| 摘要 |
PURPOSE: To improve development stability when both of a negative and a positive photosensitive printing plates are commonly developed and to improve the elution of aluminum from a base body by treating a photosensitive planographic printing plate with an alkali silicate soln. of a specified pH before development. CONSTITUTION: This method includes a processing zone (A) where a photosensitive planographic printing plate is horizontally carried and subjected to pre-development, a developing zone (B) where the plate is treated with a developer of pH>=12.5 containing water as the main solvent, and a cleaning zone (C) where the plate is cleaned with water, in this order. The device is prepared by filling the pre-developing tank 2 with a pre-developing liquid such as 1% potassium silicate soln., a developing tank 8 with a developer, and cleaning tank with tap water. A negative or a positive photosensitive planographic printing plate is processed under conditions, for example, at 25 deg.C for 3sec for the pre-development, at 32 deg.C for 10sec for development, and at room temp. for 3sec for cleaning. Thereby, the range for the developing time is almost the same for both of a negative and a positive photosensitive planographic printing plates, and therefore, development stability is improved when both printing plates are developed. |
