| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyvinyl acetal resin for a heat-developable photosensitive material which improves the pot life of a solution before coating and the preservability, fog, etc., of a raw film and can improve the definition of an image and of a gradation part, a modified polyvinyl acetal resin for a heat- developable photosensitive material, and a heat developable photosensitive material. SOLUTION: The polyvinyl acetal resin is synthesized by the acetalizing reaction of a polyvinyl alcohol with an aldehyde, has a polymerization degree of 200-3,000, contains 0-25 mol% residual acetyl groups and 17-35 mol% residual hydroxyl group when one acetal group is counted as two acetalized hydroxyl groups, does not contain an antioxidant and has <=100 ppm residual halide content.
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