| 摘要 |
PROBLEM TO BE SOLVED: To provide a positive original plate for a planographic printing plate for direct plate making adaptable to an IR laser recording system and excellent in scuffing resistance and to provide a plate making method. SOLUTION: The original plate has an underlayer containing a water-insoluble and alkali-soluble resin and an upper heat sensitive layer containing a water- insoluble and alkali-soluble resin and an IR absorbing dye and having solubility in an alkaline aqueous solution increased by heating in order on a hydrophilic support, the surface hardness of the upper heat sensitive layer is >=0.50 GPa and the original plate is imagewise exposed and then developed with an alkali developing solution. |
