Patent ID: 7826703
Filing Date: 2010-11-02
Classification: G02B,G02F,Y10S

Abstract:
1. A planar lighting device comprising: a first light source and a second light source disposed a given distance apart from each other; and a light guide plate disposed between said first light source and said second light source, wherein said light guide plate comprises a light exit plane, a first light entrance plane facing said first light source and containing one side of said light exit plane, a second light entrance plane facing said second light source and containing an opposite side to said one side and a rear plane, and grows thicker from said first light entrance plane and said second light entrance plane toward a center, wherein the rear plane of said light guide plate has a first inclined plane and a second inclined plane located on the opposite side from the light exit plane and inclined a given angle respectively, and a joint formed into a curved shape between said first inclined plane and said second inclined plane, and wherein said light guide plate contains scattering particles to reduce a degree of brightness unevenness for scattering light entering through said first and said second light entrance planes of said light guide plate inside thereof and propagating nearly parallel to said light exit plane inside thereof, said scattering particles satisfying an expression (1) below: (where Φ denotes a scattering cross section of said scattering particles, L G denotes a half of a length of said light guide plate in a direction in which light is admitted, N p denotes a density of said scattering particles, and K c denotes a compensation coefficient, K c being not smaller than 0.005 and not greater than 0.1).