GB707959A - Vesicular prints and process of making same - Google Patents

Abstract

707,959. Photographic diazo layers for vesicular prints. DIXON, M. G. (General Aniline & Film Corporation). Dec. 16, 1952, No. 31864/52. Class 98(2) A support is coated with an aqueous dispersion comprising 30 to 40 parts of a hydrophilic colloid, 3 to 10 parts of a finely divided solid having an index of refraction similar to that of the colloid, and a stabilized photosensitive diazonium compound; and dried. On exposure light affected areas release gas, and on development by heat, moisture or steam the colloid softens to permit formation of minute vesicles which can refract light to cause an appearance of whiteness by reflected light and darkness by transmitted light. In a specific embodiment of the invention the support is black paper, the colloid gelatin, the finely divided solid precipitated barium sulphate, and the diazonium compound the zinc chloride double salt of p-diethylamino benzene diazonium chloride. Thiourea and citric acid also are present in the coating dispersion. Ultra-violet exposure through a positive transparency requires 30 seconds as against 70 seconds in absence of the barium sulphate to produce equal density on steam development. A glass support instead of the black paper results in a negative print. In variations the support may be regenerated cellulose, cellulose acetate or metal; the colloid may be glue, casein, fish glue, gum tragacanth, starch, dextrin, albumin, polyvinyl alcohol, urea- or melamine formaldehyde resin; the solid bentonite, colloidal silica, or calcium sulphate or silicate; the diazonium compound a diazo oxide, a diazonium compound derived from para-amino diphenylamine, the zinc chloride double salt of 4-benzamido-2.5-diethoxybenzene diazonium sulphate, of diazotized 3-aminocarbazole or of p-diethylamino-o - ethoxybenzene diazonium chloride; or the cadmium chloride double salt of p-dimethylaminobenzene diazonium chloride or of 2-hydroxy-4-sulphonaphthalene-1-diazo anhydride. Other acidic stabilizers are indicated. The final print may be given a hydrophobic coating as of wax. Specifications 524,786, 636,144, 645,825 and 647,617 are referred to.