Patent ID: 7529461

Claim:
In a light guide plate comprising a light incidence surface, a light reflection surface, and a light emission surface, said light incidence surface being arranged to receive light emitted from an elongated light source having a lengthwise direction, said light reflection surface being formed with a plurality of light guiding ribs which are elongate raised projections each having a V-shaped cross-section and having opposite inclined sides and extending in a direction parallel to said lengthwise direction of said light source, said light emission surface being opposite to said light reflection surface and adjacent to said light incidence surface, said light emission surface being formed with a plurality of light guiding ribs which are elongate raised projections each having a V-shaped cross-section and having opposite inclined sides and extending in a direction perpendicular to said lengthwise direction of said light source, the improvement wherein a central one of said light guiding ribs of said light emission surface has a regular V-shape cross-section and other ones of said light guiding ribs of said light emission surface are endwise offset from said central one and have a long inclined side and a short inclined side with said short side facing said central one and said long side facing a lengthwise end of said light emission surface, said long side and said short side respectively forming inclined angles θ 1 and θ 2 with respect to said light emission surface and said light-guiding ribs being arranged in such a way that said included angle θ 1 is smaller than said included angle θ 2 and said included angle θ 1 gets smaller with distance thereof with respect to said central rib increases.