Patent GB-500795-A (GB)
Title: Improvements in colour photographic elements
IPC: G03C1/825
Filed: 1937-05-10
Abstract: 500,795. Colour photography. KODAK, Ltd. May 10, 1937, No. 34982 /38. Convention date, May 9, 1936. Divided out of 500,826. [Class 98 (ii)] Material having three differentially colour sensitized silver halide emulsions on a single support has in an intermediate layer or intermediate layers between two emulsion layers a filter colouring matter precipitated in situ to render it resistant to diffusion. The material may comprise three layers on the single support or may comprise two layers, one a blue-sensitive emulsion layer and the other a mixed emulsion layer containing two emulsions, one sensitized to rod and the other to green. The three-layer material has a top blue-violet sensitive layer, a middle yellow and green sensitive layer, and a bottom red or infra-red sensitive layer, or a top blue-violet sensitive layer, a middle red and orange or infra-red sensitive layer, and a bottom yellow and green sensitive layer, or a top red sensitive layer, a middle yellow-green sensitive layer, and a bottom blue sensitive layer. 4 : 4<1>-Dichloro-2 : 2<1> : 8-triethylthiacarbocyanine chloride very strongly sensitizes to the extreme orange red and the red but not to the green and the yellow. A yellow filter may be arranged between the blue-sensitive and the middle layer, or in the blue-sensitive layer itself, or a green or red-orange filter may be arranged between the middle and bottom layers. Strongly swelling gelatine is used for filter layers. The middle layer may be surrounded by colourless or coloured ultra-violet filters. Basic filter dyes can be precipitated by high molecular weight sulphonic acids, such as diazo light yellow 2G, di-(p-aminobenzoyl)-alpha-naphthylamine sulphonic acid and anthraquinone sulphonic acid or complex inorganic acids such as phosphotungsfic, silicotungstic acid, phosphomolybdio acid and their salts or their reduction products. Material containing a yellow filter not destroyed by developing agents or mild oxidizing agents in the upper layer or between the upper and middle layers is developed to silver, the silver removed, the top and bottom layers successively, selectively exposed and colour developed, the newly reduced silver removed, and the middle layer exposed and colour developed. The residual silver halide may first be converted to finely divided silver chloride, which is then processed by reversal. If the bottom layer is redsensitive, it is exposed to red light and developed blue-green, the top layer exposed to blue light and developed yellow and the silver therein removed, and the middle layer is exposed to yellow light and developed purple. Specifications 376,746, 500,719, 500,793, 601,000, 501,001, 501,002; and 501,003 are referred to. The Specification as open to inspection under Seet. 91, comprises also the addition of a redorange or green filter dye to the middle layer. The material may be dyed yellow or with an ultra-violet absorbing substance throughout. A colourless gelatine layer may be arranged between the layer. The remaining layers of material having a yellow filter layer or a yellow-dyed blue-sensitive emulsion may be dyed with solutions of yellow, red, or orange dyes, or ultra-violet absorbing substances after development. The dyes may be changed in colour by the action of acids or bases. This subject-matter. does not appear in the Specification as accepted.