CHARGE CONTROL AGENTS AND TRIBOELECTRICALLY-ADJUSTED PIGMENTS IN ELECTROPHOTOGRAPHIC TONER

In electrophotographic printing systems the print quality is strongly influenced by charge control agents (CCAs) and organic pigments used i n the toner (electronic ink). Quaternary ammonium salts as CCAs exhibi t a large potential both for positive and negative applications. Their triboelectric efficiency could be adjusted by varying chemical consti tution and controlling solid-state parameters. Organic pigments provid e the color of the toner. Additionally, they exhibit a certain triboel ectric influence depending on their chemical constitution and solid-st ate properties. Low electrostatic influence together with appropriate ''coloristic properties'' (tinctorial strength, shade, transparency) a re necessary. A specially-designed yellow benzimidazolone pigment meet s these requirements. Both toner key ingredients-CCAs and pigments-hav e to be optimally dispersed into the polymer matrix (so-called binder or resin) in order to develop their desired electrostatic and colorist ic properties. Finally, they work together perfectly if the optimum co loristic and electrostatic properties are fulfilled and if the appropr iate process conditions (dispersion) are employed.