Abstract: 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 one 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 on the light exit 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.

Abstract: A surface light source device comprises a light emitting section (11) made of a single spot light source, a light guide plate (12), a reflective surface (13) provided on the back side of the light guide plate, and a prism pattern (15). On the light emitting surface side of the light guide plate (12), there is provided a directional light scattering film (14) consisting of at least two phases having different refractive indexes and scattering light when transmitting it. One phase of a larger refractive index includes a plenty of areas having a columnar structure extending in the thickness direction of a film and arranged to be perpendicular to a normal to the film, and exhibiting a maximum scattering angle of 10-40°.