GB1283898A - Etching process - Google Patents

Abstract

1283898 Etching NATIONAL CASH REGISTER CO 22 June 1971 [8 July 1970] 29168/71 Heading B6J A method of etching a relief pattern on a surface, e.g. a tool steel printing cylinder, whilst avoiding undercutting comprises applying to said surface a first photoresist layer, exposing it through a mask and removing the unexposed resist portions to leave an area or areas of exposed resist corresponding with said pattern, applying to the said area or areas and to the remaining uncovered portions of the surface a second photoresist layer and exposing this layer through a mask, removing the exposed portions of said second layer to leave an area or areas of unexposed resist covering and extending beyond the edges of said area or areas of exposed resist, etching, e.g. using a mixture of ferrous and ferric chloride sprayed at 45 p.s.i.g. and 130‹ F. for 3 minutes, the uncovered portions of the surface, removing the unexposed resist, e.g. by immersion in caustic soda at 130‹ F. for 60-90 seconds, etching again, e.g. for 6 minutes, and removing said exposed resist, e.g. by immersion in an acidic solution of xylene, methylene chloride and methyl cellosolve acetate. The photoresist may be exposed by ultra-violet light.