초록 ▼

An ion generator for the formation of electrostatic images, including two electrodes at opposite faces of a solid dielectric member, using a threshold multiplexing principle for the drive circuit. The apparatus provides a drive signal to each electrode to generate ions in an air region adjacent one

An ion generator for the formation of electrostatic images, including two electrodes at opposite faces of a solid dielectric member, using a threshold multiplexing principle for the drive circuit. The apparatus provides a drive signal to each electrode to generate ions in an air region adjacent one of the electrodes, which ions are extracted for electrostatic imaging. Two drive signals each consisting of a sinusoidal alternating potential, out of phase by 180°, intermittently induce the production and extraction of ions. Other time-varying potentials of like electrical characteristics may be used, providing a number of operating advantages. The ion generator produces ions only during print periods, and requires reduced power to achieve given ion outputs. The control electrode may be partially encapsulated to limit the discharge region. Drive circuitry such as low source impedance gated oscillators, or other low impedance drivers, reduce capacitive "cross-talk" in a multielectrode device.

대표청구항 ▼

1. Electrostatic imaging apparatus comprising: a solid dielectric member; a first electrode adjacent the solid dielectric member; a second electrode adjacent an opposite portion of the solid dielectric member; a further electrode member; a first time-varying potential applied between said firs

1. Electrostatic imaging apparatus comprising: a solid dielectric member; a first electrode adjacent the solid dielectric member; a second electrode adjacent an opposite portion of the solid dielectric member; a further electrode member; a first time-varying potential applied between said first electrode and the further electrode member; and a second time-varying potential applied between said second electrode and said further electrode member, wherein the first and second time-varying potentials provide a potential difference between the first and second electrodes to selectively generate ions in a region adjacent the first electrode and the solid dielectric member, and wherein ions are extracted from said region in response to said first potential to form an electrostatic image. 2. Apparatus as defined in claim 1 wherein the first and second time-varying potentials comprise a direct current bias potential plus a time-varying component. 3. Apparatus as defined in claim 2 wherein the first and second potentials comprise periodically varying waveforms. 4. Electrostatic imaging apparatus comprising: a solid dielectric member; a first electrode adjacent the solid dielectric member; a second electrode adjacent an opposite portion of the solid dielectric member; a further electrode; a first time-varying potential applied between said first electrode and the further electrode; and a second time-varying potential applied to said further electrode; the first and second time-varying potentials comprising a direct current bias and sinusoidally time-varying potentials of like amplitude which are 180° out of phase; wherein the first and second time-varying potentials provide a potential difference between the first and second electrodes to selectively generate ions in a region adjacent the first electrode and the solid dielectric member, and wherein ions are extracted from said region in response to said first potential to form an electrostatic image. 5. Apparatus as defined in claim 2 wherein the time-varying components of the first and second potentials each comprise a series of pulses. 6. Electrostatic imaging apparatus comprising: a solid dielectric member; a first electrode adjacent the solid dielectric member; a second electrode adjacent an opposite portion of the solid dielectric member; a further electrode; a first time-varying potential applied between said first electrode and the further electrode; and a second time-varying potential applied to said further electrode; the first and second time-varying potentials each comprising a direct current bias and a time-varying component in the form of a series of pulses, which are of like amplitude and opposing polarities for the first and second potentials. 7. Apparatus as defined in claim 2 wherein the bias potential is of an amplitude which avoids arcing between either of the first and second electrodes, and the further electrode member. 8. Apparatus as defined in claim 1, comprising a plurality of first and second electrodes in a matrix array, with ion generation regions at matrix crossover points, and further comprising means for multiplexing said first and second potentials to generate ions at selected ion generation regions. 9. Electrostatic imaging apparatus comprising: a solid dielectric member; a first electrode adjacent the solid dielectric member; a second electrode adjacent an opposite portion of the solid dielectric member; a further electrode; a first time-varying potential applied between said first electrode and the further electrode; and a second time-varying potential applied to said further electrode; wherein the first and second time-varying potentials provide a potential difference between the first and second electrodes to selectively generate ions in a region adjacent the first electrode and the solid dielectric member; further comprising a plurality of first and second electrodes in a matrix array with ion generation regions at matrix crossover points, and including means for multiplexing said first and second potentials to generate ions at selected ion generation regions by selectively altering the phase relationship between predetermined first and second potentials. 10. Apparatus as defined in claim 1 wherein said first and second potentials are produced by low impedance sources. 11. Improved electrostatic imaging apparatus of the type including first and second electrodes at opposite sides of a solid dielectric member, with a time-varying potential between the electrodes to produce electrostatic discharges in an air region adjacent the first electrode and the solid dielectric member, and an extraction potential between the first electrode and a further electrode member to extract ions from said air region and form an electrostatic image, wherein the improvement comprises means for producing said time-varying potential and extraction potential, comprising: a first time-varying potential applied between said first electrode and said further electrode member; and a second time-varying potential applied to said second electrode, wherein said first and second potentials provide a time-varying potential difference between said first and second electrodes to selectively generate ions in said air region, said first potential acting to extract these ions. 12. Apparatus as defined in claim 11 wherein the first and second time-varying potentials comprise a direct current bias potential plus a time-varying component. 13. Apparatus as defined in claim 11 wherein the first and second potentials comprise periodically varying waveforms. 14. Apparatus as defined in claim 11, of the type comprising a plurality of first and second electrodes in a matrix array, with ion generation regions at matrix crossover points, further comprising means for multiplexing said first and second potentials to generate ions at selected ion generation regions. 15. Apparatus as defined in claim 11 wherein said first and second potentials are produced by low impedance sources. 16. A method for the formation of electrostatic images comprising the steps of: applying a first time-varying potential to a first electrode adjacent a solid dielectric member, applying a second time-varying potential to a second electrode adjacent an opposite portion of said solid dielectric member, and coordinating said first and second time-varying potentials to selectively generate ions in a region at a junction of one of the electrodes and the solid dielectric member. 17. A method as defined in claim 16, wherein said first and second time-varying potentials comprise direct current bias potentials plus a time-varying component. 18. A method as defined in claim 16, wherein said first and second time-varying potentials comprise periodically varying waveforms which intermittently generate ions. 19. A method as defined in claim 17 wherein the time-varying components of said first and second time-varying potentials comprise waveforms selected from the group: sinusoidally alternating potentials with an essentially 180° phase difference; periodic pulses; and periodic pulses of like amplitude and opposing polarities. 20. A method for the formation of electrostatic images comprising the steps of: applying a first time-varying potential between a first electrode adjacent a solid dielectric member and a further electrode, applying a second time-varying potential to a second electrode adjacent an opposite portion of said solid dielectric member, and coordinating said first and second time-varying potentials by selectively varying their phase relationship to selectively generate ions in a region at a junction of the first electrode and the solid dielectric member, and extracting said ions under the influence of said first potential to form an electrostatic image. 21. The method of generating ions which comprises applying separate oppositely varying signals to opposite electrodes which are separated by a solid dielectric.