GB755425A - Production of positive photographic images by transfer - Google Patents

Abstract

755,425. Photographic positive images by transfer. AGFA AKT.-GES. FUR PHOTOFABRIKATION. Jan. 20, 1954 [Jan. 22, 1953], No. 1719/54. Class 98 (2). In the silver-salt diffusion process in which the unreduced silver halide of an exposed and developed emulsion layer is transferred to, and reduced in, a reception layer which is in intimate contact with the emulsion layer during development, the emulsion layer is coated on a thin base as of paper, and such is temporarily attached to an auxiliary support for passage through the developing solution. Difficulties as by folding or distortion of the thin base in the developing solution, especially when several positives are taken from one emulsion layer, are thereby avoided, and the use of thin bases is advantageous in needing shorter exposure times in reflex printing. The auxiliary support may be of cellulose ester or ether, or polyvinyl chloride, polystyrene or polyamide and may approximate to the size of the emulsion layer but may be designed as an endless band to permit processing of several prints in one step. Temporary attachment may be effected by use of a roughened surface on the auxiliary support or by a colloid layer thereon, or by clamping or gripping means. As shown, Fig. 1, a container 1 with developing solution 2 has a lid 3 with openings 4, 6 for entrance of the negative and positive materials respectively and means 19 to guide these to and between two endless bands, 15 travelling in a V-path over rollers 8, 13, 12 and constituting the auxiliary support, and 16 looped over rollers 14, 11; of which the pair 13, 14 are pressure rollers for image transfer. Guideway opening 7 is provided for exit of the materials. Belt 16 and its rollers may be replaced by a single roller of circumference sufficient to press on belt 15 at the positions of rollers 13, 12. The apparatus of Fig. 2 allows simultaneous transfer of positive images to both sides of a reception layer and for this the latter is introduced through a further opening 5, to meet, similarly, two emulsion layers introduced at 4, 6 respectively for pressure and conveyance to exit 7. Specifications 387,876, 433,469, 614,155 and 654,630 are referred to.