GB1229243A - - Google Patents

Abstract

1,229,243. Engraving; printing surfaces. CROSFIELD ELECTRONICS Ltd. 28 May, 1969 [29 May, 1968], No. 25787/68. Headings B6C and B6J. [Also in Division H4] An intaglio printing plate is formed from a metal blank 10, Figs. 2, 3, by forming e.g. by etching therein cells 11 of the maximum depth required, filling them with a solid material 12 such as polythene, glass or antimony, and scanning the surface of the blank with a laser beam modulated in accordance with the image to be engraved, so as to remove material 12, which is more easily evaporated than the metal, to varying depths, Fig. 2, or, where the filling material is harder near the walls of the cell, to varying depths and areas, Fig. 3. This differential hardening can be achieved chemically by causing catalytically accelerated hardening around the cell edges of an epoxy resin based filler, or by applying a cold thermosetting resin to a heated etched surface so as to get differential curing. Alternatively the cells can be partially filled with hard material and filling completed with a softer material. A photo-multiplier on an analysing head 36, Fig. 4, is exposed to light through a prism 30 and an original transparency on a cylinder 20, the head 36 and prism 30 being reciprocated axially of the cylinder while the latter rotates to scan the transparency. The output from the multiplier is passed through a tone or colour correction computer 50 to a laser modulator in a head 46 which moves with the head 36 to scan the blank 10 on a rotating cylinder 22 and selectively remove the material 12. The cylinder scanner may be replaced by an oscillating table scanner.