| 摘要 |
PROBLEM TO BE SOLVED: To provide a positive original plate for a planographic printing plate for an IR laser for direct plate making excellent in development latitude in image formation, suppressing defects due to a flaw in an image area and capable of attaining uniform image reproducibility in the surface and to provide a plate making method for a planographic printing plate. 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 upper heat sensitive layer contains at least two surfactants or both the underlayer and upper heat sensitive layer separately contain different surfactants and the original plate is imagewise exposed and then developed with an alkali developing solution. |
