Fabrication of concave microlens array diffuser films with a soft transparent mold of UV-curable polymer

A new lithographic approach for the fabrication of an enticing optical diffuser with concave microlens array (MLA) is reported. A flexible photopolymerizable polymer mold is employed as an intermediate transferring template from nickel stamp and directly adopted to fabricate concave MLA diffuser films. The influence of the parameters (such as diameter, fill factor etc.) of concave MLA is analyzed experimentally and theoretically. The results verify that the optical gain can be reached as high as 53%, which has a similar fascinating diffusion effect compared with that of conventional convex MLA diffuser films. Additionally, it is found that diffusion angle could be manipulated by the profile of the concave elliptical MLA, leading to luminance increase in long axis larger than that in short axis. The approach demonstrated here affords the intriguing opportunity to large scale industrial processing for high-quality diffusers with low manufacturing and materials cost.