JPH06143570A - Ink jet head and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve bubble discharging properties by covering a front surface of an ink channel with a hydrophilic layer. CONSTITUTION:An ink jet head comprises ink channels 4, and nozzles hole arranged in contact with the channels 4 for discharging ink in such a manner that the channels 4 are formed partly or entirely of a piezoelectric material, wherein entire surfaces of electrodes 10 and the channels 4 formed with an inorganic insulating layer 12 is covered with a hydrophilic layer 14.

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 the conventional ink jet head will be described with reference to FIG. 5, and the ink ejection operation will be described with reference to FIG. FIG. 5 is a perspective view showing the configuration of a conventional inkjet head, and FIG.
FIG. 7 is a sectional view of an ink flow path showing the structure of a 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 piezoelectric side wall), 6 is an upper substrate, 7 is an ink supply port, 9 is an ink discharge port, 10 is an electrode, 11 is polarization. Direction, 15 is a channel end opening, 16 is a mounting portion electrode, 20
Is the 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. 6 (a),
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.

However, 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, an oil-based ink is used, the oil-based ink has a larger print bleed than the water-based ink, and the nozzle is likely to be clogged. Sufficient print quality cannot be obtained. It also has drawbacks such as being harmful and dangerous.

To solve the above problems, the present inventor has proposed to form an organic insulating layer in the flow channel.

The structure of a conventional ink jet head will be described below with reference to FIGS. 7 and 8, and the conventional method of manufacturing an ink jet head will be described with reference to FIG.

FIG. 9 is a sectional view of an ink flow path showing a conventional ink jet head manufacturing method. 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. 9A is a sectional view of the ink flow path after the electrodes are formed. The piezoelectric side wall 5 having a groove width of 80 μm is formed on the piezoelectric substrate 1 bonded in the opposite polarization direction, and the electrode 1
Form 0.

Next, unnecessary electrodes on the upper surface of the piezoelectric substrate 1 are removed 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. The sectional shape of the ink flow path is as shown in FIG.

The organic insulating layer 12 is formed on the surface of the ink flow path by a thermal decomposition CVD (chemical vapor deposition) method or the like. 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. 10 shows the structure of a thermal decomposition CVD apparatus. In the figure, 1 is a piezoelectric substrate, 31 is a vaporizer, and 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 organic insulating layer. Diparaxylylene is a dimeric solid at room temperature. Diparaxylylene is in the vaporization chamber 31,
It is heated at 1 Torr and 175 ° C. to be 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 para-xylylene is at room temperature, 0.
It is introduced into a vapor deposition chamber of 1 Torr, and 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 and the ink flow path.

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.

[0026]

[Chemical 1]

[0027]

[Chemical 2]

[0028]

[Chemical 3]

According to the above proposal, it is possible to completely cover the ink flow path with the insulator, and it is possible to stably discharge the water-based ink for a long period of time.

[0030]

However, the conventional ink jet head has the following problems.

The surface of the organic insulating layer formed on the surface of the ink flow path has a poor affinity for water-based ink and repels water-based ink that is generally used. Therefore, it is difficult to completely fill the ink flow path with ink. In addition, air bubbles were easily drawn in during ink ejection, many nozzles were unable to eject, and many dot omissions occurred in printing.

Furthermore, the air bubble dischargeability due to the cleaning operation (by sucking air bubbles accumulated in the ink flow path by sucking from the nozzle, that is, completely filling the ink flow path with ink) is also poor. Therefore, it is difficult to perform stable printing for a long time, and a large number of cleaning operations are required for a fixed amount of printing.

As described above, it is difficult for the conventional ink jet head to improve the printing speed and the reliability for fine printing due to the water repellency of the organic insulating layer.

Further, regarding the surface modification, it is difficult to uniformly treat the surface of the ink flow path because the flow path has a structure deeper than the width.

An object of the present invention is to solve such problems, and an object thereof is to provide an ink jet head having excellent printing quality, long-term reliability and capable of high-speed printing at low cost.

[0036]

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 inkjet head in which an electrode for driving the piezoelectric material is formed on a surface of the flow path in contact with ink, and an insulating layer is formed on the entire surface of the flow path in contact with the ink, The channel is coated with a hydrophilic substance, and the surface of the channel is coated by circulating a liquid in the channel.

[0037]

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 sectional view of an ink flow path of an inkjet head showing an embodiment of the present invention, and FIG. 2 is a perspective view of the inkjet head.

In FIGS. 1 and 2, 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, 12 is an organic insulating layer, and 14 is a hydrophilic layer. is there. The ejection operation is similar to that of the conventional inkjet head.

In one embodiment of the present invention, the hydrophilic layer 14 is formed on the entire surface of the organic insulating layer 12 formed on the entire surface of the ink flow path 4.
Is formed.

Here, alumina sol is used as the material of the hydrophilic layer. Alumina sol is a sol obtained by hydrating alumina and has an excellent affinity for water due to the contained hydroxy groups. In addition, it is possible to form a hydrophilic layer using zirconium sol or the like.

By forming the hydrophilic layer with alumina sol,
The contact angle with respect to the ink on the surface of the ink flow path, which was about 60 degrees in the past, could be set to 20 degrees or less.

The method of forming the hydrophilic layer in the method of manufacturing an ink jet head of the present invention will be described below with reference to FIG.

FIG. 3 is a perspective view showing an apparatus structure of a hydrophilic layer forming method of an ink jet head manufacturing method according to an embodiment of the present invention.

A tube pump is used as the liquid circulation means 17, and an alkaline cleaning liquid is introduced from the ink supply port 7, circulated in the ink flow path 4 and discharged from the ink discharge port 9.

Similarly, the cleaning liquid is removed by circulating pure water in the ink flow path 4.

The water is removed by circulating ethanol.

Air is introduced to dry the surface.

Alumina sol diluted with ethanol to reduce viscosity and facilitate circulation is circulated in the flow path.

Air is introduced to evaporate the ethanol content.

By heating in a dryer, the alumina sol remaining on the surface is cured.

Although a tube pump is used as the liquid circulating means here, it is also possible to circulate the liquid and dry the surface by vacuum suction.

Further, as shown in FIG. 4, it is also possible to form the hydrophilic layer 14 on the inner surface of the nozzle by the above-mentioned treatment after the nozzle plate 2 is bonded.

In the present invention, the hydrophilic layer is formed on the entire surface of the ink flow path, which facilitates ink filling during ink ejection.

Further, since the affinity with the ink on the surface of the ink flow path is improved, bubbles are less likely to be drawn into the ink flow path, frequent cleaning operations are unnecessary, and the printing speed is improved.

Further, it is easy to discharge the air bubbles drawn into the flow path, and it is possible to discharge the air bubbles with a simple cleaning mechanism.

As another effect, since the cross-sectional shape of the ink flow path is smooth, the flow path resistance can be reduced, and ejection at a low voltage is possible. The smooth cross section of the flow path also has an effect as a measure for drawing in and discharging bubbles.

Further, since the insulating material is further coated after the insulating layer is formed, the insulation reliability is improved and the number of nozzles that cannot be ejected due to poor insulation is reduced.

[0059]

According to the ink jet head and the method of manufacturing the same of the present invention, the flow path resistance is reduced, the cleaning operation is simplified by improving the bubble discharge property, the dot dropout is reduced, and the insulation reliability is excellent. It is possible to provide an inkjet head that has high printing quality and long-term reliability and is capable of high-speed printing.

[Brief description of drawings]

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

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

FIG. 3 is a schematic diagram showing a method for forming a hydrophilic layer of an inkjet head according to an embodiment of the present invention.

FIG. 4 is a sectional view of a nozzle portion showing an embodiment of the present invention.

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 perspective view showing the configuration of another conventional inkjet head.

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

FIG. 9 is a cross-sectional view of an ink flow path showing another conventional method for manufacturing an inkjet head.

FIG. 10 is a schematic diagram showing a device configuration of a thermal decomposition CVD method.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 Nozzle Plate 3 Nozzle 4 Ink Flow Path 5 Piezoelectric Sidewall 6 Upper Substrate 7 Ink Supply Port 8 Nozzle Plate Adhesive Surface 9 Ink Discharge Port 10 Electrode 11 Polarization Direction of Piezoelectric Sidewall 12 Organic Insulation Layer 13 Treatment Used to Form Hydrophilic Layer Liquid 14 Hydrophilic Layer 15 Channel End Opening 16 Mounting Part Electrode 17 Liquid Circulation Means 20 Upper Substrate Bonding Surface 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 having an insulating layer formed on the entire surface of the flow path, which is in contact with the ink, and the entire surface of the flow path, which is in contact with the ink, is coated with a hydrophilic substance. 2. A flow path and a nozzle surface disposed in the flow path for ejecting ink, wherein 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. A method for manufacturing an inkjet head, characterized in that the entire surface of the flow path, which is in contact with the ink, is covered with a hydrophilic substance by circulating a liquid in the flow path. .