| 摘要 |
An automotive discharge bulb having a light emitting tube includes a ceramic tube with paired electrodes oppositely placed, and contains a light emitting material and starting rare gas. A transversal section of the ceramic tube is longitudinally elongated. Because the capacity of an enclosed space of the ceramic tube is small, after discharging begins, the enclosed space temperature increases. Consequently, the ceramic tube has a good luminous flux rising characteristic. Because of the small surface area of the ceramic tube, the load imposed on the wall surface increases. Consequently, the ceramic tube has good luminous efficiency. In the ceramic tube having a longitudinally elongated transversal section, an arc generated into an upwardly convex shape and the tube wall do not make contact. Thermal shock resistance required of the ceramic tube is alleviated, durability is enhanced, and the ceramic tube is made of a ceramic material hitherto unusable.
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