| 摘要 |
A surface light source device of side light type includes a primary light source, a reflection sheet, a light scattering guide plate, and a prism sheet. The primary light source comprises a fluorescent lamp and a reflector to supply illumination light toward an incidence surface of the light scattering guide plate. The light scattering guide plate has an emission surface and a back surface, with the prism sheet being disposed along the emission surface. On the emission surface and/or the back surface, a great number of grooves running generally perpendicular to the incidence surface within a range of distance W1 and/or W2 from an upper edge EU and/or a lower edge EL. These grooves provide a corrugate shape in a cross section parallel to the incidence surface. Depth of corrugate shape gradually becomes shallower as getting away from the incidence surface. Illumination light illuminating the edges EU and EL is prevented from being excessively emitted from a specific linear region of the emission surface, with the result that bright line (reflective appearance) is prevented. Such grooves may be formed in the vicinity of the edge where the side surface and the major surfaces intersect. A light control surface may be formed on the full surface of the emission surface or the back surface.
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