Design and fabrication compound diffuser film with LIGA-like process

Integrated microlens array (MLA) on an optical film provides interesting application for various fields. In this study, a new type film is developed, called compound diffuser films. Two MLAs on double-side of the film is its feature. Another feature is the shape of the microlens, which is polygonal shape and gapless, i.e. 100% fill-factor. And the compound film can supply functions of diffusing light and enhancing brightness. To obtain the optimal effects of the film, Taguchi method with optical simulation is utilized to design and analyze. Processes of compound films belong to Lithographie Galvanoformung Abformung (LIGA)-like, including lithography, reflow, sputtering, electroplating and replication processes. Among these processes, nickel–cobalt (NiCo) alloy electroplating is a key step to fabricate an accurate and strong template with gapless MLAs, as the first mold. Then, a flexible mold of polydimethylsiloxane (PDMS) is replicated from the first mold, as the secondary mold. Then, the film is manufactured by ultraviolet (UV)-cured method with the secondary mold. The processes have advantages of fast, accuracy and mass production. Finally, this film is measured and analyzed its data. The results of measurement and simulation such as the average intensity and the S/N ratios are compared. They show good agreement with each other.