Patent 7095969 was granted and assigned to Konica Minolta on August, 2006 by the United States Patent and Trademark Office.
A developing device has a voltage application member which is in contact via a toner layer with a developing roller that rotates while holding the toner layer on its outer peripheral surface. A voltage that the voltage application member applies to the toner layer is switched between AC voltage and DC voltage based on humidity or drive cumulated time of the developing device.