Lithographic Offset Master for Electroerosion Writing
Original Publication Date: 1985-Jun-01
Included in the Prior Art Database: 2005-Feb-18
Methods developed to prolong the printing life of lithographic masters for electroerosion writing have met with limited success. This disclosure describes fabrication of a multilayered offset plate having a black (light absorbent), hydrophilic (ink repellent) and water-insoluble basecoat, and two processes for preparing the basecoat. After electroerosion writing on the plate, the hydrophilic basecoat is made hydrophobic (water repellent) and ink receptive selectively in the written areas by infrared heat treatment. The nonwritten areas remain hydrophilic. After a normal press run (500-1000 copies), which wears off the aluminum layer of a conventional plate, the hydrophilic basecoat continues to prevent inking in the nonimage area, allowing for several thousand additional copies. Fig.