Preparation of Super-Water-Repellent Alumina Coating Film with High Transparency on Poly(ethylene terephthalate) by the Sol–Gel Method

Abstract
Al2O3 gel films were prepared on poly(ethylene terephthalate) substrates from Al(O–sec-C4H9)3 chemically modified with ethyl acetoacetate. A small roughness of about 20–50 nm was found to form on the Al2O3 gel films dried at room temperature and then immersed in hot water at 60 °C. When hydrolyzed fluoroalkyltrimethoxysilane was coated on the Al2O3 films, transparent thin films with contact angle for water to be more than 150° were obtained.