JPS6490748A - Thermal processing method in plate making - Google Patents

Abstract

PURPOSE:To obtain a printing original plate capable of obtaining a clear image, by a method wherein a thermal means is, in an image state, processed on a surface of a lithographic printing original plate prepared by forming a hydrophilic multi layer part by successively laminating a metal deposition layer, a hydrophilic layer having an affinity with the metal deposition layer and a protective thin film layer on a base material having an ink-sensitized layer, and the hydrophilic layer is removed. CONSTITUTION:A lithographic printing original plate to be used is prepared by laminating successively an ink fat sensitive layer 2, a metal deposition layer 3, a hydrophilic layer 4, and a protective thin film layer 5 on a base material 1. The metal deposition layer 3 is a thermal recording layer, and vaporization of a hydrophilic metal of a low melting point is preferable. The hydrophilic layer 4 has affinity with the metal deposition layer 3, and silicate and phosphate can be exemplified. The protective thin film layer 5 is established for protecting surface of the hydrophilic layer 4 and the metal deposition layer 3. The original plate of the lithographic printing is prepared as follows. A hydrophilic multi layer part composed of the metal deposition layer 3, a selected part of the hydrophilic layer 4, and the protective thin film layer 5 overlapping with said part is destroyed with a heat source such as thermal head and laser beams to prepare a plate. thereafter, the protective thin film layer 5 on the surface is washed away to be thoroughly removed by solvents such as water or the like, and the hydrophilic layer 4 is exposed, which is taken as the lithographic original plate.