Two-layer hard coatings on transparent resin substrates for improvement of abrasion resistance

Two-layer hard coatings were prepared on transparent resin substrates (polymethylmethacrylate PMMA, polycarbonate PC) by the dipping method using commercial UV-cured and thermally cured hard coating solutions as starting materials. The former was used for preparing an underlayer, the latter was used for preparing a top layer. Three kinds of silane coupling agent and other additions were used to increase the adhesion between the two layers. The abrasion resistance improved remarkably compared with a single layer of the thermally cured hard coating. The result of the Taber abrasion test for the substrate treated using this method was very similar to that for inorganic glass. The influence of the various kinds of silane coupling agent and other additions on the adhesion between the two layers was examined in detail. The molecular structure of the silane coupling agents and other additions was studied using Fourier transform nuclear magnetic resonance. The chemical state of the interface between the two layers was studied using X-ray photoelectron spectroscopy and Fourier transform IR spectroscopy.