| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for making a lithographic printing plate of a positive lithographic printing original plate by which sufficient sensitivity under the exposure conditions of low speed and low exposure light quantity is obtained, the difference in solubility (so-called solubility discrimination) between an unexposed part and a exposed part is increased to improve the development latitude and a favorable image can be formed. <P>SOLUTION: The method for making a lithographic printing plate includes processes of image exposing a positive lithographic printing original plate having at least two layers of an image forming under layer on a supporting body and an image forming upper layer on the image forming lower layer by using a laser beam and developing the plate by using an alkaline developing solution. The method features that: in the exposure process, the time the laser beam stays on a pixel is 2.0 to 20 μsec; the total coating amount of the image forming lower layer and the image forming upper layer ranges from 1.2 to 3.0 g/m<SP>2</SP>; the dissolving rate of the positive lithographic printing original plate with the alkaline developing solution under the unexposed condition is higher in the image forming lower layer than in the upper layer; and the alkaline developing solution contains at least one kind of compound having a function to decrease the dissolving rates in an unexposed part of the image forming layer to in an exposed part of the image forming layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
