Patent ID: 7077556

Claim:
A lighting device comprising: a light guide plate; a light guide disposed along a side end surface of the light guide plate; and a light emitting device disposed on an end surface of the light guide, wherein a plurality of wedge-shaped grooves seen in cross section extending in a thickness direction of the light guide is formed and arranged in a backside of the light guide on an opposite side of the light guide plate, a metal reflective film, in a distribution of a pitch between the grooves with respect to a distance from the end surface disposed with the light emitting device to groove, the pitch between the grooves is constant or linearly varied with respect to the distance from the end surface disposed with the light emitting device to the groove, a depth of the groove is formed more deeply as the groove is positioned more distal from the end surface, in a distribution of the depth of the groove with respect to the distance from the end surface disposed with the light emitting device to the groove, there is a first area where the depth of the groove is constant or linearly increased with respect to the distance from the end surface to the groove, and a second area formed more distal from the light emitting device than the first area in which an increasing rate of the depth of the groove with respect to the distance from the end surface is greater than that in the first area, and in two grooves adjacent to each other formed in at least one of the first and second area, a ratio of the depth of the groove formed on a side apart from the end surface to the depth of the other groove ranges from 1 to 1.005.