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 µm, heights of 21 µm and apex angles of 70 • 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 • 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 • .

This paper reports a novel and effective method to fabricate microlens arrays on polycarbonate films by hybrid extrusion rolling embossing. The metallic cylinder mold bearing an array of micro-holes is fabricated using photolithography with dry film resist. During the extrusion rolling embossing process, the extruded PC film is immediately pressed against the surface of the roller mold. Under the influence of the rolling pressure and surface tension, an array of convex microlenses is formed. The uniformity and optical properties have been verified. An efficient continuous mass production technique has been demonstrated.

Hot embossed microstructures fabricated by laboratory and commercial environments have been studied. The laboratory process uses silicon with micropyramid patterns as the mold insert. Fine replication by using Polymethyl Methacrylate (PMMA) has been achieved. The commercial process uses electroplated nickel as the mold insert. Polyvinyl Chloride (PVC), which has a lower glass transition point than PMMA, has been used as the raw material. Fabrication results show that the laboratory process, although taking about 2 hours long per run, can successfully replicate microstructures. The commercial process which takes only 1 minute per run may be fine tuned for good replication. Atomic Force Microscope (AFM) has been used to analyze the fabricated microstructures. It is found that the root mean square (r.m.s.) roughness of PMMA is about 4 nm and that of PVC is about 10-15 nm. Defects including voids and bumps on both PMMA and PVC films have been found.

Abstruct-We have successfully demonstrated the feasibility of fabricating three-dimensional microstructures by using a combined silicon mold insert and micro hot embossing process (SMIHE).Anisotropic silicon wet etching process has been used to define microstructures on top of a four inch silicon wafer. The whole wafer is then used as the mold insert in a micro hot pressing machine to duplicate plastic microstructures repeatedly. Fine micro pyramid shape microstructures with base width of 30 pm and height of about 21 pm have been fabricated by this method as a demonstration. They have very smooth surfaces and may be suitable for optical applications. This new process shows promise for achieving high yield, reliable fine micro structures on plastic films.

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