A study of non-uniform charging by charging roller with DC voltage

Model experiment is carried out using metal roller and PET (polyethylene terephthalete) sheet for the analysis of the generating mechanism of the non-uniform charging together with the numerical simulation. It is difficult to obtain uniform charging by charging roller with DC voltage. The periodic charging patterns can be recognized on the PET sheet by cascade development with toners after the sheet is charged. The period and the size of the patterns become large as the applied voltage increases. The shapes of the patterns are different between positive and negative charging. The morphology of the patterns is very similar to that of separating discharges on electrified insulating sheet. The results of the investigation show that the charging patterns are made as follows. (1) Strong discharge occurs between the charging roller and the PET sheet. Large amount of charge is deposited on the sheet. (2) That charge moves because of surface discharge.2-dimensional electrostatic simulation of the charging roller shows the periodic patterns on the PET sheet due to the effects mentioned above.