GB699340A - Improvements in photosensitive silver halide emulsions for use in half-tone photographic processes - Google Patents

Abstract

699,340. Half-tone photography. KODAKLtd. June 30, 1952 [June 29, 1951], No. 16362/52. Drawings to Specification. Class 98(ii) A silver halide emulsion layer has a half-tone pattern of dots sensitive at the centres to longer wave-length light than at the corners. The centres may be sensitive to green and blue, to red and blue, or to green, red and blue, and the corners to blue; the green or red sensitivity varying continuously from a maximum at the centres to a minimum at the corners. The layer is made by application of optical sensitizer from a dot pattern printing plate which may be of letterpress, intaglio or even litho type to a litho or process type emulsion; the normal diffusion of sensitizer providing the continuous variation from centre to corner of the dots. Exposure of the layer through a blue filter leads to production of a continuous tone image; through a green or yellow filter to a half-tone image, or a line image may be superimposed on the latter by use of a blue filter. Two half-tone patterns may be provided on a single emulsion without registration, such as one corresponding to a 50-line screen using a green sensitizer and the other to a 120-line screen using a red sensitizer, when a green filter would provide newspaper half-tones and a red filter magazine half-tones. In all cases a blue filter gives continuous tones. As green and red sensitizers, respectively, 1-carboxymethyl-5-[(3-ethyl-2(1)- benzoxazolylidene) - ethylidene] - 3 - phenyl - 2 - thio hydantoin and 5-[(3-ethyl-2(3)-benzthiazolylidene)-butenylidene]-3-#-sulphorhodanine are quoted. Drawings show application of sensitizer from a wash-off relief film and from an intaglio printing roll, with dot patterns, to an emulsion; and the sensitivity variation produced in the latter. Specifications 529,033, 532,098, 540,451, 541,510, 541,513, 541,514, 541,515, 544,134, 552,368 and 558,099 are referred to.