| 摘要 |
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.%.
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