Improvements in or relating to photoresists

1,153,185. Photo-resists. GENERAL ANILINE & FILM CORP. June 13, 1966 [July 6, 1965], No. 26163/66. Heading G2C. Coloured photo-resists are prepared by coating a support with a photo-polymerizable, non- oxidizing material containing a leuco dye, imagewise exposing to visible light, applying an aqueous oxidizing solution to convert the leuco dye to a dye, and removing the material in the unexposed areas. Suitable leuco dyes are those of the phenazine, thiazine and pherathiazine types. In the Examples a mixture of acrylamide, N, N'-methylenebisacrylamide, ferric ammonium oxalate, hydroxyethyl cellulose, the disodium salt of ethylene diaminetetraacetic acid and a leuco dye formed by the reduction of methylene blue or thionin with ferrous ammonium sulphate, is coated on paper, exposed, oxidized with aqueous H 2 O 2 and developed with water.