Light guide plate, production method therefor, and surface light source device provided with it

Abstract

A light guide plate capable of omitting use of a directional sheet such as a prism sheet as much as possible and ensuring a viewing angle without decreasing brightness in the vertical direction. A light guide plateis used for an edge-light surface illuminant device. The light guide plate comprises an emission plane, a bottom planefacing the emission planeand an incident end facewhich enters light emitted from a primary light sourceprovided in a side face between the emission planeand the bottom plane. Each of the emission planeand the bottom planecomprises a pattern having convex portions and/or concave portions formed at predetermined pitches. The pattern formed on the emission planeis orthogonal to the incident end faceand also the pattern formed on the bottom planeis parallel to the incident end face. The emission planeor the bottom planecomprises a trapezoidal convex portionand a trapezoidal concave portionwhich are alternately arranged. If a diffusion treatment is performed on the surface of each of the convex portions, the light guide plate which has reduced glare on the surface and has a superior surface quality can be obtained.