GB666107A - Improvements in colour photography - Google Patents

Abstract

666,107. Colour photography. KODAK, Ltd. Oct. 18, 1949 [Oct. 21, 1948], No. 26670/49. Drawings to Specification. Class 98 (ii). An exposed emulsion layer containing differently sensitized silver bromide or bromoiodide and silver chloride or chloro-bromide grains is developed with a colour developer containing an antifoggant consisting of 6- nitro - benzimidazole, 6 - nitro - benzimidazole nitrate, 5-nitroindazole or benztriazole, treated, as with 10 per cent sodium sulphite, to remove undeveloped silver chloride, and then treated with a different colour developer not containing the antifoggant to develop the exposed silver bromide grains. The antifoggant has the effect of sufficiently increasing the known difference in rate of development between silver chloride and silver bromide to permit this individual development of the silver chloride. The layer may comprise not specially coloursensitized silver bromide or bromoiodide grains and green or red-sensitized silver chloride grains and may be used in conjunction with another silver bromide or silver chloride layer on the same, or opposite, side of a support; either or both layers may contain colour couplers, or the latter may be used in solution. Example 1 describes a two-colour mixed grain process using a layer containing non-colour sensitized silver bromide, and silver chloride green sensitized as with 5-(2-ethyl-l-benzoxazolylidene) - ethylidene - 3 - n - primaryheptyl - 1 - phenyl - 2 - thiohydantoin on a support such as cellulose ester, synthetic resin or paper; which is exposed through a filter having a blue portion and a green portion; treated in 1 per cent 6-nitrobenzimidazole nitrate for one minute; developed in a specified p-diethylaminoaniline developer containing 1- phenyl - 3 - (b - - nitrobenzoylamino) - 5 - pyrazolone, #-benzoylacetanilide and more of the 6-nitrobenzimidazole nitrate to produce by the mixture of couplers, red colour in the exposed silver chloride grains; treated in 10 per cent sodium sulphite to remove undeveloped silver chloride without affecting the silver bromide; developed in a 2-amino-5-diethylaminotoluene developer containing 2 ; 4-dichloro-1-naphthol to provide cyan colour in the exposed silver grains; and, finally given conventional bleaching and fixing treatments. Examples 2-5 describe three colour adaptations using a mixed grain layer of the type of that of example 1 in conjunction with a further silver halide layer; , example 2 having this further layer on the oppo- . site side of the support and protected from the first developing and fixing steps by an acid soluble polyvinyl pyridine resist; examples 3 and 4 using superposed emulsion layers, both containing colour formers in conjunction with a further colour former in the second developer, and example 5 constituting a false colour process. Specifications 524,154, 524,554, 524,555, 541,589 and 2505/39 as open to inspection are referred to. The Specification as open to inspection under Sect. 91 comprises also the use of 2-amino-omethylbenztriazole as antifoggant. This subject-matter does not appear in the Specification as accepted.