Method of making lithographic printing plate

摘要

A method of making a printing plate from a heat-sensitive PS plate of a positive-working mode for lithographic printing includes the steps of exposing the heat-sensitive PS plate to light and developing the PS plate using an alkaline developing solution containing at least one surfactant selected from the group consisting of anionic surfactants and ampholytic surfactants, and a salt selected from the group consisting of alkali metal salts and ammonium cation salts. The PS plate has a substrate and an image forming layer formed thereon, the image forming layer including a lower layer which is formed on the substrate and contains a water-insoluble and alkali-soluble resin and an upper heat-sensitive layer which is overlaid on the lower layer and contains a water-insoluble and alkali-soluble resin and an infrared absorption dye and exhibits an elevated solubility with respect to alkaline aqueous solutions when heated.