Fabrication of linear Fresnel lens using UV embossing and a micromachined roller mold

Abstract

Roll-to-roll embossing is able to produce functional optical films with high throughput and lower cost, compared to other conventional manufacturing technologies such like injection molding. In roll-to-roll ultraviolet (UV) embossing, the functional microstructures on an optical film are directly replicated from a high-precision roller mold; the roller mold requires strict control of profile accuracy and optical surface quality which have to be achieved using ultra-precision machining technology. In this study, optical films with linear Fresnel lens array have been developed by using ultra-precision diamond tuning for mold fabrication and roll-to-roll UV embossing for transferring the features from mold to the flexible plastic substrates. The roller mould for making Fresnel lens array was designed in such a way that one Fresnel lens was composed of 166 tiny prisms and all prisms have an equal-feature-height of 0.1 mm, resulting in a focal length of 82.5 mm. With the optimized roll-to-roll UV embossing process, the Fresnel lens film produced in large area demonstrated strong light concentration effect on a solar simulation system, with light intensity increased by more than 6 times.