Nanopatterned Polymer Molds Using Anodized Aluminum Templates for Anti-Reflective Coatings

Abstract

This work introduces a facile geometry-controlled method for the fabrication of embossed and engraved polymeric moth-eye-inspired nanostructures in imprinting molds using anodic aluminum oxide (AAO) templates, resulting in a novel anti-reflective transparent coating. The moth-eye nanostructures are prepared directly on the surface of a flexible polyethylene terephthalate (PET) substrate. As a prerequisite procedure, a UV-curable polyurethane acrylate resin is spun on the PET. The shape of the moth-eye nanostructures can then be adjusted by controlling the size and shape of the nanopores in the AAO templates. Both embossed and concaved polymer moth-eye nanostructures were successfully mounted on a PET substrate. Embossed polymer replica molds were prepared using the AAO master templates in combination with an imprinting process. As revealed by field-emission electron microscope (FE-SEM) images, conical nanopatterns in the AAO template with a diameter of ~90 nm and a depth of ~100 nm, create a homogeneous embossed morphology in the polymer moth-eye nanostructure. The polymeric molds with the depths of 300 and 500 nm revealed the amalgamated structures in their apexes. In addition, a dip-imprinting process of the polymeric layers was implemented to yield a concaved mold by assembly on the surface of the 100 nm embossed polymer mold substrate. Considering that the embossed structures may be crumbled due to their protuberant shapes, the concaved geometries can have an advantage of stability in a certain application concerning physical degradation along with a higher transmission by ~2%, despite somewhat nonuniform structure. The experimental and theoretical results of this study indicate that this polymer layer has the potential for use in anti-reflective coating applications in transparent films.

Preparation of antireflection structures with heat resistance by nanoimprinting using anodic porous alumina molds

“…Several groups, including our group, have already reported the fabrication of antireflection structures consisting of tapered nanopillar arrays by nanoimprinting using anodic porous alumina molds. [15][16][17][18][19]24,25) However, the polymers used in conventional nanoimprinting have poor heat resistance, and under conditions exceeding 100 °C, shape deformation and carbonization occur, making it difficult to use them in antireflection structures under high-temperature conditions. The tapered nanopillar arrays prepared in this study showed no significant change in shape or color even after heat treatment at 200 °C.…”