7. Toners for electrophotography

7.1 Brief description of the process

Along with inkjet, electrophotography is the most important digital printing process. In this process, a latent image (intermediate and temporarily invisible) is formed on a cylinder coated with a photoconductive material. This photoconductor is insulating in the dark. It undergoes uniform precharging, and then, under the effect of a light beam, certain zones of the photoconductor are discharged. The latent image thus formed is revealed using a toner (powder) with the opposite charge to that of the photoconductor. The developed image is then transferred to the print substrate, where it is fixed: under the effect of a rise in temperature (up to 120-140°C), the toner particles become viscous fluids, enabling them to spread out and, depending on their...