| 摘要 |
A surface light source comprising a light emitting part (11) consisting of a single spot light source, and a light guide plate (12), wherein a reflection plane (13) is provided on the back side of the light guide plate and a prism pattern (15) is also provided. A directional light diffusion film (14) consisting of at least two light scattering/transmitting phases having different refractive indexes, where on phase having a larger refractive index includes a large number of regions having a columnar structure extending in the thickness direction of the film and the columnar structure is inclining against the normal direction of the film at an angle of 5-60°, is arranged in the light exist surface side of the light guide plate (12) such that the scattering direction of the directional light diffusion film becomes the direction of uneven luminance. Unevenness of luminance becomes inconspicuous especially when it is observed from an oblique direction and highly efficient brighter irradiation of light is ensured in the front direction of a screen.
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