Sol-gel derived single-layer zeolite-based coatings on glass for broadband antireflection properties

In this study, a simple and effective sol-gel method was used to generate antireflection coatings on borosilicate glass substrates. Commercially available zeolite 4 Å powder and tetraethyl orthosilicate were used as the starting materials to synthesize the sol. Single layer antireflection coatings were generated on borosilicate glass substrates using dip coating technique and densified in air at 450 °C. Optical properties were analyzed using UV-Vis-NIR transmittance/reflectance spectrophotometer and variable angle spectroscopic ellipsometer. Mechanical properties were analyzed using adhesion, pencil scratch hardness testing as well as using crockmeter tests. The antireflection coatings were found to exhibit excellent broad band transmittance over the visible wavelength range. An average transmittance of 96.8 ± 1% could be obtained for the wavelength range 400-800 nm. The reflectance of the bare borosilicate glass substrate was found to decrease from 8.6 ± 0.1% to 2.5 ± 0.05% after deposition of the antireflection coating. The scratch hardness of the coatings was determined to be 6H and adhesion tests showed the adhesion to be of rank 5B. The transmittance loss was 0.9 ± 0.1% after 1000 cycles of crockmeter test using a cotton fabric as the abrading medium. The single layer zeolite-based antireflection coatings were found to exhibit good mechanical properties and could be used for a variety of applications.