Planar lighting device

摘要

A simple and inexpensive planar lighting device (10) realizing a high luminance is provided, including: a light guide plate (12) having a pair of opposite light entry faces (12a), a light emitting face (12b) extending perpendicularly to the light entry faces (12a), a plurality of hemispherical surfaces (22a) formed on the light emitting face (12a), and a light non-emitting face (12c) opposite to the light emitting face (12a); a light source (14) disposed to extend along each of the light entry faces (12a); a reflector (16) for reflecting light from the light source (14) toward a respective one of the light entry faces (12a); a reflecting plate (18) disposed to extend along the light non-emitting face (12c) for reflecting light leaking from the light guide plate (18) toward the light guide plate; and a lens sheet (20) disposed to extend along the light emitting face (12a) and formed with a plurality of first ridges (20a) extending parallel with the light entry faces (12a) on a face thereof opposite to the light emitting face (12b), the first ridges (20a) each having a triangular section.