Patent GB-550994-A (GB)
Title: Improvements in or relating to the toning and colouring of photographic records
IPC: G03C7/26
Filed: 1941-08-01
Abstract: 550,994. Photographic toning processes; colour photography. DU PONT FILM MANUFACTURING CORPORATION. Aug. 1, 1941, No. 9826. Convention date, Aug. 2, 1940. [Class 98 (ii)] A yellow-toned sulphide image is obtained by treating a silver sulphide image with an aqueous toning solution containing a water-soluble cyanide and a water-soluble salt of cadmium, arsenic, or antimony. The cyanide may be an amine, ammonium, substituted ammonium, or alkali metal cyanide, and the cadmium, arsenic or antimony salt a sulphate, phosphate, nitrate, borate, chloride, bromide, iodide, fluoride, acetate, propionate, lactate, borotungstate, or selenate. Cadmium sulphate, nitrate, fluoride, chloride, bromide, iodide, borotungstate, selenate, acetate, or lactate, arsenious chloride, and antimony nitrate are specific examples. Loading agents such as mono- and polyhydric alcohols, e.g. methyl, ethyl, n-propyl, iso-propyl, butyl, and amyl alcohols, glycerol, ethylene and propylene glycol, acetone, gelatine, gum arabic, sugar, sodium sulphate, and sodium chloride may be added to the toning solution. A silver image may be bleached with a bath containing copper chloride or bromide and an oxidizing agent such as chromic acid, notassium ferricyanide, or potassium ferricyanide in the presence of an alkali carbonate. The bleached image is converted into silver sulphide by treatment with a water-soluble sulphide or a water-soluble sulphur compound, capable of forming silver sulphide. e.g. hydrogen sulphide, alkali (sodium or potassium) sulphides, barium sulphide, ammonium sulphide, sodium thiomolvbdates, thiotungstates, and thiostannates. The silver image may be a positive, negative, or reversed image. The silver sulphide image contains the residual stain images formed during development and during fixing. The outer image is an exposed bi-pack or three layer material in which the three component images have been developed, fixed, and washed may be bleached and toned to a silver sulphide image while the other images are transformed into coloured images by colour development. The toning may precede or follow a colour development step. In three-layer material, the three layers may be all on one side of the support, or one layer may be on the opposite side. In the two-layer element of a bi-pack, the two layers may be on the same or opposite sides of a transparent support. The layers may be sensitized with cyanine, carbocyanine, pseudocyanine, neocyanine, cyazine, carbocyazine, or rhodanine dyes in the form of bases or salts. The material may have prefogged layers between the colour-component layers as in Specification 512, 563, Such material may be developed to silver, the residual image in the innermost layer colour developed blue-green, the residual outermost layer toned with sodium sulphide, and the middle layer rendered developable chemically with aqueous alkaline sodium arsenite, hydrogen peroxide, guanidine thiocyanate, guanyl thiourea, thiourea, allylthiourea, or imino amino methane sulphinic acid, or by exposure to X-rays, ultrasonic vibrations or heat rays (after hardening in for maldehyde solution). The silver images are removed by successive treatments with alkaline ferricyanide solution and hypo. In example 1-6, toning baths contain (1) cadmium sulphate and potassium cyanide; (2) cadmium nitrate and potassium cyanide ; (3) cadmium acetate and sodium cyanide ; (4) arsenious chloride (or nitrate) and ammonium cyanide ; (5) antimony nitrate and potassium cyanide ; and (6) cadmium acetate, potassium cyanide, and glycerol. In example 7, a silver image is bleached in a chromic acid-sodium chloride bath or an alkalineferricyanide bath, washed, treated in a bath containing sodium sulphide, ethyl alcohol, and glycerol, the silver images removed with Farmer's reducer, and the image toned in the bath of example 1. In example 8, multilayer positive nitrate support coated on one side with a gelatino-silver bromide emulsion (A) containing Tartrazine having a gelatine anti-abrasion overcoating, and on the other side with successive layers of panchromatic gelatino-silver-chloro-bromide emulsion, (B) plain gelatine, and gelatino-silverbromide emulsion, (C) a blue component negative is printed, using a sharp-cutting blue filter, on to emulsion C, a green component negative, using exposure light filtered to contain no blue-green rays, on to emulsion B, and a red component negative, using a sharp-cutting blue filter, on to emulsion A. The material is developed, fixed, bleached in a bath containing copper sulphate, sodium chloride, and sulphuric acid, dried, the two-layer side floated on a solution containing sodium sulphide, ethyl alcohol, and glycerol, washed the two-layer side floated on a magenta colour developer containing p-amino-N-diethylaniline hydrochloride, sodium sulphite, sodium carbonate, and p-nitrobenzyl cyanide (alcoholic solution), washed, and the single-coated side floated on a blue-green colour developer containing p-amino-N-diethylaniline hydrochloride, sodium sulphite, sodium carbonate, and 4-chloroo-phenylphenol. The silver is removed by treatment with alkaline ferricyanide solution followed by fixing, the silver-copper-sulphide complex image is converted into a cadmium-copper-sulphide image by treatment in a bath containing cadmium sulphate and potassium cyanide, and the film is washed and dried. In example 9, a support carries a gelatino-silver-bromide emulsion sensitized predominately in the orange-red region by naphthiocarbocyanine in the presence of soluble bromide, a pre-fogged emulsion material, a gelatino-silver-chlorobromide emulsion greensensitized with erythrosine or pinaflavol, a yellow gelatine filter layer containing Tartrazine, and a gelatino-silver-bromide emulsion. After exposure and development the innermost layer is re-exposed through the support with red or white light and developed in a blue-green colour developer, and the film washed and dried. A silver sulphide image is produced in the outermost layer by treatment with 90 per cent aqueous ethyl alcohol saturated with sodium sulphide, and the film is washed, and the middle layer developed, after being rendered developable chemically, in a magenta colour developer. The film is bleached in alkaline' potassium ferricyanide, washed, fixed, treated in a cadmium nitrate-potassium cyanide bath, and dried. In modifications (examples 10 and 11) the aqueous ethyl alcoholic sodium sulphide solution is replaced by aqueous ethyl alcoholic ammonium-sulphide solution or by aqueous methyl alcoholic barium sulphide solution. In example 12, the process is applied to the bipack of Specification 505,861. Specification 505,099 also is referred to. The Specification as open to inspection under Sect. 91 comprises also the production of a yellow-toned image by treating a silver sulphide, selenide, or telluride image with an aqueous toning solution containing a water-soluble cyanide and a water-soluble salt of a heavy metal, which heavy metal is one which forms a yellow sulphide, selenide, or telluride. This subject-matter does not appear in the Specification as accepted.