Patent ID: 7018777

Claim:
A method of making a lithographic printing plate from a heat-sensitive pre-sensitized plate of a positive-working mode for lithographic printing comprising the steps of: exposing the heat-sensitive pre-sensitized plate to light, and developing the plate using an alkaline developing solution comprising (a) at least one surfactant selected from the group consisting of anionic surfactants and ampholytic surfactants in an amount of 0.001 to 10% by weight, and (b) at least one salt selected from the group consisting of alkali metal salts and salts of an ammonium cation, wherein the pre-sensitized plate comprises a substrate, a lower layer which comprises a water-insoluble and alkali-soluble resin, and an upper heat-sensitive layer which comprises 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, said lower layer and said upper heat-sensitive layer being located on the substrate in this order.