The effect of the solvent on the cross-link density of SiO2 coatings

With increasing screen size of television and computer monitor tubes the spin-coating of tetraethylorthosilicate (TEOS) based sol-gel coatings becomes an increasingly difficult task. To retain sufficient uniformity and scratch resistance of the coatings, changes in the composition of the coating liquids and the coating procedures are needed. Changing solvents and adding catalysts can lead to increased cross-link density which has been measured by Si-29-NMR. The cross-link density increases with increasing average number of hydroxy groups on the Si atoms in the drying phase, which can be tailored by adjusting the water concentration, by using water vapour or by using solvents which do not cause the re-esterification of alkoxy groups on the Si atoms during drying. (C) 1999 Elsevier Science S.A. All rights reserved.