| abstract |
A cathode ray tube, particularly, but not exclusively, a projection cathode ray tube having a multilayer interference filter (22) disposed between the cathodoluminescent screen (23) and the interior side of the faceplate (12). The interference filter (22) comprises alternate layers having high (H) and low (L) refractive indices. Known filters suffer from crazing after the tube processing is completed, as cathode ray tubes having them are heated up to between 4OO°C and 46O°C during the normal processing of the cathode ray tubes. It has been found that crazing is eliminated substantially if the high refractive index material is niobium pentoxide and the low refractive index material is either silicon oxide or magnesium fluoride. Deposition of the layers can be done by sputtering or evaporation onto a substrate which is cool relative known substrate temperatures used for other materials. |