Patent ID: 7722790

Claim:
A process for making a transparent polymeric film bearing on the light exit surface of the film an array of close-packed convex elliptical microlenses having a distribution of sizes and oriented in one direction comprising the steps of (a) providing a first structured polymeric film with hemispherical micro-cavities (b) heating the first structured polymeric film to a temperature above the glass transition temperature (Tg) of the polymer composing the film; (c) stretching the first structured polymeric film to form micro-cavities of the desired asymmetric shape; (d) cooling the first structured polymeric film below Tg while the film is maintained in the stretched configuration to lock in the asymmetric shape of the micro-cavities; (e) coating a curable second fluid polymer composition over the first structured polymeric film to form a second polymeric film; and (f) curing the second polymer film while it is still in contact with the first structured polymeric film to render it solid and create a transparent second polymeric structured film comprising a first typically flat side and a second side with an array of microlenses formed thereon corresponding to the asymmetric shaped micro-cavities of the first structured film and separating the second structured polymeric film with the microlens array from the first structured polymeric film.