A new fabrication method for an asymmetric microlens array light control film using inclined exposure and an incomplete thermal reflow process

This study presents a novel fabrication method for asymmetric microlens arrays for light control films that increase the efficiency of liquid crystal displays used to collect lateral light sources and improve the brightness within the angle of view. Initially, the pattern allows exposure through the placement of a photoresist-coated substrate on an inclined fixture. An inclined photoresist column array with a round cross section is constructed using a photolithography technique. During the incomplete thermal reflow processing, only the surface part of the photoresist column reaches the glass transition temperature (T-g) and is transformed from a glassy state into a rubbery state. In order to minimize the structural surface energy and reduce the surface area, the surface of the inclined photoresist column forms the shape of a lens. With proper control of the thermal reflow temperature and processing time, the photoresist at the base maintains its original inclination and glassy state, because it does not reach the glass transition temperature. The experimental results show that the inclined exposure from different angles precisely controls the declination angle of the inclined photoresist column. Asymmetrical microlens arrays with tilt angle larger than 33 degrees can be fabricated using the incomplete thermal reflow method.