JP2002248761A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of complication of steps for preventing suction of a vibrating plate and the electrode side. SOLUTION: The surface of an insulating protection film 25 for protecting an electrode 23 is modified so as to have the hydrophobic property.

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, and more particularly to an electrostatic ink jet head.

[0002]

2. Description of the Related Art As an ink jet head used in an image recording apparatus such as a printer, a facsimile, and a copying apparatus or an ink jet recording apparatus used as an image forming apparatus, a nozzle for discharging ink droplets and a discharge chamber (ink flow) communicating with the nozzle are used. Channel, ink chamber, pressure chamber, liquid chamber,
Also referred to as a pressurized chamber, a pressurized liquid chamber, and the like. ), A diaphragm forming the wall surface of the discharge chamber, and an electrode facing the diaphragm, and the diaphragm is deformed by electrostatic force to change the pressure / volume in the discharge chamber, thereby causing the ink to flow from the nozzles. 2. Description of the Related Art An inkjet head that discharges droplets is known.

In such an ink jet head, an electrostatic actuator is constituted by a diaphragm serving as a movable portion and electrodes facing the diaphragm. Electrostatic actuators with a diaphragm as a movable part include micro-pumps, micro-switches (micro-relays), multi-optical lens actuators (micro-mirrors), micro flow meters, pressure sensors, etc. Although it is used, the following mainly describes the inkjet head.

Meanwhile, in an electrostatic ink jet head, while the head is driven by repeatedly applying a voltage between the opposed electrodes (between the diaphragm and the electrodes), the surface of the opposed electrode, that is, the opposed diaphragm is driven. When moisture adheres to the electrode side surface (hereinafter simply referred to as “diaphragm surface”) or the electrode side surface (hereinafter simply referred to as “electrode side surface”), electrostatic attraction is caused by the charging of these polar molecules. The characteristics or the electrostatic repulsion characteristics may be reduced.

Further, there is a possibility that the polar molecules adsorbed on the surface of the diaphragm and the surface of the electrode side are hydrogen-bonded to each other, and the diaphragm remains stuck to the electrode side, and thus the operation becomes inoperable.
Furthermore, even if moisture does not adhere, the diaphragm may remain stuck to the electrode side as described above due to van der Waals force and electrostatic attraction.

Therefore, in a conventional electrostatic ink jet head, for example, as described in JP-A-7-13007, perfluorodecanoic acid (PFD) is used.
By forming the alignment molecular layer of A) on the surface of the diaphragm and the surface on the electrode side, these surfaces are made hydrophobic.

Further, as described in JP-A-11-179919, hexamethyldisilazane or the like (H
It is known to perform a hydrophobic treatment using MDA). This is to improve the durability by hermetically sealing a compound for forming a hydrophobic film in a space between the opposed electrodes.

[0008]

According to the method for hermetically sealing the compound for forming the hydrophobic film in the space between the counter electrodes as described above, the ink chamber due to the liquid bridging force or the hydrogen bonding force is certainly used. Adhesion of the bottom surface to the substrate side can be prevented. However, in the above sealing operation, after injecting a compound for forming a hydrophobic film between the surfaces of the opposed diaphragm and the electrode, the concentration of the compound for forming the hydrophobic film existing in the gap between the opposing surfaces is predetermined. While maintaining the value
The gap must be hermetically sealed quickly. As this method, it is necessary to form a communication hole communicating with a plurality of vibration chambers, and there is a problem that the area of the actuator increases and the cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to prevent the adhesion of water to the electrode-side surface of a diaphragm and an electrode with a simple structure and maintain operation stability and reliability. With the goal.

[0010]

In order to solve the above problems, an ink jet head according to the present invention has a structure in which the surface of an insulating protective film formed on an electrode is modified to be hydrophobic. .

Here, the surface of the insulating protective film is made of Si, N, P,
It is preferable that any one of B and As ions is implanted to be modified to be hydrophobic. Alternatively, the surface of the insulating protective film is preferably modified to be hydrophobic by plasma treatment with nitrogen gas.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view of an ink jet head according to a first embodiment of the present invention along a longitudinal direction of a diaphragm, and FIG. 2 is an explanatory cross-sectional view of the same head along a lateral direction of the diaphragm.

This ink jet head has a flow path substrate 1 using a silicon substrate, a conductive electrode substrate 2 using a silicon substrate provided below the flow path substrate 1, and an upper side of the flow path substrate 1. The nozzle unit 3 includes a flow path forming plate 4, a common ink chamber forming plate 5, and a nozzle plate 6, and the nozzle holes 7 for discharging a plurality of ink droplets, and the nozzle holes 7 communicate with each other. A liquid chamber 8 serving as an ink flow path, a common ink chamber 10 and a nozzle hole 7 communicating with each of the liquid chambers 8 through a fluid resistance portion 9 also serving as an ink supply path, and the liquid chamber 8
Is formed.

The flow path substrate 1 is, for example, an SOI (Silicon On Insulat) in which an active layer is bonded to a base substrate via an oxide film.
or) By using the substrate, the base substrate of the SOI substrate is etched to form the liquid chamber 8, and the diaphragm 15 made of an active layer whose oxide chamber is covered with an oxide film can be formed. Further, a high-concentration boron layer serving as an etching stop layer is formed in advance by injecting boron to the thickness of the vibration plate into the silicon substrate, and after joining with the second substrate 2 side, the concave portion serving as the liquid chamber 8 is filled with KOH aqueous solution or the like. Anisotropic etching may be performed using the above etching solution, and the diaphragm 15 may be formed by using the high-concentration boron layer as an etching stop layer.

On the other hand, an oxide film 21 formed by a thermal oxidation method or the like using a single crystal silicon substrate is formed on the electrode substrate 2, and an electrode forming groove (recess) 22 is formed in the oxide film 21. A predetermined gap 1 is formed on the diaphragm 15
7, an opposing electrode 23 is formed, and the diaphragm 15 and the opposing electrode 23 constitute an electrostatic actuator in which the diaphragm 15 is deformed by electrostatic force.
The gap 17 is formed in a non-parallel gap shape by forming the bottom surface of the concave portion 22 non-parallel to the diaphragm 15 in the short direction of the diaphragm.

Then, an insulating protective film 25 covering the surface of the electrode 23 is formed, and the surface 25a of the insulating protective film 25 is modified to be hydrophobic. For example, the surface of the insulating protective film 25 made of a silicon oxide film is modified to be hydrophobic by injecting any ion of Si, N, P, B, or As, or by performing a plasma treatment with nitrogen gas. I have.

The passage forming plate 4 of the nozzle unit 3 has a through hole for forming an ink supply path (fluid resistance portion) 9 and a through hole for forming a nozzle communication passage 11, and the common ink chamber forming plate 5 has a common ink. Through hole and nozzle communication passage 1 forming chamber 10
No. 1 is formed, and a nozzle plate 7 is formed with a nozzle hole 7. Then, the flow path forming plate 4 of the nozzle unit 3 is bonded onto the first substrate 1 with an adhesive 26.

The surface of the nozzle plate 6 is subjected to a water-repellent treatment. The nozzle unit 3 is provided with an ink supply port (not shown) for supplying ink to the common ink chamber 10 from outside. Further, the liquid chamber 8 and the diaphragm 1
A structure in which a nozzle plate 6 in which nozzle holes are formed on a flow path substrate in which nozzles 5 are formed may be employed.

In this ink jet head, when a driving voltage is applied between the diaphragm 15 and the counter electrode 23, the diaphragm 15 is displaced toward the electrode by electrostatic force generated between the diaphragm 15 and the counter electrode 23. As a result, the ink is supplied from the common ink chamber 10 to the liquid chamber 8 through the fluid resistance portion 9. After that, when the voltage is returned to 0, the diaphragm 15 displaced when the voltage is returned to 0 returns to the original position by the elastic force, and the ink droplet is ejected from the nozzle hole 7.

In this ink jet head, since the surface 25a of the insulating protective film 25 on the electrode is modified to be hydrophobic, the amount of adsorbed moisture is suppressed and reduced. Between the surfaces can be reduced, and the driving characteristics are stabilized over a long period of time.

Next, a first example of the manufacturing process of the ink jet head will be described with reference to FIGS.
First, as shown in FIG. 3A, a thermal oxide film 21 is formed to a thickness of about 2 μm on an electrode substrate 2 which is a silicon substrate. Then, as shown in FIG. 2B, after forming a non-parallel resist pattern using a gradation mask, the electrode forming groove 22 having a step of 0.4 to 0.5 μm in the oxide film 21 by dry etching and wet etching.
Form.

Next, a TiN film is formed on the entire surface by reactive sputtering as an electrode material, and is patterned to form an individual electrode 23 as shown in FIG. Next, as shown in FIG.
Thereby, an oxide film 31 serving as an insulating protective film is formed on the entire surface.

Thereafter, as shown in FIG. 4A, Si implantation is performed on the entire surface of the oxide film 31. Si implantation is performed with S
Using iF ₄ , implantation is performed at about 10 Kev and 1E17 to 1E18 / cm ³ to form an oxide film layer having a high Si content. It has been confirmed that the use of N, P, B, As, etc., other than Si as the implantation source is also effective in making the surface hydrophobic.

Next, as shown in FIG. 1B, a resist pattern 32 is formed to cover a region to be left as an insulating protective film, and the oxide film 31 is removed by etching.
As shown in FIG. 4C, an insulating protective film 25 made of an oxide film 31 whose surface has been modified to be hydrophobic is formed, and then, as shown in FIG. 4D, the resist pattern 32 is removed.

Thereafter, as shown in FIG. 5 (a), the flow path substrate 1 is bonded directly to the electrode substrate 2 to form a flow path-shaped pattern and anisotropic etching is performed. The diaphragm 15 and the liquid chamber 8 are formed. Then, as shown in FIG. 2B, the nozzle unit 3 is bonded onto the flow path substrate 1 with an adhesive 26. .

Next, a second example of the manufacturing process of the ink jet head will be described with reference to FIGS.
First, as shown in FIG. 6A, a thermal oxide film 21 is formed to a thickness of about 2 μm on an electrode substrate 2 which is a silicon substrate. Then, as shown in FIG. 2B, after forming a non-parallel resist pattern using a gradation mask, the electrode forming groove 22 having a step of 0.4 to 0.5 μm in the oxide film 21 by dry etching and wet etching.
Form.

Next, a TiN film is formed on the entire surface by reactive sputtering as an electrode material, and is patterned to form an individual electrode 23 as shown in FIG. Next, as shown in FIG.
Thereby, an oxide film 31 serving as an insulating protective film is formed on the entire surface.

Thereafter, as shown in FIG. 7A, the entire surface of the oxide film 31 is subjected to a plasma process using nitrogen gas. In the plasma processing, for example, a wafer is held in a parallel plate plasma reaction chamber, and several hundred sccm of nitrogen gas and a degree of vacuum of 0.3 to 0.5 are used.
KPa, RF power of about 400 to 500 W for 3 to 5 minutes. Thus, a nitride layer of 3 to 5 nm is formed on the surface of the oxide film 31. This nitride layer shows hydrophobicity, and can suppress moisture adsorption of the oxide film.

Next, as shown in FIG. 2B, a resist pattern 32 is formed to cover the region to be left as an insulating protective film, and the oxide film 31 is removed by etching.
As shown in FIG. 4C, an insulating protective film 25 made of an oxide film 31 whose surface has been modified to be hydrophobic is formed, and then, as shown in FIG. 4D, the resist pattern 32 is removed.

Thereafter, as shown in FIG. 8 (a), the flow path substrate 1 is joined to the electrode substrate 2 by direct bonding or the like to form a flow path shape pattern, and anisotropic etching is performed. The diaphragm 15 and the liquid chamber 8 are formed. Then, as shown in FIG. 2B, the nozzle unit 3 is bonded onto the flow path substrate 1 with an adhesive 26. .

Next, a third example of the manufacturing process of the ink jet head will be described with reference to FIG. In this example, in the manufacturing process of the first example, Si ions are implanted after the pattern formation of the insulating protective film 25.

In this case, since Si ions are also implanted into the surface of the thermal oxide film 21 which is a bonding surface with the flow path substrate 1,
A decrease in the hydrophilicity required for the direct bonding surface of the flow path substrate 1 and the electrode substrate 2 slightly lowers the bonding strength. It was confirmed that the effect was greater.

Next, a fourth example of the manufacturing process of the ink jet head will be described with reference to FIG. In this example, in the manufacturing process of the second example, N ₂ plasma processing is performed after the patterning of the insulating protection film 25.

Also in this case, since a nitride layer is also formed on the surface of the thermal oxide film 21 serving as a bonding surface with the flow path substrate 1, hydrophilicity required for the direct bonding surface between the flow path substrate 1 and the electrode substrate 2 is required. Although the bonding strength decreases slightly due to the lowering of the property, it was confirmed that the effect of hydrophobizing the surface of the insulating protective film 25 was larger than that of the third example.

Although the above embodiment has been described by taking an electrostatic ink jet head as an example of an ink jet head, the present invention can be similarly applied to a piezo ink jet head in which a diaphragm is deformed by a piezoelectric element. Also,
Besides the inkjet head, a microactuator having a diaphragm as a movable part, for example, a micropump,
The present invention can be similarly applied to a micro switch (micro relay), a multi-optical lens actuator (micro mirror), a micro flow meter, a pressure sensor, and the like.
Further, for example, the present invention can be applied to a droplet discharge head that discharges a liquid resist for patterning as a droplet discharge head other than the inkjet head.

Further, in the above embodiment, the present invention is applied to a side shooter type ink jet head in which the direction of displacement of the diaphragm and the direction of ejecting ink droplets are the same.
The present invention can be similarly applied to an edge shooter type inkjet head in which the diaphragm displacement direction and the ink droplet ejection direction are orthogonal.

As described above, according to the ink jet head of the present invention, the surface of the insulating protective film formed on the electrodes is modified to be hydrophobic, so that the vibration can be performed in a simple process. The adhesion between the plate and the electrode can be prevented, the operating characteristics are stabilized, and the reliability is improved.

Here, the surface of the insulating protective film is made of Si, N, P,
Either ion of B or As is implanted and modified to be hydrophobic, so that the process is simplified and the cost can be reduced. Alternatively, the process can be simplified and the cost can be reduced even if the surface of the insulating protective film is modified to be hydrophobic by plasma treatment with nitrogen gas.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view along a longitudinal direction of a diaphragm of an ink jet head according to the present invention.

FIG. 2 is an explanatory cross-sectional view of the head taken along a lateral direction of a diaphragm.

FIG. 3 is an explanatory cross-sectional view of a main part along a lateral direction of a diaphragm for explaining a first example of a manufacturing process of the inkjet head.

FIG. 4 is an explanatory cross-sectional view of a main part explaining a step following FIG. 3;

FIG. 5 is an explanatory cross-sectional view of a main part explaining a step following FIG. 4;

FIG. 6 is an explanatory cross-sectional view of a main part along a lateral direction of a diaphragm for explaining a second example of the manufacturing process of the inkjet head.

FIG. 7 is an explanatory cross-sectional view of a main part explaining a step following FIG. 6;

FIG. 8 is an explanatory cross-sectional view of a main part explaining a step following FIG. 7;

FIG. 9 is an explanatory cross-sectional view of a main part, used for describing a third example of the manufacturing process of the inkjet head.

FIG. 10 is an explanatory sectional view of a main part, used for describing a fourth example of the manufacturing process of the inkjet head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flow path board, 2 ... Electrode board, 3 ... Nozzle unit, 8
... liquid chamber, 15 ... diaphragm, 17 ... gap, 21 ... insulating film, 23 ... electrode, 24 ... electrode separating groove, 25 ... insulating protective film.

Claims (3)

[Claims] 1. A vibration plate having a nozzle for discharging ink droplets, a liquid chamber with which the nozzle communicates, a vibration plate forming a wall surface of the liquid chamber, and a counter electrode facing the vibration plate. Wherein the surface of an insulating protective film formed on the electrode is modified to be hydrophobic in an ink jet head that discharges ink droplets from the nozzles by deforming the nozzle with electrostatic force. 2. The ink jet head according to claim 1, wherein the surface of the insulating protective film is formed of Si, N, P, B, and A.
An ink-jet head, wherein any one of s is implanted to be modified to be hydrophobic. 3. The ink jet head according to claim 1, wherein the surface of the insulating protective film has been modified to be hydrophobic by plasma treatment with nitrogen gas.