Preparation of durable hydrophobic and antireflective silica coating

To improve the durable hydrophobicity of sol-gel silica antireflective coating,methyl-modified silica sol was prepared through hydrolysis and condensation of tetraethoxysilane and methyhriethoxysilane under ammonia catalysis in ethanol solvent.Then the sol was dip-coated onto both sides of clean K9 glass substrate to form single layer coatings.The chemistry of coating was analyzed by FF-IR spectroscopy,the water contact angle of coating was measured by contact measurement,the transmittance of coating was measured by spectrophotometer,and the thickness and refractive index of coating were measured by spectroscopic ellipsometry.More importantly,the durability of hyddropobicity of hydrophobic coating was reported for the first time.The results showed that coatings gained water repellence and antireflectivity at the same time by introducing CH3 into Si-O-Si linkage.The peak transmittance of the coating was above 99.5%; the static water contact angle was 130°,and the hydropobicity of such coating could last for 5 months in environment with relative humidity of 90%.