JPH06155738A - Ink jet head and its manufacture - Google Patents

Abstract

PURPOSE:To provide an ink jet head of improved foam discharge properties and insulation reliability, simplified process and low unit cost thereof. CONSTITUTION:In an ink jet head provided with an ink passage 4 and a nozzle opening 3 injecting ink fed in the ink passage 4, a part or the whole of the ink passage 4 is constituted of a piezoelectric material and the whole of the surface of ink passage 4 on which an electrode 10 is formed is coated with an insulated layer 12.

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 density of the nozzle array, it is difficult to obtain high print quality. Due to these issues, it has not been widely spread.

As a method for solving the problem of the first method,
In Japanese Patent Laid-Open No. 63-247501, there are provided a plurality of parallel rectangular cross-sectional areas spaced apart from each other in the nozzle arrangement direction, and electrodes are formed on part or all of the side walls of the flow paths. The side wall is partially or entirely made of a piezoelectric material, and the side wall is deformed in parallel to the direction in which the flow channels are arranged, and the pressure in the flow channel is changed so that ink droplets are applied to one end of the flow channel. An inkjet head that can be formed and ejected has been proposed.

The structure of a conventional ink jet head will be described with reference to FIGS. FIG. 5 is a perspective view showing the structure of a conventional inkjet head, and FIG. 6 is a sectional view of an ink flow path showing the structure of the conventional inkjet head. 1
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. An outlet, 10 is an electrode, 11 is a polarization direction, 15 is a channel end opening, 16 is a mounting portion electrode, and 20 is an upper substrate bonding surface.

In this ink jet head, a large number of ink flow paths 4 which are parallel to each other are formed. The ink flow path 4 is
Comprised of a groove formed in the piezoelectric substrate 1 and the upper substrate 6,
Its cross-sectional shape is rectangular. One end of the ink flow path 4 is
It is connected to the slit-shaped ink discharge port 9 and connected to the nozzle 3 formed on the nozzle plate 2. Further, the other end of the ink flow path 4 is connected to the ink supply port 7, and passes through the flow path end opening 15 and the ink supply port 7 corresponding to each ink flow path 4 to an ink storage tank (not shown). Connected.

The ink ejection operation of the conventional ink jet head will be described with reference to FIG. In FIG. 6A, the piezoelectric side wall 5 is formed of two piezoelectric ceramics having different polarization directions 11. In FIG. 6A, 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 driving means (not shown). In FIG. 6B, when a voltage pulse is applied, the piezoelectric side wall 5 is deformed to the reversal plane of the polarization direction of the piezoelectric side wall, and the ink is generated by the pressure generated by the decrease of the volume of the ink flow path 4. A part of the ink filling the flow path 4 is ejected from the nozzle 3 as an ink droplet, 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 flow path 4 by the capillary force of the nozzle 3.

In the above structure, when the upper substrate and the piezoelectric substrate are bonded together, the bonding surface must be sufficiently flat in order to obtain a flow path without ink leakage between the ink flow paths. Further, as shown in the ejection principle of FIG.
Serves as a fulcrum of displacement of the piezoelectric sidewall 5. In order to suppress the loss of displacement of the piezoelectric side wall 5 as much as possible and to print with low power, it is desirable that the bonding layer be as thin as possible.

Further, in the above structure, the electrodes are exposed on the surface of the ink flow path and are in direct contact with the ink. For this reason, when water-based ink or the like with high conductivity is used, current leaks in the ink due to voltage application during ejection,
Corrosion of electrodes, deterioration of ink, etc. occur.

Therefore, although the ink having a low electric conductivity, for example, the oil-based ink is used, the oil-based ink has a larger print bleeding than the water-based ink, and the nozzle is easily clogged. Sufficient print quality cannot be obtained. It also has drawbacks such as being harmful and dangerous.

In order to solve the above problem, it has been proposed in the prior art to form an insulating layer on the electrode.

A method of manufacturing a flow path portion of a conventional ink jet head will be described below with reference to FIG. 7, and a structure of the conventional ink jet head will be described with reference to FIGS. FIG. 7, FIG. 8 and FIG. 9 are cross-sectional views of ink flow paths of a conventional inkjet head. In the figure, 1 is a piezoelectric substrate, 4 is an ink flow path,
Reference numeral 5 is a piezoelectric side wall, 6 is an upper substrate, 10 is an electrode, 11 is a polarization direction, 20 is an upper substrate bonding surface, 21 is an insulating layer, a missing electrode, 22 is an insulating layer, and peeling of the electrode.

As shown in FIG. 7A, the ink flow path 4
An electrode 10 is formed on the piezoelectric substrate 1 on which the electrodes have been formed.

Further, as shown in FIG. 7B, the electrode 1
0, the insulating layer 12 is formed.

Unnecessary electrodes and insulating layers formed on the adhesive surface 20 of the piezoelectric substrate 1 are collectively removed by plane polishing to form a flat adhesive surface 20.

The upper substrate 6 was adhered to obtain the structure shown in FIG.

[0017]

However, the following problems have occurred in the structure and manufacturing process of the conventional ink jet head.

FIG. 8 is a sectional view of an ink flow path of a conventional ink jet head. In many cases, the piezoelectric side wall of the piezoelectric side wall 5, the insulating layer, the missing electrode 21, and the peeling 22 of the insulating layer and the electrode are caused by polishing. When a highly conductive water-based ink was used, the nozzle in which this phenomenon occurred was unable to eject due to the leakage of current into the ink. In addition, even a small amount of current leakage that does not hinder the ejection of ink droplets caused ejection failure due to electrode corrosion and ink deterioration due to long-term use, and required driving power also increased. Furthermore, when the adhesive layer between the upper substrate 6 and the piezoelectric substrate 1 is insufficient,
Ink penetrates through the gap, and the same adverse effect occurs. Therefore, if the adhesive layer is thickened in order to obtain sufficient adhesive strength, the rigidity of the adhesive layer is insufficient, resulting in a decrease in efficiency.

Further, as shown in FIG. 9, when the insulating layer is adhered without polishing as a measure against current leakage, the adhering surface is not flat, and ink leakage to adjacent ink channels is confirmed at several places. It was The thickness of the bonding layer, which used to be around 1 μm, is 8
10 μm, and due to insufficient rigidity of the adhesive layer and insulating layer,
The loss with respect to the displacement of the piezoelectric substrate was large, and it was necessary to increase the drive voltage by about 20%.

Another problem is that if the joint between the piezoelectric side wall of the ink flow path and the upper substrate is angled, it becomes a non-uniform element for ink circulation, and bubbles tend to accumulate in the ink flow path. , The air bubble discharging property also deteriorated.

The present invention solves such a problem, has a wide range of ink compatibility, has a good production yield, a simple production process, a constant ink ejection performance level for each nozzle and head, and long-term reliability. It is an object of the present invention to provide at low cost an inkjet head capable of printing with low power consumption.

[0022]

An ink jet head and a method of manufacturing the same according to the present invention have a flow path and a nozzle surface for ejecting ink disposed in the flow path, and a part or the whole of the flow path is provided. In an ink jet head which is made of a piezoelectric material and in which an electrode for driving the piezoelectric material is formed on the surface of the flow path in contact with the ink, the entire surface of the flow path in contact with the ink is covered with an insulator. As a method for coating the surface of the flow path, two or more kinds of gases are introduced into a vacuum chamber, and a reaction excitation means for the gas is used,
A method of forming a coating layer using the gas as a starting material is used.

[0023]

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 the ink jet head of the present invention is shown in FIGS. FIG. 1 is a perspective view of an inkjet head showing an embodiment of the present invention, and FIG. 2 is a sectional view of an ink flow path. Reference numeral 1 is a piezoelectric substrate, 2 is a nozzle plate, 3 is a nozzle hole, 4 is an ink flow path, 5 is a piezoelectric side wall, 10 is an electrode, and 12 is an insulating layer. The ejection operation is similar to that of the conventional inkjet head.

The ink jet head manufacturing method of the present invention will be described below with reference to FIG.

FIG. 3 is a sectional view of an ink flow path showing a method of manufacturing an ink jet head according to 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, 6 is an upper substrate, 10 is an electrode, 12 is an insulating layer, and 20 is an upper substrate bonding surface.

FIG. 3A is a sectional view of the ink flow path after the electrodes are formed. Piezoelectric side walls 5 having a groove width of 80 μm are formed by a dicing saw or the like on the piezoelectric substrates 1 bonded in opposite polarization directions, and the electrodes 10 are formed by vacuum vapor deposition or the like.

The electrode 10 was Ni-Cr 1.0 μm and Au was 0.1 μm.
Form 5 μm. Alternatively, the piezoelectric side wall 5 can be processed using a wire saw or the like.

Next, unnecessary electrodes on the upper surface of the piezoelectric substrate 1 are removed by planar polishing to obtain a flat upper substrate bonding surface 20. The sectional shape of the ink flow path is as shown in FIG.

A glass upper substrate 6 is bonded to the piezoelectric substrate 1 on which the piezoelectric sidewall 5 is formed. It is preferable that the adhesive material does not flow out. The sectional shape of the ink flow path is as shown in FIG.

The insulating layer 12 is formed by a thermal decomposition CVD (chemical vapor deposition) method or the like. At this time, unnecessary portions of the insulating layer are masked to prevent formation of the insulating layer. The cross section of the ink flow path is as shown in FIG.

A nozzle plate is bonded to the end faces of the piezoelectric substrate 1 and the upper substrate 6.

The ink supply means and the drive means for generating the applied pulse are connected.

The ink jet head thus obtained has the structure shown in FIG.

A method of forming an insulating layer by the thermal decomposition CVD method will be described below with reference to FIG.

FIG. 4 shows the structure of the thermal decomposition CVD apparatus. In the figure, 1 is a piezoelectric substrate, 31 is a vaporizer, 32 is a thermal decomposition chamber, and 33 is a vapor deposition chamber.

Chemical formula 1 is diparaxylylene which is a raw material for the insulating layer. Diparaxylylene is a dimeric solid at room temperature. Diparaxylylene is 1 Torr in the vaporization chamber 31.
It is heated at 175 ° C., vaporized, and introduced into the thermal decomposition chamber 32.

The introduced diparaxylylene is heated to 680 ° C. and decompressed to 0.5 Torr in the thermal decomposition chamber 32 to become the diradical paraxylylene shown in Chemical formula 2.

The diradical paraxylylene is at room temperature, 0.
After being introduced into a vapor deposition chamber at 1 Torr, it is adsorbed on the substrate and polymerized to become polyparaxylylene shown in Chemical formula 3, and an organic insulating layer is formed on the entire surface of the substrate.

The substrate on which the organic insulating layer is formed is -70.
The pressure is reduced to 0.001 Torr and the temperature is reduced to 0.001 Torr to obtain an adhered insulating layer.

[0041]

[Chemical 1]

[0042]

[Chemical 2]

[0043]

[Chemical 3]

In the present invention, as shown in FIG. 2, the polishing step is not used after the insulating layer is formed, the process is simplified, and the entire surface of the ink flow path is covered with the insulating layer 12.
Stable insulation and long-term reliability were obtained for the conductive ink.

Further, it is not necessary to perform the adhesion via the insulating layer, and the adhesion layer with the upper substrate can be kept at about 1 μm. Therefore, it becomes possible to transfer the displacement energy of the piezoelectric side wall to the ink without loss, and it is possible to perform printing with low driving power.

With this method, 60% of the conventional manufacturing method is used.
The manufacturing yield, which was about the same level, was satisfied almost 100% without impairing the advantage of the conventional low power driving, and the manufacturing defect due to the current leakage could be eliminated.

Further, as another effect, the corner portion formed in the cross-sectional shape of the conventional ink flow path 4 is eliminated, and the unevenness of the ink flow path surface generated by the agglomerates forming the piezoelectric element is smooth. Became. Therefore, the flow path resistance was reduced, and the bubble discharging property was improved.

In this embodiment, pyrolysis CV is used to form the insulating layer.
Although the D method was used, the treatment liquid was circulated in the ink flow path by the sol-gel method or the like to form an insulating layer such as ceramic,
It is also possible to coat the surface of the flow channel.

[0049]

According to the ink jet head and the method of manufacturing the same of the present invention, insulation reliability, reduction of flow path resistance, improvement of bubble discharge property, and reduction of driving power can be obtained, and the ink jet head has compatibility with a wide variety of ink types. In addition, it is possible to inexpensively provide an inkjet head capable of printing at low power with a good manufacturing yield, a simple manufacturing method, a constant ink discharge performance level for each nozzle and a head unit, and long-term reliability. .

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a sectional view of an ink flow path showing an inkjet head according to an embodiment of the present invention.

FIG. 3 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. 4 is a schematic diagram showing the configuration of an insulating layer forming apparatus.

FIG. 5 is a perspective view showing a configuration of a conventional inkjet head.

FIG. 6 is a sectional view of an ink flow path showing the principle of ink droplet ejection of a conventional inkjet head.

FIG. 7 is a sectional view of an ink flow path showing a conventional inkjet head manufacturing method.

FIG. 8 is a sectional view of an ink flow path showing a conventional inkjet head.

FIG. 9 is a sectional view of an ink flow path showing another conventional inkjet head.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 Nozzle Plate 3 Nozzle 4 Ink Channel 5 Piezoelectric Sidewall 6 Upper Substrate 7 Ink Supply Port 9 Ink Discharge Port 10 Electrode 11 Polarization Direction of Piezoelectric Sidewall 12 Insulating Layer 14 Surface Treatment 15 Channel Termination Opening 16 Mounting Part Electrode 20 Upper Substrate Bonding Surface 21 Piezoelectric Sidewalls, Electrodes, Insulation Layer Missing 22 Electrodes and Insulation Layer Peeling 31 Vaporizer 32 Pyrolysis Chamber 33 Deposition Chamber

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Claims (2)

[Claims] 1. A flow path and a nozzle surface disposed in the flow path for ejecting ink, a part or the whole of the flow path is made of a piezoelectric material, and an electrode for driving the piezoelectric material is provided. An ink jet head formed on a surface of a flow path in contact with ink, wherein the entire surface of the flow path in contact with ink is covered with an insulating material. 2. The method of manufacturing an ink jet head according to claim 1, wherein the step of introducing two or more kinds of gas into a tank in which the surface of the flow path is evacuated, and a reaction excitation means for the gas is used. And a step of forming a coating layer using the gas as a starting material.