Surface light source device.

摘要

A surface light source device includes a light guiding plate which is transparent, a line light source provided on one side face of the light guiding plate, a side face reflection layer provided on the other side of the light guiding plate, a light diffusion/transmission section provided on a back face of the light guiding plate, a ratio of an area of the light diffusion/transmission section to a whole area of the back face of the light guiding plate gradually increasing with a distance increasing in a region from a side face on a light source side of the light guiding plate to a position at which a surface emission luminance of the light guiding plate is lowest, and being constant in a region from the position to a side face on a side face reflection layer side of the light guiding plate, and a back face reflection layer which is white and provided on the back face of the light guiding plate. <IMAGE>