| 摘要 |
A light diffusing sheet exhibiting a high uniformity of luminance and a high average luminance when assembled in a backlight unit of direct under light type and a backlight unit including this unit are provided. The light diffusing sheet of light-transmitting resin comprises a sheet upper surface serving as a light exiting surface and a sheet lower surface serving as a light entering surface. Small recessed parts having an inverted polygonal pyramid shape, inverted truncated polygonal pyramid shape, inverted cone shape, or inverted truncated cone shape or small projecting parts having a polygonal pyramid shape, truncated polygonal pyramid shape, cone shape, or truncated cone shape are arrayed in and on the sheet upper and lower surfaces. The angle of inclination of the slope or ridge of the small recessed or projecting parts in or on the sheet upper surface with respect to the horizontal surface is larger than that in or on the sheet lower surface with respect to the horizontal surface. Thus, the average luminance and uniformity are improved. The backlight unit has such a light diffusing sheet above linear light sources arranged parallel in the vertical or lateral direction.
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