Patent GB-545443-A (GB)
Title: Improvements in or relating to colour photographic processes
IPC: G03C7/30
Filed: 1940-10-16
Abstract: 545,443. Photographic colour development. DU PONT FILM MANUFACTURING CORPORATION. Oct. 16, 1940, No. 15342. Convention date, Oct. 16, 1939. [Class 98 (ii)] Coloured photographic images are produced by developing an exposed silver halide emulsion with an aqueous solution of a primary aromatic hydrazine containing a solubilizing agent, which is a surface-active polar compound which contains an open-chain hydrocarbon radical of at least 8 carbon atoms, in the presence of a coupling component which couples with oxidation products of the hydrazine to form an azo dye image. The hydrazine should precipitate silver from an ammoniacal solution containing approximately 0.1 per cent of silver nitrate within 30 seconds at 20 C. By using a di-functional hydrazine or a coupling-component containing an azo group or both, dis-, tris-, and tetrakis-azo dye images may be produced. The process may be applied to the development of latent images and of rehalogenized and reversed silver salt images. Residual silver salt images remaining after removal of the firstdeveloped silver may be reduced to silver and reoxidized to silver salts reducible by a primary aromatic hydrazine. The preferred hydrazines are free from negative groups such as sulphonic acid, sulphonate, carboxylic acid, or carboxylate groups. Examples specified are phenyl-, tolyl-, nitrophenyl-, bromophenyl-, chlorophenyl-, chloronaphthyl-, bromonaphthyl-, p-diphenyl-, α naphthyl-, and naphthyl-hydrazines, and p:p<SP>1</SP>- diphenyldihydrazines. Weakly acid to moderately basic developing solutions may be used, alkaline solutions being preferred. Acetic acid; alkaline carbonates, phosphates, acetates, phthalates, citrates, and borates ; alkali hydroxides ; mild oxidizing agents such as hydrogen peroxide, alkali metal peroxides, perborates, percarbonates, persulphates, hypochlorites, and alkali metal salts of per-organic acids, e.g. per-acetic and per-propionic acid ; or ammonia may be added. The coupling component may be in the developer or in the emulsion, including the emulsion layers of threelayer, bi-pack, and tri-pack colour photographic material. Stripping material may be used, the support being of paper, cellulose ester or ether, or resin. The adhesive layers may be softened or dissolved in water, alkaline baths such as developer baths, or acid baths and reversed baths. The support may be coated with a water-soluble glue or dextrine adhesive layer, followed by a thin collodion layer and the emulsion layer. Colour component negatives may be printed on to stripping paper material, and the print fixed, bleached, washed, and redeveloped in a hydrazine developer containing a coupling component. In example 1, a colour developer for the reversal process comprises phenylhydrazine, sodium oleate, sodium carbonate, and sodium #-naphtholate. Numerous other combinations of hydrazines and coupling components are given. In example 2, a colour developer comprises sodium oleate, p-nitrophenylhydrazine hydrochloride, sodium acetate, acetic acid, and 1-dimethylamino-5-naphthol. Hydrazino-diphenyl may also be used as the developing agent. In example 3, an emulsion containing silver halide and stearoyl-J-acid is coated on a cellulose acetate base, exposed, developed in a non-colour-forming developer, re-exposed, and processed in a colour-forming developer containing phenylhydrazine, sodium oleate, and sodium carbonate. The film is washed, and, after bleaching the silver, fixed. Other combinations of hydrazines and coupling components are given. In reversal, the first developed silver may be removed, and the remaining silver salts reduced and then re-oxidized to silver salts more readily reducible by hydrazines. Positive images produced by printing from negatives may be similarly treated. Specifications 458,400, 465,823, 479,838, 483,000, 489,093, 489,161, 489,274, 491,958, 491,959, 537,232 and 545,444 are referred to.