JPS55163764A - High-pressure metal vapor discharge lamp - Google Patents

Abstract

PURPOSE:To raise color rendition of luminous tube by rising the temperature of the most cold point by designating the size of projecting area in the press direction on the side where the most cold point is formed at least of the sealed portion of a luminous tube at a specific value on the basis of rated consumed power. CONSTITUTION:When forming a discharge lamp, having the luminous tube 18 with the electrodes 4 and 7 sealed on both ends and zinc or cadmium and a given amount of mercury, together with a rare gas, filled inside, the tube wall load of which is 6-9W/cm<2> for lighting, with a consumption power of 700-2,000W, the relationship 0.006WL+1<=0.007WL+1.5(cm<2>) is kept for the sealed portion 12, where S(cm<2>) is the size of projecting area in press direction and WL(W) is the consumption power of the luminous tube 18. Thus, the temperature of the most cold point can be raised by reducing heat radiation from the outer surface of the sealed portion, and therefore its color rendition can be enhanced.