GB1253446A - X-ray intensifying screen layers - Google Patents

Abstract

1,253,446. Radiographic films. EASTMAN KODAK CO. 20 Feb., 1969 [22 Feb., 1968], No. 9295/69. Heading H5R. An X-ray intensifying screen includes a layer of binder containing a dispersion of particles of an alloy comprising bismuth and lead. Preferably, the bismuth content of the alloy is at least 50% by weight, and the lead content at least 25% by weight; the particle size is less than 20 microns diameter; the amount of alloy particles in the layer is not less than 25 % by weight; and the amount of alloy per unit area is 0À1 to 10 grams per square decimeter. The alloy preferably should also contain tin and/or cadmium, and may contain tin and mercury. The binder may be unhardened gelatin, or a thermoplastic resin, gum, or gel, and the intensifier may be either self-supporting, and used in contact with a light-sensitive radiographic film-which contains 3À6 grams or more light-sensitive silver halide emulsion per square foot-or may be integral with the film. The screen may be prepared by mixing the molten alloy with aqueous gelatin solution, stirring while the mixture is cooled to disperse the alloy as small particles, and coating on a poly(ethylene terephthalate) film support, setting the gelatin by cooling, and drying. When the screen is integral with the film, the resolution is increased by the melting of the particles to form an alloy rich layer adjacent the film; the same effect may be obtained in the case of a separate intensifying screen, by coating the layer on a temporary support, and wet-transferring it to a permanent supporting sheet with its alloy-rich side outermost, so that the latter may be placed in contact with the radiographic film.