JP4120954B2 - Electrostatic actuator, inkjet head, and image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
  The present invention relates to an electrostatic actuator and an inkjet head., Image forming apparatusAbout.
[0002]
[Prior art]
An ink jet head used in an image recording apparatus such as a printer, a facsimile machine, a copying apparatus, or a plotter, or an ink jet recording apparatus used as an image forming apparatus includes a nozzle that ejects ink droplets and a pressurized liquid chamber (liquid chamber) that communicates with the nozzle. , A pressurizing chamber, a pressure chamber, a discharge chamber, an ink flow path, etc.), a diaphragm that forms a wall surface of the pressurizing liquid chamber, and an electrode facing the diaphragm, There is an electrostatic ink jet head that pressurizes ink in a pressurized liquid chamber and deforms a diaphragm with an electrostatic force to eject ink droplets from a nozzle.
[0003]
In addition to the ink jet head, the electrostatic actuator having a movable part of the diaphragm is used for a micro electrostatic pump, a micro relay, an optical switch, a micro switch (micro relay), an actuator for a multi-optical lens, and the like.
[0004]
As a conventional electrostatic ink-jet head, for example, as described in JP-A-6-71882, a diaphragm that forms the wall surface of a liquid chamber and an electrode are arranged in parallel (the gap formed thereby). As described in Japanese Patent Application Laid-Open No. 9-39235, a gap is provided between the diaphragm and the electrode, and the electrodes are arranged in a staircase shape. The dimension is changed stepwise, or as described in Japanese Patent Application Laid-Open No. 9-193375, the electrodes are arranged obliquely with respect to the diaphragm so that the diaphragm and the electrode The cross-sectional shape of the gap is at least partially non-parallel between the diaphragm side surface (side) and the electrode side surface (side) (such a gap is referred to as a “non-parallel gap”). Also known It has been.
[0005]
In such electrostatic inkjet heads (as well as electrostatic actuators), the gap formed between the diaphragm and the electrode is formed with high precision, and the rigidity of the diaphragm is also manufactured with high precision. • Must be maintained. The rigidity of the diaphragm is almost determined by the Young's modulus, internal stress, and diaphragm thickness of the diaphragm material, but is particularly affected by variations in diaphragm thickness.
[0006]
Therefore, in the conventional ink jet head described above, a boron diffusion layer is formed on a silicon (110) substrate and the boron diffusion layer is formed by alkali etching stop (generally referred to as a boron stop method) in order to produce a diaphragm thickness with high accuracy. The diaphragm which consists of is formed.
[0007]
[Problems to be solved by the invention]
However, even if the diaphragm is formed by using the above-described etching stop technique using the boron diffusion layer, the diaphragm having a thickness of about 5 μm or less, more specifically, a thickness of about 2 μm is high with a thickness variation of several percent or less. It is not easy to produce with yield.
[0008]
When the vibration plate thickness varies in an actuator having a vibration plate in this way, for example, in an ink jet head, there are variations in ejection characteristics such as ink droplet ejection volume and ink droplet velocity, and ink landing positions vary. As a result, the image quality will deteriorate.
[0009]
  The present inventors recognize that it is indispensable to study from the viewpoint of "detecting variations and correcting them in a circuit" rather than simply from the conventional viewpoint of "suppressing variations as much as possible" to complete the present invention. In order to solve the above-described problems, the present invention can eliminate a defective actuator, reduce characteristic variation by setting an appropriate circuit correction value, and improve the yield., Image forming apparatus including the headThe purpose is to provide.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the electrostatic actuator according to the present invention has a sealed vacant space in which one wall surface is formed of the same membrane as a diaphragm serving as a movable part.
[0011]
Here, it is preferable that the fixed end width of the membrane is defined by the width of the sealed vacant chamber. Moreover, it is preferable that the diaphragm and / or the casing forming the diaphragm is formed of a silicon substrate having a (110) plane orientation. Furthermore, it is preferable to provide one or a plurality of sealed vacancies with different fixed end widths of the membrane.
[0012]
Moreover, it is preferable that the width | variety of the housing | casing which forms a membrane is the same as the width | variety between the side walls of a drive bit. Furthermore, it is preferable that the sealing pressure in the sealed vacant chamber is lower than 1 atm. More preferably, the sealed pressure in the sealed vacant chamber is set to 1/100 atm or less. Furthermore, it is preferable that the gap length of the sealed space is substantially equal to or less than the thickness of the membrane.
[0013]
  An ink jet head according to the present invention includes the electrostatic actuator according to the present invention.The image forming apparatus according to the present invention is equipped with the ink jet head according to the present invention.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
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. 1 is a schematic top view of the inkjet head according to the embodiment, FIG. 2 is a cross-sectional explanatory view in the longitudinal direction of the diaphragm along the line AA in FIG. 1, and FIG. 3 is along the line BB in FIG. FIG. 4 is a cross-sectional explanatory diagram of the diaphragm in the lateral direction along the line CC in FIG.
[0015]
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 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 or the like for supplying ink is formed through the fluid resistance portion 7, and the ink is supplied from a back surface flow path (ink supply path) 9 formed in the base substrate 2. It is ejected as a droplet from the nozzle 5 through the part 7 and the pressurized liquid chamber 6.
[0016]
The diaphragm substrate 1 is provided with a concave portion that becomes the pressurized liquid chamber 6, a diaphragm 10 that forms a bottom surface that is a wall surface of the pressurized liquid chamber 6, an opening that forms a common liquid chamber 8, and the like. The diaphragm substrate 1 is formed of a silicon substrate having a crystal plane orientation (110).
[0017]
The diaphragm substrate 1 can be formed using, for example, an SOI substrate in which a silicon substrate is bonded via an oxide film. In this case, the diaphragm 10 can be formed using the oxide film layer as an etch stop layer by anisotropically etching the concave portion serving as the liquid chamber 6 using an etchant such as a KOH aqueous solution. That is, the diaphragm substrate 1 is a housing that forms the diaphragm 10.
[0018]
Further, by forming a high-concentration P-type impurity diffusion layer, for example, a boron diffusion layer on a silicon substrate, and using this boron diffusion layer as an etching stop layer and performing an etch stop (hereinafter referred to as a boron stop), the diaphragm 10 can be made higher. It can be formed with high accuracy.
[0019]
An SOI substrate having an active layer of several μm or less is already on the market, but its specification value is still strict when it is used in an inkjet driven by an electrostatic type. 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, it is possible to control, for example, about 2 μm ± 0.1 to 0.2 μm or less, and at present, the boron stop method is more expensive than the thin film diaphragm. It can be said that it is an advantageous method as a method of forming accurately.
[0020]
A thermal oxide film 2a is formed on the base substrate 2 by a thermal oxidation method using a silicon substrate, an electrostatic gap engraving 14 is formed on the oxide film 2a, and a predetermined portion of the diaphragm 10 is formed on the bottom of the engraved portion 14. Electrodes 15 facing each other with an electrostatic gap 16 are arranged, and the diaphragm 10 and the electrodes constitute an electrostatic actuator. A protective insulating film 17 is formed on the surface of the electrode 15, and the electrode 15 extends to an electrode extraction part (hereinafter referred to as a PAD contact part) 18. A portion between the engraved portions 14 or the like serves as a gap spacer portion for joining to the diaphragm substrate 1.
[0021]
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, and the electrode 15 is gold or Al, which is generally used in a process for forming a semiconductor element. As the protective insulating film 17, a metal material such as Cr, Ni, or a refractory metal such as Ti or W can be used.
[0022]
In this ink jet head, for diaphragm rigidity evaluation having substantially the same width as the width of the pressurizing fluid chamber 6 (the width of the side wall of the drive bit) in the same manner as the concave portion serving as the pressurizing fluid chamber 6 on the diaphragm substrate 1. The engraving portion 6m is formed. Further, the base substrate 2 is formed with a carved portion 14m for diaphragm rigidity evaluation in the same manner as the engraved portion 14 of the electrostatic gap. A membrane 10m equivalent to the diaphragm 10 of the driving bit is disposed on the upper surface of the engraved portion 14m. Thereby, the sealed vacant chamber 20 is formed as an evaluation pattern in which one wall surface is formed of the same membrane 10m as the diaphragm 10 serving as a movable part.
[0023]
Further, a carved portion 14g for taking the potential of the base substrate 2 is formed in the base substrate 2, and an extraction electrode 15g electrically connected to the base substrate 2 and its insulating protective film 17g are formed in the carved portion 14g. The electrode 15 g extends to the electrode extraction portion 18 g of the base substrate 2.
[0024]
In the figure, the engraved portion 14 of the gap 16 is remarkably illustrated, but the actual dimensions are, for example, a thickness of the diaphragm 10 of 2 μm, a width of the diaphragm 10 of 125 μm, and a length of the diaphragm 10 of 800 μm. The depth of the electrostatic gap 16 is 0.2 μm, the thickness of the electrode 15 is 0.15 μm, the thickness of the protective insulating film 17 of the electrode 15 is 0.2 μm, the width of the gap spacer (the width of the region directly bonded) 44 μm, which is quite different from the impression of the figure.
[0025]
The nozzle plate 4 having the nozzles 5 is formed of a metal layer, a laminated member obtained by joining a metal layer and a polymer layer, or a resin member, a resin member, or nickel electroforming. A water repellent film is formed on this nozzle surface (surface in the ejection direction: ejection surface) by a known method such as a plating film or a water repellent coating in order to ensure water repellency with ink.
[0026]
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). The diaphragm substrate 1 and the nozzle plate 4 are joined with an ink-resistant adhesive.
[0027]
In the ink jet head configured as described above, the vibration plate 10 and the electrode 15 are formed by applying a driving voltage between the vibration plate 10 and the electrode 15 using the vibration plate 10 as a common electrode and the electrode 15 as an individual electrode. The diaphragm 10 is deformed and displaced to the electrode 15 side due to the electrostatic force generated during this period, and the diaphragm 10 is restored by discharging the charge between the diaphragm 10 and the electrode 15 from this state (setting the drive voltage to 0). Due to the deformation, the internal volume (volume) / pressure of the liquid chamber 6 changes, and ink droplets are ejected from the nozzle 5.
[0028]
Next, the manufacturing process of the inkjet head according to the first embodiment will be described with reference to FIGS.
First, as shown in FIG. 5A, a base oxide film 2a is formed for insulation between the base substrate 2 and the electrode 15 serving as an individual electrode. Although a thermal oxide film having a thickness of about 0.5 to 2.0 μm is formed here, the type of oxide film is not limited to this. The film thickness is preferably relatively thick in order to reduce capacitive coupling between the electrodes. However, the film thickness is appropriately set according to the capacitance and resistance of each bit, the driver capacity for driving this, and the voltage. It is not limited to.
[0029]
Next, a contact hole 14ch for taking the substrate potential is opened.
[0030]
Then, as shown in FIG. 4B, on the oxide film 2a, an engraved portion 14 for forming an electrostatic gap, an engraved portion 14m for forming a vacant space 20 serving as an evaluation pattern, and a substrate potential extraction. The engraving portion 14g is formed. Since these engraved portions 14, 14 m and 14 g 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 protective film 17 to the desired electrostatic gap amount.
[0031]
Next, as shown in FIG. 2C, an electrode 15 made of a TiN film and an electrode protective 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 serves as a joint surface with the diaphragm substrate 1, consideration is given to prevent exposure to dry etching or the like. The electrode material is not limited to TiN, but a high melting point material is preferable because the electrode material is bonded to the diaphragm substrate 1 at a high temperature.
[0032]
At this time, together with the electrode 15 and the electrode protective film 17, an electrode 15g and an electrode protective film 17g for taking the substrate potential are formed at the same time. In this embodiment, no electrode is formed in the engraved portion 14m for evaluation.
[0033]
Next, as shown in FIG. 4D, the diaphragm substrate 1 having the boron diffusion layer 10s having a desired depth formed on the silicon substrate and the base substrate 2 are bonded by the silicon direct bonding method. Specifically, both substrates are treated with ammonia and / or sulfuric acid (hydrophilic treatment), pre-bonded under reduced pressure (vacuum state) within a predetermined time, and in nitrogen (atmospheric pressure). Firing at about 700 to 1100 ° C. When pre-bonding is performed in a desired manner, the engraved portions 14, 14m, and 14g do not return to atmospheric pressure even when the pressure is returned to atmospheric pressure during firing.
[0034]
Next, as shown in FIG. 6A, an alkali etching mask is formed with a silicon nitride film and alkali etching is performed to obtain a desired pressurized liquid chamber 6, an evaluation engraving portion 6m, a diaphragm 10, and an evaluation membrane 10m. Get. Here, a silicon substrate having a crystal plane orientation (110) is used as the diaphragm substrate 1 and anisotropic etching is performed with a KOH solution of about 10 wt% to 30 wt%. As a mask for anisotropic etching, a nitride film by low pressure CVD or plasma CVD, or a laminated film of an oxide film and the nitride film is formed by patterning by IR alignment.
[0035]
Thereafter, as shown in FIG. 2B, the nozzle plate 4 is bonded onto the diaphragm substrate 1 to obtain a desired ink jet head.
[0036]
Here, the electrode and the protective film are not formed in the portion where the sealed vacant space 20 serving as the evaluation pattern is formed. When the electrode and the electrode protective film are formed, a gas is generated from the portion at the time of direct silicon bonding (after pre-bonding), and the inside of the vacant space 20 of the evaluation pattern is brought into a desired vacuum state with a high yield. It becomes difficult. In order to reduce the outgas, air is burned out before pre-bonding, but if the electrode protective film has defects such as pinholes, when the hydrophilic treatment is performed by the WET method as described above In some cases, moisture may remain in the portion, resulting in a rare positive pressure.
[0037]
Moreover, since it is necessary to make the inside of the empty room 20 sealed, in the case of this embodiment, it is difficult to pull out an electrode from the empty room 20. On the other hand, these are solved in the third embodiment described later.
[0038]
As described above, in the present embodiment, when forming the electrostatic actuator, the sealed vacant space 20 serving as a vibration rigidity evaluation pattern is formed on the head (chip). As described above, the evaluation pattern is such that the interior of the vacant chamber 20 having the membrane 10m as one wall is sealed in a reduced pressure state.
[0039]
In the case of this embodiment, the pressure at the time of prebonding is 10 −3 Torr or less, and normally the inside of the vacant chamber 20 is kept sufficiently smaller than the atmospheric pressure, and the diaphragm 10 and the membrane 10m are just 1 The atmospheric pressure is applied, and the diaphragm 10 and the membrane 10m are deformed accordingly. By examining the amount of deformation in advance, the rigidity of the diaphragm 10 can be easily evaluated optically. The amount of deformation includes the influence of the fixed end width, pressure, etc. in addition to the diaphragm thickness, but is the most rational evaluation method from the viewpoint of driving the actuator.
[0040]
In order to make the fixed end width of the membrane 10 m accurate, not the width of the engraved portion 6 m formed on the diaphragm substrate 1 but the width of the engraved portion 14 m formed on the base substrate 2, that is, the width of the empty chamber 20. It is preferable to specify. This is because the engraved portion 14m can use a highly accurate semiconductor process. When the engraved portion 14m is used as the fixed end of the membrane 10m, the effect of the angular deviation of anisotropic etching occurs (the orientation flat accuracy of a normal wafer is not so good as about 1 deg), and there are various at the laboratory level. With this method, appropriate accuracy can be obtained, but the variation becomes large when mass-producing at low cost.
[0041]
Usually, a silicon substrate having a crystal plane orientation (110) is used as the diaphragm substrate 1. Since the (110) substrate has a Si (111) surface serving as an etching stop surface on the side wall on a surface perpendicular to the substrate surface, the chip area can be reduced. Even in the case where the vacant chamber 20 serving as an evaluation pattern is included, it is possible to suppress an extra region for inspection as much as possible.
[0042]
Next, different examples of the second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, a plurality of evaluation patterns having different fixed ends of the membrane 10m are provided.
[0043]
That is, in the first example shown in FIGS. 7 and 8, the vacant chambers 20a, 20b, and 20c having a rectangular planar shape and different lengths (widths) in the diaphragm lateral direction are arranged in the diaphragm lateral direction. There are three engraved portions 6m. Further, the second example shown in FIG. 9 and FIG. 10 is such that vacant chambers 20d, 20e, and 20f having a rectangular planar shape and different cross-sectional areas are arranged in the longitudinal direction of the diaphragm, and the engraved portion 6m is One is formed.
[0044]
In addition, the third example shown in FIGS. 11 and 12 is an arrangement in which vacant chambers 20g, 20h and 20i having a circular planar shape and different plane cross-sectional areas are arranged in the longitudinal direction of the diaphragm. One is formed. In the fourth example shown in FIGS. 13 and 14, the planar shape is a trapezoidal shape, and one vacant chamber 20j whose planar cross-sectional area continuously narrows from one end side to the other end side has a diaphragm plate length. One engraved portion 6m is formed.
[0045]
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 10 m of each vacant chamber 20, but the amount of deformation can be measured roughly. Instead, the inspection can be completed by evaluating only the presence or absence of deformation.
[0046]
In other words, the fixed end width is set smaller and the rigidity is set higher than that of the drive bit of this pattern, and detection is performed only when the variation in diaphragm thickness exceeds the allowable range due to the presence or absence of deformation of this evaluation pattern. It is. For example, when the vibration plate 10 exceeds the allowable range of the desired thickness, all the bits are not deformed, and when the vibration plate 10 is within the allowable range of the desired thickness, the fixed end width is reduced. When only the widest bit is deformed and the diaphragm is below the allowable range of the desired thickness, all bits may be set to be deformed.
[0047]
Here, it is assumed that the diaphragm thickness of this pattern is equal to the membrane thickness of the evaluation pattern as an assumption to use the above method. Usually, the variation in the thickness of the membrane within one head (chip) is not so remarkable, but by making the engraving portion 6m of the evaluation pattern the same as the width of the liquid chamber 6 of this pattern, There is almost no variation. This is because the etching amount (remaining diaphragm thickness) changes due to the adhesion of bubbles during alkali etching, and depends on the liquid chamber width. Usually, when the liquid chamber width is increased, bubbles are likely to adhere and the etching amount is decreased (membrane thickness is increased).
[0048]
The amount of deformation of the membrane is roughly proportional to the membrane pressure (inversely proportional to the cube of the thickness of the membrane and proportional to the fourth power of the membrane). Therefore, in order to make the deformation amount of the evaluation pattern roughly 1% or less, it is preferable to set the internal pressure of the vacant chamber 20 to 1/100 atmospheres or less.
[0049]
Furthermore, if the gap (vacant space 20) under the membrane 10m is large, the membrane may be damaged during the manufacturing process. According to the experiment, breakage occurred during cleaning during chip dicing (shower cleaning from the nozzle). In the case of a membrane width of 125 μm and a membrane thickness of 2 μm, the breakage was zero when the gap length was 1.2 μm, and the breakage rate was about 90% when the gap length was 2.0 and μm. Although the details of the breakage have not yet been elucidated, it is preferable from these results to keep the gap length below the membrane thickness.
[0050]
Next, a third embodiment of the present invention will be described with reference to FIGS. 15 is a schematic top view of the inkjet head according to the embodiment, FIG. 16 is a cross-sectional explanatory view in the longitudinal direction of the diaphragm along the line DD in FIG. 15, and FIG. 17 is along the line EE in FIG. FIG. 18 is a cross-sectional explanatory view of the diaphragm along the FF line of FIG. 15, FIG. 19 is a cross-sectional explanatory view of the diaphragm along the GG line of FIG. FIG.
[0051]
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 15, an evaluation electrode 15m, and a substrate potential extracting electrode 15g are formed on the oxide film 2a. Further, a protective insulating film 41 is formed to embed these electrodes 15 and 15g. Further, the protective insulating film 41 has an engraved portion 14 for electrostatic gap, an engraved portion 14m for evaluation, and a substrate potential extraction. A carved portion 14g is formed. Therefore, in this head, the opening of the gap 16 is sealed with the protective insulating film 41 serving as a gap spacer, and a special sealing process is not necessary.
[0052]
Here, the electrode 15 is formed of a polysilicon layer and the protective insulating film 41 is formed of an HTO (High-Temperature-Oxide) film, and is flat at least in a region wider (larger) than the engraved portion 14 for the gap. Is formed.
[0053]
The electrode 15 is not limited to polysilicon, but may be 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.
[0054]
In addition, the protective insulating film 41 includes, for example, an LP-CVD nitride film, a plasma oxide film, a plasma nitride film, a sputtered insulating film, or a laminated film thereof. In these insulating films, electrons in the film are included. There are many trap levels and electrical degradation is accelerated. In this case, a means for increasing the film thickness is taken in order to alleviate this electrical degradation, but the drive voltage increases because the electrostatic effective gap increases.
[0055]
Here, the engraved portion 14 for the electrostatic gap is formed in a substantially semicircular cross section to form the non-parallel gap 16, but it may be a parallel gap similar to the above embodiment. Further, the insulating protective film 41 of the base substrate 2 is formed with a communication path 42 communicating with the gap 16, a common communication path 43 communicating with each communication path 42, and an end portion 44 of the common communication path 43. Is formed with an air opening 45 facing the end 44 of the common communication passage 43 so that the inside of the gap 16 can be opened to the atmosphere during the manufacturing process.
[0056]
Since it comprised in this way, it becomes possible to arrange | position the electrode 15m for evaluation also under the sealed space 20, and a various test | inspection is attained compared with that of 1st Embodiment.
[0057]
Further, as described above, in the present embodiment, the electrostatic gap 16 is in a reduced pressure state during the manufacturing process. Therefore, in order to return the pressure to atmospheric pressure once, a communication path 42 and a 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 laser processed or the like. The electrostatic gap 16 can be returned to the atmospheric pressure by penetrating with. After returning to atmospheric pressure, it is normal to seal the air opening 45 again, but in some cases, the electrostatic gap 16 is used under reduced pressure without passing through the air opening 45 once. You can also
[0058]
  In each of the above embodiments, the electrostatic actuator according to the present invention has been described as an example applied to an ink jet head. However, the electrostatic actuator according to the present invention may be similarly applied to a microactuator used for a micropump, a micromotor, a microrelay, or the like. it can. The ink jet head may be of an edge shooter type in which the ink droplet ejection direction is orthogonal to the vibration plate displacement direction.Further, as described above, the present invention can also be applied to an image forming apparatus such as a printer, a facsimile, a copying apparatus, and a plotter, and an apparatus that ejects droplets.
[0059]
【The invention's effect】
As described above, according to the electrostatic actuator according to the present invention, the diaphragm has a sealed vacant space in which one wall surface is formed of the same membrane as the diaphragm serving as the movable part. It is possible to inspect, and screening and classification (classification by thickness and its variation), elimination of defective actuators, and reduction of characteristic variation by setting appropriate circuit correction values, which in turn improves yield. .
[0060]
Here, since the fixed end width of the membrane is defined by the width of the sealed vacant space, the fixed end width of the membrane becomes high accuracy, and the inspection accuracy of the highly accurate diaphragm thickness is improved. In addition, since the diaphragm and / or the casing for forming the diaphragm is formed of a Si substrate having a crystal plane orientation (110), an increase in the size of the head due to the provision of the sealed vacancy can be suppressed. Further, by providing one or a plurality of sealed vacancies with different fixed end widths of the membrane, it is possible to inspect the diaphragm thickness with higher accuracy.
[0061]
Further, since the width of the casing 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. Furthermore, since the sealing pressure in the sealed empty chamber is lower than 1 atm, the membrane is deformed without taking special measures. In this case, more preferably, the thickness can be evaluated with high accuracy by setting the sealing pressure in the sealed empty chamber to 1/100 atm or less. Furthermore, since the gap length of the sealed space is substantially equal to or less than the thickness of the membrane, the membrane can be prevented from being damaged.
[0062]
  According to the ink jet head of the present invention, since the electrostatic actuator according to the present invention is provided, it is easy to correct the circuit with respect to the variation of the diaphragm thickness, and the ink droplet ejection characteristics are excellent, and a high quality image is obtained. It becomes possible to record.According to the image forming apparatus according to the present invention, since the inkjet head according to the present invention is provided, a high-quality image can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic top view illustrating an example of an electrostatic ink jet head including an electrostatic actuator according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional explanatory diagram of the head in the longitudinal direction of the head along the line AA in FIG.
3 is a schematic cross-sectional explanatory diagram of the head in the short direction of the diaphragm along the line BB in FIG. 2;
4 is a schematic cross-sectional explanatory view of the head in the lateral direction of the diaphragm along the line CC in FIG. 2;
FIG. 5 is an explanatory diagram for explaining the manufacturing process of the head.
6 is an explanatory diagram for explaining a process following the process of FIG. 5;
FIG. 7 is a top view of relevant parts showing a first example of an electrostatic inkjet head including an electrostatic actuator according to a second embodiment of the present invention.
FIG. 8 is a cross-sectional explanatory view of the main part of the first example.
FIG. 9 is a top plan view of relevant parts showing a second example of an electrostatic inkjet head including an electrostatic actuator according to a second embodiment of the present invention.
FIG. 10 is a cross-sectional explanatory view of the main part of the second example.
FIG. 11 is a top plan view of relevant parts 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 a cross-sectional explanatory view of the main part of the third example.
FIG. 13 is a top plan view of relevant parts showing a fourth example of an electrostatic inkjet head including an electrostatic actuator according to a second embodiment of the present invention.
FIG. 14 is a cross-sectional explanatory view of an essential part of the fourth example.
FIG. 15 is a schematic top view illustrating another example of an electrostatic inkjet head including an electrostatic actuator according to a third embodiment of the present invention.
16 is a schematic cross-sectional explanatory view in the longitudinal direction of the diaphragm of the head along the line DD in FIG. 15;
17 is a schematic cross-sectional explanatory view of the head in the short direction of the diaphragm along the line EE in FIG. 15;
18 is a schematic cross-sectional explanatory view of the head in the short direction of the diaphragm along the line FF in FIG. 15;
19 is a schematic cross-sectional explanatory view of the head in the short direction of the diaphragm along the line GG in FIG. 15;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Diaphragm board | substrate, 2 ... Base board | substrate, 2a ... Oxide film, 5 ... Nozzle, 6 ... Pressure liquid chamber, 10 ... Vibration board, 10m ... Membrane, 14 ... Engraving part for electrostatic gaps, 14m ... For evaluation patterns Engraved part, 15 ... electrode, 20 ... sealed empty room.

Claims (10)

  In an electrostatic actuator that includes a diaphragm serving as a movable part and an electrode facing the diaphragm, and that deforms the diaphragm with an electrostatic force, a single wall surface is formed of the same membrane as the diaphragm. An electrostatic actuator having a vacant chamber.   2. The electrostatic actuator according to claim 1, wherein a fixed end width of the membrane is defined by a width of the sealed vacant space.   3. The electrostatic actuator according to claim 1, wherein the diaphragm and / or a casing for forming the diaphragm is formed of a silicon substrate having a (110) plane orientation. .   4. The electrostatic actuator according to claim 1, wherein one or a plurality of the sealed vacancies having different fixed end widths of the membrane are provided.   5. The electrostatic actuator according to claim 1, wherein a width of a casing forming the membrane is the same as a width between side walls of the drive bit. 6.   6. The electrostatic actuator according to claim 1, wherein a sealing pressure in the sealed empty chamber is lower than 1 atm.   7. The electrostatic actuator according to claim 6, wherein a sealing pressure in the sealed space is 1/100 atm or less.   8. The electrostatic actuator according to claim 1, wherein a gap length of the sealed space is substantially equal to or less than a thickness of the membrane.   An electrostatic actuator having a nozzle that ejects ink droplets, a pressurized liquid chamber that communicates with the nozzle, a diaphragm that forms a wall surface of the pressurized liquid chamber, and an electrode that faces the diaphragm; The inkjet actuator according to any one of claims 1 to 8, wherein the diaphragm is deformed by an electrostatic force to eject ink droplets from the nozzle. Inkjet head. An image forming apparatus comprising the inkjet head according to claim 9.

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