| 摘要 |
An asymmetric prism sheet 15 has a plurality of projections 17 having prism shape on its surface. The projection 17 comprises a first inclined surface 17a having a relatively gentle slope (easy slope) and a second inclined surface 17b having a relatively steep slope (steep slope). A base angle 17d on the side of the second surface 17b is alpha ° and a base angle 17c on the side of the first surface 17a is beta ° . In the case that the light enters into the asymmetric prism sheet 15, which has the above-mentioned structure, from the bottom surface 15a (light guide plate 11), the light is mainly emitted in the substantially vertical direction (a direction inclined by relatively small angle to the vertical direction) in the first inclined surface 17a (arrows X), and is mainly emitted in the inclined direction (a direction inclined by relatively large angle to the vertical direction) in the second inclined surface 17b (arrows Y). |
