Decay of electrical charge on polyethylene films

Abstract

The characteristics of the decay of the surface potential of corona-charged untreated polyethylene films 25 mu m thick in air have been investigated using a well-defined circular charging area and a high-resolution 80 mu m diameter induction probe. Distinct differences between the decay characteristics of negative and positive surface charges emerge. In the former case, the nature of the decay is shown to depend not only on the magnitude of the surface potential (700-3000 V) but also on the presence of the corona light. Corona light incident on the centre of the exposed area during charging subsequently leads to a much more rapid decay of charge in this region. In contrast, corona light has no effect on the subsequent decay of positive charges which appears to decay very much in accordance with known theories. The corona light is shown to be responsible for the so-called 'cross-over' phenomena which hitherto has been observed, notably by Ieda and co-workers (1967, 1968) after positive charging.