Formation of large format functional films via roll-to-roll (R2R) ultraviolet (UV) embossing

Large format roll-to-roll (R2R) embossing is a continuous process suitable for manufacturing large area functional films at low cost and high throughput. R2R ultraviolet (UV) embossing has several advantages over R2R hot embossing as it offers lower processing temperature, lower embossing pressure and higher process speed. Hence, it is a promising approach for forming micro structures on flexible films. Some critical challenges in R2R UV embossing include fabrication of large area template and its durability, ensuring even coating across web, realization of low pressure & high fidelity micro structuring via UV curing, etc. A R2R UV embossing system has been developed, which can handle substrate film as wide as 500 mm. Both templates made of polymer-based sheets and those made of metal shims are employed as the molds for R2R UV embossing. Liquid UV curable resin is deposited on plastic films via a slot die coater, filled into template cavity by means of applied web tension and then cured via UV exposure. The functional films with embossed micro structures have been obtained after the embossed films are separated from the embossing roller. Micro pillars of 100 μm and ridges of 25 μm in width are formed on polymer films; micro prismatic structures and micro lenticular lens arrays are also formed for optical applications.