PRISM SHEET HAVING CONCAVE PENTAGONAL

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 alpha of the apex is 30° <= alpha <= 120°, the exterior angle ß formed by the upper slant side and the lower slant side is ß < 180°, the interior angle y of the lower vertex formed by the lower slant side and the base is 5° <= Y &LE; 85<°> and the length w of the base is 30µm <= w <= 100µm. Preferably, the interior angle alpha of the apex may be 40° <= ALPHA &LE; 100<°>, the exterior angle ß formed by the upper slant side and the lower slant side may be 160° <= ß &LE; 179<°>, and the interior angle y of the lower vertex formed by the lower slant side and the base may be 30<° ><= y <= 60°. Preferably, the length w of the base may be 40µm <= w <= 60µm.