| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface light source device having a good light utilization efficiency and a luminance distribution sharp in the normal direction of its light-emitting surface and to provide a lens film therefor. SOLUTION: This surface light source device has a light source 2 placed on the side end face of a non-light-diffusive light guide plate 1, a light reflector 3 on the back of the plate, and on the light-emitting surface side of the plate a lens film 5 having a number of triangular prisms, with the prism side directed to the light guide plate 1. The shape of the triangular prism is such that when the emission peak angle of light from the light guide plate with respect to the horizontal direction of the light-emitting surface of the lens film 5 is (x) [ deg.], the apex angle (a) of the triangular prism is (90-x)÷2+(x) [ deg.], and that the angle (b) on the light source side when the apex angle is divided by the normal is (x) [ deg.] while the angle (c) opposite to the light source side is (90-x)÷2[ deg.].
|
