Abstract: A projection television system comprising a cathode-ray tube having a face plate, a display screen coated with a phosphor of the type ZnS:Ag and an interference filter arranged between the display screen and the face plate.The ZnS:Ag has an admixture which slightly increases the y-coordinate of the light emitted by the phosphor.This enables an increased maximum luminance in the white-D-point without the y-coordinate of the light emitted by the cathode-ray tube becoming too low.

Abstract: Blue-luminescing lanthanum-gadolinium-oxybromide, activated by trivalent cerium, which oxybromide is also activated by trivalent terbium and is defined by the molecular formulaLa.sub.1-x-y-z Gd.sub.x Ce.sub.y Tb.sub.z OBr,in which0.25.ltoreq.x.ltoreq.1-y-z,0.002.ltoreq.y.ltoreq.0.05,0.0001.ltoreq.z.ltoreq.0.005 and y.ltoreq.z.

Abstract: Phosphors used in colour cathode ray tubes, particularly but not exclusively projection television tubes, have colour point standards or chromaticities modified to conform to European Broadcasting Union (EBU) standards by disposing an interference filter in the light-path from the phosphor, for example, between the phosphor and the faceplate, which has a peak gain greater than unity over a selected part of the frequency spectrum. As a result, an efficient broadband phosphor can be employed to obtain the desired chromaticity and thereby increase the white-D luminance of projection television systems.