Modification of porous silica antireflective coatings with fluorine-containing organosilicon

Antireflective (AR) coatings prepared from colloidal suspensions of silica are porous and quite polar due to residual Si-OH. So the silica coatings readily absorb water or organic vapor which is detrimental to the optical performance. In order to improve the stability of AR coating, two series of antireflective coatings are prepared by sol-gel process with tetraethoxysilane as a precursor. All of them are modified with trimethoxy (3, 3, 3-trifluoropropyl)-silane and diethoxymethyl (3, 3, 3-trifluoropropyl)-silane. Experimental results show that hydrophobic performance of the coatings is enhanced significantly. The anti-reflectivity of the coating is high when the mass fraction of CF₃-CH₂-CH₂-Si or CF₃-CH₂-CH₂-Si-CH₃ is between 0.40%-1.5%. At a certain mass fraction of fluorine-containing siloxane, the performance of high laser damage threshold is not affected obviously. A series of tests are carried out by exposuring the coatings to vapor contamination in 10^-3 Pa vacuum chamber. The test results indicate that the stability and life of AR coatings are improved greatly.