Patent ID: 7884898

Claim:
An optical sheet for a backlight provided on a surface light source in the backlight, comprising: an optical reflection layer having a plurality of through grooves arranged at a prescribed interval; and a plurality of cylindrical lenses each provided at a corresponding through groove, the width of said through groove being narrowed from the upper surface to the lower surface of said optical reflection layer, said cylindrical lens being filled in said through groove and having a cylindrical surface on the upper surface side of said optical reflection layer, wherein the refractive index of said cylindrical lens is n, the radius of curvature of said cylindrical surface is r, and the height h from the top of said cylindrical lens to the opening of the through groove formed at the lower surface of said optical reflection layer satisfies the following Expression (1): nr /( n− 1)×0.8 ≦h≦nr ( n− 1)×1.3 (1).