| 摘要 |
PROBLEM TO BE SOLVED: To decrease abnormal emission of light due to reflection on an edge by connecting protrusions each made by a pair of slopes with curved faces having an almost arc cross section in a specified range near the entrance face. SOLUTION: The light guide plate 2 is formed by injection molding of a transparent resin into a body having a wedge cross section. Illumination light from a primary light source is introduced through an entrance face 2A and repeatedly reflected between an exit face and a back face 2B to propagate while the component of light having an angle smaller than the critical angle exits from the exit face and from the back face 2B during reflection. The prism face formed on the back face 2B of the light guide plate 2 consists of minute protrusions repeatedly formed along the entrance face 2A. The minute protrusion has a pair of slopes 2E, 2F extended in the direction almost perpendicular to the entrance face 2A, and the pair of slopes 2E, 2F are directly connected to form a triangular cross section. The protrusions are smoothly connected with curved faces each having an almost arc cross section in a specified range near the entrance face 2A. Thereby, the valley part in the grooves made by the repeated protrusions is not formed as a sharp notch in the light guide plate 2. |
