Patent ID: 6012802
Filing Date: 2000-01-11
Classification: B41J,G03G

Abstract:
A method for direct electrostatic printing in a system having:a receiving member substrate having a front side and a back side opposite said front side; andan electrostatic printing device for producing a toner image having a variable density on said front side of said receiving member substrate, said printing device having:a printhead structure facing said front side of said receiving member substrate, said printhead structure having a back side facing said front side of said receiving member substrate and a front side opposite said back side, said printhead structure having a plurality of apertures and corresponding galvanically isolated control print electrodes disposed therearound on the back side of the printhead structure, each of said control print electrodes being coupled to a power supply providing a variable voltage V.sub.CP having a value between a first voltage level V.sub.CP0 and a second voltage level V.sub.CPn ;toner delivery means disposed at said front side of said printhead structure for providing charged toner particles;means for generating an electrical field for propelling the toner particles through said printhead structure and towards said receiving member substrate; anda receiving member support facing said back side of said receiving member substrate, said support having a front side facing said back side of said receiving member substrate and a back side opposite said front side of said support, said support having a plurality of galvanically isolated control back electrodes, each of said control back electrodes having a center which is aligned with one of said apertures, each of said control back electrodes being arranged in a one to one relationship with a corresponding one of said control print electrodes and being coupled to a power supply providing a variable voltage V.sub.CB having a value between a third voltage level V.sub.CBO and a fourth voltage level V.sub.CBn, wherein said voltage levels V.sub.CPO and V.sub.CBO are for printing a maximum density D.sub.max and said voltage levels V.sub.CPn and V.sub.CBn are for printing a minimum density D.sub.min ;said method comprising the steps of:providing said toner particles proximate said apertures of said printhead structure by said toner delivery means;propelling a portion of the toner particles through said apertures and towards said receiving member substrate so as to print the toner image at said minimum density D.sub.min, said propelling step comprising the steps of:supplying at least one of said control back electrodes with said variable voltage V.sub.CB =V.sub.CBn /2; andsupplying a corresponding at least one of said control print electrodes with said variable voltage V.sub.CP =V.sub.CPn /2.