JP2826526B2 - Electrostatic inkjet printer - 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 printer for recording by attaching toner to a recording medium, and more particularly, to a structure of a recording head unit.

[0002]

2. Description of the Related Art The non-impact recording method has attracted attention in that noise during recording is negligibly small. Among these recording methods, the ink jet recording method has an advantage that it can perform high-speed printing directly on a recording medium with a simple mechanism, and is simple because plain paper can be used as the recording medium.

Various methods have been proposed as ink jet recording methods. One of them is to provide a plurality of recording electrodes on the front surface of the recording paper and one counter electrode on the back surface. The electrostatic force of the electric field generated when a voltage is applied between the plurality of recording electrodes and the counter electrode, such as ink There is an electrostatic ink jet recording method in which a color material is recorded on a recording paper while flying.
In this method, an ink containing a charged toner in an insulating solvent is used.

A specific example of the electrostatic ink jet recording method will be described with reference to FIGS. The recording head unit of the electrostatic ink jet printer includes a substrate 11 and an upper cover 14 made of an insulating member facing the substrate 11, and a plurality of recording electrodes 12 are provided on the surface of the substrate 11 in a direction perpendicular to the ejection direction. Are arranged next to each other. Upper cover 14
Is formed with an ink supply port 15 and an ink discharge port 16. The plurality of recording electrodes 12 are formed by patterning a conductive material such as chromium sputtered on the entire surface of the substrate 11 by a photolithography method.
They are provided at a dpi pitch, that is, at intervals of about 85 μm. The plurality of recording electrodes 12 are connected to a driver (not shown) provided on the printer main body side, and a high voltage pulse is selectively applied at the time of recording.

[0005] A plurality of meniscus forming members 18 are arranged between the substrate 11 and the upper cover 14 in correspondence with the recording electrodes 12. The meniscus forming member 18
The photosensitive polymer film formed thereon is processed by a photolithography method.
Is provided at a position slightly retreated from the tip of the recording electrode 12 so as to overlap with each recording electrode 12.
The thickness of the photosensitive polymer film is 30 μm, and the width of the meniscus forming member 18 is about 30 μm. The tip of the upper cover 14 is located further back than the tip of the meniscus forming member 18. Between the substrate 11 and the upper cover 14, each recording electrode 12 and the meniscus forming member 18
Thus, a slit-shaped ink ejection port 17 is formed. Meniscus forming member 18 on recording electrode 12
The ink path 10 (see FIG. 7) is formed between the lower surface and the substrate 11 while the rear end extends below the upper cover 14 to support the upper cover 14 from below.

[0006] An ink chamber is formed between the substrate 11 and the upper cover 14 by the rear end face of the meniscus forming member 18 and the substrate 11 and the upper cover 14. The electrophoresis electrode 21 and the recording paper 2 are located behind the ink flow path 10.
The counter electrodes 13 are provided on the back surface of each of the reference numerals 5. The migration electrode 21 collects and concentrates charged toner particles in the ink by applying a migration voltage to the ink. The toner particles in the ink move via the ink flow path 10 due to the electrophoretic force of the electric field generated between the counter electrode 13 and the migrating electrode 21, and concentrate near the ejection port 17.

In the above-mentioned electrostatic ink jet printer,
The electrostatic force generated between the counter electrode 13 and the recording electrode 12 on the back surface of the recording paper 25 causes the toner in the ink to fly onto the recording paper, and the distance between the counter electrode 13 and the recording electrode 12 is sufficient. In this case, the potential difference between the recording electrode 12 and the counter electrode 13 is, for example, 1 kv
Such a high voltage is required.

Further, the same phenomenon as the change in the distance between the recording electrode 12 and the counter electrode 13 during the recording operation occurs due to the thickness of the recording paper 25 or the floating phenomenon of the recording paper 25 during transportation. . For this reason, there is a problem that the electrostatic force acting on the toner particles 26 in the ink changes, and stable flying of the toner particles 26 is hindered.

As electrostatic ink jet printers, those disclosed in JP-B-58-153661 and JP-B-58-153662 are separately known. In the printers described in these publications, a plurality of ejection ports constituting the first electrode are arranged in a two-dimensional XY manner, and are arranged in the Y direction (the traveling direction of the recording paper) or the X direction (the width direction of the recording paper). The first electrode is used as a common lead terminal, the second electrode disposed behind the first electrode is used as a common electrode in the X direction, and a third electrode is provided on the recording paper side ahead of the first electrode in the ejection direction. Prepare.

The electrostatic ink jet printer described in the above publication has the same problems as the conventional electrostatic ink jet printer shown in FIGS. 5 to 7, and also has a problem in that the ink itself is charged. In addition, there is a problem that printing bleeding or bleeding occurs to deteriorate printing quality. Further, since the second electrode, which is one of the electrodes for driving the matrix, is in contact with the ink, the potential in the ink becomes unstable, and stable ejection becomes difficult.

[0011]

The above-mentioned electrostatic ink jet printers require a high voltage,
As an electrostatic ink jet printer that solves problems such as unstable flying of toner and deterioration of print quality, a printer having a structure shown in FIG. 8 has been proposed. In this printer,
A gate plate 19 having a gate electrode 19a is provided between the counter electrode 13 and the plurality of recording electrodes 12.

In the above proposed electrostatic ink jet printer, the distance between the recording electrode 12 and the gate electrode 19a is kept constant so that the toner 26 flies relatively stably. When a pulse voltage is applied to the electrode 12, toner may also be ejected from the electrodes on both sides. Further, if there is a positional deviation (manufacturing error) at the time of assembling the plurality of gate holes 20 formed in the gate plate 19 with the recording electrode 12 or a disturbance during the recording operation, the adjacent gate electrode In some cases, the ink may be ejected in the 19a direction. Further, when there is a manufacturing error or an influence due to disturbance during a recording operation, the toner 26 flying from the recording electrode 12 does not pass through the gate hole 20 properly and reaches the gate electrode 19 a of the gate plate 19. May drip.

In view of the above, the present invention stabilizes the flying of the charged toner between the recording electrode and the counter electrode, prevents the flying toner from dropping on the gate electrode, and further increases the cost. It is an object of the present invention to provide an electrostatic ink jet printer that can improve the reliability of a recording head unit without using the same.

[0014]

In order to achieve the above object, an electrostatic ink jet printer of the present invention incorporates an ink in which a charged toner is contained in an insulating solvent,
A recording head for discharging the toner in the ink from the discharge port to the outside, wherein the recording heads extend in parallel with each other and discharge the toner from the discharge port by electrostatic force when a pulse voltage is applied. A plurality of recording electrodes, one counter electrode located at a predetermined distance from the plurality of recording electrodes in the toner discharge direction, and extending in parallel with the direction in which the plurality of recording electrodes are arranged; and the recording electrode and the counter electrode. And a gate electrode disposed between the two electrodes, wherein the gate electrode includes an inner gate electrode facing the recording electrode and an outer gate electrode facing the counter electrode. It is characterized by comprising two or more independent electrodes.

In the electrostatic ink jet printer according to the present invention, a good condition is obtained between the recording electrode to which the pulse voltage is applied and two or more electrically independent gate electrodes including the inner gate electrode and the outer gate electrode. The lines of electric force are generated, and the flying toner is accurately guided by the lines of electric force. Therefore, the flying toner reaches the recording medium without dropping on the gate electrode. In addition, basically, the above effect can be realized by increasing the number of gate electrode layers, so that no significant cost increase is caused.

Preferably, the inner gate electrode and the outer gate electrode are set to mutually different potentials. In this case, the potential of the inner gate electrode is Vg (1), the potential of the outer gate electrode is Vg (2), and the potential of the recording electrode is Ve.
j, It is preferable that the relationship of Vej> Vg (1)> Vg (2)> Vop is satisfied when the potential of the counter electrode is Vop.

Preferably, when the distance between the inner gate electrode and the recording electrode is d (1) and the distance between the outer gate electrode and the recording electrode is d (2), The relationship Vej-Vg (1)) / d (1) <(Vej-Vg (2)) / d (2) holds.

The inner gate electrode may be divided into a plurality of parts corresponding to the plurality of recording electrodes, and a potential of each of the divided inner gate electrodes may be controlled independently of each other. In addition, it is preferable that each of the divided inner gate electrodes is held at a constant bias potential during non-recording, and the potential of the electrode corresponding to the recording electrode to which the pulse voltage is applied changes during the recording operation.

[0019]

The present invention will be described in more detail with reference to the drawings. FIG. 1 is a perspective view showing a recording head unit of an electrostatic inkjet printer according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a main part of the recording head unit in FIG.
In FIG. 1, a part of the upper cover and the lower cover are partially omitted, and in FIG. 2, the gate electrode is cut at the same level position as the recording electrode for easy understanding.

As shown in FIG. 1, the recording head according to the present embodiment comprises an ink supply port 36 and an ink chamber 20.
And an ink discharge port (not shown) for discharging surplus ink to the ink circulation path. The ink supply port 36 is
It is connected to an ink circulation path formed by a tube communicating with an ink tank (not shown). The recording head further includes an upper cover 24 that forms the ink chamber 20.
And a lower cover 23, a base film 37 sandwiched between both covers 23 and 24, and a substrate 31 made of an insulator such as glass for supporting the base film 37 from the back side.
And In the ink chamber 20, ink containing toner charged positively or negatively by a charge control agent or the like in an insulating solvent is temporarily stored by being taken in from an ink circulation path via an ink supply port 36. Is done.

The base film 37 is made of an insulator,
A plurality of recording electrodes 22 are provided on the surface. The recording electrode 22
A conductive material having a predetermined thickness is pattern-plated on the base film 37. The conductive material extends substantially in the ink discharge direction and in parallel with each other, and is arranged at a recording resolution pitch in the width direction of the substrate 31. Each recording electrode 22 has a leading end projecting from an end of the base film 37 and a trailing end connected to a driver (not shown) provided on the printer body side. When a high-voltage pulse is selectively applied during a recording operation, each recording electrode 22 causes the toner 2 to generate electrostatic force.
6 is discharged from the discharge port.

The upper cover 24 is formed of an insulating member having an opening at the tip end and an ink supply port 36 formed therein. The upper cover 24 forms a slit-shaped discharge port with the base film 37 to form a discharge port. The portion has an ink meniscus. The lower cover 23 is made of an insulating member having an ink outlet (not shown). The ink taken from the ink supply port 36 is supplied to the upper cover 24 of the ink chamber 20.
From the side, it passes between the recording electrodes 22, flows into the lower cover 23 side of the ink chamber 20 from the vicinity of the discharge port, and returns to the circulation path from an ink discharge port (not shown) together with excess toner particles.

A counter electrode 33 is disposed at a position separated from the tip of each recording electrode 22 by a predetermined distance in the toner discharging direction. The counter electrode 33 is located on the back of the fed recording paper 25 and extends in parallel with the direction in which the plurality of recording electrodes 22 are arranged.

A migration electrode 21 extends inside the upper cover 24 at the rear end of the ink chamber. When a voltage (migration voltage) having the same polarity as the toner potential is applied to the migration electrode 21, the toner particles in the ink in the ink chamber 20 are electrophoresed by the electric field between the migration electrode 21 and the counter electrode 33. It moves to the vicinity of the recording electrode 22 due to the phenomenon. Therefore, in addition to the supply of the toner particles to the vicinity of the ejection port due to the forced ink circulation by the pump, the movement of the toner particles by electrophoresis causes the toner particle concentration in the vicinity of the ejection port to be relatively high compared to the upstream side of the ink chamber 20. Become higher.

Between the recording electrode 22 and the counter electrode 33,
A gate plate 29 is provided. The gate plate 29 extends in parallel with the direction in which the plurality of recording electrodes 22 are arranged and in parallel with the counter electrode 33. Gate plate 29
Comprises an insulating plate material 29a and two layers of gate electrodes respectively disposed on the front and back of the insulating plate material 29a. The two-layered electrode is an inner gate electrode 38 located on the recording electrode 22 side.
And an outer gate electrode 39 located on the opposite electrode 33 side. At the position of the gate plate 29 facing each recording electrode 22, the gate hole 3 penetrates the inner gate electrode 38, the outer gate electrode 39 and the insulating plate material 29a.
0 is formed. Each of the gate holes 30 has a smaller diameter on the outer gate electrode 39 side than on the inner gate electrode 38 side. The inner gate electrode 38 and the outer gate electrode 39 are insulated from each other and are maintained at different potentials, and each is independently controlled electrically.

In this embodiment, the inner gate electrode 38
Is the potential of Vg (1), and the potential of the outer gate electrode 39 is Vg (2).
, The potential of the recording electrode 22 is Vej, and the potential of the counter electrode 33 is Vej.
When op is set, the relationship of Vej> Vg (1)> Vg (2)> Vop is established. Further, the distance between the inner gate electrode 38 and the recording electrode 22 is represented by d (1).
And when the distance between the outer gate electrode 39 and the recording electrode 22 is d (2), (Vej-Vg (1)) / d (1) <(Vej-Vg (2)) / d The relationship of (2) holds.

In the electrostatic ink jet printer having the above structure, when a pump (not shown) is operated, ink flowing in the circulation path is discharged from the ink supply port 36 through the ink chamber 20 through the ink discharge port, and Return to During this time, when a pulse voltage is applied to any one of the plurality of recording electrodes 22, the applied recording electrode 22
A line of electric force indicated by an arrow 27 in FIG. 2 is generated between the inner gate electrode 38 and the outer gate electrode 39. The toner 26 that has been ejected from the ejection port by the electrostatic force generated by the migration electrode 21 and the recording electrode 22 is appropriately guided by electric force lines 27. Therefore, even if there is a misalignment between the gate hole 30 and the recording electrode 22, the flying toner 2
6 can pass through the gate hole 30 properly.
Therefore, the yield can be improved and the recording head can be manufactured at low cost, and the flying toner 26 can be deposited on the recording paper 25 with high positional accuracy to obtain good recording quality.

Next, a second embodiment according to the present invention will be described. FIG. 3 is a cross-sectional view showing a main part of the recording head unit of this embodiment, and FIG. 4 is a front view showing an individually configured inner gate electrode as viewed from the recording electrode side.

In this embodiment, the inner gate electrode 40
The other configuration is the same as that of the first embodiment. The inner gate electrode 40 is divided into a plurality of pieces arranged at the same pitch corresponding to the plurality of recording electrodes 22, and the potential of each inner gate electrode 40 is controlled separately from the outer gate electrode 39 and independently of each other. .

Each inner gate electrode 40 is held at a constant bias potential during non-recording, and the potential of the inner gate electrode 40 corresponding to the recording electrode 22 to which the pulse voltage has been applied changes during a recording operation. That is, the inner gate electrode 40
In the normal state, the potential difference between the recording electrode 22 and the recording electrode 22 is maintained at a high potential that does not exceed the threshold value for discharging the toner.
, The potential of the inner gate electrode 40 corresponding to.
Accordingly, the potential of the inner gate electrode 38 corresponding to the recording electrode 22 on both sides of the recording electrode 22 to which the pulse voltage is applied is maintained higher than the potential of the inner gate electrode 38 corresponding to the recording electrode 22 to which the pulse voltage is applied. Is done.

According to the electrostatic ink jet printer of this embodiment, even when the positional deviation between the recording electrode 22 and the gate electrode is large, or when there is an influence of disturbance or the like, the recording electrode 22 and the inner gate electrode 40 can be connected to each other. Correspond electrically in a one-to-one relationship during ejection. Thereby, the toner 26
Can fly accurately and reliably in the direction of the corresponding gate hole 30, reach the gate hole 30 and pass through the hole 30. Therefore, the accuracy of the landing position of the flying toner 26 can be further improved, and the recording quality can be further improved.

In this embodiment, the gate plate 2
9 can be composed of, for example, a TAB tape used in TAB (Tape Automated Bonding) technology. In this TAB tape, the electrode pads leading to the respective inner gate electrodes 40 are drawn out to the end of the TAB tape, and further drawn out of the portion to the outside of the recording head section by bonding means such as bonding.

In the first and second embodiments, the structure in which the gate plate 29 is provided with a two-layer gate electrode of the inner gate electrode 38 (or 40) and the outer gate electrode 39 is shown. However, the number of gate electrodes is not limited to this, and three or more layers can be formed. As described above, when forming n layers exceeding two layers, the potential relationship between the electrodes is as follows.

That is, the inner gate electrode 38 (or 4)
0) is set to Vg (1), the inner gate electrode 38 (or 4).
0), the potential of the outer gate electrode 39 of the nth layer is set to Vg (n).
, The potential of the recording electrode 22 is Vej, and the potential of the counter electrode 33 is Vej.
When op is set, Vej> Vg (1)> ... Vg (n-1)> Vg (n)> Vop. Further, the distance between the inner gate electrode 38 (or 40) and the recording electrode 22 is d (1), and
When the distance between the outer gate electrode 39 of the n-th layer and the recording electrode 22 is d (n), (Vej-Vg (1)) / d (1) <(Vej-Vg (n)) / d (n) is set. According to this configuration, more favorable ink flying than the first and second embodiments can be obtained.

Although the present invention has been described based on the preferred embodiment, the electrostatic ink-jet printer of the present invention is not limited to the configuration of the above-described embodiment. The electrostatic inkjet printer in which various modifications and changes have been made from the configuration described above is also included in the scope of the present invention.

[0036]

As described above, according to the electrostatic ink jet printer of the present invention, the recording electrode to which the pulse voltage is applied and the two electrically independent two layers including the inner gate electrode and the outer gate electrode. Good lines of electric force are generated between the above-mentioned gate electrodes, and flying toner can be accurately guided by the lines of electric force. Therefore, the flying toner can reach the recording medium without dropping on the gate electrode.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a recording head unit of an electrostatic inkjet printer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a main part of a recording head unit in FIG.

FIG. 3 is a cross-sectional view illustrating a main part of a recording head unit of an electrostatic inkjet printer according to a second embodiment of the present invention.

FIG. 4 is a front view of a gate electrode of the recording head unit of FIG. 3 as viewed from the recording electrode side.

FIG. 5 is a perspective view of the vicinity of a discharge unit of a recording head of a conventional electrostatic ink jet printer.

FIG. 6 is an enlarged plan view illustrating a main part of the recording head of FIG. 5;

FIG. 7 is a side sectional view showing a main part of the recording head of FIG. 5;

FIG. 8 is a cross-sectional view showing a main part of a recording head of a conventional electrostatic ink jet printer.

[Explanation of symbols]

 22 Recording Electrode 25 Recording Paper 26 Toner 29 Gate Plate 29a Insulating Plate 33 Counter Electrode 38, 40 Inner Gate Electrode 39 Outer Gate Electrode

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Mizoguchi Niigata Prefecture Kashiwazaki-shi, 7546 Yasuda, Niigata Nippon Electric Co., Ltd. (72) Inventor Hitoshi Minemoto 746 Yasuda, Kashiwazaki-shi, Niigata Niigata Nippon Electric (72) Inventor Hitoshi Takemoto 7546 Yasuda, Kashiwazaki City, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. (72) Inventor Kazuo Shima 7546 Yasuda Oaza, Kashiwazaki City, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. 7546 Yasuda, Kashiwazaki, Niigata Prefecture Niigata Nippon Electric Co., Ltd. (56) References JP-A-10-44428 (JP, A) JP-A-10-44432 (JP, A) JP-A 10-808 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B41J 2/06

Claims (5)

(57) [Claims] A recording head section for taking in an ink containing a charged toner in an insulating solvent and discharging the toner in the ink from a discharge port to the outside, wherein the recording head sections extend in parallel with each other. A plurality of recording electrodes for discharging toner from the discharge port by electrostatic force when a pulse voltage is applied, and a plurality of recording electrodes located at a predetermined distance from the plurality of recording electrodes in a toner discharge direction and In an electrostatic ink jet printer having one counter electrode extending in parallel with the arrangement direction and a gate electrode provided between the recording electrode and the counter electrode, the gate electrode faces the recording electrode. Characterized by comprising two or more layers of electrodes that are electrically independent from each other, including an inner gate electrode that contacts the outer gate electrode and an outer gate electrode that faces the counter electrode. Printer. 2. The inner gate electrode and the outer gate electrode are set to different potentials from each other, and the potential of the inner gate electrode is set to Vg (1), and the potential of the outer gate electrode is set to Vg (1).
(2) The electrostatic capacitance according to claim 1, wherein the relationship of Vej> Vg (1)> Vg (2)> Vop is satisfied, where Vej is the potential of the recording electrode and Vop is the potential of the counter electrode. Type inkjet printer. 3. When the distance between the inner gate electrode and the recording electrode is d (1) and the distance between the outer gate electrode and the recording electrode is d (2), (Vej-Vg The electrostatic ink jet printer according to claim 2, wherein a relationship of (1)) / d (1) <(Vej-Vg (2)) / d (2) is satisfied. 4. The internal gate electrode according to claim 1, wherein the inner gate electrode is divided into a plurality of parts corresponding to the plurality of recording electrodes, and a potential of each of the divided inner gate electrodes is controlled independently of each other. Electrostatic inkjet printer. 5. Each of the divided inner gate electrodes comprises:
5. The electrostatic ink jet recording head according to claim 4, wherein a constant bias potential is held during non-recording, and a potential of an inner gate electrode corresponding to a recording electrode to which a pulse voltage is applied changes during a recording operation.