Patent GB-523296-A (GB)
Title: Process and material for the production of colour photographs
IPC: G03C7/46
Filed: 1938-09-06
Abstract: 523,296. Colour photography. SCHINZEL, K., and SCHINZEL, L. Sept. 6, 1938, No. 25982. [Class 98 (ii)] Printing material for the production of subtractive colour photographs comprises a plurality of differentially coloured emulsions each containing as the light sensitive substance a salt of a dye derivative or of a generator of a dye formed with an organic base or acid which is directly converted to a dye image by the action of light. Three emulsions may be used in the form of three superimposed layers, of a mixture of three sets of grains, or of a homogeneous blue-sensitive layer and a layer containing two sets of grains or containing grains dispersed in a different emulsion. A yellow filter layer may be provided between the blue sensitive layer and the other layers. Alternatively a yellow salt of the dye-derivative in the blue-sensitive emulsion is employed, or the latter may be dyed yellow with a decolorable dye. An orange or red filter layer may be arranged between the two other emulsion layers. An upper homogeneous blue-sensitive layer and a lower two-grain layer containing dyegenerators for purple and blue-green may be provided. The order of the emulsions may be reversed and the film exposed through the back. Collodion grains containing one dye-derivative may be emulsified in solutions of cellulose acetate, cellulose ether, polyviny alcohol or gelatin containing the other dye-derivative. The insoluble dye-derivatives may be formed by double decomposition in starch or lycopodium grains, or may be produced in finely ground cellulose or powdered wool and formed into paper. The derivatives may also be formed successively in regenerated cellulose film. Erythrosine, isocyanine, pinacyanol, and fulgide are used as colour sensitizers. Salts of leuco bases with dyes such as pyronine, night-blue, methylene blue, or auramine, or with dicinchonine, quinine or diphenylguanidine may be employed. Oxidising agents may be added. Insoluble salts of colourless leuco esters with dyes coloured complementarily to the light to be absorbed are preferably used, for example a salt of a leuco ester of a yellow vat dye with auramine or thioflavine T, a salt of a purple vat dye with pyronine, fuchsine, or rhodamine, and a salt of a blue-green vat dye with night-blue, methylene blue, or a blue cyanine, isocyanine, or pinacyanol. The leuco esters may be coloured in the complementary colour, for example the salt of indigosol golden yellow IGK with diphenylguanidine or auramine, the salt of chlorisodibenzathrone with pyronine or rhodamine, and the salt of indigosol green AB with methylene blue or night-blue. The unexposed parts may be decomposed with sodium hydroxide, ammonia, or sodium carbonate, and washed out. Basic dyes used as precipitants may be washed out with acidified water. Dye derivatives of colour complementary to the light absorbed and converted into vat dyes of the same colour as the light may be employed. The original in this case is processed by colour development so that the top blue component is coloured blue-green or blue, the middle green component yellow or green, and the bottom red component bluish-red or red. Stable diazo compounds of amino dyes in the form of insoluble salts with high molecular sulphonic acids or complex salts may be used. The diazo derivatives of dyes containing one or more amino groups may be used. The diazo compounds in the unexposed areas may be liberated by alkali or acid and used for coupling. The diazo compound in the exposed parts may be removed by conversion of the diazo group to hydroxyl or by coupling with phonol-1-diazo-#-naphthol-4- sulphonic chloride or carboxylic acid chloride may be reacted with thioindigo white. The vat dye produced by exposure may be removed by alkaline reduction and vat dye regenerated from the residual insoluble leuco derivative by general exposure or by treatment with an oxidising agent. Derivatives containing an oxidising group may be employed. Thioindigosols may be precipitated with complex compounds formed from thiourea and silver halides. The precipitating bases may first be absorbed on finely ground silica gel. A light filter action may be obtained by producing a superficial precipitate of night-blue or methylene blue on the yellow. Thioflavine T salt of indigozol O, and the precipitate may be rendered insoluble by treatment with phosphotungstates or higher organic sulphonic acids. This procedure is particularly applicable to grains produced by pulverization. In printing ultraviolet and violet light is removed from the printing light, or the latter is composed of three narrow bands. Printing from three black-and-white or colour component negatives or positives may be effected. A black silver key image may be provided in the printed image. Specifications 417,588 and 503,826 are referred to.