Patent ID: 8210730
Filing Date: 2012-07-03
Classification: G02B,G02F

Abstract:
1. A surface light source device, comprising: a point light source; and a light guide plate which introduces light of the point light source therein from a light entering face and emits the same outward from a light exit face, wherein the point light source is provided at a position facing the light entering face of the light guide plate, wherein the light guide plate comprises: wherein the light introducing portion has an inclined face on a face on a light exit side of the light guide plate or the opposite face thereof, wherein the inclined face is inclined to an end of a surface of the light guide plate body from a surface of a portion thicker than the light guide plate body, wherein the light guide plate has a directivity converting pattern on the face on the light exit side or the opposite face, wherein the directivity converting pattern is for converting a directional expansion in a thickness direction of the light guide plate of the light that has entered the light introducing portion into a directional characteristic that has been inclined to a direction parallel to a planer direction of the light guide plate, wherein the directivity converting pattern is comprised of an arrangement of a plurality of unit patterns of recesses or projections, each of which extends in one direction, and wherein when the light guide plate is viewed from a direction perpendicular to the light exit face, both a first point of intersection at which a first straight line obtained by averaging respective longitudinal axes of the unit patterns which is located within a region which the light which has entered the light guide plate from the light entering face reaches and on one side of the centerline and a second point of intersection at which a second straight line obtained by averaging respective longitudinal axes of the unit patterns which is located within a region which the light which has entered the light guide plate from the light entering face reaches and on the other side of the centerline are located behind a light source center of the point light source.