Use of variothermal heating for the extrusion embossing of microstructured poly(methylmethacrylate) and polycarbonate optical films

The importance of microstructured parts and extrudates is rising because of the increasing functional integration in many different fields of application, for example in the automotive industry and medical technology. Variothermal extrusion embossing is a continuous process that combines plastic film production with the application of large-area microstructures. The process utilizes an embossing roll and an external heating device to continuously imprint the desired structure into film during extrusion. Through this microstructuring, it is possible to integrate innovative functions into a film. Present efforts are focused on forming optical structures (micro-optics) on polycarbonate and poly(methylmethacrylate) films. This article deals with process control requirements that are necessary to successfully apply this technology, and also demonstrate how, through suitable process parameter selection, high-quality microstructures can be effectively embossed on the films. Different microstructures between 24 and 165 µm in height and between 100 and 200 µm in width are tested. With poly(methylmethacrylate) better microstructure reproduction could be achieved than with polycarbonate.