GB626844A - A process for producing photo-mechanical printing plates - Google Patents

Abstract

626,844. Photo-mechanical printing surfaces. AKOMFINA AKT.-GES. June 3, 1941, Nos. 7040 and 7041. Convention dates, May 29, 1940, and April 18, 1941. [Class 98 (ii)] The printing surface is produced by treating a plate of metal, or one having a metallic surface, in a lye bath, coating thereon a lightsensitive layer, copying the matter to be printed from a diapositive thereof, developing to remove the unexposed parts of the layer, coating the metal thus laid bare with a solution containing at least one metal salt which reacts with the metal of the plate to form a firmly-adhering metallic layer, preferably applying thereto an ink-receptive varnish coating, and thereafter removing the remainder of the sensitive layer. The ground plate may be of zinc, aluminium or aluminium alloy; the lye bath may contain at least one substance from each of the groups (a) soda, potassium cyanide, calcium chloride, and (b) potassium or sodium hydrate; the sensitive layer may consist of bichromated gum arabic containing a calcium salt (e.g. chloride or hydrosulphite) and formalin or both, and maybe also colouring matter; the metallising substance may consist of an alcoholic solution of one or more of copper chloride or oxide, antimony chloride, oxide, sulphide or sulphate; and the varnish coating may consist of a natural or artificial resin. The bichromated gum layer may be developed with cold water and removed with lukewarm water. The printing layer, when no longer of use, may be removed from the plate with the usual media, e.g. pumice meal, nitric acid, &c., or by the above-mentioned lye, or by a bath containing any or all of chromic, nitric, and hydrochloric acids to which calcium chloride may be added. Reference is made also to procedure commencing with a negative, and to transfer and intaglio work. Specification 23048/39, as open to inspection under Sect. 91, is referred to.