Abstract: The invention relates to a low-pressure mercury vapor discharge lamp (10) comprising a metal compound which is selected from the group formed by compounds of titanium, zirconium, hafnium and their mixtures. The effect of adding the metal compound selected from said group to the gas filling of the discharge space (14) results in an increased efficiency of the low-pressure gas discharge lamp (10), because part of the emitted light from the discharge space (14) is in the visible range of the electromagnetic spectrum. In one embodiment of the invention, the low-pressure gas discharge lamp (10) produces substantially white light without the use of a luminescent layer (16) comprising a luminescent material. In another embodiment of the invention, the luminescent layer (16) is applied to the discharge vessel (12) of the low-pressure gas discharge lamp (10). The light emitted by the luminescent material can be mixed with the light emitted from the discharge space (14) to produce the required color.

Abstract: A discharge units comprises a transparent envelope filled with a discharge gas containing mercury, and electrodes for exciting the gases by applying an electric field. It has been found that if, apart from the mercury vapour, the gas is about 99% argon and of the order of 0.1-1% krypton then the proportion of near-visible UV lines is increased, in relation to the 254-nm line, particularly if pulsed excitation is used. This increases the efficiency of the lamp when used to excite visible phosphors.