JPH068450A - Manufacture of ink jet head - Google Patents

Abstract

PURPOSE:To solve dispersion in discharge performance among nozzles by simplifying a process by a method wherein an electrode on a bottom face of a passage is removed by a cutting means. CONSTITUTION:In an ink jet head wherein an ink passage 4 and a nozzle face which is arranged in contact with the ink passage to discharge ink are provided, and a part or the whole of the ink passage 4 is composed of a piezoelectric material, an electrode 10 formed on a bottom face 12 of the passage is removed by a cutting means 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head. More specifically, the present invention relates to an inkjet head that selectively deposits ink droplets on a recording medium.

[0002]

2. Description of the Related Art In recent years, ink jet printers have been rapidly developed due to advantages such as high speed printing, low noise and high printing quality. Several methods have been proposed for an inkjet head used in an inkjet printer, but generally they can be classified into two methods. That is, the first method uses a piezoelectric material to generate a pressure pulse in the ink chamber to eject an ink droplet from the nozzle. The second method uses a heating resistor to generate vapor bubbles in the ink chamber and eject ink droplets from the nozzle.

The second method has a problem in that the heating resistor is easily deteriorated and durability is poor because the heating resistor is repeatedly heated and cooled rapidly. There is also a problem that only ink that generates vapor bubbles can be used.

On the other hand, the first method does not have the above-mentioned problems. However, in the first method, the efficiency of the piezoelectric material is low, so that the inkjet head itself becomes large. In addition, the manufacturing process is complicated, it is not suitable for mass production, and as a result, it is expensive. Further, since it is difficult to increase the nozzle density, it is difficult to obtain high print quality. Due to these issues, it has not been widely spread.

As a first method for solving the problem of the method, Japanese Patent Laid-Open No. 63-247501 has a plurality of parallel rectangular cross-sectional flow passages spaced from each other in the nozzle arrangement direction, An electrode is formed on a part or the whole surface of the side wall of the channel, the part or the whole of the side wall is made of a piezoelectric material, and the side wall is deformed parallel to the direction in which the channels are arranged. An inkjet head has been proposed that changes the internal pressure to eject ink droplets formed at one end of a flow path.

The structure of the ink jet head disclosed in Japanese Patent Laid-Open No. 63-247501 will be described with reference to FIG. FIG. 3 is a diagram showing the configuration of the inkjet head.
Is a piezoelectric substrate, 2 is a nozzle plate, 3 is a nozzle, 4 is an ink flow path, 5 is a side wall made of a piezoelectric material (hereinafter abbreviated as a piezoelectric side wall), 6 is an upper substrate, 7 is an ink supply port, and 9 is ink discharge. The outlet 10 is an electrode.

In this ink jet head, a large number of parallel flow paths 4 are formed. It is connected to the nozzle 3 formed on the nozzle plate 2, and the other end of the flow path 4 is connected to the slit-shaped ink ejection port 9. In addition, the ink flow path 4
Is covered with an upper substrate having an ink supply port 7, and is connected to an ink storage tank (not shown) via the ink supply port corresponding to each ink flow path 4. The ink flow path 4 is composed of a piezoelectric side wall 5 and an upper substrate 6, and has a rectangular cross section.

The ink ejection operation of the conventional ink jet head will be described with reference to FIG. 4 showing a cross section of the flow path. In FIG. 4A, the piezoelectric side wall 5 has a different polarization direction 11.
It is formed by individual piezoelectric sidewalls. In FIG. 4A, the piezoelectric side wall 5 is not deformed because a voltage pulse is not applied to the electrodes 10 formed on both sides by an electric actuating means (not shown).

In FIG. 4B, when a voltage pulse is applied, the piezoelectric side wall 5 is deformed to the joint surface of the piezoelectric side wall, and a part of the ink filling the ink flow path 4 is generated by the generated pressure.
Ink droplets are ejected from the nozzle openings 3 shown in FIG. 3, and the other part is ejected to the ink storage tank side through the ink supply port 7. The ink supply to the nozzle portion after the ink droplets are discharged is supplied to the nozzle 3 from the ink storage tank through the ink supply port 7 and the ink flow path 4 by the capillary force of the nozzle 3.

In the conventional example, another structure has been proposed for the piezoelectric side wall. Hereinafter, the structure described above will be referred to as a piezoelectric side wall structure A, and the structure described below will be referred to as a piezoelectric side wall structure B.

The structure of the piezoelectric side wall structure B will be described with reference to FIG. In this piezoelectric side wall structure B, the piezoelectric side wall 5 that partitions each ink flow path 4 is polarized in a direction 11 perpendicular to the flow path direction. FIG. 5A is a diagram showing a state in which no voltage pulse is applied, and FIG. 5B is a diagram showing a state in which a voltage pulse is applied.

In FIG. 5A, the piezoelectric side wall 5 is not deformed because no voltage pulse is applied to the electrodes 10 formed on both sides by an electric actuating means (not shown). In FIG. 5B, when a voltage pulse is applied, the upper portion of the piezoelectric side wall 5 is deformed in the displacement direction, and a part of the ink that fills the ink flow path 4 is ejected as an ink droplet from the nozzle 3 by the generated pressure. Let

Furthermore, by forming an insulating layer (not shown) on the electrode 10 in both the piezoelectric side wall structures A and B, it is possible to eject ink having a high electric conductivity without damaging the electrode.

A conventional method of manufacturing an ink jet head will be described below with reference to FIG.

A piezoelectric substrate having a thickness of 1 mm and a thickness of 0.2 m
Piezoelectric ceramic plates of m are bonded in the opposite polarization direction to form the piezoelectric substrate 1.

The piezoelectric side wall 5 having a groove width of 80 μm is formed on the piezoelectric substrate 1 with a diamond blade.

The electrode 1 is formed on the piezoelectric side wall 5 by a vacuum deposition method.
Form 0. The electrode 10 is Ni-Cr 1.0 μm, Au
0.5 μm is formed.

In the case of the piezoelectric sidewall structure A, the plane of the piezoelectric substrate 1 is perpendicular to the vapor deposition source, whereas in the case of the piezoelectric sidewall structure B, the piezoelectric substrate 1 is oriented in the direction of the vapor deposition source 14 as shown in FIG.
Tilt with respect to each other, and perform vapor deposition operations on both side surfaces once. In the piezoelectric wall structure B, the piezoelectric substrate 1 is made of one piece of piezoelectric ceramics.

The unnecessary electrode 10 on the upper surface of the piezoelectric substrate 1 is removed by plane polishing.

The state in which the above steps up to electrode formation are completed is shown in FIG. 6 (a).

An adhesive is applied to the upper portion of the piezoelectric side wall 5 to bond the piezoelectric substrate 1, the upper substrate 6 and the ink supply port 7. The upper substrate 6 serves as the top wall of the ink flow path 4. It is desirable that the adhesive used has a small amount of runoff.

An adhesive is applied to the end faces of the piezoelectric substrate 1 and the upper substrate 6 on the ink ejection side to bond the nozzle plate 2. Also in this case, it is desirable that the adhesive used has a small amount of outflow.

The state in which the above steps up to the adhesion of the nozzle plate 2 are completed is shown in FIG. 6 (b).

It is connected to the ink supply means and the drive means.

The operation as an ink jet head is possible through the above steps.

[0026]

However, in the conventional ink jet head having the piezoelectric structure A, the electrodes are formed even on the bottom surface, and the electric field wraps around the bottom surface of the substrate, which has an effect on ink droplet ejection. .

FIG. 8 is a sectional view of an ink flow path of a conventional piezoelectric structure A ink jet head. In order to eject the ink filled in the ink flow path 4 as an ink droplet,
A voltage is applied to the electrode 10. Then, the electric field curve 15 is shown in FIG.
Occurs in the piezoelectric substrate 1 and the piezoelectric sidewall 5 is deformed as shown by the dotted line 16. However, as shown in FIG. 8, the electric field curve 15 is also generated on the electrode on the bottom surface 12 of the ink flow path, and the bottom surface of the substrate becomes wavy as shown by the dotted line 17. For this reason, the adjacent side walls of the cavity are affected, causing crosstalk, and it is difficult to discharge at a constant level for each nozzle.

Conventionally, a vacuum deposition method has been studied for the purpose of not forming an electrode on the bottom surface. As shown in FIG. 9, in the vacuum evaporation method, it was considered that the piezoelectric substrate 1 was tilted with respect to the evaporation source direction 14. However, in order to form the electrodes on both wall surfaces of the ink flow path 4, it is necessary to perform the vapor deposition operation twice, and further the substrate angle must be changed by removing the substrate from the vacuum chamber. In addition, since it is necessary to return the inside of the vacuum chamber to atmospheric pressure once again and to make the inside of the chamber vacuum state again, man-hours are required in the process, and the scale of the apparatus configuration becomes large to perform the above evaluation in the vacuum chamber. It becomes expensive. Further, as a result, it was difficult to form no electrode on the bottom surface.

In the structure of the piezoelectric side wall B in which the electrode is formed by the same method as described above, the electrode is formed on the upper half of the piezoelectric side wall. Since there is no electrode on the bottom surface, there is no interference between cavities, but since the electrode area is small, the volume of the piezoelectric element that can be displaced is small, and a higher voltage is required to obtain the ink droplet ejection speed necessary for image formation. The problem is that the power consumption increases.

Further, conventionally, electrodes have been formed by using a vacuum evaporation method. However, when the metal layer is formed by the dry process, a metal lump having a diameter of about 1 μm is formed on the surface. This is due to the formation process of the metal thin film in the dry process.

When the metal atoms reach the surface of the substrate, they undergo surface movement on the substrate and aggregate to form nuclei. The formed nuclei grow three-dimensionally due to the agglomeration of the incoming metal atoms. A metal thin film is formed through such a growth process. Therefore, island-shaped clusters exist on the entire surface of the metal thin film.

Furthermore, the piezoelectric ceramics, which is the substrate, is formed of agglomerates having a diameter of 2 to 3 μm.
The shadow part is produced. Since the flying metal atoms do not reach the shadow directly, a difference appears in the amount of metal atoms.

Due to the above two points, the surface roughness of the electrode reaches a maximum of about 5 μm. Further, when a wet process such as electroless plating is used, the surface of the formed electrode is rougher than that in the dry process because the surface is roughened in order to improve the adhesion of the metal layer.

If the wall surface of the flow path is not smooth, the resistance of the flow path becomes large, and there arises a problem that bubbles existing in the cavity are difficult to escape. The presence of air bubbles in the cavity makes it impossible to efficiently convert the displacement of the piezoelectric ceramics into the ink droplet ejection pressure, causing ejection failure.

Further, due to the presence of irregularities on the surface of the electrode, many defects were present when performing a treatment such as an insulation treatment, and complete coating was difficult. For example, in the case of performing the insulation treatment, when a highly conductive water-based ink was used, discharge was impossible due to the leakage of current into the ink. Even with a small amount of current leakage that does not hinder ink droplet ejection, ejection failure was caused due to electrode corrosion and ink deterioration after long-term use.

The present invention solves such a problem and provides an ink jet head having a wide range of ink types, a good production yield, a constant ink ejection performance level for each nozzle, and long-term reliability. The purpose is to

[0037]

In order to solve such a problem, the ink jet head of the present invention has a flow path and a nozzle surface for ejecting ink disposed in the flow path, and the flow path has In an inkjet head whose part or whole is made of a piezoelectric material, a cutting means is used to remove the electrode formed on the bottom surface of the flow path, and the electrode surface formed on the side wall of the flow path is smoothed. For this purpose, a cutting means is used to remove the electrodes formed on the bottom surface of the flow channel and to smooth the electrode surface formed on the side wall of the flow channel in the same step.

[0038]

The present invention will be described below with reference to the drawings. The present invention is not limited to the examples below.

First, an example of a method for manufacturing an ink jet head of the present invention will be shown in FIG. 1 and described. FIG. 1 is a sectional view of an ink flow path in an inkjet head manufacturing process showing an embodiment of the present invention. Reference numeral 1 is a piezoelectric substrate, 4 is an ink flow path, 5 is a piezoelectric side wall, 8 is a diamond blade, 10 is an electrode, 11 is a polarization direction of the piezoelectric side wall, and 12 is an ink flow path bottom surface.

Piezoelectric side walls 5 having a groove width of 80 μm are formed on the piezoelectric substrate 1 bonded in the opposing polarization directions 11 with a diamond blade having a thickness of 70 μm.

Next, the electrode 10 is formed on the piezoelectric substrate. For the electrode 10, a metal thin film forming means such as vacuum deposition, sputtering or plating is used.

The 80 μm-thick ink channel thus formed is cut deeper than the initially formed groove depth with a diamond blade having a thickness of 65 μm to remove the electrode at the bottom of the channel. At this time, the electrode surface is polished by simultaneously spraying small-diameter abrasive grains.

The bottom electrode can be removed by one-time cutting, but it can also be removed by cutting with a thin diamond blade a plurality of times.

The surface of the obtained electrode was extremely flat, and the surface irregularities could be 0.5 μm or less.

By removing the electrode on the bottom surface, the waviness of the substrate as shown in FIG. 8 can be eliminated, and stable ejection can be performed regardless of the behavior of the adjacent cavity. In addition, comparing with the conventional method using oblique deposition,
The process was greatly simplified. Further, since the bottom surface of the ink flow path was polished by the abrasive grains and became smooth, it was effective in reducing the flow path resistance.

Further, since the surface of the electrode was polished, the flow path resistance could be reduced. Further, when the insulating layer was formed on the electrode, no defect was generated in the insulating layer, and stable insulating properties could be obtained easily and for a long time.

By using the above method, a plurality of effects can be obtained in the same step, and the steps can be simplified.

Further, as shown in FIG. 2, a buffing cylinder having a long bristles is brought into close contact with the upper surface of the substrate, and the above-mentioned discharged particles having a smaller particle diameter are sprayed and rotated. As a result, the electrode surface becomes smoother and the unevenness of the electrode surface is 0.1 μm
Will be less than.

In the case of performing the insulation treatment, since the electrode surface is made smoother, the insulation treatment can be performed with a thinner film thickness.

By the ink jet manufacturing method of the present invention,
It has stable insulation and long-term reliability for conductive ink. The manufacturing yield, which was about 60% in the conventional method, was almost 100% satisfied, and manufacturing defects due to current leakage could be eliminated.

Further, it was possible to suppress the variation in the ejection speed of ink droplets from nozzle to nozzle, which was about 10% in the past, to about 3%.

Further, regarding the polishing of the electrode surface, it was also useful for the ink jet head having the ink flow path cross-sectional structure of FIG. 5 constituted by the piezoelectric side wall structure B, and the same effect as above could be obtained.

The present invention is also useful for an inkjet head having a structure in which electrodes are exposed in other ink flow paths.

[0054]

According to the ink jet manufacturing method of the present invention, it has a good manufacturing yield, a constant ink ejection performance level for each nozzle, excellent mass productivity, and a wide range of ink type compatibility, and can be used for a long period of time. It has an excellent effect that an ink jet head with high reliability can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of an ink flow path showing a method for manufacturing an inkjet head according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an inkjet head manufacturing method according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration of a conventional inkjet head.

FIG. 4 is a cross-sectional view of an ink flow path showing the ejection principle of an inkjet head having a conventional piezoelectric sidewall structure A.

FIG. 5 is a cross-sectional view of an ink flow path showing the ejection principle of an inkjet head having a conventional piezoelectric sidewall structure B.

FIG. 6 is a perspective view showing a conventional method for manufacturing an inkjet head.

FIG. 7 is a sectional view of an ink flow path showing a method of forming electrodes of an inkjet head having a conventional piezoelectric sidewall structure B.

FIG. 8 is a cross-sectional view of an ink flow path showing a method for forming electrodes of an inkjet head having a conventional piezoelectric sidewall structure A.

FIG. 9 is a diagram showing deformation of a cross section of an ink flow path when a conventional inkjet head is driven.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Nozzle plate 3 Nozzle 4 Ink flow path 5 Piezoelectric side wall 6 Upper substrate 7 Ink supply port 8 Diamond blade 9 Ink discharge port 10 Electrode 11 Polarization direction of piezoelectric side wall 12 Ink flow path bottom surface 13 Buff polishing cylinder 14 Deposition source Direction 15 Electric field curve in piezoelectric substrate 16 Line showing deformation of piezoelectric side wall when driving piezoelectric substrate 17 Line showing deformation of piezoelectric substrate when driving piezoelectric side wall

Claims (3)

[Claims] 1. An ink jet head having a flow path and a nozzle surface disposed in the flow path for ejecting ink, wherein the flow path is partly or entirely made of a piezoelectric material. An inkjet head manufacturing method, characterized in that an electrode formed on a road bottom is removed by a cutting means. 2. An ink jet head having a flow path and a nozzle surface disposed in the flow path for ejecting ink, the flow path being partly or wholly made of a piezoelectric material. An inkjet head manufacturing method, characterized in that an electrode surface formed on a road side wall is polished. 3. An ink jet head having a flow path and a nozzle surface, which is disposed in contact with the flow path, for ejecting ink, and the flow path is partly or wholly made of a piezoelectric material. An inkjet head manufacturing method, characterized in that the removal of the electrode formed on the bottom surface of the road and the polishing of the surface of the electrode formed on the side wall of the flow path are performed in the same step.