| 摘要 |
PROBLEM TO BE SOLVED: To obviate the degradation in luminance in the case where at least one prism sheet is used, and to obtain high-luminance illumination by setting the vertex of a triangular constituting the groove of the prism sheet at a specific range. SOLUTION: The prism sheets 6, 7 are constituted by arranging many micro- triangular prisms in parallel. Both of the prism surfaces (the surfaces having the grooves) exist on the liquid crystal panel 30 side. The groove of the prism sheet 6 and the groove of the prism sheet 7 are so arranged as to intersect orthogonally with each other. The extension direction of the groove of the prism sheet 6 on a light transmission plate 1 side is arranged to intersect orthogonally with the axial direction of a lamp 21 and the extension direction of the groove of the prism sheet 7 on the liquid crystal panel 30 side is arranged in parallel with the axial direction of the lamp 21. In these prism sheets, plural prisms having triangular shape are formed continuously on the one surface of a transparent resin plate consisting of an acrylic resin, etc. The vertexθof the triangular shape is 97 to 98 deg.. The visual field angle is narrowed and the visibility is improved by setting the vertex to have such triangular shape. |
