Moisture-proof antireflective coatings derived from liquid-phase and vapor-phase fluoro-modification methods

Moisture resistance is one of the most crucial issues for sol-gel antireflective (AR) coatings. In this work, two kinds of fluoro-modified AR coatings named MSolF and MGasF coatings with satisfactory moisture resistance have been prepared via liquid-phase copolycondensation and vapor-phase grafting with fluoroalkylsilane, respectively. The fluorine-containing groups are attached to the silica networks through the two fluoro-modification methods, resulting in a significant increase in water contact angle and a decline of coating surface free energy. The fluoro-modified coatings both possess nice dynamic dewetting, water repellency and moisture barrier performance. After exposure to a 90%RH humid environment for 3 months, the average transmittance in the wavelength range over 300–1200 nm of MSolF1 and MGasF1 coated BK7 glasses only decreases by 0.07% and 0.06%, respectively. The superior moisture-proof performance benefits from the combination of two factors: the added long fluoroalkyl chains yield excellent water repellency that greatly reduces the adhesion of water vapor on the coating surface; the densified structure benefited from two fluoro-modification methods prevents water molecules from further permeating into the coatings. Furthermore, the differences between the two fluoro-modification routes are also compared in detail for making appropriate choices in various working environments.