Patent ID: 8632238

Claim:
A surface light source device comprising: a light source; and a light guide plate configured to introduces light emitted from the light source through a light incident surface to output the light through a light exit surface, the light guide plate including a light introduction part configured to traps the light emitted from the light source through the light incident surface, the light guide plate including a light guide plate body being provided to be continuously joined to the light introduction part, a thickness of the light guide plate body being smaller than a maximum thickness of the light introduction part, wherein the light introduction part includes an inclined surface on at least one of a surface on a light exit side of the light guide plate and an opposite surface thereof, the inclined surface is inclined from a surface in a portion having a thickness larger than the thickness of the light guide plate body toward an end of a surface of the light guide plate body, the light guide plate body includes a light exit pattern on at least one of a surface on the light exit side of the light guide plate and an opposite surface thereof, the light exit pattern configured to outputs the light in the light guide plate body through the light exit surface, and the thickness of the light guide plate body is configured to be gradually increased with increasing distance from the light source in a region near the light source of the light guide plate body.