
%, Toluene, cyclohexane, s-butyl acetate, n-butyl acetate, methyl isobutyl ketone and the like are preferred, and particularly preferred are s-butyl acetate, n-butyl acetate and methyl isobutyl ketone.

The solubility of the present invention in water at 20 ° C. is 5
The following can be cited as examples of the organic solvent having a content of not more than wt%.

S-butyl acetate Boiling point 112.3 ° C Solubility in water 0.6 wt% n-butyl acetate Boiling point 126.1 ° C Solubility in water 1.0 wt% Cyclohexane Boiling point 80.0 ° C Solubility in water Insoluble toluene Boiling point 112.3 ° C Solubility in water Unnecessary Methyl isobutyl ketone Boiling point 116.2 ° C Solubility in water Poorly soluble The recording layer of the photothermographic material of the invention contains silver halide grains that function as an optical sensor. The silver halide grains preferably have a small average grain size, more preferably 0.1 μm or less, more preferably 0.01 to 0.1 mm, in order to suppress white turbidity after image formation and obtain good image quality. 1 μm, particularly preferably 0.02 to 0.08 μm. The term "grain size" as used herein refers to the length of a ridge of a silver halide grain when the silver halide grain is a cubic or octahedral so-called normal crystal. In the case of non-normal crystals, for example, in the case of spherical, rod-shaped or tabular grains, the diameter refers to the diameter of a sphere equivalent to the volume of silver halide grains.

The silver halide grains are preferably monodispersed. Here, the monodispersion means that the degree of monodispersion determined by the following equation is 40 or less. The particle size is more preferably 30 or less, and particularly preferably 20% or less.

Monodispersity = (standard deviation of particle size) / (average value of particle size) × 100 The shape of the silver halide grains is not particularly limited, but the ratio occupied by the Miller index [100] plane is high. It is preferable that this ratio is 50% or more, further 70% or more,
In particular, it is preferably at least 80%. Miller index [1
The ratio of the [00] plane is determined by utilizing the dependence of the adsorption of the sensitizing dye on the [111] plane and the [100] plane. Tan
i. Imaging Sci. , 29, 165 (1
985).

Another preferred form of silver halide is tabular grains. Here, the tabular grains refer to
The thickness h in the vertical direction, where the square root of the projected area is the particle size r μm.
The aspect ratio = r / h in the case of μm is 3 or more. Among them, the aspect ratio is preferably 3 or more and 5 or more.
0 or less. The particle size is preferably 0.1 μm or less, and more preferably 0.01 to 0.08 μm.
These are disclosed in U.S. Patent Nos. 5,264,337 and 5,31.
No. 4,798, 5,320,958, and the like, the desired tabular grains can be easily obtained.

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. The photographic emulsion used in the present invention is P.I. Glafkids Chimie et
Physique Photographique (P
aul Montel, 1967); F. D
uffin Photographic Emulsi
on Chemistry (The Focal Pr
ess, 1966); L. Zelikman
et. , Al. , Making and Coati
ng Photographic Emulsion
(The Focal Press, 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 one of a one-sided mixing method, a double-sided mixing method, a combination thereof and the like. Good.

The silver halide may be added to the organic silver salt dispersion by any method, wherein the silver halide is arranged close to the reducible silver source. Further, the silver halide may be prepared by converting a part or all of silver in the organic acid silver by a reaction between the organic acid silver and a halogen ion into silver halide, or preparing the 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.

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 used in the present invention preferably contains metal ions or complex ions belonging to Groups 6 to (10) of the periodic table. These metals include W, Fe, Co, Ni, Ru, Rh, Pd, R
e, Os, Ir and Pt are preferred.

These metals can be introduced into the silver halide in the form of a complex.

In the present invention, the transition metal complex is preferably a six-coordinate complex represented by the following general formula.

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,-, 2- or 3 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 can be mentioned, and preferred are 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), and osmium (Os).

The following are specific examples of the transition metal coordination complex.

[0061] 1: [RhCl _6] ^3- 2: [RuCl _6] ^3- 3: [ReCl _6] ^3- 4: [RuBr _6] ^3- 5: [OsCl _6] ^3- 6: [CrCl _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 : [Ru (NS) Cl _5] ^2- 24: _{[Re (NS) Cl 4 (SeCN} ) ] ^2- 25: [Os (NS) Cl (SCN) 4 ] ^2- 26: [Ir (NO) Cl _5] ^2- The ions or complex ions of these metals may be of one type, or two or more of the same and different metals may be used in combination. The content of these metal ions or complex ions is generally 1 × 10 ⁻⁹ to 1 mol per mol of silver halide.
1 × 10 ⁻² mol is appropriate, and preferably 1 × 10 ⁻⁸ to
It is 1 × 10 ^-4 mol. These compounds providing a metal ion or a complex ion are preferably added during silver halide grain formation and incorporated into silver halide grains. Preparation of silver halide grains, that is, nucleation, growth, physical ripening, It may be added at any stage before and after the chemical sensitization, but it is particularly preferable to add at the stage of nucleation, growth, and physical ripening, more preferably, at the stage of nucleation and growth, and most preferably. It is added at the stage of nucleation.

In the addition, it may be added in several divided portions, may be uniformly contained in the silver halide grains, or may be added to the 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). For example, a method in which 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 silver salt solution or a water-soluble halide solution during grain formation, or a silver salt solution. A method in which silver halide grains are prepared by a method of simultaneous mixing of three liquids when a halide solution is simultaneously mixed as a third aqueous solution, and a method in which a required amount of an aqueous solution of a metal compound is charged into a reaction vessel during grain formation. Alternatively, there is a method in which another silver halide grain doped with a metal ion or a complex ion 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 surface of the particles, 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 according to the present invention can be desalted by a known desalting method such as a noodle method, flocculation method, ultrafiltration method, and electrodialysis method.

The photosensitive silver halide grains are preferably chemically sensitized. As a preferable chemical sensitization method, a sulfur sensitization method, a selenium sensitization method, or a tellurium sensitization method well known in the art can be used. Further, a noble metal sensitization method such as a gold compound, a platinum compound, a palladium compound, and an iridium compound or a reduction sensitization method can be used.

The compounds preferably used in the sulfur sensitization method, selenium sensitization method, and tellurium sensitization method include known compounds,
For example, compounds described in JP-A-7-128768 can be used.

Examples of tellurium sensitizers include diacyl tellurides, bis (oxycarbonyl) tellurides, bis (carbamoyl) tellurides, bis (oxycarbonyl) ditellurides, bis (carbamoyl) ditellurides, and P = Te bond Compounds having the formula: tellurocarboxylates, Te-organyltellurocarboxylates, di (poly) tellurides, tellurides, tellurols, telluroacetals, tellurosulfonates, Te-containing heterocycles, tellurocarbonyl compounds, An inorganic tellurium compound, a colloidal tellurium compound, or the like can be used.

Compounds preferably used in the noble metal sensitization method include, for example, chloroauric acid, potassium chloroaurate, potassium aurithiocyanate, gold sulfide, gold selenide or US Pat. No. 2,448,060, British Patent 618, No. 061 or the like can be preferably used.

Specific compounds preferably used in the reduction sensitization method include, in addition to ascorbic acid and thiourea dioxide, for example, stannous chloride, aminoiminomethanesulfonic acid, hydrazine derivatives, borane compounds, silane compounds,
A polyamine compound or the like can be used.

Further, the pH of the emulsion was 7 or more and the pAg was 8.
Reduction sensitization can be achieved by ripening while keeping at 3 or less. Further, reduction sensitization can be achieved by introducing a single addition portion of silver ion during grain formation.

The heat-developable photographic light-sensitive material of the present invention comprises, as spectral sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, and hemioxonol dyes. Etc. can be used. For example, JP-A-63-1598
No. 41, No. 60-140335, No. 63-23143
No. 7, 63-259,651 and 63-304242
No. 63-15245, U.S. Pat. No. 4,639,4
No. 14, No. 4,740,455, No. 4,741,
No. 966, No. 4,751,175, No. 4,83
The spectral sensitizing dyes described in 5,096 can be used.

Useful spectral sensitizing dyes for use in the present invention include, for example, Research Disclosure.
(Hereinafter referred to as RD) 17643 IV-A (p. 23, December 1978) and Item 1831X (p. 437, August 1978). In particular, a spectral sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light source of various laser imagers and scanners can be advantageously selected. For example, JP-A-9-34
Compounds described in Nos. 078, 9-54409 and 9-80679 are preferably used.

Useful cyanine dyes are, for example, cyanine dyes having a basic nucleus such as a thiazoline nucleus, an oxazoline nucleus, a pyrroline nucleus, a pyridine nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus and an imidazole nucleus. 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 are also included.

These spectral sensitizing dyes may be used alone or in combination, and the combination of spectral sensitizing dyes is often used particularly for supersensitization.

Along with the spectral 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 spectral sensitizing dyes, combinations of dyes exhibiting supersensitization and substances exhibiting supersensitization are described in RD 176 Vol.
43 (issued in December 1978), page 23, IV, J, or Japanese Patent Publication No. 9-25500, Japanese Patent Publication No. 43-4933.
JP-A-59-19032 and JP-A-59-192242.
No. etc.

The reducing agents preferably used in the present invention include US Pat. Nos. 3,770,448 and 3,773.
No. 3,512, No. 3,593,863 and RD17
029 and 29996, and include the following.

Aminohydroxycycloalkenone compounds (for example, 2-hydroxypiperidino-2-cyclohexenone); aminoreductones as precursors of reducing agents;
Esters (for example, piperidinohexose reductone monoacetate); N-hydroxyurea derivatives (for example, Np-methylphenyl-N-hydroxyurea);
Aldehyde or ketone hydrazones (e.g., anthracene aldehyde phenylhydrazone); phosphoramidophenols; phosphoramidoanilines; polyhydroxybenzenes (e.g., hydroquinone, t-butyl-hydroquinone, isopropylhydroquinone and (2,5- Dihydroxy-phenyl) methylsulfone); sulfhydroxamic acids (eg, benzenesulfhydroxamic acid); sulfonamidoanilines (eg, 4- (N-methanesulfonamido) aniline);
-Tetrazolylthiohydroquinones (e.g., 2-methyl-5- (1-phenyl-5-tetrazolylthio) hydroquinone); tetrahydroquinoxalines (e.g.,
1,2,3,4-tetrahydroquinoxaline); amidooxines; azines (for example, a combination of an arylcarboxylic acid arylhydrazide and ascorbic acid);
Combinations of polyhydroxybenzene and hydroxylamine, reductone and / or hydrazine; hydroxanoic acids; combinations of azines and sulfonamidophenols; α-cyanophenylacetic acid derivatives; combinations of bis-β-naphthol and 1,3-dihydroxybenzene derivatives 5-pyrazolones; sulfonamidophenol reducing agents; 2-phenylindane-1,3-dione and the like; chromans; 1,4-dihydropyridines (eg, 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, 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 which particularly preferred reducing agents are hindered phenols. Examples of the hindered phenols include compounds represented by the following general formula (A).

[0079]

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In the general formula (A), R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms (for example, propyl,
Butyl, 2,4,4-trimethylpentyl, etc.), and R ′ and R ″ each represent an alkyl group having 1 to 5 carbon atoms (eg, each group such as methyl, ethyl, propyl, butyl, pentyl, etc.). ).

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

[0082]

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[0083]

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The amount of the reducing agent including the compound represented by the general formula (A) is preferably 1 × 10 ^-2 to 10 mol, more preferably 1 × 10 ^-2 to 1 mol per mol of silver.
1.5 mol.

The photothermographic material of the present invention preferably contains an antifoggant. What is known as the most effective antifoggant is mercury ion. The addition of a mercury compound as an antifoggant to a light-sensitive material is disclosed in, for example, US Pat. No. 3,589,903. However, since mercury compounds are environmentally unfavorable, non-mercury antifoggants include, for example, U.S. Pat. Nos. 4,546,075 and 4,452,885.
And antifoggants as described in JP-A-59-57234. Particularly preferred non-mercury antifoggant, a compound as described in U.S. Patent No. 3,874,946 and ibid. No. _{4,756,999, C- (X 1) (} X 2) (X 3 (Where X ₁ and X ₂ are halogen atoms, and X ₃ is a hydrogen atom or a halogen atom).

Examples of suitable antifoggants are described in
No. 288328, paragraphs [0030] to [003
6] are preferably used.
Other preferred antifoggants include JP-A-9-905.
No. 50, paragraphs [0062] to [0063]. Still other suitable antifoggants include, for example, U.S. Pat. No. 5,028,523 and British Patent Applications 9300147.7 and 93117.
No. 90.1.

It is preferable to add a color tone agent to the photothermographic material of the present invention. Toning agents are disclosed in US Pat.
Nos. 80254, 3847612 and 412
It is a material well known in the photographic art, as shown in US Pat. Examples of suitable toning agents are disclosed in RD 17029 and include:

Imides (for example, phthalimide); cyclic imides, pyrazolin-5-ones and quinazolinones (for example, succinimide, 3-phenyl-2-pyrazolin-5-one, 1-phenylurazole, quinazoline and 2,2) 4-thiazolidinedione); naphthalimides (for example, N-hydroxy-1,8-naphthalimide); cobalt complexes (for example, hexamine trifluoroacetate of cobalt), mercaptans (for example, 3
-Mercapto-1,2,4-triazole); N- (aminomethyl) aryldicarboximides (for example,
N- (dimethylaminomethyl) phthalimide); combinations of blocked pyrazoles, isothiuronium derivatives and certain photobleaches (eg, N, N'-hexamethylene (1-carbamoyl-3,5-dimethylpyrazole); 1,8- (3,6-dioxaoctane) bis (isothiuronium trifluoroacetate), and 2
-(Tribromomethylsulfonyl) benzothiazole combinations); merocyanine dyes (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 + benzenesulfin) Acid sodium salt or 8-methylphthalazinone + p-
Sodium trisulfonate); phthalazine + phthalic acid combination; phthalazine (including adducts of phthalazine)
And maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivative and its anhydride (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride) Quinazolinediones, benzoxazines, naltoxazine derivatives; benzoxazine-2,4-diones (for example,
Pyrimidines and asymmetric-triazines (eg, 2,4-dihydroxypyrimidine) and tetraazapentalene derivatives (eg, 3,6-dimercapto-1,4) -Diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene). Preferred toning agents are phthalazone or phthalazine.

The photothermographic material of the present invention may contain a mercapto compound or a disulfide compound for controlling development such as suppressing or accelerating development, improving spectral sensitization efficiency, or improving storage stability before and after development. , A thione compound or the like.

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

Preferred heteroaromatic rings include benzimidazole, naphthimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzoterzole, imidazole, oxazole, pyrazole, triazole, thiadiazole, tetrazole, triazine, pyrimidine. ,
Each ring such as pyridazine, pyrazine, pyridine, purine, quinoline or quinazolinone. The heteroaromatic ring includes, for example, a halogen atom (e.g., Br and Cl), a hydroxy group, an amino group, a carboxy group, an alkyl group (e.g., having one or more carbon atoms, preferably 1 to 4 carbon atoms. Mercapto-substituted heteroaromatics, which may have a substituent selected from the group consisting of a substituent group consisting of an alkyl group and an alkoxy group (e.g., having 1 or more carbon atoms, preferably 1 to 4 carbon atoms). As the compound, 2-
Mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-
Mercapto-5-methylbenzimidazole, 6-ethoxy-2-mercaptobenzothiazole, 2,2'-dithiobisbenzothiazole, 3-mercapto-1,2,2
4-triazole, 4,5-diphenyl-2-imidazolethiol, 2-mercaptoimidazole, 1-ethyl-2-mercaptobensoimidazole, 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, 21-mercaptopyrimidine, 4,6-diamino-2mercaptopyrimidine, 2-mercapto-4-methylpyrimidine hydrochloride, 3-mercapto-5-phenyl-1,
Examples include compounds such as 2,4-triazole and 2-mercapto-4-phenyloxazole, but the present invention is not limited thereto.

The addition amount of these mercapto compounds is preferably in the range of 0.001 to 1.0 mol per mol of silver in the photosensitive layer, more preferably 0.1 to 1.0 mol per mol of silver.
It is in an amount of from 0.01 to 0.3 mol.

In the heat-developable photographic light-sensitive material of the present invention, the protective layer on the side of the photosensitive layer preferably contains a matting agent. That is, a matting agent is provided on the surface of the photosensitive material in order to prevent the image after thermal development from being damaged.

The matting agent is preferably contained in a weight ratio of 0.5 to 30% with respect to all binders on the photosensitive layer side.

The material of the matting agent preferably used in the photothermographic material of the present invention may be either an organic substance or an inorganic substance. For example, as inorganic substances, Swiss Patent No. 33
No. 0,158, silica, 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. 2,322,037
And starch derivatives described in Belgian Patent No. 625,451 and British Patent No. 981,198, polyvinyl alcohol described in JP-B-44-3643, and Swiss Patent No. 330,158. Polystyrene or polymethacrylate described in US Pat.
Organic matting agents such as polyacrylonitrile described in No. 079,257 and polycarbonate described in U.S. Pat. No. 3,022,169 can be used.

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

The matting agent preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm.
m. The coefficient of variation of the particle size distribution is 5
0% or less, more preferably 40%
Or less, particularly preferably 30% or less.

Here, the coefficient of variation 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 is preferably a constituent layer other than the photosensitive layer, more 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 heat-developable photographic material of the present invention preferably contains a conductive compound such as a metal oxide and / or a conductive polymer in a constituent layer for preventing static charge. 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 layer, and the like. In the present invention, US Pat.
The conductive compounds described in No. 773 columns [0014] to [0020] are preferably used.

In addition, various additives may be added to any of the photosensitive layer, the non-photosensitive layer and other constituent layers.

The photothermographic material of the present invention may further include, for example, a surfactant, an antioxidant, a stabilizer, a plasticizer,
An ultraviolet absorber, a coating aid, or the like may be used. These additives and the other additives mentioned above are RD17029 (197
The compound described in "June 9, pp. 9-15" can be preferably used.

The binder preferably used in the photothermographic material of the present invention is transparent or translucent, generally colorless, and is composed of natural polymer synthetic resins, polymers and copolymers,
Other film forming media, for example, gelatin, gum arabic, polyvinyl alcohol, hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, polyvinyl pyrrolidone, casein, starch, polyacrylic acid, polymethyl methacrylic acid, polyvinyl chloride, polymethacryl Acid, styrene-maleic anhydride copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, polyvinyl acetals (for example, polyvinyl formal and polyvinyl butyral), polyesters, polyurethanes, phenoxy resins, polyvinylidene chloride , Polyepoxides,
There are polycarbonates, polyvinyl acetate, cellulose esters, and polyamides. It may be hydrophilic or non-hydrophilic.

In the photothermographic material of the present invention, the amount of binder in the photosensitive layer is preferably 1.5 to 10 g / m ² for the purpose of preventing dimensional fluctuation after heat development. More preferably, it is 1.7 to 8 g / m ² . 1.5 g / m ²
If it is less than 1, the density of the unexposed portion is significantly increased, and may not be usable.

The support used in the photothermographic material of the present invention may be a plastic film (for example, polyethylene terephthalate, polycarbonate, polyimide, or the like) in order to obtain a predetermined optical density after the development processing and to prevent deformation of the image after the development processing. Nylon, cellulose triacetate, polyethylene naphthalate) are preferred.

[0107] Among them, preferred supports include polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene naphthalate (hereinafter abbreviated as PEN), and plastics containing a styrene polymer having a syndiotactic structure (hereinafter SPS). Abbreviated). The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

Further, a heat-treated plastic support may 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.
Heating 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.

[0109]

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, and the temperature was adjusted to 35 ° C. and the pH to 3.0. Silver nitrate 74
g of an aqueous solution containing potassium bromide and potassium iodide in a molar ratio of (98/2) and [Ir (N
O) Cl ₅ ] ^2- salt at 1 × 10 ^-4 mole per mole of silver,
While maintaining the pAg at 7.7, it was added over 10 minutes by the controlled double jet method. Thereafter, 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene was added, the pH was adjusted to 5 with NaOH, the average particle size was 0.06 μm, the coefficient of variation of the particle size was 11%, and [10
0] Cubic silver iodobromide grains having an area 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 thereto.
It adjusted to 5.9 and pAg7.5. Further, it was optimally subjected to chemical sensitization with sodium thiosulfate and chloroauric acid to obtain a silver halide emulsion A.

(Preparation of Na Organic Acid Solution) 39.7 g of behenic acid, 2.3 g of arachidic acid and 6.1 g of stearic acid were dissolved in 1400 ml of pure water at 90 ° C. Next, while stirring at high speed, a 1.0 mol aqueous solution of sodium hydroxide 14
5.5 ml were added. Next, after adding 1.3 ml of concentrated nitric acid, the mixture was cooled to 30 ° C. to obtain an organic acid Na solution.

(Preparation of photosensitive emulsion EM-1) 15.1 g of the above-mentioned silver halide emulsion A was added to the above-mentioned organic acid Na solution, and the pH was adjusted to 8.1 with a sodium hydroxide solution. 147 ml of the solution was added over 7 minutes, the mixture was further stirred for 20 minutes, and water-soluble salts were removed by a microfiltration membrane. Next, while stirring the aqueous mixture, a solution of polyvinyl acetate in n-butyl acetate (boiling point: 126.1 ° C.) (1.
(2 wt%) 100 g was gradually added, and the mixture was allowed to stand. After forming a floc of the dispersion, the water was removed, followed by washing twice with water and removing water. Polyvinyl butyral (average molecular weight 3
000) of 2.5 wt% methyl ethyl ketone (boiling point 7
(9.6 ° C.) After adding 60 g of the solution with stirring, and further adding and mixing 60 g of polyvinyl butyral (average molecular weight: 4000) and methyl ethyl ketone, 4000 g were added.
The mixture was dispersed at psi to obtain a photosensitive emulsion EM-1.

(Preparation of photosensitive emulsion EM-2) 15.1 g of the above-mentioned silver halide emulsion A was added to the above-mentioned organic acid Na solution, and the pH was adjusted to 8.1 with a sodium hydroxide solution. 147 ml of the solution was added over 7 minutes, the mixture was further stirred for 20 minutes, and water-soluble salts were removed by a microfiltration membrane.

After drying for 24 hours (drying temperature: 40 ° C.) to remove water, 100 g of polyvinyl acetate in n-butyl acetate (1.2 wt%) was added to swell the emulsion, and polyvinyl butyral (average) was used. 60 g of a 2.5 wt% methyl ethyl ketone solution having a molecular weight of 3,000) was added with stirring, and then 60 g of polyvinyl butyral (average molecular weight: 4000) and methyl ethyl ketone were added and mixed, and then dispersed at 4000 psi to obtain a photosensitive emulsion EM-2. Was prepared.

(Preparation of photosensitive emulsion EM-3) Instead of n-butyl acetate, methyl isobutyl ketone (boiling point 116.
A photosensitive emulsion EM-3 was prepared in the same manner as in EM-1 except that 2 ° C.) was used.

(Preparation of photosensitive emulsion EM-4) A photosensitive emulsion EM-4 was prepared in the same manner as in EM-2 except that methyl isobutyl ketone was used instead of n-butyl acetate.

<Preparation of PET-undercoated support>
A corona discharge treatment of 8 w / m ² · min is applied to both sides of a 100 μm-thick PET film having been axially stretched and heat-fixed, and the following undercoating solution a-1 is applied to one side to a dry film thickness of 0.8 μm. And dried to form a subbing layer A1. On the opposite side, an antistatic subbing coating solution b-1 shown below was dried to a thickness of 0.
It was applied so as to have a thickness of 8 μm and dried to obtain an undercoat layer B1 having an antistatic treatment.

<Undercoat Coating Solution a-1> Butyl acrylate (30 wt%) t-butyl acrylate (20 wt%) Styrene (25 wt%) 2-hydroxyethyl acrylate (25 wt%) copolymer latex liquid (Solid content: 30%) 270 g (C-1) 0.6 g hexamethylene-1,6-bis (ethylene urea) 0.8 g Finished to 1 liter with water <Undercoat coating solution b-1> Butyl acrylate (40 wt. %) 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 Finishing to 1 liter with water Then, 8w on the upper surface of the undercoat layer A1 and the undercoat layer B1
/ M ² · corona discharge, and on the undercoat layer A1,
The following undercoating upper layer coating solution a-2 was used as the undercoating layer A2 so as to have a dry film thickness of 0.1 μm. The undercoating layer B2 having an antistatic function was applied so as to obtain

<Undercoating upper layer coating liquid 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 upper layer coating solution 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

[0120]

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[0121]

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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) The following layers were sequentially formed on the support to prepare Samples 1 to 4. The drying was performed at 60 ° C. for 15 minutes. Further, the photosensitive emulsion EM
Sample Nos. 5 to 16 were prepared by changing -1 to photosensitive emulsions EM-2 to EM-4, respectively.

Back side coating: A liquid having the following composition was applied.

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

[0126]

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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.
It was applied so that it became.

Photosensitive emulsion EM-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 0.7 ml Antifoggant-2 (10% methanol solution) 1.2 ml 2- (4-chlorobenzoylbenzoic acid (12% methanol solution) 9.2 ml 2-mercaptobenzimidazole (1% methanol solution) 11 ml tribromomethylsulfo Quinoline (5% methanol solution) 17 ml Developer-1 (20% methanol solution) 29.5 ml Hardener H (1% methanol / N, N-dimethylformamide = 4: 1 solution) 2 ml

[0129]

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[0130]

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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 80 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 (Performance of photothermographic material (Evaluation) <Exposure and Development Processing> The photothermographic material prepared above was exposed with an imager having a semiconductor laser of 810 nm. Thereafter, using an automatic developing machine having a heat drum, heat development was performed at a developing temperature shown in Table 1 for 15 seconds. At that time, exposure and development were performed in a room conditioned at 23 ° C. and 50% RH.

<Evaluation of Photographic Performance> The image obtained after the heat development was evaluated with a densitometer. The measurement results were evaluated in terms of fog (Dmin) and sensitivity (the reciprocal of the ratio of the exposure amount giving a density higher than Dmin by 1.0). The sensitivity is the same as that of Sample No.
The sensitivity of 5 was set as 100 and the relative sensitivity was shown.

<Evaluation of Image Preservation> A sample treated in the same manner as in the evaluation of photographic performance was stored at 55 ° C. and 55% RH for 7 days under light-shielded conditions, and the color tone was observed.

Evaluation Criteria 5: Color tone without any problem 4: Color tone without practical problem 3: Color tone slightly yellowish but not problematic 2: Color tone unpleasant and possibly problematic 1: A remarkable change was recognized, and the color tone was a practical problem. The above results are shown in Table 1.

[0136]

[Table 1]

From Table 1, it can be seen that thermal development using an organic silver salt dispersion obtained by adding an organic solvent having a boiling point equal to or lower than the developing temperature to an aqueous layer dispersion of the organic silver salt of the present invention and converting the layer into an organic solvent layer. It can be seen that the photosensitive material is excellent in sensitivity, photographic performance such as fogging, and image storability.

Example (2) (Evaluation of Dispersion of Organic Silver Salt) Measurement of Average Particle Size Regarding EM-1 and EM-3 of Example 1, the layer was changed from a water tank to an organic solvent layer, and water was removed. The removed organic silver salt dispersion, and for EM-2, the organic silver salt dispersion from which water was removed by drying for 24 hours instead of separating water and the organic solvent layer was observed with a transmission electron microscope. The particle size of 1000 particles was randomly measured, and the average particle size was calculated.

Measurement of the degree of dispersion The same sample was calculated by the following equation using the average major axis particle size.

Monodispersity = (standard deviation of particle size) / (average particle size) × 100 Table 2 shows the average particle size and the degree of dispersion of the silver salt of organic acid contained in the obtained photosensitive emulsion.

[0141]

[Table 2]

As is clear from Table 2, the organic silver salt dispersion obtained by adding an organic solvent having a boiling point not higher than the development temperature to the aqueous layer dispersion of the organic silver salt of the present invention and converting the organic silver salt into an organic solvent layer was an average. It can be seen that the organic silver salt dispersion has a small particle size and improved monodispersibility.

[0143]

According to the present invention, a photothermographic material, an image forming method and an organic silver salt dispersion having improved photographic performance such as sensitivity, fog and image storability can be obtained.

Claims (6)

[Claims] 1. An image forming method using a photothermographic material having a recording layer containing an organic silver salt, a photosensitive silver halide and a reducing agent on a support, wherein the heat development temperature is equal to the production of the organic silver salt. An image forming method using a photothermographic material, wherein the temperature is higher than the boiling point of the organic solvent used in the process. 2. An organic solution prepared by subjecting an organic silver salt to a layer conversion from an aqueous layer to an organic solvent layer by adding an organic solvent having a boiling point below the thermal development temperature and then separating the organic solvent layer and the aqueous layer. The image forming method using the photothermographic material according to claim 1, wherein the image forming method is a silver salt. 3. The organic solvent according to claim 1, wherein the solubility in water at 20 ° C. is 5 wt% or less.
An image forming method using the photothermographic material according to item 1. 4. An aqueous dispersion of an organic silver salt is prepared by adding silver nitrate to an aqueous dispersion in which fine particles of an alkali metal salt of an organic acid are dispersed. An organic solvent having a boiling point is added, the organic silver salt is subjected to a layer conversion from an aqueous layer to an organic solvent layer, and then the organic solvent layer and the aqueous layer are separated. Production method. 5. The method for producing an organic silver salt dispersion according to claim 4, wherein the solubility of the organic solvent in water at 20 ° C. is 5 wt% or less. 6. A photothermographic material having a recording layer containing an organic silver salt, a photosensitive silver halide and a reducing agent on a support, wherein the organic silver salt is an organic solvent having a boiling point not higher than the heat development temperature. A photothermographic material, characterized in that an aqueous dispersion of an organic silver salt is obtained by the addition thereof through a layer conversion process from an aqueous layer to an organic solvent layer.