Surface light source unit, surface illumination device, and liquid crystal display device

Abstract

Provided is a surface light source unit which has a high-directivity point light source and has a decreased thickness in the in the direction in which light is irradiated from said point light source. Also provided are a surface illumination device and a liquid crystal display device. A plurality of small chambers (to) having an opening on the top are formed in a housing () from side plates (to) that have a predetermined height and partition plates () which partition the inside of the housing (). Each small chamber is provided with a point light source () on the bottom part. The opening of each small chamber (to) is covered with a light transmitting/reflecting plate (to) which has a surface area (S), and comprises: a central reflecting section that has a surface area (ΔS), exhibits high reflectance and low transmittance, and is positioned directly above the point light source (); and an outer reflecting section that surrounds the central reflecting section and is configured so that the light transmittance increases at distances further from the central reflecting section. The surface area (ΔS) and surface area (S) of each light transmitting/reflecting plate (to) are set in a manner such that the ratio ΔS/S is a predetermined value.