GB734472A - Improvements in sensitized photographic emulsions - Google Patents

Abstract

734,472. Photographic emulsions. KODAK, Ltd. Nov. 6, 1953 [Nov. 8, 1952], No. 30698/53. Class 98 (2). A light-sensitive silver halide emulsion contains a sulphur sensitizer, a gold salt sensitizer, and either bis-(#-aminoethyl)-sulphide, a watersoluble salt thereof with a non-desensitizing acid, or bis-(γ-diethylaminopropyl)-disulphide. The sulphur sensitizer may be thiourea, di-otolyl thiourea, allyl isothiocyanate, thiocarbanilide, sodium thiosulphate, thioacetamide, or allyl thiourea, the gold salt sensitizer may be potassium chloroaurate, gold chloride, or potassium aurothiocyanate, and the watersoluble salt of the bis-(#-aminoethyl)-sulphide may be the acetate, carbonate, sulphate, or hydrochloride. The sensitizers may be incorporated into the emulsion at any stage, but preferably before completion of digestion, it being preferred to partially digest the emulsion after the addition of the sulphur and gold salt sensitizers and to finish digestion after addition of the organic sulphide. Speed, gamma, and fog data are given for emulsions containing (a) allyl thiourea and potassium chloro-aurate; (b) and (c) as (a) plus bis-(#-aminoethyl)-sulphide dihydrochloride in different quantities; (d) , as (a) with a different emulsion; and (e) and (f) as (d) with bis-(#-aminoethyl)-sulphide in different quantities. The emulsions, which may have various binders and may be coated in single- or multi-layer coatings, may contain anti-fogging and spreading agents and colour couplers. Specifications 570,393, 631,243, 636,140 and 664,230 are referred to.