Fabrication of an Aspherical Microlens for OLED with Modified Etching Process

Study on using a process which was combined LIGA (Lithographie Galvanoformung Abformung) with etching to manufacture an optical film of an aspherical microlens array (A-MLA), which can improve the extraction efficiency of an OLED (Organic Light-Emitting Diode). The extraction efficiency of a current OLED is not high due to its total internal reflection, and the luminance is also lower because of the low extraction efficiency. How to increase the extraction efficiency is a valuable topic to discuss. This study analyzes the manufacturing and design parameters of A-MLAs such as diameter of a microlens, dry etching parameters and electroforming rates. The experimental results indicate that the variation of the diameter is about 5% after the thermal reflow and dry etching process. Electroforming process is used to make a metal mold as the first mold after PDMS (Polydimethylsiloxane) mold is replicated called the secondary mold. In addition, it has an additional effect to refine the existing defects on photoresist surface. From the measured data of the luminance of the optical film with A-MLAs, they show that the luminance of OLEDs is enhanced more than that of common spherical-microlens array.