JPH1110885A - Recording head of ink jet recording device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the accurate manufacturing of a recording head by a method wherein the recording head consists of a recording cell, in which discharging electrodes are provided on the wall surfaces of a plurality of nozzle grooves, and a cover, which forms a plurality of nozzle holes by covering the nozzle grooves under the state being placed on the recording cell. SOLUTION: In a recording cell, a plurality of strips of nozzle grooves 2 and discharging electrodes 5 for applying voltage to ink on the bottom wall surfaces of the nozzle grooves are provided. In addition, wirings 8 connecting to a recording signal voltage generating power source 7 for generating recording signal voltages necessary for discharging ink in the discharging electrodes 5 are joined to wiring joining parts 6 formed at the extension base parts of the discharging electrodes 5. A cover 10 provided opposite to the recording cell 1 is made of an insulating sheet having nearly the same size as that of this recording cell. By joining the joining surface 9 of the recording cell 1 and the cover 10, each nozzle groove 2 turns to be a nozzle hole, at the terminal point of which an opening 4 for discharging ink is formed, by being covered and a tank groove 3 forms an ink tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head of an ink jet recording apparatus for recording an image by ejecting ink from a nozzle hole, and more particularly to an electrostatic induction type in which ink is drawn out of the nozzle hole by an electrostatic force to fly. The present invention relates to a recording head in an ink jet recording apparatus and a method for manufacturing the same.

[0002]

2. Description of the Related Art An electrostatic induction type ink jet recording apparatus is provided with a discharge electrode in contact with ink, and a counter electrode for drawing out ink opposite to the discharge electrode, and applies a voltage between the discharge electrode and the counter electrode. Thus, the ink is caused to fly by electrostatic force, and the flying ink is attached to paper or the like, which is a printing medium positioned in front of the counter electrode, to record an image. In such a recording apparatus, since there is no mechanically moving part, the life of the apparatus can be extended.

In an electrostatic induction type ink jet recording apparatus called a slit jet, a plurality of ejection electrodes for applying a voltage for causing ink to fly are arranged in one slit opening, and each of the electrodes has a voltage sufficient to cause the ink to fly. Is applied to fly the ink.

[0004] In a slit-jet type ink jet recording apparatus, an ink having no conductivity is used so that when a potential difference occurs between adjacent discharge electrodes, dielectric breakdown does not occur between the discharge electrodes. Generally, semiconductive (1
Since an ink of about 00 MΩcm) is used, a current actually flows between the electrodes, and thus there has been a problem of destruction of the electrodes due to sparks or the like and clogging due to deposition of the ink.

In order to solve such a problem, an ink jet recording apparatus disclosed in Japanese Patent Application Laid-Open No. 5-208501 prevents ink from erroneously flying due to a recording signal voltage applied to an adjacent electrode. In addition, in order to prevent a current from flowing between the adjacent electrodes, a partition wall is provided, and an insulating film is provided on almost all of the portions that come into contact with the ink tank and the nozzle groove, thereby preventing destruction and clogging of the electrodes. . The recording head of this ink jet recording apparatus is manufactured by combining a flat plate provided with electrodes and a flat plate provided with nozzle grooves.

[0006]

Problems to be Solved by the Invention
In the ink jet recording apparatus disclosed in Japanese Patent Publication No. 1 (1993), a member having an ejection electrode for ejecting ink and a member having a partition wall are separated as separate components.
When two members are combined, there is a problem that the alignment is very difficult, and since the joining surfaces of those members have irregularities, joining is difficult. Further, two types of members are required to form a recording head.

An object of the present invention is to provide a recording head of an ink jet recording apparatus which can be manufactured with high accuracy, and a method of manufacturing the same.

It is another object of the present invention to provide a recording head of an ink jet recording apparatus having a high degree of integration and a method of manufacturing the same.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a recording method for an electrostatic induction type ink jet recording apparatus in which ink in a nozzle hole of a recording head is caused to fly by electrostatic force and adhere to a recording medium. The head was composed of a plurality of nozzle grooves, a recording cell provided with ejection electrodes on the wall surface of the nozzle groove, and a lid which formed a plurality of nozzle holes by overlapping the recording cell and covering the nozzle groove.

By providing the ejection electrode on the wall surface of the nozzle groove, there is no influence of displacement when the lid is overlapped, and the ink ejection accuracy is improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A feature of the present invention is that an ejection electrode for ejecting ink is provided in a nozzle groove formed in an insulating plate, and one embodiment thereof is shown in FIG.

In the embodiment shown in FIG. 1, the recording head comprises:
It comprises a recording cell 1 and a lid 10. The recording cell 1 having the nozzle groove and the discharge electrode extends from an ink tank (ink tank groove) 3 formed on the upper surface of the insulating plate to the edge along the upper surface toward the counter electrode (not shown), and is exposed to the outside air. A plurality of communicating nozzle grooves 2 are formed and each nozzle groove 2 is formed.
A discharge electrode 5 for applying a voltage to the ink on the bottom wall surface of
A wiring 8 connected to a recording signal voltage generation power supply 7 for generating a recording signal voltage required for ink ejection is joined to the ejection electrode 5 to a wiring joint 6 formed at the extension base of the ejection electrode 5. Each of the discharge electrodes 5 is formed by uniformly forming a conductive film on the nozzle groove forming surface of the insulating plate (recording cell 1) having the nozzle grooves 2 formed thereon by metal vapor deposition or sputtering, and then forming the conductive film between the nozzle grooves. A method in which the film is formed by removing and separating the film is preferable.

A cover 1 provided to face the recording cell 1
Numeral 0 is constituted by an insulating plate having substantially the same size as the recording cell.

The bonding surface 9 of the recording cell 1 and the lid 10
The nozzle groove 2 is covered to form a nozzle hole, and the terminal point thereof forms an opening (nozzle opening) 4 for discharging ink, and the tank groove 3 forms an ink tank. It is necessary that the wiring joint 6 be sufficiently sealed to prevent the ink from leaking.

Next, a printing method using such a recording head will be described. First, ink is filled in the ink tank groove (tank) 3 and each nozzle groove (nozzle hole) 2.
A recording signal voltage is applied to the discharge electrode 5 of the desired nozzle hole 2 requiring dot printing using the recording signal voltage generation power supply 7, and a counter electrode (not shown) on an extension of the opening 4 is applied. When a potential difference is generated, ink in the ink tank 3 is moved to the opening 4 through the nozzle groove 2 and flies according to an electric field generated between the discharge electrode 5 and the counter electrode. The flying ink adheres to a printing medium such as paper placed in front of the counter electrode to form (record) an image.

The recording head to be constructed and driven as described above is provided with the discharge electrodes 5 for discharging ink on the bottom wall surface of each nozzle groove 2, so that the electrode is different from the conventional recording head. It is possible to eliminate obstacles such as crosstalk due to a joining failure between the member provided with the groove and the member provided with the groove, and it is also possible to reduce the displacement of the ink flying position.
Further, since one groove is processed and one electrode is processed to discharge the ink, manufacturing and handling are facilitated. In the case of this embodiment, in particular, the nozzle groove 2
And the ink tank groove 3 are formed on the same surface of the insulating plate of the recording cell 1, so that the process of providing the nozzle groove and the ink tank groove is performed on only one surface, and the handling during manufacture is extremely easy Become.

Next, details of the constituent means in the embodiment will be described.

First, the size of the discharge electrode 5 will be described. Although the ejection electrode 5 is brought into contact with the ink, it is desirable that the area of the ejection electrode 5 be large in order to efficiently eject and fly the ink. Although the ink can be ejected even if the area of the ejection electrode in contact with the ink is small as in the conventional ink jet recording apparatus, the voltage required for the ejection increases. On the other hand, it has been confirmed that when the ejection electrode is enlarged to increase the contact area with the ink, the voltage required for ejecting the ink decreases. Therefore, it is better that the area of the ejection electrode is large. Therefore, in this embodiment, the area of the ejection electrode 5 is increased by increasing the length in the direction along the nozzle groove 2.

In the embodiment shown in FIG. 1, the discharge electrode 5
Although formed on only one surface of the bottom wall surface of the nozzle groove 2, as another embodiment for further increasing the area of the discharge electrode to lower the voltage required for ink discharge, a plurality of surfaces of the nozzle groove 2, For example, by forming electrodes on the bottom wall and both side walls, the contact area with the ink can be further increased, and the voltage required for ink ejection can be further reduced. Also,
As will be described later, the manufacturing method can be simplified, which is very convenient. In general, it is preferable to form the discharge electrodes 5 on all the wall surfaces (surfaces) of the recessed portions as the nozzle grooves 2.

In the embodiment shown in FIG. 1, the cross section of the nozzle groove 2 is square, but it is triangular or U-shaped.
Any shape such as a letter shape is acceptable. It is preferable that the discharge electrode is formed on a half or more of the wall area of the nozzle groove 2, and that the discharge electrode is formed on the entire wall surface of the nozzle groove 2.

As another embodiment for further increasing the area of the discharge electrode to lower the voltage required for ink discharge, a lid 10 for forming a nozzle hole covering the nozzle groove 2 of the recording cell 1 is provided.
A discharge electrode (lid-side electrode) is also provided on the surface facing the nozzle groove 2 in the above, and a cylindrical discharge electrode is formed by combining the lid-side electrode and the electrode formed on the wall surface of the nozzle groove 2. It is possible to have a structure similar to a rectangular ink nozzle, and to further reduce the voltage required for ink ejection.

Next, the recording signal voltage generated by the recording signal voltage generating power supply 7 will be described.

The recording signal voltage generated by the recording signal voltage generating power supply 7 needs a peak value and a pulse width which are sufficient for ejecting ink from the nozzle holes and causing the ink to fly. The voltage required to eject and fly the ink is about 1.5 kV to about 3 kV when the distance from the tip opening 4 of the nozzle groove 2 (nozzle hole) to the counter electrode (not shown) is about 1 mm.
Voltage. Since this voltage value changes depending on the size and shape of the recording cell, it is necessary to confirm it in actual application.

One voltage application method is a method of generating and applying a recording signal voltage (pulse voltage) having a value necessary for causing ink to fly. Normally, there is a method in which the discharge electrode 5 is set to the ground potential, and when the ink is to be ejected to fly, a voltage large enough to cause the ink to fly is applied for a desired time to cause the ink to fly. In this method, since a recording signal voltage is applied to the discharge electrode 5 only when desired, power is saved, and drying of the ink at the tip of the nozzle opening can be prevented.

In another voltage application method, a bias voltage is applied to the discharge electrode 5 in advance so that a meniscus of ink is sufficiently formed at the tip of the nozzle opening, and a recording signal voltage (pulse voltage) is applied to the bias voltage for a desired time. This is a method of ejecting ink in a superimposed manner. In this method, since the meniscus is formed in advance, the response speed is faster than in the former method, and high-speed printing is possible. Further, the recording signal voltage (pulse voltage) can be reduced. When a DC power supply is used for the bias voltage and the pulse voltage is generated using the DC power supply and the switching element, the voltage of the switching element can be reduced. Therefore, a small and highly integrated device using a switching element such as a power transistor or a power MOSFET can be used, and the drive circuit can be manufactured at low cost.
In this embodiment, while the former method applies a pulse voltage of 2 kV or more, the latter method uses
If a pulse voltage of about 200 V is generated for a bias voltage of about 1.7 kV, the ink can be ejected and fly. As power MOSFETs used to generate a pulse voltage of about 200 V, small and inexpensive power MOSFETs are supplied.

As another voltage applying method, there is a case where a bias voltage is applied to a counter electrode and a recording signal voltage is applied to an ejection electrode.

Next, the counter electrode and the printing medium will be described.

In this electrostatic induction type ink jet recording apparatus, ink is ejected and flies by an electrostatic force generated by an electric field generated between an ejection electrode and a counter electrode. This electric field reaches the counter electrode from the discharge electrode through ink, air, paper as a printing medium, or the like.

The voltage required to discharge and fly the ink can be set lower as the counter electrode is closer to the recording cell. However, if you get too close,
There is a danger that the printing medium, such as paper, will come into contact with the recording cells, resulting in poor printing. Therefore, it is preferable that the distance between the recording cell and the counter electrode is about 500 μm to about 1 mm. The distance is not limited to this range as long as a high-voltage power supply can be prepared.

In another embodiment, a configuration without using the counter electrode may be adopted. If a sufficient electric field is formed outward from the discharge electrode in the recording cell, the ink can be ejected, so that the printing medium such as paper is set to a potential at which a sufficient electric field can be formed. do it. Therefore, as one embodiment, when the printing medium such as paper is sufficiently discharged and brought to the ground potential, by applying a pulse voltage of about 3 kV to the discharge electrode, the ink is sufficiently discharged and caused to fly. Can be.

Next, the cell size will be described.

The recording head of the ink jet recording apparatus is
Although it is adapted to print an image with an image quality having a resolution of 100 dots / inch to 720 dots / inch, depending on the application, it is possible to cope with a lower resolution or a higher resolution. In one embodiment, 100 dots /
A case of a recording head having a recording density of inches will be described.

In the case of a recording head of 100 dots / inch, the nozzle interval must be about 254 μm. Therefore, each nozzle groove 2 of the recording cell 1 has a width of 100
It is appropriate that the thickness is about 150 μm and the depth is about 100 to 200 μm. However, the size is not limited to flying ink. The thickness of the discharge electrode 5 formed on the bottom wall of the nozzle groove 2 is preferably several μm or more. The length of the nozzle groove 2 is at least 200 μm or more and several mm
Is appropriate.

The size of the recording cell having the above dimensions is made of the recording cell 1 having a thickness of several mm, and the number of the nozzle grooves 2 formed in the lateral direction is not particularly limited. , About 800 lines (800 dots), up to 5000
It is sufficient that these can be arranged, but from the viewpoint of manufacturing easiness, it is preferable to arrange 256 lines corresponding to an 8-bit bus.

Next, a method of forming a nozzle groove, an ink tank groove, and the like will be described.

The first method is the easiest to machine the recording cell 1 using a cutting machine or the like.

The second method is to use an insulating plate (recording cell 1)
Is a method in which the insulating plate is burned by applying a laser or a heating means to the surface of the insulating plate to form irregularities. For example, desired nozzle grooves 2 and ink tank grooves 3 can be formed while heating and melting the acrylic plate using a heating means such as a soldering hand. Similarly, there is a method in which electric discharge is performed at a desired position to dent the insulating plate.

The third method is a method used for photoetching, sandblasting, or the like. Masking the insulating plate according to the shape of the unevenness to be formed to prevent erosion, and performing chemical erosion (photo etching) or mechanical erosion (sand blast) on the other portion to create unevenness. is there.

In addition to the above, mechanical, thermal, electromagnetic,
There is a method of chemically forming irregularities, but any method may be used.

The recording head manufactured as described above is
In this configuration, the nozzle grooves 2 (nozzle holes) are arranged in a line and the ink is ejected. However, in order to increase the degree of integration, the following embodiment can be adopted.

First, an embodiment in which a plurality of recording cells are overlapped to form a plurality of rows of nozzle hole groups will be described. Such a recording head is effective for increasing the printing speed, increasing the printing density, and performing color printing.

Since the back surfaces of the recording cells 11 and 12 are flat, as shown in FIG. 2, a plurality of recording cells 11 and 12 having nozzle grooves and ejection electrodes formed in the same manner as the recording cell 1 of FIG.
Are stacked in multiple stages to form a nozzle hole group therebetween, and the upper surface of the uppermost recording cell 11 is covered with a lid 10 to form another nozzle hole group. With this configuration, the upper recording cell 11 also functions as a lid for the lower recording cell 12, so that an increase in the thickness of the entire recording head can be reduced. Incidentally, the conventional recording head has a configuration in which a single row of nozzle holes is formed by using a pair of a recording cell having nozzle grooves and a lid having electrodes, so that it is attempted to form a plurality of rows of nozzle holes. Then, the recording cells and the lid must be alternately overlapped, and the thickness of the entire recording head is simply doubled.

However, as in the embodiment shown in FIG. 2, by using the back surface (lower surface) of the upper recording cell 11 to cover the nozzle grooves of the lower recording cell 12, a plurality of rows of nozzles are provided. Hole groups can be configured. Therefore, it is sufficient that the cover 10 is provided so as to cover the uppermost recording cell 11, so that a recording head having a plurality of rows of nozzle holes can be made relatively thin.

If the relative positions in the arrangement direction of the nozzle grooves (nozzle holes) of the recording cells 11 and 12 are made equal, for example, as shown in FIG. it can. If the number of stages is increased to three or four, the printing speed can be further improved.

The printing density can be improved by combining the recording cells 11 and 12 such that the relative positions in the arrangement direction of the nozzle grooves (nozzle holes) are alternated. For example, as shown in FIG. 2, the printing density can be doubled by combining two stages. Each row is 100
In the case of dots / inch, it is equivalent to 200 dots / inch. If the number of stages is increased to three or four, the printing density can be further improved.

Further, by changing the color of the ink used for each of the superimposed recording cells, it is possible to perform color printing. By using the above alternate combinations together,
A recording head with a higher degree of integration can be obtained.

As still another embodiment, it is possible to propose an embodiment in which, when a print head is formed by stacking print cells in multiple stages, the print cell having the same structure is used for the top cover. In this embodiment, as shown in FIG. 3, a lid to be stacked last is replaced with a recording cell 13. Thus, there is no need to make a dedicated insulating plate used for the lid, and the number of parts can be reduced.

The recording head configured as described above supplies the ink in the individual ink tanks 3 to the plurality of nozzle grooves 2 and discharges them. It is convenient to replace the recording head when the ink in the ink tank 3 runs out. However, in a recording head configured by superposing the recording cells in a plurality of stages, the ink consumption in each stage is different. In addition, if the ink tank in each recording cell is small, the ink in a specific recording cell may run out immediately. As another embodiment in which the measure is taken, a recording head that supplies ink from outside can be proposed.

FIG. 4 shows an embodiment in which an external ink tank is attached to the recording head. External ink tank 14
Represents each recording cell 1 of the recording head via the supply pipe 15.
1 and 12 are connected to the ink tanks 3. Thus, when the ink in the recording cell is consumed and the ink in the ink tank 4 becomes insufficient, the ink can be supplied from the external ink tank 14 to solve the ink shortage. If the external ink tank 14 is detachable and can be replaced, the shortage of ink in the external ink tank 14 can be solved. Further, when the external ink tank 14 is provided, a height difference can be created between the nozzle opening 4 and the ink liquid level of the external ink tank 14, and the ink pressurized or depressurized by the height difference is supplied to the nozzle opening 4. Can be supplied. For example, if the ink level of the external ink tank 14 is set to be lower than the position of the nozzle opening 4, the ink is drawn inward from the nozzle opening 4, so that it is difficult for the ink to be hardened due to drying. Further, the ink level of the external ink tank 14 is
If the height is set higher than the position, the ink can form a meniscus protruding outside the nozzle opening 4, so that the ink can be easily ejected and fly.

In the embodiment in which the external ink tank is provided as described above, the ink tank in the recording head can be omitted. In this way, interference between adjacent electrodes in the ink tank can be avoided.

In the recording head according to the above-described embodiment, if there is interference due to a potential difference between adjacent ejection electrodes, erroneous ejection, sticking of ink, or damage to the electrodes will occur. The distance between the electrodes in the part must be increased. As an embodiment for that purpose, a form in which the discharge electrode portion located in the ink tank is covered with an insulating member can be proposed. As a result, the ejection electrode does not come into contact with the ink in the ink tank, and comes into contact with the ink inside the nozzle groove, so that the influence between the adjacent ejection electrodes can be reduced.

As shown in FIG. 5, the process of covering the discharge electrode with an insulating member is performed by the ink tank groove 3 in the recording cell 1.
And the area of the nozzle groove 2 in the vicinity thereof is immersed in a tank 17 containing an insulating agent 16 so that an insulating film is adhered to the area. As another method, a method of masking the tip of the nozzle groove 2 (ejection electrode 5) and spraying an insulating treatment agent on the ink tank 3 and the nozzle groove 2 near the ink tank 3 to form an insulating film is also adopted. be able to. The thickness of the insulating film formed at this time is appropriately several μm, and if the thickness is about this thickness, even when bonding with the lid or another recording cell, a step generated in the covering portion and other portions is small, Joining can be performed without causing ink leakage. As the insulating agent, a fluoropolymer resin is appropriate.

As another embodiment for preventing the interference between the discharge electrodes, it is possible to propose a form in which the electrodes in the ink tank 3 and the nozzle groove 2 in the vicinity thereof are peeled off without performing insulation coating. In this case, as shown in FIG. 6, the electrode is peeled by immersing the ink tank 3 and a region in the vicinity thereof in a tank 19 of a peeling agent 18 containing a solvent or the like for dissolving a metal. As a result, the ink tank 3 and the electrode in the vicinity thereof are removed, and the discharge electrode 5 remains in the nozzle groove in an isolated state. The connection of the wiring 8 to each of the ejection electrodes 2 is made at the tip located at the nozzle opening as shown in FIG. However, it is preferable that the position on the ink tank 3 side is far from the nozzle opening.

Next, another embodiment in which the connection structure between the discharge electrode 5 and the wiring 8 is devised will be described. As described above, in a print head in which the discharge electrode is provided only inside the nozzle groove, the configuration in which the wiring connection is made at the nozzle opening affects the ink discharge. It is desirable to avoid connections.

FIG. 7 shows an embodiment in which a connection hole 21 penetrating the lower surface is formed in the middle of the nozzle groove 2 in the recording cell 1 and the wiring 8 is connected to the discharge electrode 5 through the connection hole 21. I have. In this way, it is possible to realize wiring connection that does not hinder the flow of ink.

As another embodiment, as shown in FIG. 8, a connecting portion 22 is formed by extending the tip of the discharge electrode 5 and extending to the lower surface of the recording cell 1, and a wiring connection is made at this portion. It can be suggested to do so. According to such an embodiment, it is not necessary to make a hole in the recording cell 1, and the connection portion (extended portion) may be formed in the electrode forming step. The connection of the wiring 8 to the wiring connecting portion 22 is as follows.
The opposite side is preferable, not the side of the nozzle opening 4 where the ink is ejected. In this way, it can be used without problems even in an embodiment in which recording cells are stacked in multiple stages.

As still another embodiment, a form in which one recording cell is constituted by combining a plurality of divided members can be proposed. The embodiment shown in FIG. 9 has a configuration in which a cell 23 in which the nozzle groove 2 and the ejection electrode 5 are formed and a cell 24 in which the ink tank groove 3 is formed are joined to form one recording cell. In this embodiment, a wiring 23 is connected in advance to a cell 23 having an ejection electrode 5 and a cell 24 having an ink tank 3 which does not require an electrode is integrated to constitute one recording cell. It is. The cell 24 having no electrode can be completed only by machining, the discharge electrode 5 and the cell 23 for wiring can be formed by simple machining, and the wiring operation can be facilitated. In this embodiment, an auxiliary cell (not shown) having a nozzle groove without an electrode is interposed between the cell 23 having the ejection electrode 5 and the cell 24 having the ink tank 3 to reduce the influence between the electrodes. It can be deformed as follows.

The embodiment shown in FIG.
And the nozzle groove 2 are provided in one recording cell 1, an embodiment in which an ink tank 25 is formed on a lid 26 as shown in FIG. 10 can be proposed. A nozzle groove 2 and a discharge electrode 5 are formed in the recording cell 1, an ink tank groove 25 is formed on a surface of the lid 26 facing the inner part of the nozzle groove 2, and these are joined to form an ink tank 25 and a nozzle. Make up the hole.

In this way, the processing surface of the nozzle groove 2 and the processing surface of the ink tank 25 can be made different, so that a processing method suitable for each can be adopted. For example, since the depth of the ink groove 2 and the depth of the ink tank groove 25 are often different, different processing is required. In a plurality of types of groove processing, it is easier to perform each processing operation from an unprocessed surface. The recording cell 1 provided with the nozzle groove 2 may be provided with the ejection electrode 5 after the formation of the nozzle groove 2, and the processing is extremely easy.

In the recording head constructed as described above, since the nozzle openings 4 for discharging ink are formed in a hole shape, the meniscus is formed by projecting the ink to make it easier to fly the ink. It takes time and the applied voltage is high. If the meniscus can be formed efficiently, the applied voltage can be further reduced.

To form a meniscus by mechanically projecting ink from the nozzle openings, protrusions 2 are formed on the upper and lower sides of each nozzle opening 4 as shown in FIG.
7 and 28, and an embodiment in which a meniscus is formed between the two by utilizing the surface tension of ink can be proposed. The protrusion 27 is formed so as to protrude in a triangular shape in the ink discharge direction in opposition to the nozzle groove on the end face of the lid 10. It is formed so as to project in a triangular shape. The protrusions 27 and 28 are effective even if only one of them is used.

FIG. 12 shows another embodiment for forming a meniscus. In this embodiment, the recording cells 1 in which the nozzle openings 4 are formed and the end surfaces 29 and 30 of the lid 10 are curved to facilitate the formation of a meniscus. This embodiment is easy to process.

The method of forming a meniscus as described above is as follows.
In order to prevent ink from flowing out at the nozzle opening, the portion must have ink-phobic properties. Otherwise, there will be disadvantages such as that ink is connected between the nozzle openings and individual printing cannot be performed, or ink escapes and a meniscus cannot be formed.

As another embodiment for forming a meniscus, as shown in FIG. 13, a mandrel 31 such as a needle-shaped wire or fiber is provided at the center of the nozzle groove 2 and a meniscus is formed at the center of the nozzle opening 4. It is possible to propose a configuration to be performed. In this embodiment, since the center of the meniscus is the tip of the protruding mandrel 31, the ink can fly stably.

As another embodiment of the meniscus formation, as shown in FIG.
By inserting 2, it is possible to propose a form in which the tip position of the meniscus is further stabilized. This U-shaped line 32 can keep its tip position stable with respect to the nozzle opening 4.

Next, an embodiment for electrically forming a meniscus will be described. In an electrostatic induction type inkjet recording apparatus, ink is moved by electrostatic force. Therefore,
By applying an electric field from the ink tank to the ejection electrode, a meniscus of ink can be formed at the nozzle opening.

FIG. 15 shows an embodiment in which the ink in the nozzle groove 2 is moved toward the nozzle opening 4 by an electric field formed by the discharge electrode 5 in the nozzle groove 2 and the auxiliary electrode 33 in the ink tank 3. Auxiliary electrode 33 in ink tank 3
And the discharge electrode 5 are formed separately.
Are connected to a bias power supply 36. The ejection electrode 5 is connected to the wiring 8 using a connection portion 34 extending from the nozzle opening 4 to the end face of the recording cell. Then, a potential difference is applied between the ejection electrode 5 and the auxiliary electrode 33 to form an electric field, and ink is moved by electrostatic force to form a meniscus in the nozzle opening 4.

In this embodiment, the power supplies 7 and 36 may be integrally configured as one power supply. However, in this case, two electric potentials are required in addition to the ground potential. Therefore, a power supply capable of supplying an electric potential according to the two electric potentials is required.

The ink in the ink tank 3 is supplied to the nozzle opening 4
In order to make the ink flow easier, a method of pressurizing the inside of the ink tank with a pressurizing pump (not shown) can be adopted.

In a recording head that does not use an external ink tank, when the ink in the ink tank formed in the recording cell is consumed, the pressure in the ink tank drops and it becomes difficult to discharge from the nozzle opening. Therefore, it is desirable to provide a ventilation hole for breathing so that the pressure in the ink tank does not decrease with consumption of ink.

The embodiment shown in FIG.
This is a mode in which a ventilation hole formed by the ventilation hole groove 39 is formed in the joint surface between the lid 38 and the recording cell 1 by superimposing the lid 38 formed thereon. Other configurations are the same as those of the embodiment shown in FIG.

In the embodiment shown in FIG. 17, a part of the ink tank groove wall is cut off to form a ventilation hole groove 40 in the lid 26 in which the ink tank groove 25 is formed. This is a mode in which a ventilation hole is formed. Other configurations are the same as those of the embodiment shown in FIG.

In order to extend the life of a recording head having no external ink tank, the capacity of the ink tank must be increased. In order to increase the ink tank capacity of the recording head, it is effective to form a large ink tank groove in the lid.

In the embodiment shown in FIG. 18, a large ink tank is formed by combining the ink tank groove 3 formed in the recording cell 1 and the large ink tank groove 42 formed in the lid 41. The lid 41 is formed as a lid provided with an ink tank having a ventilation hole by combining a base 43 and an auxiliary body 45 having a ventilation hole groove 44.

In the embodiment shown in FIG. 19, two rows of nozzle holes are formed by multi-layered recording cells 1 and 46, and the capacity of the ink tank is increased.
The upper recording cell 46 has a through hole 47 for communicating the ink tank 3a of the lower recording cell 1 with the ink tank 3b of the upper recording cell 46. And the lid 41 is
The configuration is the same as that of the embodiment shown in FIG. According to such an embodiment, the ink tank 3 of the lower recording cell 1
The ink can be supplied from the large ink tank 3b of the upper recording cell 46 even if the capacity is small. Also,
The upper ink tank 3b breathes through the ventilation hole 44.

Since the ink is a mixture of a solvent and a coloring material (pigment), if the ink stays in the recording head, there is a problem that the coloring material settles down and is fixed. Further, there is a problem that the portion exposed to the nozzle opening 4 for a long time is dried and solidified.

In the embodiment shown in FIG. 20, the ink in the ink tank is supplied to the external ink tank 14 by a supply pipe 15 connected to one side of the ink tank, a recovery pipe 48 connected to the other side, and a pump 49. This is a configuration in which the coloring material is refluxed to prevent the coloring material from settling and fixing due to the ink remaining in the ink tank.

The embodiment shown in FIG. 21 is configured to prevent ink from staying in the nozzle groove (nozzle hole) 2. An ink recovery groove 50 continuous with the nozzle groove 2 is formed up to the lower surface of the nozzle opening end surface of the recording cell 1, and ink in the nozzle opening flows down along the ink recovery groove 50.
An ink collecting cell 52 having an ink collecting hole groove 51 formed on the lower surface of the recording cell 1 so as to coincide with the ink collecting groove 50 is joined to form an ink collecting hole on the joining surface. The ink flowing down is drawn into the ink collecting hole, and is returned from the collecting pipe 53 to the external ink tank 14 via the pump 54.

The electrostatic induction type ink jet recording apparatus using the above-described recording head can also use a recording head constituted by arbitrarily combining the features in each embodiment. For example, a multi-color recording head can be formed by laminating single-color recording heads in which nozzle positions are arranged in a grid pattern.

[0080]

According to the recording head of the present invention, since the ejection electrode is provided on the nozzle groove wall for guiding the ink, no misalignment occurs between the nozzle groove and the ejection electrode when the recording cell and the lid are joined, so that the recording head is stable. This makes it possible to create a nozzle hole having a predetermined shape, apply an appropriate voltage to the ink, and discharge and fly the ink accurately.

Further, a plurality of rows of nozzle holes can be formed by stacking recording cells of the same shape in multiple stages.
The degree of integration of the ink nozzles can be increased.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a recording head showing one embodiment of the present invention.

FIG. 2 shows another embodiment of the present invention, and is an exploded perspective view of a recording head in which two recording cells are overlapped to form two rows of nozzle holes.

FIG. 3 is an exploded perspective view of a recording head according to still another embodiment of the present invention, in which three recording cells are overlapped to form two rows of nozzle holes.

FIG. 4 is an exploded perspective view of a recording head provided with an external ink tank according to still another embodiment of the present invention.

FIG. 5 is a view showing still another embodiment of the present invention, and is a view for explaining a method of insulating an electrode in and near an ink tank.

FIG. 6 is a view showing still another embodiment of the present invention, and is a view for explaining a peeling processing method for forming an ejection electrode by removing an electrode in and near an ink tank.

FIG. 7 is an exploded perspective view of a recording head showing still another embodiment of the present invention and showing a modification of wiring connection to ejection electrodes.

FIG. 8 shows still another embodiment of the present invention, and is a longitudinal sectional side view of a recording head showing a modification of wiring connection to an ejection electrode.

FIG. 9 shows still another embodiment of the present invention, and is an exploded perspective view of a recording head in which a recording cell is composed of a plurality of members.

FIG. 10 shows still another embodiment of the present invention, and is an exploded perspective view of a recording head having an ink tank formed on a lid.

FIG. 11 shows still another embodiment of the present invention and is an exploded perspective view of a recording head in which a projection is formed in a nozzle opening for forming a meniscus.

FIG. 12 shows still another embodiment of the present invention, and is an exploded perspective view of a recording head in which a nozzle opening end surface is formed into a curved surface for forming a meniscus.

FIG. 13 shows still another embodiment of the present invention, and is a perspective view of a recording cell in which a mandrel is provided in a nozzle groove for forming a meniscus.

FIG. 14 shows still another embodiment of the present invention, and is a perspective view of a recording cell in which a U-shaped member is provided at the tip of a nozzle groove for forming a meniscus.

FIG. 15 shows still another embodiment of the present invention, and is a perspective view of a recording cell provided with an auxiliary electrode for forming a meniscus.

FIG. 16 is a longitudinal sectional side view of a recording head according to still another embodiment of the present invention, in which a vent hole for breathing is formed in an ink tank.

FIG. 17 shows still another embodiment of the present invention, and is an exploded perspective view of a recording head having a ventilation hole formed in an ink tank.

FIG. 18 shows still another embodiment of the present invention, and is a longitudinal sectional side view of a recording head in which a large ink tank and a ventilation hole for breathing are formed.

FIG. 19 shows still another embodiment of the present invention, and is a longitudinal sectional side view of a multilayer recording head in which a large ink tank and a ventilation hole for breathing are formed.

FIG. 20 is a perspective view of a recording head according to still another embodiment of the present invention, which prevents settling of a coloring material due to retention of ink.

FIG. 21 is a perspective view of a recording head according to still another embodiment of the present invention, which prevents settling of a coloring material due to stagnation of ink.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording cell, 2 ... Nozzle groove, 3 ... Ink tank (ink tank groove), 4 ... Nozzle opening, 5 ... Discharge electrode, 6 ... Wiring connection part, 7 ... Recording signal voltage generation power supply.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshinobu Fukano 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Akira Shimada 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Inside the Hitachi Research Laboratory, Hitachi, Ltd.

Claims (17)

[Claims] A recording head of an electrostatic induction type ink jet recording apparatus in which ink in a nozzle hole of a recording head is ejected by an electrostatic force to fly and adhere to a recording medium, wherein a plurality of nozzle grooves are formed in an insulating plate. An ink jet recording apparatus comprising: a recording cell having an ejection electrode provided on a wall surface of a nozzle groove; and an insulating plate lid for forming a plurality of nozzle holes by overlapping the recording cell and covering the nozzle groove. Recording head. 2. A recording head according to claim 1, wherein said recording cell includes an ink tank connected to a plurality of nozzle grooves. 3. A recording head for an ink jet recording apparatus according to claim 1, wherein said lid is provided with an ink tank connected to said nozzle groove in a joined state on a surface joined to said recording cell. 4. The recording head according to claim 1, further comprising an external ink tank for supplying ink to a plurality of nozzle grooves provided in said recording cell. 5. A recording head for an ink jet recording apparatus according to claim 1, wherein said discharge electrode is provided on a surface of at least half of a nozzle groove. 6. A recording head according to claim 5, wherein said discharge electrode is provided on an entire surface of a nozzle groove. 7. A recording head for an ink jet recording apparatus according to claim 1, wherein an electrode is provided on a surface of said lid facing said nozzle groove. 8. A recording head for an ink jet recording apparatus according to claim 1, wherein the discharge electrodes located in and near the ink tank are covered with an insulating member. 9. A recording head for an ink jet recording apparatus according to claim 1, wherein the discharge electrode is not located in the ink tank and in the vicinity of the ink tank. 10. A recording head for an ink jet recording apparatus according to claim 1, wherein said discharge electrode is provided so as to extend from a tip portion of the nozzle groove to a back surface of the recording cell. 11. A recording head for an ink jet recording apparatus according to claim 1, wherein said lid is an insulating plate having no discharge electrode. 12. An ink jet recording apparatus according to claim 1, wherein a protrusion protruding from a recording cell and / or a lid is provided in a tip end opening of the nozzle hole in an ink discharging direction. Recording head. 13. A recording head for an ink jet recording apparatus according to claim 1, wherein an auxiliary electrode for applying electrostatic force to the ink is provided at a position deeper than said discharge electrode. 14. A recording head for an ink jet recording apparatus according to claim 1, wherein a plurality of recording cells are stacked to form a plurality of rows of nozzle holes. 15. A recording head according to claim 14, wherein ink tanks of adjacent recording cells are communicated with each other. 16. A plurality of nozzle grooves, one end of which extends so as to penetrate an edge of the insulating plate and the other end of which extends to connect to an ink tank. A recording cell provided with a discharge electrode for applying a voltage is formed, and a cover of an insulating plate is joined to the recording cell to cover the nozzle groove, thereby forming a plurality of nozzle holes for guiding and discharging ink between the two. A method for manufacturing a recording head of an ink jet recording apparatus, comprising: forming a recording head; 17. The discharge electrode according to claim 16, wherein:
An ink-jet printing method comprising: forming a conductive film uniformly on the nozzle groove forming surface of an insulating plate having the nozzle grooves formed thereon by metal vapor deposition, sputtering, or the like, and removing the conductive film between the nozzle grooves; A method for manufacturing a recording head of a recording apparatus.