| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a substrate film for optical sheet which extraordinarily improves the efficiency of using light and far accelerates the improvement of luminance, to provide an optical sheet having the substrate film for optical sheet, and to provide a backlight unit having the optical sheet. <P>SOLUTION: The substrate film for optical sheet made of transparent resin which is formed in a rectangle shape has an optically anisotropy and has an absolute value of angle in the crystal axis direction with respect to the width direction of π/16 to 3π/16. A fast axis direction is preferably set as the crystal axis direction. Therein, the substrate film for optical sheet can convert an exit light polarization component from a light guide plate, etc. to a transmission axis direction of a polarizing plate, etc. and has such a retardation value that the average transmission light intensity I<SB>A</SB>is 0.75 or more. The retardation value preferably falls into the range of 140 nm to 390 nm. Polyethylene terephthalate or polycarbonate is preferably used as the transparent resin. The optical sheet is provided with the substrate film for optical sheet and an optical layer. <P>COPYRIGHT: (C)2007,JPO&INPIT |
