Single-light-source illumination device and liquid crystal display device using the same

An illumination device comprising:

• a light guiding plate;
• an intermediate light guide disposed along two side surfaces of the light guide plate;
• and a light emitting element disposed on the intermediate light guide,
• wherein the light guiding plate includes two mutually opposing surfaces, one serving as an output surface and the other serving as a reflective surface for reflecting light propagating in the light guiding plate, the reflective surface including a plurality of mutually parallel, prismatic grooves, each having a wedge shape in sectional view and extending so as to form an oblique angle with any one of the two side surfaces of the light guiding plate on which the intermediate light guide is disposed, and
• wherein the intermediate light guide comprises two light guiding sections disposed in an L-shaped configuration in plan view and along the two neighboring side surfaces of the light guide plate.

An illumination device comprising:

• a light guiding plate;
• an intermediate light guide disposed along one side surface of the light guiding plate;
• and a light emitting element disposed on a longitudinal end surface of the intermediate light guide,
• wherein the light guiding plate includes two mutually opposing surfaces, one serving as an output surface and the other serving as a reflective surface for reflecting light propagating in the light guiding plate, the reflective surface including a plurality of mutually parallel, prismatic grooves, each having a wedge shape in sectional view and extending so as to form an oblique angle with the one side surface of the light guiding plate on which the intermediate light guide is disposed, and
• wherein the light guiding plate has a reflective film formed on another side surface thereof, lying adjacent to the one side surface thereof on which the intermediate light guide is disposed and lying close to the light emitting element.

A liquid crystal display device comprising:

• an illumination device, the illumination device comprising:
• a light guiding plate;
• an intermediate light guide disposed along one side surface of the light guiding plate;
• and a light emitting element disposed on a longitudinal end surface of the intermediate light guide, wherein the light guiding plate includes two mutually opposing surfaces, one serving as an output surface for outputting light which is emitted from the light emitting element and which is introduced into the light guiding plate via the intermediate light guide, and the other serving as a reflective surface for reflecting light propagating in the light guiding plate and including a plurality of mutually parallel, prismatic grooves, each having a wedge shape in sectional view;
• and
• a liquid crystal display unit disposed so as to oppose the output surface of the light guiding plate,
• wherein the prismatic grooves of the light guiding plate have a pitch P1 in the range (1/2)P0<P1<(3/4)P0 with respect to the pitch P0 of pixels of the liquid crystal display unit.