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) (PTF E) films was carried our via W-induced graft copolymerization with glycidyl methacrylate (GMA). acrylamide (AAm) and hydroxylethylacrylate (HEA) to im prove the adhesion strength with sputtered indium-tin-oxide (ITO). The surf ace compositions of the graft-copolymerized PTFE Alms were studied by X-ray photoelectron spectroscopy (XPS). The graft yield increases with increasin g monomer concentration and Ar plasma pretreatment Lime of the PTFE films. The T-peel adhesion strength was affected by the type of monomer used for g raft copolymerization, the graft concentration, and the thermal post-treatm ent after ITO deposition. A double graft-copolymerization process, which in volved initially the graft copolymerization with AAm or HEA, followed by gr aft 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 f ilms. The electrical resistance of ITO on all graft-modified PTFE surfaces before and after thermal post-treatment remained constant at about 30 Ohm/s quare, suggesting that the graft layer did not have any significant effect on the electrical properties of the deposited ITO.