LIGHT GUIDE PLATE, AND PLANAR LIGHTING DEVICE AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME

摘要

The transparent light guide plate 18 includes a rectangular light exit surface 18a, a thick portion 18b positioned at substantially a central portion of the surface, thin edge portions 18c formed in parallel on both sides of the thick portion 18b, a parallel groove 18f accommodating a bar-like light source 12 and being formed at substantially a center of the thick portion 18b and inclined rear portions 18e whose thickness is reduced from the thick portion toward the thin edge portions 18c. An end portion of the groove is narrowed toward the surface symmetrically to a center line of the groove in a sectional shape thereof according to a ratio of a peak value of illuminance or luminance of emitted light at a first portion of the surface corresponding to the groove to an average value thereof at second portions corresponding to the inclined rear portions. The planar lighting device includes the light guide plate 18. The liquid crystal display device (4) includes the planar lighting device.