Patent ID: 9116265
Filing Date: 2015-08-25
Classification: G02B,G02F

Abstract:
1. A planar lighting device comprising: a light guide plate that includes a rectangular light exit surface, one or more light incidence surfaces which are each disposed on an end side of the light exit surface and through which light traveling in a direction substantially parallel to the light exit surface enters, a rear surface on an opposite side to the light exit surface, scattering particles dispersed in the light guide plate, and two or more layers overlapping in a direction substantially perpendicular to the light exit surface and having different particle concentrations of the scattering particles, wherein the two or more layers of the light guide plate include a first layer having a particle concentration of the scattering particles represented by Npo and being located on a side closer to the light exit surface, and a second layer having a particle concentration of the scattering particles represented by Npr and being located on a side closer to the rear surface, and wherein thicknesses of the two or more layers in the direction substantially perpendicular to the light exit surface vary individually such that the thickness of the second layer continuously varies so that the thickness of the second layer increases, then decreases, and increases again with increasing distance from the one or more light incidence surfaces in a direction perpendicular to the one or more light incidence surfaces so that a combined particle concentration of the light guide plate has, in a direction perpendicular to one of the one or more light incidence surfaces, a first local maximum value on a side closer to one of the one or more light incidence surfaces and a second local maximum value located at a position more distant from one of the one or more light incidence surfaces than the position of the first local maximum value and being larger than the first local maximum value; one or more light source units, the one light source unit being so disposed as to face one of the one or more light incidence surfaces of the light guide plate; and an optical member unit including a micro-lens film in which a plurality of spherical micro-ball lenses are formed on a film, the optical member unit being disposed on the light exit surface of the light guide plate.