Patent GB-631184-A (GB)
Title: Improvements in the processing of photographic materials
IPC: G03C5/39
Filed: 1946-10-01
Abstract: 631,184. Processing photographic silver halide emulsion layers. KODAK, Ltd. (Eastman Kodak Co., Brice, W. L., Russell, H. D., and Yackel, E. C.). Oct. 1, 1946, No. 29244. [Class 98 (ii)] An exposed hardened silver halide emulsion layer is rapidly processed by developing to form a silver image and stabilizing by treatment with a solution of a compound which does not react with metallic silver and which forms a light-coloured or transparent lightinert silver compound by reaction with undeveloped silver halide only until such silver halide is substantially converted to the lightinert compound, and drying without further treatment. If the emulsion is carried by a 'paper or other porous support, the developer may be applied with a sponge, rubber roller, or other applicator so that the support is not soaked with solution. Excess developer may be removed by a squeegee, and the stabilizing solution applied. The stabilizing compound may be an organic compound containing doublebonded sulphur or an -SH linkage or a compound containing a quaternary N atom, the compounds being generally used in lower concentration than in normal fixing procedure. Compounds specified are potassium and ammonium thiocyanates ; sodium, potassium and ammonium thiosulphates ; thiourea ; ethylene and propylene thioureas ; thioglycollic acid ; α-picolinium-#-phenylethobromide; thiobarbituric acid ; ammonium dithiocarbamate ; 2 - mercapto - 4 - methyl - 5 - nitrothiazole ; 2 - mercapto - 4 - methylthiazole ; dithiobiurea ; 4 - aminomethyl - 2 - mercaptoiminazole ; 5 - amino - 2 - mercapto - 1 : 3 : 4- thiodiazole ; 2 - mercapto - 5 - aminobenziminazole ; 6 - amino - 2 - thio - 4 - hydroxypyrimidine ; dithio - oxamide ; thiotrimethylacetamide; cysteine hydrochloride ; thioacetamide ; thiopropionamide ; and thioglycollic hydrazide. The thiosulphates and thioureas are used in acid solution, thioglycollic acid in alkaline solution, and thiocyanates in acid or alkaline solution. The time of treatment varies, but may be about 30 seconds. A compound of a metal below silver and above osmium in the electromotive series, e.g. palladium chloride, gold chloride, iridium sesquichloride, chloroplatinic acid, or a rhodium compound, may be incorporated in the emulsion layer or the stabilizing bath. A hydroxysubstituted aliphatic amine may be incorporated in the stabilizing bath to prevent crystallization, or the amine thiosulphate may be used wholly or in part as the stabilizing agent. Suitable amines are ethanolamine, diethanolamine, triethanolamine, #-diethylaminoethyl alcohol, trimethylolaminomethane, 2 - amino - 2 - methyl - 1 - propanol and 2- amino - 2 - methyl - 1 : 3 - propanediol. Stabilizing compounds such as the mercaptopyridines and mercaptopyrimidines, e.g. 4-amino-6-hydroxy - 2 - mercaptopyrimidine, 6 - amino - 4- hydroxy - 2 - mercaptopyrimidine, and 4- amino - 6 - hydroxy - 2 - mercaptopyridine, may be incorporated in the developing bath. The emulsion, if not already hardened is hardened before stabilizing and before or after development, e.g. with a formaldehyde hardening bath. Examples illustrate the treatment of developed plates, films, and papers with stabilizing solutions, stabilizing solutions containing salts of gold, iridium, palladium, and platinum, the development and stabilizing of an emulsion already containing gold chloride, and a combined developing stabilizing solution including metol, hydroquinone, and 6-amino-4- hydroxy-2-mercaptopyrimidine. The stabilization of a print-out image by treatment with aqueous propylene thiourea containing acetic acid is referred to.