| CPC G02B 6/0051 (2013.01) [G02B 6/0053 (2013.01)] | 20 Claims |

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11. A backlight unit comprising:
an edge type light source; and
an optical film disposed over the light source further comprising:
a first optical sheet including a first base portion;
a pyramid pattern layer including a plurality of pyramid patterns formed on a first surface of the first base portion and a first side of a pyramid base of the pyramid pattern arranged in a pyramid direction; and
a first prism pattern layer including a plurality of first prism patterns formed on a second surface of the first base portion and an edge of the first prism pattern arranged in a first prism direction,
wherein the optical film satisfies either Equation 5 or Equation 6:
![]() wherein pi1 is a first pitch corresponding to a length of the first side of the pyramid base of the pyramid pattern; pi1-1 is a first prime pitch corresponding to a diagonal length of the pyramid base of the pyramid pattern; pi2 is a second pitch corresponding to a base length of the first prism pattern; and n is a natural number.
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