Inventors:
Dale D. Russell - Boise ID
James G. Bearss - Boise ID
Assignee:
Hewlett-Packard Company - Palo Alto CA
International Classification:
G03G 9135
Abstract:
The invention is a positive charge director for liquid electrographic toners. The charge director comprises a very strongly chelating functional group covalently bonded in the resin coating or pigment component, or an intrinsic part of the pigment component, of the toner particle, and a very weakly associated, preferably ionic, molecule dispersed in the liquid phase to achieve charge separation. The strong chelation site on the resin is prepared, via well-known polymer chemistry. For the ionic molecule, preferred cations are those with no regulatory, health or environmental issues, such as K+, Na+, Ca. sup. 2+, Al. sup. 3+, Zn. sup. 2+, Zr. sup. 4+, Mg. sup. 2+, ammonium (NH. sub. 4 +), and organic cations. The chelate-containing resin is brought into dispersion with the liquid phase containing the ionic molecule. When this is done, the equilibria that compete for the cation are such that it is released from the ionic molecule and bound in the chelate.