An improved, user-friendly
silane / silica
sol copolymer hardcoating composition for protecting optical plastic and other substrates (including wood, metals, glass, plastics and most coated articles) from
scratching is able to be manufactured at lower costs and to provide much-improved ease of use in transportation, storage, dipbath (or other
coating tank) 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 monomethyltrialkoxysilane, preferably substantially monomethyltriethoxysilane, in ratios of 30:70 to 70:30, most preferably about 40:60. A
tail solvent aids blush resistance, reduces
internal stress and permits 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 monomethyltrialkoxysilane.