GB557802A - Improvements in methods relating to colour photography - Google Patents

Abstract

557,802. Colour photography. KODAK, Ltd. (Eastman Kodak Co., Vittum, P. W., and Wilder, L. S.). Oct. 21, 1941, No. 7151/43. Divided out of 557,750. [Class 98 (ii)] The formation of colour fog in a sensitive silver salt emulsion containing colour coupler prior to exposure and which is exposed and processed by a series of steps including colour development is reduced or prevented by performing the colour development step in the presence of an inhibitor of colour for consisting of an organic ring compound having at least one hydroxyl nuclear substituent which has been incorporated in the emulsion prior to the commencement of and is still present during colour development. In three-colour material comprising three emulsions in one or more layers adapted to record three out of the four spectral regions blue, green, red, and infra-red, the inhibitor may be incorporated in one, two, or all of the layers. Suitable compounds are hydroquinone, n- or iso-amyl hydroquinone, lauryl hydroquinone, n-heptyl hydroquinone, diamyl hydroquinone, dilauryl hydroquinone, di-n-heptyl hydroquinone, di-isooctyl hydroquinone α-tocopherol, ascorbic acid, and dodecyl catechol. A compound having a chain of at least 5 carbon atoms is preferably used, but a compound of lower molecular weight is preferably if it is to be uniformly distributed throughout the film. In emulsions containing a coupler incorporated in a water-insoluble binder dispersed as particles in the emulsion as in Specifications 524,154, 524,554, 524,555, 540,368 and 541,589, the compound may be added to the emulsion or else to the mixture of the water-insoluble binder and coupler before dispersion in the emulsion. In a modification, the compound may be introduced into the emulsion after coating and before processing, e.g. by bathing the sensitive material in an aqueous solution containing hydroquinone, potassium bromide, and sodium sulphite. The solution should be applied immediately prior to colour development with little or no washing therebetween. The compound may also be added to a processing bath which immediately precedes the colour development step. An opaque support, e.g. paper, may be used. The preparation of the compound is as described in Specification 557,750. Specifications 503,752 and 505,834 also are referred to.