JPH05208491A - Ink jet recording head and ink jet recorder - Google Patents

Abstract

PURPOSE:To obtain a long-life recording head and device realizing a smooth air flow, a stable electric field, a reduction of an interelectrode reaction, and a constantly stable ink delivery with respect to an ink jet recording applied for a print-out equipment of every type. CONSTITUTION:Air discharge ports 17 discharging air flows at a constant rate are disposed opposedly to ink delivery ports 16, 24, in which ink is held. An electric potential difference is provided between an attracting electrode 18 disposed on the surfaces of the air discharge ports 17 and a control electrode 26 disposed near the ink delivery port 24 to deliver the ink in the ink delivery ports 16, 24 out of the air discharge ports 17. The control electrode 26 is provided in an ink chamber 25 orthogonally to the attracting electrode 18. The control electrode 26 is partially electrically insulated by an insulating film 28 except the vicinity of the ink delivery port 24. The control electrodes 26 in the vicinity of the ink delivery ports 24 are isolated from each other by partition walls 23. In this manner, a head is characterized by its long life and stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for recording characters and images on a recording medium by ejecting liquid droplets from minute openings, and an ink jet recording apparatus using this recording head.

[0002]

2. Description of the Related Art There are various types of ink jet recording technology, but a method is known in which ink is attracted by electrostatic force, ink is drawn out from an opening, and recording is performed with ink dots.

As for the conventional ink jet recording head, an electrostatic suction type ink jet recording head utilizing electrostatic force and air flow called a beam jet will be described with reference to FIG. In FIG. 4, 1 is a head body, 2 is an ink ejection plate, and 3 is an air ejection plate. An ink chamber 4 and an air chamber 5 are formed in the head body 1, a plurality of ink ejection ports 6 are formed in the ink ejection plate 2, and a plurality of air opposed to each ink ejection port 6 is formed in the air ejection plate 3. The discharge port 7 is formed. On the back surface of the ink ejection plate 2,
An independent control electrode 8 is provided around each ink ejection port 6, and a common suction electrode 9 is provided on the surface of the air ejection plate 3 so as to surround each air ejection port 7. Each control electrode 8
A plurality of signal sources 10 corresponding to the respective control electrodes 8 are connected between and the common suction electrode 9. In the recording preparation stage, the air supplied to the air chamber 5 through the air supply pipe 5a causes an air flow having a constant flow rate to flow from the air discharge port 7 and the ink supplied to the ink chamber 4 through the ink supply pipe 4a. As a result, the meniscus of the ink is stably held in the ink ejection port 6. When a potential difference is generated by the voltage applied from the signal source 10 between the suction electrode 9 and the control electrode 8, the meniscus of the ink generated in the ink ejection port 6 is drawn out toward the air ejection port 7 and then from the air ejection port 7. Since the air flow is flowing out, the ink drawn out flies while being accelerated by the air flow and reaches the recording paper arranged in front of the air ejection port 7 to form an ink dot pattern. The voltage from the signal source 10 is applied to each control electrode 8 through the signal wiring 10a, but the signal wiring 10a is arranged in the arrangement direction of the ink ejection ports 6 in a plane substantially perpendicular to the ejection direction of ink and air as shown in the drawing. The head body 1 is drawn out to the right and left at right angles.

[0004]

However, in the above-mentioned conventional configuration, the signal wiring 10a for drawing the control electrode 8 to the outside of the head body is arranged across the air chamber 5 and in parallel with the suction electrode 9. There is a problem.
The first is that it obstructs the flow of air because it traverses the air chamber 5. That is, when the airflow flows into the gap between the ink ejection port 6 and the air ejection port 7 and is ejected from the air ejection port 7, the flow is obstructed by the signal wiring 10a and becomes a turbulent flow or a vortex occurs. In some cases, the uniformity of the air flow velocity from each air discharge port 7 may be impaired, and the air may be bent in the discharge direction. Secondly, since the signal wiring 10a and the suction electrode 9 are parallel and close to each other, an electric field which is inconvenient for ink ejection may be generated between them. As an electrostatic suction type ink jet, ideally, an electric field should be generated between the ink meniscus generated in the ink ejection port 6 and the suction electrode 9, and it is not necessary to generate it in other places. However, in the conventional configuration, an electric field is generated over a wide range between the parallel signal wiring 10a and the attraction electrode 9, and in the case of the multi-nozzle configuration as shown in the figure, the plurality of signal wirings 10 are formed.
There is a large change in the state of the electric field between when there is a signal input to a and when there is an input to the independent signal wiring 10a, which becomes a phenomenon like mutual interference between the signal electrodes, and the recording characteristics are It may deteriorate. In particular, when the signal voltage is high, it has been confirmed that when the ejection signals are simultaneously input to all the ink nozzles, the ejection amount suddenly increases and an abnormal ejection state in which the ink ejection direction bends occurs. .. We call this abnormal discharge.

A signal voltage is independently applied to each control electrode 8 from each signal source 10, and ink is ejected only from the ink ejection port of the control electrode to which the signal voltage is applied. Is generated and a control electrode to which no voltage is applied is generated, and a potential difference is generated between them. Therefore, in a portion of the plurality of control electrodes 8 where a potential difference is generated between the adjacent control electrodes, a current flows in that portion. Although the electrostatic suction type inkjet recording head uses an insulating ink so that the recording electrodes are not short-circuited and destroyed, the ink is ejected with very highly insulating ink. Ink having a specific resistance of 10 ⁶ to 10 ⁹ Ωcm is generally used because of poor characteristics. For this reason, a minute current may flow between the recording electrodes to cause an electrode reaction or electrolysis, and the control electrode may dissolve in the ink and disappear.
There is a problem that the ink is deposited on the control electrode to cause clogging.

The present invention solves the above-mentioned problems of the prior art. It is easy to make the air flow uniform, a stable electric field can be formed for ink ejection, and there is no electrode consumption or ink deposition. An object of the present invention is to provide an inkjet recording head capable of stable recording for a long time and an inkjet recording device using this recording head.

[0007]

In order to achieve the above object, the present invention has a structure in which a recording head is configured to take out a plurality of control electrodes in a direction orthogonal to a suction electrode, and an outlet of an ink ejection port of each control electrode. Except for the vicinity, the portion contacting the ink is insulated, and each control electrode is isolated from each other by a partition wall.

[0008]

According to the present invention, since the control electrode is provided in the direction orthogonal to the suction electrode and is pulled out from the rear of the recording head through the inside of the ink chamber, the portions close to each other are near the ink ejection port. Since the electric field for ejecting ink is concentrated on the ink ejection port, ejection is stabilized. In addition, since there is no signal wiring in the air chamber for letting out the air, the stability of the air flow is greatly improved. Further, the portion where the control electrode is in contact with the ink is only in the vicinity of the outlet of the ink ejection port, and in that portion the control electrodes are isolated from each other, so when a potential difference occurs between the adjacent control electrodes, The current will flow around the partition wall, and the resistance value between the electrodes will be much larger than in the conventional case. Therefore, the resistance value between the electrodes becomes much larger than the conventional one, the current value is greatly reduced, and the electrolysis and electrode reaction as in the conventional case are reduced, so that the life of the recording electrode is extended and ,
Ink deposition can be eliminated. In other words, in the conventional configuration, it is necessary to develop an ink in which an electrode reaction is less likely to occur and to select an electrode material with less electrode consumption. However, the configuration of the present invention allows the degree of freedom in selecting the ink and the electrode material. Can be considered to increase significantly.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an ink jet recording head in one embodiment of the present invention, FIG. 1 (a) is a front view of the recording head, and FIG. 1 (b) is a sectional view taken along the line AA of FIG. FIG. 2 is an exploded perspective view of the head body portion excluding the ink ejection port and the air ejection port of FIG. In FIG. 1, 11 is a head body portion, 12 is an ink ejection plate, and 13
Is a spacer for forming the air flow path 14, 15 is an air ejection plate, 16 is an ink ejection port formed in the ink ejection plate 12, 17 is an air ejection port formed in the air ejection plate 15,
A common suction electrode 18 is provided on the surface of the air discharge plate 15 around the air discharge port 17.

The head body 11, as shown in FIG.
It is composed of an ink supply plate 19, a control electrode plate 20, and air supply plates 21 and 22 sandwiching these from both sides. The ink supply plate 19 has a partition wall 2 on its back surface and a front end portion.
A plurality of groove-shaped ink discharge ports 24 formed by
And a common ink chamber 25 that communicates with each of these ink ejection ports 24. On the other hand, a plurality of control electrodes 26 are formed on the surface of the control electrode plate 20 whose rear end portion is longer than the ink supply plate 19 in accordance with the pitch of each ink ejection port 24. Signal terminal 2 at the rear end
It is formed as 7. Each control electrode 26 is covered with an insulating film 28 except for the outlet portion of each ink ejection port 24 and the signal terminal 27. Also, the air supply plate 2
The air chambers 29 and 30 are formed in the inner portions of the Nos. 1 and 22, respectively. The head body portion 11 is formed by stacking and joining the ink supply plate 19, the recording electrode 20, and the air supply plates 21, 22 to each other. In this state, the center of each ink ejection port 24 is located at each control electrode 26.
The partition wall 23 is located between the control electrodes 26 adjacent to each other, and the rear end portion of the control electrode plate 20 having the signal terminal 27 is exposed.

In the ink jet recording head configured as described above, a potential difference is selectively provided between each control electrode 26 and the common suction electrode 18 from an individual signal source corresponding to each control electrode 26. The ink in the ink ejection port 24 supplied from the ink chamber 25 is
The air that is supplied from 9, 30 and flows through the air flow path 14 flies from the air discharge port 17 and adheres to the recording paper to perform recording. The ink supply port 2 is provided in the ink chamber 25.
Ink is supplied from the ink supply source through 5a, and air is supplied from the air supply source to the air chambers 29 and 30 through the air supply ports 29a and 30a.

In the ink jet recording head according to the present embodiment, since the control electrode 26 and its wiring portion are not present in the vicinity of the suction electrode 18, a stable electric field state is realized. That is, in the conventional configuration, the distance between the control electrode or the signal wire and the suction electrode is about 0.4 mm, and when the potential difference between the control electrode and the suction electrode exceeds 950 V, a signal is applied to all the control electrodes at the same time. At that time, the electric field was disturbed and the above-mentioned abnormal ejection occurred, but in the configuration of this embodiment,
It was confirmed that ink was ejected normally even if the potential difference exceeded 1.2 kV.

Good results were also obtained with respect to the air flow. When there is an unstable factor in the air flow, fluctuation in the ink ejection direction due to the instability of the air flow is an item that affects the recording characteristics. This wobble appears as a dot misregistration on the paper surface. With the conventional head, when the distance between the head and the paper surface was set to 1.5 mm, the dot misalignment was about 30 μm, but under the same conditions. In the configuration of the present embodiment described above, the thickness was set to about 10 μm or less.

Further, there was a great effect on the electrode reaction. 3A is a partially enlarged front view of the head body portion, and FIG. 3B is a sectional view taken along line BB of FIG. 3A.
In FIG. 3, each rectangular ink ejection port 24 is partitioned by a partition wall 23, and the control electrode 26 is wired in a direction parallel to the ink ejection direction, that is, a direction orthogonal to the suction electrode 19, to eject the ink. The outlet 24 is covered with an insulating film 28 except for the portion having the length Le at the outlet. Therefore, when a potential difference occurs between the adjacent control electrodes 26, the current flowing in the ink is controlled by the control electrodes 26.
Flows from the exposed portion of the length Le of the control electrode 26 toward the adjacent exposed portion of the control electrode 26.
It will flow by bypassing the length Lp of 3. As a result,
The electrical resistance value between the adjacent control electrodes 26 increases, and the flowing current value decreases.

The current value in such a structure is determined by the length Le of the exposed portion of the control electrode 26, the length Lp of the partition wall 23, the physical value (specific resistance) of the ink, etc. It is advisable to determine the physical property value of the ink by giving priority to the ejection characteristics and the printability on the recording paper, so that the degree of freedom in ink selection is emphasized, and the control electrode 26 that is inexpensive and easy to wire is used.
However, by setting the above Lp and Le so that the current value with less electrode reaction is set in consideration of the characteristics for the electrode reaction, the degree of freedom in selecting the material of the ink and the control electrode is increased, and the cost is low. A stable inkjet recording head can be realized.

Incidentally, the ink supply plate 19 in this embodiment.
The control electrode plate 20 is made of plastic, ceramic,
An insulating material such as glass or silicon is used, and the suction electrode 18 and the control electrode 26 are made of gold, silver,
Metals such as copper, aluminum, chromium, tungsten, and platinum, and other conductive materials can be used. The insulating film 28 can be made of an organic resin such as polyimide or epoxy, or an inorganic material such as low-melting glass, SiO, or SiO _2. However, considering the ease of head assembly, the ink supply plate 19 and It is preferable to use a material that has good insulating properties and can also be used as an adhesive so that the material that joins the control electrode plate 20 also serves as the insulating film 28. Insulation of the control electrode 26 and joining during head assembly It is effective to manufacture the head by simultaneously performing the above.

[0017]

As described above, according to the present invention, the recording head has a structure in which a plurality of control electrodes are taken out in the direction orthogonal to the surface of the suction electrode, and each control electrode is insulated except for the vicinity of the outlet of the ink ejection port. Moreover, since each control electrode is isolated from each other by the partition wall, a stable electric field is always generated, the flow of the airflow is uniform and smooth, and there is no electrode reaction electrolysis, electrode consumption and ink It is possible to realize an excellent inkjet recording head that does not cause precipitation, has a long life, and is not clogged, and an inkjet recording apparatus that uses this recording head.

[Brief description of drawings]

FIG. 1A is a front view of an inkjet recording head according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA of FIG.

FIG. 2 is an exploded perspective view of a head body portion of the recording head.

3A is a partially enlarged front view of the head body portion, and FIG. 3B is a sectional view taken along line BB in FIG. 3A.

4A is a front view of a conventional electrostatic suction type inkjet recording head, and FIG. 4B is a cross-sectional view taken along line CC of FIG. 4A.

[Explanation of symbols]

 11 Head Body Part 12 Ink Ejection Plate 13 Spacer 14 Air Flow Path 15 Air Ejection Plate 16 Ink Ejection Portion 17 Air Ejection Port 18 Suction Electrode 19 Ink Supply Plate 20 Control Electrode Plate 21, 22 Air Supply Plate 23 Partition Wall 24 Ink Ejection Port 25 ink chamber 25a ink supply port 26 control electrode 27 signal terminal 28 insulating film 29, 30 air chamber 29a, 30a air supply port

Claims (5)

[Claims] 1. An ink supply plate having a plurality of groove-shaped ink discharge ports partitioned by a partition wall and a common ink chamber communicating with each of these ink discharge ports; A control electrode plate having a plurality of control electrodes separated from the ink discharge port through an ink chamber and separated by the partition wall, and interposed between the ink supply plate and the control electrode plate, and at least Means for insulating each control electrode except near the outlet of the ink ejection port, an air ejection plate having a plurality of air ejection ports facing each of the ink ejection ports, and a surface of the air ejection plate. A common suction electrode provided around the air discharge port, an air flow path formed between each ink discharge port and the air discharge port, and an air chamber for supplying air to the air flow path Ink Jet recording head. 2. The ink jet recording head according to claim 1, wherein the bonding material for bonding the ink supply plate and the control electrode plate also serves as a means for insulating the control electrode. 3. The ink jet recording head according to claim 1, further comprising an air supply plate having air chambers for supplying air to the air flow path on both sides of the ink supply plate and the control electrode plate which are overlapped with each other. 4. An ink ejection plate having an ink ejection port facing each ink ejection port is disposed on the front surface of the ink supply plate and the control electrode plate which are overlapped with each other, and between the ink ejection plate and the air ejection plate. The ink jet recording head according to any one of claims 1 to 3, wherein an air flow path is formed in the air flow path. 5. An ink jet recording apparatus in which a plurality of signal sources corresponding to the respective control electrodes are connected between the respective control electrodes and suction electrodes of the ink jet recording head according to any one of claims 1 to 4.