| 摘要 |
A back light unit is provided to form pitches between prism patterns differently in a prism sheet and to form the height of prism patterns differently. A prism sheet(402) includes a prism base(500) and prism patterns(502). The prism base supports the prism patterns. The prism patterns have a mountain shape and are formed on a virtual curve(510) with a constant pattern. At least one among the vertex angles of the prism patterns is different from other vertex angles. When the vertex angle of at least one prism pattern is bisected with the normal line of the prism base as the reference, the bisected vertex angles have an equal angle. The pitch between the first prism patterns has the value of the range of 5 to 10 micrometer. The vertex angles of the first prism patterns have the angle of the range of 80 to 120 degrees. Diffusion portions with a semicircle shape are formed on the second surface of the prism base. |
