JP3173187B2 - Ink jet head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head. More specifically, the present invention relates to an ink jet head for selectively adhering ink droplets to 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 ink jet head used in an ink jet printer, but can generally be divided into two methods. That is, the first method uses a piezoelectric material to generate a pressure pulse in the ink chamber, thereby ejecting an ink droplet from a nozzle. The second method uses a heating resistor to generate a vapor bubble in an ink chamber and eject ink droplets from nozzles.

[0003] The second method has a problem that the heating resistor is easily deteriorated due to repeated heating and cooling of the heating resistor, resulting in poor durability. 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 problem. However, in the first method, since the efficiency of the piezoelectric material is low, the size of the ink jet head itself increases. In addition, the manufacturing process becomes complicated, is not suitable for mass production, and 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 used.

As a method for solving the problem of the first method,
Japanese Patent Application Laid-Open No. 63-247501 discloses a method in which a plurality of parallel rectangular cross-sectional channels having an interval in the direction in which the nozzles are arranged are provided, and an electrode is formed on a part or the entire surface of the side wall of the flow channel. The side wall is partially or entirely made of a piezoelectric material, and the side wall deforms parallel to the direction in which the flow paths are arranged, changes the pressure in the flow path, and moves the ink droplet to one end of the flow path. An inkjet head that forms and discharges ink has been proposed.

The structure of a conventional ink jet head will be described with reference to FIG. 5, and the operation of ink ejection will be described with reference to FIG. FIG. 5 is a perspective view showing the configuration of a conventional ink jet head, and FIG.
FIG. 3 is a sectional view of an ink flow path showing a structure of a conventional inkjet head. 1 is a piezoelectric substrate, 2 is a nozzle plate,
Reference numeral 3 denotes a nozzle, 4 denotes an ink flow path, 5 denotes a side wall made of a piezoelectric material (hereinafter abbreviated as a piezoelectric side wall), 6 denotes an upper substrate, 7 denotes an ink supply port, 9 denotes an ink discharge port, 10 denotes an electrode, and 11 denotes polarization. Direction, 15 is a flow path terminal opening, 16 is a mounting part electrode, 20
Denotes an upper substrate bonding surface.

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

The operation of ink ejection of a 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 no voltage pulse is applied to the electrodes 10 formed on both surfaces by an electric driving means (not shown). In FIG. 6B, when a voltage pulse is applied, the piezoelectric side wall 5 is distorted to the reverse surface of the piezoelectric side wall in the direction of polarization, and the pressure generated by the reduction in the volume of the ink flow path 4 causes the ink to flow. A part of the ink filling the flow path 4 is ejected from the nozzle 3 as ink droplets, and the other part is discharged to the ink storage tank side via the ink supply port 7. After the ink droplets are ejected, the ink is supplied to the nozzle 3 from the ink storage tank via 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, so that the structure is in direct contact with the ink. For this reason, when a water-based ink or the like having a high conductivity is used, a current leaks in the ink due to the application of a voltage during ejection,
Corrosion of the electrodes, deterioration of the ink, and the like occur.

For this reason, inks having low conductivity, for example, oil-based inks, have been used. However, oil-based inks have larger print bleeding and are more likely to cause clogging of nozzles than water-based inks. Sufficient print quality cannot be obtained. In addition, it has disadvantages such as harm and danger.

[0010]

An ink jet head according to the present invention has a flow path and a nozzle communicating with the flow path, and a part or the whole of the flow path is made of a piezoelectric material, and the ink in the flow path is formed. forming an insulating layer on a surface in contact with an ink jet head for discharging ink from the nozzle by applying an electric field to the piezoelectric material, the insulation of the channel
The edge layer is covered with a hydrophilic film made of alumina or zirconia. Further, the hydrophilic film is formed by circulating a liquid obtained by diluting an alumina sol or a zirconium sol. Further, in the method of manufacturing an inkjet head, a step of introducing, circulating, and discharging an alkaline cleaning liquid into the flow path, a step of circulating pure water, a step of circulating ethanol, a step of circulating air, The method includes a step of circulating a solution obtained by diluting the zirconium sol with ethanol, a step of circulating air, and a step of drying the channel.

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

FIG. 9 is a sectional view of an ink flow path showing a conventional method of manufacturing an ink jet head. 1 is a piezoelectric substrate,
4 is an ink channel, 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 cross-sectional view of the ink flow path after the electrodes have been formed. A piezoelectric side wall 5 having a groove width of 80 μm is formed on the piezoelectric substrate 1 bonded in the opposite polarization direction.
0 is formed.

Next, unnecessary electrodes on the upper surface of the piezoelectric substrate 1 are removed, and a flat upper substrate bonding surface 20 is obtained. The cross-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 side walls 5 are formed. The cross-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 surfaces of the piezoelectric substrate 1 and the upper substrate 6.

The ink supply means is connected to a drive means for generating an applied pulse.

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

A method for forming an insulating layer by a 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, 32
Denotes a thermal decomposition chamber, and 33 denotes a vapor deposition chamber.

Chemical formula 1 is diparaxylylene which is a raw material of the organic insulating layer. Diparaxylylene is a dimeric solid at room temperature. Diparaxysilylene is vaporized in the vaporization chamber 31,
It is heated and vaporized at 1 Torr and 175 ° C. 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 diradical paraxylylene shown in Chemical formula 2.

The diradical para-xylylene can be used at room temperature, at 0.
It is introduced into a 1 Torr vapor deposition chamber, where it is adsorbed on the substrate and polymerized, resulting in polyparaxylylene shown in Chemical Formula 3, and an organic insulating layer is formed on the entire surface of the substrate and the entire surface of the ink flow path.

The substrate on which the organic insulating layer is formed is -70.
The temperature was reduced to 0.001 Torr at a temperature of 10.degree. C., and a closely adhered insulating layer was obtained.

[0026]

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[0027]

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[0028]

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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 aqueous 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 poor affinity for water-based ink and repels commonly used water-based ink. Therefore, it is difficult to completely fill the ink flow path with the ink. In addition, bubbles are easily drawn in at the time of ink ejection, so that a large number of nozzles cannot be ejected, and printing often has missing dots.

Further, the bubble discharge performance by the cleaning operation (absorbing the air bubbles accumulated in the ink flow path by sucking from the nozzles, ie, completely filling the ink flow path with the ink) is also poor. For this reason, stable printing for a long time is difficult, and a large number of cleaning operations are required for a fixed amount of printing.

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

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 a problem, and an object of the present invention 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 discharging ink arranged in the flow path, and a part or the whole of the flow path is formed. In an inkjet head, the piezoelectric head is formed of a piezoelectric material, and a driving electrode of the piezoelectric material is formed on a surface of the flow path in contact with the ink, and an entire surface of the flow path in contact with the ink is provided with an insulating layer. The flow path is covered with a hydrophilic substance, and the surface of the flow path is coated by circulating a liquid in the flow path.

[0037]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. The present invention is not limited to the following examples.

First, an example of the ink jet head of the present invention is shown in FIGS. FIG. 1 is a cross-sectional view of an ink flow path of an inkjet head according to an embodiment of the present invention, and FIG. 2 is a perspective view of the inkjet head.

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 the same as 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 obtained by hydrating alumina to form a sol, and exhibits excellent affinity for water due to the contained hydroxy group. Alternatively, a hydrophilic layer can be formed using zirconium sol or the like.

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

Hereinafter, a method for forming a hydrophilic layer in the method of manufacturing an ink jet head according to the present invention will be described with reference to FIG.

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

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

Similarly, pure water is circulated in the ink flow path 4 to remove the cleaning liquid.

The ethanol is circulated to remove water.

Introduce air and dry the surface.

Alumina sol is diluted with ethanol to reduce the viscosity and facilitate circulation, and circulates in the flow channel.

Air is introduced to evaporate the ethanol content.

The alumina sol remaining on the surface is cured by heating in a dryer.

Here, a tube pump is used as the liquid circulating means, but it is also possible to circulate the liquid and dry the surface by suction under reduced pressure.

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

In the present invention, since the ink flow path is covered with the hydrophilic film made of alumina or zirconia, ink filling at the time of ink ejection is facilitated.

In addition, since the affinity for the ink on the surface of the ink flow path was improved, bubbles were less likely to be drawn into the ink flow path, so that frequent cleaning operations became unnecessary and the printing speed was improved.

Further, the air bubbles drawn into the flow path can be easily discharged, and the air bubbles can be discharged by a simple cleaning mechanism.

As another effect, since the cross-sectional shape of the ink flow path was smooth, the flow path resistance was reduced, and discharge at a low voltage became possible. The smoothness of the cross section of the flow path is effective also as a measure for drawing and discharging bubbles.

Further, since the insulating material is further coated after the formation of the insulating layer, the insulation reliability is improved, and the number of non-dischargeable nozzles due to insulation failure 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 discharging property, the dot missing is reduced, and the insulation reliability is obtained. It is possible to provide an ink jet head having high printing quality and high printing quality and long-term reliability.

[Brief description of the drawings]

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

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

FIG. 3 is a schematic view showing a method for forming a hydrophilic layer of an ink jet head according to one embodiment of the present invention.

FIG. 4 is a cross-sectional view of a nozzle portion showing one embodiment of the present invention.

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

FIG. 6 is a cross-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 inkjet head manufacturing method.

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

[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 Nozzle plate adhesion surface 9 Ink discharge port 10 Electrode 11 Polarization direction of piezoelectric side wall 12 Organic insulating layer 13 Processing used for forming hydrophilic layer Liquid 14 hydrophilic layer 15 flow path end opening 16 mounting part electrode 17 liquid circulation means 20 upper substrate bonding surface 31 vaporizer 32 thermal decomposition chamber 33 evaporation chamber

Claims (3)

(57) [Claims] Claims: 1. There is provided a flow path and a nozzle communicating with the flow path,
A part or the whole of the flow path is formed of a piezoelectric material, an insulating layer is formed on a surface of the flow path in contact with the ink, and an ink is ejected from the nozzle by applying an electric field to the piezoelectric material. An ink-jet head , wherein the insulating layer of the flow path is covered with a hydrophilic film made of alumina or zirconia. 2. The method according to claim 1, wherein the hydrophilic film is formed by circulating a liquid obtained by diluting an alumina sol or a zirconium sol. 3. A step of introducing, circulating, and discharging an alkaline cleaning liquid into the flow path, a step of circulating pure water, a step of circulating ethanol, a step of circulating air, and a step of converting alumina or zirconium sol into ethanol. 2. The method according to claim 1, further comprising the steps of: circulating the solution diluted in step (a), circulating air, and drying the flow path.