EP0771653A1 - Electrostatic ink jet recording apparatus - Google Patents
Electrostatic ink jet recording apparatus Download PDFInfo
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- EP0771653A1 EP0771653A1 EP96116324A EP96116324A EP0771653A1 EP 0771653 A1 EP0771653 A1 EP 0771653A1 EP 96116324 A EP96116324 A EP 96116324A EP 96116324 A EP96116324 A EP 96116324A EP 0771653 A1 EP0771653 A1 EP 0771653A1
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- European Patent Office
- Prior art keywords
- electrode
- recording apparatus
- jet recording
- ink jet
- opposing
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- 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.)
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- 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
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- 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
Definitions
- This invention relates to an electrostatic ink jet recording apparatus, and more particularly to an electrostatic ink jet recording apparatus in which a countermeasure against a voltage leak which may occur between an ejection electrode and an opposing electrode is provided.
- the electrostatic ink jet recording apparatus includes an ink chamber 52 in which conductive ink is filled, a plurality of ink jetting elements 56a communicated with the ink chamber 52, an ultrasonic oscillation application unit 57 for applying ultrasonic oscillations to the ink in the ink chamber 52, a first electrode 56 provided for each of the ink jetting elements 56a, a second electrode (back electrode) 60 located outside the ink chamber 52 in an opposing relationship to ink jet exits of the ink jetting elements 56a, and a high voltage pulse application unit 55 for applying a high voltage pulse corresponding to a recording signal between the first electrode 56 and the second electrode 60 while the ultrasonic oscillation application unit 57 is in an energized state to produce, between the first electrode 56 and the second electrode 60, an electrostatic field for causing ink drops to fly from the ink jet exits.
- the ink in the ink chamber 52 is oscillated by the ultrasonic oscillation application unit 57 to render unstable the configuration of an ink meniscus formed at each of the ink jet exits while the ink flying electric field is concentrated upon a local portion of the meniscus in order that the voltage required to be applied to the first electrode to cause the ink to fly may be reduced comparing with an ordinary application voltage thereby to prevent a voltage leak which may otherwise occur between the first electrode and the second electrode.
- the conventional electrostatic ink jet recording apparatus described above is disadvantageous in that, since an ultrasonic oscillator is required, the apparatus has a large size and a complicated structure accordingly and a high cost is required.
- the electrostatic ink jet recording apparatus is disadvantageous also in that, since an ink meniscus is rendered unstable in an unpredictable situation, stabilized ink discharging cannot be achieved. Further, even if an ultrasonic oscillator is used, the extent of reduction of a high voltage pulse to be applied to the first electrode is approximately 100 V to the utmost as apparent also from an example of experiment disclosed in the document mentioned above.
- the electrostatic ink jet recording apparatus is further disadvantageous in that, where the distance between the first electrode and the second electrode must be set short depending, for example, upon the thickness of a recording medium to be used, there is a fixed limitation to prevention of a voltage leak.
- an electrostatic ink jet recording apparatus comprising an ink chamber for accommodating ink in which charged toner particles are contained, a discharging exit communicated with the ink chamber and having an opening directed to the outside, an ejection electrode disposed in the discharging exit and having an end portion directed to the outside, an electrophoretic electrode mounted on side walls of the ink chamber such that the ejection electrode is located therein, an opposing electrode disposed in an opposing relationship to the discharging exit with a paper travel path interposed therebetween, a migration voltage source for applying a migration voltage to the electrophoretic electrode, and a discharging voltage source for applying a driving pulse voltage to the ejection electrode, the opposing electrode being formed from a conductive rubber roller having a high resistance value.
- the resistance value of the opposing electrode is equal to or higher than 1 M ⁇ .
- the opposing electrode being formed from a conductive rubber roller having a high resistance value, even if the potential difference between the ejection electrode and the opposing electrode exceeds the dielectric strength of the space between the ejection electrode and the opposing electrode by some cause, an excessive electric current which may otherwise be produced by a spark can be suppressed by the resistance of the opposing electrode. Consequently, the ejection electrode and the opposing electrode can be protected effectively from otherwise possible destruction by a spark with a comparatively inexpensive construction free from increase in size of the apparatus.
- the electrostatic ink jet recording apparatus may further comprise a resistor switch and a plurality of high resistors for being selectively connected to the opposing electrode by the resistor switch, the resistor switch and the plurality of high resistors being interposed between the opposing electrode and the ground.
- the plurality of high resistors may be at least three high resistors having different resistance values equal to or higher than 1 M ⁇ .
- one of the plurality of resistors is selectively connected to the ground side of the opposing electrode in accordance with the thickness of the recording medium to be used. Consequently, production of an excessive electric current upon leaking can be prevented effectively irrespective of the thickness of the recording medium to be used.
- an electrostatic ink jet recording apparatus comprising an ink chamber for accommodating ink in which charged toner particles are contained, a discharging exit communicated with the ink chamber and having an opening directed to the outside, an ejection electrode disposed in the discharging exit and having an end portion directed to the outside, an electrophoretic electrode mounted on side walls of the ink chamber such that the ejection electrode is located therein, an opposing electrode disposed in an opposing relationship to the discharging exit with a paper travel path interposed therebetween, a migration voltage source for applying a migration voltage to the electrophoretic electrode, a discharging voltage source for applying a driving pulse voltage to the ejection electrode, the opposing electrode being formed from a conductive rubber roller having a high resistance value, current measurement means for measuring a value of an electric current flowing to the opposing electrode, and measured current display means for displaying the value of the electric current measured by the current measurement means.
- the current value of the current flowing to the opposing electrode and measured by the current measurement means is displayed on the measurement current display unit, and if a voltage leak occurs between the ejection electrode and the opposing electrode, then this situation is displayed on the measured voltage display unit. Accordingly, when a leak is produced between the ejection electrode and the opposing electrode, it is possible to urge a user of the apparatus to take a suitable countermeasure quickly. Consequently, the electrostatic ink jet recording apparatus is advantageous in that otherwise possible damage to the ejection electrode and the opposing electrode after a leak occurs can be prevented.
- the electrostatic ink jet recording apparatus shown includes a recording head body 100 in which an ink chamber 2 in which ink 1 in the form of liquid which contains charged toner particles is accommodated is provided.
- the ink chamber 2 has a front wall 2a in which a discharging exit 4 is formed such that it is communicated with the ink chamber 2 and opened to the outside.
- the discharging exit 4 is formed as a very small slit.
- An ink supply port 14 is formed in one of the opposite side walls 2b of the ink chamber 2, and an ink emission port 13 is formed in the other side wall 2b.
- An ejection electrode 5 is provided in the ink chamber 2 and has an end portion projecting to the outside through the discharging exit 4.
- An electrophoretic electrode 8 is located on the outer side of the ink chamber 2 along outer faces of the opposite side walls 2b and a rear wall 2c of the ink chamber 2.
- the electrophoretic electrode 8 is connected to a migration voltage source 11 outside the ink chamber 2, and the ejection electrode 5 is connected to a discharging voltage source 12 outside the ink chamber 2.
- An opposing electrode 10 is located outside the ink chamber 2 in an opposing relationship to the discharging exit 4 with a paper travel path 9 interposed therebetween.
- the ink 1 is composed of fine particles of a colored thermoplastic resin called toner dispersed together with a charging control agent in a petroleum organic solvent (isoparaffin).
- the toner powder is apparently charged to the positive polarity by a zeta ( ⁇ ) potential.
- the ink chamber 2 is connected to an ink tank (not shown) via tubes (not shown) connected to the ink emission port 13 and the ink supply port 14 such that a negative pressure of approximately 1 cmH 2 O is applied to the ink 1 in the inside of the ink chamber 2 and the ink 1 is forced to circulate between the ink chamber 2 and the ink tank.
- the ejection electrode 5 is formed from a conductive material such as Cu or Ni by electroforming and has a width of approximately 50 ⁇ m.
- the ejection electrode 5 is positioned so that the end portion thereof projects over approximately 80 ⁇ m to 100 ⁇ m from the discharging exit 4 to the outside. Consequently, an ink meniscus 6 is formed between the projecting ink chamber 2 and the discharging exit 4 by a surface tension of the ink 1.
- a meniscus formation section 7 is formed from the discharging exit 4 and the ejection electrode 5.
- such meniscus formation section may otherwise be formed from a wire or a like element.
- the migration voltage source 11 applies a voltage having a same polarity as that of the zeta potential of the toner powder to the electrophoretic electrode 8.
- the discharging voltage source 12 applies a high voltage pulse having a same polarity as that of the toner powder to the ejection electrode 5 at a predetermined timing based on a recording signal.
- the opposing electrode 10 is formed from a conductive rubber roller having a high resistance value and is grounded.
- the resistance of the opposing electrode 10 is set to a value equal to or higher than 1 M ⁇ .
- a mechanism is provided for adjusting the distance between the opposing electrode 10 and the ejection electrode 5 among several stages in accordance with the thickness of a recording medium disposed along the paper travel path 9.
- a head-platen distance adjustment mechanism which is normally employed in a dot impact printer may be employed.
- toner particles are supplemented toward the discharging exit 4 by electric migration from the interior side of the ink chamber 2 so as to prepare for successive discharging. Meanwhile, an excessive amount of the ink 1 is discharged from the ink emission port 13. Those steps of operation are repeated to form a toner image on the recording medium P transported along the paper travel path 9. Then, the recording medium P having the toner image formed thereon is transported to and subject to thermal fixation by a fixing unit (not shown) similar to a fixing unit for electrophotographic recording.
- the opposing electrode 10 is a complete conductor and is grounded as in the conventional electrostatic ink jet recording apparatus described hereinabove, then if the distance between the ejection electrode 5 and the opposing electrode 10 is reduced shorter than a certain distance, a spark (voltage leak) is produced between the ejection electrode 5 and the opposing electrode 10. If a spark is produced, then metal portions of the ejection electrode 5 and the opposing electrode 10 may be melted by heat by the spark, resulting in failure in function as a head.
- the opposing electrode 10 is formed from a conductive rubber roller having a high resistance value, even if the potential difference between the ejection electrode 5 and the opposing electrode 10 exceeds the dielectric strength of the space between the ejection electrode 5 and the opposing electrode 10 by some cause, an excessive electric current which may otherwise be produced by a spark can be suppressed by the resistance of the opposing electrode 10. Consequently, the ejection electrode 5 and the opposing electrode 10 can be protected effectively from otherwise possible destruction by a spark with a comparatively inexpensive construction free from increase in size of the apparatus.
- FIGS. 3 to 5 there is shown another electrostatic ink jet recording apparatus to which the present invention is applied.
- the electrostatic ink jet recording apparatus shown is a modification to and has a common construction to that of the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2. Thus, overlapping description of the common construction is omitted herein to avoid redundancy.
- the electrostatic ink jet recording apparatus of the present embodiment is different from the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2 only in that it includes, between the opposing electrode 10 and the ground, a resistor switch 15 and a plurality of high resistors which are selectively connected to the opposing electrode 10 by the resistor switch 15.
- a resistor switch 15 and a plurality of high resistors which are selectively connected to the opposing electrode 10 by the resistor switch 15.
- three high resistors R1, R2 and R3 are provided and have different resistance values equal to or higher than 1 M ⁇ .
- the thickness of paper to be recorded is discriminated based on a result of adjustment of the gap or distance between the recording head body 100 and the opposing electrode 10 performed by an automatic gap adjustment mechanism (not shown), which is usually employed in a dot impact printer as a distance adjustment mechanism between a head body and an opposing electrode, and a main controller (not shown) of the electrostatic ink jet recording apparatus operates the resistor switch 15 based on the discrimination to automatically select an optimum one of the resistors R1, R2 and R3.
- the reason why the resistors are selectively used in response to the thickness of the recording medium is described.
- the distance from the extremity of the ejection electrode 5 to the surface of the recording medium must be set fixed, and since the recording medium is disposed in contact with the opposing electrode, it is necessary to adjust the distance between the ejection electrode 5 and the opposing electrode 10 based on the thickness of the recording medium to be used.
- the electrostatic ink jet recording apparatus of the present embodiment adopts the construction wherein the resistor to be used is switched in response to the thickness of the printing medium to prevent production of a spark.
- the resistor switch 15 is operated in accordance with the amount of the adjustment then, for example, by the main controller of the apparatus mentioned hereinabove so that one of the three resistors R1, R2 and R3 is selectively connected.
- the resistor R1 of 1 M ⁇ is selectively connected.
- the resistor R2 of 2 M ⁇ is selectively connected.
- the resistor P3 of 3 M ⁇ is selectively connected.
- the resistance values of the resistors R1, R2 and R3 must be set to optimum values for recording media of different thickness values in advance.
- the resistor switch 15 may alternatively be operated manually by an operator in accordance with the thickness of a recording medium to be used. In this instance, no particular measure is required for detecting the thickness of a recording medium.
- FIGS. 6 and 7 there is shown a further electrostatic ink jet recording apparatus to which the present invention is applied.
- the electrostatic ink jet recording apparatus shown is a modification to and has a common construction to that of the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2. Thus, overlapping description of the common construction is omitted herein to avoid redundancy.
- the electrostatic ink jet recording apparatus of the present embodiment is different from the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2 only in that it includes, for the opposing electrode 10, a current measuring instrument 16 for measuring the value of an electric current flowing to the opposing electrode 10 and a measurement current display unit 17 for displaying the current value measured by the current measuring instrument 16.
- the current measuring instrument 16 measures the value of an electric current flowing between the opposing electrode 10 and the ground and inputs to the measurement current display unit 17, for example, a voltage which varies in accordance with the measured current.
- the measurement current display unit 17 includes, for example, a level comparator not shown, and has a function of displaying, when the input voltage from the current measuring instrument 16 exhibits a level higher than a threshold level set in advance, a warning representing that a leak has occurred and generating an alarm.
- the current measuring instrument 16 measures such an electric current variation as illustrated in FIG. 8 and inputs a corresponding voltage signal to the measurement current display unit 17.
- the measurement current display unit 17 displays, on a display unit (not shown) thereof such as an operator panel, that a leak has occurred when the input voltage from the current measuring instrument 16 exceeds the preset threshold level, and generates an alarm. Consequently, the user can be urged to take a suitable countermeasure quickly. Accordingly, in addition to the advantages achieved by the electrostatic ink jet recording apparatus of the first embodiment, another advantage that otherwise possible damage to the ejection electrode 5 and the opposing electrode 10 after a leak occurs can be prevented is achieved.
- the threshold level set in the measurement current display unit 17 may be set to an intermediate value between an input voltage at which a leak occurs and another input voltage at which the electrodes are destroyed.
- the construction of the opposing electrode side in the electrostatic ink jet recording apparatus of the embodiments described above can be applied as it is also to conventional electrostatic ink jet recording apparatus wherein liquid ink is jetted directly to a recording medium to effect recording on the recording medium, and in this instance, similar advantages are achieved.
Abstract
Description
- This invention relates to an electrostatic ink jet recording apparatus, and more particularly to an electrostatic ink jet recording apparatus in which a countermeasure against a voltage leak which may occur between an ejection electrode and an opposing electrode is provided.
- Various electrostatic ink jet recording apparatus of the type mentioned are conventionally known, and one of such electrostatic ink jet recording apparatus is disclosed in Japanese Patent Laid-Open Application No. Heisei 5-212867 and shown in FIG. 9.
- Referring to FIG. 9, the electrostatic ink jet recording apparatus includes an
ink chamber 52 in which conductive ink is filled, a plurality ofink jetting elements 56a communicated with theink chamber 52, an ultrasonicoscillation application unit 57 for applying ultrasonic oscillations to the ink in theink chamber 52, afirst electrode 56 provided for each of theink jetting elements 56a, a second electrode (back electrode) 60 located outside theink chamber 52 in an opposing relationship to ink jet exits of theink jetting elements 56a, and a high voltagepulse application unit 55 for applying a high voltage pulse corresponding to a recording signal between thefirst electrode 56 and thesecond electrode 60 while the ultrasonicoscillation application unit 57 is in an energized state to produce, between thefirst electrode 56 and thesecond electrode 60, an electrostatic field for causing ink drops to fly from the ink jet exits. - The ink in the
ink chamber 52 is oscillated by the ultrasonicoscillation application unit 57 to render unstable the configuration of an ink meniscus formed at each of the ink jet exits while the ink flying electric field is concentrated upon a local portion of the meniscus in order that the voltage required to be applied to the first electrode to cause the ink to fly may be reduced comparing with an ordinary application voltage thereby to prevent a voltage leak which may otherwise occur between the first electrode and the second electrode. - However, the conventional electrostatic ink jet recording apparatus described above is disadvantageous in that, since an ultrasonic oscillator is required, the apparatus has a large size and a complicated structure accordingly and a high cost is required. The electrostatic ink jet recording apparatus is disadvantageous also in that, since an ink meniscus is rendered unstable in an unpredictable situation, stabilized ink discharging cannot be achieved. Further, even if an ultrasonic oscillator is used, the extent of reduction of a high voltage pulse to be applied to the first electrode is approximately 100 V to the utmost as apparent also from an example of experiment disclosed in the document mentioned above. Thus, the electrostatic ink jet recording apparatus is further disadvantageous in that, where the distance between the first electrode and the second electrode must be set short depending, for example, upon the thickness of a recording medium to be used, there is a fixed limitation to prevention of a voltage leak.
- It is an object of the present invention to provide an electrostatic ink jet recording apparatus of a small size and a simple construction wherein a voltage leak between an ejection electrode and an opposing electrode can be prevented.
- In order to attain the object described above, according to an aspect of the present invention, there is provided an electrostatic ink jet recording apparatus, comprising an ink chamber for accommodating ink in which charged toner particles are contained, a discharging exit communicated with the ink chamber and having an opening directed to the outside, an ejection electrode disposed in the discharging exit and having an end portion directed to the outside, an electrophoretic electrode mounted on side walls of the ink chamber such that the ejection electrode is located therein, an opposing electrode disposed in an opposing relationship to the discharging exit with a paper travel path interposed therebetween, a migration voltage source for applying a migration voltage to the electrophoretic electrode, and a discharging voltage source for applying a driving pulse voltage to the ejection electrode, the opposing electrode being formed from a conductive rubber roller having a high resistance value. Preferably, the resistance value of the opposing electrode is equal to or higher than 1 MΩ.
- With the electrostatic ink jet recording apparatus, since the opposing electrode being formed from a conductive rubber roller having a high resistance value, even if the potential difference between the ejection electrode and the opposing electrode exceeds the dielectric strength of the space between the ejection electrode and the opposing electrode by some cause, an excessive electric current which may otherwise be produced by a spark can be suppressed by the resistance of the opposing electrode. Consequently, the ejection electrode and the opposing electrode can be protected effectively from otherwise possible destruction by a spark with a comparatively inexpensive construction free from increase in size of the apparatus. Further, since only toner particles are discharged from within the liquid ink to effect recording, blurring on a recording medium or a like defect in terms of which conventional ink jet printing should be improved does not occur, and a high printing quality similar to that achieved by electrophotographic recording can be achieved.
- The electrostatic ink jet recording apparatus may further comprise a resistor switch and a plurality of high resistors for being selectively connected to the opposing electrode by the resistor switch, the resistor switch and the plurality of high resistors being interposed between the opposing electrode and the ground. In this instance, the plurality of high resistors may be at least three high resistors having different resistance values equal to or higher than 1 MΩ. In the electrostatic ink jet recording apparatus, one of the plurality of resistors is selectively connected to the ground side of the opposing electrode in accordance with the thickness of the recording medium to be used. Consequently, production of an excessive electric current upon leaking can be prevented effectively irrespective of the thickness of the recording medium to be used.
- According to another aspect of the present invention, there is provided an electrostatic ink jet recording apparatus, comprising an ink chamber for accommodating ink in which charged toner particles are contained, a discharging exit communicated with the ink chamber and having an opening directed to the outside, an ejection electrode disposed in the discharging exit and having an end portion directed to the outside, an electrophoretic electrode mounted on side walls of the ink chamber such that the ejection electrode is located therein, an opposing electrode disposed in an opposing relationship to the discharging exit with a paper travel path interposed therebetween, a migration voltage source for applying a migration voltage to the electrophoretic electrode, a discharging voltage source for applying a driving pulse voltage to the ejection electrode, the opposing electrode being formed from a conductive rubber roller having a high resistance value, current measurement means for measuring a value of an electric current flowing to the opposing electrode, and measured current display means for displaying the value of the electric current measured by the current measurement means.
- With the electrostatic ink jet recording apparatus, the current value of the current flowing to the opposing electrode and measured by the current measurement means is displayed on the measurement current display unit, and if a voltage leak occurs between the ejection electrode and the opposing electrode, then this situation is displayed on the measured voltage display unit. Accordingly, when a leak is produced between the ejection electrode and the opposing electrode, it is possible to urge a user of the apparatus to take a suitable countermeasure quickly. Consequently, the electrostatic ink jet recording apparatus is advantageous in that otherwise possible damage to the ejection electrode and the opposing electrode after a leak occurs can be prevented.
- The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference characters.
- FIG. 1 is a schematic plan view, partly in section, of an electrostatic ink jet recording apparatus to which the present invention is applied;
- FIG. 2 is a schematic side elevational view, partly in section, of the electronic ink jet recording apparatus shown in FIG. 1;
- FIGS. 3 to 5 are similar views but showing another electronic ink jet recording apparatus to which the present invention is applied;
- FIG. 6 is a schematic plan view, partly in section, of a further electrostatic ink jet recording apparatus to which the present invention is applied;
- FIG. 7 is a schematic side elevational view, partly in section, of the electrostatic ink jet recording apparatus shown in FIG. 6;
- FIG. 8 is a diagram illustrating a variation of an electric current measured by a current measuring instrument when a voltage leak occurs between an ejection electrode and an opposing electrode in the electrostatic ink jet recording apparatus shown in FIGS. 6 and 7; and
- FIG. 9 is a schematic sectional view showing a conventional electrostatic ink jet recording apparatus.
- Referring first to FIGS. 1 and 2, there is shown an electrostatic ink jet recording apparatus to which the present invention is applied. The electrostatic ink jet recording apparatus shown includes a
recording head body 100 in which an ink chamber 2 in whichink 1 in the form of liquid which contains charged toner particles is accommodated is provided. The ink chamber 2 has afront wall 2a in which adischarging exit 4 is formed such that it is communicated with the ink chamber 2 and opened to the outside. Thedischarging exit 4 is formed as a very small slit. Anink supply port 14 is formed in one of theopposite side walls 2b of the ink chamber 2, and anink emission port 13 is formed in theother side wall 2b. Anejection electrode 5 is provided in the ink chamber 2 and has an end portion projecting to the outside through thedischarging exit 4. - An
electrophoretic electrode 8 is located on the outer side of the ink chamber 2 along outer faces of theopposite side walls 2b and arear wall 2c of the ink chamber 2. Theelectrophoretic electrode 8 is connected to a migration voltage source 11 outside the ink chamber 2, and theejection electrode 5 is connected to adischarging voltage source 12 outside the ink chamber 2. Anopposing electrode 10 is located outside the ink chamber 2 in an opposing relationship to thedischarging exit 4 with apaper travel path 9 interposed therebetween. - In the electrostatic ink jet recording apparatus, the
ink 1 is composed of fine particles of a colored thermoplastic resin called toner dispersed together with a charging control agent in a petroleum organic solvent (isoparaffin). The toner powder is apparently charged to the positive polarity by a zeta (ζ) potential. - The ink chamber 2 is connected to an ink tank (not shown) via tubes (not shown) connected to the
ink emission port 13 and theink supply port 14 such that a negative pressure of approximately 1 cmH2 O is applied to theink 1 in the inside of the ink chamber 2 and theink 1 is forced to circulate between the ink chamber 2 and the ink tank. - The
ejection electrode 5 is formed from a conductive material such as Cu or Ni by electroforming and has a width of approximately 50 µm. Theejection electrode 5 is positioned so that the end portion thereof projects over approximately 80 µm to 100 µm from thedischarging exit 4 to the outside. Consequently, anink meniscus 6 is formed between the projecting ink chamber 2 and thedischarging exit 4 by a surface tension of theink 1. Here, ameniscus formation section 7 is formed from thedischarging exit 4 and theejection electrode 5. However, such meniscus formation section may otherwise be formed from a wire or a like element. - The migration voltage source 11 applies a voltage having a same polarity as that of the zeta potential of the toner powder to the
electrophoretic electrode 8. Thedischarging voltage source 12 applies a high voltage pulse having a same polarity as that of the toner powder to theejection electrode 5 at a predetermined timing based on a recording signal. - The
opposing electrode 10 is formed from a conductive rubber roller having a high resistance value and is grounded. Here, the resistance of theopposing electrode 10 is set to a value equal to or higher than 1 MΩ. Further, though not shown, a mechanism is provided for adjusting the distance between theopposing electrode 10 and theejection electrode 5 among several stages in accordance with the thickness of a recording medium disposed along thepaper travel path 9. For the mechanism, for example, a head-platen distance adjustment mechanism which is normally employed in a dot impact printer may be employed. - General operation of the electrostatic ink jet recording apparatus described above will be described below.
- When a voltage is applied from the migration voltage source 11 to the
electrophoretic electrode 8, an electric field is formed between theelectrophoretic electrode 8 and the end portion of theejection electrode 5 and causes toner particles in the ink chamber 2 to electrically migrate so that they concentrate upon thedischarging exit 4. Then, when a voltage pulse is applied from thedischarging voltage source 12 to theejection electrode 5, the toner particles concentrated upon thedischarging exit 4 are discharged in a group from theink meniscus 6 toward theopposing electrode 10. Then, the dischargedtoner group 3 sticks to a recording medium P. On the other hand, after the amount of toner particles in the proximity of thedischarging exit 4 is reduced as a result of the discharging, toner particles are supplemented toward thedischarging exit 4 by electric migration from the interior side of the ink chamber 2 so as to prepare for successive discharging. Meanwhile, an excessive amount of theink 1 is discharged from theink emission port 13. Those steps of operation are repeated to form a toner image on the recording medium P transported along thepaper travel path 9. Then, the recording medium P having the toner image formed thereon is transported to and subject to thermal fixation by a fixing unit (not shown) similar to a fixing unit for electrophotographic recording. - In this manner, in the electrostatic ink jet recording apparatus of the present embodiment, since only toner particles are discharged from within a liquid ink to effect recording, blurring on a recording medium or a like defect in terms of which conventional ink jet printing should be improved does not occur, and a high printing quality similar to that achieved by electrophotographic recording can be achieved.
- Here, if otherwise the
opposing electrode 10 is a complete conductor and is grounded as in the conventional electrostatic ink jet recording apparatus described hereinabove, then if the distance between theejection electrode 5 and theopposing electrode 10 is reduced shorter than a certain distance, a spark (voltage leak) is produced between theejection electrode 5 and theopposing electrode 10. If a spark is produced, then metal portions of theejection electrode 5 and the opposingelectrode 10 may be melted by heat by the spark, resulting in failure in function as a head. - However, in the electrostatic ink jet recording apparatus of the present embodiment, since the opposing
electrode 10 is formed from a conductive rubber roller having a high resistance value, even if the potential difference between theejection electrode 5 and the opposingelectrode 10 exceeds the dielectric strength of the space between theejection electrode 5 and the opposingelectrode 10 by some cause, an excessive electric current which may otherwise be produced by a spark can be suppressed by the resistance of the opposingelectrode 10. Consequently, theejection electrode 5 and the opposingelectrode 10 can be protected effectively from otherwise possible destruction by a spark with a comparatively inexpensive construction free from increase in size of the apparatus. - Referring now to FIGS. 3 to 5, there is shown another electrostatic ink jet recording apparatus to which the present invention is applied. The electrostatic ink jet recording apparatus shown is a modification to and has a common construction to that of the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2. Thus, overlapping description of the common construction is omitted herein to avoid redundancy.
- The electrostatic ink jet recording apparatus of the present embodiment is different from the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2 only in that it includes, between the opposing
electrode 10 and the ground, aresistor switch 15 and a plurality of high resistors which are selectively connected to the opposingelectrode 10 by theresistor switch 15. In the arrangement shown in FIGS. 3 to 5, three high resistors R1, R2 and R3 are provided and have different resistance values equal to or higher than 1 MΩ. - In particular, the resistors R1, R2 and R3 have resistance values of, for example, R1 = 1 MΩ, R2 = 2 MΩ and R3 = 3 MΩ, respectively. Further, the
resistor switch 15 is switched in response to the thickness of a printing vehicle to be used for recording. For example, the thickness of paper to be recorded is discriminated based on a result of adjustment of the gap or distance between therecording head body 100 and the opposingelectrode 10 performed by an automatic gap adjustment mechanism (not shown), which is usually employed in a dot impact printer as a distance adjustment mechanism between a head body and an opposing electrode, and a main controller (not shown) of the electrostatic ink jet recording apparatus operates theresistor switch 15 based on the discrimination to automatically select an optimum one of the resistors R1, R2 and R3. - Here, the reason why the resistors are selectively used in response to the thickness of the recording medium is described. In particular, in order to form normally fixed recording dots on a recording medium, the distance from the extremity of the
ejection electrode 5 to the surface of the recording medium must be set fixed, and since the recording medium is disposed in contact with the opposing electrode, it is necessary to adjust the distance between theejection electrode 5 and the opposingelectrode 10 based on the thickness of the recording medium to be used. However, when the magnitude of the high voltage pulse signal applied to theejection electrode 5 is constant, if the distance between theejection electrode 5 and the opposingelectrode 10 becomes shorter than a fixed distance, then the possibility occurs that a spark may be produced between theejection electrode 5 and the opposingelectrode 10. Therefore, the electrostatic ink jet recording apparatus of the present embodiment adopts the construction wherein the resistor to be used is switched in response to the thickness of the printing medium to prevent production of a spark. - Thus, in the electrostatic ink jet recording apparatus, after a recording medium having a certain thickness is set in position into the paper travel path and the distance between the extremity of the
ejection electrode 5 and the surface of the recording medium is adjusted to a certain fixed distance, theresistor switch 15 is operated in accordance with the amount of the adjustment then, for example, by the main controller of the apparatus mentioned hereinabove so that one of the three resistors R1, R2 and R3 is selectively connected. - For example, when, from among three recording media P1, P2 and P3 which are different in thickness from one another, the comparatively thick recording medium P1 is to be used as seen in FIG. 3, since the distance between the
ejection electrode 5 and the opposingelectrode 10 is comparatively large, the resistor R1 of 1 MΩ is selectively connected. In contrast, when the recording medium P2 having a middle thickness is to be used as seen in FIG. 4, the resistor R2 of 2 MΩ is selectively connected. On the other hand, when the comparatively thin recording medium P3 is to be used as seen in FIG. 5, since the distance between theejection electrode 5 and the opposingelectrode 10 is comparatively short, the resistor P3 of 3 MΩ is selectively connected. - Here, the resistance values of the resistors R1, R2 and R3 must be set to optimum values for recording media of different thickness values in advance.
- With the electrostatic ink jet recording apparatus of the present embodiment having the construction described above, similar advantages to those achieved by the electrostatic ink jet recording apparatus of the preceding embodiment are achieved, and in addition, there is another advantage that production of an excessive electric current upon leaking can be prevented effectively irrespective of the thickness of a recording medium to be used.
- In the meantime, it is otherwise possible to vary the voltage to be applied to the
ejection electrode 5 in response to the distance between theejection electrode 5 and the opposingelectrode 10 to prevent an excessive electric current upon leaking. Further, theresistor switch 15 may alternatively be operated manually by an operator in accordance with the thickness of a recording medium to be used. In this instance, no particular measure is required for detecting the thickness of a recording medium. - Referring now to FIGS. 6 and 7, there is shown a further electrostatic ink jet recording apparatus to which the present invention is applied. The electrostatic ink jet recording apparatus shown is a modification to and has a common construction to that of the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2. Thus, overlapping description of the common construction is omitted herein to avoid redundancy.
- The electrostatic ink jet recording apparatus of the present embodiment is different from the electrostatic ink jet recording apparatus described hereinabove with reference to FIGS. 1 and 2 only in that it includes, for the opposing
electrode 10, a current measuringinstrument 16 for measuring the value of an electric current flowing to the opposingelectrode 10 and a measurementcurrent display unit 17 for displaying the current value measured by the current measuringinstrument 16. Thecurrent measuring instrument 16 measures the value of an electric current flowing between the opposingelectrode 10 and the ground and inputs to the measurementcurrent display unit 17, for example, a voltage which varies in accordance with the measured current. The measurementcurrent display unit 17 includes, for example, a level comparator not shown, and has a function of displaying, when the input voltage from the current measuringinstrument 16 exhibits a level higher than a threshold level set in advance, a warning representing that a leak has occurred and generating an alarm. - If a leak occurs between the
ejection electrode 5 and the opposingelectrode 10 by some inadvertent cause, the current measuringinstrument 16 measures such an electric current variation as illustrated in FIG. 8 and inputs a corresponding voltage signal to the measurementcurrent display unit 17. The measurementcurrent display unit 17 displays, on a display unit (not shown) thereof such as an operator panel, that a leak has occurred when the input voltage from the current measuringinstrument 16 exceeds the preset threshold level, and generates an alarm. Consequently, the user can be urged to take a suitable countermeasure quickly. Accordingly, in addition to the advantages achieved by the electrostatic ink jet recording apparatus of the first embodiment, another advantage that otherwise possible damage to theejection electrode 5 and the opposingelectrode 10 after a leak occurs can be prevented is achieved. - Here, the threshold level set in the measurement
current display unit 17 may be set to an intermediate value between an input voltage at which a leak occurs and another input voltage at which the electrodes are destroyed. Further, the construction of the opposing electrode side in the electrostatic ink jet recording apparatus of the embodiments described above can be applied as it is also to conventional electrostatic ink jet recording apparatus wherein liquid ink is jetted directly to a recording medium to effect recording on the recording medium, and in this instance, similar advantages are achieved. - Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit and scope of the invention as set forth herein.
Claims (5)
- An electrostatic ink jet recording apparatus which includes an ink chamber (2) for accommodating ink (1) in which charged toner particles are contained, a discharging exit (4) communicated with said ink chamber (2) and having an opening directed to the outside, an ejection electrode (5) disposed in said discharging exit (4) and having an end portion directed to the outside, an electrophoretic electrode (8) mounted on side walls (2b) of said ink chamber (2) such that said ejection electrode (5) is located therein, an opposing electrode (10) disposed in an opposing relationship to said discharging exit (4) with a paper travel path (9) interposed therebetween, a migration voltage source (11) for applying a migration voltage to said electrophoretic electrode (8), and a discharging voltage source (12) for applying a driving pulse voltage to said ejection electrode (5), characterized in that
said opposing electrode (10) is formed from a conductive rubber roller having a high resistance value. - An electrostatic ink jet recording apparatus as set forth in claim 1, characterized in that the resistance value of said opposing electrode (10) is equal to or higher than 1 MΩ.
- An electrostatic ink jet recording apparatus as set forth in claim 1, characterized in that it further comprises a resistor switch (15) and a plurality of high resistors (R1, R2, R3) for being selectively connected to said opposing electrode (10) by said resistor switch (15), said resistor switch (15) and said plurality of high resistors (R1, R2, R3) being interposed between said opposing electrode (10) and the ground.
- An electrostatic ink jet recording apparatus as set forth in claim 3, characterized in that said plurality of high resistors are at least three high resistors (R1, R2, R3) having different resistance values equal to or higher than 1 MΩ.
- An electrostatic ink jet recording apparatus which includes an ink chamber (2) for accommodating ink (1) in which charged toner particles are contained, a discharging exit (4) communicated with said ink chamber (2) and having an opening directed to the outside, an ejection electrode (5) disposed in said discharging exit (4) and having an end portion directed to the outside, an electrophoretic electrode (8) mounted on side walls (2b) of said ink chamber (2) such that said ejection electrode (5) is located therein, an opposing electrode (10) disposed in an opposing relationship to said discharging exit (4) with a paper travel path (9) interposed therebetween, a migration voltage source (11) for applying a migration voltage to said electrophoretic electrode (8), and a discharging voltage source (12) for applying a driving pulse voltage to said ejection electrode (5), characterized in that
said opposing electrode (10) is formed from a conductive rubber roller having a high resistance value, and that
said electrostatic ink jet recording apparatus further includes current measurement means (16) for measuring a value of an electric current flowing to said opposing electrode (16), and measured current display means (17) for displaying the value of the electric current measured by said current measurement means (16).
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP28182095 | 1995-10-30 | ||
JP28182095A JP2874093B2 (en) | 1995-10-30 | 1995-10-30 | Electrostatic inkjet recording device |
JP281820/95 | 1995-10-30 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0771653A1 true EP0771653A1 (en) | 1997-05-07 |
EP0771653B1 EP0771653B1 (en) | 1999-09-01 |
Family
ID=17644458
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19960116324 Expired - Lifetime EP0771653B1 (en) | 1995-10-30 | 1996-10-11 | Electrostatic ink jet recording apparatus |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0771653B1 (en) |
JP (1) | JP2874093B2 (en) |
DE (1) | DE69604038T2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1788375A1 (en) * | 2004-08-20 | 2007-05-23 | Hamamatsu Photonics K.K. | Liquid droplet forming method and liquid droplet forming device |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2006129505A1 (en) * | 2005-06-03 | 2006-12-07 | Konica Minolta Holdings, Inc. | Liquid jetting device and liquid jetting method |
JP5724324B2 (en) * | 2010-11-24 | 2015-05-27 | 株式会社リコー | Image forming apparatus and image forming method |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5571575A (en) * | 1978-11-24 | 1980-05-29 | Matsushita Electric Ind Co Ltd | Image recorder |
JPS6157343A (en) * | 1984-08-29 | 1986-03-24 | Toshiba Corp | Ink jet recording equipment |
JPS61237653A (en) * | 1985-04-15 | 1986-10-22 | Tokyo Electric Co Ltd | Printer |
JPS6242848A (en) * | 1985-08-20 | 1987-02-24 | Toshiba Corp | Ink jet recorder |
JPH05212867A (en) * | 1992-02-05 | 1993-08-24 | Seikosha Co Ltd | Electrostatic ink jet recording apparatus |
EP0590768A2 (en) * | 1992-09-28 | 1994-04-06 | Fujitsu Limited | Image formation apparatus, developing device incorporated therein and conductive rubber roller used therein |
JPH06319261A (en) * | 1992-06-03 | 1994-11-15 | Fukushima Nippon Denki Kk | Multiple output converter |
-
1995
- 1995-10-30 JP JP28182095A patent/JP2874093B2/en not_active Expired - Fee Related
-
1996
- 1996-10-11 EP EP19960116324 patent/EP0771653B1/en not_active Expired - Lifetime
- 1996-10-11 DE DE1996604038 patent/DE69604038T2/en not_active Expired - Fee Related
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5571575A (en) * | 1978-11-24 | 1980-05-29 | Matsushita Electric Ind Co Ltd | Image recorder |
JPS6157343A (en) * | 1984-08-29 | 1986-03-24 | Toshiba Corp | Ink jet recording equipment |
JPS61237653A (en) * | 1985-04-15 | 1986-10-22 | Tokyo Electric Co Ltd | Printer |
JPS6242848A (en) * | 1985-08-20 | 1987-02-24 | Toshiba Corp | Ink jet recorder |
JPH05212867A (en) * | 1992-02-05 | 1993-08-24 | Seikosha Co Ltd | Electrostatic ink jet recording apparatus |
JPH06319261A (en) * | 1992-06-03 | 1994-11-15 | Fukushima Nippon Denki Kk | Multiple output converter |
EP0590768A2 (en) * | 1992-09-28 | 1994-04-06 | Fujitsu Limited | Image formation apparatus, developing device incorporated therein and conductive rubber roller used therein |
Non-Patent Citations (6)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 004, no. 114 (M - 026) 15 August 1980 (1980-08-15) * |
PATENT ABSTRACTS OF JAPAN vol. 010, no. 218 (M - 503) 30 July 1986 (1986-07-30) * |
PATENT ABSTRACTS OF JAPAN vol. 011, no. 082 (M - 571) 12 March 1987 (1987-03-12) * |
PATENT ABSTRACTS OF JAPAN vol. 011, no. 228 (M - 610) 24 July 1987 (1987-07-24) * |
PATENT ABSTRACTS OF JAPAN vol. 017, no. 652 (M - 1520) 3 December 1993 (1993-12-03) * |
PATENT ABSTRACTS OF JAPAN vol. 94, no. 011 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1788375A1 (en) * | 2004-08-20 | 2007-05-23 | Hamamatsu Photonics K.K. | Liquid droplet forming method and liquid droplet forming device |
EP1788375A4 (en) * | 2004-08-20 | 2012-12-19 | Hamamatsu Photonics Kk | Liquid droplet forming method and liquid droplet forming device |
Also Published As
Publication number | Publication date |
---|---|
DE69604038D1 (en) | 1999-10-07 |
JP2874093B2 (en) | 1999-03-24 |
DE69604038T2 (en) | 2000-05-25 |
JPH09123460A (en) | 1997-05-13 |
EP0771653B1 (en) | 1999-09-01 |
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