GB534341A - Improved method of producing photographic contasts by means of a diazonium compound - Google Patents

Abstract

534,341. Photographic diazotype processes. PHILIPS LAMPS, Ltd. Jan. 24, 1940, No. 1473. Convention date, Jan. 27, 1939. [Class 98 (ii)] Contrasty relief images are produced in a tannable water-soluble binding agent such as casein or egg albumen sensitized with a diazo compound of the kind which couples with its own decomposition products to form the coloured picture-and also containing a copper salt, by treating the layer after exposure with a chromate solution, the tanning of the exposed parts being effected in part by the chromate and in part by the diazo decomposition products, and thereafter washing away the unexposed parts. In an example, a glass or aluminium plate is cleaned, coated with an aqueous solution of casein containing ammonia, dried, and bathed in a solution containing 1-hydrooxyl-2-diazonium benzene-4-sulphonic acid, copper nitrate and chrome alum. It is then bathed in alcohol, dried, exposed to light, developed and tanned by bathing in potassium chromate solution; and after washing in running water, the unexposed casein is removed with a wet swab. The relief, when dry, may be protected with a coating of celluloid lacquer. Paper may be used as the support. Reference is made to known methods of producing tanned images in diazo-colloid layers, and to Specifications 296,008, [Class 98 (ii)] and 391,970 is referred to.