Semi-contact bias charge roller

An image forming apparatus comprising:

• an electrophotographic imaging member having a charge retentive surface configured to receive an electrostatic latent image;
• a development component to apply developer material to the charge retentive surface to form a developed image on the charge retentive surface;
• a transfer component for transferring the developed image from the charge retentive surface to a substrate;
• a bias charge roller for applying an electrostatic charge on the charge retentive surface to a predetermined electric potential wherein the bias charge roller comprises a first circumferential area in contact CC[contact] with the charge retentive surface and a second circumferential area CC[non-contact] spaced a distance of from about 1 μm to about 1 mm from the charge retentive surface;
• and
• a power supply for supplying an oscillating voltage signal to the bias charge roller wherein the oscillating voltage signal has a frequency Am[fAC], measured in kHz, and an amplitude Am[VAC], measured in kV, wherein a relationship (CC[contact]/CC[non-contact])≦(Am[fAC]/Am[VAC])≦(CC[non-contact]/CC[contact]) is met.