JPH068430A - Ink jet head and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve insulation reliability, simplify a process, and reduce 8 unit price by forming an ink passage with an insulating layer or an electrode without using an upper substrate. CONSTITUTION:An ink jet head comprises an ink passage 4 and a nozzle 3 for discharging ink connected to the ink passage 4. The whole part or one part of the ink passage 4 is made of piezoelectric material. A surface of an electrode 10 formed on the surface of the ink passage 4 is covered with an insulating layer 12 and an ink passage top wall 14 is made of the insulating 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 wholly formed of a piezoelectric material, and the side wall is deformed in parallel to the direction in which the flow paths are arranged to change the pressure in the flow path and is formed at one end of the flow path. Inkjet heads that eject ink droplets have been proposed.

The structure of a conventional ink jet head will be described with reference to FIG. FIG. 6 is a diagram showing a configuration of a conventional inkjet head. 1 is a piezoelectric substrate, 2 is a nozzle plate, 3 is a nozzle hole, 4 is an ink flow path, and 5 is a side wall made of a piezoelectric material (hereinafter abbreviated as a piezoelectric side wall). , 6 is the upper substrate, 7
Is an ink supply port, 9 is an ink ejection port, 10 is an electrode, 15
Is a channel end opening, and 16 is a mounting part electrode.

In this ink jet head, a large number of ink flow paths 4 which are parallel to each other are formed. Ink flow path 4
Is an upper substrate in a groove formed in the piezoelectric substrate 1, and has a rectangular cross section. One end of the ink flow path 4 is connected to the slit-shaped ink ejection port 9 and the nozzle plate 2
It is connected to the nozzle 3 formed in. In addition, the ink flow path 4
The other end is covered with an upper substrate 6 having an ink supply port 7, and the flow path end opening 1 corresponding to each ink flow path 4 is formed.
5, it is connected to an ink storage tank (not shown) via the ink supply port 7.

The ink ejection operation of the conventional ink jet head will be described with reference to FIG. 7 showing the cross section of the flow path.
In FIG. 7A, the piezoelectric side wall 5 is formed of two piezoelectric ceramics having different polarization directions 11. Figure 7
In (a), the piezoelectric side wall 5 has electrodes 10 formed on both sides.
In addition, since the voltage pulse is not applied from the electric driving means (not shown), it is not deformed. In FIG. 7B, 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. Part of the ink that fills the flow path 4 is ejected as an ink droplet from the nozzle opening 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 from the ink storage tank to the nozzle hole 3 through the ink supply port 7 and the flow path 4 by the capillary force of the nozzle 3.

[0008]

However, in the above structure, the electrode is exposed in the ink flow path and directly contacts the ink. Therefore, when a water-based ink or the like having a high electric conductivity is used, a current leaks in the ink due to the voltage application at the time of ejection, which causes corrosion of the electrodes and deterioration of the ink.

Due to the above problems, use of oil-based ink having a low electric conductivity has been forced. However, oil-based ink has a larger print blur than water-based ink,
Nozzles are apt to be clogged, and there are drawbacks such as harmfulness and danger, and sufficient printing quality has not been obtained.

In addition, when the upper substrate is bonded, the bonding surface must be polished until it is sufficiently flat in order to obtain a flow path without ink leakage. Therefore, the outer shape accuracy cannot be obtained, and it is difficult to obtain the shape as designed. Furthermore, the adhesive often flows out due to capillary force and blocks the ink flow path, requiring careful attention and a special method when applying the adhesive. was there.

Further, when the insulating layer is formed for the use of the ink having high electric conductivity, the following problems occur. FIG. 8 is a sectional view of an ink flow path of a conventional inkjet head. In many cases, the insulating layer on the wall surface, the missing electrode 21, and the peeling 22 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.

Even if a small amount of current leaks that does not hinder the ejection of ink droplets, it may cause ejection failure due to corrosion of the electrodes and deterioration of the ink due to long-term use. Further, when the adhesive layer with the upper substrate 6 was not sufficiently uniform, the ink penetrated through the gap and the same adverse effect occurred.

Further, in the case of manufacturing a long line head, due to the shrinkage of the adhesive, the difference in the coefficient of thermal expansion between the members, etc.
Distortion and breakage occurred, the manufacturing yield was poor, and it was difficult to keep the print quality constant.

The present invention solves such a problem, has a wide range of ink types, 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 an inkjet head having excellent properties.

[0015]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem, and in an ink jet head having a flow path and a nozzle surface for ejecting ink disposed in the flow path, It is characterized in that a closed channel is formed by a coating material that covers a part or the entire surface. Further, in the ink jet head in which a part or all of the flow path is made of a piezoelectric material, the electrode surface formed on the flow path surface is covered, and the coating is an insulator. And Furthermore, in the coating of the ink flow path, a temporary lid is provided in the groove formed on the substrate, the surface of the flow path is covered, and the groove is closed with the coating material,
It is characterized in that the temporary flow path wall is removed.

[0016]

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 FIG. 1 to explain the structure. FIG. 1 is a perspective view of an inkjet head showing an embodiment of the present invention. 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 insulating layer,
Reference numeral 14 is an ink channel top wall. The ejection operation is similar to that of the conventional inkjet head.

Compared with the conventional ink jet head, the structure is such that the upper substrate 6 shown in FIG. 6 is not used, and the ink channel top wall 14 is formed of the insulating layer 12.

FIG. 2 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. 1 is a piezoelectric substrate, 4 is an ink flow path, 5 is a piezoelectric side wall, 10 is an electrode, 12 is an insulating layer, 13 is a temporary upper substrate, 14 is an ink flow path top wall, 15 is a flow path end opening, 16 is mounting It is a partial electrode.

The ink jet head manufacturing method of the present invention will be described below.

FIG. 2A 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 is Ni-Cr 1.0 μm and Au is 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.

Next, as shown in FIG. 2B, the piezoelectric side wall 5 is formed to form the organic insulating film 12 on the surface of the ink flow path 4.
The temporary upper substrate 13 is adhered on top. It is desirable that the temporary upper substrate 13 be flat and have high surface water repellency.

As shown in FIG. 2C, thermal decomposition CVD
The insulating layer 12 is formed by a method or the like, and the temporary upper substrate 13 is removed. At this time, unnecessary portions of the insulating layer are masked to prevent formation of the insulating layer.

The nozzle plate is bonded to the piezoelectric substrate 1.

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.

In the present invention, as shown in the ink flow path sectional view of FIG. 2C, the entire surface of the electrode 10 is covered with the insulating layer 12 without using a polishing step after the insulating layer is formed. Stable insulation and long-term reliability were obtained for the functional ink.

By this method, the manufacturing yield, which was about 60% in the conventional method, was satisfied almost 100%, and the manufacturing defects due to current leakage could be eliminated.

Further, since the ink flow path is formed without joining the members, the substrate was not distorted or damaged even when a long line head was manufactured.

Further, as another effect, the cross-sectional shape of the ink flow path 4 is changed from a rectangular shape to a corner shape, the flow path resistance is reduced, and the bubble discharging property is 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 possible to form a flow path.

By circulating the electroless plating solution in the ink flow path, it was possible to form the ink flow path top wall using the electrodes. FIG. 3 is a cross-sectional view of the inkjet head of the present invention when electrodes are formed by electroless plating. Reference numeral 1 is a piezoelectric substrate, 4 is an ink flow path, 5 is a piezoelectric side wall, 10 is an electrode, 12 is an insulating layer, and 14 is an ink flow path top wall.

FIG. 4 shows a sectional view of the ink flow path, and the electrode forming method will be described.

The temporary upper substrate 1 is formed on the piezoelectric substrate 1 having the grooves formed therein.
Stick 3 together. The method of forming the groove is as described above.

Electroless nickel plating solution is circulated in the ink flow path 4 formed by the piezoelectric substrate 1 and the temporary upper substrate 13 to form the electrode 10. The formed electrode has the flow channel cross-sectional shape shown in FIG.

The subsequent steps are the same as the above steps.

The temporary upper substrate 13 is removed, and the insulating layer 12 is formed by the thermal decomposition CVD method or the like. The flow channel cross-sectional shape is as shown in FIG.

The nozzle plate is bonded to the piezoelectric substrate 1.

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

In this method, as in the case of forming the insulating layer, the temporary upper substrate 13 is adhered to the upper surface of the piezoelectric sidewall 5 and electroless plating is performed to form the electrode 10. Therefore, an unnecessary electrode is not formed on the upper portion of the piezoelectric side wall 5, and the electrode peeling step is unnecessary. As a result, the process can be simplified and the head unit price can be reduced.

Further, with this structure, the top wall 14 of the ink flow path becomes stronger, more stable ejection is possible, and long-term reliability is improved.

Further, as shown in the sectional view of the ink flow path in FIG. 5, the density can be easily increased by joining two ink jet heads of the present invention.

Further, the present invention was also useful for forming the ink flow path of an ink jet head having a structure having no electrode on the surface of the ink flow path.

[0045]

According to the ink jet head and the manufacturing method of the present invention, it is possible to manufacture with high accuracy, having a wide range of ink compatibility, a good manufacturing yield, and a simple manufacturing process. It is possible to provide an inkjet head that can be made denser, has a constant performance level of ink ejection in units of nozzles and heads, and long-term reliability, and can be easily made into a line head.

[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 a method for manufacturing an inkjet head according to an embodiment of the present invention.

FIG. 3 is a sectional view of an ink flow path showing an inkjet head according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of an ink flow path after electrode formation in an inkjet head manufacturing method according to another embodiment of the present invention.

FIG. 5 is a sectional view showing an ink flow path of an application example of the inkjet head of the present invention.

FIG. 6 is a perspective view showing a configuration of a conventional inkjet head.

FIG. 7 is a sectional view showing the principle of ink droplet ejection of a conventional inkjet head.

FIG. 8 is a cross-sectional view showing an ink flow path of a 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 13 Temporary Upper Substrate 14 Ink Channel Topwall 15 Channel Terminal opening 16 Mounting part electrode 20 Upper substrate bonding surface 21 Piezoelectric side wall, electrode, lack of insulating layer 22 Peeling of electrode, insulating layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area B41J 2/16

Claims (3)

[Claims] 1. An ink jet head having a flow path and a nozzle surface for ejecting ink disposed in the flow path, wherein a closed flow formed by a coating material covering a part or the whole surface of the flow path. An inkjet head having a path. 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. The inkjet head according to claim 1, wherein the electrode surface formed on the road surface is covered, and the covering is an insulator. 3. The ink flow path coating of the ink jet head according to claim 1, wherein a groove formed on the substrate is provided with a temporary lid to cover the surface of the flow path, and the groove is formed by the coating material. The method of manufacturing an inkjet head, wherein the temporary flow path wall is removed after the closed flow path is closed.