JP2002201215A - Polyvinyl acetal resin for heat developing photosensitive material and heat developing photosensitive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl acetal resin for a heat developing photosensitive material having excellent image properties without causing poor pot life of a coating solution, discoloration of the heat developing photosensitive material, fogging, poor gradation, and poor sensitivity of images, poor storage stability of green films and the like, and a heat developing photosensitive material. SOLUTION: The polyvinyl acetal resin for a heat developing photosensitive material is synthesized by the acetalization reaction of a polyvinyl alcohol with an aldehyde, has a degree of polymerization of 200-3,000, a ratio of the residual acetyl group of 0-25 mol% when an acetal group is counted as two acetalized hydroxy groups, a ratio of the residual hydroxy group of 17-35 mol%, a water content of <=2.5 wt.%, a residual aldehyde content of <=10 ppm and contains no antioxidant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl acetal resin for a photothermographic material and a photothermographic material.

[0002]

2. Description of the Related Art A heat-developable photosensitive material mainly comprises 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, which has been widely used, has been used as a high quality image forming material because of its excellent photographic properties.However, the work in the development and fixing steps is complicated, and all of the above-mentioned steps are difficult. Since it is a wet process, there is a problem that not only is it troublesome to perform complicated processing operations, but also a large amount of chemical waste liquid is discharged. In order to avoid such problems, a heat developable photosensitive material has been developed so that the development process is performed from a wet process to a heat development process, and some of the materials have been put to practical use.

[0003] For example, Japanese Patent Publication No. 43-4924 discloses an organic silver salt having silver ions associated with each other in a molecule and a silver halide in catalytic contact with the silver ions. And a heat-developable photosensitive sheet material comprising a mild reducing agent. A photosensitive material comprising these organic silver salt, silver halide and a mild reducing agent is placed in a transparent film as a support itself or in a fiber product having almost no binder to form a heat-developable photosensitive sheet material. Paper or plastic, formed or placed in a coating layer of a film-forming binder such as, for example, polyvinyl butyral, polymethyl methacrylate, cellulose acetate, polyvinyl acetate, cellulose acetate propionate, cellulose butyrate. It is described in the above-mentioned publication that a heat-developable photosensitive sheet material is formed by coating on a heat-resistant support such as a film, a metal foil, and a glass plate, and polyvinyl acetal is used as the film-forming binder. Resin is used as the optimal one.

However, the conventional polyvinyl acetal resin contains a small amount of impurities due to the production method, and the film forming binder itself has photosensitivity due to the influence of these impurities, and the prepared film forming binder is prepared. Unnecessarily colored coating layer, or fog, poor gradation, insufficient sensitivity,
This is likely to cause defects such as poor storage stability of the photosensitive sheet material before image formation. In addition, depending on the glass transition temperature of the polyvinyl acetal resin, the film undergoes thermal deformation during thermal development, and the coated image has fog, poor gradation, insufficient sensitivity, and cracks during handling of the film. There was a case.

As means for solving the problem of deteriorating the image characteristics, for example, JP-A-49-52626 discloses a thermosensitive photographic composition containing a photosensitive silver halide, a reducing agent and a silver salt oxidizing agent. Discloses that a stable image can be formed without using an independent stabilizer or a stabilizer precursor by using a thione compound represented by the general formula as a silver salt oxidizing agent. However, the use of the above-mentioned thione compound as a silver salt oxidizing agent cannot solve the above-mentioned problems of conventional polyvinyl butyral.

Further, in order to improve image characteristics, it is necessary to disperse silver salt of fatty acid, organic reducing agent, photosensitive silver halide and the like more uniformly. When a polyvinyl acetal resin having a low degree of polymerization is used, the strength of the obtained coating film is weakened, problems such as fogging occur, and conversely, when a polyvinyl acetal resin having a high degree of polymerization is used to satisfy the coating film strength. It becomes difficult to uniformly disperse the silver salt of the fatty acid, the organic reducing agent, and the photosensitive silver halide. Further, among the heat-developable photosensitive materials, the heat-developable silver salt film is inferior in the image characteristics, particularly the image density and the sharpness of the gradation portion, to be inferior to the conventional X-ray sensitized film using the wet gelatin, and has a poor thermal property. There is a strong demand for improvement of these image characteristics of developable silver salt films, and for that purpose, it is necessary to strictly control silver nucleus growth during heating.

[0007]

SUMMARY OF THE INVENTION In view of the above, the present invention has been developed in view of the pot life of a coating solution, coloring and fogging of a heat developable photosensitive material, poor gradation, insufficient sensitivity, poor raw storage stability of a film, and the like. An object of the present invention is to provide a polyvinyl acetal resin for a heat developable photosensitive material and a heat developable photosensitive material having excellent image characteristics without generation.

[0008]

The present invention relates to a polyvinyl acetal resin synthesized by an acetalization reaction between polyvinyl alcohol and an aldehyde, the resin having a degree of polymerization of 2 or less.
When the number of acetal groups is counted as two acetalized hydroxyl groups, the ratio of residual acetyl groups is 0 to 25 mol%, and the ratio of residual hydroxyl groups is 17 to 25 mol%.
It is a polyvinyl acetal resin for a photothermographic material which does not contain an antioxidant and has a water content of 2.5% by weight or less, a residual aldehyde content of 10 ppm or less. Hereinafter, the present invention will be described in detail.

The present inventors have conducted intensive studies on the coloring of a heat developable photosensitive material using a polyvinyl acetal resin, and on the causes of fogging, poor gradation, insufficient sensitivity, etc. on an image after coating. The inventors of the present invention have found out the structure and the fact that trace impurities contaminating during the production are the causes, and have completed the present invention. The polyvinyl acetal resin for a photothermographic material according to the first aspect of the present invention is synthesized by an acetalization reaction between polyvinyl alcohol and an aldehyde.

The above acetalization reaction is not particularly limited, and is carried out in a solution such as an aqueous solution, an alcohol solution, a mixed solution of water / alcohol, and a dimethyl sulfoxide (DMSO) solution using an acid catalyst. The polyvinyl alcohol also includes polyvinyl acetate before saponification.

The aldehyde is not particularly limited,
For example, formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde, Examples thereof include 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. These aldehydes may be used alone,
Two or more kinds may be used in combination. Among them, acetaldehyde and butyraldehyde are preferably used.

The acid catalyst is not particularly limited, and includes, for example, organic acids such as acetic acid and p-toluenesulfonic acid; and inorganic acids such as nitric acid, sulfuric acid and hydrochloric acid. Further, the terminator for the acetalization reaction is not particularly limited,
For example, alkali neutralizers such as sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate; alkylene oxides such as ethylene oxide; glycidyl ethers such as ethylene glycol diglycidyl ether; No.

The polymerization degree of the polyvinyl acetal resin for a heat-developable photosensitive material of the first invention is from 200 to 3,000. If it is less than 200, the resulting photothermographic material will not have sufficient coating strength and cracks or the like may be formed when the coating is bent. If it exceeds 3000, it may be added to the photothermographic material. In some cases, the dispersibility of the silver salt is reduced, and the coating properties of the heat-developable photosensitive material obtained by mixing these components are reduced. To give, it is limited to the above range.

A second aspect of the present invention is a polyvinyl acetal resin for a heat-developable photosensitive material in which a low molecular weight polyvinyl acetal resin and a high molecular weight polyvinyl acetal resin are mixed, wherein the degree of polymerization differs by at least 300 or more. It is a polyvinyl acetal resin for photothermographic materials containing two types of polyvinyl acetal resins. Second
The polyvinyl acetal resin for a heat developable photosensitive material of the present invention, at least, it is sufficient that the degree of polymerization contains at least two types of polyvinyl acetal resins differing by 300 or more, furthermore, may contain other polyvinyl acetal resin Good.

The polyvinyl acetal resin for a heat-developable photosensitive material according to the second aspect of the present invention may be a mixture of two or more kinds of polyvinyl acetal resins having different degrees of polymerization of 300 or more. A mixed polyvinyl alcohol obtained by mixing two or more different types of polyvinyl alcohols may be acetalized. If the difference in the degree of polymerization of the two or more kinds of polyvinyl acetal resins or polyvinyl alcohols to be mixed is less than 300, the dispersibility of the silver salt of a fatty acid and the photosensitive silver halide added to the heat developable photosensitive material becomes poor. In addition, fogging may occur in image characteristics or gradation may be deteriorated due to weakening of the strength of the coating film.

In the present specification, the degree of polymerization, the ratio of residual acetyl groups, and the ratio of residual hydroxyl groups of the polyvinyl acetal resin for a photothermographic material of the second invention are apparent values, that is, It means a value when it is considered to be composed of a single composition. For example, when it is composed of two types of polyvinyl acetal resins A and B, it is represented by the following formula. (A1 + B1) logX = A1 · logA2 + B1 · l
ogB2 X: Apparent polymerization degree of blended polyvinyl acetal resin (apparent residual hydroxyl group amount, apparent residual acetyl group amount) A1: Weight of polyvinyl acetal resin A A2: Degree of polymerization of polyvinyl acetal resin A (remaining) B1: Weight of polyvinyl acetal resin B B2: Degree of polymerization of polyvinyl acetal resin B (residual hydroxyl group, residual acetyl group)

The degree of polymerization of the polyvinyl acetal resin for a heat-developable photosensitive material according to the second invention is from 200 to 1,000. When it is less than 200, the strength of the obtained coating film is low, and when the coating film is bent, cracks or the like may be caused.
If it exceeds 000, the dispersibility of the silver salt of a fatty acid and the photosensitive silver halide may be deteriorated, and fog may occur in image characteristics and gradation may be deteriorated. The polyvinyl acetal resin to be mixed, or the degree of polymerization of polyvinyl alcohol is not particularly limited, the degree of polymerization is 200 ~
3000 is preferred.

In the second invention, the aldehyde, acid catalyst and terminator used in the acetalization reaction are the same as those used in the first invention. Usually, in the acetalization reaction, in order to prevent oxidation of the aldehyde of the reaction system, or to prevent oxidation of the generated polyvinyl acetal resin and improve heat resistance,
For example, hindered phenol, bisphenol,
Although an antioxidant such as a phosphoric acid type is added to the reaction system and / or the production system, the antioxidant is not used in the present invention, and the polyvinyl acetal resin for a heat developable photosensitive material of the present invention is an antioxidant. Is not contained. The antioxidant may rather reduce the pot life of the coating solution of the heat-developable photosensitive material, cause a fogged image after coating, or impair the sharpness of the gradation portion.

The polyvinyl acetal resin for a photothermographic material of the present invention has a specific acetalization degree. In the present specification, the degree of acetalization is calculated by a method of counting as two acetalized hydroxyl groups since the acetal group of the polyvinyl acetal resin is formed by acetalization of two hydroxyl groups.

The proportion of residual acetyl groups in the polyvinyl acetal resin for a heat-developable photosensitive material of the present invention is 0 to 25 mol%.
It is. If it exceeds 25 mol%, the resulting heat-developable photosensitive material films are likely to be blocked with each other, and the image is not clear, so that the content is limited to the above range.
Preferably it is 0 to 15 mol%.

The proportion of residual hydroxyl groups in the polyvinyl acetal resin for a photothermographic material of the present invention is 17 to 35 mol%. If it exceeds 35 mol%, the dispersibility of the silver salt added to the heat-developable photosensitive material decreases, and in extreme cases, the silver salt aggregates, and the sensitivity of the resulting heat-developable light-sensitive material decreases. The resulting heat-developable photosensitive material easily absorbs moisture, and the pot life of the heat-developable photosensitive material (coating solution) is reduced. On the other hand, if it is less than 17 mol%, the dispersibility of the silver salt is reduced, and the sensitivity of the resulting heat-developable photosensitive material is reduced. Preferably 19-
30 mol%.

The water content of the polyvinyl acetal resin for a photothermographic material of the present invention is 2.5% by weight or less. 2.
When the amount exceeds 5% by weight, the pot life of the heat-developable photosensitive material (coating solution) decreases, and further, a compound containing an isocyanate group added to strengthen the resulting heat-developable photosensitive material coating film Reacts with a crosslinking agent such as, and strengthening of the coating film by the desired crosslinking becomes insufficient, or becomes impossible in severe cases, and when the added amount of the crosslinking agent is increased in order to remove residual moisture, Since the handling property becomes extremely poor, such as causing fogging, it is limited to the above range. Preferably it is 2.0% by weight or less. 2.5 remaining moisture
Examples of the method for reducing the content to less than the weight percent include a method of removing water to a specified amount or less by a washing operation using water, a mixed solution of water / alcohol, or the like, followed by drying with hot air or the like.

The residual aldehyde content of the polyvinyl acetal resin for a heat developable photosensitive material of the present invention is 10 ppm or less. If it exceeds 10 ppm, the pot life of the heat-developable photosensitive material (coating solution) is reduced, the aldehyde is reduced by a reducing agent contained in the coating solution, and the preservability of the coating solution is reduced. Since the image characteristics are degraded due to the occurrence of fog, it is limited to the above range. These phenomena are
It is considered that the residual aldehyde contaminated in the heat developable photosensitive material (coating solution) is reduced by a reducing agent. The residual aldehyde content is preferably 5 ppm
It is as follows. The means for removing the residual aldehyde contaminating the polyvinyl acetal resin is not particularly limited, and examples thereof include a method of washing with water, a mixed solution of water / alcohol, and the like.

The polyvinyl acetal resin for a heat-developable photosensitive material of the present invention preferably has a glass transition temperature of 55 to 110 ° C. If it exceeds 110 ° C., the resulting coating film will be too hard, causing folds and cracks during handling, fogging on the image of the heat-developable photosensitive material film, insufficient gradation, and insufficient sensitivity. If the temperature is lower than 55 ° C., the coating film becomes soft and may be thermally deformed by heat during thermal development, or the surface of the coating film may be damaged during handling, causing fog or the like due to the scratch. The temperature is more preferably 55 to 100 ° C.

A heat-developable photosensitive material can be produced using the polyvinyl acetal resin for a heat-developable light-sensitive material of the present invention. The photothermographic material is a polyvinyl acetal resin for the photothermographic material of the present invention, an organic silver salt, a reducing agent, a small amount of a photosensitive silver halide or a silver halide forming component, if necessary, a crosslinking agent, It is obtained by blending with other additives. The blending amount of the polyvinyl acetal resin for a heat developable light-sensitive material of the present invention in the above heat developable light-sensitive material is preferably a weight ratio to the organic silver salt (polyvinyl acetal resin: organic silver salt), preferably 1:10 to 10:10. : 1
And more preferably 1: 5 to 5: 1.

The above-mentioned organic silver salt is a colorless or white silver salt which is relatively stable to light. When heated to 80 ° C. or more in the presence of a photosensitive silver halide, it reacts with a reducing agent to react with metallic silver. It is what becomes. Examples of the organic silver salt include 3
Mercaptans such as -mercapto-4-phenyl-1,2,4-triazole, 2-mercapto-5-aminothiazole, 1-phenyl-5-mercaptotetrathiazole, 2-mercaptobenzothiazole, mercaptooxadiazole and mercaptotriazine Silver salts of thioamides such as thioamide, thiopyridine, S-2-aminophenylthiosulfate; aliphatic carboxylic acids, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and maleic acid Dithiocarboxylic acid, thioglycolic acid, aromatic carboxylic acid, such as fumaric acid, tartaric acid, froinic acid, linoleic acid, oleic acid, hydroxystearic acid, adipic acid, sebacic acid, succinic acid, acetic acid, butyric acid, camphoric acid, dithioacetic acid Has acid, thione carboxylic acid and thioether groups Silver salts of organic carboxylic acids such as aliphatic carboxylic acids, etc .; silver salts of imidazoles such as 2-mercaptobenzimidazole; silver salts of triazoles such as benzotriazole; silver salts of tetrazaindene; silver-containing metal amino alcohols And organic acid silver chelate compounds. Among these organic silver salts, silver salts of aliphatic carboxylic acids are preferable, and silver behenate is more preferably used. The particle size of the organic silver salt is preferably 0.01 to 10 μm,
More preferably, it is 0.1 to 5 μm.

The above-mentioned organic silver salt may be brought into catalytic contact with a photosensitive silver halide. The means for contacting the photosensitive silver halide is not particularly limited.For example, a solution or dispersion of an organic silver salt prepared in advance, or a film containing an organic silver salt, a photosensitive silver halide forming component is added. A method in which a part of the organic silver salt is converted to silver halide by the action of the organic silver salt.

The photosensitive silver halide forming component is not particularly limited as long as it acts on an organic silver salt to form silver halide, but preferably contains iodide ions. Examples of the silver halide include silver bromide, silver iodide, silver chloride, silver chlorobromide, silver iodobromide, silver chloroiodide and the like. The amount of the photosensitive silver halide to be added is preferably 0.0005 to 0.2 part by weight, more preferably 0.01 to 0.2 part by weight, based on 100 parts by weight of the organic silver salt.

The reducing agent is not particularly limited and may be appropriately selected according to the kind of the organic silver salt used. Examples thereof include substituted phenols, bisphenols, naphthols, bisnaphthols, polyhydroxy Benzenes, di- or polyhydroxynaphthols, di- or polyhydroxynaphthalenes, hydroquinones, hydroquinone monoethers, ascorbic acid or derivatives thereof, reducing sugars, aromatic amino compounds, hydroxyamines, hydrazines, phenidones, Hindered phenols and the like. Among them, a photodecomposable reducing agent is suitably used, and a thermally decomposable reducing agent is also preferable. More preferably, they are hindered phenols.
The amount of the reducing agent to be added is preferably 0.0001 to 3.0 parts by weight, more preferably 0.01 to 1.0 part by weight, based on 100 parts by weight of the organic silver salt. Furthermore, each of the above-mentioned reactions is controlled by using a photodegradable reducing agent in combination with a photodegradation accelerator, or by using a coating provided to inhibit the reaction between the organic silver salt and the reducing agent. can do.

The method for producing the photothermographic material of the present invention is not particularly limited. For example, a polyvinyl acetal resin for a photothermographic material of the present invention, an organic silver salt, a reducing agent and a solvent are mixed and dispersed in a ball mill. After that, a method of adding a silver halide or a silver halide forming component, and other additives as necessary, and further dispersing to prepare a dispersion liquid may be mentioned.

As the above-mentioned solvent, those which can dissolve the polyvinyl acetal resin for a heat-developable photosensitive material of the present invention and have a small water content are preferably used. These solvents include, for example, diethyl ketone,
Ketones such as methyl ethyl ketone and methyl isobutyl ketone; esters such as methyl acetate, ethyl acetate and propyl acetate;

Next, the resulting dispersion is applied on a support so that the organic silver salt is in a predetermined amount, and the solvent is evaporated, whereby a coating film of a heat-developable photosensitive material is obtained. As described above, the coating film of the heat developable photosensitive material is prepared by blending the polyvinyl acetal resin for a heat developable photosensitive material of the present invention, an organic silver salt and a reducing agent all at once, and forming a layer of the heat developable photosensitive material on a support. Although it may be formed as a coating film of an optical material, an organic silver salt and a reducing agent are separately added to the polyvinyl acetal resin for a heat-developable photosensitive material of the present invention to form a two-layer coating film. Later, both may be laminated. Further, a coating film may be formed on only one surface of the support, or a coating film may be formed on both surfaces of the support.

The support is not particularly restricted but includes, for example, polyolefins such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene and polypropylene; cellulose esters such as polyvinyl acetal, cellulose diacetate and cellulose triacetate; Examples include plastic films made of vinyl chloride resin, chlorinated polypropylene and the like, glass, paper, metal plates made of aluminum and the like.

The amount of silver dispersed in the coating film of the heat developable photosensitive material is preferably from 0.1 to 5.0 g / m ² . 0.
If it is less than 1 g / m ² , the image density will decrease, and even if the density is increased beyond a certain amount, the image density will be saturated and no further improvement will be observed, while on the other hand it will exceed 5.0 g / m ² . No improvement in image density is seen even when used. More preferably, 0.
It is a 3~3.0g / ^{m 2.} Such a heat developable photosensitive material is also one of the present invention. When an image is formed using the heat developable photosensitive material of the present invention, a color tone agent is added as an additive. To form a black image, a black toning agent is added, and to form a color image, a color coupler, a leuco dye and the like are added.
Further, if necessary, a photosensitizer may be added to these heat-developable photosensitive materials.

[0035]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Example 1) <Preparation of polyvinyl acetal resin> 100 g of polyvinyl alcohol having a polymerization degree of 500 and a saponification degree of 98 mol% was added to 7
After heating and dissolving in 00 g of distilled water, the temperature was maintained at 20 ° C., and 29 g of 35% by weight hydrochloric acid was added thereto, followed by 64 g of butyraldehyde. After the acetalized resin starts to precipitate, it is kept in this state for 30 minutes.
An additional 8 g was added, the temperature was raised to 30 ° C., and the reaction was performed for 10 hours. After completion of the reaction, the solid content (resin) was washed with distilled water, the resin after the water washing was redispersed in distilled water, and sodium hydroxide was added to the obtained dispersion to adjust the pH of the solution to 7. . This liquid was heated to 50 ° C., kept in this state for 10 hours, and then cooled to room temperature. Reheated and washed resin,
The solid was washed with 100 times the volume of distilled water. Further, the washed resin was redispersed in distilled water, kept at 50 ° C. for 5 hours, further washed with 100 times the amount of distilled water, dehydrated, and dried to prepare a polyvinyl acetal resin. In addition, the glass transition temperature of the obtained polyvinyl acetal resin was 60 ° C.

The residual acetyl group content, residual hydroxyl group content, residual aldehyde content and water content of the obtained polyvinyl acetal resin, the preservability of the coating solution, the heat developability, the preservability of the developed image and the heat stability were evaluated. Was measured by the following method. The measurement results are shown in Table 1. 1. Residual acetyl group content: The residual acetyl group content is ¹³ C-
It was measured using NMR. 2. Residual hydroxyl group amount: The residual hydroxyl group amount was measured using ¹³ C-NMR. 3. Residual aldehyde amount: The polyvinyl acetal resin was heat-extracted in a heating furnace, and the amount of the aldehyde was measured for the obtained extract using gas chromatography. 4. Moisture content: Measured using a Karl Fischer moisture meter.

<Preparation of Coating Solution for Heat-Developable Photosensitive Material Film> 5.0 g of the above polyvinyl butyral resin, 5.0 g of silver behenate and 40 g of methyl ethyl ketone were mixed for 24 hours in a ball mill, and further N-lauryl-1-. 0.2 g of hydroxy-2-naphthamide was added, and the mixture was pulverized and mixed again with a ball mill to prepare a coating solution.

<Preservability of Coating Solution for Thermally Developable Photosensitive Material Film> The obtained coating solution was placed under an indoor fluorescent lamp at room temperature for 3 days, and the presence or absence of coloring of the coating solution was observed. No change was observed in the whiteness of the coating solution before and after the fluorescent lamp exposure. The preservability of the coating solution was evaluated by visually observing a change in the color of the solution. A sample in which the color of the solution did not change was evaluated as ○, a slightly colored one was evaluated as Δ, and a greatly colored one was evaluated as ×.

<Preparation of heat-developable photosensitive material film> The above coating solution was applied on a support made of a polyester film so that the thickness after drying was 10 μm, and dried. On a coated surface, a solution comprising 0.5 g of N, N-dimethyl-p-phenylenediamine / lead sulfate, 2 g of polyvinylpyrrolidone and 30 ml of methanol has a thickness of 1 after drying.
It was applied to a thickness of μm and dried. Thus, a heat developable photosensitive material film was prepared.

<Heat developability of heat developable photosensitive material film>
In order to evaluate the heat developability of the obtained heat developable photosensitive material film, a 250-watt high-pressure mercury lamp was exposed through a gradation pattern film from a distance of 20 cm for 0.3 mm second, and then a hot plate at 120 ° C. was exposed. And developed by heating for 5 seconds to obtain a good cyan pattern image. At this time, those with no fog and good sharpness were rated as ○, those with some fog and poor sharpness were rated as Δ, and those with many fogs and poor sharpness were rated as x.

<Storability of Developed Image> Next, to confirm the storability of the developed image, it was exposed to white light for 24 hours.も の indicates that no image pattern contrast disturbance was observed, △ indicates that the image pattern contrast was slightly disturbed, and X indicates that the image pattern contrast was significantly disturbed.
Was evaluated.

<Heat Stability> A heat-developable photosensitive material film obtained as described above was coated on a stainless steel plate at 100 ° C. having irregularities formed at intervals of 1 mm in height and 1 mm in width. After being placed as described above, the heat developable photosensitive material film was pressed against the stainless steel plate at a pressure of 100 g / cm ² for 5 seconds. continue,
The heat-developable photosensitive material film was cooled at room temperature, and the coating surface of the heat-developable photosensitive material film was visually observed, and those having no cracks or deformation were evaluated as ○, and those having cracks or deformation were evaluated as x. .

Example 2 Degree of polymerization: 500, degree of saponification: 88
A polyvinyl butyral resin was prepared in the same manner as in Example 1 except that mol% of polyvinyl alcohol was used, and a heat developable photosensitive material film was prepared using the same. The glass transition temperature of the polyvinyl butyral resin was 56 ° C. The prepared polyvinyl butyral resin and the obtained heat-developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, the heat developability, the preservability of the developed image and the heating stability were all good. Table 1 shows the test results and the like.

Example 3 A polyvinyl butyral resin having a degree of polymerization of 240, a residual acetyl group content of 1.5 mol%, a residual hydroxyl group content of 27 mol%, a residual aldehyde content of 3 ppm and a water content of 1.5 wt% was used. Except for the above, a heat developable photosensitive material film was produced in the same manner as in Example 1. In addition,
The glass transition temperature of the polyvinyl butyral resin is 62
° C. The prepared polyvinyl butyral resin and the obtained heat-developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, the heat developability, the preservability of the developed image and the heating stability were all good. Table 1 shows the test results and the like.

(Example 4) Degree of polymerization: 300, degree of saponification: 98
After melt | dissolving 132 g of polyvinyl alcohol of mol% in 1600 g of distilled water by heating, it is kept at 20 degreeC, 110 g of 35 weight% hydrochloric acid is added thereto, and acetaldehyde 30g is further added.
g, cooled to 12 ° C., and then 40 g of butyraldehyde was added. After the acetalized resin starts to precipitate,
This state was maintained for 30 minutes, and then the temperature was raised to 60 ° C. and the reaction was performed for 4 hours. After completion of the reaction, the solid content (resin) is washed with distilled water, the washed resin is redispersed in distilled water, sodium hydrogen carbonate is added to the obtained dispersion, and the pH of the solution is adjusted.
Was adjusted to 8. This liquid was heated to 60 ° C., kept in this state for 5 hours, and then cooled to room temperature.

The reheated and washed resin was added in an amount of 1
It was washed with 00 volumes of distilled water. Further, the resin washed with water was redispersed in distilled water, kept at 50 ° C. for 5 hours, washed with 100 times the amount of distilled water, dehydrated, and dried to prepare a polyvinyl acetal resin. The glass transition temperature of the polyvinyl acetal resin was 80 ° C. A heat-developable photosensitive material film was produced in the same manner as in Example 1 using the prepared polyvinyl acetal resin. The obtained polyvinyl acetal resin and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution,
The heat developability, the storage stability of the developed image and the heat stability were all good. Table 1 shows the test results and the like.

(Example 5) Degree of polymerization 240, residual acetyl group content 11 mol%, residual hydroxyl group content 21 mol%, acetoacetalization degree 35 mol%, butyralization degree 33 mol%, residual aldehyde content 3 ppm, water content A heat-developable photosensitive material film was prepared in the same manner as in Example 1, except that a polyvinyl acetal resin having a glass transition temperature of 70 ° C. and 1.5% by weight was used. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, the heat developability, the preservability of the developed image and the heating stability were all good. See Table 1 for test results
It was shown to.

(Example 6) Degree of polymerization 240, residual acetyl group content 1 mol%, residual hydroxyl group content 32 mol%, acetoacetalization degree 35 mol%, butyralization degree 32 mol%, residual aldehyde content 3 ppm, water content A heat-developable photosensitive material film was produced in the same manner as in Example 1, except that a polyvinyl acetal resin having a glass transition temperature of 76 ° C. and 1.5% by weight was used. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, the heat developability, the preservability of the developed image and the heating stability were all good. Table 1 shows the test results and the like.

(Example 7) Degree of polymerization 240, residual acetyl group content 1 mol%, residual hydroxyl group content 25 mol%, acetoacetalization degree 73 mol%, butyralization degree 1 mol%, residual aldehyde content 3 ppm, water content A heat-developable photosensitive material film was produced in the same manner as in Example 1, except that a polyvinyl acetal resin having a glass transition temperature of 103 ° C and 1.5% by weight was used. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, the heat developability, and the preservability of the developed image were all good. Table 1 shows the test results and the like.

(Example 8) Degree of polymerization 240, residual acetyl group content 12 mol%, residual hydroxyl group content 22 mol%, acetoacetalization degree 63 mol%, butyralization degree 1 mol%, residual aldehyde content 3 ppm, water content A heat-developable photosensitive material film was produced in the same manner as in Example 1, except that a polyvinyl acetal resin having a glass transition temperature of 93 ° C and 1.5% by weight was used. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, the heat developability, the preservability of the developed image, and the heating stability were all good. Table 1 shows the test results and the like.

Example 9 Polymerization degree 240, residual acetyl group content 1 mol%, residual hydroxyl group content 24 mol%, acetoacetalization degree 75 mol%, residual aldehyde content 3 ppm, water content 1.5 wt%, glass A heat-developable photosensitive material film was produced in the same manner as in Example 1 except that a polyvinyl acetal resin having a transition temperature of 109 ° C. was used. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. As a result, as in Example 1, the preservability of the coating solution, heat developability,
Both the storage stability and the heating stability of the developed image were good.
Table 1 shows the test results and the like.

Comparative Example 1 A heat-developable photosensitive material film was produced in the same manner as in Example 1 except that the polyvinyl acetal resin used in Example 1 was used except that the water content was 5% by weight. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. Coating solution has poor dispersibility of organic silver salt,
In the image after exposure of the heat developable photosensitive material film, the pattern boundary surface was unclear. Table 2 shows the test results and the like.

(Comparative Example 2) 2,2'-methylenebis (4-ethyl-6-t-butylphenol) was added as an antioxidant to the same polyvinyl acetal resin as in Example 1 for 50 days.
A heat-developable photosensitive material film was prepared in the same manner as in Example 1 except that 0 ppm was added. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. The coating solution was remarkably colored, and the heat-developable photosensitive material film was frequently fogged after exposure. Table 2 shows the test results and the like.

Comparative Example 3 A polymerization degree of 500, a residual acetyl group content of 1.5 mol%, a residual hydroxyl group content of 38 mol%, an acetoacetalization degree of 75 mol%, a residual aldehyde content of 3 ppm,
Example 1 except that a polyvinyl acetal resin having a water content of 1.5% by weight and a glass transition temperature of 60 ° C. was used.
A heat-developable photosensitive material film was prepared in the same manner as described above. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. No coloring of the coating solution was observed, but when the heat-developable photosensitive material film was stacked and stored, blocking occurred at 35 ° C., and the image after exposure of the heat-developable photosensitive material film had an unclear pattern boundary surface. Met. Table 2 shows the test results and the like.

Comparative Example 4 A heat-developable photosensitive material film was produced in the same manner as in Example 1 except that the same polyvinyl acetal resin as in Example 4 was used except that the water content was 5% by weight. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. Coating solution has poor dispersibility of organic silver salt,
In the image after exposure of the heat developable photosensitive material film, the pattern boundary surface was unclear. Table 2 shows the test results and the like.

(Comparative Example 5) 2,2'-methylenebis (4-ethyl-6-t-butylphenol) was added to the same polyvinyl acetal resin as in Example 4 as an antioxidant.
A heat-developable photosensitive material film was prepared in the same manner as in Example 1 except that 0 ppm was added. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. The coating solution was remarkably colored, and the heat-developable photosensitive material film was frequently fogged after exposure. Table 2 shows the test results and the like.

Comparative Example 6 The same polyvinyl alcohol as in Example 4 except that the residual hydroxyl group content was 38 mol%, the degree of acetoacetalization was 31 mol%, and the degree of butyralization was 29.5 mol%. Example 1 using acetal resin
A heat-developable photosensitive material film was prepared in the same manner as described above. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. No coloring of the coating solution was observed, but when the heat-developable photosensitive material film was stacked and stored, blocking occurred at 35 ° C., and the image after exposure of the heat-developable photosensitive material film had an unclear pattern boundary surface. Met. Table 2 shows the test results and the like.

Comparative Example 7 A polymerization degree of 500, a residual acetyl group content of 1.0 mol%, a residual hydroxyl group content of 37 mol%, a formalization degree of 62 mol%, a residual aldehyde content of 3 ppm, a water content of 1.5 wt%, A heat-developable photosensitive material film was produced in the same manner as in Example 1 except that a polyvinyl acetal resin having a glass transition temperature of 130 ° C. was used. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. The coating solution was slightly colored, and the resulting developable photosensitive material film slightly fogged after exposure. As for the heating stability, fine cracks occurred on the coating film surface.

(Comparative Example 8) Degree of polymerization 500, residual acetyl group content 1.0 mol%, residual hydroxyl group content 37 mol%, hexyl acetalization degree 62 mol%, residual aldehyde content 3 pp
m, a heat-developable photosensitive material film was prepared in the same manner as in Example 1, except that a polyvinyl acetal resin having a glass transition temperature of 50 ° C. and a water content of 1.5% by weight was used. The polyvinyl hexyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. The coating solution was slightly colored, and the resulting developable photosensitive material film slightly fogged after exposure. In addition, the heating stability was deformed by the heating.

(Comparative Example 9) The residual aldehyde content was 200 p
A heat-developable photosensitive material film was produced in the same manner as in Example 1, except that the same polyvinyl acetal resin as in Example 1 was used except that the resin composition was pm. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. The coating solution was slightly colored, and the heat-developable photosensitive material film was found to have fogging after exposure. Table 2 shows the test results and the like.

(Comparative Example 10) The amount of residual aldehyde was 200
A heat-developable photosensitive material film was produced in the same manner as in Example 1, except that the same polyvinyl acetal resin as in Example 4 was used except that the content was ppm. The polyvinyl acetal resin used and the obtained heat developable photosensitive material film were tested in the same manner as in Example 1. The coating solution was slightly colored, and the heat-developable photosensitive material film was found to have fogging after exposure. Table 2 shows the test results and the like.

[0063]

[Table 1]

[0064]

[Table 2]

(Example 10) <Preparation of polyvinyl acetal resin> 100 g of polyvinyl alcohol having a degree of polymerization of 300 and a degree of saponification of 98 mol% was added to 7
After heating and dissolving in 00 g of distilled water, the temperature was maintained at 20 ° C., and 29 g of 35% by weight hydrochloric acid was added thereto, and further 64 g of butyraldehyde was added. After the resin is deposited, hold for 30 minutes,
Thereafter, 108 g of the above hydrochloric acid was added, and the temperature was raised to 30 ° C.
Time kept. After the completion of the reaction, the resultant was washed with distilled water, and sodium hydroxide was added to the washed polyvinyl butyral resin dispersion to adjust the pH of the solution to 7. Solution at 50 ° C for 10
After holding for a while, the mixture was cooled. Next, the solution was washed with distilled water 100 times the solid content, and then the solution was further washed with 50 times.
After holding at 5 ° C. for 5 hours, it was washed with 100 times the volume of distilled water, dehydrated and dried to obtain a polyvinyl acetal resin.
Next, 100 g of polyvinyl alcohol having a polymerization degree of 650 and a saponification degree of 98 mol% was heated and dissolved in 700 g of distilled water, and a polyvinyl acetal resin was obtained in the same manner as described above.

<Preparation of Coating Solution for Photothermographic Material Film> 5.0 g of silver behenate, 5.0 g of polyvinyl acetal resin and 40 g of methyl ethyl ketone were ball milled.
Mix for 4 hours, then add N-lauryl-1-hydroxy-
0.2 g of 2-naphthamide was added, and the mixture was pulverized again with a ball mill to obtain a coating solution. The polyvinyl acetal resin used here was prepared by blending polyvinyl acetal resins having a degree of polymerization of 300 and 650 at a weight ratio of 1: 1 and an apparent degree of polymerization of 440, an apparent amount of hydroxyl groups of 21 mol%, and an apparent amount of acetyl groups of 1 0.7 mol% was used.

(Examples 11 to 16, Comparative Examples 11 to 14)
A heat developable photosensitive material film was produced in the same manner as in Example 10 except that the degree of polymerization, degree of saponification, type of aldehyde, degree of acetalization, amount of hydroxyl group, and blend ratio of the polyvinyl acetal resin were changed as shown in Table 3. A coating solution was prepared.

(Example 17) Degree of polymerization: 300, degree of saponification: 9
50 g of 8 mol% polyvinyl alcohol and a polymerization degree of 65
0, 50 g of polyvinyl alcohol having a saponification degree of 98 mol%
Was heated and dissolved in 700 g of distilled water, and a polyvinyl acetal resin was obtained in the same manner as in Example 10. Then, using the obtained polyvinyl acetal resin, Example 10
In the same manner as described above, a coating solution for a heat-developable photosensitive material film was prepared.

(Examples 18 to 23, Comparative Examples 15 to 16)
A heat-developable photosensitive material film was produced in the same manner as in Example 17, except that the degree of polymerization, the degree of saponification, the type of aldehyde, the degree of acetalization, the amount of hydroxyl groups, and the blend ratio of the polyvinyl alcohol resin were changed as shown in Table 4. A coating solution was prepared.

The amounts of residual acetyl groups, residual hydroxyl groups, residual aldehydes and water content of the polyvinyl acetal resins obtained in Examples 10 to 23 and Comparative Examples 11 to 16 were measured and evaluated in the same manner as in Example 1. Table 3 shows the results for Examples 10 to 16 and Comparative Examples 11 to 14,
Tables 4 for Examples 17 to 23 and Comparative Examples 15 and 16
It was shown to.

The apparent degree of polymerization, the apparent amount of hydroxyl groups, and the apparent amount of acetyl groups of the polyvinyl acetal resin were determined by the following equations. (A1 + B1) logX = A1 · logA2 + B1 · l
ogB2 X: apparent polymerization degree of blended polyvinyl acetal resin (apparent hydroxyl group amount, apparent acetyl group amount) A1: weight of polyvinyl acetal resin A A2: polymerization degree of polyvinyl acetal resin A (hydroxyl group amount, (Acetyl group content) B1: Weight of polyvinyl acetal resin B B2: Degree of polymerization of polyvinyl acetal resin B (hydroxyl content, acetyl content)

Further, in the same manner as in Example 1, the storage stability of the coating solution for a heat-developable photosensitive material film was evaluated. Further, a heat-developable photosensitive material film was prepared in the same manner as in Example 1, and the following evaluation was performed. The results are shown in Table 3 for Examples 10 to 16 and Comparative Examples 11 to 14, and Examples 17 to 2
Table 4 shows No. 3 and Comparative Examples 15 and 16.

<Heat developability of heat developable photosensitive material film>
To evaluate the heat developability of the obtained heat developable photosensitive material film, a 250-watt high-pressure mercury lamp was exposed through a gradation pattern film from a distance of 20 cm for 0.3 seconds, and then a hot plate at 110 ° C was exposed. And developed by heating for 3 seconds to obtain a good pattern image of cyan color. At this time, those with no fog and good sharpness were rated as ○, those with some fog and poor sharpness were rated as Δ, and those with many fogs and poor sharpness were rated as x.

<Preservation of Developed Image> Next, to confirm the preservation of the developed image, it was exposed to white light for 24 hours.も の indicates that no image pattern contrast disturbance was observed, △ indicates that the image pattern contrast was slightly disturbed, and X indicates that the image pattern contrast was significantly disturbed.
Was evaluated.

<Heat Stability> A heat-developable photosensitive material film obtained as described above was placed on a stainless steel plate at 100 ° C. having irregularities formed at intervals of 1 mm in height and 1 mm in width, and the coating was applied to the stainless steel plate side. After the mounting, the heat developable photosensitive material film was pressed against the stainless steel plate at a pressure of 150 g / cm ² for 5 seconds. continue,
The heat-developable photosensitive material film was cooled at room temperature, and the coating surface of the heat-developable photosensitive material film was visually observed, and those having no cracks or deformation were evaluated as ○, and those having cracks or deformation were evaluated as x. .

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[Table 3]

[0077]

[Table 4]

In the case of Comparative Example 11, the dispersibility of the organic silver salt in the coating solution was poor due to the large amount of water contained in the polyvinyl acetal resin, resulting in poor heat developability and image preservability. In Comparative Example 12, the storage stability of the coating solution was poor and the heat developability was poor because the antioxidant was blended in the polyvinyl acetal resin. Comparative Example 13 was poor in dispersibility due to a large amount of residual hydroxyl groups, and poor in image preservability due to moisture absorption and the like. In Comparative Examples 14 to 16, although the storage stability of the coating solution was good, the heat developability and the heat stability were poor. On the other hand, those of Examples 10 to 23
Because it is controlled within the scope of the present invention, the storage stability of the coating solution,
A heat developable photosensitive material film having excellent heat developability, preservability of a developed image, and heat stability was obtained.

[0079]

According to the present invention, since it has the above-mentioned structure, it has excellent preservability and extremely excellent image characteristics. Further, the coating film may be creased or cracked during handling. Therefore, it is possible to provide a heat-developable photosensitive material that does not thermally deform during heat development.

Continued on front page F-term (reference) 2H025 AA00 AC01 AD01 AD03 CB07 FA22 2H096 AA00 BA20 EA02 GA52 LA16 4J002 BE06W BE06X GP03 4J100 AD02P AF15P BA02H CA01 CA31 DA01 HA19 HA43 HA56 HC16 HC17 HC18 HC19 HC20 JA37

Claims (4)

[Claims] 1. A polyvinyl acetal resin synthesized by an acetalization reaction between polyvinyl alcohol and an aldehyde, having a degree of polymerization of 200 to 3000, and remaining when the acetal group is counted as two acetalized hydroxyl groups. The ratio of acetyl groups is 0 to 25 mol%, the ratio of residual hydroxyl groups is 17 to 35 mol%, the water content is 2.5 wt% or less, the residual aldehyde content is 10 ppm or less, A polyvinyl acetal resin for a heat-developable photosensitive material, characterized by containing no agent. 2. A polyvinyl acetal resin for a heat-developable photosensitive material containing at least two kinds of polyvinyl acetal resins having different degrees of polymerization by at least 300, wherein the apparent degree of polymerization is from 200 to 1,000, and an acetal group is contained. When counted as two acetalized hydroxyl groups, the ratio of apparent residual acetyl groups is 0 to 25 mol%, the ratio of apparent residual hydroxyl groups is 17 to 35 mol%, and the water content is 2. A polyvinyl acetal resin for a heat-developable photosensitive material, which is 5% by weight or less, has a residual aldehyde content of 10 ppm or less, and does not contain an antioxidant. 3. The polyvinyl acetal resin for a heat-developable photosensitive material according to claim 1, wherein the glass transition temperature is 55 to 110 ° C. 4. A photothermographic material comprising the polyvinyl acetal resin for photothermographic material according to claim 1, 2 or 3.