| 摘要 |
A low-pressure mercury vapor discharge lamp includes a light-transmitting tube containing discharge medium, a pair of discharge electrodes each mounted in a vicinity of respective end portions of the tube, a transparent conductive film formed of metallic oxide as a main component thereof and coated on an inner surface of the light-transmitting tube between the discharge electrodes, and the transparent conductive film having a thickness on one end portion of the tube relatively thinner than a thickness of the transparent conductive film on the other end portion of the tube. A phosphor film is coated on an inside surface of the transparent conductive film on an inside surface of the tube. The discharge lamp has a feature reduced in blackening on the transparent conductive film. A portion more capable of decreasing ultraviolet causing electrical resistance to change, such as the thick portion of the phosphor film and/or an ultraviolet decreasing film, is coated to the inside surface of the conductive film where the stability of the resistance relatively low, specifically the thick portion of conductive film in which more undecomposed material remains. The change in the resistance of the conductive film is balanced between both ends of the lamp bulb.
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