Silicon-processed plastic micropyramids for brightness enhancement applications

A combination of silicon anisotropic etch and mechanical hot embossing techniques is used to demonstrate the feasibility of manufacturing plastic micropyramids. These micropyramids have the desirable optical characteristics to enhance the brightness of LCD (liquid crystal displays) in battery-powered laptop computers, personal TVs and camcorders. Silicon mold inserts, 4-inch in diameter, are first micromachined and used directly in the micro hot embossing process by applying plastic sheets made of polymethyl methacrylate (PMMA) or polyvinyl chloride (PVC). Micropyramids which have base widths of 30 mu m, heights of 21 mu m and apex angles of 70 degrees are hot embossed on the surface of plastic sheets. The fabricated plastic films are tested optically and the results show that up to 20% brightness enhancement within the front viewing angles of +/-35 degrees have been achieved. An optical model has been established to simulate the brightness enhancement effects and it is concluded that the optimal pyramid angle for the brightness enhancement application is 90 degrees.