| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical plate which allows for realizing superior brightness uniformity, or specifically eliminating the darkness right above LED light sources, and reducing thickness and the number of point light sources of direct point light source backlight devices which use point light sources having high light emission intensity in the wide-angle region, and to provide a direct point light source backlight device equipped with the same.SOLUTION: An optical plate has a periodic structure on one surface (surface A) and satisfies a conditional expressions (1) and (2) expressed as: 54%≤Tt_A≤-Tt_B+124%...(1), 48%≤Tt_B≤54%...(2), where Tt_A represents total light transmittance of the optical plate, measured with a JIS K7105 compliant method, when light enters from the surface (surface A) having the periodic structure, and Tt_B represents total light transmittance of the optical plate, measured with a JIS K7105 compliant method, when light enters from a surface (surface B) opposite the surface having the periodic structure. |
