LIGHT DIFFUSING PLATE USED FOR POINT LIGHT SOURCES, AND DIRECT-LIGHTING POINT-LIGHT-SOURCE BACKLIGHT DEVICE

摘要

Provided is a light diffusing plate in a direct-lighting point-light-source backlight using point light sources, the light diffusing plate making it possible to, without use of a number of optical films, compatibly achieve excellent luminance, luminance uniformity (in frontal and diagonal view fields) and color unevenness characteristic with the thickness of the backlight set as desired and with the reduced number of point light sources. Specifically, provided is a light diffusing plate used for point light sources, which has a plurality of convex portions formed on a surface thereof, wherein: each of the convex portions has a substantially triangular-pyramid shape having a triangular bottom; and the slope angle (?) of each side of the substantially triangular-pyramid shape with respect to the bottom, and the refraction index (A) of a material forming the convex portions satisfy the following expressions (1) and (2): (1) ... ? = -40A° + 115.2° (2) ... ? = 25A° + 22.25°