Process for the production of coloured photographic pictures
Реферат: 397,884. Colour photography. DRKOPP-WERKE AKT.-GES., Bielefeld, Germany. Feb. 1, 1932, No. 2993. Convention date, Feb. 9, 1931. [Class 98 (ii).] In the production of colour photographs by printing from two complementary negatives on to opposite sides of a film coated on both sides, the negatives are obtained by single exposure of a bipack and are accurately focused and brought into register on a ground glass screen and copied by projection on the doublecoated film. Weak diapositives are made which are weakly coloured in complementary colours and provided with a reflecting support for viewing. To produce three-colour pictures, the coloured diapositive is bathed with a chromate solution and exposed from one side, the unhardened portions on the other side being then coloured with an acid pigment. The negatives are produced on a bipack comprising a front plate mainly sensitive to green and slightly sensitive to blue and a rear, redsensitive plate which may be partly sensitive to green, an orange filter being placed between the plates or coated on the rear of the front plate. A yellow filter dye is added to the front emulsion, or exposure is made through a yellow filter. The two negatives are each mounted in a projection apparatus and focused and registered on opposite sides of a ground glass screen, registration being facilitated by projection through red and green filters. When registered, the screen is replaced by a doublecoated film having an intermediate screening layer which is removed in the developer. The exposed film is developed in a hardening developer, e.g. pyrocatechin without sulphite, mordanted in a permanganate bath, and coloured by suitable basic pigments, e.g. pyronin 6 for the red side and thionin blue for the blue. After clearing in a bath of potassium metabisulphite, the picture is washed for a few minutes in a bath of ammonium chromate, dried, and exposed to strong light from the red side ; a yellow acid dye is then washed into the unhardened portions of the blue side. The finished film is mounted on white paper or is coated on the rear side with a white pigment which may be lightly coloured with blue or yellow to obtain different tone effects.
Process for the production of colour photographic pictures
Номер патента: GB774534A. Автор: . Владелец: Ciba AG. Дата публикации: 1957-05-08.