| 摘要 |
PROBLEM TO BE SOLVED: To uniformize the light emission of a whole surface, to thin a light source body and to prolong the life of a liquid crystal display element by closely surrounding at least the whole side peripheral surface of a cold cathode tube by a light guiding part having a specified refractive index. SOLUTION: At least the whole side peripheral surface of the cold cathode tube 1 is a surface light source body closely surrounded by the light guiding part 2 having the refractive index of 1.4-1.6. A light reflection sheet 3 is integrally attached to the side peripheral surface of the surface light source body, and a light scattering layer 4 and the light reflection sheet 3' are integrally attached to the lower surface of it and a light diffusion sheet 5 and a prism sheet 6 are integrally attached to the upper surface of it. When the refractive index is <1.4, an allowable angle range where light is totally reflected and advanced inside the light guiding part 2 becomes narrow, so that the light is hardly advanced to the corner of the light guiding part 2, and then surface light source is not made uniform. Also, when the refractive index is larger than 1.6, the light is hardly emitted from a light-emitting surface. |
