A charge control mechanism of charge control agents (CCAs) has been proposed in the present investigation that assumes an appreciable temperature increase at the "toner/carrier" interface due to triboelectrification. A further assumption is that the CCA is present on the surface of both toner and carrier. Because of local heating, the electrical conductivity of CCAs is increased remarkably to give a conductive channel, through which the carrier flow occurs effectively to charge the toner. These two assumptions have experimentally been verified. Especially, local heating of up to ∼100 °C has been confirmed by using a pigment marker that changes its color from black to red. Around this temperature, the electrical conductivity of CCAs is also found to increase significantly by one to three orders of magnitude as compared with that at room temperature.
J. Mizuguchi, A. Hitachi, Y. Sato, K. Uta, "Study on the Charge Control Mechanism of Charge Control Agents" in Journal of Imaging Science and Technology, 2008, pp 30506-1 - 30506-5, https://doi.org/10.2352/J.ImagingSci.Technol.(2008)52:3(030506)