Fabrication of Large Area Broadband and Omnidirectional Antireflective Transparent Foils by Roll‐to‐Roll Extrusion Coating

This study investigates the fabrication and performance of broadband and omnidirectional antireflective polymer foils, in the visible spectrum (400–800 nm), consisting of subwavelength inverted moth‐eye structures. The foils are fabricated by a high throughput roll‐to‐roll extrusion coating process allowing structuring on both sides at a rate of 60 m min −1 , with web width 45 cm. The highest average transmittance obtained in the visible spectrum is (98 ± 1) %; compared with (92 ± 1) % for the unstructured foil. The antireflective foil shows no significant difference in transmittance between normal incidence and incidence up to at least 60°. The foil performance is also investigated for different depths ( Dp ) and shapes of structures. The transmittance initially increases with Dp and reaches a maximum at Dp ≈ 120 nm. For process parameters yielding greater depths, other shape factors also play a critical role in the foil's antireflective properties. image