GB1322393A - X-ray intensifying screen - Google Patents

Abstract

1322393 Luminescent screens KODAK Ltd 19 April 1971 [26 Feb 1970] 9258/70 Heading C4S [Also in Division H5] An X-ray intensifying screen comprises a supported layer of particulate X-ray intensifying substance dispersed in a binder and synthetic resin compatible therewith, defined as a resin which on admixture with the gelatine forms a clear composition. Photographic materials may include a layer of photographic silver halide emulsion separate from or integral with the screen. "X-ray intensifying substance" is defined as substances which enhance the effect of X-rays on photographic materials, e.g. metallic lead and lead compounds which, as well as shielding photographic material from scattered soft X-rays, produce long wavelength and # radiation from short wavelength radiation. Phosphors may include calcium tungstate, barium lead sulphate, and magnesium tungstate. Metallic Pb powder is preferably 1-100 Á, e.g. 3-8 Á, particle size. Typical Pb compounds include lead oxides (e.g. PbO and Pb 3 O 4 ), inorganic or organic lead salts, (e.g. lead carbonate, lead oxalate, and tetraalkyl lead. Lead oxide screens are preferably coated with an aqueous acidic solution (e.g. aqueous sulphuric acid) and when combined with a Ag halide layer, separation is preferably by a stripping layer (e.g. layers of unhardened gelatine or cellulose ether phthalate) or protective layer such as gelatine. The resin is preferably 25 to 75% by wt. of the total binder, mechanical strength increasing content, and may be added to gelatine solutions as latexes before coating. The binder may include plasticizers to enhance flexibility and photographic hardening agents to raise the melting point. Supports may be baryta-coated paper, cellulose ester film base, polystyrene or metal foil and may be given one or a series of coatings. The layers may be coated over the photoemulsion, on the opposite side of the support from the emulsion or on both sides. The screen may be made removable by stripping or washing with a solvent. In examples, copoly- (butylacrylate acrylic acid) containing 20% solids was mixed with calcium tungstate in a vibration mixer, to which was added 15% gelatine solution, proportions being given, the mix being coated on glass, then backed with paper. Polyvinyl alcohol and alkylacrylate-acrylic acid copolymers are instanced resins, preferably copoly(butylacrylate - acrylic acid having a monomer weight ratio of 90 : 10. Resins may also be as in Specifications 819,645, 1,010,917, 1,057,976, 1,073,238, 1,113,527, 1,115,014, 1,124,284, 1,145,979 and 1,148,482.