METAL HALIDE LAMP, DISCHARGE LAMP LIGHTING DEVICE AND LIGHTING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a metal halide lamp capable of improving in service life and capable of reducing the total cost, while securing lamp efficiency to a required degree or more even though being a small sized, a discharge lamp lighting device and a lighting system using the lamp. SOLUTION: A metal halide lamp includes I and Br by 1 to 50, desirably, 1 to 30, most desirably, a rate of 1 to 20 in the mole ratio (%) as halogen by sealing halide of light emitting metal including as least Sc-Na together with mercury and rare gas inside a light transmissive discharge vessel 1a where a diameter of a sealing part 1a2 positioned on the lower side at least at lighting time is formed smaller than an outer diameter of the central part of a discharge space 1a1 and has a light emitting tube 1 having a tube wall load of 10 to 17 W/cm2 and rated lamp electric power of 76 to 125 W. This constitution can provide a mercury lamp ballast adaptive metal halide lamp having lamp efficiency not less than 70 Im/W and a light flux maintenance factor not less than 80%. Corrosion of a tungsten electrode is not seen up to lighting 3000 hours. An increase in extinction voltage can also be prevented by largely restraining dissipation of Na.