To provide a platemaking method for easily obtaining a key plate and a platemaking method by which both of a planographic printing plate and a key plate can be supplied in the same platemaking system without decreasing developing property even when the setting of a replenisher amount is constant in the platemaking system.
The platemaking method for obtaining a key plate is carried out by developing a planographic printing original plate having sensitivity to IR rays without exposing. Otherwise, a layered body comprising two or more planographic printing original plates having IR sensitivity is continuously processed in the same platemaking system to result in a planographic printing plate and a key plate. A part of the layered body is processed into the planographic printing plate by imagewisely exposing to IR rays and developing, while the other part of the layered body is processed into the key plate by developing without imagewisely exposing to IR rays. Further, at least one plate in 100 planographic printing original plates subjected to the continuous process is the plate made as the above planographic printing plate.
Kato Kazunori
Katsuichi Nishimoto
Hiroshi Fukuda
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