GB565135A - Improvements relating to photographic processing solutions - Google Patents

Abstract

565,135. Photographic processing solutions. KODAK, Ltd. April 23, 1943, No. 6574. Convention date, Oct. 16, 1942. [Class 98 (ii)] The rate of penetration of a processing solution into an image-recording layer containing a polyvinyl resin as binder is increased by incorporating a thiocyanate in the solution. The layer may be a silver salt emulsion, and the binder a polyvinyl acetal (e.g. an acetaldehyde, propionaldehyde, or butyraldehyde acetal), polyvinyl ester (e.g. partially hydrolyzed acetate), or mixed polyvinyl acetal-ester. The thiocyanate may be added to developing or fixing baths. Inorganic thiocyanates, e.g. sodium, potassium, or ammonium thiocyanate, or organic thiocyanates, e.g. thiocyanocatechol. From 1 to 50 grams of inorganic thiocyanate per litre may be added to a developing solution, and from 50 to 100 grams to a fixing solution. From 3 to 10 grams of sodium thiocyanate may be added to a litre of a metol-hydroquinone developer of specified formula A. The thiocyanates may be used alone as fixing agents, or thiourea may be added. An amine, e.g. ethanolamine or triethanolamine, may be added to the bath, especially the fixing bath, to prevent opalescence in the dried emulsion, or the material may be treated after fixation with an ethanolamine, triethanolamine, ethylene diamine, or alcohol bath: In examples, an emulsion prepared by dispersing silver halide in a solution of a polyvinyl acetaldehyde acetal containing 35 per cent polyvinyl alcohol is (1) developed in developer A containing 10 grams of sodium thiocyanate per litre ; (2) fixed in a bath containing 30 per cent hypo and 100 grams per litre of sodium thiocyanate ; (3) developed in developer A containing 5 grams per litre of sodium thiocyanate and fixed in a bath containing 30 per cent hypo and 100 grams of sodium thiocyanate and 100 cc. of ethanolamine per litre ; and (3) developed in a metol-hydroquinone developer B of specified formula (including citric acid) containing 5 grams per litre of sodium thiocyanate. Specifications 527,283, 531,579, 543,855, and 551,659 are referred to.