GB539412A - Improvements in the production of photo-mechanical printing plates - Google Patents

Abstract

539,412. Producing photo-mechanical printing plates. LENGEL, A. L. June 5, 1939, No. 15555/40. Convention date, June 6, 1938. Divided out of 530,445. [Class 98 (ii)] A low relief printing plate produced by lightly etching to a depth of between 0.005 and 0.007 of an inch thin metal, for example zinc or jem metal, readily flexible about a plate support and of a thickness between 0.020 and 0.027 of an inch has throughout the etched non-printing areas uniform dots produced by exposure through a half-tone screen to a surface of uniform' light tone, the dots serving merely as mechanical supports for the inking rollers and web in a rotary web perfecting press. In the production of the plate, a negative is made on a film by photographing a white surface through a coarse half-tone screen. The picture matter is photographed through a fine half-tone screen on to one or more films which are then inset into appropriate apertures on the first film, which is mounted on a glass plate. A transparent film is placed over the combination, and text, type and line drawings are placed in this sheet and photographed from the rear to reverse the lettering, and obtain a film in which the text &c. are represented by transparent areas and the rest of the film is opaque. This latter film and the combination film are then successively printed in either order on a sensitized flexible metal sheet, which is then " rolled up" and etched. Flanges may be provided on the plate for direct attachment to a printing cylinder. Where opposite sides of the web are printed on, ordinary relief type plates, if used, should be on the first printing cylinder and the plates according to the invention on the second cylinder. The plates may be used in multi-colour printing, either alone or in combination with ordinary relief type plates. Stereotype plates may be made from the plates according to the invention. Specification 345,255 is referred to.