| 摘要 |
786,924. Photographic emulsions. GENERAL ANILINE & FILM CORPORATION. Nov. 3, 1955 [Nov. 24, 1954], No. 31486/55. Class 98(2) A photographic emulsion comprises silver bromide grains dispersed in a colloid carrier (e.g. gelatin, polyvinyl alcohol, or a water-dispersible cellulose organic ester, polyamide, hydroxyethyl cellulose, modified polyvinyl alcohol, or partially hydrolyzed polyvinyl acetate), the grains containing from 0.001 to 0.2 mol per cent of cadmium based on the quantity of silver present in the emulsion. The emulsion has an increased sensitivity to X- and gamma-rays, but a reduced sensitivity to visible light. The cadmium ion can be introduced in the presence of a colloid carrier as a water soluble salt such as cadmium chloride or bromide mixed with alkali metal bromide solution to which is added the silver nitrate solution to precipitate the silver bromide. Alternatively, a non-halide water soluble cadmium salt such as the nitrate or acetate may be mixed with the silver nitrate. In Example 1, a solution of 74 grams of silver nitrate and 0.05 gram of cadmium nitrate in 400 ccs. of water at 68‹C. is slowly added with agitation to a solution, also at 68‹C. of 60 grams of potassium bromide and 6 grams of gelatine in 150 ccs. of water. 60 grams of gelatin are added and the mixture maintained at 68‹C. with agitation for 20 minutes. The chilled and shredded emulsion is washed until the bromide ion concentration is 100 mgms. per kilogram of liquid emulsion, the remelted emulsion is ripened for 20 minutes at 60‹C., saponin and formaldehyde are added, and the emulsion is coated on cellulose ester film. A metol-hydroquinone developer for this film is specified. In Example 2, polyvinyl alcohol is used as the emulsion binder and cadmium acetate is added to .the silver nitrate solution, the potassium nitrate formed on precipitation of the silver bromide being removed by dialysis. In Example 3, the purification by dialysis is replaced by precipitation with ammonium sulphate and washing. In Example 4, gelatin is used as the emulsion binder and cadmium chloride is added to the gelatin-potassium bromide solution. The silver bromide emulsion may be replaced by a silver bromiodide emulsion, but at least 90 per cent by weight of the silver halide should be silver bromide. The emulsion may contain sensitizing agents, and may contain a colour coupler and be processed by colour development. The saponin may be replaced by isopropylnaphthalesesulphonic acid.
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