Polyvinylacetal resin for heat-developable photosensitive material and heat-developable photosensitive material

Abstract

A polyvinyl acetal resin for a heat-developable photosensitive material capable of preventing skinning in the coating process of the photosensitive layer of the heat-developable photosensitive material, preventing deterioration of image characteristics and coloration of the coating solution, and suppressing the occurrence of odor at the time of producing the heat-developable photosensitive material and heat development. The polyvinyl acetal resin for a heat-developable photosensitive material used for a photosensitive layer of the heat-developable photosensitive material has a residual acetyl group content of 25 mol % or less, residual hydroxyl group content of 17-35 mol %, and polymerization degree of 200 to 3,000, and is obtained by an acetalization of a polyvinyl alcohol mixture containing polyvinyl alcohol resins having different polymerization degrees, wherein the content of the polyvinyl alcohol having a polymerization degree of 600 or less is 50 wt % or higher in the polyvinyl alcohol mixture.

Claims

1. A polyvinyl acetal resin comprising a residual acetyl group content of 25 mol % or less, residual hydroxyl group content of 17-35 mol %, and having a polymerization degree of 200 to 3,000, wherein: the polyvinyl acetal resin is obtained by an acetalization of a polyvinyl alcohol mixture containing polyvinyl alcohol resins having different polymerization degrees, and the polyvinyl alcohol mixture comprises 60% or more of polyvinyl alcohol having a polymerization degree of 600 or less, and the polyvinyl acetal resin is capable of use as a photosensitive layer of a heat-developable photosensitive material.

2. The polyvinyl acetal resin according to claim 1, comprising 60 ppm or less of 2-ethyl-2-hexenal.

3. The polyvinyl acetal resin according to claim 1, comprising 100 ppm or less of each of alkali metal, alkaline earth metal, halide ions, sulfate ions and nitrate ions.

4. The polyvinyl acetal resin according to claim 1, which is obtained by washing only particles which are able to pass through #60 mesh sieve after the acetalization.

5. The polyvinyl acetal resin according to claim 1, which is granulated by compression granulation.

6. A heat-developable photosensitive material comprising a support and a photosensitive layer formed on the support, wherein the photosensitive layer contains the polyvinyl acetal resin according to claim 1, organic silver salt, photosensitive silver halide and silver ion reducing agent.

Description

DESCRIPTION OF EMBODIMENTS

(1) The invention is further illustrated by the following examples, but the present invention is not limited to these examples.

Example 1

(2) 50 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 600, and 26 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 800, and 24 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 1700, were dissolved in 700 g of distilled water by heating.

(3) The solution was kept at 20 C., then 26 g of 70% nitric acid was added, and 16 g butylaldehyde was added further.

(4) Then it was cooled to 10 C., and 70 g butylaldehyde was added.

(5) After the resin precipitated, and held for 30 minutes, then 93 g nitrate was added and kept for 6 hours, and the temperature was raised to 35 C.

(6) After the end of the reaction, flushing for 10 hours with distilled water followed, and the polyvinylbutyral resin was dehydrated after washing. The only particles capable of passing through a #60 mesh sieve were dispersed in distilled water and then sodium hydroxide was added to adjust to pH 8. After holding for 6 hours at 50 C., the solution was cooled.

(7) Then, the solution was washed with running distilled water for 2 hours, then dehydrated and dried at 40 C. for 12 hours, then the polyvinylacetal resin particles were ground by a mortar, sieved by a #60 mesh sieve, and then the only particles capable of passing through the sieve were washed for 10 hours with running distilled water.

(8) The polyvinyl acetal resin was gained after washing, dewatering, and drying.

(9) The residual acetyl group content of the obtained polyvinyl acetal resin was 1.7 mol %, and the residual hydroxyl group content was 20 mol %. The ratio of the particles having a particle size of 35 m or less was 96% in the obtained polyvinyl acetal resin.

(10) Then, the obtained polyvinyl acetal resin was subjected to granulation treatment by passing the resin through two rolls provided with a concave recess on the roll surface. The obtained powder was sieved by a #50 mesh sieve and ungranulated powder was removed and then polyvinyl acetal resin powder was obtained.

Example 2

(11) Except for using 35 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 600, and 26 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 400, and 21 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 800, and 18 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 2400, the experiments were conducted in the same manner as in Example 1.

(12) The residual acetyl group content of the obtained polyvinylacetal resin was 1.1 mol %, and the residual hydroxyl group content was 28 mol %.

(13) The ratio of particles having a particle size of 35 m or less was 98% in the obtained polyvinyl acetal resin.

(14) The polyvinyl acetal resin powder was obtained by performing granulation in the same manner as in Example 1.

Example 3

(15) 95 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 600, and 37 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 1700 (the composition ratio of the polyvinyl alcohol having a degree of polymerization of 600 or less was 72%), were dissolved in 1600 g of distilled water by heating.

(16) The solution was kept at 20 C., then 90 g of 70% nitric acid was added, and 28 g acetaldehyde was added further.

(17) Then it was cooled to 13 C., and 36 g butyraldehyde was added. After the resin was precipitated, and held for 30 minutes, then it was kept for 5 hours, and the temperature was raised to 55 C.

(18) After the end of the reaction, flushing for 10 hours with distilled water followed, and the polyvinylacetal resin was dehydrated after washing. The only particles capable of passing through a #60 mesh sieve were dispersed in distilled water and then sodium bicarbonate was added to adjust to pH 8. After holding for 6 hours at 50 C., the solution was cooled. After cooling, pH was 8.

(19) Then, the solution was washed with running distilled water for 2 hours, then dehydrated and dried at 40 C. for 12 hours.

(20) The polyvinylacetal resin particles were ground by a mortar, sieved by a #60 mesh sieve, and then the only particles capable of passing through the sieve were washed for 10 hours with running distilled water.

(21) The polyvinyl acetal resin was gained after washing, dewatering, and drying.

(22) The residual acetyl group content of the obtained polyvinyl acetal resin was 1.8 mol %, and the residual hydroxyl group content was 26 mol %.

(23) The acetacetal degree of the obtained polyvinylacetal resin was 37.3 mol % (51.7% per total acetal), and the butylalization degree was 34.9 mol %. The ratio of the particles having the particle size of 35 m or less was 95% in the obtained polyvinyl acetal resin.

(24) The polyvinyl acetal resin powder was obtained by performing granulation in the same manner as in Example 1.

Example 4

(25) Except for using 98 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 400, and 34 g of polyvinyl alcohol in which saponification degree was 98%, polymerization degree was 2400, the experiments were conducted in the same manner as in Example 3.

(26) The residual acetyl group content of the obtained polyvinylacetal resin was 1.3 mol %, and the residual hydroxyl group content was 23 mol %.

(27) The ratio of particles having a particle size of 35 m or less was 98% in the obtained polyvinyl acetal resin.

(28) The polyvinyl acetal resin powder was obtained by performing granulation in the same manner as in Example 1.

Comparative Example 1

(29) Except for using a polyvinyl alcohol resin with polymerization degree 1700, experiments were conducted in the same manner as in Example 3.

(30) The residual acetyl group content of the obtained polyvinyl acetal resin was 1.9 mol %, and the residual hydroxyl group content was 30 mol %. The acetacetal degree of the obtained polyvinylacetal resin was 40.1 mol % (58.9% per total acetal), and the butylalization degree was 28.0 mol %. After the reaction and grinding step, except the process of sieving by using a #60 mesh sieve, polyvinyl acetal resin powder was obtained in the same manner as in Example 1.

Comparative Example 2

(31) Except for using a polyvinyl alcohol resin in which polymerization degree was 900, experiments were conducted in the same manner as in Example 3.

(32) The residual acetyl group content of the obtained polyvinyl acetal resin was 1.2 mol %, and the residual hydroxyl group content was 25 mol %. The acetacetal degree of the obtained polyvinylacetal resin was 50 mol % (79.4% per total acetal), and the butylalization degree was 13.0 mol %. After the reaction and grinding step, except the process of sieving by using a #60 mesh sieve, polyvinyl acetal resin powder was obtained in the same manner as in Example 3.

(33) (Evaluation)

(34) The polyvinyl acetal resin powders obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were evaluated by the following methods. The results are shown in Table 1.

(35) (1) Bulk Specific Gravity

(36) By the method of JIS K6720, bulk specific gravity of the obtained the polyvinylacetal resin particles was measured.

(37) (2) Evaluation of Handling Properties of Polyvinylacetal Resin

(38) 14 g of the obtained polyvinylacetal resin was placed in a 100 ml-glass bottle with a lid.

(39) The resin was dissolved in 56 g of MEK: ethanol (2:8) mixed solution.

(40) In this case, handling property was evaluated according to the following criteria.

(41) : Polyvinyl acetal resin powder could be put into a bottle at once.

(42) X: Polyvinyl acetal resin powder could not be put into a bottle at once.

(43) It is necessary to introduce it into the bottle several times while dissolving it.

(44) (3) Evaluation of the Skinning of Coating Layer

(45) By using the applicator which is set at 10 mil, the resin solution prepared in (2) Evaluation of handling properties of polyvinylacetal resin is coated on the PET film and dried for 15 minutes in a 60 C. oven. Then, the surface condition of the coating film was evaluated.

(46) : There was no wrinkle and smooth surface was obtained.

(47) X: There was rough surface, wrinkle, or bubbles due to skinning.

(48) (4) Content of 2-ethyl-2-hexenal

(49) The content of 2-ethyl-2-hexenal in the obtained the polyvinyl acetal resin was measured by Gas chromatography which is connected headspace (Tekmer Dohrmann Co., Ltd.)

(50) (GPC: manufactured by Shimadzu Corporation, GC-14, column: TC-WAX PEG using a 0.25 mm30 m).

(51) (5) Measurement of the Content of Ions

(52) The content of sodium ions was evaluated by elemental absorption method.

(53) In addition, the content of nitrate ions was evaluated by ion chromatography.

(54) (6) The Evaluation of Coloring of Organic Silver Salt Solution

(55) 5 g of the obtained polyvinyl acetal resin powder, 5 g of silver behenate, 40 g of methyl ethyl ketone were mixed in a ball mill for 24 hours. Then, 0.2 g of N-lauryl-1-hydroxy-2-naphthamide was added, thereby producing a coating solution by ball-milled again. These solutions were observed for color changes under a fluorescent lamp for 3 days at room temperature indoors.

(56) The evaluation was done by the following criteria.

(57) : There was no change from white.

(58) X: Coloration was observed.

(59) (7) Image Evaluation

(60) The coating solution prepared in (6) The evaluation of coloring of organic silver salt solution was applied on to the polyester substrate and dried so that the thickness after drying was 10 m.

(61) On this coated surface, a solution which had the following composition was coated.

(62) Solution composition: N, N-dimethyl-p-phenylenediamine sulfate 0.5 g, polyvinylpyrrolidone 2 g, methanol 30 mL

(63) The dried coating thickness after drying was 1 m, so that a photosensitive film was obtained.

(64) The obtained photosensitive film was exposed for 0.3 seconds at a distance of 20 cm with high pressure mercury such as 250 watt through gradation pattern film.

(65) Then, it was obtained a pattern image of cyan color by heating for 5 seconds using a hot plate of 120 C.

(66) By exposure to white light of the pattern image obtained, a change in the contrast of the pattern image was observed.

(67) The evaluation was done by the following criteria.

(68) : There was no change.

(69) X: Change was observed.

(70) (8) Smell

(71) During producing the photosensitive film at the time of (7) Image evaluation, and the heat development, the presence of smell was confirmed by a functional test. Evaluation based on the following criteria.

(72) : Smell could not be felt.

(73) X: Smell was felt.

(74) TABLE-US-00001 TABLE 1 Polyvinyl alcohol Polyvinylacetal resin Saponification Mixing Acetyl group Hydroxyl group Acetalization Bulk specific Polymerization degree ratio Polymerization content content degree gravity degree (mol %) (Wt %) degree (mol %) (mol %) (mol %) (g/cm.sup.3) Example 1 600 98 50 900 1.7 20 78.3 0.335 800 98 26 1700 98 24 Example 2 600 98 35 900 1.1 25 70.9 0.375 400 98 26 800 98 21 2400 98 18 Example 3 600 98 72 900 1.8 26 72.2 0.42 1700 98 28 Example 4 400 98 74 900 1.3 24 74.7 0.455 2400 98 26 Comparative 1700 98 100 1700 1.9 30 68.1 0.215 Example 1 Comparative 900 98 100 900 1.2 25 73.8 0.285 Example 2 Evaluation Content of Content of 2-ethyl-2-hexenal ions Na.sup.+/NO.sub.3.sup. Image Handling Skinning (ppm) (ppm) Coloring evaluation Smell Example 1 28 25/20 Example 2 48 70/75 Example 3 33 55/60 Example 4 50 80/90 Comparative X X 137 210/220 X X X Example 1 Comparative X X 140 280/320 X X X Example 2

(75) As shown in Table 1, the obtained polyvinyl acetal resin in Examples 1 to 4, the average of polymerization degree was about 900. Skinning was not observed, the condition of the dry film was good, and the change of the pattern image and the coloring of the coating solution were not observed either.

(76) In addition, the content of 2-ethyl-2-hexenal was low, bad smell could not be felt during thermal development and photosensitive film production.

(77) In contrast, polyvinyl acetal resins obtained in Comparative Examples 1 and 2, the skinning state was observed on the surface of the dry film. There were changes in both the coloring of the pattern image and the coating solution. Smell was detected at the development or during production of the photosensitive film.