| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a diffusion plate capable of reducing radial luminance unevenness generated in a surface light source device using point light sources. <P>SOLUTION: A prism diffusion sheet 52 has a convex and concave diffusion plate 53 formed on the front surface thereof and a prism sheet 40 formed on the rear surface thereof. The convex and concave diffusion plate 53 diffuses light transmitted by the prism sheet 40 only in a circumferential direction around a central point corresponding to light emission part 33. The convex and concave diffusion plate 53 is divided into concentric annular regions 54a and 54b having a width Λr around the light emission part 33 as a center, sine-wave-shaped convex and concave patterns 55 are formed in the regions 54a and 54b along a direction θ in a period Λθ satisfactorily shorter than the width Λr of the regions, and the periods Λθ of the adjacent regions 54a and 54b are different from each other by a little amount. <P>COPYRIGHT: (C)2008,JPO&INPIT |
