JP3194266B2 - Polyvinyl acetal resin for photothermographic material, modified polyvinyl acetal resin for photothermographic material, and photothermographic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-developable light-sensitive material, particularly a polyvinyl for heat-developable light-sensitive material used in a heat-developable light-sensitive material containing an organic silver salt and a reducing agent for development in the same composition. The present invention relates to an acetal resin, a modified polyvinyl acetal resin for a photothermographic material, and a photothermographic material.

[0002]

2. Description of the Related Art A heat-developable photosensitive material is mainly composed of a composition obtained by dispersing a silver salt of a fatty acid, an organic reducing agent and, in some cases, a small amount of photosensitive silver halide in a polymer binder, on a support. It is made by coating.

Conventionally, silver halide light-sensitive materials that have been widely used have been used in the field of image formation as high-quality materials due to their excellent photographic characteristics. Since the treatment process is a wet process, there is a problem that the treatment is complicated and a large amount of chemical waste liquid is discharged. Therefore, at present, a heat developable photosensitive material in which a development process is performed by heat treatment has been developed and put into practical use.

For example, Japanese Patent Publication No. 43-4924 discloses a heat-developable photosensitive material comprising an organic silver salt, a reducing agent and silver halide in catalytic contact with organic silver ions. . That is, these heat developable photosensitive materials are:
Using a film-forming binder such as polyvinyl butyral, polymethyl methacrylate, cellulose acetate, polyvinyl acetate, cellulose acetate propionate, cellulose acetate butyrate on a support such as paper, plastic film, metal foil, or glass plate. It is described that it is used after being applied.

[0005] As the above-mentioned film-forming binder, specifically, polyvinyl butyral resin is most suitably used. However, general polyvinyl butyral resins have various compositions, and furthermore, contain a small amount of impurities in the production method, and due to the influence of these impurities, the prepared binder solution becomes photosensitive and colored, In some cases, fogging, poor gradation, insufficient sensitivity, poor storage stability of the film, and the like occur in the image characteristics after coating.

In order to solve the above problems, improvements have been made on silver salts, reducing substances, additives and the like. For example, as disclosed in JP-A-49-52626, it has been reported that an improvement is achieved by using a silver salt of a thione compound without using an independent stabilizer and a precursor component of a stabilizer. Although polyvinyl butyral resin is also used, there is no disclosure of a technique for solving the problem by specifying the composition of the binder to be used.

Further, among the heat-developable photosensitive materials, a heat-developable silver halide film has image characteristics, especially image density, which are lower than those of a conventional X-ray photosensitive film using a wet gelatin.
Since the sharpness of the image / gradation part is slightly inferior, its improvement is desired. For this purpose, it is necessary to strictly control the nucleus growth of the silver salt during heating, and furthermore, the silver dispersed in the binder It was necessary to improve the dispersibility of the salt.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a polyvinyl acetal resin used as a binder having a specific composition, so that the pot life of a pre-coating solution and the preservation of raw film can be improved. It is an object of the present invention to provide a polyvinyl acetal resin for a heat-developable photosensitive material and a heat-developable photosensitive material using the same, which can improve the properties and fog.

Further, the present invention improves the dispersibility of a silver salt by introducing an acetoacetal moiety into a polyvinyl acetal resin used as a binder or further introducing a modifying group comprising a hydrophilic group. It is possible to sharpen the heat melting property, cooling hardening property, etc., and to precisely control the nucleus growth of the silver salt, thereby improving the image density and the sharpness of the image / gradation area. It is an object of the present invention to provide a polyvinyl acetal resin for an optical material, a modified polyvinyl acetal resin for a heat developable photosensitive material, and a heat developable photosensitive material using the same.

[0010]

According to the first aspect of the present invention, there is provided a polyvinyl acetal resin synthesized by an acetalization reaction of a polyvinyl alcohol and an aldehyde, and having a degree of polymerization of 200. ~ 3
000, and the ratio of residual acetyl groups is 0 to 25.
Mol%, the proportion of residual hydroxyl groups is in the range of 17 to 35 mol%, the composition does not contain an antioxidant, and the residual halide amount is 1%.
There is provided a polyvinyl acetal resin for a heat-developable photosensitive material, wherein the content is not more than 00 ppm.

The invention according to claim 2 is a polyvinyl acetal resin synthesized by an acetalization reaction of polyvinyl alcohol and butyraldehyde, wherein the degree of polymerization is in the range of 200 to 3000 and the ratio of residual acetyl groups is 0. A polyvinyl acetal for a heat-developable photosensitive material, characterized in that the content of the residual hydroxyl group is in the range of 17 to 35 mol%, the antioxidant is not contained, and the amount of the residual halide is 100 ppm or less. A resin is provided.

The invention according to claim 3 is a polyvinyl acetal resin synthesized by an acetalization reaction of polyvinyl alcohol, butyraldehyde, and acetaldehyde, wherein the degree of polymerization is in the range of 200 to 3000,
The proportion of the residual acetyl group is 0 to 25 mol%, the proportion of the residual hydroxyl group is 17 to 35 mol%, and the proportion of the portion acetalized by acetaldehyde in the entire acetalized portion is in the range of 30 to 100%. The present invention provides a polyvinyl acetal resin for a heat-developable photosensitive material, which contains no inhibitor and has a residual halide content of 100 ppm or less.

According to a fourth aspect of the present invention, there is provided a modified polyvinyl acetal resin which is synthesized by an acetalization reaction of polyvinyl alcohol and an aldehyde and has the following modifying group in a side chain, and has a degree of polymerization of 200 to 3,000. Wherein the proportion of residual acetyl groups is in the range of 0 to 25 mol%, the proportion of residual hydroxyl groups is in the range of 17 to 35 mol%, the proportion of modifying groups is in the range of 0.1 to 5 mol%, and an antioxidant And a modified polyvinyl acetal resin for a heat-developable photosensitive material, characterized by having a residual halide content of not more than 100 ppm.

Here, the modifying groups are -COOM, -CH _{2
COOM, -SO 3 M, -OSO 3} M, -PO (OM)
₂ , -P (= O) (R) (OM), at least one hydrophilic group selected from the group consisting of tertiary amines and quaternary ammonium salts (where M is H, Li , N
represents a or K, and R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. )

According to a fifth aspect of the present invention, there is provided the thermal development method according to any one of the first to third aspects, wherein the amount of the remaining alkaline substance in the polyvinyl acetal resin is 0.01% by weight or less. There is provided a polyvinyl acetal resin for a photosensitive material.

In the invention according to claim 6, the amount of the residual alkaline substance in the modified polyvinyl acetal resin is 0.01%.
The modified polyvinyl acetal resin for a heat-developable photosensitive material according to claim 4, wherein the amount is not more than% by weight.

According to a seventh aspect of the present invention, the polyvinyl acetal resin for a heat-developable photosensitive material or the modified polyvinyl acetal resin for a heat-developable photosensitive material according to any one of the first to sixth aspects is used. A heat-developable photosensitive material is provided.

The polyvinyl acetal resin or modified polyvinyl acetal resin used in the present invention has a polymerization degree of 20.
Those having a degree of polymerization of 300 to 1,000 are preferably used, in which the silver salt used in the heat-developable photosensitive material can be easily balanced in dispersibility, coating strength, coatability and the like.

The amount of residual acetyl groups in the polyvinyl acetal resin or the modified polyvinyl acetal resin is from 0 to 25 mol%. If the amount of the residual acetyl group is more than 25 mol%, the resulting photosensitive films will be blocked from each other, and the image will not be clear. More preferably, it is 0 to 15 mol%.

The residual hydroxyl group content of the polyvinyl acetal resin or the modified polyvinyl acetal resin is 17
To 35 mol%, preferably 19 to 30 mol%. When the amount of the residual hydroxyl group is more than 35 mol%, the dispersibility of the silver salt used in the photothermographic material is poor, the silver salt is aggregated, the sensitivity of the obtained film is lowered, and moisture is easily adsorbed. The pot life of the coating solution decreases. When the amount of the remaining hydroxyl groups is less than 17 mol%, the dispersibility of the silver salt is reduced, and the sensitivity is lowered.

The polyvinyl acetal resin or modified polyvinyl acetal resin used in the present invention is synthesized by an acetalization reaction between polyvinyl alcohol and various aldehydes, and is preferably one acetalized with butyraldehyde and / or acetaldehyde. In particular,
The proportion of the acetalized portion of the acetalized portion of the polyvinyl acetal resin is preferably in the range of 30 to 100%, more preferably 50 to 10%, of the entire acetalized portion.
0%. When the portion acetalized by acetaldehyde is less than 30%, the glass transition point of the obtained polyvinyl acetal resin is 80 ° C. or less, the nucleus growth of the photosensitive silver salt proceeds too much, and the dispersibility of the silver salt is also low. And the resolution and sharpness of the image may remain the same as those of the conventional polyvinyl butyral resin.

The polyvinyl acetal resin or modified polyvinyl acetal resin used in the present invention is generally combined with polyvinyl alcohol or modified polyvinyl alcohol in an aqueous solution, an alcohol solution, a mixed solution of water / alcohol, a dimethyl sulfoxide (DMSO) solution, or the like. It is synthesized by reacting various aldehydes with an acid catalyst, but can also be synthesized by adding an acid catalyst and an aldehyde to a polyvinyl acetate solution or an alcohol solution of modified polyvinyl acetate.

As the aldehyde, any aldehyde can be used as long as it can be acetalized, such as formaldehyde, acetaldehyde, butyraldehyde and propylaldehyde. In particular, it is preferable to use butyl aldehyde and acetaldehyde alone, or to use butyl aldehyde and acetaldehyde together.

The acid catalyst is not particularly limited, and any of an organic acid and an inorganic acid can be used. Examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, and hydrochloric acid. In order to stop the above synthesis reaction, alkali neutralization is usually performed. As the alkali used at this time, for example, sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogen carbonate, Potassium carbonate, potassium bicarbonate and the like can be mentioned.

The amount of halide remaining in the polyvinyl acetal resin or the modified polyvinyl acetal resin of the present invention is preferably 100 ppm or less, more preferably 5 ppm or less.
It is 0 ppm or less. 100 pp residual halide
If it exceeds m, it becomes a substance producing photosensitive silver halide, lowers the preservability of the coating solution, and may cause deterioration of the raw preservability of the film and fogging. As a method for reducing the residual halide amount to 100 ppm or less, for example, a non-halogenous catalyst is selected as a catalyst used for acetalization, or when a halogenous catalyst is used, water, water / alcohol mixture is used. A method of purifying by a washing operation with a solution or the like, and removing it to a specified amount or less, and the like.

The amount of the alkaline substance remaining in the polyvinyl acetal resin or the modified polyvinyl acetal resin used in the present invention is preferably 0.01% by weight or less, more preferably 0.005% by weight or less. If the amount of the remaining alkaline substance exceeds 0.01% by weight, the pot life of the coating solution may be reduced, and the raw preservability of the film may be reduced. As a method for adjusting the amount of the remaining alkaline substance to 0.01% by weight or less, for example, excess alkali after neutralization in the synthesis of a polyvinyl acetal resin or a modified polyvinyl acetal resin is mixed with water or a mixed solution of water / alcohol. A washing method and the like can be mentioned. When a volatile alkali is used, a method of removing to a prescribed amount or less by drying and the like can be mentioned.

In the acetalization reaction of polyvinyl alcohol or modified polyvinyl alcohol with an aldehyde, usually, in order to prevent oxidation of the aldehyde or to prevent oxidation of the obtained resin and to improve heat resistance, the reaction system or the resin system is oxidized. Although an antioxidant is added, in the synthesis of the polyvinyl acetal resin or the modified polyvinyl acetal resin of the present invention, an antioxidant such as a hindered phenol type, a bisphenol type, or a phosphoric acid type which is usually used as an antioxidant is used. do not do. When such an antioxidant is used, it remains in the polyvinyl acetal resin or the modified polyvinyl acetal resin, causing a decrease in the pot life of the coating solution, a decrease in the raw preservability of the raw film, etc. The clarity of the tone may be impaired.

When using a modified polyvinyl acetal resin having a modifying group in the side chain of the polyvinyl acetal resin,
The modifying group, -COOM, -CH ₂ COOM, -S
O ₃ M, -OSO ₃ M, -PO (OM) ₂ , -P (=
O) (R) (OM), at least one hydrophilic group selected from the group consisting of tertiary amines and quaternary ammonium salts is used. Here, M is H, Li, Na or K
And R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. Examples of the carboxyl group include acrylic acid, maleic acid, and itaconic acid. The alkyl group preferably has 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, an isopropyl group, a butyl group, a t-butyl group, and a cyclohexyl group. As the tertiary amine, for example, trimethylamine, triethylamine,
Triethanolamine, tripropylamine, tributylamine and the like can be mentioned.

A method for obtaining such a modified polyvinyl acetal resin is described in, for example, JP-A-2-220221.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-205, a method in which a unit having a hydrophilic group is coexisted at a position where a main chain is formed in advance, and a hydrophilic group is formed using a hydroxyl group of an alcohol-type unit after formation of the main chain. Is adopted.

The ratio of the modifying group in the modified polyvinyl acetal resin is 0.1 to 5 mol%. When the ratio of the modifying group is less than 0.01 mol%, the effect of introducing the hydrophilic group, that is, the effect of improving the dispersibility of the organic silver salt cannot be obtained. Conversely, when the proportion of the modifying group exceeds 5 mol%, not only the effect of improving the dispersibility of the organic silver salt is saturated, but also the solubility in the solvent after acetalization is reduced.

Thus, the polyvinyl acetal resin for a heat-developable photosensitive material and the modified polyvinyl acetal resin for a heat-developable photosensitive material of the present invention are obtained. A heat-developable photosensitive material is produced using such a polyvinyl acetal resin and a modified polyvinyl acetal resin. The composition of the heat developable photosensitive material is the same as that of the conventional heat developable photosensitive material except that the above-mentioned polyvinyl acetal resin and modified polyvinyl acetal resin are used. For example, an organic silver salt, a reducing agent, and if necessary, a small amount of a photosensitive silver halide or a silver halide forming component, and other additives are blended with the above-mentioned polyvinyl acetal resin or modified polyvinyl acetal resin. The weight ratio of the polyvinyl acetal resin or the modified polyvinyl acetal resin to the organic silver salt is preferably 1:10 to 10: 1, more preferably 1: 5 to 5: 1.

The organic silver salt is a colorless or white silver salt which is relatively stable to light, and is 80% in the presence of a light-sensitive silver halide.
There is no particular limitation as long as it reacts with a reducing agent to generate silver when heated to a temperature of not less than ° C.

Examples of the organic silver salts include silver salts of organic compounds having a mercapto group, a thione group or a carboxyl group, and benzotriazole silver. Specifically, silver salts of compounds having a mercapto group or a thione group, silver salts of 3-mercapto-4-phenyl1,2,4-triazole, silver salts of 2-mercapto-benzimidazole, 2-mercapto-5 A silver salt of aminothiazole,
Silver salt of dithiocarboxylic acid such as silver salt of 1-phenyl-5-mercaptotetrathiazole, silver salt of 2-mercaptobenzothiazole, silver salt of thioglycolic acid, silver salt of dithioacetic acid, thioamide silver, silver thiopyridine Silver salt of dithiohydroxybenzol, silver salt of mercaptotriazine, silver salt of mercaptooxadiazole, silver salt of aliphatic carboxylic acid: silver caprate, silver laurate, silver myristate, silver palmitate, silver stearate, behen Silver acid, silver maleate, silver fumarate, silver tartrate, silver furoate, silver linoleate, silver oleate, silver hydroxystearate, silver adipate, silver sebacate, silver succinate, silver acetate, silver butyrate, camphor Silver carboxylate, silver thionate carboxylate, aliphatic carboxylate having a thioether group, tetrazaine Down the silver salt, S-2-aminophenyl silver thiosulfate, metal-containing amino alcohol, and an organic acid metal chelate.

Of the above organic silver salts, silver salts of aliphatic carboxylic acids are preferred, and silver behenate is more preferred. The particle size of the organic acid silver salt has a diameter of 0.01 to
It is preferably 10 μm, more preferably 0.1 to 5 μm.

In some cases, photosensitive silver halide is brought into catalytic contact with the organic silver salt. In this case, for example, a part of the organic silver is formed into silver halide by applying a silver halide forming component to a solution or dispersion of an organic silver salt prepared in advance or a film material containing the organic silver salt. And the like.

The photosensitive silver halide forming component is not particularly limited as long as it acts on an organic silver salt to form a silver halide. It is preferably used in an amount of 0.0005 to 0.2 part by weight, more preferably 0.01 to 0.2 part by weight.

In the heat-developable photosensitive material, a reducing agent is used together with the organic silver salt. Such a reducing agent is not particularly limited and is appropriately selected depending on the organic silver salt used in combination. For example, substituted phenols, bisphenols, naphthols, bisnaphthols, polyhydroxybenzenes, di- or polyhydroxynaphthalenes , Hydroquinone monoethers, ascorbic acid or derivatives thereof, reducing saccharides, aromatic amino compounds, hydroxyamines, hydrazines and the like. Among them, a photodecomposable reducing agent is preferably used, and a thermally decomposable reducing agent is also used. Further, a compound which promotes photolysis can be used in combination, and a coating agent for inhibiting the reaction between silver halide and a reducing agent can be used in combination.

As a method for preparing a heat-developable photosensitive material using the polyvinyl acetal resin or the modified polyvinyl acetal resin of the present invention, for example, a polyvinyl acetal resin or a modified polyvinyl acetal resin, an organic silver salt,
After dispersing the reducing agent and the solvent in a ball mill, if necessary, further silver halide or a silver halide forming component,
A method of adding various additives and dispersing them with a ball mill to prepare them may be used.

As the above-mentioned solvent, those which dissolve a polyvinyl acetal resin or a modified polyvinyl acetal resin and have almost no water content are preferably used. Among them, ketones and esters are preferable, and more preferably,
Diethyl ketone, methyl ethyl ketone, ethyl acetate and the like. When using ethanol, normal propyl alcohol, isopropyl alcohol, etc. as the solvent,
It is preferable to use a dehydrated one. The obtained dispersion is applied onto a support so that the organic silver salt is in a specified amount, and the solvent is evaporated to obtain a heat developable photosensitive material. In addition, the organic silver salt and the reducing agent may be mixed together in a polyvinyl acetal resin or a modified polyvinyl acetal resin, and may be formed on a support in a single layer. The reducing agent and each separately blended in polyvinyl acetal resin or modified polyvinyl acetal resin,
These may be separately formed in two layers on the support.

As the support, for example, a plastic film such as polyethylene terephthalate, polycarbonate, polyethylene, polyvinyl acetal, cellulose ester, cellulose triacetate, nitrocellulose, polyethylene naphthalate and the like, and a metal plate such as glass, paper and aluminum plate are used. Can be

The silver coated on the above-mentioned support was
It is preferably used in an amount of 0.1 to 5 g per m ² , and more preferably 0.3 to 3 g. 0.1
g, the image density may be low,
No improvement in image density is observed with the above use.

In the present invention, when a black image is formed with silver, a color tone agent may be added as an additive. When a color image is formed, a color coupler, a leuco dye and the like may be added. Further, a sensitizer or the like may be added as the case requires.

The polyvinyl acetal resin for a heat-developable photosensitive material, the modified polyvinyl acetal resin for a heat-developable light-sensitive material, and the heat-developable photosensitive material of the present invention have the above-mentioned constitution, and thus, the photosensitive property due to the generation of halide is obtained. , An abnormal growth reaction of the silver salt is suppressed, and a decrease in the pot life of the coating solution due to impurities and a decrease in the raw storage stability of the sheet are suppressed.

When a polyvinyl acetal resin into which an acetoacetal moiety is introduced is used, the dispersibility of the silver salt is improved, and the heat melting property, cooling curability, and the like become sharp.
It is possible to precisely control the nucleus growth of the silver salt, and as a result, the sharpness of the image and the gradation portion is improved. Furthermore,
When a modified polyvinyl acetal resin is used, the dispersibility of the silver salt is further improved by the action of the modifying group comprising a hydrophilic group, and the sharpness of an image and a gradation portion is improved.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. (Example 1) 100 g of polyvinyl alcohol having a polymerization degree of 500 and a saponification degree of 98% was heated and dissolved in 700 g of distilled water, kept at 20 ° C, and 29 g of 35% hydrochloric acid was added thereto.
Further, 14 g of butyraldehyde was added. Next, 12 ° C
Then, 64 g of butyraldehyde was added. After the resin was precipitated, the mixture was kept for 30 minutes, and then 108 g of hydrochloric acid was added, the temperature was raised to 30 ° C., and the mixture was kept for 10 hours. After the completion of the reaction, the solution was washed with distilled water, and sodium hydroxide was added to the water-washed polyvinyl butyral resin dispersion to adjust the pH of the solution to 7. The solution was kept at 50 ° C. for 10 hours and then cooled.
At this time, the pH of the solution was 6.7.

Next, the solution was washed with 100 times the amount of distilled water with respect to the solid content, then the solution was kept at 50 ° C. for 5 hours, washed with 10 times the amount of distilled water, dehydrated, and dried. . The polyvinyl butyral resin thus obtained had a residual hydroxyl group content of 21 mol% and a residual acetyl group content of 1.7 mol%. The residual chlorinated product amount is 50p
pm, the amount of residual alkaline substance was 0.002% by weight.

The measurement of the residual amount of chlorine ions was carried out by the following method. Pretreatment (pyrohydrolysis method): Approximately 0.3 g of a polyvinyl butyral resin sample was weighed into a magnetic boat, gradually inserted into a quartz tube in a tubular electric furnace heated to 1250 ° C., and oxygen gas passed through water vapor ( (0.5 L / min) and heated. The generated gas was absorbed into an absorbing solution (2.25 mM Na ₂ CO ₃ -2.8 mM N).
aHCO ₃ ) (about 30 minutes). 10 absorption liquids
0 ml constant solution and ion chromatography (DONEX
DX-500). The blank test was similarly operated using only the magnetic boat.

The amount of the residual alkaline substance was measured by a neutralization titration method. As a sample, 1 g of a polyvinyl butyral resin was accurately weighed to the order of 1 mg in a common ground Erlenmeyer flask, and dissolved by adding 30 ml of ethanol. Three drops of the phenolphthalein solution were added to the solution after dissolution, and the solution was titrated with a 0.02 mol / L hydrochloric acid solution until the red color disappeared. The amount of potassium hydroxide equivalent to the amount of hydrochloric acid added to the sample was calculated based on the weight of the resin, and the amount was defined as the amount of residual alkaline substance.

5 g of silver behenate and 5 of polyvinyl butyral
g and 40 g of diethyl ketone were mixed in a ball mill for 24 hours, 0.2 g of N-lauryl-1-hydroxy-2-naphthamide was further added, and the mixture was pulverized again in a ball mill to obtain a coating solution. The obtained coating solution was placed under an indoor fluorescent lamp at room temperature for 3 days, and the coloring of the solution was observed. As a result, there was no change in white color.

The above coating solution was applied on a polyester substrate so that the thickness after drying was 10 μm, and dried.
0.5 g of N, N-dimethyl-p-phenylenediamine sulfate, 2 g of polyvinylpyrrolidone,
Thickness after drying a solution consisting of 30 ml of methanol is 1μ
m and dried.

The photosensitive film thus obtained was exposed through a gradation pattern film with high-pressure mercury of 250 watts at a distance of 20 cm for 0.3 seconds, and then heated for 5 seconds using a hot plate at 120 ° C. A good pattern image of cyan color was obtained. The resulting image showed little change in pattern contrast when exposed to white light.

Example 2 Remaining halide amount 90 pp
A coating solution was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin of m was used to prepare a photosensitive film. Coloring of the obtained coating solution and image change of the film after exposure of the photosensitive film hardly occurred.

(Example 3) Amount of residual alkaline substance 0.0
A coating solution was prepared in the same manner as in Example 1 except that a 09% polyvinyl butyral resin was used, and a photosensitive film was produced. Coloring of the obtained coating solution and image change of the film after exposure of the photosensitive film hardly occurred.

Example 4 A coating solution was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin having a butyralization degree of 69 mol% was used, to prepare a photosensitive film. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred.

Example 5 A coating solution was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin having a residual acetyl group content of 11 mol% and a residual hydroxyl group content of 21 mol% was used to prepare a photosensitive film. did. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred.

[0056]

(Example 7) Degree of polymerization 500, degree of saponification 98
132 g of polyvinyl alcohol was dissolved in 1600 g of distilled water by heating, and then kept at 20 ° C., 110 g of 35% hydrochloric acid was added, and 30 g of acetaldehyde was further added. Next, the mixture was cooled to 12 ° C., and 40 g of butyraldehyde was added.
Was added. After the resin was precipitated, the temperature was maintained for 30 minutes, and then the temperature was raised to 60 ° C. and maintained for 4 hours. After the completion of the reaction, the resultant was washed with distilled water, and the pH of the solution was adjusted to 8 by adding sodium bicarbonate to the washed vinyl acetal resin dispersion.
The solution was kept at 70 ° C. for 5 hours and then cooled. The pH of the solution at this time was 8.

After the solution was washed again with 100 times the volume of distilled water with respect to the solid content, the solution was kept at 50 ° C. for 5 hours, washed with 10 times the volume of distilled water, dehydrated, and dried.
The residual hydroxyl group content of the polyvinyl acetal resin thus obtained was 24 mol%, the residual acetyl group content was 1.5 mol%, and the degree of acetoacetalization was 39 mol% (the ratio in all acetalized portions was 52.3%. ) And the butyral degree was 35.5 mol%. The amount of residual chlorinated product is 2
0 ppm and the amount of residual alkaline substance was 0.002% by weight. In addition, the obtained coating solution remains white,
The resulting image on the photosensitive film has almost no change in pattern contrast even when exposed to white light, and the obtained gradation pattern has a density of about 4% in the thinnest color gradation part compared to the original pattern. Was only getting darker.

(Example 8) Amount of residual halide is 80 pp
A coating solution was prepared in the same manner as in Example 7 except that a polyvinyl acetal resin of m was used, to prepare a photosensitive film. Coloring of the resulting coating solution and image change of the film after exposure of the photosensitive film hardly occurred. The obtained gradation pattern is 5 in the lightest color gradation part.
Only the concentration was increased by about%.

Example 9 Amount of residual alkaline substance 0.0
A coating solution was prepared in the same manner as in Example 7, except that a 09% by weight polyvinyl acetal resin was used, to prepare a photosensitive film. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred.
Further, the obtained tone pattern also had only a density of about 5% in the lightest color tone portion.

Example 10 Degree of acetoacetalization 74
A coating solution was prepared in the same manner as in Example 7 except that a polyvinyl acetal resin of mol% (the ratio of the acetoacetalized portion to the total acetalized portion was 100%) was used to prepare a photosensitive film. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred. Further, the obtained gradation pattern had a sharpness equal to or higher than that of Example 7, and the density of the lightest color gradation part was almost the same as that of the pattern original plate.

Example 11 Residual acetyl group content 11 mol%, residual hydroxyl group content 24 mol%, degree of acetoacetalization 6
A coating solution was prepared in the same manner as in Example 7 except that a polyvinyl acetal resin of 5 mol% (the ratio of the acetoacetalized portion to the entire acetalized portion was 100%) was used to prepare a photosensitive film. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred. Further, the obtained tone pattern had a sharpness equal to or higher than that of Example 7, and the density of the lightest color tone portion was almost equal to that of the pattern original plate.

(Example 12) Degree of polymerization: 500, residual hydroxyl group content: 22 mol%, residual acetyl group content: 1.5 mol%, total acetalization degree: 76.5 mol%, acetoacetalization degree: 20
Coating was carried out in the same manner as in Example 7 except that a polyvinyl butyral resin having a mol% (the ratio of the acetoacetalized portion to the entire acetalized portion was 26%), a butyralization degree of 56.5 mol%, and a residual halide amount of 20 ppm was used. A working solution was prepared to prepare a photosensitive film. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred. In the obtained gradation pattern, the sharpness of the gradation part is slightly inferior to that of the seventh embodiment, and the density of the lightest color gradation part is about 10% higher than that of the pattern original. The pattern change was slightly larger.

(Example 13) Degree of polymerization: 500, degree of saponification: 9
After heating and dissolving 132 g of 7% itaconic acid-modified polyvinyl alcohol in 1600 g of distilled water, the temperature was maintained at 20 ° C.
To this, 110 g of 35% hydrochloric acid was added, then cooled to 12 ° C. and 80 g of butyraldehyde was added. After the resin is precipitated, the temperature is maintained for 30 minutes, and then the temperature is raised to 30 ° C. for 7 minutes.
Time kept. After completion of the reaction, the solution was washed with distilled water, and sodium hydroxide was added to the water-washed modified polyvinyl butyral resin dispersion to adjust the pH of the solution to 8. Solution at 60 ° C
And then cooled for 5 hours. At this time, the pH of the solution was 8
Met.

Next, the solution was washed with distilled water 100 times the solid content, and then the solution was kept at 50 ° C. for 5 hours, washed with 10 times the volume of distilled water, dehydrated, and dried. . The amount of residual hydroxyl groups of the itaconic acid-modified polyvinyl butyral resin thus obtained was 21 mol%, the amount of residual acetyl groups was 1.5 mol%, and the degree of butyralization was 25.5.
Mol%. In addition, the residual chlorinated product amount is 20 ppm,
The amount of the remaining alkaline substance was 0.002% by weight.

5 g of silver behenate, 5 g of itaconic acid-modified polyvinyl butyral and 40 g of diethyl ketone were mixed in a ball mill for 24 hours, 0.2 g of N-lauryl-1-hydroxy-2-naphthamide was added, and the mixture was pulverized again in a ball mill. To obtain a coating solution. The obtained coating solution was placed under an indoor fluorescent lamp at room temperature for 3 days, and the coloring of the solution was observed. As a result, there was no change in white color.

The above coating solution was applied on a polyester substrate so that the thickness after drying was 10 μm, and dried.
0.5 g of N, N-dimethyl-p-phenylenediamine sulfate, 2 g of polyvinylpyrrolidone,
Thickness after drying a solution consisting of 30 ml of methanol is 1μ
m and dried.

The photosensitive film thus obtained was exposed through a gradation pattern film with a 250-watt high-pressure mercury lamp at a distance of 20 cm for 0.3 seconds, and then heated for 5 seconds using a hot plate at 130 ° C. to obtain cyan. A good color pattern image was obtained. The resulting image showed little change in pattern contrast when exposed to white light. Further, the density of the whitest gradation part was only 2% higher than that of the original plate. Also, the boundary of the gradation part was clear.

(Example 14) The amount of residual halide was 80
The same itaconic acid-modified polyvinyl butyral resin as in Example 13 was used except that the content was ppm. Otherwise, the procedure of Example 13 was repeated to prepare a coating solution, and a photosensitive film was prepared. Coloring of the obtained coating solution, and
Image change of the film after exposure of the photosensitive film hardly occurred. The density of the obtained tone pattern was also about 3% higher than that of the pattern original in the lightest color tone portion.

Example 15 The same itaconic acid-modified polyvinyl butyral resin as in Example 13 was used except that the amount of the remaining alkaline substance was 0.009%. Otherwise, the procedure of Example 13 was repeated to prepare a coating solution, and a photosensitive film was prepared. Coloring of the obtained coating solution and image change of the film after exposure of the photosensitive film hardly occurred. Further, the gradation pattern is the same as that of Example 14
Was equivalent to

Example 16 The degree of acetoacetalization was 7
Example 13 except that it was 4 mol% (the ratio of the acetoacetalized portion to the total acetalization degree was 100%).
The same itaconic acid-modified polyvinyl butyral resin was used. Otherwise, the procedure of Example 13 was repeated to prepare a coating solution, and a photosensitive film was prepared. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred. The sharpness of the gradation part was equal to or higher than that of Example 13, and the density of the lightest color gradation part of the gradation pattern was almost the same as that of the pattern original plate.

Example 17 Residual acetyl groups were 11 mol%, residual hydroxyl groups were 24 mol%, and acetoacetalization degree was 6
Example 13 except that it was 5 mol% (the ratio of the acetoacetalized portion to the total acetalization degree was 100%).
The same itaconic acid-modified polyvinyl butyral resin was used. Otherwise, the procedure of Example 13 was repeated to prepare a coating solution, and a photosensitive film was prepared. Coloring of the obtained coating solution and image change after exposure of the photosensitive film hardly occurred. Further, the image of the gradation pattern was the same as that of Example 16.

(Comparative Example 1) Amount of residual halide 150p
A coating solution was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin of pm was used to prepare a photosensitive film. The obtained coating solution was slightly colored, and the obtained photosensitive film also slightly fogged after exposure.

(Comparative Example 2) 2,2'-
Methylene bis (4-ethyl-6-tert-butylphenol) was converted to 500 pp in polyvinyl butyral resin.
A coating solution was prepared in the same manner as in Comparative Example 1 except that the addition was performed so as to obtain m, thereby preparing a photosensitive film. The obtained coating solution was greatly colored, and the obtained photosensitive film was also frequently fogged after exposure.

Comparative Example 3 A coating solution was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin having a residual hydroxyl group content of 37 mol% and a residual acetyl group content of 1.5 mol% was used. Was prepared. The obtained coating solution was slightly colored, and the obtained photosensitive film was slightly fogged after exposure.

Comparative Example 4 A coating solution was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin having a residual hydroxyl group content of 10 mol% and a residual acetyl group content of 30 mol% was used to prepare a photosensitive film. did. Although the obtained coating solution was not colored, when the obtained photosensitive film was layered and stored, blocking occurred at 35 ° C., and the resulting exposed image had sharpness at the boundary surface. lost.

(Comparative Example 5) 2,2'-
Methylene bis (4-ethyl-6-tert-butylphenol) was added to a polyvinyl acetal resin at 500 pp.
A coating solution was prepared in the same manner as in Example 7, except that m was added, to prepare a photosensitive film. The obtained coating solution was greatly colored, and the photosensitive film was frequently fogged after exposure.

[0078]

(Comparative Example 6 ) 2,2'-methylenebis (4-ethyl-6-tert-butylphenol) was added as an antioxidant so as to be 500 ppm in a polyvinyl butyral resin.
Otherwise, a coating solution was prepared in the same manner as in Example 13,
A photosensitive film was produced. The obtained coating solution was greatly colored, and the obtained photosensitive film was also frequently fogged after exposure.

(Comparative Example 7 ) The amount of residual hydroxyl groups was 37 mol% and the amount of residual acetyl groups was 1.5
The same itaconic acid-modified polyvinyl butyral resin as in Example 13 was used except that it was mol%. Otherwise, the procedure of Example 13 was repeated to prepare a coating solution, and a photosensitive film was prepared. The obtained coating solution was slightly colored, and the obtained photosensitive film was slightly fogged after exposure.

(Comparative Example 8 ) The same itaconic acid-modified polyvinyl butyral resin as in Example 13 was used except that the residual hydroxyl group content was 20 mol% and the residual acetyl group content was 28 mol%. Other than that,
A coating solution was prepared in the same manner as in Example 13 to prepare a photosensitive film. The obtained coating solution had poor solubility. Neither the obtained photosensitive film nor the image after exposure was sharp at the boundary.

[0082]

According to the present invention, the polyvinyl acetal resin for a photothermographic material, the modified polyvinyl acetal resin for a photothermographic material and the photothermographic material according to the present invention have the above-mentioned constitution, and can be used to store a coating solution. In addition, the resulting photosensitive film has excellent storage stability after exposure, and has excellent image characteristics.

Further, the dispersibility of the silver salt is improved,
The cooling hardenability and the like become sharp, and the nucleus growth of the silver salt can be controlled with high accuracy. As a result, the sharpness of the image and the gradation portion is improved.

Claims (7)

(57) [Claims] 1. A polyvinyl acetal resin synthesized by an acetalization reaction between polyvinyl alcohol and an aldehyde, wherein the degree of polymerization is in the range of 200 to 3000, and when the acetal group is counted as one side chain,
And the acetal group is replaced with two acetalized hydroxyl groups.
In all cases, the ratio of the residual acetyl group was 0 to 25 mol%, and the ratio of the residual hydroxyl group was 17 to 35.
A polyvinyl acetal resin for a heat-developable photosensitive material, wherein the polyvinyl acetal resin contains no antioxidant and has a residual halide content of 100 ppm or less. 2. A polyvinyl acetal resin synthesized by an acetalization reaction between polyvinyl alcohol and butyraldehyde, wherein the degree of polymerization is in the range of 200 to 3000 and the acetal group is counted as one side chain.
And two waters with acetalized acetal groups
When counted as an acid group, in each case, the ratio of the residual acetyl group was 0 to 25 mol%, and the ratio of the residual hydroxyl group was 17%.
A polyvinyl acetal resin for a heat-developable photosensitive material, characterized by containing no antioxidant and having a residual halide content of 100 ppm or less. 3. A polyvinyl acetal resin synthesized by an acetalization reaction of polyvinyl alcohol, butyraldehyde and acetaldehyde, wherein the degree of polymerization is 2
In the range of 00 to 3000, with the acetal group on one side
When counted as a chain and when acetal group is acetal
If it is counted as two hydroxyl groups,
However, the proportion of the residual acetyl group is in the range of 0 to 25 mol%, the proportion of the residual hydroxyl group is in the range of 17 to 35 mol%, and the proportion of the portion acetalized by acetaldehyde in the entire acetalized portion is in the range of 30 to 100%. A polyvinyl acetal resin for a heat-developable photosensitive material, which does not contain an antioxidant and has a residual halide content of 100 ppm or less. 4. A modified polyvinyl acetal resin synthesized by an acetalization reaction between polyvinyl alcohol and an aldehyde and having the following modifying group in a side chain, wherein the degree of polymerization is in the range of 200 to 3000 and the acetal group is 1
When counted as two side chains, and the acetal group
When counted as two tarylated hydroxyl groups,
In the above, the ratio of the residual acetyl group is 0 to 25 mol%,
The ratio of residual hydroxyl groups is in the range of 17 to 35 mol%, the ratio of modifying groups is in the range of 0.1 to 5 mol%, does not contain an antioxidant, and the amount of residual halide is 100 ppm or less. A modified polyvinyl acetal resin for a heat-developable photosensitive material, comprising: Here, the modifying group is -COOM,
_{-CH 2 COOM, -SO 3 M,} -OSO 3 M, -PO
(OM) ₂ , -P (ＯO) (R) (OM), at least one hydrophilic group selected from the group consisting of tertiary amines and quaternary ammonium salts (where M is H,
Represents Li, Na or K, and R represents a hydrogen atom or a carbon number of 1 to
Represents 20 alkyl groups. ) 5. The polyvinyl acetal for a heat-developable photosensitive material according to claim 1, wherein the amount of the remaining alkaline substance in the polyvinyl acetal resin is 0.01% by weight or less. resin. 6. The modified polyvinyl acetal resin for a heat-developable photosensitive material according to claim 4, wherein the amount of residual alkaline substance in the modified polyvinyl acetal resin is 0.01% by weight or less. 7. A heat development method comprising using the polyvinyl acetal resin for a heat-developable photosensitive material according to claim 1 or a modified polyvinyl acetal resin for a heat-developable light-sensitive material. Photosensitive material.