Charge injection in corona-charged polymeric films: potential decay and current measurements
Abstract
Currents during corona charging and surface potential decay after corona charging have been studied on polymeric films. As has been reported before, surface potential is a useful tool for investigating the electrical properties of an insulating material, making it possible to discriminate charge injection from polarization processes, when data are correctly analysed, and it has also been shown that, on thin polymeric films, slow polarization processes leading to heterocharge formation dominate at low fields, while charge injection occurs above a given field threshold. We present here a combined study of the surface potential after charge deposit and current flowing on the back electrode during the corona charge; we show that current measurements during the charge confirm the interpretation of potential measurements after corona charge. The outbreak of “hollows” in the potential distribution on the surface is clearly linked to the predominance of injected charge on the polarization charge. However, even at high fields, polarization phenomena will dominate again a given time after corona discharge stopping.