PLANAR ILLUMINATION DEVICE AND DISPLAY DEVICE PROVIDED WITH THE SAME

摘要

Provided is a planar illumination device wherein the use efficiency and the brightness of light are improved while suppressing the unevenness of the brightness; the increase of the manufacturing cost is suppressed; and the thickness of the planar illumination device can be reduced. In the planar illumination device (backlight device) (20), a plurality of prisms which gradually reduce the incident angle of light with respect to the back surface (23c) of the light guiding element are provided on a light emitting surface (23b) of a light guiding element (23). A plurality of prisms (24b) are formed on a back surface (24a) of a low refractive index layer (24). The prisms (24b) reflect all of the light emitted from a LED (21) at the interface between the back face of the low refractive index layer and an air layer.