Sol-gel preparation of antireflective coatings with abrasion resistance by base/acid double catalysis and surface treatment

Abstract

The Antireflective coatings (ARCs) dip-coated in base catalyzed sol have been demonstrated excellent optical property for its high porosity. However, its poor abrasion-resistance limits the industrial promotion. In this paper, the porous silica ARCs with excellent optical properties and abrasion-resistance were prepared by base/acid double catalysis. At the beginning of spherical SiO2 particles growing process, the tetraethoxysilane (TEOS) sol-gel environment was basic as the function of ammonia catalyst. After a period of time, the environment was changed to acid by using hydrochloric acid as catalyst, substituting for ammonia. The sol prepared by this method shows excellent stability. When the aging time increased from 30 days to 180 days, the refractive index only increased 0.024. Compared with the films dip-coated in the base silica sol, the porosity was lower and the particles’ agglomeration was more obvious. Besides, the coated glasses also possess better optical property and abrasion-resistance. The peak transmittance of the samples increased from 98.6% to 98.9%, while the pencil hardness grade also increased from <6B to 2B degree. The cotton scrubbing test also proved the improvement of abrasion-resistance. The poly (methylhydrogen) siloxane (PMHS) surface treatment was proved to be a great assistant for the base/acid double catalysis process. After the treatment, the pencil hardness grade could further increase to 5H, while the peak transmittance only decreased 0.3%.