The HP Indigo process transfers liquid ink from the imaged photoreceptor to the media via a blanket, which possesses several key characteristics. Among these is sufficient conductivity to provide the electric field necessary to draw the charged ink from the photoreceptor. In this work we describe an impedance measurement technique to assess blankets. We find that features in the data can be assigned to individual layers within a blanket responsible for electrical transfer. The outer layer adjacent to the ink generally blocks charge within the contact nip time, suppressing possible ink discharge. The inner layer underneath readily allows charge through so that a sufficient field can be set up between the photoreceptor and blanket electrodes. The measurement also clarifies the role of temperature and the effect of absorbed imaging oil during the operation.
Michael H. Lee, William D. Holland, "Impedance Technique for Assessing Indigo Blanket Electrical Properties" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP25), 2009, pp 257 - 260, https://doi.org/10.2352/ISSN.2169-4451.2009.25.1.art00072_1