Surface light source device, and liquid crystal display device, sign display apparatus and traffic sign display apparatus using the surface light source device

Abstract

A surface light source device, comprising a light source (2); a light conductor (1) which has a light incident face (11) on at least one side end surface thereof which confronts the light source (2), and a light emitting face (12) on one surface thereof which is substantially perpendicular to the light incident face (11); and a light angle varying sheet (3) which is disposed at a side of the light emitting face (12) of the light conductor (1), wherein at least one of the light emitting face (12) and a back surface (13) of the light conductor (1) comprises a minute structure having an average slant angle of 0.5 to 7.5 degrees. The light angle varying sheet (3) may comprise a prism sheet having a plurality of prisms (31) which are formed parallel to one another on at least one surface thereof. The minute structure may comprise a roughened surface which includes a plurality of fine convex members each having a substantially spherical surface or a plurality of prism arrays having slant surfaces which extend parallel to said light incident face (11) and which have an average slant angle of 0.5 to 7.5 degrees.

Dependencies are inferred from the claim text.