Patent ID: 7445358
Filing Date: 2008-11-04
Classification: G02B

Abstract:
1. A light guide plate comprising a plurality of unit light guide plates that are formed of a transparent resin material and which are joined together, each of the unit light guide plates having a flat rectangular light exit surface, and a back surface that is opposite the light exit surface and which has a parallel groove formed in generally a center and parallel to a side of the rectangular light exit surface, wherein the light guide plate is used with a linear light source fitted in the parallel groove and satisfying the inequality: where L 0 is the length (mm) of the light guide plate in a direction perpendicular to the parallel groove, k is the linear expansion coefficient [/° C.] of the resin material, Ts is the surface temperature [° C.] of the linear light source that has become stable after being lit, S is half of cross-sectional area [mm 2 ] of the unit light guide plate as the unit light guide plate is cut through a plane perpendicular to the parallel groove, and T=Ts−25.