Planar light source device and liquid crystal display apparatus

Abstract

A planar light source device contains a light source (1); a light guide (2) which has a light incident face (21) on at least one side end surface thereof which confronts the light source (1), and a light emitting face (23) on one of two principal surfaces (23, 24) thereof; and a light direction varying sheet (4) which is disposed on the light emitting face (23) of the light guide (2), wherein a back surface (24) of the light guide (2) opposing to the light emitting face (21) is formed as a prism surface which comprises a plurality of elongated prisms each having substantially triangular cross section of a vertical angle within a range of 60 to 80° or 125 to 150° so as to extend in parallel to each other and in perpendicular to the light incident face (21), and a major part of the light emtting face (23) is formed as an uneven surface having an average slant angle of 0.3 to 30°.

Dependencies are inferred from the claim text.