Preparation And Characterization Of Multifunctional SiO₂ Anti-reflective Film By Sol-gel Method

Anti-reflection film is the most widely used and the largest production optical film,which can reduce the light reflection caused by sunlight or artificial lighting,and can be used in photovoltaic modules,electronic devices.As the research and application of anti-reflection film become more and more extensive,the single function of increasing the transmittance can no longer meet the increasing actual demand.Therefore,the anti-reflection film must be given more functions to meet its needs in practical applications.This paper mainly explores the versatility of the SiO₂anti-reflection film.On the basis of not losing the light transmission characteristics,the hydrophobicity and heat insulation properties and the adaptability of the flexible substrate adhesion under different processes of the SiO₂anti-reflection film are studied.First,silica sol is prepared by sol-gel method with tetraethyl silicate（TEOS）as precursor,and then the silicon dioxide（SiO₂）anti-reflection film is plated on the glass substrate by spin coating.The effects of different p H environments,the amount of ammonia,the amount of ethanol,the aging time and the spin coating speed on the microstructure and light transmittance of the film were studied.Through the adjustment of these process parameters,the transmittance of the glass sheet with anti-reflection film in the visible light range has been increased from 90.90%to 94.88%.Then,the hydrophobic properties of the SiO₂anti-reflection film under the two modification processes are studied.The first step is co-precursor modification by introducing methyltriethoxysilane（MTES）.When TEOS:MTES=1,the transmittance of the glass substrate is increased to 94.25%,and the surface water contact angle is 130°.The second step is to modify the hydrophilic surface of the sample in an organic solution of hexamethyldisilazane（HMDS）by the surface modification method.When the sample is immersed in an ethanol solution of HMDS with a concentration of 10wt.%,after 3h,the average transmittance of the sample was 95.60%,and the WCA is 128°.Next,the heat insulation performance of the SiO₂anti-reflection film under different processes is studied.In this paper,a self-made simulated sunlight device is used to test the thermal insulation temperature difference of SiO₂anti-reflection film.When the precursor is a single silicon source TEOS,the film has the best thermal insulation performance.Compared with bare glass,the temperature difference is 6.0℃.As the ratio of MTES increases,the thermal insulation performance of the film gradually decreases.When the mass ratio of TEOS and MTES is 1:1,the temperature difference drops to 3.8°C.When MTES is used as the only silicon source,the temperature difference drops to 2.1°C.Finally,in order to explore the realization and application of SiO₂anti-reflective film on flexible substrates,we studied the spin-coating of multifunctional SiO₂anti-reflective film on flexible and colorless transparent polyimide（CPI）substrate.The effects of different amounts of ethanol on the microstructure,transmittance,wettability and thermal insulation properties of the film were explored.SEM showed that the anti-reflection coating was still attached to the CPI substrate intact after the sample was bent 200 times.At the same time,the hydrophobic properties of the surface were still maintained.