Electrostatic printing system and method using ions and liquid aerosol toners

A method of electrostatic printing on a print receiving medium comprising:

• generating an ion stream;
• modulating the cross-sectional flow density of ions in the stream in accordance with a pattern to be reproduced to produce a modulated stream of ions;
• establishing an ion projection field for propelling the ions of a modulated ion stream thus formed toward the print receiving medium;
• and introducing a cloud of substantially uncharged liquid ink droplets having an average charge no greater than substantially 5 .times. 10.sup.-.sup.7 coulombs/m.sup.2 into the path of the modulated ion stream whereby the modulated ion stream selectively impinges upon and charges droplets in the cloud which are deposited on the print receiving medium by said projection field in accordance with a pattern to be reproduced.

In an apparatus for electrostatic printing including means for generating a directed stream of ions including an ion source and an electrode spaced from said ion source;

• means interposed in the ion stream for modulating the ion stream comprising a multilayered apertured modulating element spaced between said ion source and said electrode, said modulating element having at least a conductive layer and an insulative layer capable of supporting charge potentials of differing magnitude for establishing electrostatic lines of force within the apertures of the element for controlling passage of ions to form a modulated ion stream in accordance with a pattern to be reproduced;
• means for supporting and positioning a print receiving medium spaced from said modulating element between said modulating element and said electrode;
• means for establishing an electrical field between said ion source and said electrode encompassing said modulating element and the print receiving medium;
• and means for introducing a cloud of marking particles into the path of the modulated ion stream in the space between said modulating element and the positioned print receiving medium so that the modulated ion stream selectively impinges upon and charges the particles in the cloud which are propelled by said electrical field and deposited on the print receiving medium in accordance with a pattern to be reproduced;
• the improvement wherein said introducing means comprises means for generating a cloud of uncharged liquid ink droplets having an average charge no greater than substantially 5 .times. 10.sup.-.sup.7 coulombs/m.sup.2.