Patent ID: 8400585
Filing Date: 2013-03-19
Classification: G02B,G02F

Abstract:
1. A surface light source device comprising: a point source of light; and a light guide plate provided at a position facing the point source of light and causing light from the point source of light to be introduced from a light incident end face and be emitted from a light emission surface to outside, wherein the light guide plate comprises a light guide substrate formed of a transparent or translucent material provided with a directivity converting portion and light emitting means, wherein the light guide substrate is integrally configured with a light introducing portion provided at a position facing the point source of light and a light guide plate body including the light emission surface from which light introduced from the light introducing portion is emitted to outside, wherein the light guide plate body has a thickness equal to or larger than a minimum thickness of the light introducing portion in the light guide substrate, wherein, on a surface of the light guide substrate on a light emission side or a surface thereof on a side opposite thereto, the light introducing portion is flatly continuous from a portion of the light introducing portion having a thickness equal to a thickness of the light guide plate body toward an end edge of the light introducing portion side of the light guide plate body, or is continuous with an inclined surface from a portion of the light introducing portion having a thickness smaller than the thickness of the light guide plate body toward the end edge of the light introducing portion side of the light guide plate body, wherein the directivity converting portion traps light entering the light introducing portion from the light incident end face inside the light guide plate by narrowing a directivity spread of the light entering the light introducing portion in a thickness direction of the light guide substrate, and is formed on a surface of the light introducing portion on a light emission side or a surface thereof on a side opposite thereto, and wherein the light emitting means emits the light trapped inside the light guide plate body from the light emission surface to outside, and is formed in the light guide plate body.