| 摘要 |
PROBLEM TO BE SOLVED: To prevent deterioration of an optical lumen maintenance factor, and damaging of appearance quality by coloring of tubular bodies surrounding a light-emitting tube, such as for example an outside tube and a sleeve or the like while obtaining a high light-emitting efficiency. SOLUTION: In the inside of the light-emitting tube 3 in which an outside envelope is composed of translucent ceramics, a pair of electrodes 20a, 20b are arranged, and a halogenated compound of sodium is enclosed, when the inner diameter of the light-emitting tube 3 is made D (mm) and a distance between the electrodes 20a, 20b is made L (mm), a relational equation of L/D≥4 is satisfied. Outside the light-emitting tube 3, out of an electric discharge space of the light-emitting tube 3, there are tubular bodies 2, 31 which are arranged so as to enclose a part including at least the distance L between the pair of electrodes 20a, 20b, and out of the light-emitting tube 3, in between a part ranging from the distance L of the pair of electrodes 20a, 20b up to the tubular bodies 2, 31, when the outer diameter of the light-emitting tube 3 is r (mm) and the inner diameter of the tubular bodies 2, 31 is made R (mm) at the part where each approaches the closest, a relational equation R/r≥3.0 is satisfied. COPYRIGHT: (C)2008,JPO&INPIT |
