US 4792860 A In a method of printing on a printing medium a
variable thickness ink dot pattern representing an original
image in response to an incoming digital data stream, a printing
member, e.g. a cylinder, is formed which defines a multiplicity
of discrete, independently electrically chargable capacitor
microcells adjacent to a printing surface of that member.
Selected ones of the microcells are activated in accordance with
the incoming data stream so that the activated microcells are
geometrically related to the dots in the pattern to be printed.
Then, electrical charges are deposited on the microcells
selected for activation at controlled variable coulombic charge
levels to create at the printing surface, localized electrical
fields of various strengths that are proportional to the print
densities desired for the related dots in the pattern to be
printed. Following this, the printing surface is contacted by a
two-component, voltage sensitive, thermoplastic ink whereby ink
colorant, under the influence o