Photographic polymeric resist images

926,583. Photographic polymeric images. GENERAL ANILINE & FILM CORPORATION. Sept. 21, 1961 [Oct. 10, 1960], No. 33858/61. Class 98 (2). A positively operating method of producing resist images comprises exposing a composition of an ethylenically unsaturated polymerizable compound, a colloid carrier and a diazo compound; applying a salt of a divalent metal in its lower oxidized state and a per compound having the grouping -O-O- to effect polymerization in the unexposed areas only, and removing unpolymerized photo-sensitive composition in the exposed areas. It is conjectured that the exposed diazo compound inhibits polymerization in the presence of this salt and per compound. Either of these may be initially present in the composition, thus in Example I a composition comprising gelatin, citric acid, N,N1-methylene-bis-acrylamide, ferrous ammonium sulphate and the zinc double salt of diazotized N,N1-hydroxy diethyl p-phenylenediamine on a polycarbonate base is exposed for two minutes through a positive transparency, treated in hydrogen peroxide solution and then bathed in warm water, to leave a positive resist which may be dyed with naphthylamine black. Example II describes the procedure with a composition omitting the ferrous ammonium sulphate, for application of this after exposure and following with hydrogen peroxide; and Examples III, IV have further slight variations. Extensive lists of the several materials used are provided, and uses of the method include multicolour procedure by superimposition, and especially printing plate production of which many types are referred to.