GB400951A - Sensitising silver halide emulsion layers - Google Patents

Abstract

Silver halide emulsions are sensitized by the addition of benzothiocarbocyanine, benzothiocyanine, benzoselenocyanine, benzothiopseudocyanine, benzoselenopseudocyanine, benzothioisocyanine or benzoselenoisocyanine dyes in which the benzene nucleus attached to the thiazole or selenazole ring contains a substituted or unsubstituted amino-group. Suitable substituents are methyl, ethyl, acetyl or propyl radicals. The dyes are added to the emulsion in the form of alkyl halides or alkyl sulphoalkylates. Suitable dyes for the process are (1) 1 : 1<1>-diethyl-5 : 5<1> - bisdiethylamino - benzothiocyanine iodide; (2) 1 : 1<1>-diethyl-2 : 2<1>-(5-benzoylamino - benzo - thio - quino)-cyanine iodide prepared by boiling 6-benzoylamino-2-methylbenz-thiazole-diethyl sulphate with 2-iodoquinoline ethyl iodide with the addition of alcoholic potash; (3) 1 : 1<1>-diethyl-5-dimethylamino-2-benzothio - 4<1> - quinocyanine iodide prepared by boiling 6-diethylamino-2-methylbenzthiazole ethyl iodide with quinoline ethyl iodide and alcoholic potash; (4) 1 : 1<1>-diethyl - 5 : 5<1>- bis - diethylaminobenzothiocarbocyanine iodide obtained by boiling 2-methyl-6-diethylamino-benzthiazole ethyl iodide with pyridine and triethylorthoformate; (5) 1 : 1<1>-diethyl - 6 - 6<1> - bisdiethylaminobenzothiocarbocyanine prepared as above, using 2-methyl-5-diethylaminobenzthiazole ethyl iodide; (6) 1 : 1<1>-diethyl - 5 - diethylamino - 6<1>-methoxybenzoseleno-pseudo cyanine iodide obtained by boiling 2-methyl-6-diethylamino-benzselenazole ethyliodide and 2-iodo - 6 - methoxy - quinoline with addition of sodium ethylate; and (7) 1 : 1<1>-dimethyl - 5 : 5<1> - diacetylamino - benzoselenocyanine iodide prepared by boiling 2-methyl-6-acetylamino-benzselenazole methyl iodide with acetic anhydride and amyl nitrite. The base 2-methyl-5-dimethylamino-benzthiazole is prepared by nitrating parabromo-dimethyl-aniline, heating the product with sodium sulphide, reducing the product with sodium sulphide in aqueous suspension and converting the resulting compound into 2-methyl-5-dimethylamino-benzthiazole by treatment with acetic anhydride. The base 6-benzoylamino-2-methyl-benzthiazole is formed by benzoylating 6-amino-2-methyl benzthiazole prepared as described in Specification 313,293, [Class 2 (iii), Dyes &c.]. The base 2-methyl - 6 - diethylaminobenzselenazole ethyl iodide is prepared by nitrating 2-methylbenzselenazole with nitric acid, reducing the product with stannous chloride or iron and acetic acid, heating the resulting product with ethyl iodide and alcohol in a sealed tube. The base 2 - methyl - 6 - acetylamino - benzselenazole methyl iodide is made by acetylating 2-methyl6-amino-benzselenazole with acetic anhydride. Specification 383,486 also is referred to.