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°.

Abstract: Disclosed herein is a gear structure which comprises a sectoral base member of metal plate; and an arcuate flange portion integrally formed on an arcuate flange portion integrally formed on an arcuate peripheral portion of the sectoral base member. The arcuate flange portion is formed on an outer surface of thereof with forged teeth.