JP2003075954A - Heat developable photosensitive material and imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat developable photographic sensitive material having high sensitivity, less liable to fog, suppressing fogging and a sensitivity change in storage, suppressing fog density, its change and color tone deterioration particularly due to printout and ensuring improved image stability after development. SOLUTION: The heat developable photosensitive material is obtained by disposing a photosensitive layer comprising at least an organic silver salt, silver halide, a reducer and a thermotropic liquid crystal on a support. Preferably the transition temperature of the thermotropic liquid crystal from the solid state to the liquid-crystalline state is 50-150 deg.C and preferably the transition temperature of the thermotropic liquid crystal from the solid state to the liquid- crystalline state is >=50 deg.C and the transition temperature from the liquid- crystalline state to an isotropic liquid is <=150 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photothermographic material for forming an image by heat development and an image forming method using the same, and more particularly to a technique for improving fog of an image formed.

[0002]

2. Description of the Related Art In recent years, in the fields of printing and plate making and medical treatment, a waste liquid caused by wet processing of image forming materials has become a problem in terms of workability. Weight loss is strongly desired. Therefore, there is a need for a technology relating to a photothermographic material that can be efficiently exposed by a laser imagesetter and can form a clear black image with high resolution. Examples of this type of technique include U.S. Pat. Nos. 3,152,904, 3,487,075 and D.I. Morgan
n) "Dry Silver Photographic Material (Dry Sil
ver Photographic Material
s) "(Handbook of Imaging M
materials, Marcel Dekker, I
nc. The light-sensitive materials described in page 48, 1991) are known. Since these photosensitive materials are usually developed at a temperature of 80 ° C. or higher, they are called thermal development materials.

Such heat-developable materials usually contain a reducible silver source (eg organic silver salt), a catalytically active amount of a photocatalyst (eg silver halide) and a reducing agent dispersed in an organic binder matrix. However, it is stable at room temperature, but when heated to a high temperature after exposure, silver is produced by a redox reaction between a reducible silver source (acting as an oxidizing agent) and the reducing agent. This redox reaction is promoted by the catalytic action of the latent image produced by exposure. The silver produced by the reaction of the organic silver salt in the exposed areas provides a black image, which contrasts with the unexposed areas and forms an image.

However, the above-mentioned heat-developable material has a drawback that undesired formation of silver occurs in a white background portion having no image and fog is formed. As a technique for suppressing the fogging of the image, a method using various halogen compounds has been proposed so far, for example, US Pat. No. 3,874,946.
No. 4,459,350, 5,340,712
No. 4,756,999, No. 5,594,143
No. 5,594,143, JP-A-58-59439.
Nos. 59-46641 and 59-57233.

Further, JP-A-6-208193 discloses a photothermographic emulsion in which a compound having an isocyanate group and a halogenated antifoggant are used together as a means for improving the fog stability during storage.

However, the above-mentioned technique is not sufficient in the fog-preventing effect, or one having a high fog-preventing effect has a problem that it causes a decrease in sensitivity and thus needs to be improved. Further, when an unused light-sensitive material is stored and aged, there are problems that fog is increased and sensitivity is changed.
Furthermore, after development, the fog rise (printout) that occurs when exposed to room light or Schaukasten light, the change in printout density during exposure, color deterioration due to printout, or the temporal stability of the image after printout is It was still insufficient. Further, there is a drawback that fog increases when conditions such as development temperature are raised in order to shorten the development time, so that development of a fog prevention technique without such a problem has been desired.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide high sensitivity with less fog generation and to suppress fog formation and sensitivity fluctuation during storage. In particular, it is an object of the present invention to provide a photothermographic material in which the fog density, its fluctuation and color tone deterioration due to printout are suppressed and the image stability after development processing is improved.

[0008]

The above object of the present invention is to provide a photothermographic material comprising a support and a photosensitive layer containing at least an organic silver salt, a silver halide, a reducing agent and a thermotropic liquid crystal provided on the support. Achieved

The transition temperature from the solid state to the liquid crystal state of the thermotropic liquid crystal is 50 to 150 ° C., the transition temperature from the solid state to the liquid crystal state of the thermotropic liquid crystal is 50 ° C. or more, and the liquid crystal It is a preferable embodiment that the transition temperature from the state to the isotropic liquid is 150 ° C. or lower.

The present invention also includes an image forming method in which the above-mentioned heat-developable photosensitive material is exposed to laser and heated and developed.

The present invention will be described in more detail below. The photothermographic material of the invention has a photosensitive layer containing an organic silver salt, a silver halide, a reducing agent and a thermotropic liquid crystal on a support. A protective layer is provided on the photosensitive layer, a backing layer (hereinafter, also simply referred to as a BC layer) on the side opposite to the side having the photosensitive layer with respect to the support, and a protective layer also on the BC layer. Is preferred. The photosensitive layer contains an organic silver salt serving as a silver source, a silver halide which may be sensitized, and a reducing agent for developing a silver salt to form a silver image.

First, the thermotropic liquid crystal of the present invention will be described. Thermotropic liquid crystal is a substance that changes from solid state to liquid crystal state to isotropic liquid by heat, and known compounds can be used. Examples thereof include aromatic carboxylic acids and their derivatives, polycyclic hydrocarbons and their derivatives, azomethine compounds, bisazomethine compounds, hydrazine derivatives, azo compounds, azomethine-azo compounds, azoxy compounds, sterols and steroid derivatives.

The transition temperature of the thermotropic liquid crystal from the solid state to the liquid crystal state must be 50 to 150 ° C.
More preferably, it is 80 to 100 ° C.

The transition temperature of the liquid crystal state ⇒ isotropic liquid is 8
The temperature is preferably 0 to 150 ° C., more preferably 100 to 120 ° C., but preferably at least 10 ° C. or higher than the transition temperature from the solid state to the liquid crystal state.

Typical examples of thermotropic liquid crystal (also referred to as the liquid crystal compound of the present invention) preferably used in the present invention are shown below, but the invention is not limited thereto.

[0016]

[Chemical 1]

[0017]

[Chemical 2]

The addition amount of the thermotropic liquid crystal is preferably from 0.01 to 10 g / m ^2, more preferably 0.1-2 g / m ^2. The solubility in the coating solvent is 0 to 0.5% by mass, preferably 0 to 0.05% by mass.

Next, the support, organic silver salt, silver halide and reducing agent will be described in order. As the support used in the present invention, polyethylene terephthalate (PE
T), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS) and the like are preferable, and 2
It is preferably axially stretched or heat-fixed and has high optical isotropy and good dimensional stability, usually 50 to 400 μm thick.

In the present invention, the organic silver salt is a reducible source of silver, and is a silver salt of an organic acid or a heteroorganic acid, especially a long-chain (C30-30, preferably 15-25) aliphatic carboxylic acid and Silver salts of nitrogen-containing heterocyclic compounds are preferred. The ligand has a total stability constant of 4.0 to 1 for silver ions.
Organic or inorganic complexes having a value of 0.0 are also preferred. Examples of these suitable silver salts include Research
Disclosure (RD) 17029 and 299
63, and includes the following.

Silver salts of organic acids: eg gallic acid, oxalic acid, behenic acid, stearic acid, arachidic acid, palmitic acid,
Silver salts such as lauric acid. Carboxyalkyl thiourea salt of silver: for example, 1- (3-carboxypropyl) thiourea,
Silver salts such as 1- (3-carboxypropyl) -3,3-dimethylthiourea. Silver salt or complex of polymer reaction product of aldehyde and hydroxy-substituted aromatic carboxylic acid: For example, aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) and hydroxy-substituted acids (salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid,
5,5-thiodisalicylic acid) as a reaction product of silver salt or complex. Silver salt or complex of thiones: For example, silver salt or complex of 3- (2-carboxyethyl) -4-hydroxymethyl-4-thiazoline-2-thione, 3-carboxymethyl-4-thiazoline-2-thione and the like. Imidazole, pyrazole, urazole, 1,2,4-thiazole and 1
H-tetrazole, 3-amino-5-benzylthio-
A complex or salt of a nitric acid and silver selected from 1,2,4-triazole and benzotriazole. saccharin,
Silver salts such as 5-chlorosalicylaldoxime and silver salts of mercaptides.

Of these, preferred silver salts are silver behenate, silver arachidate and silver stearate.

The organic silver salt can be obtained by mixing a water-soluble silver compound and a compound which forms a complex with silver, and it is described in the forward mixing method, the reverse mixing method, the simultaneous mixing method, and JP-A-9-127643. The controlled double jet method or the like is preferably used. For example, an alkali metal salt (sodium hydroxide, potassium hydroxide, etc.) is added to an organic acid to prepare an organic acid alkali metal salt soap (sodium behenate, sodium arachidate, etc.), and the soap is then treated with a controlled double jet. And silver nitrate, etc. are added to produce organic silver salt crystals. At that time, silver halide grains may be mixed.

In the present invention, the organic silver salt has an average particle size of 2
It is preferably μm or less and monodisperse. With the average particle size of the organic silver salt, particles of the organic silver salt are, for example, spherical,
In the case of rod-like or tabular grains, it means the diameter of a sphere equivalent to the volume of organic silver salt grains. Average particle size is 0.0
5 to 1.5 μm is preferable, especially 0.05 to 1.0 μm
Is preferred. The monodispersion has the same meaning as in the case of silver halide described below, and the monodispersity is preferably 1 to 30.

In the present invention, the tabular grains of the organic silver salt grains preferably account for 60% or more of all the organic silver salts. The tabular grains are grains having a ratio of grain size to thickness, that is, an aspect ratio (AR) represented by the following formula of 3 or more.

AR = particle size (μm) / thickness (μm) In order to form the organic silver salt into these shapes, the organic silver salt crystals are dispersed and pulverized by a ball mill or the like together with a binder, a surfactant and the like. can get. Within this range, a light-sensitive material having high density and excellent image storability can be obtained.

The silver halide contained in the photosensitive layer will be described. Silver halide functions as an optical sensor.
In the present invention, in order to suppress white turbidity after image formation to a low level and to obtain good image quality, it is preferable that the average grain size of silver halide grains is small, and the average grain size is 0.1 μm or less. Preferably, it is more preferably 0.01 to 0.1 μm, and especially 0.02 to 0.08 μm.
Is preferred.

The particle size referred to here means the diameter of a circle (equivalent circle diameter) having the same area as an individual particle image observed by an electron microscope. The silver halide is preferably monodisperse. The monodisperse here means that the coefficient of variation of the particle size distribution obtained by the following formula is 40% or less. The coefficient of variation is more preferably 30% or less, and particularly preferably 20% or less.

Coefficient of variation of particle distribution = (standard deviation of particle size /
The average value of the grain size) × 100 The shape of the silver halide grain is not particularly limited,
The ratio of the Miller index (100) plane is preferably high, and the ratio is preferably 50% or more, more preferably 70% or more, and particularly preferably 80% or more. Miller index (10
The ratio of the (0) plane is measured by T.W., which utilizes the adsorption dependence of the (111) plane and the (100) plane in the adsorption of the sensitizing dye. Tani,
J. Imaging Sci. , 29, 165 (198
It can be determined by 5).

Another preferred silver halide shape is tabular grain. The tabular grains referred to here mean that the square root of the projected area is the grain size r μm and the vertical thickness is h μm.
In this case, the aspect ratio = r / h is 3 or more. Among them, the aspect ratio is preferably 3 to 50. Further, the particle size is preferably 0.1 μm or less,
Furthermore, 0.01 to 0.08 μm is preferable. Such tabular grains are disclosed in US Pat.
No. 4,798,5,320,958, etc., and the target tabular grain can be easily obtained.

The halogen composition of silver halide is not particularly limited, and silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide,
It may be either silver iodobromide or silver iodide. The silver halide emulsion used in the present invention is described in P. Glafkides
Written by: Chimie et Physique Phot
ographique (published by Paul Montel,
1967), G. F. Duffin: Photog
radical Emission Chemistry
(Published by The Focal Press, 1966),
V. L. Zelikman et al: Makin
g and Coating Photographi
c Emulsion (The Focal Pres
S., 1964) and the like. That is, any of an acidic method, a neutral method, an ammonia method and the like may be used, and as the formation of reacting the soluble silver salt and the soluble halogen salt, any one of a one-sided mixing method, a simultaneous mixing method and a combination thereof may be used. Good.

The silver halide used in the present invention preferably contains a metal ion belonging to Groups 6 to 11 of the periodic table. As the metal of the metal ion, W, F
e, Co, Ni, Cu, Ru, Rh, Pd, Re, O
It is preferably at least one selected from s, Ir, Pt and Au.

These metal ions can be introduced into the silver halide in the form of metal complexes or metal complex ions. As the ligand for complex formation, halides (fluorides, chlorides, bromides and iodides), cyanides, cyanates, thiocyanates, selenocyanates, tellurocyanates,
Azido and aco ligands, nitrosyl, thionitrosyl and the like can be mentioned, with preference given to aco, nitrosyl and thionitrosyl and the like.

The content of metal ion, metal complex or metal complex ion is generally 1 × 10 ^-9 to 1 × 10 ^-2 mol per mol of silver halide, and preferably 1 × 10 9. ^-8 to 1 × 10 ^-4 mol.

The silver halide grains may or may not be desalted after grain formation. When desalting is carried out, desalting is carried out by washing with water by a method known in the art such as a noodle method or a flocculation method. can do.

The 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, platinum, palladium, or iridium compound or a reduction sensitization method can be applied.

The photosensitive layer of the photothermographic material is described in JP-A-63 / 63.
-159841, 60-140335, 63-
231437, 63-259651, 63-3
04242, 63-15245, U.S. Pat.
39,414, 4,740,455, 4,74
1,966, 4,751,175, 4,83
The sensitizing dyes described in 5,096 and the like can be used. Useful sensitizing dyes are, for example, Research Discl.
(RD), 17643, IV-A (1978)
December 23, page 23) or cited. In particular, a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various scanner light sources can be advantageously selected.

These sensitizing dyes may be used alone,
A combination of sensitizing dyes is often used especially for the purpose of supersensitization. Along with a sensitizing dye, a dye that does not have a spectral sensitizing effect itself or a substance that does not substantially absorb visible light and that exhibits supersensitization (such as a heteroaromatic mercapto compound) is included in the emulsion. May be.

Since the photosensitivity is particularly high when supersensitized, the printout silver after development tends to be large unless the reducing agent is deactivated, and the present invention is particularly effective. Further, when infrared sensitized, the infrared sensitizing dye further has an oxidation-reduction potential capable of reducing silver halide or an organic silver salt to some extent. In the presence of a reducing agent capable of reducing the organic silver salt of, silver clusters that become fog silver are likely to be formed. The generated silver clusters also act as catalyst nuclei to induce fog, which leads to deterioration of storage stability when stored in a dark place,
Further, when it is placed in a bright place after development, a phenomenon such as an increase in printout silver occurs. Further, since the sensitivity of the infrared sensitive material extends to the heat radiation region outside the visible light range, the present invention is effective against the fact that the printout silver due to the heat radiation increases even in a dark place. . In particular, the effect is great in the case of infrared spectrally sensitized light-sensitive materials in which the sensitivity is increased by a supersensitizer.

The photosensitive layer of the present invention may contain a polyhalomethane compound. The polyhalomethane compound preferably used is a compound having a polyhalomethyl group, and the polyhalomethyl group is directly or via a linking group to an aromatic group (phenyl, naphthyl, chlorophenyl, etc.) or a heterocyclic group (pyridyl, furyl, imidazolyl, oxazolyl, etc.). Those bonded together are preferred. Preferred linking _{groups, -CO -, - SO 2 -} , - NHSO 2 - and the like. Examples of the polyhalomethyl group include tribromomethyl, trichloromethyl, dibromomethyl and the like. The amount of polyhalomethane compound added is 1 × 10 ⁻⁸ to 1 × 1 with respect to 1 mol of silver halide.
0 ^-2 mol are preferred. The chemical compound may be added at the time of chemical sensitization or at any time after chemical sensitization and immediately before coating.

In order to prevent devitrification of the light-sensitive material, the total amount of silver halide and organic silver salt is preferably 0.5 to 2.2 g per m ² in terms of silver amount. Within this range, a high contrast image can be obtained. Further, the amount of silver halide with respect to the total amount of silver is 50% or less by mass ratio, preferably 2
It is 5% or less, more preferably 0.1 to 15%.

As the reducing agent used in the photothermographic material of the present invention, those known in the art can be used. For example, phenols, polyphenols having two or more phenol groups, and naphthols. , Bisnaphthols, polyhydroxybenzenes having two or more hydroxyl groups, polyhydroxynaphthalenes having two or more hydroxyl groups, ascorbic acids, 3-
Pyrazolidones, pyrazolin-5-ones, pyrazolines, phenylenediamines, hydroxylamines, hydroquinone monoethers, hydrooxamic acids,
Hydrazides, amidoximes, N-hydroxyureas, etc., and more specifically, US Pat. No. 3,615,53.
No. 3, No. 3,679,426, No. 3,672,904
No. 3,751,252, No. 3,782,949
No. 3,811,321, 3,794,488
No. 3,893,863, No. 3,887,376
Issue No. 3,770,448 Issue 3,819,382
No. 3,773,512, No. 3,839,048
No. 3, No. 3,887,378, No. 4,009,039
No. 4,021,240, British Patent 1,486,1
48 or Belgian Patent 786,086 and JP-A-50-36143, 50-36110, 50.
-116023, 50-99719, 50-1
40113, 51-51933, 51-237.
No. 21, No. 52-84727 or Japanese Patent Publication No. 51-3
There are reducing agents specifically exemplified in No. 5851 and the like, which can be appropriately selected and used from such known reducing agents.

Among the above reducing agents, when an aliphatic carboxylic acid silver salt is used as the organic silver salt, a preferable reducing agent is a polyphenol in which two or more phenol groups are linked by an alkylene group or sulfur, particularly Two or more phenol groups substituted with an alkyl group (methyl, ethyl, propyl, t-butyl, cyclohexyl, etc.) or an acyl group (acetyl, propionyl, etc.) in at least one of the positions adjacent to the hydroxy-substituted position of the phenol group Polyphenols linked by alkylene groups or sulfur, such as 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane,
1,1-bis (2-hydroxy-3-t-butyl-5-
Methylphenyl) methane, 1,1-bis (2-hydroxy-3,5-di-t-butylphenyl) methane, (2-
Hydroxy-3-t-butyl-5-methylphenyl)-
(2-hydroxy-5-methylphenyl) methane, 6,
6'-benzylidene-bis (2,4-di-t-butylphenol), 6,6'-benzylidene-bis (2-t-)
Butyl-4-methylphenol), 6,6'-benzylidene-bis (2,4-dimethylphenol), 1,1-
Bis (2-hydroxy-3,5-dimethylphenyl)-
2-methylpropane, 1,1,5,5-tetrakis (2
-Hydroxy-3,5-dimethylphenyl) -2,4-
Ethyl pentane, 2,2-bis (4-hydroxy-3,
5-dimethylphenyl) propane, 2,2-bis (4-
Hydroxy-3,5-di-t-butylphenyl) propane etc. U.S. Pat. Nos. 3,589,903, 4,021,
No. 249 or British Patent 1,486,148 and JP-A Nos. 51-51933, 50-36110 and 50-.
No. 116023, No. 52-84727, Japanese Patent Publication No. 51-35727, and the like; bisnaphthols described in U.S. Pat. No. 3,672,904, for example, 2,2'-dihydroxy-1,1. ′
-Binaphtyl, 6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl, 6,6'-dinitro-
2,2'-dihydroxy-1,1'-binaphthyl, bis (2-hydroxy-1-naphthyl) methane, 4,4'-
Dimethoxy-1,1'-dihydroxy-2,2'-binaphthyl and the like; further sulfonamide phenols or sulfonamide naphthols such as those described in U.S. Pat. No. 3,801,321, such as 4-benzenesulfonamide phenol, 2 -Benzenesulfonamide phenol,
2,6-dichloro-4-benzenesulfonamide phenol, 4-benzenesulfonamide naphthol and the like can be mentioned.

The amount of reducing agent used varies depending on the type of organic silver salt or reducing agent and other additives, but is generally 0.05 to 10 moles, preferably 0 mole per mole of organic silver salt. 0.1-3 mol is suitable. Further, within this range, two or more of the above-mentioned reducing agents may be used in combination.

In the photothermographic material, it is desirable to use an additive (hereinafter referred to as a "toning agent") called a toning agent, a toning agent or an activator toner together with the above-mentioned components.

The toning agent has a function of participating in the redox reaction between the organic silver salt and the reducing agent to make the resulting silver image a dark color, especially black. Examples of suitable toning agents used in the present invention are:
RD17029, page 11, item V (June 1978), and includes the following.

Imides (phthalimide etc.); Cyclic imides, pyrazolin-5-ones, and quinazolinones (succinimide, 3-phenyl-2-pyrazolin-5-one, 1-phenylurazole, quinazoline, 2,4- Thiazolidinedione etc.); naphthalimides (N-hydroxy-1,8-naphthalimide etc.); cobalt complexes (cobalt hexamine trifluoroacetate etc.),
Mercaptans (3-mercapto-1,2,4-triazole etc.); N- (aminomethyl) aryl dicarboximides (N- (dimethylaminomethyl) phthalimide etc.); Blocked pyrazoles, isothiuronium derivatives and or Photobleach combinations (N, N'-hexamethylene (1-carbamoyl-3,5-dimethylpyrazole), 1,8- (3,6-dioxaoctane) bis (isothiuronium trifluoroacetate) ) And 2
-(Tribromomethylsulfonyl) benzothiazole combination); merocyanine dye (3-ethyl-5-
((3-Ethyl-2-benzothiazolinylidene (benzothiazolinylidene))-1-methylethylidene) -2-
Thio-2,4-oxazolidinedione and the like); phthalazinone, phthalazinone derivatives or metal salts of these derivatives (4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone and 2, 3-dihydro-1,4-phthalazinedione, etc.); Combination of phthalazinone and sulfinic acid derivative (6-chlorophthalazinone + sodium benzenesulfinate or 8
-Methylphthalazinone + sodium p-trisulfonate, etc.); Combination of phthalazine + phthalic acid; Phthalazine (including adduct) and maleic anhydride, and phthalic acid, 2,
3-naphthalenedicarboxylic acid or o-phenylene acid derivative and its anhydride (phthalic acid, 4-methylphthalic acid, 4
-Nitrophthalic acid and tetrachlorophthalic anhydride)
A combination with at least one compound selected from: quinazolinediones, benzoxazine, naltoxazine derivatives; benzoxazine-2,4-diones (1,3
-Benzoxazine-2,4-dione); pyrimidines and asymmetric-triazines (2,4-dihydroxypyrimidine), and tetraazapentalene derivatives (3,6)
-Dimercapto-1,4-diphenyl-1H, 4H-
2,3a, 5,6a-tetraazapentalene and the like). The preferred toning agent is phthalazone or phthalazine.

The binder suitable for the photosensitive layer of the photothermographic material of the present invention is transparent or translucent, and generally colorless.
Natural and synthetic polymers and copolymers, etc.
Film forming media such as gelatin, gum arabic, polyvinyl alcohol, hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, polyvinylpyrrolidone, casein, starch, polyacrylic acid, polymethylmethacrylate, polymethacrylic acid, polyvinyl chloride, styrene. -Maleic anhydride copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, polyvinyl acetals (polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resin, polyvinylidene chloride, polyepoxides, Polycarbonates,
There are polyvinyl acetates, cellulose esters, polyamides and the like, which may be hydrophilic or non-hydrophilic. However, among these binders, particularly preferred are water-insoluble polymers such as cellulose acetate, cellulose acetate butyrate and polyvinyl butyral, and of these, polyvinyl butyral is particularly preferred.

[0049] In the present invention, it is preferred that the binder of the photosensitive layer is a 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. If it is less than 1.5 g / m ² , the density of the unexposed area may increase significantly and it may not be usable.

In the present invention, a matting agent is preferably contained in the photosensitive layer side, and a matting agent is preferably arranged on the surface of the photosensitive material in order to prevent scratching of an image after heat development. To all binders on the photosensitive layer side.
It is preferable to contain 5 to 30 mass%.

When a non-photosensitive layer is provided on the opposite side of the photosensitive layer with the support interposed, it is preferable to include a matting agent in at least one layer on the non-photosensitive layer side so that the slipperiness and fingerprints of the photosensitive material can be improved. It is preferable to dispose a matting agent on the surface of the light-sensitive material also for prevention of adhesion, and it is preferable to contain the matting agent in an amount of 0.5 to 40% by mass with respect to the total binder of the layer on the side opposite to the photosensitive layer.

The matting agent used may be either organic or inorganic. For example, as the inorganic substance, silica described in Swiss Patent No. 330,158, glass powder described in French Patent No. 1,296,995, alkaline earth metal described in British Patent No. 1,173,181, etc. Alternatively, a carbonate such as cadmium or zinc can be used. Examples of the organic substance include starch described in U.S. Pat. No. 2,322,037 and the like, starch derivatives described in Belgian Patent 625,451 and British Patent 981,198, and JP-B-44.
-3643 and the like polyvinyl alcohol, Swiss Patent 330,158 and the like polystyrene or polymethacrylate, U.S. Pat. No. 3,079,257 and the like, polyacrylonitrile and U.S. Pat. No. 3,022,1.
An organic matting agent such as polycarbonate described in No. 69 can be used.

The shape of the matting agent may be either a fixed shape or an indefinite shape, but a fixed shape is preferable, and a spherical shape is preferably used. The size of the matting agent is represented by the diameter when the volume of the matting agent is converted into a spherical shape. In the present invention, the particle size of the matting agent refers to this spherical equivalent diameter.

The matting agent used in the present invention preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm. The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30%.
It is the following. The coefficient of variation of the grain size distribution has the same meaning as in the silver halide grain.

The matting agent may 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 matting agent may be added by dispersing it in the coating solution in advance and applying it, or by spraying the matting agent after applying the coating solution and before drying is completed. or,
When a plurality of types of matting agents are added, both methods may be used together.

Further, in the photothermographic material of the present invention, an isocyanate compound described in Japanese Patent Application No. 2000-44358, an oxidizing agent described in Japanese Patent Application No. 2001-4996, a hydrazine compound, a polyhalomethane compound, a disulfide compound, a crosslinking agent, a phthalazine compound, A phthalic acid compound, a dye or the like can be used in combination.

The photothermographic material of the present invention has at least one photosensitive layer on a support. Although only the photosensitive layer may be formed on the support, at least one photosensitive layer may be formed on the photosensitive layer.
It is preferred to form the non-photosensitive layer of the layer. In order to control the amount or wavelength distribution of light transmitted through the photosensitive layer, a filter layer may be formed on the same side as the photosensitive layer or on the opposite side,
The photosensitive layer may contain a dye or a pigment. As the dye, the compounds described in JP-A 8-201959 are preferred.

The photosensitive layer may be composed of a plurality of layers, or a high-sensitivity layer and a low-sensitivity layer may be provided for adjusting gradation and these may be combined. Various additives may be added to any of the light-sensitive layer, the non-light-sensitive layer and other layers. The photothermographic material may contain, for example, a surfactant, an antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber, a coating aid and the like.

Next, an image forming method using the photothermographic material of the present invention will be described. For image formation, two steps of exposure → development are adopted. First, the exposure will be described.

For exposure, an argon ion laser (48
8 nm), He-Ne laser (633 nm), red semiconductor laser (670 nm), infrared semiconductor laser (7
80 nm, 820 nm) and the like are preferably used, but an infrared semiconductor laser is more preferably used from the viewpoint that the laser power is high and the photothermographic material can be made transparent.

In the present invention, it is preferable to use a laser scanning exposure machine in which the angle formed by the scanning laser light and the exposed surface of the photothermographic material is not substantially vertical.

As used herein, the phrase "substantially no vertical" is preferably 55 to 88 degrees, more preferably 60 to 86, as an angle that is the most vertical during laser scanning.
Degrees, more preferably 65 to 84 degrees, most preferably 70 degrees.
Say it is ~ 82 degrees.

The beam spot diameter on the exposed surface of the photothermographic material when the laser beam is scanned on the photothermographic material is preferably 200 μm or less, more preferably 100 μm or less.
μm or less. It is preferable that the spot diameter is smaller because the angle of deviation of the laser incident angle from the vertical can be reduced. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce deterioration of image quality due to reflected light such as occurrence of interference fringe-like unevenness.

Further, it is preferable that the exposure in the image forming method of the present invention is carried out by using a laser scanning exposure machine which emits scanning laser light having a longitudinal multi-direction. Image quality deterioration such as occurrence of interference fringe-like unevenness is reduced as compared with the vertical single mode scanning laser light.

In order to make the vertical multi, it is preferable to use return light by multiplexing, high frequency superposition, or the like. still,
The vertical multi means that the exposure wavelength is not single, and normally the distribution of the exposure wavelength is 5 nm or more, preferably 10 nm or more. The upper limit of the distribution of exposure wavelength is not particularly limited, but is usually about 60 nm.

Although the photothermographic material is stable at room temperature, it is developed by heating to high temperature after exposure. The heating temperature is preferably 80 to 200 ° C., more preferably 10
It is 0 to 150 ° C. If the heating temperature is less than 80 ° C, a sufficient image density cannot be obtained in a short time, and if the heating temperature exceeds 200 ° C, the binder is melted and the toner is transferred to a roller or the like, and not only the image itself but also the transportability and the developing machine are used. Also has an adverse effect.

By heating, a silver image is produced by a redox reaction between an organic silver salt (which functions as an oxidizing agent) and a reducing agent. This reaction process proceeds without supplying a treatment liquid such as water from the outside. As an apparatus for developing a photothermographic material, JP-A-11-65067 and JP-A-11-7289 are available.
The devices described in No. 7 and No. 11-84619 can be used.

[0068]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise specified
“%” In the examples represents “mass%”.

Example 1 <Preparation of backing layer> Concentration 0.170 (manufactured by Konica Corporation:
175 μm thick polyethylene terephthalate (PET) colored blue with a densitometer PDA-65)
Both sides of the film were subjected to a corona discharge treatment of 8 W / m ² · min, and the backing layer coating solution prepared as described below was applied to one side thereof by an extrusion coater so that the dry film thickness was 3.5 μm, The backing layer was applied by drying for 5 minutes using a drying air having a drying temperature of 100 ° C and a dew point temperature of 10 ° C.

(Preparation of coating solution for backing layer) Cellulose acetate butyrate (Eastman Chemical Co., Ltd.) was added to 830 g of methyl ethyl ketone with stirring.
CAB381-20) 84.2 g, polyester resin (Bostic: VitelPE2200B) 4.5
g was added and dissolved. An infrared dye (IR-
1) 3.5 g of a fluorine-containing surfactant dissolved in 43.2 g of methanol (Asahi Glass Co., Ltd .: Surflon KH4)
0) 4.5 g and a fluorinated surfactant (Dainippon Ink and
2.3 g of Megafac F120K) was added, and the mixture was sufficiently stirred until it was dissolved. Finally, silica dispersed in methyl ethyl ketone at a concentration of 1% by a dissolver type homogenizer (WR Grace Co., Ltd .: Syloid 64 × 600).
0) of 75 g was added and stirred to prepare a backing layer coating liquid.

<Preparation of Photosensitive Layer> (Preparation of Silver Halide Emulsion) Silver halide emulsion 1 was prepared using each solution having the following composition. Solution (A1) Phenylcarbamoyl gelatin 88.3 g 10% methanol solution of surfactant A 10 ml Potassium bromide 0.32 g Solution (B1) 0.67 mol / L silver nitrate aqueous solution 2635 ml Solution (C1) potassium bromide 51.55 g Potassium iodide 1.47 g Solution (D1) which is made up to 660 ml with water Potassium bromide 154.9 g Potassium iodide 4.41 g Iridium chloride (1% solution) 0.93 ml Solution (E1) 0.4 mol / L Potassium bromide aqueous solution Silver potential control amount solution (F1) 56% acetic acid aqueous solution 16.0 ml solution (G1) anhydrous sodium carbonate 1.72 g Finish with water to 151 ml A: HO (CH ₂ CH ₂ O) _n [CH (CH ₃ ) CH ₂ O] ₁₇ (CH ₂ CH ₂ O) _m H [m + n = 5 to 7] Japanese Patent Publication Sho 5 Using the mixing stirrer described in JP-A No. 8-58288 or JP-A-58-58289, the solution (A1) was mixed with 1/4 amount of the solution (B1) and the total amount of the solution (C1) at 45 ° C. and pAg 8.0.
While controlling at 9, the mixture was added for 4 minutes and 45 seconds by the simultaneous mixing method to perform nucleation. After 7 minutes, the solution (B
The rest of 1) and the total amount of the solution (D1) were heated at a temperature of 45 ° C., p
While controlling to Ag 8.09, it was added over 14 minutes and 15 seconds by the double-blending method. During the mixing, the pH of the reaction solution was 5.
It was 6.

After stirring for 5 minutes, the temperature was lowered to 40 ° C., the whole amount of the solution (F1) was added, and the silver halide emulsion was precipitated. The supernatant was removed, leaving 2000 ml of the sedimented portion, 10 L of water was added and the mixture was stirred, and then the silver halide was precipitated again. The supernatant was removed, leaving 1500 ml of the sedimented portion, 10 L of water was further added, and the mixture was stirred and then the silver halide was precipitated. After removing the supernatant liquid leaving 1500 ml of the sedimented portion, the solution (G1) was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount was 1161 g per mol of silver, whereby Silver Halide Emulsion 1 was prepared. This emulsion is
The cubic silver iodobromide grains had an average grain size of 0.058 μm, a grain size variation coefficient of 12%, and a [100] plane ratio of 92%.

(Preparation of powdered organic silver salt) In 4720 ml of pure water, behenic acid 111.4 g and arachidic acid 83.8.
g, and 54.9 g of stearic acid were dissolved at 80 ° C. Next, 540.2 ml of 1.5 mol / L sodium hydroxide aqueous solution was added while stirring at high speed, 6.9 ml of concentrated nitric acid was added, and then the mixture was cooled to 55 ° C. to obtain an organic acid sodium salt solution.

With the sodium fatty acid solution kept at 55 ° C., potassium bromide was added to the silver halide emulsion 1 and 450 ml of pure water, and the mixture was stirred for 5 minutes.

Next, a 1 mol / L silver nitrate aqueous solution 76
0.6 ml was added over 2 minutes and stirred for another 20 minutes,
Water-soluble salts were removed by filtration. Then, washing with deionized water until the conductivity of the filtrate reaches 20 μS / cm,
Filtration was repeated, centrifugal dehydration was carried out, and then hot air drying was carried out at 37 ° C. until there was no loss of mass to obtain a powdered organic silver salt.

(Preparation of Preliminary Dispersion) Polyvinyl butyral powder (Monsanto: Butvar B-7)
9) 14.57 g of MEK (methyl ethyl ketone) 14
A preliminary dispersion was prepared by dissolving in 57 g, and gradually adding 500 g of the above powdered organic silver salt and sufficiently mixing while stirring with a dissolver DISPERMAT CA-40M type manufactured by VMA-GETZMANN.

(Preparation of Photosensitive Emulsion Dispersion) Using a GM-2 type pressure homogenizer (manufactured by SMT), each preliminary dispersion was dispersed for 2 passes to prepare a photosensitive emulsion dispersion. At this time, the processing pressure during one pass is 27.4.
6 MPa, processing pressure during 2 passes is 54.92 MPa
And

Next, the following additive liquids necessary for preparing the photosensitive layer coating liquid were prepared. (Stabilizer liquid) Stabilizer-1 1.00 g Potassium acetate 0.31 g Methanol 10 g (Infrared sensitizing dye liquid) Infrared sensitizing dye-1 41.0 mg 2-Chloro-benzoic acid 2.0 g Compound A 21. 0 g Methyl ethyl ketone 100 g (Additive liquid A) 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane 51.0 g 4-methylphthalic acid 3.40 g Infrared dye-10 .22 g Methyl ethyl ketone 170 g (Preparation of photosensitive layer coating solution) 100 g of the photosensitive emulsion dispersion
And 45 g of MEK were kept at 25 ° C. with stirring, 0.65 g of a 10% methanol solution of antifoggant-1 was added, and the mixture was stirred for 1 hour. Further, 0.84 g of a 10% methanol solution of calcium bromide was added and stirred for 20 minutes. Subsequently, 0.70 g of the stabilizer solution was added and stirred for 10 minutes, and then 7.90 g of the infrared sensitizing dye solution was added and stirred for 1 hour.

Further, 1.50 g of a 1% methanol solution of supersensitizer-1 was added and stirred for 30 minutes, then cooled to 13 ° C. and further stirred for 30 minutes. While keeping the temperature at 13 ℃,
Polyvinyl butyral (Previous: Butvar B-7
15 minutes after 26 g of 9) was added, 2.3 g of a 13% MEK solution of tetrachlorophthalic acid was added. While further stirring, the isocyanate compound (IC-10) 22
% MEK solution 4.5 g, additive solution A 27.0 g, polyhalomethane compound (HL-3) 6.5% MEK solution 6.0 g, phthalazine 7% MEK solution 9.0 g, p
5 g of a 0.5% MEK solution of potassium toluenethiosulfonate and 3.0% of the liquid crystal compounds of the present invention shown in Table 1.
g, successively added and stirred to obtain a photosensitive layer coating solution.

<Preparation of Protective Layer Coating Liquid> While stirring 865 g of MEK, cellulose acetate butyrate (Ea
stman Chemical Company: CAB171-15)
96 g, polymethylmethacrylic acid (Rohm & Haas Company:
Paraloid A-21) 4.5 g, vinyl sulfone compound (VS-1) 1.5 g, benzotriazole 1.0 g,
Fluorine activator (Asahi Glass Co., Ltd .: Surflon KH40) 1.0
g was added and dissolved. Next, 30 g of the matting agent dispersion liquid shown below was added and stirred to prepare a protective layer coating liquid.

The structures of the additives used in each coating solution are shown below.

[0082]

[Chemical 3]

[0083]

[Chemical 4]

VS-1: (CH ₂ = CHSO ₂ CH ₂ ) ₂ CHOH <Preparation of Matting Agent Dispersion Liquid> Cellulose acetate butyrate (previously: CAB171-15) 7.5 g was added to MEK4.
It dissolves in 2.5 g, and calcium carbonate (Spe
ciality Minerals: Super-Pf
5 g of lex200) was added and dispersed with a dissolver type homogenizer at 8000 rpm for 30 minutes to prepare a matting agent dispersion liquid.

<Preparation of Photothermographic Material> The photosensitive layer coating solution and the protective layer coating solution were simultaneously coated in multiple layers using an extrusion coater. For the coating, the photosensitive layer has a coated silver amount of 1.9 g /
m ² and the protective layer were adjusted so that the dry film thickness was 2.5 μm. Then, the photothermographic material 1 was prepared by drying for 10 minutes using a drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

Further, as shown in Table 1, heat-developable photosensitive materials 2 to 5 (5 is a comparative example in which the liquid crystal compound is not added) are prepared in the same manner as in the photosensitive material 1 except that the liquid crystal compound of the present invention is replaced. .

The photothermographic materials 1 to 5 were exposed and developed as described below, and the relative sensitivity, fog, fog change and color tone change were evaluated according to the following evaluation criteria.

<Exposure and development processing> From the photosensitive layer surface side of the photothermographic material, a wavelength of 800 to 820 nm is superimposed by high frequency.
Exposure by laser scanning was performed by an exposure device using a semiconductor laser in which the vertical multimode was produced as a light emitting source. On this occasion,
An image was formed by setting the angle between the exposed surface of the photothermographic material and the exposure laser beam at 75 degrees.

Then, using an automatic developing machine having a heat drum, a heat development treatment was carried out at 120 ° C. for 15 seconds so that the protective layer of the photothermographic material was in contact with the drum surface.

<< Relative Sensitivity, Fog >> The transmission density of the obtained image was measured and the relative sensitivity (sensitivity was determined by the reciprocal of the exposure amount required to give a density 1.0 higher than the fog portion) to obtain a photothermographic material. (Relative value where sensitivity of 5 is 1.50) and fog were evaluated.

<< Fog Variation and Color Tone Variation >> After exposing and developing the photothermographic material on a light source stand (fluorescent lamp light, surface temperature about 45 ° C.) with an illuminance of 10000 lux, 20
The fog density after the lapse of time was measured. Also, transmission density 1.1 ±
With respect to the 0.05 part, the color tone of silver was evaluated on a scale of 5 according to the following criteria. If it is 3 or more, there is no problem in practical skill.

[0092] 5: Pure black tone with no yellow tint 4: It is not pure black, but almost no yellow color is felt 3: Partially slightly yellowish 2: A slight yellow color is felt on the entire surface 1: At first glance, you can feel yellow color The results are also shown in Table 1.

[0093]

[Table 1]

From Table 1, it is confirmed that the sample of the present invention has higher relative sensitivity and lower fog than the comparative sample, and the stable color tone can be obtained with less fogging change and color tone change after heat development. Was done.

[0095]

INDUSTRIAL APPLICABILITY According to the present invention, a photothermographic material having high relative sensitivity and low fog, and having no fog density fluctuation or color tone fluctuation after exposure to room light after development, and the photosensitive material. It was possible to provide an image forming method using.

Claims (4)

[Claims] 1. A photothermographic material comprising a support and a photosensitive layer containing at least an organic silver salt, a silver halide, a reducing agent and a thermotropic liquid crystal. 2. The photothermographic material according to claim 1, wherein the transition temperature of the thermotropic liquid crystal from the solid state to the liquid crystal state is 50 to 150 ° C. 3. The transition temperature from the solid state to the liquid crystal state of the thermotropic liquid crystal is 50 ° C. or higher, and the transition temperature from the liquid crystal state to the isotropic liquid is 150 ° C. or lower. 1. The photothermographic material according to 1. 4. An image forming method, which comprises subjecting the photothermographic material according to claim 1 to laser exposure to heat and development.