| 摘要 |
PROBLEM TO BE SOLVED: To provide an image exposure method for computer-to-plate applied to an ordinary positive PS plate using a quinone diazide compound as an image exposure method for a positive type photosensitive planographic printing plate in which a comparatively low output laser is used. SOLUTION: In this method; a photosensitive layer containing a positive photosensitive compound is provided on an aluminum supporting body at least sandblasting and anodizated and the positive type photosensitive planographic printing plate is image-exposed. At such a time, (1) full exposure where the plate is exposed with exposure under the exposure where residual film rate in gamma characteristic after the development of the photosensitive planographic printing plate is 0%, (2) scanning exposure where the plate is exposed while performing modulation according to a digital signal based on image data are performed. A laser beam whose wavelength is 400 to 450 nm is used and the scanning exposure where the plate is exposed with the exposure equal to or over the exposure, where the above defined residual film rate in the sum of the exposure in the above scanning exposure and that in the full exposure is 0% is performed. |
