The light guide plate, a planar lighting device and a liquid crystal display device using the same

A lightweight thin, more uniform unevenness less from the light emitting surface, in order to provide a light guide plate having a large size which can emit a higher intensity illumination light, the light guide plate, the rectangular light exit surface back of the cross section satisfies the following 10th-order function equation. In the formulas, X is a position from the origin O in a direction parallel to one side of the light guide plate, Y is the position from the origin O in the direction perpendicular to the one side. The planar lighting device comprises a light guide plate, a liquid crystal display device includes the planar illumination device as a backlight unit.