| Summary: | We studied the mechanism of and countermeasures against a pale image defect observed in the halftone area following a solid image in a two-component magnetic brush electrophotographic development system. We build a model machine that consisted of a pseudo-photoreceptor drum, development sleeve, and stationary magnetic roller to perform direct observations of the toner and carrier particles in the development area. The image was formed on an insulated film electrode pasted onto the drum. Instead of a digital halftone image, an analog halftone image was formed on the pseudo-photoreceptor. A parameter experiment showed that the image defect was enhanced when the voltage difference between the solid area and halftone area was large, the AC voltage superposed on the DC development voltage was low, the development gap was large, and the ratio of the sleeve speed to the drum speed was low. However, the defect was almost independent of the toner-to-carrier concentration ratio as well as the frequency and waveform of the superposed AC voltage. The dynamic behavior of the toner particles in the development area was directly observed using a high-speed microscope camera, and the cause of the print defect was investigated.
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