Method to optimize charge distribution in electret films using multiple needle discharges

The purpose of this paper was to find the optimal parameters of moving multiple needle corona discharges by looking at the transport velocity and the distance of the needles. The parameters were then used to symmetrically arrange the discharge needles for large-scale mass production. A corona discharge method is typically used to perform charge injection in the creation of electret films. A static single needle corona discharge method typically leads to a non-uniform space charge distribution in electret films. Since obtaining uniformly injected charge distribution and uniform efficiency of large-area electret films have become important research topics recently, methods such as moving multiple needle corona discharges have been developed to improve production efficiency and uniformity in the spatial charge distribution of electret films for industrial applications. An automated control system was developed using VB (Visual Basic) to create a virtual instrument to perform the corona discharges and to measure the surface potential. Several important processing parameters were identified to enable us to obtain uniform spatial charge distribution in newly created electret films.