Antireflective coatings using organically modified silica and polyimide via solution casting method

Antireflective (AR) coatings were prepared using a polyimide and two types of organically modified silica colloids via a solution casting method. The optically transparent polyimide was prepared from 2,2′‐Bis4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 4,4′‐oxydianiline (ODA). The silica colloids were driven to the coating‐air interface by either the fluorinated alkyl group or PDMS (Polydimethylsiloxane) segment tethered onto the silica colloids. The amount of fluorinated alkyl groups and the molecular weight of the siloxane grafted on the silica colloid were varied. The PDMS‐silica and fluorosilica colloids were characterized by TEM (Transmission Electron Microscopy), DLS (Dynamic Light Scattering), FTIR (Fourier Transform Infrared Spectroscopy), solid‐state ¹³C NMR (Nuclear Magnetic Resonance) and solid‐state ²⁹Si NMR. The AR coatings were characterized by UV–vis (Ultraviolet–Visible Spectroscopy) transmittance spectra, AFM (Atomic Force Microscope), and SEM (Scanning Electron Microscope). The effects of modified silica loading and type of solvent on AR properties were studied. An enhancement in AR activity was observed for 1 wt% PDMS‐modified (low molecular weight) silica coatings and 3 wt.% fluorosilica‐10 in dimethylacetamide (DMAc). In comparison with cyclopentanone (CPT), DMAc favors migration of silica particles toward coating‐air interface giving higher transmittance. The migration of particles to the surface and consequently increased surface roughness was observed by SEM. POLYM. ENG. SCI., 53:2228–2241, 2013. © 2013 Society of Plastics Engineers