Formation of anti-reflective alumina films on polymer substrates by the sol–gel process with hot water treatment

Al2O3 films with a small roughness of less than 100 nm prepared through the sol–gel method have been found to show anti-reflective (AR) property in a wide wavelength region on polymer substrates such as poly(ethylene terephtalate) (PET), poly carbonate (PC), and poly(methyl methacrylate) (PMMA). The highest AR effects were obtained on PMMA substrates, the refractive index of which is similar to that of porous Al2O3 gel films. The reflectance of PET, PC, and PMMA substrates coated with flowerlike Al2O3 was less than 1.5, 1.0, and 0.8% in the visible light region, respectively.