| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to emit illumination light by a uniform light quantity even when the number of light sources is decreased by using approximate spot light sources as primary light sources and forming recessed parts in the portions facing the primary light sources of a slope. SOLUTION: The light guide plate 16 is formed to a shape diagonally cut off at the corner in a wedge shaped root portion on an exit surface 16B side, by which the slope 16C is formed. Further, the light guide plate 16 is formed with the recessed parts 16E on the slope 16C in the portions where the illumination light emitted from the light emitting diodes 18 are made incident at the largest light quantity, i.e., the portions facing the light emitting diodes 18. The recessed parts 16E are so formed that the cross-sectional shape viewed by cutting off by the surface parallel with an exit surface 16D attains an approximately arcuate shape. The recessed parts are formed of millor surfaces same as the slope 16C so that the illumination light is mirror- reflected. As a result, the light transmission plate 16 reflects the illumination light emitted in the front surface direction of the light emitting diodes 18 having the largest light quantity out of the illumination light emitted from the light emitting diodes 18 by these recessed parts 16E and internally propagates this light by divergent light. |
