GB430357A - Process for sensitising photographic silver halide emulsions - Google Patents

Abstract

Silver halide emulsions are sensitized by means of benzoxocarbocyanine dyes substituted in one or both benzene rings, and having no substituent in the trimethine chain, other than a benzoxocarbocyanine dye substituted in each of the positions 5 and 6 or 5<1> and 6<1> or in all four positions. Suitable substituents are alkyl, hydroxyl, alkoxy, amino, substituted amino, or aryl groups or halogens. Examples are given of the preparation of (1) 1 : 1<1>-dimethyl5 : 5<1>-di-(dimethylamino)-benzoxocarbocyanine iodide by heating 6-dimethylamino-2-methylbenzoxazole dimethylsulphate with orthoformic ester in pyridine and precipitating the dye with potassium iodide; (2) 1 : 1<1>-dimethyl-5 : 5<1>-dihydroxybenzoxocarbocyanine perchlorate by heating 2 - methyl - 6 - hydroxybenzoxazole dimethylsulphate with triethyl orthoformate in pyridine and precipitating the dye with sodium perchlorate; (3) 1 : 1<1>-dimethyl-6 : 6<1>-dichlorobenzoxocarbocyanine iodide by heating 2-methyl-5-chlorobenzoxazole methiodide with triethyl-orthoformate in pyridine and adding potassium iodide; (4) 1-methyl-1<1>-ethyl-6-methoxybenzoxocarbocyanine iodide by heating 2-methylbenzoxazole ethiodide with diphenylformamidine in acetic anhydride and condensing the product with 5 - methoxy - 2 - methylbenzoxazole methiodide in pyridine and piperidine. Specification 418,745 is referred to. The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 28561/34. This subject-matter does not appear in the Specification as accepted.