JP2937955B2 - Electrostatic ink jet recording head - Google Patents

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 recording head, and more particularly, to an ink jet recording head, in which an electric field is applied to ink in which charged toner particles are dispersed, and the toner particles are ejected by an electrostatic force generated by the electric field to perform printing. The present invention relates to an electrostatic ink jet recording head that performs the following.

[0002]

2. Description of the Related Art The non-impact recording method has recently attracted attention in that noise during recording is extremely small to a negligible level. Among them, the ink jet recording method that can record directly on a recording medium at high speed with a simple mechanism and that can record on plain paper is an extremely powerful recording method, and various methods have been proposed so far. Have been. In it, an ink in which toner particles are dispersed in a carrier liquid is used, and a voltage is applied between a needle-shaped recording electrode and an electrode provided on the back of the recording paper opposed thereto, and the electrostatic force of the generated electric field is used. There is an electrostatic ink jet recording system in which a color material in ink is caused to fly and recording is performed.

An example of a conventional electrostatic ink jet recording system will be described with reference to FIGS. 5, 6 and 7. FIG. FIG.
FIG. 6 is a perspective view of a conventional electrostatic ink jet recording head, FIG. 6 is a top view and a cross-sectional view of a head end portion of the conventional electrostatic ink jet recording head, and FIG. 7 is a bb cross-sectional view of FIG.

The substrate 101 is an insulator such as plastic.
The base film 110 is supported from the back side. The base film 110 is an insulator such as polyimide, has a thickness of about 50 μm, and has a plurality of recording electrodes 102 formed integrally on the surface thereof. The recording electrodes 102 are formed by pattern-plating a conductive material such as copper on a base film 110 to a thickness of 20 to 30 μm, and are arranged at a pitch of 300 dpi, that is, at intervals of about 85 μm. The recording electrodes 102 independently protrude from the end faces of the base film 110, and the protruding amount is about 80 μm to 500 μm. Further, the surface of the recording electrode 102 is uniformly coated with an insulating coating material 103 with a thickness of 10 μm or less. In this example, a tape-shaped head in which the recording electrode 102 is integrally formed on the base film 110 is used. Specifically, TAB (Tape Automated Bondin) is used.
g) Using TAB tape used in the technology,
The insulating coating material 103 is formed by parylene resin chemical vapor deposition.

[0005] A cover 104 is mounted on the base film 110 at a position that does not cover the projection of the recording electrode 102. The cover 104 is an insulative member, and the ink supply port 105 and the ink discharge port (not shown) are processed in advance.
4 constitutes an ink chamber, and the ink is filled from the ink supply port 105 to fill the inside. Further, the cover 104 has an opening at the tip end, and a slit-shaped opening formed by the base film 110 and the cover 104 forms an ink ejection port 107, and an ink meniscus 108 is formed therein. .

[0006] The ink forms an ink meniscus 108 at the ink ejection port 107 due to its surface tension. Since a back pressure is applied to the ink in the head, and the recording electrode 102 protrudes from the base film 110 and the cover 104, the ink meniscus 108 has a concave shape obliquely downward when viewed from the side. Further, since each recording electrode 102 individually protrudes outside the ink ejection port 107, the ink meniscus 108 is formed corresponding to each recording electrode 102 when viewed from above.

Therefore, when a high voltage pulse is applied to an arbitrary recording electrode 102, an electric field is concentrated on the tip of the ink meniscus protruding from the recording electrode 102. The charged toner in the ink is guided by this electric field and is drawn out from the protruding tip of the ink meniscus, and the toner group 1
At 09, it flies in the direction of the counter electrode (not shown) facing the recording head, ie, the recording paper (8 in FIG. 8).

FIG. 8 is a schematic diagram of equipotential lines generated during recording by a conventional electrostatic ink jet recording head.

In FIG. 8, an equipotential line 123 near the discharge point 120 when a recording voltage is applied is formed so as to follow the shape of the recording electrode 102.
Since equipotential lines 123 substantially parallel to the ejection direction are generated on the ink in the vicinity, no electrostatic force in the direction toward the ejection point 120 is generated in the toner particles near the ejection point 120. Therefore, the supply amount of toner particles for forming a desired dot diameter on the ejection point 120 while the recording voltage is being applied is insufficient.
A desired dot diameter cannot be formed.

Further, an electric field for performing ejection is generated by the recording electrode 1.
02 and the counter electrode 7, the recording electrode 1
The electric field density in the vicinity of the ejection point 120 changes due to the change in the gap between the counter electrode 02 and the counter electrode 7, which affects the ink droplet ejection state.

[0011]

First, the above-mentioned conventional electrostatic ink jet recording head has a structure in which an electric field necessary for discharging ink droplets is generated by an electric field between a recording electrode and a counter electrode. When a gap of about 0.5 to 1 mm is secured between the recording electrode and the counter electrode to convey the paper, the recording voltage required to generate an electric field required for ejecting ink droplets increases in proportion to the gap. There is a problem that it becomes.

Secondly, since the ejection point is formed by the recording electrode, and no electrostatic force is generated in the direction toward the ejection point for the toner particles near the ejection point when a recording voltage is applied, the toner particles are discharged. It has a structure that is difficult to migrate to the discharge point, so when driven at a high drive frequency, it is not possible to supply a sufficient amount of toner particles to form a desired dot on the discharge point, and in the high drive frequency region There is a problem that the printing of is deteriorated.

Third, a convex ink meniscus having a discharge point at the top is continuously connected, and the vibration of the liquid surface near the discharge point where the discharge is performed affects the ink meniscus on the other discharge points. Therefore, there is a problem that a stable ink meniscus cannot always be obtained, and ejection of ink droplets becomes unstable.

Fourth, since the discharge opening for supplying ink to the discharge point is formed as a slit in a part of the ink chamber which does not cause the ink to overflow, the ink in the discharge opening is formed. Does not flow, causing an increase in ink viscosity due to excessive concentration of toner particles in the ejection opening, which causes a problem that ejection failure of ink droplets occurs.

An object of the present invention has been made in view of the foregoing points, and has been made to reduce the recording voltage, prevent printing deterioration in a high driving frequency region, stabilize the ejection of ink droplets, and reduce excessive toner particles. It is an object of the present invention to provide an electrostatic ink jet recording head for preventing a discharge failure of ink droplets due to concentration of ink.

[0016]

The electrostatic ink jet recording head of the present invention applies an electric field to ink in which charged toner particles are dispersed, and discharges the toner particles by an electrostatic force generated by the electric field. In an electrostatic ink jet recording head that performs printing, a discharge member having a plurality of concavo-convex shapes formed continuously on two surfaces that are in contact with each other, and on one surface on which the concavo-convex shape of the discharge member is formed A recording electrode substrate having a recording electrode disposed thereon,
A minute slit-shaped discharge that covers the uneven surface formed on the two surfaces of the discharge member that are in contact with each other and opens the corner of the uneven portion that is formed on the two surfaces of the discharge member that are in contact with each other The discharge opening of the cover block is opened on the cover block having a shape in which the opening is formed, and on the cover block in front of the corner of the uneven portion formed on the two surfaces that are in contact with each other of the discharge member. And a control electrode formed on the substrate.

In the electrostatic ink jet recording head according to the present invention, the discharge opening of the cover block may be tapered so that the discharge opening widens toward the front of the corner of the uneven portion formed on the two surfaces of the discharge member that are in contact with each other. It may have a shape.

In the electrostatic ink jet recording head according to the present invention, each of the recording electrodes has an electrode width larger than a width of a convex portion formed on the discharge member, and each of the convex portions formed on the discharge member is formed. Are formed at the same interval as every other convex portion, and the central axis of each electrode of the recording electrode and the central axis of each convex portion of the ejection member may be arranged so as to coincide with each other. Good.

In the electrostatic ink jet recording head according to the present invention, the uneven surface formed on the two surfaces of the discharge member that are in contact with each other is in contact with an inner chamber and an outer chamber, respectively. May communicate with each other through respective concave portions that are respectively continuous on two surfaces of the discharge member that are in contact with each other.

[0020] In the electrostatic ink jet recording head of the present invention, the recording electrode forming surface of the recording electrode substrate may be disposed so as to face the uneven surface of the ejection member.

In the electrostatic ink jet recording head according to the present invention, the recording electrodes may be coated with an insulating coating material.

In the electrostatic ink jet recording head according to the present invention, the ejection member and the cover block may be formed of an insulating material having a dielectric constant of 10 or less.

In the electrostatic ink jet recording head of the present invention, a migration electrode in contact with ink may be provided in the inner chamber.

[0024]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of one embodiment of the electrostatic ink jet recording head of the present invention, FIG. 2 is a detailed view of a discharge section, and FIG. 3 is a sectional view near a discharge point.

The discharge member 1 is made of an insulating material having a dielectric constant of 10 or less, such as ceramics and a polymer material, and has a plurality of continuous irregularities formed on two surfaces that are in contact with each other. In addition, the discharge member 1 has a two-sided projection and a depression formed at a position facing the counter electrode 7 such that a corner of the two projections on which the projections and depressions are formed becomes the ejection point 20. The projection is supported by the head block 2 such that the corners of the projection protrude.

The recording electrode substrate 3 has independent recording electrodes 14 formed on a thin insulating substrate or a film made of a polymer material. One end of the recording electrode 14 is formed at one end of the recording electrode substrate 3 so as to be arranged at the same interval as a desired dot pitch, and the other end of the recording electrode 14 is connected to an external driver power supply (not shown). Electrode pads are formed. The surface of the recording electrode 14 is uniformly coated with an insulating coating material 19 with a thickness of 10 μm or less. Further, the recording electrode substrate 3 has a concave / convex surface on which the recording electrode 14 is formed to face the concave / convex surface of the discharge member 1 at a position several tens of μm away from the discharge point 20 on one of the concave / convex surfaces of the discharge member 1. It is arranged so as to cover the upper part.

Each projection of the ejection member 1 is formed at an interval of 1/2 with respect to a desired dot pitch, and the center axis of each recording electrode 14 of the recording electrode substrate 3 is aligned with every other projection. (A) It is arranged so as to coincide with the central axis of 15.
The width of each projection (A) 15 arranged at the position of each recording electrode 14 is desirably 20 μm or less, whereas the width of each recording electrode 14 is the width of each projection (A) 15. It has a wider electrode width. In addition, the actual ink droplet 21
The ejection points 20 at which the ejection is performed are the convex portions (A) 15 arranged at the positions of the recording electrodes 14,
Each of the other convex portions (B) 16 functions as a partition wall for preventing the vibration of the meniscus 22 after the ejection of the ink droplet 21 from the ejection point 20 from being transmitted to another ejection point 20. doing.

The cover block 4 is made of an insulating material having a dielectric constant of 10 or less, such as a ceramic material or a polymer material, and has a small slit-like shape in which the corners of two convex portions of the discharge member 1 that are in contact with each other are opened. An ejection opening 13 is formed. In order to prevent the ink 18 supplied to each concave portion 17 of the ejection member 1 from overflowing out of the recording head, the cover block 4 has an uneven surface formed on two surfaces which are in contact with each other of the ejection member 1. It is arranged to cover. Further, the control electrode 5 is formed on the cover block 4 in front of the corner of the projection so as to open the discharge opening 13 of the cover block 4.

The discharge opening 13 on the cover block 4
When the ink 18 supplied to each recess 17 of the ejection member 1 overflows to the ejection opening 13, the ejection member 18 is configured to quickly return the ink 18 overflowing to the ejection opening 13 to each recess 17. It is preferable that the projection has a tapered shape that widens toward the front of the corner of the projection.

The migrating electrode 6 is made of a conductive material such as metal and is connected to an external voltage source (not shown).
Is provided in the inner chamber 9 on the side where the supply of the ink 18 is performed so as to be in contact with the ink 18.

The counter electrode 7 is made of a conductive material such as a metal, and is connected to a ground or an external voltage source (not shown).
It is arranged so as to secure a print gap at a desired interval from the ejection point 20 in the recording head. The counter electrode 7 also has a function of a platen for conveying the recording paper 8,
The recording paper 8 conveyed from a paper feed mechanism (not shown) is moved within a printing gap between the counter electrode 7 and the ejection point 20.
It is transported so as to be always in contact with the counter electrode 7.

The inner chamber 9 and the outer chamber 10 are independently formed in the recording head, and a part of the inner chamber 9 has an ink supply port 11 for supplying ink 18 from the outside.
Is formed with an ink discharge port 12 for discharging the ink 18 to the outside. Further, a part of the inner chamber 9 and a part of the outer chamber 10 are respectively in contact with the concave portion 17 on one surface formed in the discharge member 1, and the inner chamber 9 and the outer chamber 10
Are communicated via the respective recessed portions 17 formed in the holes. Further, the recording head is connected to the ink supply port 1 by a circulation mechanism (not shown).
1 and the ink discharge port 12 are connected to an external ink tank (not shown), and ink is constantly circulated between the ink tank and the recording head. As a result, the ink 18 supplied to the inner chamber 9 of the recording head is discharged to the outer chamber 10 via the respective recesses 17 formed in the ejection member 1. Of ink 18 is constantly circulating. In addition,
The outer chamber 10 is desirably disposed above the inner chamber 9 in order to prevent bubbles from remaining in the recording head when bubbles are mixed in from the ejection member 1.

The ink 18 in the recording head is applied to the ejection member 1.
The ink circulation is performed while applying a back pressure that does not exceed the capillary force of each concave portion 17 formed in each of the concave portions 17. 22 are formed.

A constant bias voltage having the same polarity as that of the charged toner particles is applied to the migration electrode 6, a constant bias voltage having a ground level or a polarity different from that of the charged toner particles is applied to the control electrode 5, and the opposite electrode 7 is applied to the counter electrode 7. A bias voltage having the same potential as the control electrode 5 or a potential lower than the control electrode 5 is always applied. The ink 18 in which the toner particles supplied into the recording head are dispersed is pulled up to a potential at which no discharge occurs by the electrophoresis electrode 6 which is in contact with the ink 18 in the inner chamber 9. Supplied to

At the time of recording, a driving pulse voltage is applied from a driving driver (not shown) to a desired recording electrode 14, and an electric field generated between the recording electrode 14 and the control electrode 5 causes the electric field in the ink 18 supplied on the ejection point 20 to be discharged. The electrostatic force acts on the toner particles, and the electrostatic force of the toner particles overcomes the surface tension of the convex meniscus 22 on the ejection point 20,
Ink droplet 2 containing toner particles from above ejection point 20
1 is discharged to the counter electrode 7 side, and the ink droplet 21 that has passed through the discharge opening 13 lands on the recording paper 8 on the counter electrode 7 while maintaining the inertia force by the discharge, and printing is performed.

FIG. 4 is a schematic diagram of equipotential lines generated during recording by the electrostatic ink jet recording head of the present invention.

In FIG. 4, the equipotential line 23 near the ejection point 20 when the recording voltage is applied is formed so as to be substantially orthogonal to the ejection direction. An electrostatic force in the direction toward is generated. Therefore, the supply of the toner particles onto the ejection point 20 is performed even while the recording voltage is being applied, and further, the convex meniscus 22 is provided forward of the recording electrode 14.
Therefore, a sufficient amount of toner particles for forming a desired dot diameter on the discharge point 20 can be supplied even while the recording voltage is being applied. Further, by changing the time for applying the recording voltage, the supply amount of the toner particles onto the discharge point 20 can be changed, so that an arbitrary dot diameter can be formed.

Since an electric field for performing ejection is generated between the recording electrode 14 and the control electrode 5 in the same head, an electric field density sufficient for performing ejection is set at the ejection point 20.
Ink droplets 2 even when the gap between the recording electrode 14 and the counter electrode 7 changes.
1 can be made unaffected by the ejection state.

[0040]

As described above, the present invention provides the first
In addition, because of the structure in which the electric field required for ejecting ink droplets is generated by the electric field between the recording electrode and the control electrode in the same head,
By the configuration of the recording electrode and the control electrode in the head, the electric field density in the vicinity of the ejection point can be made sufficiently dense, and the recording voltage can be reduced. Further, since the ink droplet can be ejected by the electric field between the recording electrode and the control electrode, there is an effect that the gap between the recording electrode and the counter electrode can be arbitrarily set for transporting the recording paper.

Second, the discharge point is formed in front of the recording electrode, and each recording electrode is formed so as to surround each discharge point. On the other hand, an electrostatic force is generated in the direction toward the discharge point, and the ink has a pool of ink meniscus ahead of the recording electrode, so that the toner particles are easily migrated to the discharge point. Therefore, even when driven at a high driving frequency, there is an effect that a sufficient amount of toner particles can be supplied to form a desired dot on an ejection point.

Third, each ink meniscus having a peak at the discharge point composed of the convex portion (A) disposed below the recording electrode is a partition composed of convex portions (B) formed on both sides. To form an independent meniscus,
Since the vibration of the liquid surface near the ejection point where the ejection was performed does not affect the ink meniscus at other ejection points, it is possible to always obtain a stable ink meniscus,
There is an effect that stable ejection of ink droplets can be performed.

Fourthly, by causing a forced flow from the inner chamber to the outer chamber in each of the recesses formed near the discharge point, the ink in each of the recesses is always circulated. Therefore, it is possible to prevent accumulation of toner particles in the vicinity of the discharge point closest to the above, and to prevent defective discharge of ink droplets due to excessive concentration of toner particles.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of an electrostatic ink jet recording head according to the present invention.

FIG. 2 is a detailed view of a discharge unit of one embodiment of the electrostatic ink jet recording head of the present invention.

FIG. 3 is a sectional view showing the vicinity of a discharge point of the electrostatic ink jet recording head of the present invention.

FIG. 4 is a schematic view of equipotential lines generated at the time of recording by the electrostatic ink jet recording head of the present invention.

FIG. 5 is a perspective view of a conventional electrostatic ink jet recording head.

FIG. 6 is a top view and a sectional view of a head end portion of a conventional electrostatic ink jet recording head.

FIG. 7 is a sectional view taken along the line bb of FIG. 6;

FIG. 8 is a schematic view of equipotential lines generated during recording by a conventional electrostatic ink jet recording head.

[Explanation of symbols]

 Reference Signs List 1 ejection member 2 head block 3 recording electrode substrate 4 cover block 5 control electrode 6 migrating electrode 7 counter electrode 8 recording paper 9 inner chamber 10 outer chamber 11 ink supply port 12 ink discharge port 13 ejection opening 14 recording electrode 15 convex part ( A) 16 convex part (B) 17 concave part 18 ink 19 insulating coating material 20 discharge point 21 ink drop 22 meniscus 23 equipotential line

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Minemoto 7546 Yasuda, Kashiwazaki-shi, Niigata Niigata Nippon Electric Co., Ltd. (72) Inventor Hitoshi Takemoto 7546 Yasuda, Kashiwazaki-shi, Niigata Inside (72) Inventor Tomoya Saeki 7546 Yasuda, Kashiwazaki City, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. (72) Inventor Yoshihiro Hagiwara 7546 Yasuda, Oji Character in Kashiwazaki City, Niigata Prefecture (72) Inventor Toru Yakushiji 7546 Yasuda, Kashiwazaki-shi, Niigata Prefecture Niigata Nippon Electric Co., Ltd. (56) References JP-A-9-123458 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) B41J 2/06 B41J 2/16

Claims (8)

(57) [Claims] 1. An electrostatic ink jet recording head which applies an electric field to ink in which charged toner particles are dispersed and discharges the toner particles by an electrostatic force generated by the electric field to perform printing, the two surfaces being in contact with each other. A discharge electrode formed with a plurality of concavo-convex shapes each of which is continuous above, a recording electrode substrate having a recording electrode disposed on one surface of the discharge member on which the concavo-convex shape is formed, and A minute slit-shaped discharge opening so as to cover the uneven surface formed on the two surfaces that are in contact with each other of the member and to open the corner of the uneven portion formed on the two surfaces that are in contact with the discharge member. A cover block having a shape formed with the cover member, and the cover block is provided on the cover block in front of a corner portion of an uneven portion formed on two surfaces of the discharge member that are in contact with each other. A control electrode formed so as to open a discharge opening of the lock. 2. The discharge opening of the cover block has a tapered shape that widens toward the front of a corner portion of a concave and convex portion formed on two surfaces of the discharge member that are in contact with each other. Item 2. An electrostatic ink jet recording head according to Item 1. 3. The recording electrode has an electrode width wider than a width of a protrusion formed on the discharge member, and is the same as every other protrusion formed on the discharge member. 3. The static electricity according to claim 1, wherein the recording electrodes are arranged at intervals and the central axes of the respective electrodes of the recording electrodes coincide with the central axes of the respective convex portions of the ejection member. Electric inkjet recording head. 4. An uneven surface formed on two surfaces of the discharge member that are in contact with each other is in contact with an inner chamber and an outer chamber, respectively, and the inner chamber and the outer chamber are in contact with each other of the discharge member. 4. The electrostatic ink jet recording head according to claim 1, wherein said ink jet recording heads communicate with each other through respective concave portions which are continuous on the surface. 5. The recording electrode substrate according to claim 1, wherein the recording electrode forming surface of the recording electrode substrate is arranged so as to face the uneven surface of the discharge member.
The electrostatic ink jet recording head according to the above. 6. The recording electrode according to claim 1, wherein the recording electrode is coated with an insulating coating material.
The electrostatic ink jet recording head according to 2, 3, 4 or 5. 7. The discharge member and the cover block are formed of an insulating material having a dielectric constant of 10 or less.
The electrostatic ink jet recording head according to the above. 8. The electrostatic ink jet recording according to claim 1, wherein a migration electrode in contact with ink is provided in the inner chamber. head.