Anti-reflective properties of nano-structured alumina thin films on poly(methyl methacrylate) substrates by the sol–gel process with hot water treatment

Alumina gel films were coated on poly(methyl methacrylate) (PMMA) substrates using the sol–gel process, and pseudo-boehmite nanocrystals of several tens of nanometers were precipitated on the surface of the alumina gel films through immersion in hot water. It was found that the PMMA substrates, which were coated with the pseudo-boehmite nanocrystals precipitated alumina, exhibited very slight incident-angle dependence in transmittance up to 60°. The reflectance of PMMA substrates coated with the nanocrystal-precipitated alumina was less than 0.8% in the visible light region.