| 摘要 |
PURPOSE: To produce a letterpress printing plate which gives a sharp printed image with a small print gain by leaving the plate to stand for a specified period after back exposure being a primary exposure of the plate and then subjecting the plate to relief exposure. CONSTITUTION: A negative film 3 and a cover film 4 are laminated on a transparent substrate 1 and the that the negative film 3 is tightly adhered in vacuum state to the transparent substrate 1 by using holes and grooves formed in the transparent substrate 1 and vacuum pipings. Then a photosensitive resin layer 5 is laminated thereon, on which a base film 6 and a masking film 7 are laminated. Then a transparent substrate 2 is placed on a spacer 8 which is set to decide the thickness of the photosensitive resin plate. Then the photosensitive resin is irradiated with active rays for back exposure (masking exposure) through the transparent substrate 2 to form the base part of a relief part. Then the plate is not exposed for one minute, preferably for two minutes (standby time for relief exposure), the plate is irradiated with active rays for relief exposure through the transparent substrate 1 and the negative film 3. |
