Patent Number: 6,332,691

Title: 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.

Inventors: Oda; Masaharu (Kanagawa, JP), Chiba; Issei (Kanagawa, JP), Hayashi; Yasuko (Kanagawa, JP)

Assignee: Mitsubishi Rayon Co., Ltd.

International Classification: F21V 8/00 (20060101); G02B 6/00 (20060101); F21V 008/00 ()

Expiration Date: 12/25/2018