Incorporation of Crosslinking Polyelectrolytes with Silica Nanoparticles into Layer-by-Layer (LbL) Self-Assembled Anti-Reflection Films for Improved Scratch Resistance and Stability

摘要

Antireflection coatings (ARCs) are commonly used to reduce substrate reflection, while maximizing transmission, in the visible wavelength range of incident light. Previous work1 has developed ARCs through the ionic self-assembled multilayer (ISAM) fabrication of poly(allylamine hydrochloride) (PAH) and silica nanoparticles (SiO2 NPs). From the resultant porosity intrinsic to the film, an average refractive index was obtained within the film between that of the substrate (in this case glass n=1.50) and the surrounding medium (air, n = 1.00). Based on the SiO2 NP diameter, this average refractive index resided near to the ideal value of 1.22 with film porosity at 30% to 45%. While this porosity is critical in creating a refractive index for the film near the ideal value, the stability of the film was lacking. Since ISAM growth is based upon electrostatic attraction, the exposed surface area of the nanoparticles provides limited contact points leading to reduced stability. ISAM nanoparticle films also exhibit instability in the interaction of polar solvents. The incorporation of photo-curable crosslinking oligomer, diazo-resin (DAR), into our ionically bonded layer-by-layer films has shown promising prospects for increasing the films stability. DAR is a thoroughly studied polycation that allows for the conversion of ionic to covalent bonding between several negatively charged functional groups, by the decomposition of its diazoum group under UV irradiation (Figure 1).