| abstract |
An improved silane/silica sol copolymer hardcoating composition for protecting optical plastic substrates from scratching is able to be manufactured at lower costs and to provide much-improved ease of use in transportation, storage, dipbath stability, and blush resistance in ordinary cleanroom atmospheres. The silane/silica sol copolymer is formed as a direct reaction product of an acidic silica sol and an monomethyl trialkoxy silane, preferably substantially monomethyltriethoxysilane, in ratios of 30:70 to 70:30, most preferably about 40:60. A tail solvent aids blush resistance and adhesion to unprimed polycarbonate. Optionally, colloidal silica sol dissolved in water-miscible solvent may be reacted in a second stage with acidic aqueous colloidal silica sol earlier silanized with monomethyl trialkoxy silane. |