| 摘要 |
PURPOSE:To uniformize a distribution of brightness in a fluorescent tube, by composing grids so that their control function becomes large at both-end parts, where a cathode filament voltage is high, and becomes small at the central part, where it is low. CONSTITUTION:With anodes having phosphor 3 being arranged in dot shapes on a glass substrate 1, meshy grids 15 arranged on both sides, and two cathode filaments 7 arranged above, a fluorescent tube such as a phosphor-dotted array tube is formed. Then, the grids 15 are made of a sheet of plate and arranged so that a long hole-opening part 16 exposing the phosphor 3 has opening width t2 large at a central part of the filament 7 and opening width t1 narrow at the both end parts, with their space combined in secondary curve-shapes. And, the grids 15 are provided with control functions corresponding to the emission amount of thermions in the filament 7. Therefore, a distribution of brightness in the longitudinal direction can be utilized with simple composition.
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