Patent GB-394537-A (GB)
Title: Process for sensitizing photographic silver halide emulsions
IPC: G03C1/20
Filed: 1932-10-10
Abstract: Photographic silver halide emulsions are sensitized for red and infra red by incorporating in the emulsion a pentacarbocyanine or heptocarbocyanine dye of the general formula <FORM:0394537/IV/1> y represents S, Se, CH = CH, O or C(CH3)2, n is 2 or 3, r represents alkyl and X an acid radicle such as halide, perchlorate, para-toluene sulphonate, alkyl sulphate or nitrate, and at least one carbon atom of the polymethine chain is linked to an alkyl group, the others being linked to hydrogen.  The nuclei V and V<1> may be substituted by alkyl, alkoxy, hydroxyl, halogen or a substituted amino group and may be replaced by naphthalene, anthracene or phenanthrene nuclei. In the case where y represents CH = CH the polymethine chain may be linked to the heterocyclic rings in para position to the nitrogen atom.  The dyes may be added to the emulsion at any stage of its preparation in solution in an alcohol or alcohol and water mixture; preferably, they are added to the emulsion ready for casting. They may also be incorporated in the emulsion by coating the cast layer with a solution of the dye or bathing it therein.  The dye 1 : 1<1>-diethyl benthio-g -methyl-pentacarbocyanine iodide is prepared by heating 2-methyl-benzthiazoleethyl-iodide with b -ethoxy-a -methyl-acroleinacetal in dry pyridine, the dye being precipitated on addition of water.  The corresponding selenium dye is prepared in a similar manner.  In further examples, (1) the dye 1 : 1<1>-diethyl-5 : 5<1> - bisacetylamino - benzthio - g  - methyl-pentacarbocyanine monoethyl sulphate is prepared by heating 2-methyl-6-acetylaminobenzthiazole-diethyl sulphate (made by acetylating 2-methyl-6-aminobenzthiazole described in Specification 313,293, [Class 2 (iii), Dyes &c.]), with b -ethoxy-a -methyl-acrolein-acetal in pyridine; (2) the dye 1 : 1<1>-diethyl-5 : 6 : 5<1> : 6<1>-tetramethoxy - benzthio - g  - methyl - pentacarbocyanine iodide by heating 2-methyl-5 : 6<1>-dimethoxy-benzthiazole ethyl iodide with b  - methoxy - a  - methyl - acrolein - acetal in pryidine; (3) the dye 1 : 1<1>-diethyl-b -naphthothioa  - methyl - pentacarbocyanine iodide by heating 2 - methyl - b  - naphthothiazole - ethyl iodide with b -ethoxy-b -methyl-acrolein-acetal in pyridine; (4) the dye 1 : 1<1>-diethyl-benzseleno-b -methyl-pentacarbocyanine iodide by heating 2-methyl-benzselenazole-ethyl iodide with b -ethoxy-b -methyl - acrolein-acetal in pyridine; (5) the dye 1 : 1<1>-diethyl benzthio-b : g -dimethyl-pentacarbocyanine iodide by heating 2 - methyl - benzthiazole-ethyl-iodide with b -ethoxy-a  : b -dimethyl-acrolein-acetal in pyridine; (6) the dye 1 : 1<1>-diethyl-benzthio-b -methylheptacarbocyanine-iodide by heating 2-methyl-benzthiazole ethyl-iodide with e -(b -naphthylimido) - a  - (b  - naphthylamino) - a -methyl-a  : g -pentadiene hydrochloride in alcohol with the addition of diethylamine; (7) the dye 1 : 1<1> - diethyl- 6 : 6<1>-bisdiethylamino-benzthio-8-methyl-heptacarbocyanine perchlorate by heating 5 - diethylamino - 2 - methyl - benzthiazoleethyl-iodide and e -phenylimido - a  - phenyl-amino - (g - methyl - a  : g  - pentadiene) - hydrobromide in alcohol with the addition of diethylamine and precipitating with sodium perchlorate; (8) the dye 1 : 1<1>-diethyl-b -naphthothio - d  - methyl - heptacarbocyanine - iodide by heating 2 - methyl - b  - naphthothiazole - ethyl-iodide with e -phenylimido-a -phenyl-amino-(g -methyl-a  : g -pentadiene) hydrobromide in alcohol with the addition of sodium ethylate; (9) the dye 1 : 1<1> - dimethyl - 4 : 4<1> - quino - 8-methyl-heptacarbocyanine perchlorate by heating lepidine-methyl-iodide with e -phenylimido-a  - phenylamino - (g -methyl a  - g  - pentadiene)-hydrobromide in alcohol and dimethylamine and adding sodium perchlorate; (10) the dye 1 : 1<1> - dimethyl - a  : a <1>-dimethyl - dibenzthiopenta-carbocyanine-iodide by heating 2-ethyl-benzthiazole-methyl-iodide with b -ethoxy-acrolein-acetal in pyridine.  a -(b -naphthylimido)-e -(b -naphthylamino) - a  - methyl - a  : g -pentadiene hydrochloride is prepared from b -naphthylamine, a -picoline and cyanous chloride and e -phenylimido-a -phenylamino-g -methyl-, a  : g -pentadiene-hydrobromide from aniline g -picoline and cyanous bromide.