| 摘要 |
PURPOSE:To improve the light distribution characteristics near the top of a luminous tube by arranging between the inner and outer tubes of a discharge tube, an intermediate cylinder that forms a discharge path, providing two or more electrodes at the base end between this intermediate cylinder and the outer tube, and forming an optical reflection film at the top on the tip side of the inner tube. CONSTITUTION:An outer tube 10 that is made of transparent material and is almost cylindrical and whose top is semi-spherical is sealed to a base 11 and the inner surface of the outer tube 10 is coated with phosphor 13. An inner tube 15 made of transparent material is concentrically arranged in this outer tube 10 and the inner surface is coated with phosphor 16. A cathode 22 is arranged at the inner part and an opening 15a is formed at the base section side. In addition, an intermediate cylinder 18 is arranged between the outer and inner tubes 10 and 15 so as to enclose the inner tube 15 made of transparent material. The base section side 28a of this intermediate cylinder 18 is sealed to the base 11 and the tip side 18b is opened, then two or more anodes 20 are arranged at the base section side between the outer tube 10 and intermediate cylinder 18. Besides, an optical reflection film 25 is formed at the tip section of the inner tube 15 and the light distribution characteristics near the top of a luminous tube is improved through a discharge path formed by the intermediate cylinder 18. |
