Patent GB-661211-A (GB)
Title: Improvements in or relating to colour photography
Inventor: HARRISON GEOFFREY BOND
IPC: G03C7/18
Filed: 1949-02-09
Abstract: 661,211. Colour photography. ILFORD, Ltd. Feb. 7, 1950 [Feb. 9, 1949], No. 3601/49. Class 98 (ii). A multilayer material which includes a layer destined to record a masking image for colour correction comprises the following layers: (a) blue-sensitive silver bromide emulsion containing a colour-former; (b) removable blueabsorbing filter; (c) green-sensitized silver bromide emulsion containing a colour-former; (d) red-sensitized silver bromide emulsion containing a colour-former; (e) removable blueabsorbing. filter; (f) silver bromide emulsion sensitized to green or red or both, constituting the masking layer; (g) transparent colourless support, the colour-formers lying preferably in the usual yellow, magenta and cyan sequence; or with layers (c) and (d) in reverse order; while, if desired, layer (f) or layers (e) and (f) may be on the other side of the support. The filter layers may incorporate dischargeable dyestuffs or colloidal silver, and in a modification layer (f) may include a colour former for masking the colour images of layers (c) or (d) or both. The element may be exposed; and then processed to a negative colour record with positive masks in dye or silver, or to a positive colour record with negative masks, by a number of procedures which include (1) non-colour-forming development to produce negative silver records in layers (a), (c), (d) and (f), exposure of layer (f) by blue light, development in a colour developer containing a colour-former to produce a colour masking image suitable for the colour images to be produced in layers (c) or (d) or both, fixation, bleaching, re-exposure, colour development and removal of silver and residual silver halide by Farmer's reducer; (3) initial colour development, which development may be brought to completion if desired in a vigorous black and white developer, treatment with cupric chloride to convert the developed silver to silver chloride, removal of the latter with sodium sulphite which leaves the silver bromide of the original layers unaffected, re-exposure of layer (f) by blue light, non-colour-forming development to produce a positive silver mask therein and fixation in hypo. Procedure (4) uses reversal technique and for this the element must be one in which filter layer (b) includes a readily removable dyestuff such as tartrazine, while filter layer (e) resists developing, fixing and bleaching treatments and may comprise a complex of auramine base and bexadecyl sodium sulphate; after exposure the element is treated in a non-colour-forming developer to produce negative silver records in layers (a), (c), (d) and (f) and decolorize layer (b), re-exposed by blue light incident on layer (a), colour developed, fixed, bleached as with potassiumferricyanide and -bromide, re-exposed with blue light incident on layer (f), developed to produce a negative masking record in either silver or dyestuff therein, fixed and, finally, treated as with dodecyl pyridinium bromide to remove the filter material in layer (e). Specifications 475,784, 475,786 and 561,674 are referred to.