GB602158A - Improvements in sensitive photographic materials - Google Patents

Abstract

602,158. Photographic emulsions. KODAK, Ltd. (Eastman Kodak Co., Trivelli, A.P.H., and Smith, W. F.). June 14, 1946, No. 17915. [Class 98 (ii)] A sensitive silver halide developing-out emulsion is stabilized by the incorporation therein of a complex halide of ruthenium, palladium, or iridium. The halide may have the formula R2RuX6, R2PdX4, R2PdX6, R2IrX6, or R3IrX6, wherein R is H, alkali metal, or ammonium and X is halogen (e.g. Cl or Br). The compounds sometimes increase the speed, and in this case may be used in very small quantities. Details of speed, gamma, and fog values for additions of ammonium chloropalladite, and ammonium chloroiridite with a given developer under different conditions of storage are given. The stabilized emulsions may be developed with developers containing hydroquinone, p-aminophenol or its derivatives, pyrogallol, p-phenylenediamine or its derivatives, or phenylhydroxylamine. Other compounds that may be used are potassium chloropalladate, ammonium chlororuthenate, potassium and sodium chloropalladite, and ammonium bromopalladate. The compounds may be added before or during precipitation of the silver halide, before or during the first digestion (ripening), before or during the second digestion, or just before coating. Sulphur sensitizers (e.g. thiourea, allyl isothiocyanate, thiosinamine, or a metal, e.g. sodium, potassium, cadmium, or calcium, or ammonium thiocyanate, including one or more thiocyanates with a sulphur sensitizer other than a thiocyanate) may also be added. Both the compound and the sulphur sensitizer are preferably present during the second digestion, and the pH of the emulsion is preferably adjusted to between 5 and 7. The emulsions may be sensitized with any of the usual dyes. e.g. erythrosin, Congo Red, monomethine-, trimethine-, pentamethine-, or heptamethine-cyanines, merocyanines, hemicyanines, or hemioxonols, and supersensitizing mixtures may be used. Hardening, setting, or stabilizing agents may be added. In an example, to three batches of a gelatino-silver bromiodide emulsion are added (a) sodium thiocyanate, (b) sodium thiocyanate, ammonium chloropalladate, and ascorbic acid (reducing agent), and (c) sodium thiocyanate and larger quantities of ammonium chloropalladate and ascorbic acid. Details of speed, gamma, and' fog values for a specified developer are given. The use of osmium compounds is referred to. Specifications 450,958, 479,970, 515,145, and 517,769 are referred to.