Fabrication of microlens array diffuser films with controllable haze distribution by combination of breath figures and replica molding methods

This work demonstrates the fabrication of a simple, low-cost microlens array (MLA) diffuser film with controllable haze distribution (diffusion effect) by a combination of breath figures (BFs) and microreplica molding methods. Polystyrene (PS) molds obtained by BFs method contain concave, hexagonal packed air holes formed by the condensation of water vapor on cooling surfaces in a chamber in which relevant influence factors can be controlled. The sizes of the air holes in the BFs PS molds can be controlled by varying such factors as chamber temperature, chamber relative humidity, substrate temperature and others. The temperature distribution on the substrate affects the distribution of diameters of the air holes formed in a BFs PS mold. Convex PDMS (poly-dimethylsiloxane) MLAs were obtained by molding from the BFs PS molds. The focal lengths of MLAs were measured and compared with theoretical values. The diffusion effect of the diffuser films with MLAs of diameters 6 mu m and 3 mu m were compared. The results indicate that an MLA with a smaller diameter has a larger diffusion effect. c 2008 Optical Society of America