Assessment of Resistivity Uniformity of HP-Indigo Developer Rollers

The binary ink developer in the HP-Indigo press selectively applies condensed ElectroInk® onto the photoreceptor to form the image. The ink is transported by the elastomeric developer roller, which needs to be sufficiently conductive to allow its surface voltage remains constant as it moves through the various interfaces encountered along its periphery. But it cannot be so conductive as to discharge the ink before it is developed. So it would be useful to know the roller resistance and its uniformity. In this work we describe an impedance technique to map the developer roller resistance across its surface. The roller only needs to be a single conductive dielectric layer. Hence its relevant impedance spectrum can be simple and uniquely determined by the corresponding capacitance and resistance obtained at a single well-chosen frequency. Although the actual material can be more complex, we show that scanning the roller surface at one frequency can provide very useful information. The process is reasonably rapid, allowing multiple rollers to be readily compared to see if process/materials variations produce changes. External Posting Date: July 6, 2011 [Abstact Only] Approved for External Publication Internal Posting Date: July 6, 2011 [Fulltext]  Copyright 2011 Hewlett-Packard Development Company, L.P. Developer roller Cleaner roller