Device for enhancing transport of proper polarity toner in direct electrostatic printing

A direct electrostatic printing device for printing an image onto an image receiving substrate, said printing device comprising:

• a toner source;
• a toner carrier;
• a transfer member which receives toner particles from said toner source, said transfer member being separated from said toner carrier by a migration gap, said toner particles including toner particles of a predetermined charge polarity and toner particles of an opposite charge polarity;
• a voltage source connected to provide an electrical voltage potential between said transfer member and said toner carrier, said electrical voltage potential selected to cause toner particles having said predetermined charge polarity to be attracted across said migration gap from said transfer member to said toner carrier without attracting toner particles of said opposite charge polarity;
• and
• a printhead structure onto which an image is defined by an electric field pattern, wherein toner particles are transferred from said toner carrier to said image receiving substrate under control of said electric field pattern on said printhead structure.