HIGH FREQUENCY PULSED BIAS ROLLER TRANSFER SYSTEM
Original Publication Date: 1976-May-31
Included in the Prior Art Database: 2004-Mar-27
Xerox Disclosure Journal
xerographic transfer of toner from a photoreceptor 1 to a copy sheet 2 utilizing a conductive transfer roller 3 which is electrically biased with a pulsed high frequency bias potential source 4. The pulsing frequency is made greater than the RC time constant of even humid copy paper so that the applied transfer charge does not have sufficient time to leak off or through the copy paper even under high humidity conditions. That is, the copy paper would behave like a dielectric for the applied transfer field at the roller surface even when the paper resistiv~ ity is low, to allow the application of an effectively constant peak electrostatic transfer field regardless of humidity. Frequencies of 50 KC to 500 KC or higher are suggested, depending on the actual paper resistivity and thickness, i.e., the minimum frequency desired would depend on the system capacitance and resistance, A fre~ quency five times the system RC time constant is believed to be appropriate. This system would enable the use of conductive transfer rollers capable of applying higher transfer fields through the copy sheet for the same externally applied voltage than rollers of the insulative coated or highly resistive or lossey dielectric material type. The pulsation in the transfer field level may also assist in dislodging the toner adhering to the photorecep- tor surface, to improve transfer efficiency.