| 摘要 |
PROBLEM TO BE SOLVED: To suppress degradation, without exposing a phosphor to gas and prolong the life of a lamp by providing two kinds of phosphor layers arranged without mixing with the outside face of the inner tube of a fluorescent lamp and further adhering film outer tubes to the layers. SOLUTION: This fluorescent lamp is made to have a dual pipe structure such that a phosphor layer 13 is fixed to the outside face of borosilicate glass inner tube 11, and an outer tube 12 of a film visible light transmissive material is adhered to the layer 13. This phosphor layer 13 is applied in a sheet shape and is formed without mixing a phosphor A 21 and a phosphor B 22, so that they may not be superposed. The sizes of the application ranges of these phosphors A and B are determined for such shapes as a rectangle, a dot shape and a stripe shape and about 1mm×0.3mm. The sizes for which color irregularity is not concerned when the fluorescent lamp is seen, are determined. At this stage, because a positive column and mercury gas exist only in the inner tube 11, the phosphor layer 13 is not exposed to these gases, degradation of the phosphors is suppressed and the life of the lamp can be prolonged.
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