Method and apparatus for producing consistent thickness cap resin layers

Abstract

Printing plates are formed from a layer of photo polymerizable resin by a process and assembly which includes a negative of the image or images to be formed in the printing plate. The negative is placed on a lower glass support plate and a bank of lights is disposed below the lower glass support plate. A cover film is laid down on the negative, and a very thin layer of resin, called a cap resin, is deposited on the cover film. A layer of the resin to be cross-linked is deposited on the cap resin layer, and the cross-linked resin layer is covered with a polyester sheet, on the top of which an upper glass plate is lowered. The cap resin layer and the cross-linked resin layer are both laid down on the lower glass plate assembly by meas of a carriage assembly that traverses over the lower glass plate assembly, and which carries the cross-linking resin and cap resin reservoir. The thickness of the cross-linked resin layer varies widely, while the thickness of the cap resin layer is narrowly confined. The carriage assembly is provided with a cap resin doctor blade that is maintained a constant distance above the lower glass plate, irregardless of the spacing between the cross-linked resin layer reservoir on the carriage assembly and the lower glass plate. In this manner, a constant thickness cap resin layer can be deposited on the lower glass plate in conjunction with different thickness cross-linking resin layers.