JP2007160831A - Electrostatic actuator, liquid droplet discharge head and method of manufacturing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic actuator which permits the increasing of driving durability, a liquid droplet discharge head and a method of manufacturing them. <P>SOLUTION: The inkjet head 10 having the electrostatic actuator comprises a vibrating plate 22 as one facing member capable of elastic deformation, a discrete electrode 31 as the other facing member arranged oppositely to the vibrating plate 22 through an insulating film 26 and a fixed space (gap) G, and a driving control circuit (driving means) 4 to generate an static electric power by applying driving voltage between the discrete electrode 31 and the vibrating plate 22. A hydrophobic film 29 is formed on the surface of the insulating film 26 formed on the underside of the vibrating plate 22 by using at least a processing agent to be bonded to at least either a trialkylsilyl group or a dialkylsilyl group by a siloxane bond. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic actuator that is driven by utilizing electrostatic force, a droplet discharge head including the electrostatic actuator, and a method of manufacturing the same.

  2. Description of the Related Art An actuator having a microstructure formed by using a semiconductor microfabrication technique is used in an inkjet head of an inkjet printer. As this micro-structure actuator, an electrostatic drive type using an electrostatic force as a drive source is known (see, for example, Patent Document 1).

An ink jet head provided with an electrostatic actuator is formed as a vibration plate whose bottom surface of an ink chamber communicating with an ink nozzle can be elastically deformed. A substrate is disposed opposite to the diaphragm at a constant interval. A counter electrode is disposed on each of the diaphragm and the substrate, and a space between the counter electrodes is sealed. When a voltage is applied between the opposing electrodes, the bottom surface (vibrating plate) of the ink chamber is vibrated by electrostatic attraction or electrostatic repulsion toward the substrate by electrostatic force generated between them. Ink droplets are ejected from the ink nozzles due to fluctuations in the internal pressure of the ink chamber that occur with the vibration of the bottom surface of the ink chamber. By controlling the voltage applied between the counter electrodes, ink droplets are ejected only when necessary for recording.
Here, when the driving of the ink jet head is repeated by repeatedly applying a voltage between the counter electrodes, a phenomenon in which the electrostatic attraction characteristic or the electrostatic repulsion characteristic deteriorates is observed. In order to avoid such an adverse effect, it is conceivable to hydrophobize the actuator surface.

  As the electrostatic actuator subjected to the hydrophobization treatment, techniques disclosed in Patent Documents 2 and 3 are known.

JP-A-5-50601 (FIGS. 1 and 2) Japanese Patent Laid-Open No. 7-13007 (FIGS. 2 and 3) Japanese Patent Laid-Open No. 10-181028 (FIGS. 3 and 4)

In Patent Document 2, by forming an alignment monomolecular layer of perfluorodecanoic acid (PFDA) on the surface of the counter electrode in the micromechanical device that is an electrostatic actuator, these are in a stuck state during driving, etc. I try to prevent it.
In Patent Document 3, a hydrophobic film made of hexamethyldisilazane (HMDS) is formed on the opposing surface of the electrostatic actuator to prevent them from becoming stuck during driving.

  In the future, in consideration of improving the durability of inkjet printers, it is necessary to increase the number of times the actuator is driven. However, the conventional electrostatic actuator has a problem that the driving durability is not sufficient. That is, in the hydrophobization treatment using perfluorodecanoic acid (PFDA), there is a problem in the adhesion strength of the PFDA layer, and the PFDA layer may be peeled off by repeated operation of the actuator. On the other hand, in the hydrophobizing treatment using hexamethyldisilazane (HMDS), the formation of a uniform hydrophobic film is inhibited by the generation of ammonia gas in the minute gap between the counter electrodes in the hydrophobizing treatment step. There was a fear.

  An object of the present invention is to provide an electrostatic actuator capable of increasing driving durability, a droplet discharge head including the electrostatic actuator, and a method of manufacturing the same.

The present inventors have previously filed an application regarding a hydrophobic film using hexamethyldisilazane (HMDS) as a processing agent, but there is a particular problem in a processing system in which the processing state such as the entire wafer processing tends to be uniform. However, depending on the actuator layout, etc., there was a case where a difference in the driving durability of the actuator was observed. Specifically, in the case of an approach path in which a nano-order fine structure is complicatedly configured as the treatment agent entry path, the actuator is driven in the actuator part near the treatment agent entrance and the actuator part farthest from the entrance. In some cases, there was a difference in durability characteristics.
As a cause of the difference in driving durability due to the layout of this actuator, etc., the present inventors consider that the ammonia gas generated by the reaction of hexamethyldisilazane and the hydroxyl group on the surface of the treated substrate may affect the characteristics. It was.
Ammonia gas generated by the chemical reaction moves by diffusion. Most of the ammonia gas generated at this time is diffused into the processing vessel, but a part is diffused into the processing region deeper than the reaction part. In the region where the concentration of ammonia gas is high, the reaction rate between hexamethyldisilazane and hydroxyl groups is considered to decrease. As a result, processing unevenness is likely to occur, and it is considered that there is a difference in the driving durability of the actuator. Alternatively, it is considered that ammonia gas is physically adsorbed on the treated surface, so that many surfaces that are not hydrophobized with the treating agent are generated, resulting in a difference in the driving durability of the actuator.

Therefore, the present inventor uses a processing agent that can hydrophobize the substrate surface and does not generate ammonia gas even if it reacts with hydroxyl groups on the substrate surface, so that the actuator can be used regardless of the distance from the inlet of the processing agent entry path. As a result, the present inventors have found that there is no difference in driving durability.
That is, the present invention relates to an electrostatic actuator having a relatively displaceable facing member disposed to face each other at a constant interval, and a driving means for generating an electrostatic force between these facing members to relatively displace the facing member. And forming a hydrophobic film on a surface of at least one of the opposing members facing the other member using a treatment agent that binds to at least one of a trialkylsilyl group and a dialkylsilyl group by a siloxane bond. This is an electrostatic actuator.

  By using the treatment agent as described above, ammonia gas is not generated, and a uniform hydrophobic film can be formed on the facing surface of the facing member, thereby improving the driving durability of the electrostatic actuator. it can.

The alkyl group includes a functional group selected from a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.
Since these functional groups do not generate ammonia gas, they can penetrate deeply into a minute gap between the opposing members, and form a uniform hydrophobic film on the opposing surface of the opposing member.

Moreover, it is desirable that at least two alkyl groups among the trialkylsilyl groups are dimethylalkylsilyl groups composed of methyl groups.
If it is a dimethylalkylsilyl group, the treatment agent does not become a bulky alkyl group, and it can penetrate deeply into the minute gap between the opposing members, and form a uniform hydrophobic film on the opposing surface of the opposing member. .

  A droplet discharge head according to the present invention includes any one of the electrostatic actuators described above. Thereby, a droplet discharge head with improved driving durability can be provided.

  The method for manufacturing an electrostatic actuator according to the present invention includes a counter-displaceable counter member arranged to face each other at regular intervals, and a driving unit that generates an electrostatic force between the counter members to relatively displace the counter member. A method of manufacturing an electrostatic actuator comprising: a surface treatment of a facing surface of at least one member of the electrostatic actuator facing the other member with a treatment agent, wherein the treatment agent comprises: And forming a hydrophobic film bonded to the surface with a siloxane bond using a compound having an alkoxyl group and a trialkylsilyl group, or a compound having an alkoxyl group and a dialkylsilyl group after hydroxylating the opposite surface It is characterized by.

  By using the treatment agent as described above, ammonia gas is not generated, a uniform hydrophobic film can be formed on the facing surface of the facing member, and an electrostatic actuator with improved driving durability is manufactured. be able to.

  In the method for producing an electrostatic actuator of the present invention, the alkoxyl group is preferably a methoxy group or an ethoxy group. When the alkoxyl group is a methoxy group, the by-product generated in the hydrophobic reaction is methanol, and when the alkoxyl group is an ethoxy group, the by-product generated in the hydrophobic reaction is methanol. These by-products can be easily removed in a post-processing step described later, and do not interfere with the hydrophobization reaction of the actuator surface and do not adversely affect the actuator characteristics by removing in the post-processing step.

  The method for manufacturing an electrostatic actuator according to the present invention includes a counter-displaceable counter member arranged to face each other at regular intervals, and a driving unit that generates an electrostatic force between the counter members to relatively displace the counter member. A method of manufacturing an electrostatic actuator comprising: a surface treatment of a facing surface of at least one member of the electrostatic actuator facing the other member with a treatment agent, wherein the treatment agent comprises: After the hydroxylation of the opposing surface, a hydrophobic film bonded to the surface with a siloxane bond is formed using a compound having a hydroxyl group and a trialkylsilyl group.

  Even when a treating agent made of a compound having a hydroxyl group and a trialkylsilyl group is used, a uniform hydrophobic film can be formed, and an electrostatic actuator having excellent driving durability can be manufactured.

  The alkyl group includes a functional group selected from a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. By constituting the alkyl group with a group having a small number of carbon atoms, it is possible to form a treated surface having a sufficiently low surface energy because it has a sufficient hydrophobizing ability and has little treatment unevenness.

Moreover, it is desirable that at least two alkyl groups among the trialkylsilyl groups are dimethylalkylsilyl groups composed of methyl groups.
If it is a dimethylalkylsilyl group, the treatment agent does not become a bulky alkyl group, and it can penetrate deeply into the minute gap between the opposing members, and form a uniform hydrophobic film on the opposing surface of the opposing member. .

Moreover, it is desirable to include a pretreatment step for removing moisture adhering to the facing surface prior to the surface treatment step for the facing surface.
By this pretreatment step, moisture adhering to the facing surface can be removed prior to the surface treatment step, so that the adhesion state of the treatment agent can be stabilized. Furthermore, the pretreatment step is preferably a vacuum heating step in which the inside of the treatment tank containing the workpiece is evacuated and heated.

  In addition, after the surface treatment step of the facing surface, a post-treatment step of removing by-products formed on the facing surface is included.

  Since the treating agent used in the present invention generates alcohol or water as a by-product, it is necessary to perform a post-treatment in order to remove these by-products. In this case, it is desirable that the post-treatment process is a vacuum heating process in which the inside of the treatment tank containing the workpiece is evacuated and heated.

A method for manufacturing a droplet discharge head according to the present invention is a method for manufacturing a droplet discharge head using any one of the above-described electrostatic actuator manufacturing methods.
As a result, it is possible to provide a liquid droplet ejection head such as an ink jet head having a high driving durability.

A method for manufacturing a droplet discharge head according to the present invention is a method for manufacturing a droplet discharge head using any one of the above-described electrostatic actuator manufacturing methods.
As a result, it is possible to provide a liquid droplet ejection head such as an ink jet head having a high driving durability.

  Hereinafter, embodiments of a droplet discharge head including an electrostatic actuator according to the present invention will be described with reference to the drawings. Here, as an example of a droplet discharge head, a face discharge type inkjet head that discharges ink droplets from ink nozzles provided on the surface of a nozzle substrate will be described with reference to FIGS. The present invention is not limited to the structure and shape shown in the following drawings, and can also be applied to an edge discharge type inkjet head that discharges ink droplets from ink nozzles provided at the end of a substrate. It is.

  FIG. 1 is an exploded perspective view showing an exploded schematic configuration of the ink jet head according to the present embodiment, and a part thereof is shown in cross section. FIG. 2 is a cross-sectional view of the ink jet head showing a schematic configuration in an assembled state. FIG. 3 is an enlarged sectional view in the longitudinal direction of the electrostatic actuator portion in this ink jet head, and FIG. 4 is an enlarged sectional view in the width direction of the electrostatic actuator portion. 1 and 2 are shown upside down from a state in which they are normally used.

  As shown in FIGS. 1 and 2, an inkjet head (an example of a droplet discharge head) 10 according to the present embodiment includes a nozzle substrate 1 having a plurality of ink nozzles (nozzle holes) 11 provided at a predetermined pitch, The cavity substrate 2 in which an ink supply path is provided independently of the ink nozzle 11 and the electrode substrate 3 on which the individual electrode 31 is disposed facing the vibration plate 22 of the cavity substrate 2 are bonded together. ing.

The electrostatic actuator in the present embodiment includes the diaphragm 22 that is one opposing member that can be elastically deformed, and the other that is disposed to face the diaphragm 22 via an insulating film 26 and a certain gap (gap) G. The above-mentioned individual electrodes 31 that are opposing members, and a drive control circuit (driving means) 4 that generates a static force by applying a driving voltage between the individual electrodes 31 and the diaphragm 22 are further provided. As shown, a hydrophobic film 29 is formed on the surface of the insulating film 26 formed on the lower surface of the diaphragm 22 using the treatment agent of the present invention.
Hereinafter, the configuration of each substrate constituting the inkjet head 10 will be described.

The nozzle substrate 1 is made of, for example, a silicon substrate having a thickness of 100 μm, and a plurality of ink nozzles 11 are formed. As shown in FIG. 2, each ink nozzle 11 has a cylindrical ejection port portion 11a perpendicular to the surface of the nozzle substrate 1, and is provided coaxially with the ejection port portion 11a and has a diameter larger than that of the ejection port portion 11a. An inlet part 11b having a large (or cross-sectional area) is provided. Thus, by making the ink nozzle 11 have a two-stage hole, the ink droplet ejection direction can be aligned with the central axis direction of the ink nozzle 11, and stable ink ejection characteristics can be exhibited. . That is, there is no variation in the flying direction of the ink droplets, there is no scattering of the ink droplets, and variations in the ejection amount of the ink droplets can be suppressed.
Further, in FIG. 2 of the nozzle substrate 1, a narrow groove-like orifice 13 that forms a part of the ink flow path is provided on the lower surface (the surface on the bonding side with the cavity substrate 2).

  The cavity substrate 2 is made of, for example, a silicon substrate having a thickness of 140 μm. By performing anisotropic wet etching on the silicon substrate, recesses 24 and 25 for forming the ink chamber (discharge chamber) 21 and the reservoir 23 of the ink flow path are formed. A plurality of recesses 24 are independently formed at positions corresponding to the ink nozzles 11. Therefore, when the nozzle substrate 1 and the cavity substrate 2 are joined as shown in FIG. 2, each concave portion 24 constitutes an ink chamber 21 and communicates with the ink nozzle 11 respectively, and the orifice 13 serving as an ink supply port. Both communicate with each other. The bottom wall of the ink chamber 21 (recess 24) serves as the diaphragm 22. The diaphragm 22 can also be constituted by a boron-doped layer formed by diffusing high-concentration boron in a silicon substrate with a required thickness. By configuring the diaphragm with a boron-doped layer, the etching stop sufficiently works on the surface of the boron-doped layer, so that the surface roughness of the diaphragm can be suppressed and the thickness thereof can be processed with high accuracy.

  The other concave portion 25 is for storing liquid material ink, and constitutes a common reservoir (common ink chamber) 23 for each ink chamber 21. The reservoirs 23 (recesses 25) communicate with all the ink chambers 21 through the orifices 13, respectively. Further, a hole penetrating the electrode substrate 3 described later is provided in the bottom of the reservoir 23, and ink is supplied from an ink cartridge (not shown) through the ink supply hole 34 of the hole.

An insulating film made of SiO ₂ or TEOS (Tetraethylorthosilicate Tetraethoxysilane) is formed on the entire surface of the cavity substrate 2 or at least the surface facing the electrode substrate 3 by thermal oxidation or plasma CVD (Chemical Vapor Deposition). 26 is applied with a film thickness of 0.1 μm. This insulating film 26 is provided for the purpose of preventing dielectric breakdown and short circuit when the ink jet head is driven. Further, on the surface of the insulating film 26, as will be described later, a hydrophobic film 29 surface-treated with the treating agent of the present invention is formed.
On the upper surface of the cavity substrate 2, that is, the surface facing the nozzle plate 1 (including the inner surfaces of the ink chamber 21 and the reservoir 23), an ink protection film (not shown) is similarly formed of a SiO ₂ film (including a TEOS film). This ink protective film is provided to prevent corrosion of the flow path by ink.

  The electrode substrate 3 is made from a glass substrate having a thickness of about 1 mm, for example. Among them, it is suitable to use a borosilicate heat-resistant hard glass having a thermal expansion coefficient close to that of the silicon substrate of the cavity substrate 2. This is because when the electrode substrate 3 and the cavity substrate 2 are anodically bonded, the thermal expansion coefficients of the two substrates are close to each other, so that the stress generated between the electrode substrate 3 and the cavity substrate 2 can be reduced. This is because the electrode substrate 3 and the cavity substrate 2 can be firmly bonded without causing the above problem. The electrode substrate 3 may be a silicon substrate made of the same material as the cavity substrate 2.

  The electrode substrate 3 is provided with a recess 32 at a position on the surface of the cavity substrate 2 facing each diaphragm 22. The recess 32 is formed to a depth of about 0.2 μm by etching. In each recess 32, an individual electrode 31 made of, for example, ITO (Indium Tin Oxide) is formed by sputtering with a thickness of, for example, 0.1 μm. Therefore, the gap (gap) G formed between the diaphragm 22 and the individual electrode 31 is determined by the depth of the recess 32 and the thickness of the insulating film 26 covering the individual electrode 31 and the diaphragm 22. . This gap G greatly affects the ejection characteristics of the inkjet head. In the above example, the gap G between the insulating film 26 on the lower surface of the diaphragm 22 and the individual electrode 31 after the cavity substrate 2 and the electrode substrate 3 are joined is 0.1 μm. The open end of the gap G is hermetically sealed by filling a sealing through hole 28 provided at the rear end of the cavity substrate 2 with a sealing material 27 made of, for example, TEOS or epoxy adhesive. The Thereby, moisture, dust and the like can be prevented from entering the gap, and the reliability of the inkjet head 10 can be kept high.

  The individual electrode 31 has a lead part 31a and a terminal part 31b connected to a flexible wiring board (not shown). The terminal portion 31b is exposed in the electrode extraction portion 35 in which the rear end portion of the cavity substrate 2 is opened in order to facilitate connection of the flexible wiring board.

  Here, the diaphragm 22 formed by the bottom wall of each ink chamber 21 functions as a common electrode on each ink chamber side. As shown in FIGS. 3 and 4, the surface of the insulating film 26 formed on the lower surface of the diaphragm 22 is subjected to surface treatment with the treatment agent of the present invention to form a hydrophobic film 29. Individual electrodes 31 made of ITO are formed on the concave surface of the electrode substrate 3 so as to face the diaphragm 22 as the common electrode. The counter electrode of the electrostatic actuator is formed by the diaphragm 22 on the bottom wall of each ink chamber, which is a common electrode, and the individual electrodes 31 corresponding to the insulating film 26 and the gap G.

As described above, the nozzle substrate 1, the cavity substrate 2, and the electrode substrate 3 are bonded to each other as shown in FIG. That is, the cavity substrate 2 and the electrode substrate 3 are generally bonded by anodic bonding, and the nozzle substrate 1 is bonded to the upper surface (the upper surface in FIG. 2) of the cavity substrate 2 by adhesion or the like.
Finally, as shown in a simplified manner in FIGS. 1 and 2, a drive control circuit (drive means) 4 such as a driver IC is provided on the terminal portion 31 b of each individual electrode 31 and the common electrode (on the cavity substrate 2). The flexible wiring board (not shown) is connected to the terminal (not shown).
Thus, the ink jet head 10 is completed.

Next, the operation of the inkjet head 10 configured as described above will be described.
The drive control circuit 4 is an oscillation circuit that controls the supply and stop of charges to the individual electrodes 31. This oscillation circuit oscillates at, for example, 24 kHz, and supplies electric charges by applying pulse potentials of, for example, 0 V and 30 V to the individual electrodes 31. When the oscillation circuit is driven and charges are supplied to the individual electrode 31 to be positively charged, an electrostatic force (Coulomb force) is generated between the individual electrode 31 and the diaphragm 22. Therefore, the diaphragm 22 is attracted to the individual electrode 31 by this electrostatic force and bends (displaces). As a result, the volume of the ink chamber 21 increases. When the supply of electric charges to the individual electrodes 31 is stopped, the diaphragm 22 returns to its original state due to its elastic force, and at this time, the volume of the ink chamber 21 is rapidly reduced. Part of the ink is ejected from the ink nozzle 11 as ink droplets. Next, when the vibration plate 22 is similarly displaced, ink is supplied from the reservoir 23 through the orifice 13 into the ink chamber 21.
The ink used in the inkjet head 10 is prepared by dissolving or dispersing a surfactant such as ethylene glycol and a dye or pigment in a main solvent such as water or alcohol.

  Next, with reference to FIG. 5, the manufacturing method of the inkjet head 10 provided with the electrostatic actuator of this embodiment is demonstrated.

FIG. 5 is a schematic flowchart showing an outline of the manufacturing process of the inkjet head 10. As shown in this figure, first, in step S1, the nozzle substrate 1, the cavity substrate 2, and the electrode substrate 3 constituting the inkjet head 10 are each processed from a wafer and manufactured.
Next, in step S2, as shown in FIG. 6, the wafer assembly having a large number of ink-jet heads 10 (referred to here as the main body of the ink-jet head 10) is formed by bonding the three-member wafers to each other. 100 is formed. That is, the electrode substrate 3 is bonded to the bottom surface side of the cavity substrate 2 by anodic bonding so that the gap G is formed. Then, the nozzle substrate 1 is bonded and bonded to the upper surface of the cavity substrate 2 with an adhesive. Note that the inkjet head 10 in the wafer assembly 100 has an electrode extraction portion 35 formed by etching at the rear end of the cavity substrate 2 as described above. Processing is performed.

Next, in the pretreatment step of Step S3, the surface to be processed (the inner surface of the gap G) of the inkjet head 10 is dried. That is, in this step, moisture adhering to the surface to be processed of the wafer assembly (object to be processed) 100 is removed. For example, using a processing apparatus as shown in FIG. 7, the wafer assembly 100 is placed in the processing tank 201, for example, nitrogen is used as an inert gas, and the nitrogen introduction valve 202 is opened to supply nitrogen from the nitrogen introduction port. The exhaust valve 203 may be opened at the same time as supplying into the processing tank 201 to replace the inside of the processing tank 201 with a nitrogen gas atmosphere. At this time, the inside of the electrostatic actuator, that is, the gap G is similarly replaced with the nitrogen gas atmosphere. When such a pretreatment process is performed, the surface treatment state of the surface to be treated can be stabilized. In other words, it is possible to remove the adhering moisture from the surface of the insulating film 26 formed on the lower surface of the vibration plate 22 and avoid the occurrence of variations in the state of adhesion of the processing agent in the next step. In FIG. 7, reference numeral 204 denotes a heater.
Further, in this pretreatment step, vacuum heat treatment can be employed in order to remove moisture adhering to the surface to be treated. The conditions of the vacuum heat treatment are, for example, that the treatment tank 201 containing the wafer assembly 100 of the inkjet head is held at a temperature of 340 ° C. and a vacuum degree of 10 ⁻³ Torr for 9 minutes, and then held in a nitrogen gas atmosphere for 1 minute. This cycle is repeated for a total of 12 cycles.

  Next, in the surface treatment process of step S4, a hydrophobic film 29 as schematically shown in FIG. 8 is formed on the surface of the insulating film. In the present invention, as the treating agent, a functional group for reacting with the insulating film surface, specifically an alkoxyl group or a hydroxyl group, and a functional group for reducing the surface energy of the insulating film surface, specifically an alkyl group. A compound having both groups is used. The alkoxyl group and the hydroxyl group are highly reactive with the surface of the insulating film that has been subjected to hydrophilic treatment, and the entire surface of the insulating film surface of the actuator portion can be uniformly surface-treated.

  There are many compounds having an alkoxyl group or a hydroxyl group and an alkyl group in the chemical structure, but in the present invention, a trialkylalkoxysilyl compound comprising one alkoxyl group, three alkyl groups and one silicon atom, Alternatively, it is desirable to use a dialkyl dialkoxysilyl compound composed of two alkoxyl groups, two alkyl groups, and one silicon atom. It is also possible to use a trialkylalkoxysilanol compound composed of one hydroxyl group, three alkyl groups and one silicon atom.

Here, it is desirable that the alkyl group contains a fluorinated alkyl group in which hydrogen of the alkyl group is substituted with fluorine. Since the fluorinated alkyl group has a smaller surface energy than the alkyl group, the driving durability of the actuator is further improved.
Moreover, it is desirable that at least two alkyl groups among the trialkylsilyl groups are dimethylalkylsilyl groups composed of methyl groups. This is because when the treatment agent is composed of a bulky alkyl group, depending on the type of the alkyl group, the entire surface of the insulating film in the actuator portion is hardly uniformly treated, and the driving durability of the actuator is not improved. If it is a dimethylalkylsilyl group, such a problem does not arise.

  In addition, the surface treatment can be either a liquid phase treatment or a vapor phase treatment, but it is desirable to use a vapor phase treatment that can easily obtain a uniform treatment surface. In the present embodiment, by a vapor phase process, a 7 L processing tank and a 4-inch wafer assembly are reacted with 300 μL of a processing agent, that is, a trialkylalkoxysilyl compound trimethylmethoxysilane shown below at room temperature for 30 hours. As a result, the hydrophobic film 29 was formed on the bottom surface of the insulating film 26. In the gas phase treatment, it is necessary that the vapor pressure of the treatment agent is an appropriate value. Accordingly, among the treating agents represented by the above general formula, a compound having a relatively low vapor pressure at room temperature, specifically, a compound having 4 or less carbon atoms constituting one alkyl group of the treating agent is used. Is desirable.

  In the case of the treatment agent used in the present invention, alcohol is generated when the alkoxyl group and the hydroxyl group on the surface of the insulating film react, and water is generated when the hydroxyl group of the treatment agent and the hydroxyl group on the surface of the insulating film react. If these by-products adhere to the surface of the insulating film of the actuator part, it causes sticking of the actuator. Therefore, in the manufacturing method of this embodiment, the post-processing process which removes the alcohol and water which generate | occur | produce in a surface treatment process is needed. Although the post-treatment process will be described later, it is desirable to use a lower alkoxide, preferably a linear alkoxide having 3 or less carbon atoms, from which the generated alcohol can be easily removed.

As specific treatment agents satisfying the above conditions, the following compounds are commercially available, and an appropriate one may be selected and used.
<Trialkylalkoxysilyl compound>
* Trimethylmethoxysilane
* Trimethylethoxysilane
* (3,3,3-trifluoropropyl) dimethylmethoxysilane
* N-propyldimethylmethoxysilane
* N-butyldimethylmethoxysilane
<Dialkyl dialkoxysilyl compound>
* Dimethyldimethoxysilane
* Dimethyldiethoxysilane
* Diethyldiethoxysilane
* Di-n-bytyldimethoxysilane
* Isobutylmethyldimethoxysilane
<Trialkylalkoxysilanol compound>
* Trietylsilanol
* T-butyldimethylsilanol

Next, in the post-treatment process in step S5, the lower alcohol and water generated in the surface treatment process are surely removed.
The post-processing step is not particularly limited as long as it is a method capable of removing the by-product lower alcohol and water. For example, after the surface treatment, the wafer assembly 100 of the inkjet head 10 is vacuumed, preferably heated vacuum. A method of placing and removing alcohol or water is desirable. Further, in order to prevent moisture in the air from entering in the next hermetic sealing process, it is desirable to replace the inside of the actuator with nitrogen by replacing the inside of the treatment tank with nitrogen after the post-treatment process.

  Next, in the hermetic sealing process of step S 6, the wafer assembly of the inkjet head 10 is taken out from the treatment tank replaced with nitrogen, and the space between the insulating film 26 and the individual electrode 31 is sealed with the sealing agent 27. Seal hermetically. Thereby, a predetermined sealed gap G is formed, and an electrostatic actuator is formed. Then, the inkjet head 10 is completed by cutting the wafer assembly 100 into individual heads by dicing.

  As described above, according to the method of manufacturing the ink jet head of the present embodiment, by using the processing agent described above, the surface of the insulating film 26 is deeply formed on the surface of the insulating film 26 without generating ammonia gas. A uniform hydrophobic film 29 can be formed, and the driving durability of the actuator can be improved.

In the above embodiment, the electrostatic actuator, the inkjet head, and the manufacturing method thereof have been described. However, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the idea of the present invention. it can. For example, by changing the liquid material ejected from the ink nozzles, in addition to inkjet printers, the production of color filters for liquid crystal displays, the formation of light-emitting portions of organic EL display devices, the microarray of biomolecule solutions used for genetic testing, etc. It can be used as a droplet discharge device for various uses such as manufacture of
In addition, although the vibration plate has been described as a thin plate type in which both ends are supported or a substantially rectangular whole circumference is fixed, a cantilever type may be used. Further, the shape of the diaphragm is not particularly limited. For example, it may be circular, and an electrostatic actuator having a circular diaphragm can be used, for example, in a diaphragm portion of a micropump.

1 is an exploded perspective view showing a schematic configuration of an ink jet head provided with an electrostatic actuator of the present invention. FIG. 2 is a schematic cross-sectional view showing an assembled state of the inkjet head of FIG. 1. FIG. 3 is an enlarged cross-sectional view in the longitudinal direction of an electrostatic actuator portion in the inkjet head of FIG. 2. The expanded sectional view of the width direction of the electrostatic actuator part of FIG. FIG. 3 is a schematic flowchart of a manufacturing process showing an example of a method for manufacturing the ink jet head of FIG. 2. The fragmentary sectional view of a wafer assembly. BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the processing apparatus used in this invention. The schematic diagram which shows the hydrophobic film | membrane formed with the processing agent of this invention.

Explanation of symbols

1 nozzle substrate, 2 cavity substrate, 3 electrode substrate, 4 drive control circuit (drive means), 10 ink jet head, 11 ink nozzle, 13 orifice, 21 ink chamber, 22 vibration plate, 23 reservoir, 26 insulating film, 27 sealing Material, 28 sealing through-hole, 29 hydrophobic membrane, 31 individual electrode, 32 recess, 34 ink supply hole, 35 electrode take-out part, 100 wafer assembly, 201 processing tank.

Claims (14)

In an electrostatic actuator having a relatively displaceable facing member arranged to face each other at a fixed interval, and a driving unit that generates an electrostatic force between these facing members to relatively displace the facing member.
A hydrophobic film is formed on a surface of at least one of the facing members facing the other member using a treatment agent that binds to at least one of a trialkylsilyl group and a dialkylsilyl group by a siloxane bond. An electrostatic actuator characterized by   The electrostatic actuator according to claim 1, wherein the alkyl group includes a functional group selected from a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.   3. The electrostatic actuator according to claim 1, wherein at least two alkyl groups among the trialkylsilyl groups are dimethylalkylsilyl groups composed of methyl groups.   A droplet discharge head comprising the electrostatic actuator according to claim 1.   A method of manufacturing an electrostatic actuator comprising: a relatively displaceable facing member disposed facing each other at a fixed interval; and a driving unit that generates an electrostatic force between the facing members to relatively displace the facing member. And a step of treating the surface of at least one of the opposing members of the electrostatic actuator facing the other member with a treatment agent, and after treating the opposite surface with hydroxyl as the treatment agent, an alkoxyl group And a compound having a trialkylsilyl group, or a compound having an alkoxyl group and a dialkylsilyl group, and forming a hydrophobic film bonded to the surface with a siloxane bond.   6. The method for producing an electrostatic actuator according to claim 5, wherein the alkoxyl group is a methoxy group or an ethoxy group.   A method of manufacturing an electrostatic actuator comprising: a relatively displaceable facing member disposed facing each other at a fixed interval; and a driving unit that generates an electrostatic force between the facing members to relatively displace the facing member. And a surface treatment of at least one of the opposing members of the electrostatic actuator facing the other member with a treatment agent, and the treatment agent is hydroxylated after hydroxylating the opposite surface. And a compound having a trialkylsilyl group, and forming a hydrophobic film bonded to the surface with a siloxane bond.   The method for producing an electrostatic actuator according to claim 5, wherein the alkyl group includes a functional group selected from a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.   9. The method for manufacturing an electrostatic actuator according to claim 5, wherein at least two alkyl groups among the trialkylsilyl groups are dimethylalkylsilyl groups composed of methyl groups.   The method for manufacturing an electrostatic actuator according to claim 5, further comprising a pretreatment step of removing moisture attached to the facing surface prior to the surface treatment step of the facing surface.   The method of manufacturing an electrostatic actuator according to claim 10, wherein the pretreatment step is a vacuum heating step in which the inside of the treatment tank containing the workpiece is evacuated and heated.   The method for manufacturing an electrostatic actuator according to claim 5, further comprising a post-processing step of removing a byproduct formed on the facing surface after the surface-treating step of the facing surface.   13. The method for manufacturing an electrostatic actuator according to claim 12, wherein the post-processing step is a vacuum heating step in which the inside of the processing tank containing the workpiece is evacuated and heated. A method for manufacturing a droplet discharge head, wherein the droplet discharge head is manufactured using the method for manufacturing an electrostatic actuator according to claim 5.

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