Patent GB-665657-A (GB)
Title: Improvements in or relating to colour photography
IPC: G03C7/18
Filed: 1949-04-13
Abstract: 665,657. Colour photography. DU PONT DE NEMOURS & CO., E. 1. April 13, 1949 [April 21, 1948], No. 10064/49. Drawings to Specification. Class 98 (ii). An integral colour-correcting mask is provided in an exposed element bearing a colloidsilver halide emulsion layer containing a colour former by colour-developing with a primary aromatic amino developing agent and coupling the colour former remaining in the layer with a diazo compound to form an azo dye which is complementary in colour to light undesirably absorbed by the dye image and then removing silver and silver salts. The process may be applied to an element with the " normal " arrangement of blue, green and red sensitive layers which are developed to yellow, magenta and cyan respectively to produce yellow, and then orange, orange-red or red masks in the magenta and cyan layers; or to an element as of Specification 644,575 with magenta in the outermost layer; and particularly to production of masked colour duplicate negatives from which multiple copies of positives are to be printed. Preferred diazo compounds for production of orange and yellow masks from conventional colour formers are those derived from aromatic amines with substituents such as -COOH, -S0 3 H, -N0 2 - halogen, -CN and CF 3; specific diazo compounds being those derived from metanilic acid, sulphanilic acid, anthranilic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-chloroaniline, p-chloroaniline, cyanoaniline, m-aminobenzotrifluoride, naphthionic acid, m-xylidine, 2 - naphthylamine - 6,8 - disulphonic acid, 4 - chloro-2-a.minotoluene. Compounds such as diazoiminos, nitrosamines and anti-diazotates, from which diazo compounds can be generated, may be used. The outermost layer of a multi: layer film may be treated with a diazo salt solution of controlled penetration characteristics to produce a colourless or nearly colourless reaction product from residual yellow colour former therein, and subsequently different diazonium compounds may be caused to react on a lower layer or layers; for this procedure diazotized meta-chloroaniline, meta-nitro-paraanisidine, ortho - aminoazotoluene, 1 - amino - anthraquinone, 5 - nitro - 2 - aminoanisole, meta - nitro - para - toluidine, 4 - chloro - 2 - nitro-aniline, 4-chloro-2-aminoanisole, 2,5-dichloroaniline, 4-nitro-2-aminoanisole or tetrazotized o-dianisidine may be used for the lower layers. Examples 1-3 describe production of the masks in single emulsion layers containing colour formers as of Specifications 627,125, 627,353, 631,269 and 661,477 by use of diazotized sulphanilic acid or diazotized p-aminobenzoic acid solutions. Example (4) provides a list of colours of the masks made by the various diazotized amines used for the lower layers of a multilayer film, as indicated above. Examples (5) and (6) describe production of mask images by means of the diazoamino derivative of aniline. Example (7) describes production of complementary orange and yellow masks by use of diazotized sulphanilic acid after colour development in a film having, in order on a support, emulsion layers for colour development of a cyan image sensitized for red light, for a yellow image sensitized for green light, and for a magenta image containing tartrazine. Examples (8) and (9) specify the diazo compounds of naphthionic acid, m-fluoroaniline, m-toluidine, m-amino benzoic acid, metanilic acid, m-amino-benzotrifluoride, pamino-benzoic acid, 4-chloro-2-amino-toluene, p-chloro-aniline, p-chloro-aniline, 2-naphthylamine-6,8-disulphonic acid and unsymmetrical m-xylidine for production of the masks, stating that these produce orange or orange-red, yellow, and colourless or very pale yellow masks in the cyan, magenta and yellow layers, respectively. Specifications 535,341, 598,477, 599,377.602,881 and 617,247 also are referred to. The Specification as open to inspection under Sect. 91 comprises also production of masks by coupling residual colour former with 1,4- naphthalenediamine - 7 - sulphonic acid, and hydrazine and its derivatives such as N-acyl-N- hydrazines or sulphon-hydrazides. This subject-matter does not appear in the Specification as accepted.