| 摘要 |
PROBLEM TO BE SOLVED: To provide an HID lamp of relatively low power having high lamp efficiency.SOLUTION: To achieve a discharge lamp suitable to operate in reduced nominal electric power, such as 20-30 W, a lamp including two electrodes arranged with a certain interval is proposed in a discharge container for generating arc discharge. The discharge container has filling materials having metal halide and inert gas almost without mercury. The lamp further has an external electric bulb arranged around the discharge container with a distance dfrom the discharge container. The external electric bulb is sealed and has gas filling materials having heat conductivity λ. The inner diameter dof the discharge container is preferably within the range of 2-2.7 mm. A wall thickness wis within the range of 1.4-2 mm. A heat transition coefficient λ/dis calculated as heat conductivity λ in 800°C of the filling materials of the external electric bulb, divided by the distance d. The heat transition coefficient defined in this way is lower than 150 W/(mK). |
