Anti-reflective optical coatings incorporating nanoparticles

TLDR

The study proposes a simple method to form anti‑reflective film stacks on plastic substrates using aqueous colloidal dispersions of metal‑oxide nanoparticles. The method employs these aqueous colloidal dispersions to build the film stacks. The authors demonstrate that polymer films with continuously tunable refractive indices (1.46–1.54 with silica, 1.54–1.95 with ceria) can be fabricated by loading metal‑oxide nanoparticles, and that combining low‑ and high‑index layers yields anti‑reflective coatings with reflectance, abrasion resistance, haze, and transmission comparable to vacuum‑based methods, while aqueous dispersions can be diluted for spin‑coating.

Abstract

This paper presents a simple approach for forming anti-reflective film stacks on plastic substrates employing aqueous colloidal dispersions of metal oxide nanoparticles. Results demonstrate that it is possible to fabricate a polymeric thin film of continuously tunable refractive index over a wide range by loading the film with varying concentrations of metal oxide nanoparticles. Specifically, the refractive index for the polymer film was tuned from 1.46 to 1.54 using silica nanoparticle loadings from 50 to 0 wt% and from 1.54 to 1.95 using ceria nanoparticle loadings from 0 to 90 wt%, respectively. The low and high refractive index layers are then combined to create an anti-reflective coating which exhibits a reflectance spectrum, abrasion resistance, haze and transmission values that compare well with those produced using state-of-the-art vacuum based techniques. Furthermore, the results show that it is possible to begin with aqueous dispersions and then dilute them with organic solvents for use in a spin coating method to prepare the polymer-metal oxide nanoparticle composite films.