| 摘要 |
PROBLEM TO BE SOLVED: To obtain the manufacturing method of a positive-action planographic printing plate having such excellent printing quality that a developing action can be executed by a simple biological method by using a specified infrared laser beam. SOLUTION: A positive thermosensitive image forming element including a hydrophobic infrared sensitive layer on a planographic base having a hydrophilic surface is exposed to the laser beam according to an image. Then, the image forming element is developed in acrylic developing water solution without executing different processing other than the thermal processing. In this case, the infrared laser beam having pixel residence time being shorter than 0.075μs is used. As an image forming device for exposing the thermosensitive image forming element to the laser beam according to the image, an inside drum or a flat-bed scanner is used. Then, the image forming element is exposed to one or the small number of laser beams having the shorter pixel residence time (0.01-0.075μs). By exposing the image forming element to the laser light beams having the pixel residence time being shorter than 0.075μs, preferably 0.05μs in such a way, the positive-action planographic printing plate with the high quality is obtained. |
