Antireflective silica thin films with super water repellence via a solgel process

A solgel process was developed, through which silica films possessing both high antireflection and super water repellence were obtained. In this process, methyl-modified SiO2 sols synthesized by colloidal suspension of SiO2 particles and hexamethyldisilazane (HMDS) were used to deposit spinning-coating films on optical glass substrates. On the resultant films the contact angle for water increased with the increasing amount of HMDS in the reaction mixture. The biggest contact angle was 165 degrees, and the lowest reflectivity on one-sided film reached 0.03%. The antireflections were high all the while. One advantage of this process is that neither a roughened surface nor fluoroalkyltrialkoxylsilane (FAS) is needed to obtained super water repellence.