| 摘要 |
PURPOSE:To erase an unnecessary picture, on a planographic printing plate, which has a photosensitive layer containing a photo-cross-linking polymer and a photopolymerizing polymer, by using an erasing agent which contains an organic solvent and alkali hydroxide without leaving bleeding at a place except at an erasure place and corroding a base. CONSTITUTION:A 50-99wt% organic solvent of alkali hydroxide, such as KOH and NaOH, and a kind of ketone, a kind of ester, aromatic hydrocarbon, etc., specially, univalent alcohol or benzine alcohol of C6-10 is mixed, and a small quantity of a surface active agent, a thickener, etc., are added to prepare an erasing agent. An unnecessary picture part, such as a flaw and an edge, on a photosensitive planographic printing plate which has a photosensitive layer containing a photo-cross-linking or photopolymerizing polymer, such as a photosensitive polymer, having cinnamic acid at a principal or side chain is applied with the said erasing agent with a painting brush and, after being left for a while, washed away. Thus, excellent erasure is performed without corroding a base and causing bleeding in an adjacent picture at the unnecessary picture part. |
