| 摘要 |
A surface light source unit comprising a primary light source (1), a light guide (3) for guiding light emitted therefrom, and a light polarization element (4) disposed on the light exit surface (33) thereof, as a surface light source unit in which a luminance unevenness, in an area near a light guide light entry end surface, caused by the thinning of a light guide is hardly recognized visually and little specific light exit is observed in an oblique direction near the light entry end surface. The light guide light entry end surface (31) is specified such that a light-guide-thickness-direction average inclined angle obtained based on measurement by a ultra-depth shape measuring microscope is 3° through 12°, the presence proportion of components having an inclined angle of at least 20° in an inclined angle frequency distribution up to 40%, a light-guide- thickness-direction center line average roughness Ra 0.2 mum through 0.4 mum, and a light-guide-thickness-direction ten-point average roughness Rz 0.7 mum through 2.0 mum.
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