Planar illumination device and display device provided with the same

A planar illumination device comprising:

• a light source;
• and
• a light guide member that guides light from the light source,
• wherein the light guide member includes:
• a light guide body that the light from the light source enters;
• and
• a low refractive index layer that is provided on a back surface of the light guide body without intervention of an air layer and that has a lower refractive index than the light guide body,
• in a side of a front surface of the light guide body or in the back surface of the light guide body, a plurality of first reflective portions are provided that gradually reduce an angle of incidence of the light from the light source with respect to the back surface of the light guide body, and
• in a light emitting region of the light guide member, a plurality of second reflective portions that have a function of totally and forwardly reflecting the light from the light source in an interface between a back surface of the light guide member and an air layer are formed over substantially the entire back surface of the light guide member.