| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a plate making method of a lithographic printing plate based on a positive lithographic printing original plate for IR laser for direct plate making by which sensitivity and developing latitude are excellent during forming an image, occurrence of defects due to scratches in an image in a unexposed part is suppressed and a favorable image can be formed. <P>SOLUTION: The plate making method of a lithographic printing plate is carried out by imagewise exposing the following positive lithographic printing original plate to IR rays in an image and then developing with an alkali developer containing (a) at least one kind of primary or secondary amine having an acidic group with ≤10 pKa, (b) a compound having a buffer effect and (c) a basic compound. The original plate has (ii) a lower layer containing a water-insoluble and alkali-soluble resin as the main component and (iii) a thermosensitive layer which contains a water-insoluble and alkali-soluble resin and an IR absorbing dye and which increases the solubility with an alkaline aqueous solution by exposure to IR laser light, both layers formed on (i) a support having a hydrophilic surface. <P>COPYRIGHT: (C)2004,JPO |
