Discharge lamp with optimized salt filling

Abstract

A discharge lamp has a discharge vessel for generating an arc discharge between two electrodes. The discharge vessel contains an inert gas, and metal halides. The lamp further comprises an outer envelope surrounding the discharge vessel. The outer envelope is made of transparent material containing Potassium in a maximum concentration of 10 ppm by relation to the weight. The metal halides are contained in the discharge vessel in an amount of 3-6 μg/μl of the inner volume of the vessel, preferably 5±0.5 μg/μl. The lamp exhibits an improved long term lumen maintenance and may have a physical lifetime exceeding 4000 h net burning time.

Dependencies are inferred from the claim text.