Patent ID: 8864358

Claim:
A surface light source device in which a light source and a lightguide plate are accommodated in a frame such that an outer peripheral surface of the lightguide plate is surrounded by the frame, light emitted from the light source being incident to the lightguide plate from an end face of the lightguide plate, the light guided in the lightguide plate being output from a light output surface of the lightguide plate, wherein the frame comprises: a frame-shaped frame main body that is made of a light-absorbing material; and an auxiliary member that is attached to an inner surface of an end side on a side farther away from the light source in the frame main body and at most to an inner surface of an end portion on the side farther away from the light source in both lateral sides of the frame main body, the auxiliary member being made of a light-reflecting material, wherein a latching portion is projected in one of the frame main body and the auxiliary member, wherein a latched portion is recessed in the other of the frame main body and the auxiliary member, and wherein the latching portion is engaged with the latched portion such that the auxiliary member is prevented from floating.