Patent ID: 7815357

Claim:
A light guide for use in surface light source devices, which is shaped like a plate, designed to guide light emitted from a plurality of spot-like primary light sources, comprising: a light-incoming end face for receiving the light from the primary light sources; a light-outgoing face for emitting the light guided in the light guide; a rear surface located opposite to the light-outgoing face; a low light diffusion region having an average inclination angle; and a plurality of high light diffusion regions, wherein the low light diffusion region and the high light diffusion regions are formed on at least one of the light-outgoing face and the rear surface, so that the high light diffusion regions are isolated from one another with the low light diffusion region interposed therebetween, wherein the high light diffusion regions are disposed in the vicinity of the light-incoming end face so as to extend substantially in a direction of the directivity of the light introduced into the light guide within a plane extending along the light-outgoing face, and have a larger average inclination angle than that of the low light diffusion region, and wherein the high light diffusion regions are provided corresponding to the respective primary light sources, and each high light diffusion region and the corresponding primary light source are positioned on a line extending in the direction of the directivity regarding the corresponding primary light source.