Preparation of octyltrimethoxysilane modified SiO₂ hydrophobic antireflective coating

The standard SiO₂ sol was prepared by sol-gel process using tetraethylorthosilicate (TEOS) as precursor and ammonia as catalyst. Octyltrimethoxysilane (OTMS) was added into the standard SiO₂ sols before and after refluxing to obtain different organosilane modified silica sols, respectively. Silica antireflective (AR) coatings were then prepared from different SiO₂ sols by dip-coating method. The optical and structural properties of the AR coatings were characterized by Fourier transform infrared spectroscopy, liquid-state ²⁹Si NMR, UV-Vis-NIR spectrometer, atomic force microscope and water contact angle measurement. The results show that the AR coating prepared from OTMS modified before refluxing has the best moisture-resistant performance. The coated glass substrate obtains a high peak transmittance of 99.7%, with water contact angle of 120°. After been placed in a humid environment for 4 w, the transmittance of SiO₂ coatings modified before refluxing is decreased only by 0.23%.