Patent ID: 7517127

Claim:
A light guide plate comprising: an emission face provided by a first major face; a back face provided by a second major face opposite to said emission face; a side peripheral face giving a bridge between said emission face and said back face; at least one incidence face provided by a part of said side peripheral face, being supplied with primary light from a primary light source disposed opposite to said incidence face, said emission face comprising: an inclined surface which is not parallel with the rest of said emission face and extends at least in the vicinity of said incidence face, and an effective light emitting area which includes first and second regions disposed at either sides of an optical axis of said primary light, and said inclined surface is sloped downwards in a direction crossing said optical axis so that said light guide plate decreases in thickness as said inclined surface is sloped downwards away in parallel with said incidence face from a part of said side peripheral face corresponding to a larger one of said first and second regions, wherein each of said emission face and said back face is shaped like a rectangle having a pair of long sides and a pair of short sides, said incidence face is formed across a thickness of said light guide plate at least one corner portion as to extend obliquely with respect to each of said one of said long sides and said one of said short sides.