Abstract
The authors observed contact charging of a PET film with a rubber roller, and a series of small electrostatic discharges between the layers of the charged film when the film is wound into a roll. In the contact charging with the rubber roller, the surface charge density of the film decreases as the roll becomes bigger. The surface potential of the roll, however, is increasing as the result of the integral of the charges. This results in the occurrence of the tree-like discharges. Moreover, small discharges occur at strongly charged areas of the film. Once the discharges occur at a layer of the film roll, they tend to occur at every outer layer of it, leaving short term (about 1-2mm), high density surface charges of opposite polarity on all these layers of the film in the roll.
