The surface light source device, a diffusion plate and a liquid crystal display device

A point-light-source type light emitting portion 33 is equipped so as to face a light incident face 37 located at a corner portion of a light guide plate 32. A light diffusion pattern 36 for emitting the light in the light guide plate 32 from a light emission face 45 is equipped on the lower surface of the light guide plate 32. A diffusion prism sheet 35 is disposed on the light emission face 45. A prism sheet 40 comprising prisms each having a concentric shape with the light emitting portion 33 at the center is equipped on the lower surface of the diffusion prism sheet 35, and an uneven diffusion plate 39 is equipped on the upper surface of the diffusion prism sheet 35. Light emitted from the light emission face 45 of the light guide plate 32 along the light emission face 45 is deflected in the direction perpendicular to the light guide plate 32 by the prism sheet 40, and the angle of beam spread of the light is spread by the uneven diffusion plate 39.