| 摘要 |
A subject for the invention is to provide: a light diffusing sheet which, when incorporated in a direct-backlight unit, brings about high uniformity of luminance and a high average luminance; and a backlight unit having the sheet incorporated therein. The light diffusing sheet of the invention is made of a light-transmitting resin and has a sheet upper surface serving as a light emission side and a sheet lower surface serving as a light entrance side. It has a constitution in which small recesses having a shape which is any of the shapes of an inverted polyangular pyramid, inverted truncated polyangular pyramid, inverted cone, and inverted truncated cone or small protrusions having a shape which is any of the shapes of a polyangular pyramid, truncated polyangular pyramid, cone, and truncated cone have been formed in order in the sheet upper surface and sheet lower surface, and the inclined angle between the horizontal plane and the inclined face or ridgeline of each small recess or small protrusion in the sheet upper surface is larger than the inclined angle between the horizontal plane and the inclined face or ridgeline of each small recess or small protrusion in the sheet lower surface. This constitution improves average luminance and uniformity of luminance. The backlight unit of the invention has a constitution in which the light diffusing sheet has been disposed over linear light sources disposed in parallel in a lengthwise or crosswise direction.
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