Patent GB-500829-A (GB)
Title: Improvements in or relating to the electrolytic production of printing forms
IPC: B41C1/10
Filed: 1937-12-20
Abstract: 500,829. Printing-surfaces. HUGENTOBLER, W. Dec. 20, 1937, No. 35231. Convention date, Dec. 23, 1936. Drawings to Specification. [Class 100 (ii)] Flat or curved planographic printing-surfaces are prepared by applying to a non-porous iron surface, which has been ground flat, a layer of non-corrodible metal such as nickel, applying a printing-image to the nickel layer and covering the image with a coating of lacquer, electrolytically depositing a metal on the exposed portions of the nickel, removing the lacquer, and treating the block produced so that one part becomes colour-receptive and the other colour-repellent. The nickel layer is applied electrolytically to the iron base, and, in one modification, a thin layer of copper and a layer of zinc are superposed. An image is applied photographically to the zinc layer and the non-image portions are covered with a coating of gum. A solution of asphalt lac and Canadian balsam in rectified turpentine is then applied over the whole surface, and on washing, the gum and overlying lac are removed. The plate is degreased by sponging with a solution of caustic alkali and potassium cyanide in dilute ammonia, and a layer of zinc is then electrolytically deposited on the exposed portions, the upper surface of the zinc layer being level with the top ofthe lac coating; finally a layer of chromium is deposited. The plate is coated with gum, and the lac and overlying gum removed by a solvent such as turpentine. The bare metal at the image portions is washed with oil of cloves, and coated with Syrian asphalt dissolved in turpentine, and printing-ink is rolled on. The gum coating and overlying ink are removed and the exposed metal is etched to render it colour-repelling. In a modification, a thick layer of copper is applied to the nickel surface, and if not for immediate use is coated with gum arabic to prevent oxidation. The surface is cleaned before use, the image is applied, coated with a layer of asphalt and Canadian balsam in rectified turpentine which is removed from thenon-image areas, cleaned, and a layer of antimony or lead is applied electrolytically up to the level of the surface of the lacquer. The whole surface is coated with gum, the lacquer removed, and a layer of asphalt in turpentine is applied, being subsequently removed from the non-image areas with the gum by washing. It is again coated with gum, then rolled up with printing-ink which is removed from the non-image areas, these areas being etched with a mixture of nitric and sulphuric acids to render them water-receptive. If a reversed image is required, a layer of lead, antimony, or an alloy thereof is applied to the nickel layer, the image is applied and covered with asphalt lacquer, and a final layer of copper is electrolytically applied. In a further modification, the layer of nickel is coated with copper or brass, the image is applied, coated with lacquer, a further layer of nickel is applied to the non-image areas, and the plate is then prepared for printing in the usual way. When the surface is no longer required, it is cleaned from adhering colour by benzene or turpentine and is then immersed as an anode in an electrolytic bath of the same composition as that in which the layer was applied, and is treated for the same period of time.