Effect of polyvinyl butyral on the microstructure and laser damage threshold of antireflective silica films

Silica antireflective films modified by polyvinyl butyral (PVB) were deposited on fused silica substrates by sol–gel process. The effects of PVB on the microstructure and laser damage threshold (LIDT) of films were investigated. The results of the nano particle analyzer and scanning probe microscope revealed that PVB molecules surrounded silica particles and controlled the particle growth, which resulted in a stable sol with uniformly distributed silica particles. Therefore, the films deposited from these modified sols possessed more uniform microstructures than the films without PVB. The adhesive-resistance test indicated that the strength of the modified silica films increased due to the bond reaction between PVB molecules and silica particles. The introduction of PVB into silica sols had also increased the LIDT of films. The LIDT of films increased from 30.0 J/cm2 to 40.1 J/cm2 after 1.0 wt.% PVB was added. The increase in LIDT was attributed to the increased strength and uniform microstructures of films as an effect of the PVB modification.