An improved ion projection printing apparatus, for imaging on the front surface of a charge receptor sheet with an imagewise charging device and for depositing a counter-charge upon the rear surface of the charge receptor sheet with another charging device concurrently with and spatially opposed to the imagewise charging device.

An electrographic printing system moves a dielectric imaging member past a charge transfer print cartridge or bulk charging source, and a landing electrode arrangement directs charged particles with enhanced precision to dot positions on the imaging member. The arrangement includes a central, point-like, target electrode and a field electrode that, together with the target electrode, provides a corrective electric field component to form a focusing, or at least a non-diverging field over the target position. Field deflection artifacts such as "venetian blinding" are substantially corrected. The target electrodes are located behind the imaging member, in registry with the charging cartridge which is opposed to the other side of the member. Different landing electrode arrangements may include one- or two-dimensional arrays of targeting electrodes and are adapted to either bulk or pointwise arrays of charge emitter. Two dimensional imaging may be performed by timed actuation of landing electrodes using a charged particle source that is always ON, by multiplexing the print cartridge electrodes, or multiplexing some electrodes of each of the two structures at a lower rate. A self-limiting feedback loop assures charge dot saturation without image distortion.

A method and apparatus provide enhanced longevity of the ion cartridge in an MIDAX (silent electric discharge) electrostatic imaging processing system. The conventional ion cartridge comprises a solid dielectric with driver and control electrodes on opposite sides, the second electrode defining a discharge region at the junction of the edge surface of the solid dielectric member. Alternating current is supplied to the electrodes to induce charged particle production electrical discharges. Gas is supplied to the discharge region to replace the vast majority of the air during charge particle generation. The gas is a mixture consisting essentially of nitrogen with an amount of argon, neon, xeon, or krypton effective to provide a catalyst for nitrogen ionization while preventing arcing. Typically, the gas is a mixture of nitrogen and argon in a ratio of about 5 to 1 to about 20 to 1 (e.g. about 10 to 1), with the total gas flow rate to the discharge region about 4.75-6.25 cubic feet per hour. The gas is supplied to the area between the ion cartridge and an imaging drum by a pair of gas manifolds at opposite ends of the drum, and a pair of spray tubes having numerous perforations along their length extending between the gas manifolds. Regulators precisely control the amount of nitrogen and argon supplied to the gas manifolds.

Apparatus for information transfer and including a dielectric element having generally opposite first and second surfaces, an information bearing voltage signal being associated with the first surface and an information bearing charge pattern being associated with the second surface, device for applying a flow of charges to the second surface, the flow of charges being operative to transfer information between the first and second surfaces.

An apparatus for selectively setting the distance between the write head of an electrographic printing apparatus and a recording medium in combination with the use of a gas, present in the gap between the medium and the write head whereby the gas has a Paschen curve minimum lower than the Paschen curve for air. The combination of increasing the distance of the head from the medium along with the use of a gas as specified decreases the amount of flare while decreasing dropout and maintaining image density.