| 摘要 |
PROBLEM TO BE SOLVED: To obtain a back light device with its superior cost effectiveness and mass-productivity capable of being a surface light source without applying a divergence reflection pattern material. SOLUTION: A light guide body part 8 at which tubular light sources 1, 1 and reflection plates 2, 2 are mounted on both ends thereof is formed of which a light guide layer 3 for transmitting incident light from the tubular light source 1 and a triangular layer 4 with its cross-section formed in the form of saw-teeth for emitting light transmitted from the light guide layer 3. The refractive index of the light guide layer 3 is set to be the largest, and the refractive index of the triangular layer 4 is set to be changed in a direction in which the index increases as it is further removed from the tubular light source 1. The apex angle of the saw-tooth part of the triangular layer 4 is set to increase as it is further removed from the tubular light source 1 so as to strengthen directivity of light emitted from the light guide body part 8 in the front face direction of a liquid crystal panel. |
