JP2002272144A - Electrostatic actuator and ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic actuator and an ink jet head, which are capable of rejecting defective actuators and reducing characteristic variation by setting an optimum circuit correction value and improving the yield. SOLUTION: This electrostatic actuator includes a sealed hollow space 20 with one of its wall surfaces being constituted of a vibration plate 10 serving as a movable section and the same membrane 10m, where preferably, the fixed end width of the membrane 10m is specified as the width of the sealed hollow space 20. In is also preferable that the vibration plate and/or a casing which forms the vibration plate be formed from a surface oriented silicon substrate. Furthermore, it is preferable that '1' with different membrane fixed end width or a plurality of sealed hollow space be established.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator and an ink jet head.

[0002]

2. Description of the Related Art An ink jet head used in an image recording apparatus such as a printer, a facsimile, a copying machine, a plotter or the like which is used as an image forming apparatus has a nozzle for discharging ink droplets and a pressurized communication with the nozzle. Liquid chamber (liquid chamber, pressurized chamber, pressure chamber,
Also referred to as a discharge chamber, an ink flow path, or the like. ), And an electrostatic actuator having a vibrating plate forming the wall surface of the pressurized liquid chamber and an electrode facing the vibrating plate, and applying ink to the pressurized liquid chamber by deforming the vibrating plate by electrostatic force. 2. Description of the Related Art There is an electrostatic inkjet head that presses and ejects ink droplets from a nozzle.

[0003] In addition to an ink jet head, an electrostatic actuator having a movable portion of a diaphragm is used for a micro electrostatic pump, a micro relay, an optical switch, a micro switch (micro relay), an actuator of a multi-optical lens, and the like. Can be

[0004] As a conventional electrostatic ink jet head, for example, as described in Japanese Patent Application Laid-Open No. 6-71882, a diaphragm forming a wall surface of a liquid chamber and an electrode are arranged in parallel (formed by this). The gap is referred to as a “parallel gap”. As described in JP-A-9-39235, a gap is provided between the diaphragm and the electrode, and the electrode is arranged in a stepwise manner. By changing the gap size in a stepwise manner, or by disposing the electrodes obliquely with respect to the diaphragm as described in JP-A-9-193375, At least part of the cross-sectional shape of the gap between the electrode and the surface (side) on the diaphragm side and the surface (side) on the electrode side is non-parallel (such a gap is referred to as a “non-parallel gap”). )like Also known as the.

In such an electrostatic ink jet head (the same applies to an electrostatic actuator), not only is the gap formed between the diaphragm and the electrode formed with high precision, but also the rigidity of the diaphragm is high. It must be manufactured and maintained with precision. The rigidity of the diaphragm is substantially determined by the Young's modulus of the diaphragm material, the internal stress, and the thickness of the diaphragm, but the influence of the variation in the thickness of the diaphragm is particularly large.

Therefore, in the above-described conventional ink jet head, a boron diffusion layer is formed on a silicon (110) substrate by an alkali etching stop (generally referred to as a boron stop method) in order to manufacture a diaphragm with high precision. A diaphragm made of a boron diffusion layer is formed.

[0007]

However, even if the diaphragm is formed by using the above-described etching stop technique using a boron diffusion layer, a diaphragm having a thickness of about 5 μm or less, more specifically, a thickness of about 2 μm is required. It is not easy to produce at a high yield with a thickness variation of several percent or less.

[0008] When the thickness of the diaphragm varies in the actuator having the diaphragm as described above, for example, in the ink jet head, the ejection characteristics such as the ink droplet ejection volume and the ink droplet velocity vary, and the ink landing position varies. Or the image quality is degraded.

The present inventors have recognized that it is indispensable to study from the viewpoint of "detecting variations and correcting them in a circuit" rather than the conventional viewpoint of simply suppressing variations as much as possible. In order to solve the above-described problems, the present invention provides an electrostatic actuator capable of eliminating a defective actuator, reducing a characteristic variation by setting an appropriate circuit correction value, and improving a yield. An object is to provide an inkjet head.

[0010]

In order to solve the above-mentioned problems, an electrostatic actuator according to the present invention has a closed cavity in which one wall is formed by the same membrane as a diaphragm which becomes a movable portion. It is configured.

Here, the fixed end width of the membrane is preferably defined by the width of the closed space. In addition, it is preferable that the diaphragm and / or a casing forming the diaphragm be formed of a silicon substrate having a (110) plane orientation. Further, it is preferable to provide one or a plurality of closed cavities having different fixed end widths of the membrane.

Further, it is preferable that the width of the housing forming the membrane is the same as the width between the side walls of the drive bit. Furthermore, it is preferable that the sealing pressure in the sealed chamber is lower than 1 atm. In this case, the sealing pressure in the sealed chamber is preferably set to 1/100 atm or less. Furthermore, it is preferable that the gap length of the closed space is substantially equal to or less than the thickness of the membrane.

An ink jet head according to the present invention is provided with the electrostatic actuator according to the present invention.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a first embodiment of the present invention will be described with reference to FIGS. FIG.
Is a schematic top view of the ink jet head according to the embodiment, FIG. 2 is an explanatory cross-sectional view in the longitudinal direction of the diaphragm along the line AA in FIG. 1, and FIG. 3 is a short side of the diaphragm along the line BB in FIG. FIG. 4 is an explanatory cross-sectional view taken along the line CC of FIG. 1 in the transverse direction of the diaphragm.

The ink jet head includes a vibration plate substrate 1, a base substrate 2, and a nozzle plate 4, and a pressurized liquid chamber 6 through which a plurality of nozzles 5 for discharging ink droplets communicate with each other. A common liquid chamber 8 for supplying ink to the liquid chamber 6 via a fluid resistance portion 7 is formed. The ink is supplied from a back surface flow path (ink supply path) 9 formed on the base substrate 2, and the common liquid chamber 8 is formed. The liquid is ejected as droplets from the nozzle 5 through the fluid resistance section 7 and the pressurized liquid chamber 6.

A concave portion serving as a pressurized liquid chamber 6 is provided in the diaphragm substrate 1.
A diaphragm 10 forming the bottom surface which is a wall surface of the pressurized liquid chamber 6, an opening forming the common liquid chamber 8, and the like are provided. The diaphragm substrate 1 is formed from a silicon substrate having a crystal plane orientation (110).

The diaphragm substrate 1 can be formed, for example, using an SOI substrate in which a silicon substrate is bonded via an oxide film. In this case, the concave portion serving as the liquid chamber 6 is KOH
By performing anisotropic etching using an etching solution such as an aqueous solution, the diaphragm 10 can be formed using the oxide film layer as an etch stop layer. That is, the diaphragm substrate 1 is a housing on which the diaphragm 10 is formed.

Further, a high-concentration P-type impurity diffusion layer, for example, a boron diffusion layer is formed on a silicon substrate, and the boron diffusion layer is used as an etching stop layer for an etch stop (hereinafter, referred to as an etch stop).
The diaphragm 10 can be formed with higher precision.

An SOI having an active layer of several μm or less
Substrates are already commercially available, but their specifications are still strict for use in electrostatically driven inkjets. For example, in the case of a substrate having an active layer of 2 μm, the variation specification value is about ± 0.5 μm or less. Of course, this is not the case when the yield cost is not considered. On the other hand, when the boron stop method is used, for example, 2 μm ± 0.1 to 0.2 μm
Control of the degree or less is possible, and at present, the boron stop method is more advantageous as a method for forming a thin film diaphragm with high accuracy.

A thermal oxide film 2a is formed on the base substrate 2 by a thermal oxidation method using a silicon substrate.
a is formed on the diaphragm 10, and a predetermined electrostatic gap 16 is formed on the diaphragm 10 on the bottom surface of the engraved portion 14.
In this case, the opposing electrodes 15 are arranged, and the diaphragm 10 and the electrodes constitute an electrostatic actuator. In addition, a protective insulating film 17 is formed on the surface of the electrode 15, and the electrode 15 extends to an electrode take-out portion (hereinafter, referred to as a PAD contact portion) 18. In addition, a portion between the engraved portions 14 and the like serve as a gap spacer portion for joining to the diaphragm substrate 1.

Here, the electrode 15 is formed of a TiN layer, and the protective insulating film 17 is formed of a plasma oxide film. However, the present invention is not limited to this. A metal material such as Al, Cr, or Ni, or a high-melting point metal such as Ti or W may be used as the protective insulating film 17, and a plasma nitride film, a sputter-based insulating film, or a stacked film thereof may be used. .

In this ink jet head,
In the same manner as the concave portion serving as the pressurized liquid chamber 6, a notch 6m for evaluating the diaphragm rigidity having substantially the same width as the width of the pressurized liquid chamber 6 (width of the side wall of the drive bit) is formed on the diaphragm substrate 1. ing. Further, a sculpture portion 14m for evaluating diaphragm rigidity is formed on the base substrate 2 in the same manner as the sculpture portion 14 of the electrostatic gap. On the upper surface of the carved portion 14m, a membrane 10m equivalent to the diaphragm 10 of the drive bit is arranged. In this way, a closed vacant space 20 which is an evaluation pattern in which one wall surface is formed by the same membrane 10 m as the diaphragm 10 which is a movable portion is formed.

The base substrate 2 has
14g is formed to obtain the potential of the lead electrode, and a lead electrode 15g electrically connected to the base substrate 2 and an insulating protective film 17g thereof are formed in the carved portion 14g.
The electrode 15g extends to the electrode extraction portion 18g of the base substrate 2.

Although the engraved portion 14 of the gap 16 and the like are notably shown in the figure, the actual dimensions are, for example, the thickness of the diaphragm 10 2 μm, the width of the diaphragm 10 125 μm, 800 μm in length, 0.2 μm in depth of electrostatic gap 16, 0.15 μm in thickness of electrode 15
m, the thickness of the protective insulating film 17 of the electrode 15 is 0.2 μm, and the width of the gap spacer (the width of the region directly joined) is 44 μm.
This is quite different from the impression of the figure.

The nozzle plate 4 having the nozzle 5 is formed of a metal layer, a laminated member in which the metal layer and a polymer layer or a resin member are joined, a resin member, nickel electroforming, or the like. . A water-repellent film is formed on the nozzle surface (surface in the discharge direction: discharge surface) by a known method such as a plating film or a water-repellent agent coating in order to ensure water repellency with ink.

Here, the bonding between the diaphragm substrate 1 and the base substrate 2 (more specifically, the insulating film 2a) uses a method of silicon direct bonding (DB: Silicon Direct-Bonding). The bonding between the diaphragm substrate 1 and the nozzle plate 4 is performed using an ink-resistant adhesive.

In the ink-jet head thus configured, the diaphragm 10 is used as a common electrode, and the electrode 15 is used as an individual electrode. The diaphragm 10 is deformed and displaced toward the electrode 15 by the electrostatic force generated between the diaphragm 15 and the electrode 15, and in this state, the electric charge between the diaphragm 10 and the electrode 15 is discharged (the driving voltage is set to 0). 10 is deformed by return, the internal volume (volume) / pressure of the liquid chamber 6 changes, and ink droplets are ejected from the nozzle 5.

Next, a process of manufacturing the ink jet head according to the first embodiment will be described with reference to FIGS. First, as shown in FIG. 5A, a base oxide film 2a for insulating between the base substrate 2 and the electrode 15 serving as an individual electrode is formed. Here, the film thickness is 0.5 to
Although a thermal oxide film of about 2.0 μm was formed, the type of the oxide film is not limited to this. The film thickness is preferably relatively thick in order to reduce the capacitance coupling between the electrodes. However, the film thickness is appropriately set by the capacitance and resistance of each bit, the driver capacitance for driving the bit, and the voltage. It is not limited to.

Next, a contact hole 14ch for obtaining a substrate potential is opened.

Then, as shown in FIG. 2B, the engraved portions 14 for the electrostatic gap are formed on the oxide film 2a.
A carved portion 14m for forming the vacant space 20 serving as an evaluation pattern and a carved portion 14g for taking out a substrate potential are formed. Each of these engraved parts 14, 14m, 14g
Are formed at the same time, the engraving amount is an amount obtained by adding the thickness of the electrode 15 and the thickness of the electrode protection film 17 to the desired electrostatic gap amount.

Next, as shown in FIG. 3C, an electrode 15 made of a TiN film and an electrode protection film 17 made of a plasma oxide film are formed on the oxide film 2a of the base substrate 2. Here, since the oxide film surface 2s is a bonding surface with the diaphragm substrate 1, care is taken not to be exposed to dry etching or the like. Note that the electrode material is not limited to TiN, but is preferably a high-melting-point material because bonding with the diaphragm substrate 1 is performed at a high temperature.

At this time, together with the electrode 15 and the electrode protection film 17, an electrode 15g and an electrode protection film 17g for obtaining a substrate potential are simultaneously formed. Engraved part 14m for evaluation
In the present embodiment, no electrode is formed in the portion of.

Next, as shown in FIG. 2D, the diaphragm substrate 1 having a silicon substrate and a boron diffusion layer 10s having a desired depth formed thereon and the base substrate 2 are bonded by a silicon direct bonding method. Specifically, both substrates are subjected to an ammonia / hydrogen treatment and / or a sulfuric acid / hydrogen treatment (hydrophilization treatment), and are pre-joined under a reduced pressure (vacuum state) within a predetermined time, and are then subjected to a nitrogen (atmospheric pressure) treatment. It is fired at about 700 to 1100 ° C. When pre-joining in the desired manner, even if it is returned to atmospheric pressure during firing,
The above-mentioned engraved parts 14, 14m, 14g do not return to the atmospheric pressure.

Next, as shown in FIG. 6A, an alkali etching mask is formed with a silicon nitride film and alkali etching is performed, and a desired pressurized liquid chamber 6, a carved portion 6m for evaluation, a diaphragm 10, an evaluation plate 10 m of the membrane for use. Here, the crystal plane orientation (11
The silicon substrate of 0) is anisotropically etched with a KOH solution of about 10% to 30% by weight. The mask used for anisotropic etching is low-pressure CVD or plasma C.
A nitride film by VD or a laminated film of an oxide film and the nitride film is formed by patterning by IR alignment.

Thereafter, as shown in FIG. 1B, the nozzle plate 4 is joined onto the diaphragm substrate 1 to obtain a desired ink jet head.

In this case, no electrode and no protective film are formed in the portion where the closed space 20 serving as the evaluation pattern is formed. When an electrode and an electrode protective film are formed, gas is generated from the portion at the time of silicon direct bonding (after pre-bonding), and a desired vacuum state is obtained with good yield in the empty space 20 of the evaluation pattern. It becomes difficult. In order to reduce outgassing, outgassing is performed by baking before pre-joining, but if there is a defect such as a pinhole in the electrode protective film, when the hydrophilic treatment is performed by the WET method as described above In
In some cases, a positive pressure may be rarely generated due to residual moisture in the portion.

Further, since the inside of the vacant space 20 needs to be sealed, it is difficult to pull out the electrodes from the vacant space 20 in this embodiment. In contrast, a third embodiment described below solves these problems.

As described above, in the present embodiment, when forming the electrostatic actuator, the closed vacant space 20 which is a pattern for evaluating the diaphragm rigidity is formed on the head (chip). As described above, the evaluation pattern is such that the inside of the vacant space 20 having the membrane 10 m as a wall is hermetically sealed in a reduced pressure state.

In the case of this embodiment, the pressure during pre-bonding is 1
The pressure is kept at 0-3 Torr or less. Usually, the inside of the vacant room 20 is maintained sufficiently smaller than the atmospheric pressure.
0, just 1 atm is applied to the membrane 10m, and the diaphragm 10 and the membrane 10m are deformed accordingly. By examining the amount of deformation in advance, the rigidity of diaphragm 10 can be easily evaluated optically. The amount of deformation includes the influence of the fixed end width, the pressure, etc., in addition to the thickness of the diaphragm, but this is the most rational evaluation method from the viewpoint of driving the actuator.

In order to make the fixed end width of the membrane 10 m accurate, the engraved portion 6 formed on the diaphragm substrate 1 is formed.
m width, not the engraved part 1 formed on the base substrate 2
It is preferable that the width be 4 m, that is, the width of the vacant space 20. This is because the engraved portion 14m can utilize a highly accurate semiconductor process. When the engraved portion 14m is a fixed end of the membrane 10m, the influence of the angle shift of anisotropic etching appears (the orientation accuracy of a normal wafer is about 1 deg, which is not very good), and various at a laboratory level. Although a suitable accuracy can be obtained by the above method, the variation becomes large in mass production at low cost.

Usually, a silicon substrate having a crystal plane orientation (110) is used as diaphragm substrate 1. The (110) substrate has a Si (111) surface serving as an etching stop surface of a side wall on a surface perpendicular to the substrate surface, so that the chip area can be reduced. Even when the vacant space 20 serving as the evaluation pattern is included, an extra area for the inspection can be suppressed as much as possible.

Next, another example of the second embodiment of the present invention will be described with reference to FIGS. In each of the second embodiments, a plurality of evaluation patterns having different fixed ends of the membrane 10m are provided.

That is, the first example shown in FIG. 7 and FIG.
The plane shape is rectangular and the length (width) in the short direction of the diaphragm
Are arranged in the transverse direction of the diaphragm, and three engraved portions 6m are formed. In the second example shown in FIGS. 9 and 10, the vacancies 20d and 20
e and 20f are arranged in the longitudinal direction of the diaphragm, and one engraved portion 6m is formed.

The third example shown in FIGS. 11 and 12 is as follows.
Vacancies 20 having a circular planar shape and different plane cross-sectional areas
g, 20h and 20i are arranged in the longitudinal direction of the diaphragm, and one engraved portion 6m is formed. In the fourth example shown in FIGS. 13 and 14, one vacant space 20j having a trapezoidal planar shape and a flat cross-sectional area continuously narrowing from one end side to the other end side is formed as a vibration plate longitudinally. Direction, and one engraved part 6m is formed.

In this embodiment, not only can the rigidity of the diaphragm 10 be evaluated more accurately by comparing the amount of deformation of the membrane 10m in each of the cavities 20, but also the amount of deformation can be roughly estimated. The inspection can be completed by evaluating only the presence or absence of deformation without performing measurement.

That is, the fixed end width is set smaller and the rigidity is set higher than that of the drive bit of the present pattern, and it is detected only when the thickness variation of the diaphragm exceeds the allowable range due to the deformation of the evaluation pattern. It is to do. For example, if the diaphragm 10 has a thickness greater than a desired thickness, all the bits are not deformed. If the diaphragm 10 is within a tolerance of a desired thickness, the width of the fixed end is smaller than one. If only the widest bit is deformed and the diaphragm becomes less than the allowable range of the desired thickness, the setting may be made so that all the bits are deformed.

Here, assuming that the above method is used, it is assumed that the diaphragm thickness of the present pattern is equal to the membrane thickness of the evaluation pattern. Normally, the variation of the membrane thickness within one head (chip) is not so remarkable. However, by making the engraved portion 6m of the evaluation pattern the same as the width of the liquid chamber 6 of this pattern, the thickness of the diaphragm is reduced. There is almost no variation. This is because the amount of etching (the thickness of the remaining diaphragm) changes due to the attachment of bubbles during alkali etching, and depends on the width of the liquid chamber. Normally, when the width of the liquid chamber becomes large, air bubbles tend to adhere and the amount of etching decreases (the membrane thickness increases).

The amount of deformation of the membrane is roughly
It is proportional to the membrane pressure (inversely proportional to the cube of the membrane thickness, proportional to the fourth power of the membrane). Therefore, in order to roughly reduce the amount of deformation of the evaluation pattern to about 1% or less, it is preferable to set the internal pressure of the vacant chamber 20 to about 1/100 atmosphere or less.

Further, if the gap (vacant space 20) below the membrane 10m is large, the membrane may be damaged during the manufacturing process. According to the experiment, breakage occurred remarkably at the time of cleaning at the time of chip dicing (shower cleaning from the nozzle). Membrane width 125μm, membrane thickness 2
In the case of μm, breakage was zero when the gap length was 1.2 μm, and about 90% when the gap length was 2.0 μm. Although the details of the damage have not yet been elucidated, these results indicate that
It is preferable to keep the gap length substantially equal to or less than the membrane thickness.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS. FIG. 15 is a schematic top view of the inkjet head according to the same embodiment, and FIG.
6 is an explanatory cross-sectional view in the longitudinal direction of the diaphragm along the line DD in FIG. 15, FIG. 17 is an explanatory cross-sectional view in the lateral direction of the diaphragm along the line EE in FIG. 15, and FIG. FIG. 19 is an explanatory cross-sectional view of the diaphragm along the line F-G along the line F-G in FIG. 15.

In this ink jet head, a thermal oxide film 2a is formed on a base substrate 2 by a thermal oxidation method using a silicon substrate, and an electrode 1 is formed on the oxide film 2a.
5.Evaluation electrode 15m and substrate potential extraction electrode 15
g, a protective insulating film 41 is further formed, and these electrodes 15 and 15g are buried.
In FIG. 1, a carved portion 14 for an electrostatic gap, a carved portion 14m for evaluation, and a carved portion 14g for taking out a substrate potential are formed. Therefore, in this head, the opening of the gap 16 is sealed with the protective insulating film 41 serving as a gap spacer, so that a special sealing step is not required.

Here, the electrode 15 is a polysilicon layer,
The protective insulating film 41 is made of HTO (high-temperature oxide film: High-Temperat).
ure-Oxide) film, and is formed flat at least in a region wider (larger) than the engraved portion 14 for the gap.

The electrode 15 may be made of not only polysilicon but also tungsten silicide, titanium silicide, or a laminated film thereof. As the protective insulating film 41, it is preferable to use a polysilicon oxide film obtained by thermally oxidizing polysilicon or a high-temperature oxide film (HTO) formed by high-temperature thermal CVD.

In addition, examples of the protective insulating film 41 include an LP-CVD nitride film, a plasma oxide film, a plasma nitride film, a sputter-based insulating film, and a laminated film thereof. There are many levels of electron traps inside, and electrical degradation is quicker. In this case, measures are taken to increase the film thickness in order to alleviate the electrical deterioration, but the driving voltage increases because the effective electrostatic gap increases.

In this case, the engraved portion 14 for the electrostatic gap is formed to have a substantially semicircular cross section so that the non-parallel gap 16 is formed.
Is formed, but a parallel gap similar to the above embodiment may be used. Further, a communication passage 42 communicating with the gap 16, a common communication passage 43 communicating with each communication passage 42, and an end 44 of the common communication passage 43 are formed in the insulating protection film 41 of the base substrate 2. At the same time, an atmosphere opening port 45 facing the end 44 of the common communication path 43 is formed, and the gap 16 is formed during the production.
The inside is open to the atmosphere.

With such a configuration, the evaluation electrode 15m can be disposed under the closed space 20, and various inspections can be performed as compared with those of the first embodiment.

As described above, in the case of the present embodiment, the electrostatic gap 16 is decompressed during the manufacturing process. Therefore, in order to return the pressure once to the atmospheric pressure, the communication path 42 and the common communication path 43 are provided, and the membrane of the air opening 45 on the flow path substrate 1 side corresponding to the end 44 of the common communication path 43 is subjected to laser processing or the like. The electrostatic gap 1
6 can be returned to atmospheric pressure. After returning to atmospheric pressure,
Usually, the air opening 45 is sealed again. However, in some cases, the electrostatic gap 16 can be used under reduced pressure without penetrating the air opening 45 once.

In each of the above embodiments, an example in which the electrostatic actuator according to the present invention is applied to an ink jet head has been described. However, the same applies to a microactuator used for a micropump, a micromotor, a microrelay, and the like. can do. Further, the ink jet head may be of an edge shooter type in which the ink droplet ejection direction is a direction orthogonal to the diaphragm displacement direction.

[0059]

As described above, according to the electrostatic actuator of the present invention, the structure is such that the closed vacant space in which one wall surface is formed by the same membrane as the diaphragm as the movable portion is provided. Inspection of diaphragm thickness is possible, and screening and classification (classification according to thickness and its variation), elimination of defective actuators, and reduction of characteristic variations by setting appropriate circuit correction values are possible. Improves the yield.

Here, since the fixed end width of the membrane is defined by the width of the closed space, the fixed end width of the membrane becomes highly accurate, and the inspection accuracy of the diaphragm thickness with high accuracy is improved. In addition, since the diaphragm and / or the housing that forms the diaphragm is formed of a Si substrate having a crystal plane orientation of (110), it is possible to suppress an increase in the size of the head due to the provision of a closed space. Furthermore, the fixed end width of the membrane is different.
Alternatively, by providing a plurality of closed cavities, it is possible to more accurately inspect the diaphragm thickness.

Since the width of the housing forming the membrane is the same as the width between the side walls of the drive bit, the membrane can be made equivalent to the diaphragm. Further, since the sealing pressure in the sealed chamber is lower than 1 atm, the membrane is deformed without taking any special measures. In this case, more preferably, by setting the sealing pressure in the sealed chamber to 1/100 atm or less, highly accurate thickness evaluation becomes possible. Furthermore, since the gap length of the closed space is substantially equal to or less than the thickness of the membrane, breakage of the membrane can be prevented.

According to the ink jet head of the present invention, since the ink jet head includes the electrostatic actuator of the present invention,
The circuit correction for the variation in the diaphragm thickness is facilitated, and the ink droplet ejection characteristics are excellent, and a high-quality image can be recorded.

[Brief description of the drawings]

FIG. 1 is a schematic top view illustrating an example of an electrostatic inkjet head including an electrostatic actuator according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional explanatory view of the head in the longitudinal direction of the diaphragm along the line AA in FIG. 1;

FIG. 3 is a schematic cross-sectional view of the same head taken along line BB in FIG.

FIG. 4 is a schematic cross-sectional explanatory view of the same head taken along the line CC in FIG. 2 in the transverse direction of the diaphragm;

FIG. 5 is an explanatory diagram for explaining a manufacturing process of the head.

FIG. 6 is an explanatory view for explaining a step that follows the step of FIG. 5;

FIG. 7 is a main part top view illustrating a first example of an electrostatic inkjet head including an electrostatic actuator according to a second embodiment of the present invention;

FIG. 8 is an explanatory sectional view of a main part of the first example.

FIG. 9 is a partial top plan view showing a second example of the electrostatic inkjet head including the electrostatic actuator according to the second embodiment of the present invention.

FIG. 10 is an explanatory sectional view of a main part of the second example.

FIG. 11 is an explanatory top view of a main part showing a third example of an electrostatic inkjet head including an electrostatic actuator according to a second embodiment of the present invention;

FIG. 12 is an explanatory sectional view of a main part of the third example.

FIG. 13 is a main part top view illustrating a fourth example of the electrostatic inkjet head including the electrostatic actuator according to the second embodiment of the present invention;

FIG. 14 is an explanatory sectional view of a main part of the fourth example.

FIG. 15 is a schematic top view showing another example of the electrostatic inkjet head including the electrostatic actuator according to the third embodiment of the present invention.

FIG. 16 is a schematic cross-sectional explanatory view of the head in the longitudinal direction of the diaphragm along the line DD in FIG. 15;

FIG. 17 is a schematic cross-sectional explanatory view of the head taken along the line EE in FIG.

FIG. 18 is a schematic cross-sectional view of the head taken along line FF in FIG.

FIG. 19 is a schematic cross-sectional explanatory view of the same head taken along a line GG in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... diaphragm board, 2 ... base substrate, 2a ... oxide film, 5 ...
Nozzle, 6: pressurized liquid chamber, 10: diaphragm, 10m: membrane, 14: engraved portion for electrostatic gap, 14m: engraved portion for evaluation pattern, 15: electrode, 20: closed air chamber.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F04B 53/00 B41J 3/04 103A 53/16 103H 23/06 F04B 21/00 N 43/02 21/08 Z43 / 04 F term (reference) 2C057 AF21 AG54 AG82 AP34 AP82 AQ02 BA04 BA15 3H071 AA05 BB01 CC17 CC31 CC34 CC35 DD04 DD06 EE02 EE08 EE15 3H075 AA07 BB04 BB21 CC30 CC32 CC35 CC36 CC37 DA02 DA03 DA05 DB01 CC02 DD06 EE34 FF06 FF36

Claims (9)

[Claims] 1. An electrostatic actuator that includes a diaphragm serving as a movable portion and an electrode facing the diaphragm, and deforms the diaphragm by electrostatic force. In the electrostatic actuator, one wall is formed by the same membrane as the diaphragm. An electrostatic actuator having a closed vacant space formed therein. 2. The electrostatic actuator according to claim 1, wherein a fixed end width of the membrane is defined by a width of the closed space. 3. The electrostatic actuator according to claim 1, wherein the diaphragm and / or a casing forming the diaphragm are formed of a silicon substrate having a (110) plane orientation. Electrostatic actuator. 4. The electrostatic actuator according to claim 1, wherein one or a plurality of said closed cavities having different fixed end widths of said membrane are provided. . 5. The electrostatic actuator according to claim 1, wherein a width of a housing forming the membrane is the same as a width between side walls of the drive bit. Type actuator. 6. The electrostatic actuator according to claim 1, wherein a sealing pressure in the closed chamber is lower than 1 atm. 7. The electrostatic actuator according to claim 6, wherein a sealing pressure in the closed chamber is 1/100 atm or less. 8. The electrostatic actuator according to claim 1, wherein a gap length of the closed space is substantially equal to or less than a thickness of the membrane. 9. An electrostatic type having a nozzle for ejecting ink droplets, a pressurized liquid chamber communicating with the nozzle, a vibration plate forming a wall surface of the pressurized liquid chamber, and an electrode facing the vibration plate. An inkjet head comprising an actuator, wherein the diaphragm is deformed by electrostatic force to discharge ink droplets from the nozzles, wherein the electrostatic actuator is the electrostatic actuator according to any one of claims 1 to 8. An inkjet head, comprising: