Large format cylindrical lens films formed by roll-to-roll ultraviolet embossing and applications as diffusion films

A roll-to-roll (R2R) ultraviolet (UV) embossing system has been developed for manufacturing micro features on continuous flexible films. The R2R UV embossing system, which has an embossing roller of 160 mm in diameter, can handle flexible polymer films with a width up to 500 mm and thickness ranging from 0.05 to 0.5 mm. A metal sheet template with micro features on its surface is mounted to the embossing roller and used as embossing mould. A slot die coating unit that has a coating width of 250 mm is used to deposit liquid UV curable resin on polymer films and coating thickness ranging from 10 to 50 mu m has been achieved. Continuous roll-to-roll UV embossing is conducted and optical films with cylindrical lens arrays (curvature radius = 112 +/- 2 mu m, sag height = 28 +/- 0.5 mu m and pitch = 150 +/- 2 mu m) are formed. The optical films are used for diffusion to improve light uniformity of a printed lighting film that consists of lighting stripes and dark blank lines. The evaluation results show that the non-uniformity of light intensity can be reduced from 30% (with only lighting panel) to about 3% with the cylindrical lens films.