| 摘要 |
A planar illumination device is provided that enhances the efficiency of use of light and its brightness while suppressing uneven brightness, that reduces an increase in the manufacturing cost and that can reduce the thickness of the planar illumination device. In this backlight device (planar illumination device) (20), in the light emitting surface (23b) of a light guide body (23), a plurality of prisms (23e) that gradually reduce an angle of incidence of light with respect to the back surface (23c) of the light guide body are provided, and, in the back surface (24a) of a low refractive index layer (24), a plurality of prisms (24b) that have the function of forwardly and totally reflecting light from LEDs (21) in an interface between the back surface of the low refractive index layer and an air layer are formed. |
