Toner transfer: Effects of size polydispersity

Toned images comprised of monodisperse, spherical toner particles, having diameters of either 2 mu m or 5 mu m or of blends thereof were electrostatically transferred from an organic photoreceptor to either paper or film receivers. It was found that the transfer efficiency of the images made with the monodisperse toners was quite high and the image quality quite good. However, even small amounts of the 5 pm toner significantly impeded the transfer of the 2 mu m, resulting in much poorer transfer efficiency and a large increase in mottle and granularity. Mathematical analysis shows that the maximum electrostatic field that can be applied prior to the onset of ionization is too small to remove the toner particles from the photoreceptor. Rather, the adhesive forces holding the toner to the photoreceptor must be partially offset by comparable adhesive forces between the toner particles and the receiver for transfer to occur.