Surface Modification of Poly(Tetrafluoroethylene) Films by Graft Copolymerization for Adhesion Improvement with Sputtered In-Sn Oxides

Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films was carried out via UV-induced graft Copolymerization with glycidyl methacrylate (GMA), acrylamide (AAm) and hydroxylethylacrylate (HEA) to improve the adhesion strength with sputtered indium-tin-oxide (ITO). The surface compositions of the graftcopolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The graft yield increases with increasing monomer concentration and Ar plasma pre-treatment time of the PTFE films. The T-peel adhesion strength was affected by the type of monomer used for graft Copolymerization, the graft concentration, and the thermal post-treatment after ITO deposition. A double graft-copolymerization process, which involved initially the graft copolymeri/ation with AAm or HEA, followed by graft Copolymerization with GMA. was also employed to enhance the adhesion of sputtered ITO to PTFE. T-peel adhesion strengths in excess of 8 N cm were achieved in the ITO graft-modified PTFE laminates. The adhesion failure of the ITO/PTFE laminates in T-peel tests was found to occur inside the PTFE films. The electrical resistance of ITO on all graft-modified PTFE surfaces before and after thermal post-treatment remained conslant at about 30 Ω square, suggesting that the graft layer did not have any significant effect or. the electrical properties of the deposited ITO.