| 摘要 |
PURPOSE:To decrease a blackening phenomenon when a lamp is lighted further reduce its deterioration of output of light, by specifying a particle mean diameter of fluorescent material in first and second fluorescent material applied layers to a small range. CONSTITUTION:A base 12, insulating, guiding and sealing electric lead-in wires 11, is provided to both ends of a mercury sealed glass tube 13, then the first fluorescent material layer 14 and the second fluorescent material layer 15 are successively coated to an internal wall of the mercury sealed glass tube 13. The first fluorescent material layer 14 consists of a fluorescent material of 3-7mu in particle mean diameter, while the seconf fluorescent material layer 15 is provided with a material in a range of 1.0-3.5mu in particle mean diameter, further the second layer is formed by the fluorescent material in diameter with a smaller value than the particle mean diameter of the fluorescent material in the first fluorescent material layer 14. |
