GB571802A - Improvements in or relating to photographic diazotype printing processes - Google Patents

Abstract

571,802. Photographic diazotype processes. HALL, HARDING, Ltd., and LEUCH, W. P. Jan. 7, 1944, No. 354. [Class 98 (ii)] In diazotype material to be developed by the dry process in which development is effected by exposure to an alkaline gas or vapour such as ammonia, a light-sensitive layer containing a diazo compound containing an acylamino group, but not any groups (e.g. sulphonic acid groups) conferring greater water-solubility on it, is coated on a paper support and dried and the support is then coated with a solution containing a coupling component and also a salt capable of insolubilizing the diazo compound. The solution of the coupling component may be applied as a separate coating after the insolubilizing salt. The diazo compound may contain two substituted hydroxy groups, e.g. alkoxy groups. Salts specified are stannic chloride, cadmium chloride, zinc chloride, antimony trichloride, aluminium chloride and the corresponding sulphates, and the salts of naphthalene - 1 : 5 - disulphonic and of 2 : 5 - dichlorobenzenesulphonio acids, and (with diazo compounds containing a phenoxyacetylamino group united to the aromatic nucleus containing the diazo group) sodium chloride. In example 1, paper is sensitized with a solution comprising water, the zinc chloride double salt of 4-benzoylamino-2 : 4-diethoxy-1-diazonium chloride, aluminium sulphate and tartaric acid is dried, and is overcoated with a solution comprising water, sodium chloride, tartaric acid, stannic chloride and phloroglucinol. The exposed paper may be developed with ammonia gas. In example 2, paper is sensitized with a solution comprising water, the zinc chloride double salt of 4 - phenylacetylamino - 2 : 5 - diethoxybenzene-1-diazonium chloride, aluminium sulphate and tartaric acid is dried, is overcoated with a solution comprising water, sodium chloride, cadmium chloride and tartaric acid is dried, is further overcoated with a solution comprising water, phloroglucinol, and again dried. Easily crystallizable diazo compounds may be used.