GB530445A - Improvements in the production of photo-mechanical printing plates - Google Patents

Abstract

530,445. Producing photo-mechanical printing-surfaces. LENGEL, A. L. June 5, 1939, No. 16464. Convention date, June 6, 1938. [Class 98 (ii)] A flexible metal printing plate for printing picture and textual matter on rotary presses is produced by preparing a half-tone ground film, inserting a half-tone picture film into an appropriate aperture there, preparing a separate film of text matter (e.g. type) and successively printing the composite half-tone film and the text film on to the entire area of the sensitized flexible metal plate. The ground film is prepared by photographing a white surface through a half-tone screen with fifty or less lines to the inch. The picture matter is photographed through a half-tone screen with eighty-five or more lines to the inch and the films thus prepared are trimmed to the desired dimensions and inset into apertures of the correct size in the ground film, which is placed on a glass sheet. A transparent sheet is placed over the ground film, and text matter, including line drawings, on an opaque medium is arranged thereon in register, and, after removal of the transparent sheet from the ground film the text thereon is photographed from the rear. The two films, one containing the picture matter and dotted ground, and the other the text-matter, are then printed in succession on to a sensitized thin flexible metal sheet, which may be of zinc or jem metal. The plate is rolled up and lightly etched. Opposite edges of the plate may be bent to form a flange which may be perforated at several points to enable its use in a rotary web perfecting press. The first of the two printing cylinders may carry ordinary stereotype plates. Matrices may be made from the plates and stereotype plates cast therefrom. The plates may be used for colour-printing, either alone or in combination with stereotype plates.