| 摘要 |
A prism sheet having a concave pentagonal structure is disclosed. The prism sheet comprises a base layer, and a prism array disposed on and supported by the base layer. The prism array is composed of a plurality of prisms aligned in parallel and one beside the other. The transversal cross-section of each prism has a shape of concave pentagon, which is symmetrical about a vertical line passing the apex. The interior angle a of the apex is 30°<=alpha<=120°, the exterior angle beta formed by the upper slant side and the lower slant side is beta<180°, the interior angle gamma of the lower vertex formed by the lower slant side and the base is 5°<=gamma<=85° and the length w of the base is 30 mum<=w<=100 mum. Preferably, the interior angle alpha of the apex may be 40°<=alpha<=100°, the exterior angle beta formed by the upper slant side and the lower slant side may be 160°<=beta<=179°, and the interior angle gamma of the lower vertex formed by the lower slant side and the base may be 30°<=gamma<=60°. Preferably, the length w of the base may be 40 mum<=w<=60 mum.
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