EP0778135A2 - Electrostatic ink jet recording device - Google Patents
Electrostatic ink jet recording device Download PDFInfo
- Publication number
- EP0778135A2 EP0778135A2 EP96119562A EP96119562A EP0778135A2 EP 0778135 A2 EP0778135 A2 EP 0778135A2 EP 96119562 A EP96119562 A EP 96119562A EP 96119562 A EP96119562 A EP 96119562A EP 0778135 A2 EP0778135 A2 EP 0778135A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode
- ink
- counter electrode
- toner particles
- record
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
- B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
- B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
- B41J2002/061—Ejection by electric field of ink or of toner particles contained in ink
Landscapes
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
- Accessory Devices And Overall Control Thereof (AREA)
- Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
Abstract
Description
- The present invention relates to an electrostatic ink jet recording device and, more particularly, to an electrostatic ink jet recording device of the type electrostatically depositing toner particles contained in liquid ink on a recording medium and thereby recording a dot on the medium.
- Nonimpact type recording devices are attracting increasing attention because they produce only negligible noise during printing. Among them, an ink jet recording device is capable of recording an image even on a plain paper at high speed with a simple configuration. One of conventional ink jet recording devices uses ink consisting of a carrier liquid and charged toner particles dispersed therein. In this kind of recording device, a voltage is applied to a designated record electrode and a counter electrode facing the record electrode with the intermediary of a paper transport path, forming an electric field between the two electrodes. The electric field causes the toner particles to fly in the form of a drop and record a dot on the paper.
- However, the conventional recording device of the kind described has the following problem. While the paper or similar recording medium is conveyed, it is often charged due to friction acting between it and another paper, friction acting between the paper and conveyor rollers, etc. The charge deposited on the paper weakens the electric field formed between the record electrode and the counter electrode, and thereby prevents an electrostatic force intense enough to eject the toner particles from being attained. This obstructs the stable ejection of toner particles, i.e., stable printing operation.
- It is therefore an object of the present invention to provide an electrostatic ink jet recording device insuring the stable ejection of toner particles toward a recording medium.
- An electrostatic ink jet recording device of the present invention includes an ink chamber storing liquid ink containing charged toner particles. An ejection opening or slit is formed in one end portion of the ink chamber. An electrophoresis electrode is positioned at the other end portion of the ink chamber facing the one end portion. A plurality of record electrodes are arranged in parallel in the ejection opening. A counter electrode faces the record electrodes with the intermediary of a path for transporting a recording medium. Discharging means is located upstream of the counter electrode with respect to the intended direction of medium transport. The discharging means dissipates any undesirable charge deposited on the recording medium before the medium reaches the counter electrode.
- The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings in which:
- FIG. 1A is a front view of a conventional electrostatic ink jet recording device, particularly its head assembly;
- FIG. 1B is a section along line C-C of FIG. 1A;
- FIG. 1C is a side elevation of the conventional recording device;
- FIG. 2 is a perspective view showing an electrostatic ink jet recording device embodying the present invention, particularly its head assembly;
- FIG. 3A is a view of the embodiment as seen in a direction B shown in FIG. 2; and
- FIG. 3B is an enlarged view of a portion A shown in FIG. 3A.
- To better understand the present invention, a brief reference will be made to a conventional electrostatic ink jet recording device, particularly its head assembly, shown in FIGS. 1A-1C. As shown, the head assembly, generally 101, has an
ink chamber 113 delimited by alower plate 110, aside wall 111, and anupper plate 112. A pump, not shown, constantly circulates ink in theink chamber 113 viaports side wall 111 and plays the role of a gap for forming an ink meniscus. Arecord electrode 102 is disposed in theslit 109 and so positioned as to slightly protrude outward from theslit 109. The outermost end of therecord electrode 102 is sharpened. Therecord head 102 is coated with an insulating material and insulated from the ink thereby. - An
electrophoresis electrode 105 surrounds theink chamber 113 at three sides where therecord electrode 102 is absent. Theelectrophoresis electrode 105 is partly disposed in thechamber 113 and held in electrical contact with the ink. A driver, not shown, applies a high-voltage pulse to therecord electrode 102 in the event of recording. A counter electrode, not shown, is positioned on the imaginary extension of therecord electrode 102 and connected to ground via a paper transport path, not shown. The ink consists of a petroleum-based organic solvent (isoparaffin) and toner particles dispersed in the solvent. The toner particles are apparently charged to the positive polarity by zeta potential beforehand. - In operation, a bias voltage of the same polarity as the charge deposited on the toner particles is applied to the
electrophoresis electrode 105, causing the toner particles in the ink to collect densely at theslit 109 due to electrophoresis. Subsequently, a high-voltage pulse of the same polarity as the charge of the toner particles is applied to therecord electrode 102. As a result, an electric field is formed between therecord electrode 102 and the counter electrode. The electric field concentrates around the sharp tip of therecord electrode 102 and extends toward the counter electrode with high intensity. The toner particles charged by zeta potential beforehand and forming an ink meniscus is pulled by the counter electrode due to a Coulomb's force derived from the above electric field. When the Coulomb's force overcomes the surface tension of the ink, the toner particles fly toward the counter electrode in the form of a mass or drop. The toner particles forming the drop deposit on a paper or similar recording medium positioned between thehead 101 and the counter electrode, forming a dot on the paper. The high-voltage pulse to be applied to therecord electrode 102 is controlled in accordance with print data so as to form a desired image. - Only the toner particles are mainly consumed at the time of recording. Therefore, just after the ejection of the toner particles toward the recording medium, the toner content of the ink is lowered around the
record electrode 102. However, the high voltage constantly applied to theelectrophoresis electrode 105 causes the toner particles to migrate from theelectrode 105 toward theelectrode 102 due to electrophoresis. This allows only the toner particles to be replenished to around theelectrode 102. Particularly, theelectrode 102 is insulated from the ink. Therefore, when the potential distribution in theink chamber 113 reaches equilibrium due to the migration of the charged toner particles, no more particles are replenished to the above position. - The conventional recording device with the above head assembly has the previously stated problem left unsolved.
- Referring to FIGS. 2, 3A and 3B, an electrostatic ink jet recording device embodying the present invention, particularly its head assembly, will be described. As shown, the head assembly, generally 1, has an
ink chamber 10 storingink 11 containing charged toner particles. A slit or ejection opening 14 is formed in one end of theink chamber 10. An electrophoresis electrode 9 is positioned at the other end of theink chamber 10 facing theslit 14. Arecord electrode 12 is disposed in theslit 14. Acounter electrode 2 faces therecord electrode 12 with the intermediary of a paper transport path H. Discharging means 3 for discharging a paper orsimilar recording medium 4 is positioned upstream of thecounter electrode 2 with respect to an intended direction of paper transport D (FIG. 2). - The head assembly 1 is mounted on a
carriage 5 movable back and forth in a direction E (FIG. 2) perpendicular to the direction of paper transport D. The head assembly 1 is implemented as a serial print head and has its outside walls mainly formed of a dielectric material. Thecarriage 5 is movably mounted on aguide shaft 5A. Theink 11 consists of a petroleum-based organic solvent (isoparaffin) and a charge control agent and toner particles dispersed in the solvent. The toner refers to fine colored particles of thermoplastic resin. Again, the toner is apparently charged to the positive polarity by zeta potential. A pump or similar pressure source, not shown, constantly circulates the ink in theink chamber 10 via aninlet port 6 and anoutlet port 7. - Specifically, as shown in FIG. 3B, a plurality of
elongate record electrodes 12 are arranged in parallel at intervals corresponding to a desired number of dots. Eachrecord electrode 12 is implemented as an about 50 µm wide strip formed of Cu, Ni or similar conductive material and produced by electroforming. The portions of theelectrode 12 contacting theink 11 are coated with insulating resin. Preferably, the insulating resin should be hydrophilic in order to enhance affinity between the surface of theelectrode 12 and theink 11. The outer end of theelectrode 12 protrudes from theslit 14 by about 80 µm to 100 µm.Walls 13 are each positioned on therespective electrode 12. Thewalls 13 form slit-like passageways fine enough to cause capillarity to occur as soon as theink 11 is fed thereto. An ink meniscus is formed between each of thewalls 13 and the associatedelectrode 12. - The electrophoresis electrode 9 facing the
slit 14 is formed of metal or similar conductive material and held in direct contact with theink 11. The electrophoresis electrode 9 andrecord electrodes 12 are connected to a voltage drive section, not shown, by acable 8 implemented by a flexible print cable (FPC). The voltage drive section applies a high-voltage pulse of the same polarity as the charge of the toner particles to the electrode 9, and applies a high-voltage pulse of the same polarity as the charge of the toner particles to designated one of theelectrodes 12 at a record timing. - The
counter electrode 2 is connected to ground via a preselected resistance, so that great current does not flow between it and therecord electrode 12. Theelectrode 2 has a width corresponding to the width of thepaper 4 and serves as a platen at the same time. Thepaper 4 is conveyed in the direction D by roller pairs R. - The discharging means 3 is held in contact with the
paper 4 over the entire width of thepaper 4 while thepaper 4 is in transport. In the illustrative embodiment, the dischargingmeans 3 is implemented as a discharge brush extending in the widthwise direction of thepaper 4. The discharge brush may be replaced with a discharge brush roller or a conductive rubber blade, if desired. - The
guide shaft 5A on which thecarriage 5 is mounted, thecounter electrode 2 and the discharging means are each affixed to a particular part of the body of the recording device. - In operation, a voltage of the same polarity as the charge of the toner particles existing in the
ink 11 is applied to the electrophoresis electrode 9. As a result, a difference in potential occurs between the electrode 9 and therecord electrodes 12 set at a lower potential than the electrode 9. In this condition, the toner particles of theink 11 apparently play the role of a charge. Therefore, the toner particles are fed to the surfaces of the insulating resin covering therecord electrodes 12, in an amount great enough for the potential in theink 11 to become equal to the potential of the electrode 9. Consequently, theink 11 on theelectrodes 12 become equal in potential to the electrode 9. - As shown in FIG. 3A, the
paper 4 is conveyed upward along the path H by the roller pairs R. At this instant, the discharging means orbrush 3 is held in contact with the rear of thepaper 4. As a result, any charge undesirably deposited on thepaper 4 during transport is dissipated before thepaper 4 reaches the gap between thecounter electrode 2 and therecord electrodes 12. - Subsequently, a high-voltage pulse of the same polarity as the charge of the toner particles is applied to designated one of the
record electrodes 12, forming an electric field between the designatedelectrode 12 and thecounter electrode 2. When a Coulomb's force acting on the toner particles included in the ink meniscus overcomes the surface tension of the meniscus, the toner particles of the meniscus are ejected in the from of adrop 15 from theslit 14 toward thecounter electrode 15. Thedrop 15 deposits on thepaper 4 and records a dot thereon. - Just after the ejection of the
drop 15, the toner particles become short around therecord electrode 12. This again produces a difference in potential between the electrophoresis electrode 9 and therecord electrode 12. As a result, the toner particles are replenished to the surface of the resin covering theelectrode 12. Such a procedure is repeated to form a desired image on thepaper 4. - As stated above, even when the
paper 4 is undesirably charged during transport, thepaper 4 is successfully discharged before it reaches thecounter electrode 2. This insures a stable electric field between the record electrodes 1 2 and thecounter electrode 2, i.e., the stable ejection of thedrop 15 at the time of recording. - While the illustrative embodiment has concentrated on a serial print head, it may, of course, be implemented as a line print head, if desired.
- In summary, in accordance with the present invention, discharging means is positioned upstream of a counter electrode with respect to an intended direction of paper transport. Therefore, even when a paper is undesirably charged during transport, the paper is successfully discharged before it reaches the
counter electrode 2. This insures a stable electric field between record electrodes and the counter electrode, i.e., the stable ejection of a drop at the time of recording.
Claims (4)
- An electrostatic ink jet recording device comprising:an ink chamber storing liquid ink containing charged toner particles;an ejection opening formed in one end portion of said ink chamber;an electrophoresis electrode positioned at the other end portion of said ink chamber facing said one end portion;a plurality of record electrodes arranged in parallel in said ejection opening;a counter electrode facing said plurality of record electrodes with the intermediary of a path for transporting a recording medium; anddischarging means located upstream of said counter electrode with respect to an intended direction of medium transport, for dissipating any charge undesirably deposited on the recording medium during transport.
- A device as claimed in claim 1, wherein said discharging means comprises a discharge brush.
- A device as claimed in claim 1, wherein said discharging means comprises a discharge brush roller.
- A device as claimed in claim 1, wherein said discharging means comprises a conductive rubber plate.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP32011295 | 1995-12-08 | ||
JP32011295A JP2783227B2 (en) | 1995-12-08 | 1995-12-08 | Electrostatic inkjet recording device |
JP320112/95 | 1995-12-08 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0778135A2 true EP0778135A2 (en) | 1997-06-11 |
EP0778135A3 EP0778135A3 (en) | 1997-10-22 |
EP0778135B1 EP0778135B1 (en) | 1999-09-15 |
Family
ID=18117839
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19960119562 Expired - Lifetime EP0778135B1 (en) | 1995-12-08 | 1996-12-05 | Electrostatic ink jet recording device |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0778135B1 (en) |
JP (1) | JP2783227B2 (en) |
DE (1) | DE69604267T2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0779155A3 (en) * | 1995-12-14 | 1997-11-12 | Nec Corporation | Ink jet print head |
EP1522410A1 (en) * | 2003-09-24 | 2005-04-13 | Fuji Photo Film Co., Ltd. | Ink jet recording apparatus |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1178024A (en) * | 1997-09-01 | 1999-03-23 | Matsushita Electric Ind Co Ltd | Ink jet recorder |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2028596B (en) * | 1978-05-26 | 1983-02-16 | Lucas Industries Ltd | Apparatus for removing electro-static charge from an aircraft windscreen |
JPS6157343A (en) * | 1984-08-29 | 1986-03-24 | Toshiba Corp | Ink jet recording equipment |
US4918464A (en) * | 1988-11-25 | 1990-04-17 | Dai Nippon Insatu Kabushiki Kaisha | Heat-sensitive image transfer type printing apparatus |
JPH03147648A (en) * | 1989-11-02 | 1991-06-24 | Ricoh Co Ltd | Paper feeding device for image forming device |
EP0450402A3 (en) * | 1990-03-20 | 1992-01-22 | Mita Industrial Co., Ltd. | Printer with a static electricity eliminator and a taking-up means for an ink ribbon slack |
JPH0545952A (en) * | 1991-08-16 | 1993-02-26 | Minolta Camera Co Ltd | Image forming cartridge |
AU664404B2 (en) * | 1991-12-18 | 1995-11-16 | Tonejet Limited | Method and apparatus for the production of discrete agglomerations of particulate matter |
JPH06202497A (en) * | 1992-12-29 | 1994-07-22 | Canon Inc | Image forming device |
-
1995
- 1995-12-08 JP JP32011295A patent/JP2783227B2/en not_active Expired - Fee Related
-
1996
- 1996-12-05 EP EP19960119562 patent/EP0778135B1/en not_active Expired - Lifetime
- 1996-12-05 DE DE1996604267 patent/DE69604267T2/en not_active Expired - Fee Related
Non-Patent Citations (1)
Title |
---|
None |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0779155A3 (en) * | 1995-12-14 | 1997-11-12 | Nec Corporation | Ink jet print head |
US5801730A (en) * | 1995-12-14 | 1998-09-01 | Nec Corporation | Ink jet print head having a projecting ejection electrode |
EP1522410A1 (en) * | 2003-09-24 | 2005-04-13 | Fuji Photo Film Co., Ltd. | Ink jet recording apparatus |
US7300139B2 (en) | 2003-09-24 | 2007-11-27 | Fujifilm Corporation | Ink jet recording apparatus using charged fine particle-containing ink |
Also Published As
Publication number | Publication date |
---|---|
JP2783227B2 (en) | 1998-08-06 |
DE69604267T2 (en) | 2000-05-11 |
EP0778135A3 (en) | 1997-10-22 |
JPH09156110A (en) | 1997-06-17 |
DE69604267D1 (en) | 1999-10-21 |
EP0778135B1 (en) | 1999-09-15 |
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