Device and method for printing on both faces of a recording medium, comprising a charge shifting and recharging device

摘要

In a method or device for simultaneous double-sided printing of a recording medium, the first toner image having toner charged with a first polarity is generated on a first transfer belt and a second toner image having toner also charged with the first polarity is generated on a second transfer belt. A charge shifting device is provided along with a recharging device. At least one of the charge shifting device and the recharging device has a corotron. With the charge shifting device, the charge of the first toner image is shifted to a second polarity opposite to the first polarity and with the recharging device the second toner image with the first polarity is recharged. The recording medium is passed between the first and the second transfer belts. An electrical field is generated at a transfer printing region via which the first toner image shifted to the second polarity and the recharged second toner image are separated from the respective first or second transfer belt and are transferred to a side of the recording medium facing the respective transfer belt.