JPH10157133A - Electrostatic ink jet print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To jet an ink droplet stably by providing a recording electrode at the outer circumferential part of a plurality of orifices communicating with an ink chamber and opening to the outside, a jetting part projecting outward in the center of each orifice, and a counter electrode facing each orifice. SOLUTION: The print head comprises an orifice plate 2 and an ink chamber 7 provided, on the base plate 4 side thereof, with a migration electrode 6. A jetting part 11 is formed in the center of each orifice 3 on the surface of the orifice plate 2 and a recording electrode 12 is formed at the circumferential fringe part of each orifice 3 on the back of the orifice plate 2. At the time of recording, a pulse voltage is applied onto the recording electrode 12 and toner particles in an ink 8 on a jetting point 14 are subjected to electrostatic force. When the electrostatic force overcomes the surface tension of meniscus on the jetting point 14, an ink droplet 17 is jetted toward a counter electrode 15 and fixed onto a recording paper 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet printhead used in a recording apparatus of an electrostatic ink jet recording system.

[0002]

2. Description of the Related Art The non-impact recording method has recently attracted attention in that the generation of noise during recording is extremely small to a negligible level. Among them, the ink jet recording method that can perform high-speed recording on a recording medium with a simple mechanism and that can perform recording on plain paper is an extremely powerful recording method, and various methods have been proposed so far. ing. One of such non-impact recording methods is an electrostatic ink jet recording method. This electrostatic ink jet recording method uses a dispersion of toner particles in a carrier liquid as ink, and provides a needle-like recording electrode and a counter electrode on the back surface of recording paper facing the recording electrode. A predetermined voltage is applied between the electrode and a counter electrode, and recording is performed by causing a color material such as toner particles in ink to fly on recording paper by electrostatic force of an electric field generated by the voltage.

FIGS. 4 and 5 are views showing the structure of a conventional electrostatic ink jet print head used in the above-mentioned electrostatic ink jet recording type recording apparatus. FIG. 4 shows an electrostatic ink jet print head. FIG. 5 is an enlarged front view and a partial cross-sectional view of the head end portion. Hereinafter, the configuration of the conventional electrostatic ink jet print head will be described with reference to these drawings.

The substrate 101 is made of a flat insulating material.
A plurality of recording electrodes 102 are formed on the surface at predetermined intervals to obtain a desired resolution. This recording electrode 10
2 is a method in which a conductive material such as Cu (copper) or Ni (nickel) is sputtered on the entire surface of the substrate 101, and then the recording electrode 102 is formed.
Is formed on the substrate 101 by being exposed and developed through a patterned mask.

The recording electrode 102 is formed as an independent electrode, and one end thereof is connected to a driver (not shown), and a high voltage pulse is selectively applied at the time of recording. Further, the surface of the substrate 101 on which the recording electrodes 102 are formed is spin-coated with an insulating coating material so that the recording electrodes 102 are insulated from the ink containing the conductive toner particles. The meniscus forming member 103 is formed by laminating or spin-coating an insulating and photosensitive resist material on the substrate 101 on which the recording electrode 102 is formed, and then exposing through a mask in which the shape of the meniscus forming member 103 is patterned. -It is formed so as to be developed and overlap each recording electrode 102.

[0006] A cover 104 is mounted on the meniscus forming member 103 at a position retracted from the front end thereof. The cover 104 is made of an insulating material, and the ink supply port 105 and the ink discharge port 106 are processed and formed in advance. That is, on the substrate 101, the substrate 10
1, a cover 104 and a meniscus forming portion forest 103 on the recording electrode 102 form a slit-shaped minute discharge opening 107, and ink supplied from the ink supply port 105 passes through the discharge opening 107 to discharge the ink. Opening 10
The ink is supplied to the distal end portions of the meniscus forming members 103 protruding outward from the outer peripheral portions 7, and the meniscus of the ink is formed at the distal end portions of the respective meniscus forming members 103.

On the other hand, Japanese Patent Application Laid-Open No. 4-366641 discloses an ink chamber provided with an ink chamber and a nozzle plate having a nozzle connected to the ink chamber and having a nozzle for discharging ink. A technique has been disclosed in which an ink jet print head having a structure in which ink is ejected from the outside to stabilize the ink ejection direction by disposing a barbed or needle-shaped ink guide near the nozzle of a nozzle plate.

[0008]

However, the above-mentioned conventional electrostatic ink jet print head has the following problems. That is, the first problem is that ink droplet ejection is unstable. The reason is that the ink at the tip end of the meniscus forming member 103, which is the ink discharge point, is continuously connected by the meniscus between the adjacent meniscus forming members 103, so that the ink is discharged from the discharge point. This is because the vibration of the liquid surface of the meniscus which occurs at the end affects the meniscus of the ink at the tip of the neighboring meniscus forming member 103.

FIG. 6 is a diagram comparing the lines of electric force generated between the recording electrode 112 and the counter electrode 115 due to the difference in the arrangement of the recording electrodes 112. As shown in FIG. 6A, when the recording electrode 112 is disposed on the discharge point 114 facing the counter electrode 115, lines of electric force 118 extending from the recording electrode 112 toward the counter electrode 15 are generated. On the other hand, as shown in FIG. 6B, when two recording electrodes 112 are arranged at a fixed interval on both sides of the discharge point 114 facing the opposite electrode 115, the electric flux lines 1 converging on the opposite electrode 115 side
18 occurs. That is, in the configuration of the above-described conventional electrostatic ink jet print head, the directionality of ink droplet ejection becomes unstable.

A second problem is that ink is not ejected from a fixed ejection point. The reason is that the tip of the meniscus forming member 103 serving as a discharge point is formed at a position receding from the end surface of the substrate 101, so that a clear convex meniscus is formed on the discharge point due to the wetting of the ink on the end surface of the substrate 101. This is because a phenomenon occurs in which ink is not formed and ink is ejected from a portion other than the original ejection point.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made in consideration of the above-described problems. It is an object of the present invention to provide an ink jet print head.

[0012]

In order to achieve the above object, as a first means, an electric field is applied to ink in which charged toner particles are dispersed, and the toner particles are externally applied by an electrostatic force generated by the electric field. In an electrostatic ink jet print head that prints on a printing target by discharging ink to an ink chamber, an ink chamber filled with ink, a plurality of orifices that are micro holes communicating with the ink chamber and opening to the outside, and each orifice A recording electrode provided on the outer periphery of the orifice, a discharge portion protruding to the outside at the center or in the vicinity of each orifice, and a counter electrode provided to face each orifice. In this case, means for discharging toner particles to the outside by electrostatic force generated during the period is adopted.

As a second means, in the first means, the recording electrode is formed on the inner surface of the ink chamber and on the periphery of each orifice, and the surface of the recording medium is insulated so as to be insulated from the ink in the ink chamber. A means of being insulated and coated with a single material is used.

As a third means, in the first or second means, there is provided an electrophoresis electrode for electrophoresing toner particles in the direction of the orifice at a portion of the inner surface of the ink chamber facing the orifice. Adopted.

As a fourth means, in any one of the above first to third means, a means is adopted in which the chamber forming member forming the ink chamber is formed of a low dielectric constant insulating material.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electrostatic ink jet print head (hereinafter, simply referred to as a print head) according to the present invention will be described below with reference to FIGS.

First, a schematic configuration of the present embodiment will be described with reference to FIG. As shown in this figure, the print head 1 of the present embodiment has an orifice plate 2 provided with a plurality of orifices (micro holes) 3 formed in two rows and a discharge portion 11, and communication with each orifice 3. The ink chamber 7 is formed. The inside of the ink chamber 7 is filled with ink 8 in which charged toner particles are dispersed.

The ink chamber 7 is a space formed by a plurality of members (chamber forming members) such as the orifice plate 2, the base plate 4, and the ink partition 5 interposed between the orifice plate 2 and the base plate 4. These chamber forming members are formed of a low dielectric constant insulating material. An ink supply port 9 and an ink discharge port 10 communicating with the ink chamber 7 are formed in the base plate 4. The ink supply port 9 and the ink discharge port 10 are respectively connected to ink tanks (not shown) provided outside via a pump.

That is, the ink 8 filled in the ink chamber 7 is always circulated between the ink tank and the ink tank by the action of the pump. A migration electrode 6 made of a conductive metal material such as Cu (copper) or Ni (nickel) is provided on the base plate 4 side (a portion facing the orifice 3) of the ink chamber 7.

FIG. 2 shows the orifice 3 and the discharge section 11.
It is a detailed view of the vicinity. The orifice plate 2 is made of a thin plate or a film-like insulating material. On the orifice plate 2, orifices 3 formed of through holes communicating with the ink chamber 7 are arranged at intervals corresponding to a desired resolution. A number corresponding to the desired number of dots is formed. The orifices 3 are formed in a plurality of rows (in this embodiment, two rows as shown in FIG. 1) in order to achieve a desired resolution and the number of dots.

On the surface of the orifice plate 2, at the center or in the vicinity of each orifice 3, a minute discharge portion 11 is formed which protrudes outwardly of the orifice 3 and is smaller than the diameter of the orifice 3. On the back surface of the orifice plate 2 (the inner surface of the ink chamber 7), a recording electrode 12 is formed on the periphery of each orifice 3. The recording electrode 12 is formed of a conductive metal material such as Cu (copper) or Ni (nickel), and is formed so as to surround the periphery of each orifice 3. And insulating coating material 1
3 (see FIG. 3).

Next, the operation of the electrostatic ink jet print head will be described with reference to FIG. The ink 8 in the ink chamber 7 is supplied to the orifice plate 2
The orifices 3 are held while forming a convex meniscus having the discharge point 14 as the tip of the discharge portion 11 as the apex. A counter electrode 15 is disposed at a position facing the discharge portion 11 of the orifice flat 2 from a discharge point 14 with a certain gap therebetween. The recording paper 16 uses the counter electrode 15 as a platen and the counter electrode 15. Paper is fed while keeping a certain gap from the discharge point 14 while touching the top.

The counter electrode 15 is always grounded and kept at a ground level (ground potential), or
A bias voltage on the side opposite to the polarity of the toner particles in the medium is applied from a counter voltage source (not shown), and the recording paper 16 fed on the counter electrode 15 is the same as the counter electrode 15. It is charged to a potential.

During recording standby, a bias voltage having the same polarity as the polarity of the toner particles in the ink 8 is applied from the migration voltage source (not shown) to such an extent that the ink droplets 17 are not discharged from the discharge point 14 to the migration electrode 6. The ink 8 in the ink chamber 7 is charged to the same potential as the migration electrode 6. Further, the toner particles of the ink 8 in the ink chamber 7 are circulating while moving so as to gather toward the ejection point 14 on the orifice 3 by the electric field between the ink 8 and the counter electrode 15.

On the other hand, at the time of recording, a pulse voltage having the same polarity as the polarity of the toner particles in the ink 8 is applied to a recording electrode 12 formed on the ejection portion 11 corresponding to a desired print via a drive driver (not shown). Is applied from the recording voltage source, and the discharge point 1 is generated by an electric field between the recording electrode 12 and the counter electrode 15.
The electrostatic force acts on the toner particles of the ink 8 on the ink 4, and the electrostatic force overcomes the surface tension of the meniscus on the discharge point 14, so that the ink droplet 17 containing the toner particles on the discharge point 14 becomes the counter electrode 15. And adheres onto the recording paper 16. As a result, dots are formed on the recording paper 16 in the form of toner particles deposited thereon, and the deposited toner particles are fixed onto the recording paper 16 by a fixing mechanism (not shown) such as a heat roller.

[0026]

As described above, the electrostatic ink jet print head according to the present invention has the following effects. (1) An electrostatic ink jet print head that applies an electric field to ink in which charged toner particles are dispersed and discharges the toner particles to the outside by electrostatic force generated by the electric field to perform printing on a print target. , A plurality of orifices which are micro holes communicating with the ink chamber and opening to the outside, a recording electrode provided on the outer peripheral portion of each orifice, and an external portion at or near the center of each orifice. And a counter electrode provided to face each orifice, and the toner particles are discharged to the outside by electrostatic force generated between the recording electrode and the counter electrode. The ink droplet stably protrudes from the vicinity of the ejection portion to the outside. The reason is that the ink meniscus is formed individually in each orifice, and the vibration of the liquid surface on the meniscus when ink is ejected from near the ejection portion of the orifice causes the meniscus of the adjacent orifice to This has no effect. (2) Since the recording electrodes are formed on the inner surface of the ink chamber and on the periphery of each orifice, and the surface is insulated and coated with an insulating coating material so as to be insulated from the ink in the ink chamber. Lines of electric force converging from the recording electrode toward the counter electrode can be obtained. Therefore, the ejection direction of the ink droplet is stabilized by this. (3) Since a discharge portion protruding to the outside is provided at or near the center of each orifice, which is a minute hole, a convex meniscus having a small meniscus fluctuation with the orifice at the apex is formed, and is always stable from a desired orifice. Ink droplet ejection can be performed. (4) Since a migration electrode for electrophoresing toner particles in the direction of the orifice is provided in a portion of the inner surface of the ink chamber facing the orifice, charged toner particles in ink in the ink chamber can be effectively moved to the vicinity of the orifice. Can be collected.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of an electrostatic ink jet print head according to the present invention, and FIG.
It is sectional drawing of the A line.

FIG. 2 is a perspective view showing a configuration of an orifice portion of an orifice plate and an arrow view from the direction B in an embodiment of the electrostatic ink jet print head according to the present invention.

FIG. 3 is an explanatory diagram illustrating the operation of the electrostatic inkjet print head according to the present invention.

FIG. 4 is a perspective view showing a configuration of a conventional electrostatic ink jet print head.

FIG. 5 is a front view and a cross-sectional view taken along line BB showing a configuration of a head end portion of a conventional electrostatic ink jet print head.

FIG. 6 is a comparison diagram of electric lines of force due to differences in arrangement of recording electrodes.

[Explanation of symbols]

1 ... print head, 2 ... orifice plate, 3
... orifice, 4 ... base plate, 5 ... ink partition, 6 ... electrophoresis electrode, 7 ... ink chamber, 8 ...
Ink, 9 ... Ink supply port, 10 ... Ink discharge port,
11 discharge section, 12 recording electrode, 13 insulating coating material, 14 discharge point, 15 counter electrode, 16 recording paper, 17 ink drop

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Minemoto 7546 Yasuda, Niigata Prefecture Kashiwazaki City Niigata Nippon Electric Co., Ltd. (72) Inventor Yoshihiro Hagiwara 7546 Yasuda, Kashiwazaki, Niigata Prefecture Niigata Nippon Electric Co., Ltd. (72) Inventor Toru Yakushiji 7546, Yasuda, Kashiwazaki, Niigata Niigata Nippon Electric Co., Ltd.

Claims (4)

[Claims] 1. An electrostatic ink jet print head which applies an electric field to ink in which charged toner particles are dispersed, discharges the toner particles to the outside by electrostatic force generated by the electric field, and prints on a printing target. An ink chamber filled with ink; a plurality of orifices, each of which is a micro hole communicating with the ink chamber and opening to the outside; a recording electrode provided on an outer peripheral portion of each orifice; and a central portion or a vicinity of each orifice And a counter electrode provided to face each orifice, wherein the toner particles are discharged to the outside by electrostatic force generated between the recording electrode and the counter electrode. Characteristic electrostatic ink jet print head. 2. The electrostatic ink jet print head according to claim 1, wherein the recording electrode is formed on an inner surface of the ink chamber and a peripheral portion of each orifice, and a surface of the recording electrode is insulated from the ink in the ink chamber. An electrostatic ink jet print head characterized by being coated with an insulating coating material. 3. The electrostatic ink jet print head according to claim 1, wherein a portion of the inner surface of the ink chamber facing the orifice is provided with a migration electrode for electrophoresis of the toner particles in the direction of the orifice. Characteristic electrostatic ink jet print head. 4. The electrostatic ink jet print head according to claim 1, wherein the chamber forming member forming the ink chamber is formed of an insulating material having a low dielectric constant. Electric inkjet print head.