JP2000171936A - Heat developable material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat developable material, in particular a heat developable photosensitive material which prevents cracking in heat development. SOLUTION: Polyvinyl alcohol is incorporated into the top layer (image recording layer side) of a heat developable material with an image recording layer (in particular a photosensitive layer) formed by aqueous coating and containing a polymer having <=2 wt.% equilibrium water content at 25 deg.C and 60% RH as the principal binder. The image recording layer is preferably a photosensitive layer containing at least photosensitive silver halide grains and a binder. The heat developable material is preferably heat-developed at >=100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-developable material, and more particularly to a heat-developable light-sensitive material (hereinafter sometimes referred to as a heat-developable light-sensitive material). It relates to a developed photosensitive material.

[0002]

2. Description of the Related Art Photothermographic materials have been proposed for a long time, and are described, for example, in US Pat. Nos. 3,152,904 and 345.
No. 7075 and each of B.I. "Thermal Proceed Silver System" by Shely
ssed Silver Systems) "(Imaging Processes and Mats
erials) Neblette 8th edition, edited by Sturge, V. Walworth, A. Shepp, 2nd edition
, 1996). The photothermographic material generally comprises a catalytically active amount of a photocatalyst (eg, silver halide), a reducing agent, a reducible silver salt (eg, an organic silver salt), and if necessary, a color tone controlling agent for controlling the color tone of silver. Having a photosensitive layer dispersed in a matrix. After the image exposure, the photothermographic material is heated to a high temperature (for example, 80 ° C. or higher), and is subjected to an oxidation-reduction reaction between silver halide or a reducible silver salt (which functions as an oxidizing agent) and the reducing agent,
A black silver image is formed. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure.
Therefore, a black silver image is formed in the exposed area.

Conventionally, an organic solvent-based photosensitive layer using polyvinyl butyral (PVB) as a binder has been used as a photothermographic material. However, from the viewpoint of solution preparation / coating work and equipment, coating with an aqueous solvent is used. It has been desired to do so. To address such problems, European Patent Publication No. (EP) 8037
Japanese Patent No. 64A1, for example, proposed a method of applying a photosensitive layer by dispersing a hydrophobic polymer in water. However,
It was found that when a protective layer using gelatin was used on such a water-based coated photosensitive layer, cracks were generated during thermal development. This cracking problem is a problem that does not occur even if a protective layer such as gelatin or cellulose is provided on the photosensitive layer coated with PVB in an organic solvent system. The photosensitive layer is formed by dispersing a hydrophobic polymer in water. This is a new problem that occurs when coating is performed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent a heat-developable material, especially a heat-developable photosensitive material, from cracking during heat development.

[0005]

This object has been achieved by the following means. (1) In a heat-developable material having a constituent layer including at least one image-recording layer on a support, the image-recording layer is formed by applying a coating solution in which 30% by weight or more of a solvent is water and drying. And the main binder of the image recording layer is 25 ° C.
A heat-developable material comprising a polymer having an equilibrium water content of 60% RH and an equilibrium water content of 2% by weight or less, wherein the outermost layer on the image recording layer side of the constituent layers contains polyvinyl alcohol. (2) The heat-developable material according to the above (1), wherein the image recording layer is a photosensitive layer containing at least photosensitive silver halide particles and a binder. (3) The heat-developable material according to the above (1) or (2), further comprising a layer containing polyvinyl alcohol on a side of the support opposite to the image recording layer. (4) The above (1) to (1) to heat development at a temperature of 100 ° C or higher
The heat-developable material according to any one of (3). (5) the support has at least two constituent layers including the image recording layer on the same side as the image recording layer;
The heat developing material according to any one of (1) to (4), wherein the at least two constituent layers are simultaneously coated. (6) The heat developing material according to any one of (1) to (5), wherein the image recording layer further contains an organic silver salt and a reducing agent for silver ions. (7) The heat developing material according to any one of (1) to (6), wherein the outermost surface layer further contains boric acid.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The photothermographic material of the present invention has a constituent layer including at least one image recording layer on a support, and preferably has a photothermographic material having a photosensitive layer containing a photosensitive silver halide and a binder. Material. Most preferably, the photosensitive layer has a photosensitive layer as an image recording layer. In this case, the photosensitive layer preferably contains a photosensitive silver halide, an organic silver salt, and a reducing agent for silver ions. In such a heat-developable material, the image-recording layer, particularly preferably the photosensitive layer, can be aqueous-coated using a coating solution in which 30% by weight of an environmentally preferable solvent is water, and is good. A polymer having an equilibrium water content of 2% by weight or less at 25 ° C. and 60% RH which is preferable for obtaining excellent photographic performance is used as a main binder. In the present invention, the outermost layer on the image recording layer (particularly, the photosensitive layer) side is formed of polyvinyl alcohol (P
VA), whereby cracks can be prevented during thermal development, particularly during thermal development at a temperature of 100 ° C. or higher. In addition, the polyvinyl alcohol-containing layer can be applied in an aqueous manner, and can be simultaneously coated with an image recording layer, a protective layer using a hydrophilic binder other than the polyvinyl alcohol-containing outermost layer, and an intermediate layer. Above.

The heat-developable material of the present invention is preferably a single-sided type having an image recording layer on only one surface of a support. In such a type of heat-developable material, a layer containing polyvinyl alcohol is preferably used. Is preferably provided on the back surface opposite to the image recording layer with respect to the support, so that the flatness of the sheet is maintained.

As the polyvinyl alcohol (PVA) used in the outermost layer of the present invention, there are the following compounds.

As the completely saponified product, PVA-105 is used.
[Polyvinyl alcohol (PVA) content 94.0 wt%
Above, saponification degree 98.5 ± 0.5 mol%, sodium acetate content 1.5 wt% or less, volatile matter 5.0 wt% or less, viscosity (4 wt%, 20 ° C.) 5.6 ± 0.4 CPS], PVA −
110 [PVA content 94.0 wt%, saponification degree 98.5
± 0.5 mol%, sodium acetate content 1.5 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 11.0 ±
0.8 CPS], PVA-117 [PVA content 94.
0 wt%, saponification degree 98.5 ± 0.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%
%, 20 ° C.) 28.0 ± 3.0 CPS],

[0010] PVA-117H [PVA content 93.5
wt%, saponification degree 99.6 ± 0.3 mol%, sodium acetate content 1.85 wt%, volatile matter 5.0 wt%, viscosity (4 wt%
%, 20 ° C.) 29.0 ± 3.0 CPS], PVA-12
0 [PVA content 94.0 wt%, saponification degree 98.5 ±
0.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 39.5 ± 4.
5CPS], PVA-124 [PVA content 94.0 wt.
%, Saponification degree 98.5 ± 0.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%,
20 ° C.) 60.0 ± 6.0 CPS],

[0011] PVA-124H [PVA content 93.5
wt%, saponification degree 99.6 ± 0.3 mol%, sodium acetate content 1.85 wt%, volatile matter 5.0 wt%, viscosity (4 wt%
%, 20 ° C.) 61.0 ± 6.0 CPS], PVA-CS
[PVA content 94.0 wt%, degree of saponification 97.5 ± 0.
5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 27.5 ± 3.0
CPS], PVA-CST [PVA content 94.0 wt%
, Saponification degree 96.0 ± 0.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%,
20 ° C.) 27.0 ± 3.0 CPS], PVA-HC [P
VA content 90.0 wt%, saponification degree 99.85 mol% or more, sodium acetate content 2.5 wt%, volatile matter 8.5 wt
%, Viscosity (4 wt%, 20 ° C.) 25.0 ± 3.5 CPS]
(These are all trade names made by Kuraray Co., Ltd.)

As the partially saponified product, PVA-203 is used.
[PVA content 94.0 wt%, saponification degree 88.0 ± 1.
5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 3.4 ± 0.2 C
PS], PVA-204 [PVA content 94.0 wt%,
Degree of saponification 88.0 ± 1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 wt%)
C) 3.9 ± 0.3 CPS], PVA-205 [PVA
94.0 wt%, saponification degree 88.0 ± 1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%
%, Viscosity (4 wt%, 20 ° C.) 5.0 ± 0.4 CPS],

PVA-210 [PVA content 94.0 wt.
%, Saponification degree 88.0 ± 1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%,
20 ° C) 9.0 ± 1.0 CPS], PVA-217 [P
VA content 94.0 wt%, degree of saponification 88.0 ± 1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0
wt%, viscosity (4wt%, 20 ° C) 22.5 ± 2.0CP
S], PVA-220 [PVA content 94.0 wt%, degree of saponification 88.0 ± 1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20
° C) 30.0 ± 3.0 CPS],

PVA-224 [PVA content 94.0 wt.
%, Saponification degree 88.0 ± 1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%,
20 ° C.) 44.0 ± 4.0 CPS], PVA-228
[PVA content 94.0 wt%, saponification degree 88.0 ± 1.
5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 65.0 ± 5.0
CPS], PVA-235 [PVA content 94.0 wt%
, Saponification degree 88.0 ± 1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%,
20 ° C) 95.0 ± 15.0 CPS],

PVA-217EE [PVA content 94.
0 wt%, saponification degree 88.0 ± 1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%
%, 20 ° C.) 23.0 ± 3.0 CPS], PVA-21
7E [PVA content 94.0 wt%, saponification degree 88.0 ±
1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 23.0 ± 3.0.
0CPS], PVA-220E [PVA content 94.0
wt%, saponification degree 88.0 ± 1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%
, 20 ° C) 31.0 ± 4.0 CPS],

PVA-224E [PVA content 94.0
wt%, saponification degree 88.0 ± 1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%
, 20 ° C) 45.0 ± 5.0 CPS], PVA-40
3 [PVA content 94.0 wt%, saponification degree 80.0 ±
1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 3.1 ± 0.3
CPS], PVA-405 [PVA content 94.0 wt%
, Saponification degree 81.5 ± 1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%,
20 ° C.) 4.8 ± 0.4 CPS],

PVA-420 [PVA content 94.0 wt.
%, Saponification degree 79.5 ± 1.5 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%], PVA-61
3 [PVA content 94.0 wt%, saponification degree 93.5 ±
1.0 mol%, sodium acetate content 1.0 wt%, volatile matter 5.0 wt%, viscosity (4 wt%, 20 ° C.) 16.5 ± 2.
0CPS], L-8 [PVA content 96.0 wt%, saponification degree 71.0 ± 1.5 mol%, sodium acetate content 1.0 wt% (ash), volatile matter 3.0 wt%, viscosity (4 wt%)
, 20 ° C.) 5.4 ± 0.4 CPS] (all of which are trade names manufactured by Kuraray Co., Ltd.).

The above measured values are based on JIS K-6726.
It was determined according to -1977.

As the modified polyvinyl alcohol, those described in “Poval”, published by Koichi Nagano et al., Published by Kobunshi Kanko-kai are used. Cation, anion, -SH compound,
Modification by alkylthio compounds and silanols.

Examples of such modified polyvinyl alcohol (modified PVA) include C-118 and C-
-318, C-318-2A, C-506 (all of which are trade names manufactured by Kuraray Co., Ltd.), H as an HL polymer
L-12E, HL-1203 (all of which are trade names manufactured by Kuraray Co., Ltd.), HM-03 as HM polymer,
HM-N-03 (all of which are trade names manufactured by Kuraray Co., Ltd.), KL-118 and KL-318 as K polymers,
KL-506, KM-118T, KM-618 (above,
All are Kuraray's trade names, M-polymer is M-115 (Kuraray's trade name), and MP polymers are MP-102, MP-202, MP-203 (all of which are Kuraray ( Co., Ltd.), R-1130, R-2105, and R-2130 as R polymers (all of which are trade names manufactured by Kuraray Co., Ltd.), and V-2250 (manufactured by Kuraray Co., Ltd.) as V polymer. Product name).

The amount of polyvinyl alcohol applied to the outermost surface layer containing polyvinyl alcohol (per 1 m ^{2 of} support)
Preferably 0.3g / m ² ~4.0g / m ² as, 0.3 g /
m ^{2 to} 2.0 g / m ² is more preferred. In addition, the amount of application (per layer) when polyvinyl alcohol is added to the layer on the back surface and the like is almost the same.

When the outermost surface layer containing polyvinyl alcohol is applied, boric acid as a thickener is contained in the coating solution, so that the quality of the coated surface can be improved, which is preferable. The amount of boric acid added is preferably 0.01 to 40% by weight based on polyvinyl alcohol.

In the present invention, the outermost surface layer may contain a matting agent, and the preferably used matting agent is generally fine particles of an organic or inorganic compound insoluble in water. Any matting agent can be used, for example, U.S. Patent Nos. 1,939,213, 2,701,245, 2,322,037, and
Organic matting agents described in the specifications such as 3,262,782, 3,539,344, 3,767,448, etc .; 1,260,772, 2,19
Nos. 2,241, 3,257,206, 3,370,951, 3,523,
Inorganic matting agents well-known in the art, such as inorganic matting agents described in the respective specifications such as Nos. 022 and 3,769,020 can be used. For example, specifically, examples of organic compounds that can be used as a matting agent include polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, and acrylonitrile-α- as examples of water-dispersible vinyl polymers.
Methylstyrene copolymer, polystyrene, styrene-divinylbenzene copolymer, polyvinyl acetate, polyethylene carbonate, polytetrafluoroethylene, etc., as examples of cellulose derivatives, methylcellulose,
Examples of starch derivatives such as cellulose acetate and cellulose acetate propionate, carboxy starch, carboxynitrophenyl starch, urea-formaldehyde-starch reactant, etc. Hardened gelatin or the like can be preferably used. As examples of the inorganic compound, silicon dioxide, titanium dioxide, magnesium dioxide, aluminum oxide, barium sulfate, calcium carbonate, silver chloride desensitized by a known method, silver bromide, glass, and diatomaceous earth can be preferably used. The above matting agents can be used by mixing different types of substances as necessary.

In practicing the present invention, it is more preferable to use one having an average particle size of 2 μm to 6 μm. Further, the particle size distribution of the matting agent may be narrow or wide. On the other hand, since the matting agent greatly affects the haze and surface gloss of the light-sensitive material, the particle size, shape, and particle size distribution can be changed as necessary during the preparation of the matting agent or by mixing a plurality of matting agents. preferable.

The particle size of the matting agent in the present invention is determined by using an electron microscope to obtain a circle-equivalent diameter from the projected area.
The average value is defined as the particle size.

The coating amount of the matting agent, 1 to 400 mg / m ^2, more preferably from 5 to 300 mg / m ^2, in particular, it is preferable to 4μm or more of the particles is 5 to 150 mg / m ^2.

As the layer containing a matting agent on the surface of the image recording layer or the photosensitive layer, a protective layer is most suitable. The protective layer can be made into two layers as needed, and is an additive layer to which additives related to development, a film surface pH adjuster, a charge adjuster, an ultraviolet absorber, a slipping agent, a surfactant and the like are added. By selecting, it is possible to design such that the applicability, the suitability for production and the image quality performance are compatible. The outermost protective layer preferably contains a fluorine-based surfactant together with the matting agent. Specifically, as a fluorine-based surfactant,
No.-170950, U.S. Pat.No.5,380,644, fluorine polymer surfactants described in JP-A-60-244945, JP-A-63-1
And the fluorine-based surfactants described in JP-A-88135.

In the present invention, the outermost protective layer preferably contains a matting agent.

The matting agent can also be added to the back layer. In this case, it is preferable that the matting agent is not the outermost layer on the back surface side.

A hardener may be used for each layer such as the image recording layer (preferably the photosensitive layer), the protective layer and the back layer of the present invention. "THE THEORY OF" by THJames as an example of hardener
THE PHOTOGRAPHIC PROCESS FOURTH EDITION ”(Macmil
lan Publishing Co., Inc., 1977) 77-8
There are various methods described on page 7, polyvalent metal ions described on page 78 of the same book, US Pat. No. 4,281,060, JP-A-6-208193.
No. 4,791,042
And epoxy compounds such as JP-A No. 62-89048.

As the surface protective layer of the present invention, any anti-adhesion material may be used. Examples of anti-adhesion materials include waxes, silica particles, styrene-containing elastomeric block copolymers (e.g., styrene-butadiene-
Styrene, styrene-isoprene-styrene), cellulose acetate, cellulose acetate butyrate, cellulose propionate, and mixtures thereof. Further, a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like may be added to the surface protective layer.

In the image recording layer or the protective layer of the image recording layer in the present invention, US Pat. Nos. 3,253,921 and 2,27
Light absorbing substances and filter dyes as described in 4,782, 2,527,583 and 2,956,879 can be used. Also, for example, U.S. Pat.
The dye can be mordanted as described in US Pat.

The image-recording layer or the protective layer of the image-recording layer in the present invention may comprise a matting agent such as starch, titanium dioxide, zinc oxide, silica, of the type described in US Pat. Nos. 2,992,101 and 2,701,245. Polymer beads, including beads, can be included. The matte degree of the emulsion surface may be any value as long as stardust failure does not occur, but the Beck smoothness is preferably from 200 seconds to 10,000 seconds, particularly preferably from 300 seconds to 10,000 seconds.

Hereinafter, the photothermographic material will be further described. The photothermographic material is preferably a mono-sheet type (a type capable of forming an image on the photothermographic material without using another sheet such as an image receiving material). The present invention
It is particularly effective in a photothermographic material for red to infrared exposure.

The photothermographic material has a photosensitive layer containing a photosensitive silver halide (a catalytically active amount of a photocatalyst) and a reducing agent, and a non-photosensitive layer. The photosensitive layer further comprises a binder (generally a synthetic polymer), an organic silver salt (a reducible silver source).
It contains. Further, it is preferable to include a hydrazine compound (a super-high contrast agent) and a color tone adjuster (which controls the color tone of silver). A plurality of photosensitive layers may be provided. For example, a high-sensitivity photosensitive layer and a low-sensitivity photosensitive layer can be provided on a photothermographic material for the purpose of adjusting the gradation. The order of arrangement of the high-sensitivity photosensitive layer and the low-sensitivity photosensitive layer may be such that the low-sensitivity photosensitive layer is disposed below (the support side) or the high-sensitivity photosensitive layer is disposed below.

The non-photosensitive layer may be provided as another functional layer such as a surface protective layer in addition to the dye-containing layer, that is, the filter layer and the antihalation layer.

As the support of the photothermographic material, paper, polyethylene-coated paper, polypropylene-coated paper, parchment, cloth, metal (eg, aluminum, copper, magnesium, zinc) sheet or thin film, glass, Glass and plastic films coated with a metal (eg, chromium alloy, steel, silver, gold, platinum) are used. Preferably, the transparent plastic film is an example of a plastic used for the support, such as polyalkyl methacrylate (eg, polymethyl methacrylate), polyester (eg, polyethylene terephthalate: PET), polyvinyl acetal, polyamide (eg, nylon) and Cellulose esters (eg, cellulose nitrate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate) are included. The support preferably has a thickness of 90 to 190 µm, more preferably 150 to 185 µm.

[0038] The support may be coated with a polymer. Examples of the polymer include polyvinylidene chloride, an acrylic acid-based polymer (eg, polyacrylonitrile, methyl acrylate), a polymer of unsaturated dicarboxylic acid (eg, itaconic acid, acrylic acid), carboxymethylcellulose, and polyacrylamide. Copolymers may be used. Instead of coating with a polymer, an undercoat layer containing a polymer may be provided.

As silver halide, any of silver bromide, silver iodide, silver chloride, silver chlorobromide, silver iodobromide and silver chloroiodobromide can be used. The distribution of the halogen composition in the grains may be uniform, the halogen composition may change stepwise, or may change continuously. Further, silver halide grains having a core / shell structure can be preferably used. The preferred structure is a two- to five-layer structure, and more preferably a core / shell particle having a two- to four-layer structure can be used. A technique for localizing silver bromide on the surface of silver chloride or silver chlorobromide grains can also be preferably used.

The grain size of the silver halide grains is 0.00
1 μm or more and 0.04 μm or less, preferably 0.0
It is not less than 05 μm and not more than 0.04 μm. The grain size of the silver halide grains in the present invention is determined by using an electron microscope, calculating the equivalent circle diameter from the projected area, and averaging the values.

The addition amount of the silver halide, when expressed by the coating amount per photographic material 1 m ^2, is preferably 0.03~0.6g / m ^2, at 0.05 to 0.4 g / m ² More preferably, it is most preferably 0.1 to 0.4 g / m ² .

Methods for forming photosensitive silver halide are well known in the art, for example, Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,45.
The method described in No. 8 can be used. Specifically, silver halide is prepared as a silver halide emulsion by reacting silver nitrate with a soluble halide salt. In addition,
It may be prepared by reacting silver soap with halogen ions and converting the soap portion of silver soap into halogen. Further, halogen ions may be added during the formation of the silver soap.

Silver halide is generally used after spectral sensitization. Regarding spectral sensitizing dyes, see JP-A-60-1403.
No. 35, No. 63-159,841 and No. 63-23143
No. 7, 63-259,651 and 63-304242
Nos. 63-15245 and U.S. Pat.
Nos. 414, 474,455 and 474,966,
Nos. 4,751,175 and 4,835,096.

As the reducing agent preferably used in the present invention, phenidone, hydroquinones, catechol and hindered phenol are preferable. As for the reducing agent, US Pat. Nos. 3,770,448 and 3,773,512;
Nos. 3,593,863 and 4,460,681,
And Research Discl
osure) magazines 17029 and 29963.

Examples of the reducing agent include aminohydroxycycloalkenones (eg, 2-hydroxy-piperidino-
2-cyclohexenone), N-hydroxyurea derivatives (eg, Np-methylphenyl-N-hydroxyurea), aldehydes or ketone hydrazones (eg, anthracenaldehyde phenylhydrazone), phosphoramidophenols, phosphates Amidoanilines,
Polyhydroxybenzenes (eg, hydroquinone, t-butyl-hydroquinone, isopropylhydroquinone, 2,
5-dihydroxy-phenylmethylsulfone), sulfohydroxamic acids (eg, benzenesulfohydroxamic acid), sulfonamidoanilines (eg, 4- (N-methanesulfonamido) aniline), 2-tetrazolylthiohydroquinones (eg, 2-methyl-5- (1-phenyl-5-tetrazolylthio) hydroquinone), tetrahydroquinoxalines (eg, 1,2,3,4-tetrahydroquinoxaline), amidooxines, azines (eg, aryl aryl carboxylate) Hydrazides) and ascorbic acid, polyhydroxybenzene and hydroxylamine, reductone, hydrazine, hydroxamic acids, azines and sulfonamidephenols, α-cyanophenylacetic acid derivatives, bis-β- Naphtho , A combination of a 1,3-dihydroxybenzene derivative, 5-pyrazolones, sulfonamidophenols, and 2-phenylindane-1,3-
Dione, chroman, 1,4-dihydropyridines (eg,
2,6-dimethoxy-3,5-dicarbethoxy-1,
4-dihydropyridine), bisphenols (eg, bis (2-hydroxy-3-t-butyl-5-methylphenyl) methane, bis (6-hydroxy-m-tri) mesitol, 2,2-bis (4-hydroxy -3-methylphenyl) propane, 1,1-bis (2-hydroxy-3,
5-dimethylphenyl) -3,5,5-trimethylhexane, 4,4-ethylidene-bis (2-t-butyl-6
-Methyl) phenol), UV-sensitive ascorbic acid derivatives and 3-pyrazolidones.

Esters of aminoreductones (eg, piperidinohexose reductone monoacetate) which function as a precursor of the reducing agent may be used as the reducing agent.

Particularly preferred reducing agents are hindered phenols.

The amount of the reducing agent to be added is 0.01 to 5.0 g / m ^2.
And more preferably 0.1 to 3.0 g / m ² .

The photosensitive layer and the non-photosensitive layer preferably contain a binder. Generally, a colorless transparent or translucent polymer is used as the binder.

The effect of the present invention is that the photosensitive layer contains 30% by weight of the solvent.
When the composition is formed by coating and drying using a coating solution containing water as described above, the main binder of the photosensitive layer (70% by weight or more, preferably 80% by weight or more of all binders in the photosensitive layer) further contains an aqueous solvent ( (Water solvent), which can be dissolved or dispersed, especially when the polymer latex has an equilibrium water content at 25 ° C. and 60% RH of 2 wt% or less. The most preferred form is
It is prepared so as to have an ionic conductivity of 2.5 mS / cm or less. As such a preparation method, a method of purifying using a separation functional membrane after polymer synthesis can be mentioned.

The aqueous solvent in which the main binder of the photosensitive layer of the present invention (hereinafter sometimes referred to as the polymer of the present invention) is soluble or dispersible means water or 70% by weight of water.
It is a mixture of the following water-miscible organic solvents. Examples of water-miscible organic solvents include, for example, methyl alcohol,
Examples thereof include alcohols such as ethyl alcohol and propyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, ethyl acetate, and dimethylformamide.

The term "aqueous solvent" is used herein even in the case where the polymer is not thermodynamically dissolved but exists in a so-called dispersed state. The term “equilibrium moisture content at 25 ° C. and 60% RH” as used in the present invention refers to the weight W1 of a polymer that is in a moisture-conditioning equilibrium in an atmosphere of 25 ° C. and 60% RH and the weight W0 of a polymer that is in a dry state at 25 ° C. It can be expressed as follows. Equilibrium water content at 25 ° C and 60% RH = [(W1-W0) / W0] x 100
(wt%) The definition and measurement method of the water content can be referred to, for example, Polymer Engineering Course 14, Polymer Material Testing Method (edited by the Society of Polymer Science, Jinjinshokan).

The equilibrium water content of the polymer of the present invention at 25 ° C. and 60% RH is preferably 2% by weight or less, more preferably 0.01% by weight or more and 1.5% by weight or less, further preferably 0.02% by weight or less.
It is desirable that the content be not less than wt% and not more than 1 wt%.

The polymer of the present invention is soluble or dispersible in the above-mentioned aqueous solvent and has an equilibrium water content of 2w at 25 ° C. and 60% RH.
There is no particular limitation as long as it is less than t%. Among these polymers, polymers that can be dispersed in an aqueous solvent are particularly preferred.

Examples of the dispersion state include a latex in which fine particles of a solid polymer are dispersed and a dispersion in which polymer molecules are dispersed in a molecular state or in the form of micelles. In a preferred embodiment of the present invention, it is preferable to use a hydrophobic polymer such as an acrylic resin, a polyester resin, a rubber-based resin (for example, SBR resin), a polyurethane resin, a vinyl chloride resin, a vinyl acetate resin, a vinylidene chloride resin, and a polyolefin resin. it can. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized, or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is in the range of 5000 to 10000000, preferably 1000 in number average molecular weight.
0 to 200,000 is good. If the molecular weight is too small, the mechanical strength of the emulsion layer is insufficient, and if it is too large, the film-forming properties are poor, which is not preferable. The polymer of the present invention is a polymer in which these polymers are dispersed in an aqueous dispersion medium. Here, the aqueous system refers to a dispersion medium in which 30% by weight or more of the composition is water. Emulsified dispersion, micellar dispersion,
Further, any polymer may be used, such as a polymer having a hydrophilic portion in a molecule dispersed in a molecular state, and of these, latex is particularly preferable. Specific examples of preferred polymers include the following. In the following, it is expressed using the raw material monomer, and the value in parentheses is wt%
, Molecular weight is the number average molecular weight.

Latex of P-1; -MMA (70) -EA (27) -MAA (3)-(molecular weight 37000) P-2; -MMA (70) -2EHA (20) -St (5) -AA (5)-latex (molecular weight 40000) P-3; -St (50) -Bu (47) -MAA (3)-latex (molecular weight 4500)
0) Latex of P-4; -St (68) -Bu (29) -AA (3)-(molecular weight 6000
0) Latex of P-5; -St (70) -Bu (27) -IA (3)-(molecular weight 1200
00) Latex of P-6; -St (75) -Bu (24) -AA (1)-(molecular weight 1080
00) Latex of P-7; -St (60) -Bu (35) -DVB (3) -MAA (2)-(molecular weight 150,000) P-8; -St (70) -Bu (25) -DVB ( 2) -AA (3)-latex (molecular weight 280,000) P-9; -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-latex (molecular weight 80000) P-10; -VDC (85) -MMA (5) -EA (5) -MMA (5)-latex (molecular weight 67,000) P-11; -Et (90) -MAA (10)-latex (molecular weight) 12000) P-12; -St (70) -2EHA (27) -AA (3) latex (molecular weight 130
000) P-13; -MMA (63) -EA (35)-AA (2) latex (molecular weight 330
00)

Abbreviations of the above structures represent the following monomers.
MMA; methyl methacrylate, EA; ethyl acrylate, MAA; methacrylic acid, 2EHA; 2-ethylhexyl acrylate, St; styrene, Bu; butadiene, AA; acrylic acid, DVB; divinylbenzene, VC; vinyl chloride, AN;
Acrylonitrile, VDC; vinylidene chloride, Et; ethylene, IA; itaconic acid.

The polymers described above are also commercially available, and the following polymers can be used. Examples of the acrylic resin include Sebian A-4635,46583,4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821,
Examples of polyester resins such as 820, 857 (all manufactured by Zeon Corporation) include FINETEX ES650, 611, 675, 85
HYDRAN AP10, 20, 30, 40 (Dai Nippon Ink Chemical Co., Ltd.) is an example of polyurethane resin such as 0 (Dai Nippon Ink Chemical Co., Ltd.), WD-size, WMS (Eastman Chemical). For example, LA-based resin
CSTAR 7310K, 3307B, 4700H, 7132C (all manufactured by Dainippon Ink and Chemicals, Inc.), Nipol Lx416, 410, 438C, 2507
Examples of vinyl chloride resins include G351 and G576 (manufactured by Nippon Zeon). Examples of vinylidene chloride resins include L502 and L513 (manufactured by Asahi Kasei Corporation). Examples of olefin resins include Chemipearl S120 and SA100 (Mitsui Petrochemical Co., Ltd.)
Manufactured).

These polymers may be used alone as a polymer latex, or as a blend of two or more if necessary.

The polymer latex used in the present invention is particularly preferably a styrene-butadiene copolymer latex. The weight ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably from 40:60 to 95: 5. The ratio of the styrene monomer unit to the butadiene monomer unit in the copolymer is preferably 60 to 99% by weight. The preferred molecular weight range is the same as described above.

Styrene preferably used in the present invention
As the butadiene copolymer latex, the above-mentioned P-3
~ P-8, commercial products LACSTAR-3307B, 7132C, Nipol
Lx416, and the like.

The photosensitive layer of the light-sensitive material of the present invention may optionally contain a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, hydroxypropylcellulose and the like. The addition amount of these hydrophilic polymers is preferably 30% by weight or less, more preferably 20% by weight or less of the total binder in the photosensitive layer.

The photosensitive layer of the present invention is preferably formed by using a polymer latex. The amount of the binder in the photosensitive layer is such that the weight ratio of total binder / organic silver salt is 1/10.
To 10/1, and more preferably 1/5 to 4/1.

The weight ratio of total binder / silver halide is preferably in the range of 400-5, more preferably in the range of 200-10.

The total amount of the binder in the photosensitive layer of the present invention is 0.2
To 30 g / m ^2, more preferably in the range of 1 to 15 g / m ^2. The photosensitive layer of the present invention may contain a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like.

In the present invention, the solvent of the coating solution for the photosensitive layer of the photosensitive material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is an aqueous solvent containing 30% by weight or more of water.
As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, and ethyl acetate may be used. The water content of the solvent in the coating liquid is preferably at least 50 wt%, more preferably at least 70 wt%. Preferred examples of the solvent composition include water, water / methyl alcohol = 90/10, water / methyl alcohol = 70/30, water / methyl alcohol / dimethylformamide = 80/15/5, water / methyl alcohol / Ethyl cellosolve = 85/10/5, water / methyl alcohol / isopropyl alcohol = 85/10/5 (numerical values are wt%).

The photosensitive layer preferably further contains a non-photosensitive organic silver salt, and such an organic silver salt may be further contained in the non-photosensitive layer. The organic acid forming the silver salt is preferably a long-chain fatty acid. The number of carbon atoms in fatty acids is
It is preferably from 10 to 30, and more preferably from 15 to 25. An organic silver salt complex may be used. The ligand of the complex preferably has a total stability constant for silver ions in the range of 4.0 to 10.0. For organic silver salts, see Research Disclosure (Re
search Disclosure) No. 17029 and 29963
There is a description in the issue.

Examples of organic silver salts include silver salts of fatty acids (eg, gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, lauric acid), carboxyalkylthioureas (eg, 1- (3-carboxypropyl) ) Thiourea, 1-
Silver salt of (3-carboxypropyl) -3,3-dimethylthiourea), silver complex of polymer reaction product of aldehyde (eg, formaldehyde, acetaldehyde, butyraldehyde) and hydroxy-substituted aromatic carboxylic acid, aromatic carboxylic acid Silver salts of (e.g., salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid), thioenes (e.g., 3- (2-carboxyethyl)-
Silver salt or silver complex of 4-hydroxymethyl-4-thiazoline-2-thioene, 3-carboxymethyl-4-thiazoline-2-thioene), nitrogen acid (eg, imidazole, pyrazole, urazole, 1,2,4- Thiazole, 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole, benzotriazole)
Or silver complexes of saccharin, silver salts of 5-chlorosalicylaldoxime and silver salts of mercaptides. Silver behenate is most preferred. Organic silver salts
Is preferably used in 0.05 g / m ² or more 3 g / m ² or less as the amount of silver, and more preferably used in 0.3 g / m ² or more 2 g / m ² or less.

The photosensitive layer preferably further contains a super-high contrast agent, and the super-high contrast agent may be further contained in the non-photosensitive layer. When a photothermographic material is used in the field of photographic printing, it is important to reproduce a continuous tone image or a line image using halftone dots. By using a super-high contrast agent, the reproducibility of halftone images and line images can be improved. As the super-high contrast agent, a hydrazine compound, a quaternary ammonium compound or an acrylonitrile compound (described in US Pat. No. 5,545,515) is used. Hydrazine compounds are particularly preferred ultrahigh contrast agents.

The hydrazine compound is hydrazine (H ₂ N
—NH ₂ ) and a compound in which at least one of the hydrogen atoms has been substituted. As the substituent, an aliphatic group, an aromatic group or a heterocyclic group is directly bonded to a hydrazine nitrogen atom, or an aliphatic group, an aromatic group or a heterocyclic group is bonded to a hydrazine nitrogen atom via a linking group. . Examples of linking groups include -CO
-, - CS -, - SO 2 -, - POR- (R is an aliphatic group, an aromatic group or a heterocyclic group), - CNH- and combinations thereof.

The hydrazine compound is described in US Pat.
Nos. 464738, 5496695, 5551241
Nos. 1 and 5,536,622, JP-B-6-77
Nos. 138 and 6-93082, JP-A-6-23049
7, No. 6-289520, No. 6-313951,
No. 7-5610, No. 7-77783, No. 7-104
No. 426 is described in each publication.

The hydrazine compound can be dissolved in an appropriate organic solvent and added to the coating solution for the photosensitive layer. Examples of organic solvents include alcohols (eg, methanol, ethanol, propanol, fluorinated alcohols), ketones (eg, acetone, methyl ethyl ketone), dimethylformamide, dimethyl sulfoxide, and methyl cellosolve. In addition, hydrazine compound is oily (auxiliary)
A solution dissolved in a solvent may be emulsified in a coating solution. Examples of oily (auxiliary) solvents include dibutyl phthalate, tricresyl phosphate, glyceryl triacetate, diethyl phthalate, ethyl acetate and cyclohexanone. Further, a solid dispersion of a hydrazine compound may be added to the coating solution. The dispersion of the hydrazine compound is
It can be carried out using a known dispersing machine such as a ball mill, a colloid mill, a Menton-Gauling, a microfluidizer and an ultrasonic dispersing machine.

The added amount of the super-high contrast agent is preferably 1 × 10 ^{-6 to} 1 × 10 ^-2 mol, and more preferably 1 × 10 ^{-5 to} 5 × 10 ^-3 mol per mol of silver halide. More preferably, the amount is 2 × 10 ^{−5 to} 5 × 10 ⁻³ mol.

In addition to the super-high contrast agent, a high-contrast accelerator may be used. Examples of the high contrast accelerator include amine compounds (described in US Pat. No. 5,545,505), hydroxamic acids (described in US Pat. No. 5,545,507), acrylonitriles (described in US Pat. No. 5,545,507), and hydrazine compounds (described in US Pat. No. 5,545,507). 5558983).

The photosensitive layer or the non-photosensitive layer preferably further contains a color tone adjusting agent. About color tone adjuster,
It is described in Research Disclosure Magazine No. 17029.

Examples of color tone adjusting agents include imides (eg, phthalimide), cyclic imides (eg, succinimide), pyrazolin-5-ones (eg, 3-phenyl-2-pyrazolin-5-one, -Phenylurazole), quinazolinones (eg, quinazoline, 2,4-thiazolidinedione), naphthalimides (eg, N-hydroxy-1,
8-naphthalimide), a cobalt complex (eg, hexamine trifluoroacetate of cobalt), mercaptans (eg, 3-mercapto-1,2,4-triazole), N- (aminomethyl) aryldicarboximides (eg, N- (dimethylaminomethyl) phthalimide), blocked pyrazoles (eg, N, N′hexamethylene-1-carbamoyl-3,5-dimethylpyrazole), isothiuronium derivatives (eg, 1,8- ( A combination of 3,6-dioxaoctane) bis (isothiuronium trifluoroacetate) and a photobleach (eg, 2- (tribromomethylsulfonyl) benzothiazole), a merocyanine dye (eg, 3-
Ethyl-5-((3-ethyl-2-benzothiazolinylidene) -1-methylethylidene) -2-thio-2,4-oxazolidinedione (oxaz
olazinedione)), phthalazinone compounds and metal salts thereof (eg, phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, 2,3-dihydro-1,4- Phthalazinedione, 8-methylphthalazine), a combination of a phthalazinone compound and a sulfinic acid derivative (eg, sodium benzenesulfinate), a phthalazinone compound and a sulfonic acid derivative (eg, sodium p-toluenesulfonate)
Phthalazine and its derivatives (eg, phthalazine, 6-isopropylphthalazine, 6-methylphthalazine), a combination of phthalazines and phthalic acid,
Phthalazine or a phthalazine adduct and a dicarboxylic acid (preferably o-phenylene acid) or an anhydride thereof (eg, maleic anhydride, phthalic acid, 2,3-naphthalenedicarboxylic acid, phthalic anhydride, 4-methylphthalic acid, 4 -Nitrophthalic acid, tetrachlorophthalic anhydride), quinazolinediones, benzoxazine, naltoxazine derivatives, benzoxazine-2,4-diones (eg, 1,3-benzoxazine-2,4-dione) , Pyrimidines, asymmetric-triazines (for example,
2,4-dihydroxypyrimidine) and a tetraazapentalene derivative (eg, 3,6-dimerocapto-1,4-diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene). Phthalazines are particularly preferred.

The color adjusting agent is preferably contained in the photosensitive layer surface in an amount of 0.1 to 50 mol% per mol of silver.
More preferably, the content is 0.5 to 20 mol%.

An antifoggant may be added to the photosensitive layer or the non-photosensitive layer (preferably the photosensitive layer). As an antifoggant, a mercury compound (described in US Pat. No. 3,589,903) is more preferable than a non-mercury compound (US Pat. No. 3,874).
No. 946, No. 4546075, No. 44452885,
Nos. 4,756,999 and 5,028,523, UK Patent Application Nos. 92221383.4 and 93001777.7.
Nos. 9311790.1 and JP-A-59-1790.1.
57234).

Particularly preferred antifoggants are heterocyclic compounds having a halogen (F, Cl, Br, I) substituted methyl group.

The photothermographic material further comprises a surfactant,
Antioxidants, stabilizers, plasticizers, ultraviolet absorbers or coating aids may be added. Various additives are added to either the photosensitive layer or the non-photosensitive layer. About them, WO98 / 36322, EP803376A1
No., JP-A Nos. 10-186567 and 10-18568.
Reference can be made to each specification such as the number.

In the photosensitive layer according to the invention, a polyhydric alcohol (for example, US Pat.
Glycerin and diols of the type described in U.S. Pat. No. 960,404), fatty acids or esters described in U.S. Pat. Nos. 2,588,765 and 3,121,060, and silicone resins described in British Patent No. 955,061.

In the present invention, it is preferable to add a decoloring dye and a base precursor to the non-photosensitive layer of the photothermographic material so that the non-photosensitive layer functions as a filter layer or an antihalation layer. A photothermographic material generally has a non-photosensitive layer in addition to a photosensitive layer. The non-photosensitive layer may be arranged in such a manner that (1) a protective layer provided on the photosensitive layer (farther than the support), (2) between a plurality of photosensitive layers or between the photosensitive layer and the protective layer. , An undercoat layer provided between the photosensitive layer and the support, and a back layer provided on the opposite side of the photosensitive layer. The filter layer is provided on the photosensitive material as the layer (1) or (2). The antihalation layer is provided on the photosensitive material as the layer (3) or (4).

The decolorizing dye and the base precursor are preferably added to the same non-photosensitive layer. However, they may be separately added to two adjacent non-photosensitive layers. Further, a barrier layer may be provided between the two non-photosensitive layers. In the present specification, `` the layer contains a decolorizing dye and a base precursor '' means that the `` layer '' is plural, that is, the case where a plurality of layers are adjacent layers that separately contain the decolorizing dye and the base precursor. included.

As a method of adding the decolorizable dye to the non-photosensitive layer, a method of adding a solution, an emulsion, a solid fine particle dispersion or a polymer impregnated substance to the coating solution for the non-photosensitive layer can be adopted. Further, a dye may be added to the non-photosensitive layer using a polymer mordant. These addition methods are the same as the method of adding a dye to an ordinary photothermographic material. Latex used in polymer impregnation is disclosed in US Pat.
9363, West German Patent Publication No. 25141274, 25
No. 41230, European Patent Publication 029104, and JP-B-53-41091. Further, the emulsification method of adding a dye to a solution in which a polymer is dissolved is described in International Publication No. 88/00723.

The amount of the decolorizable dye to be added is determined depending on the use of the dye. Generally, the optical density (absorbance) measured at the target wavelength is used in an amount exceeding 0.1. The optical density is preferably from 0.2 to 2. The amount of the dye used to obtain such an optical density is generally 0.0
It is about 01 to 1 g / m ² . Preferably, 0.005
To about 0.8 g / m ² , and particularly preferably 0.0
It is about 1 to 0.2 g / m ² .

When the dye is decolorized according to the present invention, the optical density can be reduced to 0.1 or less. Two or more decolorizable dyes may be used in combination in a heat-decolorable recording material or a photothermographic material. Similarly, two or more base precursors may be used in combination.

The light-sensitive material of the present invention comprises an antistatic or conductive layer such as a soluble salt (for example, chloride or nitrate), a vapor-deposited metal layer, US Pat. Nos. 2,861,056 and
It may have a layer containing an ionic polymer as described in US Pat. No. 3,206,312 or an insoluble inorganic salt as described in US Pat. No. 3,428,451.

A method for obtaining a color image by using the photothermographic material of the present invention is described in JP-A-7-13295, page 10, left column 4
There is a method described from the third line to the 11th left column, 40th line. Further, as a stabilizer for color dye images, UK Patent No. 1,326,889
No. 3,432,300, U.S. Pat.No. 3,698,909, U.S. Pat.
Nos. 574,627, 3,573,050, 3,764,337 and 4,042,394.

The photothermographic material of the present invention may be applied by any method. Specifically, extrusion coating, slide coating, curtain coating, dip coating, knife coating,
Various coating operations are used, including flow coating or extrusion coating using a hopper of the type described in U.S. Pat. No. 2,681,294, and are described by Stephen F. Kistl.
er, "LIQUID FILM COATING" by Peter M. Schweizer (C
Extrusion coating or slide coating described on pages 399 to 536, published by HAPMAN & HALL (1997) is preferably used, and particularly preferably slide coating is used. An example of the shape of the slide coater used for slide coating is shown in Figure 11 on page 427 of the same book.
in b.1. Also, if desired, the method described on page 399 to 536 of the same book, U.S. Pat.No. 2,761,791 and British Patent 837,0
Two or more layers can be coated simultaneously by the method described in No. 95. The simultaneous coating method is preferably used.

In the present invention, a surfactant may be used for the purpose of improving coating properties and charging. As the surfactant, any surfactant such as nonionic, anionic, cationic, and fluorine can be used as appropriate. Specifically,
No. 62-170950, Fluoropolymer surfactants described in U.S. Pat.No.5,380,644, JP-A-60-244945, JP-A-63-18
8135 No. fluorinated surfactants described in U.S. Pat.
No. 5,965, and the like, and polysiloxy acid-based surfactants described in JP-A-6-301140 and the like, and anionic surfactants and the like.

The photothermographic material forms an image by heating after image exposure. By this heat development, a black silver image is formed. The image exposure is preferably performed using a laser. The heating temperature for thermal development is 80 to 25.
The temperature is preferably 0 ° C, more preferably 100 to 200 ° C. The heating time is generally between 1 second and 2 minutes.

As a method of thermal development, a plate heater method is preferable. Japanese Patent Application No. 9-229684 and Japanese Patent Application No. 10-1776 disclose heat development methods using a plate heater method.
No. 10 is preferred, a thermal developing apparatus for obtaining a visible image by contacting the photothermographic material having a latent image formed thereon with a heating unit in a heat development unit, wherein the heating unit is a plate heater And a plurality of pressing rollers are provided to face each other along one surface of the plate heater, and heat development is performed by passing the photothermographic material between the pressing roller and the plate heater. This is a heat developing device.

As a heating method in the heat development processing, for example, the forms shown in FIGS.

The photothermographic material conveyed to the image exposing section is exposed to laser light or the like scanned by a light beam, and a latent image is formed on the photothermographic material. Transported to At this time, dust on the back and front surfaces of the photothermographic material is removed by the dust removing roller.

As shown in FIG. 1, the heat developing section 18
Is a portion where a latent image is converted into a visible image by performing heat development by heating the photothermographic material. In the present invention, the plate heater 120 and the plate heater And a plurality of pressing rollers 122 arranged in a row.

The plate heater 120 is a plate-like heating member in which a heating element such as a nichrome wire is laid and accommodated in a plane, and is maintained at the developing temperature of the photothermographic material. Further, it is preferable that a fluororesin is coated on a surface of the plate heater 120 for the purpose of reducing frictional resistance or imparting abrasion resistance, or a sheet made of a fluororesin is attached.

Further, when the photothermographic material is heated, the volatile components evaporate during the heat development, whereby the photothermographic material floats up from the plate heater 120 and the contact between the photothermographic material and the plate heater 120 becomes uneven. May be. Therefore, it is preferable to form minute irregularities on the surface of the plate heater 120 in order to release the vapor.

In order to compensate for a decrease in temperature due to heat radiation at both ends of the plate heater 120, it is preferable to provide a temperature gradient so that the temperature at both ends is higher than the other portions.

The pressing roller 122 is a plate heater 12
0, or at a predetermined pitch over the entire length of the plate heater 120 in the transport direction with an interval equal to or less than the thickness of the photothermographic material.
The plate 22 and the plate heater 120 form a path for transporting the photothermographic material. By arranging the photothermographic material conveying path at an interval equal to or less than the thickness of the photothermographic material, buckling of the photothermographic material can be prevented. A supply roller pair 126 for supplying the photothermographic material to the thermal developing section 18 in the direction indicated by an arrow in FIG. A pair 128 is provided.

Further, it is preferable to dispose a heat retaining cover 125 for keeping the temperature on the opposite side of the pressing roller 122 from the plate heater 120.

When the photothermographic material is transported,
When the leading end of the photothermographic material strikes the pressing roller 122, the photothermographic material stops momentarily. At this time, if the pressing rollers 122 are separated at a constant pitch, the same portion of the photothermographic material stops for each pressing roller 122 and that portion is pressed by the plate heater 120 for a long time. As a result, in the photothermographic material, streak-like development unevenness extending in the width direction occurs. Therefore, it is preferable to make the pitch of each pressing roller 122 non-uniform.

Further, as shown in FIG.
A configuration is also possible in which a driving roller 130 having an envelope surface as a peripheral surface is provided in contact with each of the pressing rollers 122, and each of the pressing rollers 122 is rotated by the rotation of the driving roller 130.

In the above description, the plate heater 120 also includes a plate member made of a heat conductor and a heat source disposed on the side of the plate member opposite to the heating surface of the photothermographic material.

[0104]

The present invention will be specifically described below with reference to examples. Example 1 (Preparation of Silver Halide Emulsion 1) To a stainless steel reaction vessel coated with titanium was added a solution obtained by adding 8 cc of a 1 wt% potassium bromide solution to 1421 cc of distilled water, further adding 8.2 cc of 1N nitric acid and 20 g of phthalated gelatin. While maintaining the liquid temperature at 37 ° C. while stirring, a solution A prepared by adding distilled water to 37.04 g of silver nitrate to 159 cc and a solution B prepared by diluting 32.6 g of potassium bromide to a volume of 200 cc with distilled water were prepared. The whole amount of the solution A was added at a constant flow rate over 1 minute while maintaining the pAg at 8.1 by the control double jet method (the solution B was added by the controlled double jet method). Thereafter, 30 cc of a 3.5 wt% aqueous hydrogen peroxide solution was added, and 36 cc of a 3 wt% aqueous solution of compound 1 was added. Thereafter, Compound A was dissolved again in Solution A2, which was again diluted with distilled water to 317.5 cc, and Compound 2 was dissolved in Solution B so that the final concentration was 1 × 10 ^-4 mol per mol of silver. Using the solution B2 diluted with distilled water to 400 cc twice that of B, the solution A was maintained at a constant flow rate by the controlled double jet method while maintaining the pAg at 8.1.
2 was added over 10 minutes (solution B2 was added by a controlled double jet method). Then, compound 3
50cc of 0.5wt% methanol solution is added, and pA is further added with silver nitrate.
g to 7.5, then adjust the pH to 3.8 with 1N sulfuric acid, stop stirring, perform sedimentation / desalting / washing steps, add 3.5g of deionized gelatin, add 1N sodium hydroxide. Then, the mixture was adjusted to pH 6.0 and pAg 8.2 to prepare a silver halide dispersion.

The grains in the completed silver halide emulsion have an average equivalent circle diameter of 0.053 μm and a coefficient of variation of the equivalent spherical diameter of 18%.
Was pure silver bromide particles. The particle size and the like were determined from the average of 1000 particles using an electron microscope. The [100] plane ratio of the particles was determined to be 85% using the Kubelka-Munk method.

The emulsion was heated to 50 ° C. while stirring, and 5 cc of a 0.5 wt% solution of compound 4 and 5 cc of a 3.5 wt% solution of compound 5
1 minute later, Compound 6 was added in an amount of 3 × 10 ⁻⁵ mol per mol of silver. After a further 2 minutes, a solid dispersion of the spectral sensitizing dye A (aqueous gelatin solution) was added at 5 × 10 ⁻³ mol per mol of silver, and after a further 2 minutes tellurium sensitizer B was added at 5 × 10 ³ mol per mol of silver.
10 ^-5 mol was added and the mixture was aged for 50 minutes. Immediately before the completion of ripening, Compound 3 was added in an amount of 1 × 10 ⁻³ mol per mol of silver, and the temperature was lowered to terminate the chemical sensitization. Thus, a silver halide emulsion 1 was prepared.

<< Preparation of Fatty Acid Silver Salt >> 87.6 g of behenic acid (product name: Edenor C22-85R) manufactured by Henkel, 423 m of distilled water
l, 49.2 ml of 5N-NaOH aqueous solution and 120 ml of tert-butanol were mixed and reacted by stirring at 75 ° C. for 1 hour to obtain a sodium behenate solution. Separately, an aqueous solution of 40.4 g of silver nitrate 206.2 ml
(PH 4.0) was prepared and kept at 10 ° C. The reaction vessel containing 635 ml of distilled water and 30 ml of tert-butanol was kept at 30 ° C., and while stirring, the whole amount of the sodium behenate solution and the whole amount of the silver nitrate aqueous solution were kept at a constant flow rate for 62 minutes, 10 seconds and 60 minutes, respectively. And added. At this time, only the aqueous solution of silver nitrate was added for 7 minutes and 20 seconds after the start of the aqueous solution of silver nitrate, and then the addition of the sodium behenate solution was started. Was added. At this time, the temperature inside the reaction vessel was set at 30 ° C., and the external temperature was controlled so that the temperature of the solution did not rise. The piping of the addition system of the sodium behenate solution was kept warm by steam tracing, and the steam opening was adjusted so that the liquid temperature at the outlet of the tip of the addition nozzle became 75 ° C. Also, the piping for the addition system of the silver nitrate aqueous solution is
The temperature was maintained by circulating cold water outside the double tube.
The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically with respect to the stirring axis, and were adjusted so as not to contact the reaction solution. After the completion of the addition of the sodium behenate solution, the mixture was allowed to stir at the same temperature for 20 minutes, and the temperature was lowered to 25 ° C. Thereafter, the solid content was separated by suction filtration, and the solid content was washed with water until the conductivity of the filtered water became 30 μS / cm. Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying. When the morphology of the obtained silver behenate particles was evaluated by electron microscopic photographing, the average projected area diameter was 0.52 μm,
It was a scale-like crystal having a coefficient of variation of 0.14 μm and an average equivalent sphere diameter of 15%.

For a wet cake having a dry solid content of 100 g, 7.4 g of polyvinyl alcohol (trade name: PVA-205)
And water were added to make the total amount 385 g, and the mixture was pre-dispersed with a homomixer.

Next, the pre-dispersed stock solution is dispersed in a disperser (trade name: Microfluidizer M-110S-EH, manufactured by Microfluidics International Corporation, using G10Z interaction chamber).
The pressure was adjusted to 1750 kg / cm ² and the mixture was treated three times to obtain a silver behenate dispersion. In the cooling operation, a coiled heat exchanger was mounted before and after the interaction chamber, and the temperature of the refrigerant was adjusted to a desired dispersion temperature.

(Preparation of 25 wt% dispersion of reducing agent) 1,1-bis
Add 176 g of water to 80 g of (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane and 64 g of a 20 wt% aqueous solution of modified polyvinyl alcohol Poval MP-203 manufactured by Kuraray Co., Ltd., and mix well. A slurry was obtained. Prepare 800 g of zirconia beads having an average diameter of 0.5 mm, put them in a vessel together with the slurry, and use a disperser (1 / 4G sand grinder mill:
The mixture was dispersed for 5 hours using IMEX Co., Ltd. to obtain a reducing agent dispersion. The reducing agent particles contained in the thus obtained reducing agent dispersion had an average particle size of 0.72 μm.

(Preparation of a 20 wt% dispersion of a mercapto compound) 64 wt% of 3-mercapto-4-phenyl-5-heptyl-1,2,4-triazole and 20 wt% of modified polyvinyl alcohol poval MP-203 manufactured by Kuraray Co., Ltd. 224 g of water was added to 32 g of the aqueous solution and mixed well to form a slurry. 800 g of zirconia beads having an average diameter of 0.5 mm were prepared, placed in a vessel together with the slurry, and dispersed with a disperser (1 / 4G sand grinder mill: manufactured by IMEX Co., Ltd.) for 10 hours to obtain a mercapto dispersion. The mercapto compound particles contained in the thus obtained mercapto compound dispersion had an average particle size of 0.67 μm.

(Preparation of 30 wt% dispersion of organic polyhalogen compound) 48 g of tribromomethylphenylsulfone and 3-tribromomethylsulfonyl-4-phenyl-5-tridecyl-
224 g of water was added to 48 g of 1,2,4-triazole and 48 g of a 20 wt% aqueous solution of modified polyvinyl alcohol poval MP-203 manufactured by Kuraray Co., Ltd., and mixed well to form a slurry. Average diameter
800 g of 0.5 mm zirconia beads were prepared, put into a vessel together with the slurry, and dispersed for 5 hours with a disperser (1/4 G sand grinder mill: manufactured by IMEX Co., Ltd.) to obtain an organic polyhalogen compound dispersion. Was. The polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had an average particle size of 0.74 μm.

(Preparation of 10 wt% methanol solution of phthalazine compound) 10 g of 6-isopropylphthalazine was dissolved in 90 g of methanol and used.

(Preparation of 20 wt% dispersion of pigment) CI Pigme
64 g of nt Blue 60 and 6.4 g of Demol N manufactured by Kao Corporation
250 g was added and mixed well to obtain a slurry. Average diameter 0.
800 g of 5 mm zirconia beads were prepared, placed in a vessel together with the slurry, and dispersed with a disperser (1/4 G sand grinder mill: manufactured by IMEX Co., Ltd.) for 25 hours to obtain a pigment dispersion. The pigment particles contained in the pigment dispersion thus obtained had an average particle size of 0.21 μm.

(Preparation of 40 wt% of SBR latex) Ultrafiltration (UF) purified SBR latex was obtained as follows. Dilute the following SBR latex 10 times with distilled water to UF
-Purification module, FS03-FC-FUY03A1 (Ion conductivity 1.5mS / using Daisen Membrane System Co., Ltd.)
What was diluted and purified to cm was used. At this time, the latex concentration was 40% by weight.

(SBR latex: -St (68) -Bu (29) -AA (3)-
Latex) equilibrium water content is 0.6wt%, average particle size 0.1μm, concentration 45wt%,
Ion conductivity 4.2mS / cm (Ion conductivity was measured using a latex stock solution (40w using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.)
t%) at 25 ° C), pH 8.2

(Preparation of Coating Solution for Emulsion Layer (Photosensitive Layer)) 1.1 g of the above-obtained 20 wt% dispersion of the pigment, silver organic acid dispersion 103
g, polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.)
0 wt% aqueous solution 5 g, the above 25 wt% reducing agent dispersion 25 g, organic polyhalogen compound 30 wt% dispersion 11.5 g, mercapto compound
20 wt% dispersion 3.1 g, UF purified SBR latex 40 wt%
106 g and 8 ml of a 20 wt% solution of a phthalazine compound were added, and 10 g of silver halide grains were mixed well to prepare a coating solution for an emulsion layer, which was coated to a concentration of 70 ml / m ² .

The viscosity of the above emulsion layer coating solution was measured with a B-type viscometer of Tokyo Keiki, and was 85 mPa · s at 40 ° C. (No. 1 rotor).
s].

The viscosity of the coating solution at 25 ° C. using an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd. was determined at a shear rate of 0.1, 1, 10, 100 or 1000.
1500/220, 70, 40, 20 (mP
a · s].

(Preparation of Emulsion Surface Intermediate Layer Coating Solution) A 10 wt% aqueous solution of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.)
2g, pigment 20wt% dispersion 0.5g, methyl methacrylate /
Styrene / 2-ethylhexyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer weight ratio 59/9/26/5/1) 27.5wt% latex 226g of aerosol OT (American Cyanamid) 5wt% aqueous solution
2 ml was added to make a coating solution for the intermediate layer, which was applied so as to be 5 ml / m ² . The viscosity of the coating solution was 21 mPa · s using a B-type viscometer at 40 ° C. (No. 1 rotor).

(Preparation of Coating Solution for First Layer of Emulsion Surface Protective Layer) Inert gelatin (80 g) was dissolved in water, and a 20 wt% dispersion of pigment (0.3 wt.
g, 64 ml of a 10 wt% methanol solution of phthalic acid, 74 ml of a 10 wt% aqueous solution of 4-methylphthalic acid, 28 ml of 1N sulfuric acid, and 5 ml of a 5 wt% aqueous solution of aerosol OT (manufactured by American Cyanamid Co.) are added, and the total amount is 1000 g. Then, water was added to obtain a coating solution for the first layer of the emulsion surface protective layer, and the solution was coated so as to be 10 ml / m ² .

The viscosity of the coating solution was 17 mPa · s at 40 ° C. (No. 1 rotor) using a B-type viscometer. Further, a coating liquid using polyvinyl alcohol instead of gelatin was prepared.

(Preparation of Coating Solution for Second Layer of Emulsion Surface Protective Layer) Inert gelatin (100 g) was dissolved in water, and N-perfluorooctylsulfonyl-N-propylalanine potassium salt (5 w) was added.
20 ml of a t% solution, 16 ml of a 5 wt% solution of Aerosol OT (manufactured by American Cyanamid Co.), 25 g of polymethyl methacrylate fine particles (average particle size 4.0 μm), 1.4 g of phthalic acid, 4-g
1.6 g of methylphthalic acid, 44 ml of 1N sulfuric acid, and 445 ml of 4 wt% chrome alum, and water were added to make a total amount of 2000 g to prepare a coating solution for the second layer of the emulsion surface protective layer, so that the solution became 10 ml / m ^2. Was applied.

The viscosity of the coating solution was 9 mPa · s at 40 ° C. with a B-type viscometer (No. 1 rotor). Further, a coating solution was prepared using polyvinyl alcohol instead of gelatin and boric acid instead of chrome alum.

(Preparation of PET support) Intrinsic viscosity IV = 0.66 (measured at 25 ° C. in phenol / tetrachloroethane = 6/4 (weight ratio)) using terephthalic acid and ethylene glycol according to a conventional method. Of PET. After pelletizing this at 130 ° C
It was dried for 4 hours, melted at 300 ° C, extruded from a T-die, and quenched to prepare an unstretched film with a thickness of 175 µm after heat setting.

This was longitudinally stretched 3.3 times using rolls having different peripheral speeds, and then horizontally stretched 4.5 times using a tenter. The temperatures at this time were 110 ° C. and 130 ° C., respectively. After that, it was heat-set at 240 ° C. for 20 seconds and relaxed 4% in the transverse direction at the same temperature. Then, after slitting the chuck portion of the tenter, knurling was performed on both ends and wound at 4 kg / cm ² to obtain a roll having a thickness of 175 μm.

(Surface Corona Treatment) Using a solid state corona treatment machine 6KVA model manufactured by Pillar Co., both surfaces of the support were treated at room temperature at 20 m / min. From the current and voltage readings at this time, it was found that the support was treated at 0.375 kV · A · min / m ² . At this time, the processing frequency was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

(Preparation of Undercoating Support) (1) Undercoating Application (1-1) Undercoating Layer Application Formula (First Layer) Butadiene-styrene copolymer latex 13 ml (solid content 43 wt%, butadiene / styrene weight ratio = 32/68) 2,4-Dichloro-6-hydroxy-S-triazine sodium salt 8 wt% aqueous solution 7 ml Sodium laurylbenzenesulfonate-1 wt% aqueous solution 1.6 ml distilled water 80 ml Prescription (photosensitive layer side second layer) Gelatin 0.9 g 20 wt% dispersion 1g methylcellulose pigment (Metolose SM15 degree of substitution from 1.79 to 1.83) 0.1 g acetic acid (concentration 99 wt%) 0.02 ml distilled water 98ml formulation (back surface-side second layer) SnO ₂ / Sb (9 / 1 weight ratio, average particle diameter 0.25 [mu] m) 100 mg / m ² gelatin 77 mg / m ² sodium dodecylbenzenesulfonate 1 mg / m ² dihexyl -α- Suruhosakushi Over door sodium 4mg / m ²

(Preparation of Undercoating Support) Thickness 175 μm
After performing the above-mentioned corona discharge treatment on both surfaces of the biaxially stretched polyethylene terephthalate support, the undercoating coating solution was coated with a wire bar so that the wet coating amount was 6 ml / m ² (per one side). Dry at 5 ° C. for 5 minutes. Next, after one side (photosensitive layer side) is subjected to corona discharge treatment, the undercoating coating liquid formulation is applied with a wire bar so that the wet coating amount is 9 ml / m ² , and dried at 180 ° C. for 5 minutes. The undercoat coating solution was applied to the back surface (back surface) with a wire bar so that the wet application amount was 5 ml / m ² , and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

(Preparation of Back Surface Coating Liquid) (Preparation of Solid Precursor Dispersion (a) of Base Precursor) 64 g of base precursor compound (11), 28 g of diphenylsulfone compound (12) and surfactant Demol manufactured by Kao Corporation
10 g of N was mixed with 220 ml of distilled water, and the mixture was dispersed in beads using a sand mill (1/4 Gallon sand grinder mill, manufactured by Imex Co., Ltd.), and the average particle size was 0.2 μm.
A solid fine particle co-dispersion liquid of a base precursor compound and a diphenylsulfone compound was obtained.

(Preparation of Dye Solid Fine Particle Dispersion) 9.6 g of cyanine dye compound (13) and 5.8 g of sodium P-alkylbenzenesulfonate were mixed with 305 ml of distilled water, and the mixture was subjected to a sand mill (1/4 Gallon sand grinder mill, The beads were dispersed by using IMEX Co., Ltd.) to obtain a dye solid fine particle dispersion having an average particle diameter of 0.2 μm.

(Preparation of antihalation layer coating solution) PVA
-217; 17 g, polyacrylamide 9.6 g, 70 g of solid fine particle dispersion (a) of the above base precursor, 56 g of solid fine particle dispersion of the above dye, 1.5 g of polymethyl methacrylate fine particles (average particle size 6.5 μm), sodium polyethylene sulfonate 2.2 g, coloring dye compound (14) 0.2 g, H ₂ O
Were mixed to prepare an antihalation layer coating solution.

(Preparation of back surface protective layer coating solution)
° C, PVA-117; 50 g, polystyrene sodium sulfonate 0.2 g, N, N-ethylenebis (vinylsulfoneacetamide) 2.4 g, t-octylphenoxyethoxyethaneethanesulfonate 1 g, compound (15) 30 mg, C ₈
F ₁₇ SO ₃ K 32 mg, C ₈ F ₁₇ SO ₂ N (C ₃ H ₇ ) (CH ₂ CH ₂ O) ₄ (CH ₂ ) ₄ -SO ₃ N
a 64 mg and 950 ml of H ₂ O were mixed to prepare a coating solution for the back surface protective layer.

[0134]

Embedded image

[0135]

Embedded image

[0136]

Embedded image

<< Preparation of Photothermographic Material >> On the back surface side of the above-mentioned undercoated polyethylene terephthalate film (support), an antihalation layer coating solution was applied at a solid content of solid fine particle dye of 0.04 g / m ² . In addition, a coating solution for the back surface protective layer was simultaneously and multi-layer coated so that the PVA coating amount was 1 g / m ^2, and dried to form a halation-preventive back layer.

A sample of a photothermographic material was prepared by simultaneously coating the emulsion layer, the intermediate layer, the first protective layer, and the second protective layer on the surface opposite to the back surface in the order of the emulsion layer, the intermediate layer, the first protective layer, and the second protective layer by slide bead coating. Was prepared.

The coating was performed at a speed of 160 m / min, the distance between the tip of the coating die and the support was set to 0.18 mm, and the pressure in the decompression chamber was set 392 Pa lower than the atmospheric pressure. In the subsequent chilling zone, air with a dry-bulb temperature of 18 ° C and a wet-bulb temperature of 12 ° C was blown for 30 seconds to cool the coating liquid, and then the dry-bulb temperature was raised in the hovering-type floating type drying zone. Dry air at 30 ° C. and a wet bulb temperature of 18 ° C. was blown for 200 seconds, passed through a drying zone at 70 ° C. for 30 seconds, and then cooled to 25 ° C. to evaporate the solvent in the coating solution. The average wind speed of the air blown to the coating liquid film surface in the chilling zone and the drying zone was 7 m / sec.

(Evaluation of cracks) 50 g of a sample of the prepared photothermographic material was taken at 25 ° C. and 60% RH (relative humidity) with a stainless needle having a 0.5 mm-shaped semicircular tip on the emulsion side. After applying a load at a speed of 1 cm / sec, the character "rose" was exposed using a semiconductor laser emitting at 660 nm and using a laser beam superimposed vertically and multiplied by high frequency. Thereafter, the plate heater type thermal developing apparatus 10 shown in FIG. 1 of Japanese Patent Application No. 9-229684 is used for 120 minutes.
Thermal development was performed at 20 ° C. for 20 seconds, and evaluated visually. However, the smell was eliminated using a metal mesh and activated carbon filter.

：: good without cracks Δ: slightly cracked but acceptable ×: cracked (problem)

[0142]

[Table 1]

From Table 1, the effect of the present invention is clear. Further, the sample of the present invention had good photographic performance.

Example 2 As in Example 1, except that the emulsion layer was replaced with SBR latex by gelatin (equilibrium water content: 9 wt%) or PV
A sample was prepared using A (equilibrium water content 5 wt%).

[0145] The effect as in Example 1 was not observed, and no crack problem occurred in any case. From this, it was found that cracks were a particular problem in the SBR latex of the emulsion layer.

Example 3 A sample was prepared in the same manner as in Example 1 except that the emulsion layers were replaced with the following latexes Lb1 and Lc1 (both having an equilibrium water content of less than 2 wt%) instead of the SBR latex. The same effect of polyvinyl alcohol as in Example 1 was obtained. In addition, the equilibrium moisture content is a thing under 25 degreeC and 60% RH.

(Synthesis of Lb1) 140 g of styrene was placed in a glass autoclave (TEM-V1000, manufactured by Pressure Glass Co., Ltd.).
280 g of distilled water, 4.44 g of a surfactant (Sandet BL (manufactured by Sanyo Chemical Co., Ltd.)) and 6 g of acrylic acid were added, and the mixture was stirred for 1 hour under a nitrogen stream. Thereafter, 54 g of 2-ethylhexyl acrylate was added, and the temperature was raised to 70 ° C. Next, 20 g of an aqueous solution of ammonium persulfate (5 wt%) was added, and the mixture was stirred for 10 hours. Thereafter, the temperature of the reaction vessel was lowered to room temperature to obtain a styrene-acryl latex. A 1N aqueous ammonia solution was added to the latex to adjust the pH to 7.5.

Thus, a latex (Lb1) having an average particle size of 98 nm and a concentration of 42 wt% was obtained. The equilibrium water content of the polymer at 25 ° C. and 60% RH was 0.7% by weight.

(Synthesis of Lc1) 126 g of methyl methacrylate, 280 g of distilled water, and a surfactant (Sandet B) were placed in a glass autoclave (TEM-V1000, manufactured by Pressure Glass Co., Ltd.).
L (manufactured by Sanyo Chemical Co., Ltd.)) and acrylic acid (4 g) were added, and the mixture was stirred under a nitrogen stream for 1 hour. Thereafter, 70 g of ethyl acrylate was added, and the temperature was raised to 60 ° C. Next, 20 g of an aqueous potassium persulfate solution (5 wt%) was added, and the mixture was stirred for 10 hours. Thereafter, the temperature of the reaction vessel was lowered to room temperature to obtain an acrylic latex. A 1N aqueous ammonia solution was added to the latex to adjust the pH to 7.5.

Thus, a latex (Lc1) having an average particle diameter of 101 nm and a concentration of 44 wt% was obtained. The equilibrium water content of the polymer at 25 ° C. and 60% RH was 0.7% by weight.

Example 4 The same results as in Examples 1 to 3 were obtained when heating was performed at 100 ° C. or higher (temperature range up to 230 ° C.) with a thermal head of the thermal system.

[0152]

According to the present invention, the occurrence of cracks during thermal development can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a plate heater type thermal developing section.

FIG. 2 is a schematic cross-sectional view of a plate heater type thermal developing section.

[Explanation of symbols]

 18 Thermal developing unit 120 Plate heater 122 Holding roller 130 Drive roller

Claims (7)

[Claims] 1. A heat-developable material having a constituent layer including at least one image-recording layer on a support, wherein the image-recording layer is coated with a coating solution in which 30% by weight or more of a solvent is water, and dried. The main binder of the image recording layer is a polymer having an equilibrium water content of 2% by weight or less at 25 ° C. and 60% RH, and the outermost surface layer on the image recording layer side among the constituent layers contains polyvinyl alcohol. A heat-developable material, characterized in that: 2. The heat-developable material according to claim 1, wherein the image recording layer is a photosensitive layer containing at least photosensitive silver halide particles and a binder. 3. The heat-developable material according to claim 1, further comprising a layer containing polyvinyl alcohol on a side of the support opposite to the image recording layer. 4. The heat-developable material according to claim 1, which is heat-developed at a temperature of 100 ° C. or higher. 5. A support having at least two constituent layers including the image recording layer on the same side as the image recording layer, and applying the at least two constituent layers simultaneously. 4. The heat-developable material according to any one of to 6. The heat development material according to claim 1, wherein the image recording layer further contains an organic silver salt and a reducing agent for silver ions. 7. The heat developing material according to claim 1, wherein the outermost surface layer further contains boric acid.