Patent ID: 6196691
Filing Date: 2001-03-06
Classification: G02B

Abstract:
A light guide plate comprising:a transparent plate; anddiffraction gratings provided on both rear and front surfaces of the plate and diffracting light incident from one or more point light sources at at least one end face of the plate; whereina ratio of grating part width/non-grating part width in a unit width, or cross-sectional shape, of the diffraction grating of the rear surface is varied, andthe diffraction grating of the front surface is provided perpendicularly to the diffraction grating of the rear surface, while grating constant of the grating on the front surface is set to a fixed value smaller than a mean grating constant of the diffraction grating on the rear surface or the cross-sectional shape of the diffraction grating on the front surface is set to such a specified shape that high-order diffracted light is diffracted at high efficiency, wherebyuniform, high brightness at the front surface of the light guide plate can be obtained.