In the monocomponent non-magnetic toner developing system, optimum toner charging and mass transfer are important factors to produce high quality images. Also the uniformity of the image is one of the most important properties in electrophotography. One major type of nonuniformity is the problem of image density degradation also known as ghosting. In this article this phenomenon is discussed in terms of the toner charging and mass transfer characteristics during the first and subsequent roller revolutions. It was found that although the toner charge and toner mass on the development roller surface are very important parameters they are not the only causes of the imaging density difference. It was also found that the relationship between roller surface properties and toner development efficiency are closely related to the uniformity of the printed image. It is demonstrated that the optimum development roller requires low charge retention on the roller surface and low current leakage between the supply and the development rollers. Finally the design features of a two-layered development roller are described, that provides significant improvement of image density uniformities in continuous development.
Koji Takagi, G. S. P. Castle, Manabu Takeuchi, "Analysis of Imaging Density Degradation by Dynamics of Toner Charging and Mass Transfer in the Toner Development Process" in Journal of Imaging Science and Technology, 2005, pp 196 - 203, https://doi.org/10.2352/J.ImagingSci.Technol.2005.49.2.art00012