GB664597A - Improvements in or relating to the hardening of dye-absorptive hydrophilic colloidallayers - Google Patents

Abstract

664,597. Hardening gelatine blank films. TECHNICOLOR MOTION PICTURE CORPORATION. Jan. 21, 1949 [April 3, 1948], No. 1751/49. Class 98 (ii). [Also in Group V] The dye-absorptive hydrophilic colloid layer of a blank film is hardened prior to dye transfer thereto by subjecting the layer to the action of an aqueous chromic salt solution containing 25-70 per cent of the green form of chromium and 75-30 per cent of the purple form of chromium and thereafter washing out unreacted chromic salts. Typically an aqueous chrome alum solution containing 52.5 grams per litre, of which 60-65 per cent is of the green form of chromium, is prepared either by mixing appropriate quantities of 100 per cent purple chromium alum, prepared by dissolving the alum in ice-cold water, and of 100 per cent green chromium alum, prepared by boiling chrome alum solution for half an hour, or by heating chrome alum solution to, say, 190‹ F. until sufficient of the green form is present, the final solution being adjusted to pH 3.5 by the addition of ammonia. The blank film is immersed in the hardening solution at 70‹ F. for about 1¢ minutes followed by washing for 1 minute. To avoid depletion of the green chromium in the solution adjacent the film the hardening solution is agitated, as by continuous movement of the film therethrough, and the overall concentration is maintained by periodic additions of the appropriate amounts of the green and purple chrome alum solutions, as determined by colorimetric tests on the solution. Specification 484,411 is referred to. The Specification as open to inspection under Sect. 9 states that a chrome alum solution containing 5.25 grams per litre may be used. This subject-matter does not appear in the Specification as accepted.