| 摘要 |
A method for manufacturing an arc tube which obtains a high luminous flux retention rate by completely removing impurities, such as oxides, from the surfaces of the electrodes within the arc tube. An exhaust tube is connected to a glass tube of an arc tube in which a pair of electrodes are oppositely disposed. After gas is exhausted through the exhaust tube from the glass tube, inert gas is introduced. An arc discharge generating circuit is connected to the oppositely disposed electrodes, and an ion bombardment process is carried out in which an arc discharge is caused between the electrodes in the inert gas atmosphere at a current density of 30 to 100 A/mm2. Due to the arc discharge process, impurities (oxides), which lead to a reduction of the luminous flux retention rate, are completely removed from the electrode surfaces. Gas is exhausted from the glass tube, and then a degassing process is carried out to degas the glass tube while it is heated to thus completely remove impurities from the inner wall of the glass tube. Metal halide as a luminous material, mercury, and a rare gas are successively introduced into the glass tube through the exhaust tube, and the exhaust tube is tipped off.
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