| 摘要 |
470,402. Photomechanical printing- surfaces. SCHLESINGER, A. Feb. 12, 1936, No. 4299. [Class 98 (ii)] [Also in Group XVI] An intaglio plate or cylinder comprises an upper layer which can be etched and of a thickness equal to the maximum depth to which it is desired to etch and an underlayer of a material not attacked by the etching agent, a half tone screen being used to provide variations in tone values. The upper layer may be of metal, e.g. copper or chromium, or other suitable material such as celluloid, and the under layer may be of aluminium, steel or stainless steel, lead or an alloy of lead, or may consist of a flexible material such as cardboard or celluloid so that the plate may be applied to a cylinder. The upper layer may be electrolytically deposited, an intermediate layer, e.g. of nickel, being first applied to facilitate the deposition of the upper layer. In one method of preparation, a base of stel is provided with an electrodeposit of copper of a depth equal to the desired depth of etching and the design is prepared on the copper by coating it with bichromated glue or gelatine and exposing under a half-tone screened positive. After development, the copper is etched with ferric chloride until the steel undersurface appears.
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