Patent GB-503815-A (GB)
Title: Improvements in the production of natural colour photographs by colour development
IPC: G03C7/30
Filed: 1937-07-07
Abstract: 503,815. Colour photography. KODAK, Ltd. July 7, 1937, No. 2601 /39. Convention date, July 7, 1936. Divided out of 503,752. [Class 98 (ii)] A three-colour photographic element having three differentially colour-sensitized silver halide emulsions inseparably coated on a single support and having in each emulsion a colour former not more soluble in water or in a solution of sodium carbonate in water than the most soluble of tri-alpha-naphthol-triazine, alpha-naphthol- 2-carboxylic acid-alpha (or #)-naphthylamide, alphanaphthol-4-benzoylketone or the hydrazone of the last-named is, after exposure, subjected to colour processing including treatment with an alkaline coupling developer and after processing is used for printing on to another three-colour element of the same kind and processed in the same manner as the first element. The first or second element may be processed to a negative by primary colour development or by colour development after ordinary development, fixing and bleaching, or the second element may be processed by reversal to give a duplicate negative. Development with a neutral developer such as ferrous oxalate or hydroquinoneacetone sulphite and treatment of the residual silver-halide with a fogging agent such as thiosinamine are referred to. The colour formers may have different coupling speeds, one coupling in the presence of borax, another only in presence of sodium carbonate. Colour developers of different coupling speeds may be used. The colour formers may be dispersed in gelatine and then added to the emulsion, or may be deposited on or adsorbed by the silver halide grains. The colour formers may be formed within the emulsion, preferably after ripening, or may be precipitated in emulsions of low gelatine content in centrifuged emulsion or in silver bromide separated from an emulsion after dispersion in water, or glycerine or other water-miscible liquid and the resulting material dispersed in gelatine, washed and sensitized. The colour formers may be added in alcoholic alkaline solution to an emulsion of low gelatine content and precipitated with acid, and the gelatine content brought to the correct value. A yellow filter consisting of a dyed layer of water or sodium carbonate-soluble colloid, such as dextrine, gum arabic, or stearic-acid, may be arranged above the blue-sensitive emulsion. A colloidal silver antihalation layer may be arranged on either side of the support. The element may have a top blue-violet sensitive layer, a middle yellow-green sensitive layer, and a bottom red or infra-red sensitive layer, or a top blue-violet sensitive layer, a middle red-orange or infra-red sensitive layer, and a bottom yellow-green sensitive layer, or a top red-sensitive layer, a middle yellow-green sensitive layer, and a bottom blue-sensitive layer. Strongly swelling gelatine is used for emulsion and filter layers. A yellow filter may be arranged between the blue-sensitive layer and the middle layer, and a green-red-orange, or yellow filter or a colourless gelatine layer may be arranged between the middle and layers. The filter dyes may be added to the top and middle layers. The emulsion may be coated in reverse order and exposed through the support. The red or the yellow-green sensitized emulsion may be on the opposite side of the support. The bottom layer may be a highly sensitized collodion emulsion or a hardened gelatine emulsion in which part of the gelatine is replaced by agar-agar, polyvinyl alcohol, or other lessswelling colloids. The use of peptized and centrifuged emulsions is referred to. Alternatively the element may comprise a top bluesensitive silver bromide or chloride emulsion and a lower mixed emulsion layer, some particles of which are sensitized to red and orange and others to yellow and green. A yellow filter may be arranged between the emulsions. Yellow-green and red-sensitized emulsions may be mixed, or the separate emulsions may be pulverized or emulsified in an immiscible liquid such as tetrahydronaphthalene or xylene and re-emulsified after weak tanning in solutions of gelatine, collodion or other developer-permeable colloid. One or both may be collodion emulsions. A pulverized emulsion may be re-emulsified in the other emulsion. After re-emulsification in collodion, the mixed emulsion layer is over-coated with a layer of gelatine, dextrine, gum arabic, or other water soluble colloid. Collodion emulsion particles may be re-emulsified in gelatine emulsion. The mixed emulsion layer may be on top and the element exposed from the rear. One emulsion may be a yellowgreen sensitized silver chloride gelatine or collodion emulsion, and the two emulsions merely mixed. The blue-sensitive emulsion may also be silver chloride, and the layers may be on opposite sides of the support and may be collodion emulsions over-coated with layers of gelatine, dextrine, gum arabic, or other water-soluble colloid, the rear layer serving also as an antihalation layer. The support may be very thin for use with a continuous-feed kinematograph camera. Alcohol or salts such as sodium carbonate or sulphate may be added to the processing baths to minimize swelling. A three-layer plate in which the bottom layer is a collodion emulsion is referred to. The support may comprise thin films of cellulose acetate, regenerated cellulose, or synthetic colloids lacquered on both sides. Thin films emulsion-coated on both sides may be temporarily mounted on water-permeable paper or aluminium foil. Emulsion-coated regenerated cellulose or transparent paper may be glued on stronger paper. The elements may carry a sound track. An element having a single layer comprising three sets of silver halide emulsion grains sensitized respectively to green, orange, and infra red may be used for printing. Specifications 376,746,376,794,376,795,440,032, 440,089, 447,092, 475,784, 475,786, 499,185, 500,826 (as open to inspection under Sect. 91), 603,752, 503,816, 503,817, 503,818, 503,819, 503,820, 503,823, 503,824, 503,825, 503,826, 503,827, 503,940, and 503,941 are referred to.