US 6,866,977 : Photoconductive elements having a polymeric barrier layer
Molaire, Michel F. (Rochester, NY, US)
O'regan, Marie B. (Santa Barbara, CA, US)
Ferrar, Wayne T. (Rochester, NY, US)
Weiss, David S. (Rochester, NY, US)
Cowdery, Jane Robin (Webster, NY, US
Disclosed are photoconductive elements including a conductive support, e.g., an electrically conductive film, drum, or belt, on which a negatively chargeable photoconductive layer is disposed. An electrical barrier layer is disposed between the conductive support and the photoconductive layer. The barrier layer provides a high energy barrier to the injection of positive charges, but transports electrons under an applied electric field. In embodiments, the barrier layer can transport charge by electronic mechanisms, and, is not substantially affected by humidity changes. The barrier layer includes a polyamide-co-imide having covalently bonded as repeat units in the polymer chain, aromatic tetracarbonylbisimide groups of the formula:
wherein Ar1 and Ar2 respectively represent tetravalent or trivalent aromatic groups of 6 to about 20 carbon atoms, and X is O, C(CF3)2, S═O or SO2. The amount of aromatic tetracarbonylbisimide content in the polymer is selected such that the barrier layer can be coated onto the support as a relatively thick layer, which provides for enhanced performance as a photoconductor when used in an electrophotographic process.