| 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 17 a having a relatively gentle slope (easy slope) and a second inclined surface 17 b having a relatively steep slope (steep slope). A base angle 17 d on the side of the second surface 17 b is alpha° and a base angle 17 c on the side of the first surface 17 a 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 15 a (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 17 a (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 17 b (arrows Y).
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