| abstract |
An electrophotographic coating composition comprising finely-divided photoconductive perylene pigment dispersed in a solvent solution of polymeric binder is prepared by the steps of (1) milling a perylene pigment with milling media comprising inorganic salt and non-conducting particles under shear conditions in the substantial absence of the solvent to provide pigment having a particle size up to 0.2 micrometer, (2) continuing the milling at higher shear at a temperature up to about 50° C., to achieve a perceptible color change of the pigment particles, (3) rapidly reducing the temperature of the milled pigment by at least 10° C., (4) separating the milled pigment from the media and (5) mixing the milled pigment with the solvent solution of polymeric binder to form the coating composition. A very high degree of dispersion of photoconductive perylene pigment in solvent solution of polymeric binder is achieved by this method. |