GB376838A - Improvements in processes for the production of colour photographs - Google Patents

Abstract

376,838. Colour photography. MANNES, L. D., 111, East 81st Street, and GODOWSKY, L., 8, West 76th Street. both in New York, U.S.A. Jan. 16, 1931, No. 15226/32. Convention date, March 19. 1930. Divided on 376.795. [Class 98 (ii).] Colour photographs are produced by exposing two or more superimposed differently sensitized layers, developing and fixing the images, bleaching them and redeveloping them with developers containing different substances which are capable of combining in the presence of reduced silver with the reactive products of the developer to form coloured compounds. The bleaching may be accomplished by controlled diffusion of potassium ferricyanide, the top layer and each successive layer being bleached and redeveloped with a colourdeveloper independently. Alternatively the layers may be simultaneously bleached, the upper layer or layers then redeveloped by controlled diffusion of developer, and the undeveloped bleached lower layer then developed with a developer containing a colour former. After fixing and washing the film, the upper layer or layers are then rebleached for a similar sequence of controlled development and colour development of another layer. The silver in the picture can then be eliminated. Specific examples of colour-formers and developers a e given. An example is also given of a process in which a red and green sensitive emulsion are superimposed, the colour-sensitizer near the upper surface being removed by using an alcoholic solution of a yellow dye, giving a thin upper blue sensitive layer, for a particular reflection printing process.