LIGHT GUIDE PLATE AND ITS MANUFACTURE, AND SURFACE LIGHT SOURCE DEVICE

摘要

PURPOSE: To lower the manufacture cost of a light guide plate and surface light source device and to form the lighting domain of a large area with high illuminance and uniformity through a sand blast processing. CONSTITUTION: A gradation pattern 12 is formed on the surface 11M of a transparent substrate through a sand blast processing. The gradation pattern 12 is constituted by dispersing an infinite number of recessed places 12A formed by cutting the surface structure of the surface 11M. The dispersion density of recessed places 12A is low nearby flanks 11A and 11B on which primary illumination light is made incident and high at the center part. The intervals of the recessed places 12A are so determined that the original smooth surface state is maintained, so that light guide performance of the light guide plate 11 is secured. An intentional bright and dark pattern can be outputted by adjusting the gradation pattern 12.