Patent ID: 6734929
Filing Date: 2004-05-11
Classification: G02B

Abstract:
An illumination device comprising:a light source; and a light guide plate for receiving light emitted from the light source through one side end face thereof as a light incident surface, and for outputting light traveling inside the light guide plate through one major surface thereof, the major surface of the light guide plate being formed in stripe form in a plan view with a plurality of prism grooves each of which is formed by a slight slope and a steep slope having an inclination angle larger than that of the slight slope, the inclination angles of the slight slope and the steep slope being in ranges of 1Â° to 10Â° and 41Â° to 45Â°, respectively, widths of the steep slopes increasing with increasing position away from the light incident surface such that a ratio of the width of the steep slope at a position farthest from the light incident surface to the width of the steep slope at a position closest to the light incident surface is 1.1 to 1.5.