| abstract |
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. |