| 摘要 |
PROBLEM TO BE SOLVED: To improve direct below illuminance at the time of base upward lighting, by forming the light transmissive envelope of a lamp bulb type fluorescent lamp into a flat type spherical body, wherein width along the horizontal direction of a lower bottom surface is longer than height height along a vertical direction. SOLUTION: An electrode coil 28 is sealedly mounted on both the end parts of a glass bulb 25. This fluorescent lamp 21 is covered by a globe 35 which is a light transmissive envelope. The flat type spherical body 37 of the globe 35 is formed so that width W, along the horizontal direction of a curved lower bottom surface 37a forming a lower bottom surface at the time of base upward lighting, is longer than the height (h) of a curved side surface 37b along a vertical direction. Since the curved lower bottom surface 37a has a wider area than the curved side surface 37b, a light beam, radiated outside by the wider part, is increased. Also since light, radiated to a base 3 side, is reflected to the lower bottom surface 37a side when a reflecting film 41 is formed on the upper part inner surface of the globe 35, direct below illuminance is moreover improved. In addition, the forming a light diffusion film 42 on the inner side of the globe 35, improves the brightness uniformity degree of the outer surface of the globe 35. |
