JPS5665453A - High-pressure metal vapor discharge lamp - Google Patents

Abstract

PURPOSE:To minimize the deterioration of the luminous flux of a high-pressure metal discharge lamp which may be caused in the initial stage of lighting, and enhance the maintenance of the luminous flux by charging an outer tube, which contains an emission tube and whose inner wall is covered with a luminescent material, with a mixture gas consisting of an inert gas and oxygen whose ratio to the inert gas is not more than a given value. CONSTITUTION:An outer tube 1 containing an emission tube 3, the inner wall of which is covered with a phosphor layer 2, is charged with a mixture gas consisting of an inert gas and oxygen, the ratio of oxygen to the inert gas being not higher than 0.5% at a pressure of 50-600 Torr. As a result, the deposition and preciptation of carbon on the phosphor layer 2, which might be caused by ultraviolet rays and heat emitted from the tube 3 and which might result from any remaining gases that are produced during the treatment of the phosphor layer 2 and a metal frame wire 4 which supports the tube 3, can be prevented. Consequently, the emission from the phosphor is not obstructed, the deterioration of the luminous flux in the initial stage of lighting can be minimized, and the maintenance of the luminous flux can be enhanced.