METHOD FOR THE PREPARATION OF LITHOGRAPHIC PRINTING PLATES

摘要

A simple and inexpensive method for the direct preparation of offset lithographic printing plates using computer-to-plate methods and an inkjet marking fluid jetted directly onto a printing surface by conventional inkjet systems. The marking fluid is a two-phase emulsion system, comprising an oleophilic inner phase and a continuous, aqueous, external phase. To effectively control the dot size in the image to be printed and advantageously produce long runs of good-quality impressions from printing on a conventional offset lithographic press, the viscosity of the marking fluid used is preselected, and a very thin cationic surfactant coating is applied to the printing surface. Alternatively, a marking fluid having a pre-selected viscosity is used together with a cationic surfactant coating solution applied directly to a printing surface in a plateless lithographic printing system.