Preparation and characterization of polyvinyl butyral/silica hybrid antireflective coating: Effect of PVB on moisture-resistance and hydrophobicity

A new modified antireflective coating was prepared by base catalyzed sol-gel process using tetraethylorthosilicate as precursor and polyvinyl butyral as modifier. The properties of the silica sols and AR coatings were characterized with Fourier-transfer infrared absorption spectroscopy, particle size analyzer, transmission electron microscope, programmable rheometer, UV-Vis spectrophotometry, ellipsometry, atomic force microscope and contact angle measurement. It was found that addition of 4% PVB greatly enhanced moisture-resistance of the AR coating. Optical transmittance of 4% PVB modified AR coating on BK7 substrate was found to be nearly 100%. The water contact angles of normal and 4% PVB modified AR coating were 51 and 53°, respectively, which indicates no significant increase of hydrophobicity of the modified coating. The peak transmittance of 4% PVB modified AR coating was almost unaffected after being exposed to the moist surroundings while that of normal silica coating decreased sharply from 99.8 to 96.5% within 2 weeks. The excellent moisture-resistance of PVB modified AR coating may be attributed to the adsorption of PVB on the surface of AR coating.