Patent GB-400401-A (GB)
Title: Manufacture of sensitised silver halide emulsions and of dyes therefor
IPC: G03C1/16
Filed: 1932-09-19
Abstract: Photographic silver halide emulsions are sensitized by a thiocyanine, thiopseudocyanine or thioisocyanine dye derived from a thiazole compound having fused on to the thiazole nucleus a system of three or four condensed rings.  Particular mention is made of anthracene, phenanthrene, acenaphthene, fluorene, chrysene, carbazole and diphenyleneoxide as ring systems fused on the thiazole nucleus.  Such thiocyanine dyes are prepared by condensing a quaternary salt of a 2-methylthiazole derived from the appropriate polynuclear compound having three or four condensed rings in the presence of acetic anhydride and amyl nitrite.  The thiopseudocyanine dyes are prepared by condensing such quaternary ammonium salt with a 2-iodoquinoline quaternary salt.  The thioisocyanine dyes are prepared by condensing such quaternary ammonium salt with a quinoline quaternary salt.  The dyes sensitize to wave lengths of about 500-620 m m  and are added in amounts of 10-40 milligrams per kilo emulsion ready for casting; they may be incorporated in the form of their alcoholic solutions in the emulsion, or the cast, but not dried emulsion may be coated with such alcoholic solution, or the finished photographic material may be bathed in such solution.  In examples: (1) 2-methyla -(N) anthrathiazole diethylsulphate is condensed with 2-iodoquinoline ethiodide and potassium iodide added to precipitate 1.1<1>-diethyl-2-2<1>-(a -anthra)-thiopseudocyanine iodide; condensing the corresponding dimethylsulphate salt with quinoline ethylbromide gives 1-methyl-1<1>-ethyl-2-4<1>-(a -anthra)-thioisocyanine bromide; condensing the corresponding methyl chloride salt in acetic anhydride by means of amyl nitrate yields 1-1<1>-dimethyl-a -anthrathiocyanine chloride; (2) a 2-methylacenaphthenethiazole diethylsulphate is condensed with 2-iodoquinoline ethiodide to give 1 - 1<1> - diethyl - 2 - 2<1> - (acenaphthene) - thio pseudocyanine iodide on adding potassium iodide; condensing this thiazole derivative with 6-methylquinoline ethiodide and adding potassium iodide yields 1-1<1>-diethyl-2-4<1>-(acenaphthene-6<1>-methyl) -thioisocyanine iodide; (3) a 2-methylcarbazolethiazolediethylsulphate is condensed with 2-iodo-6-methyl-quinoline ethiodide to give 1-1<1>-diethyl-2-2<1>-(carbazole-6<1>-methyl) -thiopseudocyanine iodide on adding potassium iodide; condensing this thiazole derivative with 6-methoxyquinoline ethiodide gives 1-1<1>-diethyl-2-4<1>-(carbazole-6<1>-methoxy) -thioisocyanine iodide; (4) a 2-methyldiphenyleneoxide-thiazole-diethylsulphate is condensed with 2-iodo-6-methoxyquinoline ethiodide and 1-1<1>-diethyl-2-2-(diphenyleneoxide-6<1>-methoxy) -thiopseudocyanine iodide precipitated out on adding potassium iodide.  2-Methylthiazole derivatives of polynuclear compounds having three or four condensed rings are prepared from the amino derivatives of these compounds according to known methods.  Thus 2-methylanthrathiazoles are prepared from a - or b -anthramines by acetylating, converting the product to the thioaceto compound and oxidizing this with potassium ferricyanide (cf. Specification 396,217).  The bases on treatment with alkylhalide, dialkylsulphate or ethyltoluenesulphonate yield quaternary ammonium compounds.  The Specification as open to inspection under Sect. 91 relates to the manufacture and use of thiocyanine, thiopseudocyanine or thioisocyanine dyes derived from higher polynuclear cyclic compounds, and claims the manufacture of such thiocyanine dyes by condensing the quaternary ammonium salt of the appropriate 2-methylthiazole derivative according to a known method. Reference is made to the presence of substituents in the anthracene, phenanthrene, &c., ring systems.  This subject-matter does not appear in the Specification as accepted.