Developing polymeric antireflective coatings

Abstract

ABSTRACT As polymers become more widely used in optics antireflective coatings need to be designed specifically to suit these new components. Modifications are being made to the current high temperature coating process to allow for inorganic metal oxides to be applied to polymer optics. This is not however the only hurdle that needs to be overcome to produce a satisfactory antireflective coating on polymers. Inorganic metal oxides and polymer components have a significant difference in thermal expansion meaning that defects such as delamination and cracking can occur. These defects significantly shorten the lifetime of the optical component. A new antireflective coating has been developed that has a similar thermal expansion coefficient to that of the polymer substrate, meaning that defects caused by thermal stress do not occur. These are polymeric coating with a refractive index of 1.31 and 1.34, lower than that of magnesium fluoride (MgF 2 ) at 1.38. These coatings have antireflective properties superior to those of current commercially available single layer inorganic antireflective coatings. Polymer antireflective coatings cannot be applied by vacuum deposition. Dip coating was evaluated as a method for film application. Dip coating allows control of the film thickness through varying the properties of the coating solution. It also allows for uniform films that can be inspected visually for variances. Keywords: amorphous fluoropolymer, antireflective, thermal e xpansion, dip coating, film thickness