| 摘要 |
PURPOSE:To prevent electrode sputters from introducing to an electric discharge space and preclude risk of blackneing phenomenon by providing a light emission part having an electric discharge space with flat section, and also providing an electrode accommodation part for accommodation of electrodes at the two ends of the discharge space and having a wall part in the discharge path from electrode. CONSTITUTION:The electric discharge space of a light emitting tube 2 having a U-bent light emission part is embodied in a flattened rectangular form, and at the end of this tube 2, an electrode accommodation part 29 is formed into cylindrical form to accommodate an anode 4 and a cathode 5. In the tube 2, mercuray and argon gas are encapsulated. The inner dia. of the accommodation part 29 is made larger than the shorter axis of the flattened discharge space, and a wall part 30 is formed. The form of discharging is, therefore, such that the mercury vapor layer on the shorter axis side formed flat is thin, which allows suppressing the self-absorption of ultraviolet rays due to the mercury. Even though the current density is increased, scattered matter from electrode attaches to the wall part 30 and intrusion to the discharge space can be suppressed. This provides a light source presenting a high output and a high rate of ultraviolet ray maintenance, wherein blackening of the light emitting tube is well prevented. |
