MOLD FOR MOLDING RUGGED SHAPE, OPTICAL SHEET PRODUCED BY USING THE MOLD, BACKLIGHT UNIT AND DISPLAY APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide an optical sheet produced to have uniform thickness by adjusting an in-plane pressure balance when the optical sheet is molded.

SOLUTION: The mold 48 for molding a rugged shape is used for molding the rugged shape on one surface of a light-transmissive base material. Patterns of concave parts 50 for prism lenses, each of which is used for forming the prism lens and extended to one direction, are formed in parallel on the outside surface of a mold cylinder 49. Pressure adjustment concave parts 51 for forming a convex lens having an almost hemispherical shape are formed at predetermined intervals while being superposed on the concave parts 50 for prism lenses. The pressure adjustment concave part 51 has the depth/width which are deeper/wider than the depth/width of the concave part 50 for the prism lens. When extrusion molding is performed by using the mold 48 for molding the rugged shape, the pressure irregularity when the molding is performed is absorbed by an optical sheet material to be pressed to the pressure adjustment concave part 51 to adjust the pressure balance and form the optical sheet having uniform thickness and refractive index of the optical sheet material, so that the unevenness or deflection of the optical sheet is made invisible.

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