Fabrication and design of various dimensions of multi-step ashperical microlens arrays for OLED package

An optical film with aspherical microlens array (A-MLA) by using multi-step lithography process for an OLED (Organic Light-Emitting Diode) package is fabricated, by which method the luminance of OLEDs can be enhanced. The method of design and fabrication of an A-MLA is explored in this study. In the design process, various parameters of an A-MLA such as curved profiles, layout template and dimensions of microlens are analyzed and characterized. Curved profiles include hyperbola, parabola, ellipse and sphere; and layout templates include square, hexagon, triangle and tangential circle. The profile of the A-MLA was determined by using a commercial optical simulation software, FRED. Based on the simulated result, a film with an A-MLA was fabricated using the LIGA-like (Lithographie Galvanoformung Abformung, LIGA) process, including lithography, sputtering, micro-molding with PDMS (Polydimethylsiloxane) and UV (Ultraviolet)-cured technology. The major challenge to this process is to use JSR-126N negative thick photoresist to manufacture an approximate A-MLA optical film with multi-step lithography method. Finally, the films with A-MLAs are attached to an OLED to measure their optical-electric properties. The effectsof A-MLA optical films on OLED luminance are analyzed. In addition, the measured results are compared with simulated ones. They show good agreement with each other.

Research highlights
► The aspherical curved profile of the microlens array can improve the luminance of the OLED.
► An A-MLA with various profiles can substantially enhance intensity up to about 36%.
► The performance of a multi-level A-MLA has good agreement with simulation result.
► The view angles of an OLED can be increased through an A-MLA.