Abstract Particles of externally added charge control agent (EA-CCA) were prepared by means of a coacervation process and their effects on toner charge were investigated. The EA-CCA particles comprised silica core particles of 110 nm diameter and CCA molecules adhered to
the core surface. Four kinds of negative charge control agent (CCA), namely a boron complex (N-1), a zinc complex (N-2), an iron complex (N-3), and a styrene‐acrylate copolymer with sulfonic acid (N-4), were prepared as EA-CCAs. The tribo-charge of the mixture of model toner and EA-CCA
was measured using the blow-off method. The CCA concentration range was up to 1 μmol/g with respect to the model toner. In both the N-1 and N-3 experiments, the maximum tribo-charge values appeared around 0.01 μmol/g of CCA concentration. On the other hand, in both the N-2
and N-4 experiments, the tribo-charge was increased with increasing CCA concentration. The CCAs were classified into two types. One was the low concentration type, N-1 and N-3, and the other was the high concentration type, N-2 and N-4. The CCA efficiency on tribo-charge was different between
the two types of CCA. Low concentration type CCAs were effective in the low concentration region. They had no effect in the high concentration region. High concentration type CCAs were effective in the high concentration region. They still had a small effect in the low concentration region.