Effect of Hydrophobic Modification on the Durability and Environmental Properties of Porous MgF2 Antireflective Films

Conventional porous MgF2 antireflective films show poor environmental durability due to its hydrophilic nature. To improve the film environmental durability, hydrophobic porous MgF2 antireflective films are prepared by a methyl silicone-modified MgF2 sol. Effects of the methyl silicone proportions on the film properties are examined in order to control the wettability, peak transmittance, and environmental durability of the films. The modification of methyl silicone can increase the film hydrophobicity, thus decreases the adsorption of water, and improves the environmental durability. However, large amounts of methyl silicone could increase the film refractive index, resulting in the decrease in peak transmittance for films on BK7 glass. Films with 40% silicone show water contact angle of 110°, peak transmittance of 98.7%, and good environmental durability. The results of accelerated test show that the environmental durability of the porous MgF2 films modified with 40% methyl silicone is six times higher than that of the conventional films.