| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a backlight which can easily and surely realize an improvement in incident light unevenness near a light source which is a weak point of a backlight using a diffraction type condensing sheet which can attain a high luminance. <P>SOLUTION: The backlight is composed of at lease one light source 1, a diffraction lattice type condensing sheet 21, and a light guide plate 2. The diffraction lattice type condensing sheet 21 has a light incident surface and a light emitting surface, and the light incident surface has lattices of sawtooth cross-sections in parallel with each other, and an angle α<SB>F</SB>between a normal of an inclined surface of the one of the lattices and a normal of an upper surface of the sheet is 70° or more and 89.5° or less, and an angle α<SB>B</SB>between a normal of an inclined surface of the other and a normal of the upper surface of the sheet is θ<SB>i</SB>/2.69-5≤78-α<SB>B</SB>≤θ<SB>i</SB>/2.69+5 against an angle θ<SB>i</SB>between the incident light and the normal. <P>COPYRIGHT: (C)2009,JPO&INPIT |
