THORIUM-FREE DISCHARGE LAMP

摘要

A high-pressure gas discharge lamp 10 is described with a sealed discharge vessel 20 with an inner discharge space 22. Two electrodes 24 project into the discharge space 22. The filling in the discharge space 22 comprises metal halides and a rare gas. In order to provide a lamp with good environmental properties suited for automotive use, in particular with good lumen maintenance, the filling is free of Hg and Th and comprises halides in an amount of 7.1-11.4 µg/mm3 of the volume of the discharge space 22. The halides comprise at least NaI and ScI3, provided in such amounts that a ratio of the masses of NaI to ScI3 is 1.2-1.6.