JP2003147018A - Polyvinyl acetal resin for heat-developable photosensitive material and heat-developable photosensitive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl acetal resin which is used as a binder, has a specific composition, and is useful for producing heat-developable photosensitive materials that do not cause the problem of blocking, even when stored for a long period, have good raw film storability, have good performances such as good film storability and good halation resistance after the formation of images, and can exhibit excellent image characteristics, and to provide a heat-developable photosensitive material. SOLUTION: This polyvinyl acetal resin acetalized with acetaldehyde and butyraldehyde in a total acetalization degree of >=65 mol.% and used for heat- developable photosensitive materials is characterized by having an acetaldehyde acetalization degree (A) and a butyraldehyde acetalization degree (B) in a molar ration of 3/7 to 7/3 and having a residual water content of <=2.5 wt.%.

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 heat-developable light-sensitive material used for a heat-developable light-sensitive material containing an organic silver salt and a reducing agent for development in the same composition. And a photothermographic material using the same.

[0002]

2. Description of the Related Art A photothermographic material is a heat-developable light-sensitive material, which is prepared by dispersing a fatty acid silver salt, an organic reducing agent, and optionally a small amount of light-sensitive silver halide in a polymer binder on a support. It is made by coating. Conventionally widely used silver halide materials have been used as a high-quality material in a wide range of image forming fields due to their excellent photographic characteristics, but development and fixing are complicated and the processing steps are wet. Therefore, there is a problem that the treatment is complicated and a large amount of chemical waste liquid is discharged.

Therefore, at present, a photothermographic material in which a developing process is carried out by heat treatment has been developed and put into practical use. For example, Japanese Examined Patent Publication No. 43-4924 discloses a photothermographic material comprising an organic silver salt, a reducing agent and a silver halide in catalytic contact with organic silver ions.
That is, these heat-developable photosensitive materials are polyvinyl butyral, polymethyl methacrylate, cellulose acetate, polyvinyl acetate, cellulose acetate propionate, cellulose acetate butyrate on a support such as paper, plastic film, metal foil and glass plate. It is described that it is applied by using a film-forming binder such as.

As the film-forming binder, specifically, a polyvinyl acetal resin is optimally used.
However, depending on the hygroscopicity and residual water content of the polyvinyl acetal resin, the image characteristics after coating have problems such as fogging, poor gradation, insufficient sensitivity, and changes over time during storage of the raw film and the film after image formation. Sometimes occurred.

Further, there are various compositions of general polyvinyl butyral resin, and in addition, since the manufacturing method contains a small amount of impurities, the adjusted binder solution becomes photosensitive due to the influence of these impurities and is colored. In some cases, fogging, poor gradation, insufficient sensitivity, and poor raw storability of the film may occur in the image characteristics after coating.

In order to solve the above problems, improvements have been made to silver salts, reducing agent substances, additives and the like. For example, in JP-A-49-52626, it is improved by using a silver salt of a thione compound without using an independent stabilizer and a stabilizer precursor component, and a polyvinyl butyral resin is also used as a binder. However, a technique for solving the problem by specifying the composition of the binder used is not disclosed.

Further, among the heat-developable light-sensitive materials, the heat-developable silver salt film is superior in image characteristics, particularly in image density and image / gradation area, to the conventional X-ray light-sensitive film using wet type gelatin. The sharpness is somewhat inferior, and therefore its improvement is desired, but for that purpose, it was necessary to strictly control the silver nucleus growth during heating.

[0008]

In order to solve the above-mentioned conventional problems, the present invention has a specific composition of the polyvinyl acetal resin used as a binder so that there is no blocking problem even during long-term storage. , A raw film storability, film storability after image formation, and performance such as fogging are good, and a polyvinyl acetal resin for a heat-developable photosensitive material capable of exhibiting excellent image characteristics and a heat-developable feeling using the same The purpose is to provide an optical material.

[0009]

The polyvinyl acetal resin for a heat-developable photosensitive material according to the invention of claim 1 (hereinafter referred to as invention 1) is acetalized with acetaldehyde and butyraldehyde, and the total degree of acetalization is 65 mol. % Or more, the polyvinyl acetal resin for a photothermographic material having a mol% ratio of the acetalization degree (A) acetalized with acetaldehyde and the acetalization degree (B) acetalized with butyraldehyde is 3%. / 7
˜7 / 3, and the residual water content is 2.5% by weight or less.

The polyvinyl acetal resin for a heat-developable photosensitive material according to the invention of claim 2 (hereinafter referred to as invention 2) is the same as the polyvinyl acetal resin for a heat-developable photosensitive material according to the above-mentioned invention 1, in which the residual aldehyde content is 10 pp.
It is characterized by being m or less.

The heat-developable photosensitive material according to the invention of claim 3 (hereinafter referred to as invention 3) is characterized by using the polyvinyl acetal resin for a heat-developable photosensitive material according to invention 1 or 2. Hereinafter, the present invention will be described in detail.

The polyvinyl acetal resin used in the present invention has acetalization degree with acetaldehyde and butyraldehyde, and acetalization degree with acetaldehyde (A) and acetalization degree with butyraldehyde (B). Mol% ratio is 3/7 ~
What is 7/3 is used. This mol% ratio is 3/7
When it is less than 0/10, the ratio of acetalization with butyraldehyde is high, and it is difficult to balance the hydrophilicity, and the organic acid forms a crystalline substance during storage of the film after image formation, and the surface of the coating film becomes whitish. There is a problem such as. On the other hand, if it is more than 7/3 to 10/0, the storage stability of the film after image formation is good, but it tends to absorb moisture during storage of the raw film, resulting in problems such as fogging during image formation. May occur, or the films may block due to moisture absorption.

The total degree of acetalization of the polyvinyl acetal resin (the sum of the degree of acetalization (A) acetalized with acetaldehyde and the degree of acetalization (B) acetalized with butyraldehyde) is 65 mol%. That is all. If the total degree of acetalization is less than 65 mol%, it becomes difficult to balance the hydrophilicity because the number of hydroxyl groups increases, and the organic acid forms a crystalline substance during film storage after image formation, and the coating surface becomes whitish. There is.
The degree of acetalization described here means that the acetal group of the polyvinyl acetal resin is formed by acetalizing two hydroxyl groups, and thus the degree of acetalization is 2%.
It was determined by the mol% of the degree of acetalization calculated by the method of counting one hydroxyl group.

The degree of polymerization of the polyvinyl acetal resin is not particularly limited, but is preferably 200 to 3,000. In particular, those having a degree of polymerization of 200 to 1000, which can easily balance the dispersibility of the silver salt used in the heat-developable photosensitive material, the coating film strength, the coatability, etc., are more preferably used.

The amount of residual acetyl groups in the polyvinyl acetal resin is not particularly limited, but is preferably 0 to 25 mol%. If the amount of residual acetyl groups exceeds 25 mol%, the resulting photosensitive films may be blocked from each other, and the image may not be clear.
More preferably, it is 0 to 15 mol%.

The polyvinyl acetal resin is
Generally, it is obtained by acetalizing polyvinyl alcohol, but if it does not affect the above-mentioned performance, it may be used by acetalizing polyvinyl alcohol obtained by mixing two or more kinds of polyvinyl alcohol,
Further, two or more kinds of polyvinyl acetal resins may be mixed to adjust the above range.

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

The above-mentioned acid catalyst is not particularly limited, and either an organic acid or an inorganic acid can be used, and examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid and hydrochloric acid.

In order to stop the above synthetic reaction, alkali neutralization is usually carried out. Examples of the alkali used at this time include sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, Examples include sodium hydrogen carbonate and potassium carbonate. In addition to alkali neutralization, alkylene oxides such as ethylene oxide and glycidyl ethers such as ethylene glycol diglycidyl ether can be used as a terminator for the acetalization reaction.

In the polyvinyl acetal resin according to the present invention, the residual water content is 2.5% by weight or less, preferably 2.0% by weight or less. If the residual water content exceeds 2.5% by weight, the pot life of the coating solution will be reduced, and it will also react with a crosslinking agent added to increase the coating strength, for example, a compound containing an isocyanate group. , The target coating strength cannot be obtained,
Increasing the amount of the crosslinking agent added in anticipation of reacting with water may cause fogging or the like. Examples of the method of reducing the residual water content to 2.5% by weight or less include a method of removing the water content to a specified amount or less by drying after a washing operation with water or a mixed solution of water / alcohol.

In the polyvinyl acetal resin of the present invention, the residual aldehyde content is preferably 10 ppm or less, more preferably 5 ppm or less. When the amount of residual aldehyde exceeds 10 ppm, the aldehyde is reduced by the reducing agent contained in the coating solution, which deteriorates the storage stability of the coating solution, which may cause deterioration of the raw storage stability of the film and fogging. is there. Examples of the method of reducing the amount of residual aldehyde to 10 ppm or less include a method of purifying by a washing operation with water, a mixed solution of water / alcohol, etc., and removing to a prescribed amount or less.

In the acetalization reaction of polyvinyl alcohol and an aldehyde, an antioxidant is usually added to the reaction system or the resin system in order to prevent the aldehyde from oxidizing, or to prevent the resulting resin from oxidizing and improving the heat resistance. However, in the synthesis of the polyvinyl acetal resin of the present invention, when a hindered phenol-based, bisphenol-based, phosphoric acid-based antioxidant or the like which is generally used as an antioxidant is used, it is contained in the polyvinyl acetal resin. It is not used at all because it may remain and cause a decrease in the pot life of the coating solution and a deterioration in the raw storability of the raw film, which may impair the fogging and the sharpness of the image / gradation portion.

The polyvinyl acetal resin thus obtained is used to produce a photothermographic material. The blending components of the heat-developable photosensitive material are the same as the blending components of conventionally known heat-developable photosensitive materials except that the above polyvinyl acetal resin is 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, a cross-linking agent, and other additives are added to the polyvinyl acetal resin. The blending amount of the polyvinyl acetal resin is preferably 1:10 to 10: 1 by weight ratio with respect to the organic silver salt, and more preferably 1: 5 to 5: 1.

The above organic silver salt is a colorless or white silver salt which is relatively stable to light, and when heated to 80 ° C. or higher in the presence of exposed silver halide, it reacts with a reducing agent to form silver. It is not particularly limited as long as it is produced, and examples thereof include silver salts of organic compounds having a mercapto group, a thione group or a carboxyl group, and benzotriazole silver. Specifically, a silver salt of a compound having a mercapto group or a thione group, a silver salt of 3-mercapto-4-phenyl 1,2,4-triazole, a silver salt of 2-mercapto-benzimidazole, 2-mercapto-5. -A silver salt of aminothiazole,
Silver salt of 1-phenyl-5-mercaptotetrathiazole, silver salt of 2-mercaptobenzothiazole, silver salt of thioglycolic acid, silver salt of dithiocarboxylic acid such as silver salt of dithioacetic acid, silver thioamide, silver thiopyridine salt, Silver salt of mercaptooxadiazole, silver salt of mercaptotriazine, silver salt of aliphatic carboxylic acid: silver caprate, silver laurate, silver myristate, silver palmitate, silver stearate, silver behenate, silver maleate, Silver fumarate, silver tartrate, silver furoate, silver linoleate, silver oleate, silver hydroxystearate, silver adipate, silver sebacate,
Silver succinate, silver acetate, silver butyrate, silver camphorate, etc., silver aromatic carboxylic acid, silver thione carboxylate, silver aliphatic carboxylic acid having thioether group, silver salt of tetrazaindene, S-
2-aminophenyl silver thiosulfate, metal-containing amino alcohols, organic acid metal chelates and the like can be mentioned.

Among the above organic silver salts, silver salts of aliphatic carboxylic acids are preferable, and silver behenate is more preferable. The particle size of the organic silver salt is 0.01
-10 micrometers is preferred and 0.1-5 micrometers is more preferred.

In some cases, the above-mentioned organic silver salt may be catalytically contacted with a photosensitive silver halide. For example, a solution or dispersion liquid of an organic silver salt prepared in advance or a film material containing the organic silver salt is added, Examples thereof include a method in which a silver halide-forming component is allowed to act to form a part of organic silver into silver halide.

As the above-mentioned photosensitive silver halide-forming component, a silver halide (for example, silver bromide, silver iodide, silver chloride, silver chlorobromide, silver iodobromide, chloroiodo) which acts on an organic silver salt is used. It is not particularly limited as long as it forms a silver halide, etc.,
It is preferable to contain iodine ions. In such cases,
For 100 parts by weight of organic silver salt, a photosensitive silver halide of 0.
It is preferably used in an amount of 0005 to 0.2 part by weight, more preferably 0.01 to 0.2 part by weight.

In addition, a reducing agent is usually used in the heat-developable photosensitive material together with the above organic silver salt. Such a reducing agent is not particularly limited and is appropriately selected depending on the organic silver salt used in combination, and examples thereof include substituted phenols, bisphenols, naphthols, bisnaphthols, polyhydroxybenzenes, di- or polyhydroxynaphthalenes. , Hydroquinone monoethers, ascorbic acid or derivatives thereof, reducing sugars, aromatic amino compounds, hydroxyamines, hydrazines, phenidones, hydroquinones, hindered phenols and the like. Of these, a photodegradable reducing agent is preferably used, but a thermally decomposable reducing agent can also be used. Further, a compound that promotes photodecomposition can be used in combination, and a coating agent for inhibiting the reaction between silver halide and a reducing agent can also be used in combination.

Among the above reducing agents, hindered phenols are preferably used, and 0.0001 to 3.0 parts by weight of the reducing agent is preferably used, and more preferably 0, to 100 parts by weight of the organic silver salt. 0.01 to 1.0 part by weight.

As a method for preparing a photothermographic material using the polyvinyl acetal resin of the present invention, for example,
A method in which a polyvinyl acetal resin, an organic silver salt, a reducing agent and a solvent are dispersed by a ball mill, and then silver halide or a silver halide-forming component and various additives are further added and dispersed by a ball mill, if necessary. Is mentioned.

As the above solvent, those which dissolve the polyvinyl acetal resin and have almost no water content are preferably used. Of these, ketones and esters are preferable, and specifically, diethyl ketone, methyl ethyl ketone,
Methyl isobutyl ketone, methyl acetate, ethyl acetate, propyl acetate and the like can be mentioned.

The dispersion obtained by the above method is coated on a support so that the amount of the organic silver salt is regulated, and the solvent is evaporated to obtain a photothermographic material. The organic silver salt and the reducing agent may be mixed together in a polyvinyl acetal resin to form a single layer on the support, but the organic silver salt and the reducing agent may be separately added to the polyvinyl acetal resin. It is also possible to form these into two layers separately on the support.

Examples of the support include polyethylene terephthalate, polycarbonate, polyethylene,
A plastic film such as polypropylene, polyvinyl acetal, cellulose ester, cellulose diacetate, cellulose triacetate, nitrocellulose, polyethylene naphthalate, vinyl chloride or chlorinated polypropylene, or a metal plate such as glass, paper or aluminum plate may be used.

The silver coated on the support is 1 m ² of the support.
The amount is preferably 0.1 to 5.0 g, and more preferably 0.3 to 3.0 g.
If it is less than 0.1 g, the image density may decrease,
No improvement in image density was observed even if more than 5.0 g was used. The coating may be on both sides or one side.

In the present invention, when a black image is formed with silver, a toning agent may be added as an additive. Further, in the case of forming a color image, a color coupler, a leuco dye or the like may be added. Further, a sensitizer or the like may be added depending on the case.

The polyvinyl acetal resin for heat-developable light-sensitive material and the heat-developable light-sensitive material of the present invention having the above-mentioned constitution can suppress deterioration of raw film storability and fogging due to the influence of moisture absorption, Further, by keeping the balance of hydrophilicity, the storability of the film after image formation is excellent.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

(Example 1) 1. Adjustment of Polyvinyl Acetal Resin 132 g of polyvinyl alcohol having a degree of polymerization of 500 and a degree of saponification of 98 mol% was dissolved in 1600 g of distilled water with heating, and then kept at 20 ° C., and 110 g of 35 wt% hydrochloric acid was added thereto, and 35 g of acetaldehyde was further added. Was added. Then 1
After cooling to 2 ° C., 33 g of butyraldehyde was added. After the resin was deposited, the temperature was maintained for 30 minutes, then the temperature was raised to 60 ° C. and the temperature was maintained for 4 hours. After completion of the reaction, the product was washed with distilled water, and sodium hydrogencarbonate was added to the polyvinyl acetal resin dispersion liquid after washing with water to adjust the pH of the solution to 8. This solution was kept at 60 ° C. for 5 hours and then cooled. Next, the solution was washed with 100 times amount of distilled water with respect to the solid content, further, the solution was kept at 50 ° C. for 5 hours, then washed with 100 times amount of distilled water, dehydrated and dried. The polyvinyl acetal resin thus obtained has a total acetalization degree of 74 mol%, an acetoacetalization degree (A) of 44 mol%, a butyralization degree (B) of 30 mol%, and a mol% ratio (A
/ B ratio) was 59/41. The residual aldehyde content was 1 ppm and the residual water content was 2.0% by weight. Here, the degree of acetalization (degree of acetoacetalization, degree of butyralization) was measured using ¹³ C-NMR. The residual aldehyde amount was determined by thermally extracting the polyvinyl acetal resin in a heating furnace and measuring the extract using gas chromatography. Furthermore, the residual water content was measured using a Karl Fischer moisture meter.

2. Preparation of coating solution for heat-developable photosensitive material film 5.0 g of the polyvinyl acetal resin obtained above, 5.0 g of silver behenate, and 40 g of methyl ethyl ketone were mixed in a ball mill for 24 hours, and further N-lauryl-1-hydroxy was added. 2-0.2 naphthamide was added and mixed again with a ball mill to obtain a coating solution.

3. Preparation of heat-developable photosensitive material film The coating solution obtained above was applied on a polyester substrate so that the thickness after drying was 10 μm, and dried. Further, on this coated surface, 0.5 g of N, N-dimethyl-p-phenylenediamine / lead sulfate and polyvinylpyrrolidone 2
A solution of g and methanol (30 ml) was applied so that the thickness after drying was 1 μm and dried to prepare a laminated photothermographic material film.

The performance of the heat-developable photosensitive material film obtained above was evaluated by the following method. The results are shown in Table 1.

(1) Storability of raw film The above photothermographic film was kept at a humidity of 60% and a temperature of 20 ° C
I kept it in my room for one month. After that, the photosensitive material film 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.
It was heated for 3 seconds using a hot plate of 0 ° C. to obtain a good cyan pattern image. From this pattern image, the storability of the raw film was evaluated according to the following three levels. ○: No fog and good sharpness △: Slight fog and poor sharpness ×: Many fogging and poor sharpness

(2) Blocking property of raw film The above photothermographic material film was cut into A4 size,
100 sheets were piled up and stored for one month in a room having a humidity of 60% and a temperature of 40 ° C. Thereafter, the blocking level of this film was evaluated according to the following three levels. ◯: No blocking at all, and peeling off one by one cleanly Δ: Part of the film is blocking and there is a part that is difficult to peel off ×: Most of the film is blocking and peeling is quite difficult Is

(3) Film storability after image formation The above heat-developable photosensitive material film 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 a heat plate at 110 ° C. was used. And heated for 3 seconds to obtain a good cyan pattern image. Then, this film was stored in a room with a humidity of 60% and a temperature of 40 ° C. for one month, and then the state of the film surface was observed, and the film storability was evaluated according to the following three levels. ○: An image that is the same as before storage is formed. △: Part of the image is whiter than before storage. ×: Many parts are whiter than before storage.

(Examples 2 to 7, Comparative Examples 1 to 4) In adjusting the polyvinyl acetal resin, the degree of polymerization of the polyvinyl alcohol resin, the degree of saponification, the degree of acetalization of the polyvinyl acetal resin, the A / B ratio, and the remaining Example 1 except that the water content and the residual aldehyde content were as shown in Table 1.
A heat-developable photosensitive material film was prepared by the same method.

The performance of the heat-developable photosensitive material films obtained in Examples 2 to 7 and Comparative Examples 1 to 4 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0047]

[Table 1]

[0048]

As described above, the polyvinyl acetal resin for a heat developable photosensitive material of the present invention and the heat developable photosensitive material using the same have the above-mentioned constitution, and thus can be stored for a long time. There is no problem of blocking, the storability of raw film, the storability of film after image formation, and the performance such as fogging are good, and excellent image characteristics are exhibited.

Claims (3)

[Claims] 1. A polyvinyl acetal resin for a photothermographic material, which is acetalized with acetaldehyde and butyraldehyde and has a total degree of acetalization of 65 mol% or more, wherein the acetalization degree (A) is acetalized with acetaldehyde. And the degree of acetalization (B) that is acetalized with butyraldehyde is 3/7 to 7 /.
3. The polyvinyl acetal resin for a heat-developable photosensitive material, which has a residual moisture content of 2.5% by weight or less. 2. The polyvinyl acetal resin for a photothermographic material according to claim 1, wherein the residual aldehyde content is 10 ppm or less. 3. A photothermographic material comprising the polyvinyl acetal resin for a photothermographic material according to claim 1 or 2.