| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a discharge bulb capable of restraining Na<SP>+</SP>ion from getting out through an arc tube by reducing the influence of external electric field acting through a sealed glass bulb. <P>SOLUTION: For the discharge bulb comprising an arc tube main body formed by integrally welding a cylinder-shaped shroud glass 4 to an arc tube 2 made of quartz in which, sodium halide is enclosed as a light emitting substance so as to surround the arc tube, a positively electrifiable electrification member 20A is arranged to the position of the arc tube surrounding the sealed glass bulb 2a where the light is not effectively passing through. As the electrification member 20A is positively electrified to form a positive electric field around the sealed glass bulb 2a, and the external electric field does not effect on the Na<SP>+</SP>ion in the arc tube, the Na<SP>+</SP>ion does not get out but remains in the arc tube, emitted light does not become pale-white, and lowering of light flux is improved. <P>COPYRIGHT: (C)2003,JPO |
