| 摘要 |
PROBLEM TO BE SOLVED: To efficiently introduce visible light into a light entering the end face of a light-guiding plate, even if a facing position with respect to the light entering end face of the light-guiding plate of a fluorescent lamp arranged along the light entering end face of the light-guiding plate is erratic due to rotation or the like. SOLUTION: A discharge medium is filled into a tubular bulb 1, and internal electrodes 4 are enclosed inside both its ends. A phosphor film 3 having an opening (aperture) 2 is formed on the inside surface of the bulb 1. The opening (aperture) 2 is formed into spiral shape along a bulb axis. A pitch P of the opening (aperture) 2 is 1 mm or more and less than 25 mm, and the opening width W is 1/8-2/3 of the inside diameter of the bulb 1.
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