QUARTZ GLASS WITH REDUCED ULTRAVIOLET RADIATION TRANSMISSIVITY, METHOD OF ITS MANUFACTURE, AND ELECTRICAL DISCHARGE LAMP USING SUCH GLASS

摘要

. Ultraviolet (UV) radiation in the UV-C and UV-B bands, which is particularly dangerous, is absorbed and filtered by quartz glass doped with between 0.065% and 3.25%; and preferably between 0.065% and 1.3%, by weight, of cerium metal, or cerium as such. Preferably, the cerium is added to quartz sand and/or rock crystal, in form of a fine-grained powder of up to 2 0 .mu. m grain size, in form of cerium aluminate (CeAlO3), present in up to about 5% by weight, and preferably up to about 2%, and melted together in a single step. The quartz glass so obtained is particularly suitable for a metal halide discharge lamp, e.g. as an outer envelope (1), or as the discharge vessel (27) itself, or for halogen incandescent lamps, to form the quartz-glass light bulb or an envelope therefor. A small quantity of titanium oxide, up to about 0.05%, may be added as a further doping agent to the melt to further improve the UV absorption in the B and C bands.