| 摘要 |
PROBLEM TO BE SOLVED: To improve erasing property of a photosensitive layer in a correcting process in the production of a printing plate containing a high mol.wt. novolac resin, and to improve easy contamination in a nonpicture part, by forming a specified positive photosensitive layer on an aluminum plate or aluminum alloy plate which is first subjected to anodic oxidation treatment and then to AC electrolysis under specified conditions. SOLUTION: In the production of a photosensitive lithographic printing plate having a positive photosensitive layer containing a phenol/p-cresol aldehyde resin with >=7000 weight average mol.wt. as a binder component, an aluminum or aluminum alloy plate treated by anodic oxidation is subjected to AC electrolysis in a soln. containing a metal salt with 0.01 to 5.0 A/dm<2> current density for 1 to 150 sec. In the AC electrolysis under the conditions above described, the metal, its hydroxdies. etc., in the metal salt soln. properly crystallizes in the micropores of the anodic oxidation film of the supporting body and properly seals the pores. Thereby, erasing property of the photosensitive layer and easy contamination in a nonpicture part in the production of a printing plate are improved. |
