Robust alkali-resistance of cover glass's UV-shielding and strengthening sol-gel coatings by tailoring the coupling between SiO2 and 2,2′,4,4′-tetrahydroxybenzophenone

Abstract

Cover glass with UV-shielding function is important to mobile displays such as mobile phones and tablet PCs, as well as flexible photovoltaic cells. UV-shielding over 90 % while visible light transmittance over 90 % is a rather difficult technical challenge for cover glass. In this report, robust alkali-resistance of display cover glass's UV-shielding and strengthening sol-gel coatings have been successfully prepared, using 2,2′,4,4′-tetrahydroxybenzophenone (BP-2), γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560) and tetraethyl orthosilicate (TEOS) as raw materials. The coupling between SiO2 and BP-2 was tailored by using a condensation reflux method for the mixture of BP-2 and KH560. Compared to blank glass (0.7 mm thickness), UV-shielding (UV-A and UV-B) of the coated glass (coated on one side, 3 μm thickness of coating) increases significantly from 13.43 % to 99.93 %, while the visible light transmittance (380–780 nm) changes only slightly from 91.87 % to 90.16 %. Moreover, the bending strength of the coated glass improves by 52 MPa, and the drop ball impact resistance increases by 16 %. After alkali corrosion, glass's UV-shielding with the BP-2/SiO2 coupling or uncoupling coatings is 90.03 % or 80.03 %, respectively. The BP-2/SiO2 coupling coatings significantly improve alkaline corrosion resistance. Fourier transform infrared spectroscopy analysis confirms that BP-2 is chemically grafted into the SiO2 grid of the coating, which contributes to the robust alkali-resistance. Demonstrated by the finite element simulation, the strengthening effect originates from the repair of cracks on the surface of glass by the coating. The coating presents its application possibility on cover glass.