Design and fabrication of double-sided optical film for OLED lighting

Design and fabrication of optical films to increase visual brightness of OLED (Organic Light-Emitting Diode) lighting units are presented in this paper. This study explores a new fabrication process combining precision machining, photolithography, and micro forming techniques to make a double-sided optical film. One side of the optical film is made of micro triangular-pyramidal array (MTPA), and the other side is micro gapless hexagonal microlens array (GHMA). First, Taguchi Method is applied to determine the optimal microstructure configuration by the assistance of the commercial optical software, FRED. Second, tungsten (W) mold of MTPA as the first mold is manufactured by precision machining including optical projection grinding, lapping, and polishing processes. Nickel–cobalt (NiCo) mold of GHMA as the first mold of the other side is fabricated by using LIGA (Lithographie Galvanoformung Abformung)-like process. To obtain inverse molds, poly dimethylsiloxane (PDMS) is used to replicate W and Ni–Co molds, which are served as the secondary molds for two sides, respectively. With these molds, UV (ultraviolet) curable resin was used to make double-sided optical film. Then the optical film was packaged on OLED unit to measure its optical properties by PR 650 equipment. The result shows that both brightness and uniformity can be improved by using this film.