Preparation of Anti-reflection Coatingswith Hollow Silica Nanoparticles by Self-assembly

Using tetraethyl orthosilicate (TEOS) as raw material and polyacrylic acid (PAA) as nucleating material, hollow silica nanoparticles were synthesized on the basis of traditional method of Stber. Using hollow silica nanoparticles, both single-layer anti-reflection coatings and broad-band double-layer anti-reflection coatings were prepared by self-assembly. The structure control of the hollow silica nanoparticles, the effect of deposition cycle, pH value of the hollow silica nanoparticle dispersion on transmittance of coatings, and the preparation of the double-layer anti-reflection coatings with a graded-refractive-index were investigated. The results show that the size and void fraction of the hollow silica nanoparticles can be controlled precisely by changing the amount of PAA and TEOS. The thickness and refractive index of the anti-reflection coatings can also be tuned accurately in the same way. The deposition cycles are reduced from 10 cycles to 2 cycles by acid pickling which simplifies the coating process. This new technique significantly increases the transmittance of glass substrate coated by single-layer anti-reflection coatings in the range of 350-800 nm under optimum conditions, and improves the maximum transmittance from 91.6% to 98.1% at optimized wavelength (=520 nm). Furthermore, glass substrate coated by double-layer anti-reflection coatings can increase the transmittance more than 5% in a much wider wavelength range