GB774655A - Improvements in photographic light-sensitive materials - Google Patents

Abstract

774,655. Photographic light-sensitive material. KODAK, Ltd. Sept. 5, 1955 [Sept. 9, 1954], No. 25408/55. Drawings to Specification. Class 98(2) Black-and-white photographic lightsensitive material having improved printing characteristics comprises a transparent support having on one side thereof two silver halide emulsion layers, the emulsion layer nearer the support having a sensitivity in the green spectral region at least one-tenth of that in the blue spectral region and having substantially no sensitivity in the red spectral region, and the emulsion layer further from the support having substantially equal sensitivity in the blue, green and red spectral regions, and having a speed at least log E = +0.3 faster than the speed of the other emulsion layer. The silver halide may be principally silver bromide, the emulsion layer nearer the support may have a green-sensitivity substantially equal to its blue-sensitivity, and the emulsion layer further from the support may have a blue : green : red spectral sensitivity ratio of 6 : 5 : 4 or of 5 : 4 : 3 to 5. The material is capable of giving a reduced density scale upon red light exposure while retaining adequate gradient in the shoulder portion of the characteristic curve and the advantages of increased exposure latitude. The support may be coated with a gelantino silver bromide layer sensitized with a green sensitizing dye to give a green-sensitivity at least one-tenth of and preferably about equal to the inherent blue-sensitivity of the emulsion, with an optional interlayer, and with a gelatino silver bromide emulsion which is panchromatically sensitized to give substantially equal blue, green and red sensitivities. The support may carry an antihalation layer. In an example, a subbed cellulose acetate support carrying an antihalation backing layer is coated first with a gelatino silver bromide emulsion sensitized with 1 : 1<SP>1</SP> - diethyl - pseudocyanine iodide and 1<SP>1</SP> : 2 - diethylthia - 2' - cyanine iodide and having a spectral sensitivity ratio of blue to green 10 : 1, and then with a gelatino silver bromide emulsion sensitized with 2 : 2<SP>1</SP> - diethyl - 8 - methyl thiacarbocyanine iodide to give a green : red sensitivity ratio of 6 : 5 and having a speed of about log E = +1.5 greater than that of the first emulsion. At the thickness at which they are coated, the two emulsions have about the same contrast in the straight line portion of the characteristic curve.