Patent ID: 6997595
Filing Date: 2006-02-14
Classification: G02B,G02F

Abstract:
1. A brightness enhancement article for transmitting incoming light and preferentially redirecting the light in a viewing direction, comprising a prism surface for receiving the light comprising a series of spaced-apart prism elements having a substantially trapezoidal cross-section, each said trapezoidal prism element comprising: (a) a face plane disposed toward the incoming light; (b) a base plane larger than the face plane, disposed away from the incoming light, connecting the base of the prism elements; and (c) first and second non-parallel planes extending back from said face plane to said base plane, each forming an angle (β), within the prism element between the non-parallel plane and said face plane, of greater than 90 and less than 120 degrees; wherein the ratio of height (H) or orthogonal distance between the face plane and the base plane to the pitch (P) or distance between identical points in adjacent prism for said article, provides a cutoff angle for output light as the largest of the absolute values θc  wherein α=180°−β degrees and wherein n is the index of refraction of the prism element material.