To provide an easy evaluation method for easily judging the platemaking conditions of a positive lithographic printing original plate for IR laser for direct plate making, in particular, for judging the activity state of a developing solution, and to provide a quality control method for keeping the quality of the lithographic printing plate constant by using the evaluation result as a feedback to the exposure/development process.
The evaluation method includes processes of: (A) exposing a lithographic printing original plate having a photosensitive layer comprising a resin which is soluble with an alkali aqueous solution and a compound which absorbs light to generate heat, on a supporting body under the conditions of forming dots of 10 to 75 μm diameter with 30 to 70% area rate by a FM screen method, and then developing the plate with a standard developing solution to prepare the lithographic printing plate treated with the standard developing solution; (B) preparing a lithographic printing plate treated with the objective developing solution under the same conditions as in the process (A) except that the plate is developed with the developing liquid to be evaluated; and (C) comparing the dot area rates in the lithographic printing plate treated with the standard developing solution and in the lithographic printing plate treated with the objective developing solution.
KOBAYASHI FUMIKAZU
Kato Kazunori
Katsuichi Nishimoto
Hiroshi Fukuda