GB961490A - Improvements in photographic emulsions - Google Patents

Abstract

961, 490. Photographic emulsion binders. E. I. DU PONT DE NEMOURS & CO. Aug. 24, 1962 [Aug. 28, 1961], No. 32673/62. Heading G2C. Light-sensitive silver halide emulsions are characterised in that the binder comprises a mixture of gelatin and an aqueous dispersion of a polymer of an olefinically unsaturated monomer which dispersion contains an anionic dispersing agent A-B wherein either (i) A is a C 8 or higher straight chain alkyl radical and B is -O m -SO 3 M or -COOM, M being ammonium or an alkali metal and m 0 or 1 or (ii) A is where R<SP>1</SP> is a C 4 or higher branched alkyl radical and n is 1 to 12, and B is -O m -SO 3 M, and in that the emulsion also contains a polyoxyethylene compound RO(CH 2 CH 2 O) n R 1 wherein R is H, C 1-18 alkyl, C 7-18 alkaryl, C 6-12 aryl, or C 7-18 aralkyl, R<SP>11</SP> is H or C 1-3 alkyl and n is 6 to 2, 500. The emulsion may also contain an amphoteric dispersing agent RNH p [(CH 2 ) n COOM] m wherein R is unsubstituted C 12-18 alkyl, m and n are 1 or 2,p is (2-m) and M is Na, K, NH 4 or H, e.g. the sodium salts of N- tallow or dodecyl-beta-iminodipropionic and of N-alkyl beta-aminopropionic acids. Other polyoxyethylene compounds may also be present in addition to that of the specified formula. Specified polymers are polymers and copolymers of methyl, ethyl, butyl or ethylhexyl acrylate or methyl or butyl methacrylate with up to 10% mole acrylic acid and of vinyl acetate and propionate, vinyl and vinylidene halides, styrene and substituted styrenes, dienes such as butadiene, acrylonitrile, and alkenes such as ethylene and propylene. The following are used in specific Examples; homopolymers of ethyl, methyl and butyl acrylates and styrene and a copolymer or vinylidene chloride with 2-ethylhexyl acrylate. Specified anionic dispersants are sodium lauryl sulphate. potassium cetyl sulphonate, ammonium octyl sulphate, sodium octadecyl sulphonate, sodium salts of isooctyl phenyl polyether sulphates and sulphonates, potassium stearate, ammonium laurate and sodium palmitate. The emulsion may contain usual adjuvants such as emulsion sensitizers, e.g. alkyl thioureas and isothiocyanates, phenyl isothiocyanate or sodium thiosulphate; metal compounds, e.g. of gold, platinum, palladium, iridium, rhodium, mercury, cadmium or thallium; antifoggants, e.g. 2-mercaptobenzothiazole, 1- phenyl-5-mercaptotetrazole, benzotriazole, triazindenes, tetrazindenes and 5-nitrobenzimidazole; sensitizing dyes; hardeners, e.g. aliphatic aldehydes, dimethylol urea and trimethylol melamine; chromium compounds, e.g. chrome alum; matting agents; and image colour modifiers. The emulsions are stated to be especially useful for lithographic films; with additives such as silica the emulsions are useful for offset plates. A long list of possible supports is provided, hydrophobic supports being stated to be preferred. Specifications 580,504, 592,676, 718,422 and 786,176 are referred to.