Patent ID: 8033710

Claim:
A light guide plate for a surface light source, the light guide plate having at least one of a pair of side surfaces opposite to each other as a light incident surface, from which light source light is guided, wherein: at least one of both surfaces of the light guide plate in a thickness direction thereof is a light distribution control surface for adjusting light distribution characteristics of light emitted from the light guide plate, the light distribution control surface having: a plurality of flat surfaces formed thereon which extend in a direction perpendicular to the light incident surface and which are arranged side by side in a longitudinal direction of the light incident surface on the light distribution control surface, each of the plurality of flat surfaces is formed in such a way as to vary in width in the longitudinal direction of the light incident surface in the direction perpendicular to the light incident surface; and a plurality of prisms formed thereon which extend in the longitudinal direction of the light incident surface in areas other than the flat surfaces of the light distribution control surface, the plurality of prisms being arranged in the direction perpendicular to the light incident surface, and each prism from among the plurality of prisms having a shape of triangle when viewed in the longitudinal direction of the light incident surface.