US Patent 9303132 Exterior window film

A transparent exterior window film composite comprising a base sheet material having an outer PET (polyethylene terephthalate) film layer which has been surface treated to elevate adhesion thereto and which is impregnated with an ultra violet light absorber (UVA), the treated surface being coated with a UV stabilized acrylic polymer or co-polymer undercoat having a UV stabilized hard coat layer thereon formed from at least one aliphatic urethane acrylate oligomer and at least one multifunctional acrylate monomer, the undercoat layer having a thickness which is at least as thick as the hard coat.