Patent GB-560082-A (GB)
Title: Improvements in sensitive photographic emulsions
IPC: G03C1/12
Filed: 1942-04-28
Abstract: A light-sensitive silver bromide, chlorobromide, bromiodide, or chloro-bromiodide emulsion is sensitized by incorporating in the emulsion up to 4 grams per gram-mole of silver halide of a non-surface-active cyclammonium quaternary salt which contains only carbon and nitrogen atoms in the heterocyclic nucleus embodying the cyclammonium nitrogen atom, and which contains not more than one quaternary nitrogen atom, and in which the heterocyclic nucleus does not bear a substituent containing an aliphatic unsaturated linkage conjugated through the nucleus with the quaternary nitrogen atom, or by incorporating in the emulsion a non-surface-active cyclammonium non-quaternary salt in which only one hydrogen atom is attached directly to the cyclammonium nitrogen atom and only two of the remaining valencies of the nitrogen atom are employed in the formation of the cyclic nucleus, and which contains only carbon and nitrogen atoms in the cyclic nucleus embodying the cyclammonium nitrogen atom and contains at the most only one quaternary nitrogen atom, which if present does not form part of a cyclic nucleus bearing a substituent containing an aliphatic unsaturated linkage conjugated through the nucleus with the quaternary nitrogen atom.  The cyclammonium quaternary salt may be one in which the quaternary nitrogen atom is the nitrogen atom of a pyridine nucleus, e.g. pyridine, quinoline, isoquinoline, and benzoquinoline quaternary salts, or one in which the quaternary nitrogen atom is the nitrogen atom of a reduced pyridine nucleus, e.g. quaternary salts of N-alkyl piperidines, or one in which the quaternary nitrogen atom is the nitrogen atom of a benzimidazole or indazole nucleus.  Aralkyl quaternary (e.g. b -phenylethyl and g -phenyl-n-propyl) salts are preferably employed, and may carry substituents, e.g. alkyl, alkoxy, arylmercapto, carboxyalkyl, halogen, carboxy, or thioalkyl, but usually not nitro, sulphonic acid, sulphonate, and like groups. The salt is incorporated in the emulsion in the form of an aqueous or methyl alcohol solution, e.g. in amount between about 0.2 and 4 grams of salt per gram-mole of silver halide.  The salt may be incorporated in the emulsion before, simultaneously with, or after a sensitizing dye.  Sensitizing dyes are incorporated in methyl or ethyl alcohol or acetone solution.  The salts depress the sensitivity produced by acid sensitizing dyes (containing sulphonic, sulphinic, or carboxylic or like groups or salt forms thereof), and non-acid sensitizing dyes are preferably used.  A supersensitizing combination (e.g. of 3 : 31-diethyl-9-methylthiacarbocyanines with 21-cyanines) of sensitizing dyes may be used.  The use of merocyanine sensitizing dyes is referred to.  The cyclammonium salts are preferably added after washing the emulsions and prior to coating.  Examples specified are a -picoline-b -phenylethyl bromide, g -phenylmercaptopyridine ethiodide, 2-methylquinoline methiodide, 2-methoxyquinoline ethobromide, N-b -phenylethylpyridinium bromide, N - ethyl - 4 - phenylmercaptopyridinium iodide, N-g -phenyl-n-propyl-a -picolinium bromide, N-b -phenylethyl-a -picolinium iodide, N-b -phenylethyl-b -picolinium bromide, N - b  - phenylethyl - g  - picolinium bromide, N-ethyl-6-methylquinolinium iodide, N-ethyl-6-methoxyquinolinium bromide, N - b  - phenylethylquinolinium bromide, N-ethylquinaldinium bromide, N - b  - hydroxyethyllepidinium perchlorate, N - b  - acetoxyethyllepidinium perchlorate, N - benzylpyridinium bromide, N - cinnamylpyridinium perchlorate, N - p - chlorobenzylpyridinium perchlorate, N - cinnamyl - a  - picolinium perchlorate, N - b  - phenylethyl - 3 - carbethoxypyridinium bromide, N - b  - phenylethyl - quinaldinium bromide, N - b  - phenylethylisoquinolinium bromide, N-benzyl-a -picolinium bromide, N-b -hydroxyethylquinaldinium perchlorate, N - b  - phenoxyethylquinaldinium perchlorate, N-benzyllepidinium perchlorate, N-phenacyl-lepidinium perchlorate, N - o - chlorobenzylpyridinium bromide, 4 - methylmercapto - N - phenylpyridinium p - toluenesulphonate, N - benzylquinaldinium bromide, N-methyl - N-g -phenyl-n - propylpiperidinium bromide, N-b -phenylethyl - lepidinium bromide, N - p - chlorophenyl-pyridinium bromide, N-methyl-a -picolinium iodide, N - methyl. - a  - picolinium p - toluenesulphonate, N - b  - phenoxyethyl - a  - picolinium bromide, N - ethyl - 2 - piperidylquinolinium iodide, N - ethyl - 2 - b  - naphthoxyquinolinium iodide, N - ethyl - 2 - b  - hydroxyethylquinolinium iodide, N-benzylquinaldinium perchlorate, N - phenylpyridinium bromide, N - ethyl - g  - phenylmercaptopyridinium p - toluenesulphonate, N - b  - phenylethylpiperidinium bromide, N - methyl - N - b  - phenylethylpiperidinium bromide, N-ethyl-2 : 6-dimethylpyridinium iodide, N-ethyl-2 : 4 : 6-trimethylpyridinium iodide, N-ethyl-4-ethylpyridinium bromide, N - b  - phenylethylbenzimidazolium bromide, g -phenylmercaptopyridine ethiodide, 2-methylquinoline methiodide, 2 - methoxyquinoline ethiobromide and, 1-methyl-b -phenylethylindazolium p-toluenesulphonate.  Numerous sensitizing dyes are referred to. The silver halide emulsion may have a gelatine, cellulose derivative, or resin binder, and may be carried on a cellulose nitrate or acetate, polyvinyl acetal resin, glass, metal, or paper support.  N - (b  - phenylethyl) - piperidinium bromide is prepared by heating piperidine with b -phenylethyl bromide.  Specifications 454,687, 498,290, [Group XX], 513,170, 514,375, 557,178 and 558,710 are referred to.