Surface light source device.

摘要

A surface light source device having light sources (2) provided along all four side edges of a light-conducting member (1). A light guide (1) has a diffusion plate (3) on its front surface and a reflection surface (4) on its back surface. The back surface of the light-conducting member (1) has a pattern consisting of tiny rough surface areas (5). The pattern is so formed that in a direction (Y-Y) of connecting a pair of two opposed sides of the light-conducting member, the density of the rough surface areas is the largest in the center portion, but gradually decreasing toward the two opposed side edges and reaching the smallest density on the two opposed side edges. Thus, the surface light source device increases the brightness and provides a uniform distribution of brightness. <IMAGE>