Patent ID: 8920017

Claim:
A surface light source device comprising: a plurality of light sources disposed to face a light incident surface; and a light guide plate that guides light emitted from the plurality of light sources through the light incident surface to output the light emitted to an outside through a light exit surface, wherein the light guide plate includes light exit patterns on at least one of a surface where light exits and an opposite surface thereof, the light exit patterns outputting the light in the light guide plate to the outside through the light exit surface, and wherein maximum inclined angles of the light exit patterns decrease with increasing distance from the light incident surface in a region near the light incident surface, and the maximum inclined angles of the light exit patterns decrease or remain constant with increasing distance from the light incident surface in a region distant from the region near the light incident surface, a maximum inclined angle of a light exit pattern being a maximum inclined angle among inclined angles of tangents drawn to surfaces of the light exit pattern in a section passing through a center axis of the light exit pattern, and the maximum inclined angles of the light exit patterns located in a region at a distance from the light exit pattern located closest to the light incident surface, the distance being equal to an interval between two of the plurality of light sources, are larger than a minimum value of the maximum inclined angles of all the light exit patterns.