SURFACE LIGHT SOURCE DEVICE AND PRISM SHEET

摘要

A surface light source device being higher in luminance than conventional surface light sources and high in front-direction light condensing feature. The surface light source device, wherein the angle ?F<SUB>1</SUB> of the oblique side on the light source side of the prism of a first prism sheet disposed opposite to the outgoing surface of a light guide satisfies the expression (1), the angle ?B<SUB>1</SUB> of the oblique side on the opposite side of the light source satisfies the expression (2), the angle ?F<SUB>i</SUB> of the oblique side on the light source side of the prism of the i-th prism sheet (i is an integer of at least 2) disposed on the light outgoing side of the first prism sheet satisfies the expression (3), and the angle ?B<SUB>i</SUB> of the oblique side on the opposite side of the light source satisfies the expression (4). ?F<SUB>1</SUB> = f<SUB>2</SUB> ---(1) (f<SUB>2</SUB>=sin<SUP>-1</SUP>(n<SUB>1</SUB>