GB715196A - Improvements in or relating to the production of photographic images by migratory transfer - Google Patents

Abstract

715,196. Photographic images by migratory transfer. OZALID CO., Ltd., and MURRAY, H. D. April 17, 1952 [April 17, 1951]; April 18, 1951], Nos. 8954/51 and 9044/51. Class 98(2) An exposed silver halide emulsion, preferably of high contrast silver chloride type, is maintained in contact with a transfer material containing colloidal hydrated copper sulphide as nuclei in presence of a developer containing a silver halide solvent for a time sufficient for transfer and reduction of silver halide in the unexposed areas and thereby production of an image, usually a positive. in the transfer material. The transfer material may contain, additionally, a high energy developer such as hydroquinone or this with metol. a silver halide solvent such as hypo, a restrainer such as a soluble bromide, a colour improver or toning agent such as mercaptobenzthiazole and a plasticizer such as glycerin. In one form of the invention a proportion, or all, of the high energy developer may be incorporated in the negative material. Preferably the copper sulphide for the transfer material is made by precipitation in presence of a protective hydrophilic colloid; thus in example 1 copper sulphate in solution in water with gelatin is precipitated with a slight excess of sodium sulphide and a portion of the suspension with more gelatin and a little formalin diluted with water is coated onto paper and dried to form the transfer material; and this, along with an exposed photographic paper carrying a silver chloride emulsion containing a proportion of hydroquinone equal to one quarter of the silver nitrate used in preparing the emulsion. is immersed in a water solution of caustic soda and sodium sulphite and the two papers in face to face contact are passed.through a pair of nipping rollers and separated after one or two minutes to leave a positive image on the transfer paper. A second example describes an aqueous composition comprising colloidal hydrated copper sulphide, sodium thiosulphate. hydroquinone, glycerin and formalin for preparation of the transfer paper and aqueous caustic soda, sodium sulphite and potassium thiocyanate for the immersion solution, leading to a dark brown or black positive image on the transfer paper. Specifications 614,155 and 654.630 are referred to.