Printing master plate prodn. without film edge trace - in which transparent positive film on transparent carrier is coated with light-diffusing layer at areas corresp. to film edges

摘要

A transparent positive film (2) fixed and adhering to a transparent carrier film (1) is placed in closed contact on a photo-sensitive, photo-solubilising layer of a printing element. A light-diffusing layer is then formed at parts corresp. to the film edges of (2), on the side of (1) facing incident exposure-light, so that no film edge trace is optically reproduced on the exposed, developed printing master-plate. Prodn. is suitable for use as a positive lithographic printing plate.