Fabrication of organic-inorganic hybrid thin films using sol-gel method to improve scratch resistance and anti-fouling of plastic substrates

Abstract

Curved display cover windows are used to protect the display panel from external stimuli, which have gained attention in smart phone, monitor, and automotive industries in recent years. They require properties that can enhance the curved cover window such as scratch resistance, anti-fouling, transparency and so on. Thus, we report a simple method to fabricate an organic-inorganic hybrid coating film that can be applied to curved display cover window by the sol-gel process. This process has several advantages including low cost, low energy consumption, and easy coverage of large areas. The organic-inorganic hybrid coating solution was prepared by adding decyltrimethoxysilane (DTMS) and phenyl-trimethoxysilane (PTMS) to a solution synthesized based on metal alkoxide precursor (tetraethylsilcate (TEOS)) and alkoxy silanes (3-glycidoxypropyltrimethoxysilane (GPTMS)). The organic-inorganic hybrid all thin films fabricated on PMMA substrates by a dip coater showed high optical transparency of 92.0 to 93.3 % at 550 nm. In addition, the measured root mean square (RMS) roughness of the hybrid film was 2.18 nm or less. This indicates a very low surface roughness and confirms the fabrication of smooth films. Notably, the coating film with a TEOS:GPTMS:DTMS molar ratio of 1.0:0.1:0.1 coating film exhibited anti-fouling properties with high hydrophobicity of 95 ^° water contact angle and 5H pencil hardness, which is expected to be coating film for application to the wide range of curved display industries.