JPH11179919A - Electrostatic actuator and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrostatic actuator having facing members being displaced relatively with electrostatic force in which the process for sealing the facing members hermetically is facilitated by forming a hydrophobic film for preventing adhesion of the facing members and then sustaining the concentration of a compound for forming the hydrophobic film between the facing members at a specified level or above. SOLUTION: An oscillation room 15 including the surface of the bottom wall (common electrode) of the ink room in an ink jet head employing an electrostatic actuator and the surface of a segment electrode 17 is coupled with a tube 15b for external connection, and the tube 15b communicates with the outside through a by-pass tube 15c. After the open end of the tube 15b is sealed with a sealant 20a, a compound for forming a hydrophobic film is injected into a processing tank through the by-pass tube 15c. Subsequently, the by-pass tube 15c is sealed with a sealant 20b on the outside of the processing tank thus sealing the oscillation room 15 hermetically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrostatic actuator which uses an electrostatic force generated by applying a voltage between opposed electrodes as a driving source.
More specifically, the present invention relates to a method of forming a hydrophobic film in an electrostatic actuator having a hydrophobic film on a surface of a member relatively displaced by an electrostatic force.

[0002]

2. Description of the Related Art A microstructured actuator formed by using a semiconductor fine processing technique is used in an ink jet head or the like of an ink jet printer. As an actuator having such a minute structure, an actuator of an electrostatic drive system using an electrostatic force as a drive source is known. For example, the applicant of the present invention has disclosed in Japanese Patent Application Laid-Open Nos. 5-50601 and 6-70882 a type of ink jet head that discharges ink droplets by using electrostatic force.

In this type of ink jet head, the bottom surface of an ink chamber communicating with an ink nozzle is formed as an elastically deformable diaphragm. Substrates are arranged facing the diaphragm at regular intervals. Opposing electrodes are respectively arranged on the diaphragm and the substrate, and the space between these opposing electrodes is in a sealed state. When a voltage is applied between the opposing electrodes, the bottom surface (vibration plate) of the ink chamber is electrostatically attracted or repelled toward the substrate by the electrostatic force generated between them, and vibrates. Ink droplets are ejected from the ink nozzles due to fluctuations in the internal pressure of the ink chamber caused by the vibration of the bottom surface of the ink chamber. By controlling the voltage applied between the opposing electrodes, the ink droplets are ejected only when necessary for recording, a so-called ink-on-
The demand method is realized.

Here, when water adheres to the surface of the counter electrode, that is, the bottom surface of the ink chamber and the surface of the substrate facing each other, while the inkjet head is driven by repeatedly applying a voltage between the counter electrodes, Due to the charging of these polar molecules, the electrostatic attraction characteristics or the electrostatic repulsion characteristics may be reduced. In addition, the polar molecules adsorbed on the surface of the substrate may form hydrogen bonds with each other, and the bottom surface of the ink chamber may remain stuck to the substrate side (sticking state), which may render the operation inoperable.

In order to avoid such adverse effects, it is conceivable to perform a hydrophobic treatment on the bottom surface of the ink chamber and the substrate surface. For example, it is conceivable to make these surfaces hydrophobic by forming an oriented monomolecular layer of perfluorodecanoic acid (PFDA) on these surfaces.

An example of an electrostatic actuator that has been subjected to a hydrophobizing treatment using PFDA is disclosed in, for example, JP-A-7-130.
No. 07, US Pat. No. 5,331,454. In these publications, by forming an oriented monomolecular layer of PFDA on the surface of a counter electrode in a micro-mechanical device which is an electrostatic actuator, it is intended to prevent these from falling into a stuck state during driving. I have.

[0007]

In addition to the hydrophobization treatment using PFDA, the present inventors have proposed HMDS (hexamethyldisilazane, (CH ₃ ) ₃ SiNHSi (C
It has been proposed to perform a hydrophobic treatment using H ₃ ) ₃ ). That is, it has been proposed to improve the durability of the electrostatic actuator by hermetically sealing a compound for forming a hydrophobic film in a space between the opposed electrodes.

According to the findings of the present inventors, it has been found that the durability of the actuator is closely related to the concentration of the compound hermetically sealed in the actuator. Specifically, the present inventors have a hydrophobic group on the facing surface,
The durability of the hydrophobic film when left outside (in air) immediately after attaching a hydrophobic film made of hexamethyldisilazane (HMDS), which is one of the organosilicon compounds capable of reacting with hydroxyl groups, was investigated. As shown in FIG. 7, it was found that the durability suddenly decreased immediately after standing, reached a predetermined level several minutes later, and then left standing for several days, after which the durability gradually recovered again. The phenomenon will be described in more detail. In the case where the space between the opposing members is sealed in the range of the region B in FIG. As a result, gel-like foreign matter is generated between the opposing members, and it becomes difficult to operate the actuator. The time at which the gel-like foreign matter is generated becomes later as the gap between the opposing members is sealed earlier (region A). That is, H in the gap between the opposing members
It was found that the higher the MDS concentration, the more difficult it is to generate gel-like foreign matter. On the other hand, a gel-like foreign substance is less likely to be generated even in a case where it is left for a predetermined time or more until hermetic sealing (region C).

[0009] This peculiar phenomenon is that when a compound for forming a hydrophobic film is excessively present between the opposing members, the compound is easily gelled during repeated charging and discharging of the electrostatic actuator, and an extremely large amount of the compound is sealed. This suggests that if stopped, gelation would be suppressed. It is also considered that, if left for a predetermined time or more until hermetic sealing, an excessive compound is removed by hydrolysis, and an excessive compound causing foreign matter is removed.

That is, from the above experimental results, in order to obtain a durable hydrophobic film, a compound for forming a hydrophobic film between the opposing surfaces is injected, and then 1) the compound is present in the gap between the opposing surfaces. If the concentration of the compound for forming the hydrophobic film is kept at or above a predetermined value, the gap is hermetically sealed, or 2) the gap is sealed after leaving the facing member in the air for several days. It turned out to be good.

When an electrostatic actuator is manufactured by a method 1) in which the gap is hermetically sealed while the concentration of the compound is maintained at a predetermined value or more, according to experiments conducted by the present inventors, It has been confirmed that if the gap is hermetically sealed at a concentration of 0.3 to 0.8% or more, the durability of the hydrophobic film can be made practically sufficient.

As described above, it is desirable to seal the gap between the opposed members in a state where the concentration of the compound is as high as possible.
For this purpose, it is preferable to adopt a step of performing an operation of sealing the gap in a tank filled with HMDS, but on the other hand, the following points may be problems. That is, the sealing material in the tank,
Specifically, sealing the gap using an epoxy-based adhesive is not an easy task. Contamination of the inside of the tank with components of the adhesive other than HMDS is not preferable for quality control.

Therefore, it is more suitable to mass-produce electrostatic actuators by adopting a process in which the gap is quickly sealed after the electrostatic actuator placed in the tank for a predetermined time is taken out of the tank. However, it was difficult to keep the compound at a high concentration and seal it outside the tank.

[0014] The object of the present invention is to solve the above problems.
Provides an electrostatic actuator with a durable hydrophobic film, while keeping the compound for forming the hydrophobic film injected into the actuator at a high concentration and sealing it outside the tank Another object of the present invention is to provide an electrostatic actuator having a shape suitable for mass production.

[0015]

According to the present invention, there are provided a plurality of opposed members which are arranged opposite to each other at a fixed interval and which can be displaced relative to each other; And a driving means for selectively displacing relative movement of each of the opposing members, a segment electrode provided on one of the opposing members and selectively energized by the driving means, and each of the opposing members are formed. Are formed as part of a wall surface, and a vibration chamber in which segment electrodes are formed respectively, and a lead portion that connects each vibration chamber to the outside of the actuator and electrically connects the segment electrode and the driving unit are formed respectively. And a first sealing member that seals the outer ends of all the first tubes in the vibration chamber to enclose a compound that forms a hydrophobic film between the facing members. A plurality of said first tubes Second communicating with the actuator outside
And a second sealing member for sealing an outer end of the second tube.

Further, according to a method of manufacturing an electrostatic actuator of the present invention, in the above-described method of manufacturing an electrostatic actuator, the first tube is sealed with the first sealing material, and the first tube is filled with the compound. After placing the actuator in the treated tank, allowing the compound to penetrate between the opposed members, and attaching a hydrophobic film between the opposed members, the second tube is sealed with the second sealing material outside the treated tank. It is characterized by sealing with.

The compound is preferably, for example, an organic silicon compound having a hydrophobic group and capable of reacting with a hydroxyl group. These are because the molecular weight is easier to inject into the minute gap than the fluorine compound. That is, in a method in which a compound is filled in a treatment tank and the compound is caused to penetrate into an actuator placed therein to form a hydrophobic film, it is preferable to use an organosilicon compound having a small molecular weight.

More specific organosilicon compounds include, for example,
Formula R ₃ —Si—X or Formula R ₃ —SiNHSi—
It is a compound represented by R ₃ (R represents an alkyl group, X represents a halogen or an amino group), and includes hexamethyldisilazane ((CH ₃ ) ₃ SiNHSi (CH ₃ ) ₃ ) and hexaethyldisilazane ((C ₂ H _{5) 3} SiNHSi (C
₂ H ₅ ) ₃ ), trimethylchlorosilane ((CH ₃ ) ₃
SiCl), triethylchlorosilane ((C ₂ H ₅ ) ₃
SiCl), trimethylaminosilane ((CH ₃ ) ₃ S
iNH ₂ ), triethylaminosilane ((C ₂ H ₅ ) ₃
SiNH ₂ ). The organic silicon compound is, for example, dimethyldichlorosilane ((CH ₃ ) ₂ S
iCl ₂ ) such as R ₂ —Si—X (R is an alkyl group, X
Represents a halogen, an amino group, or a silylated amine).

An electrostatic actuator to which the present invention can be applied is an ink jet head used in an ink jet recording apparatus. In this case, the electrostatic actuator is configured to include an ink chamber whose volume is changed by the relative displacement of the first and second members, and an ink nozzle communicating with the ink chamber, Comprises a counter electrode formed on the first member and the second member, and voltage applying means for applying an electric pulse between these counter electrodes, and in response to the application of the electric pulse What is necessary is just to make it discharge an ink droplet from the said ink nozzle.

As described above, according to the present invention, the second tube functioning as a bypass is provided for the first tube indispensable for connecting the driving circuit with the segment electrode formed in each vibration chamber. After the hydrophobic film is attached, each vibration chamber (gap between the opposing members) is kept outside the treatment tank using only the second tube while maintaining the compound forming the hydrophobic film at a predetermined concentration.
Can be hermetically sealed. Since the cross-sectional area of the second pipe is smaller than the total cross-sectional area of the first pipe, even if the sealing step is performed outside the processing tank, the sealing is completed as compared with the case where the second pipe is not used. During this period, a decrease in the concentration of the compound in the vibration chamber is suppressed. In addition, if the number of vibration chambers of the first tube increases, the number of nozzles increases in the case of an inkjet head.
Although it is necessary, only one second pipe works well, so after the adhering process, only one place is required to seal the gap, and the sealing area is smaller than that without the bypass pipe. Therefore, there is an advantage that sealing can be performed more quickly.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which an electrostatic actuator inkjet head of the present invention is applied to an inkjet head will be described with reference to the drawings.

(Overall Configuration) FIG. 1 is an exploded perspective view of an ink jet head to which the present invention is applied. FIG. 2 is a sectional view of the assembled ink jet head (FIG. 3).
3 is a plan view thereof, and FIG. 4 is a portion thereof (I-II section).
V-IV) is a sectional view.

As shown in these figures, the ink jet head 1 is of a face ink jet type in which ink droplets are ejected from ink nozzles provided on the upper surface of a substrate, and is of an electrostatic drive type. The ink jet head 1 has a cavity plate 3 sandwiched therebetween, a nozzle plate 2 on the upper side, and a glass substrate 4 on the lower side.
It has a layer structure.

The cavity plate 3 is, for example, a silicon substrate. On the surface of the plate, a concave portion 7 whose bottom wall forms an ink chamber 6 functioning as a vibration plate 5;
The narrow groove 9 for forming an ink supply port 8 provided at the rear of the concave portion 7 and the concave portion 11 for forming an ink reservoir 10 for supplying ink to each ink chamber 6 are formed by etching. Is formed. The lower surface of the cavity plate 3 is smoothed by mirror polishing.

The nozzle plate 2 joined to the upper side of the cavity plate 3 is, for example, a silicon substrate, like the cavity plate 3. Nozzle plate 2
In a portion defining the upper surface of the ink chamber 6, a plurality of ink nozzles 21 communicating with each ink chamber 6 are formed.

The electrostatic actuator is provided for each ink chamber in order to temporarily increase the pressure in each ink chamber and eject ink droplets from the corresponding ink nozzle. The electrostatic actuator has two electrode members facing each other with a small gap. In the present embodiment, one electrode is formed at the bottom of the ink chamber 6 as a deformable diaphragm 5 described later. The other electrode is formed in the recess 16 of the glass substrate 4. As described later, in the present embodiment, since the cavity plate 3 is a conductor, the diaphragm 5 itself functions as one electrode of the electrostatic actuator.

By joining the nozzle plate 2 to the cavity plate 3, the recesses 7 and 11 and the narrow groove 9 are closed, and the ink chamber 6, the ink supply port 8, and the ink reservoir 10 are partitioned. It is formed.

A hole 12a for supplying ink to the ink reservoir 10 is provided in a portion defining the bottom surface of the ink reservoir 10. After the substrate is joined, the hole 12a is provided together with a hole 12b provided in the glass substrate 4 described later. Ink supply hole 1
Form 2 The ink supply hole 12 is connected to an ink tank (not shown) via a connection tube (not shown). The ink supplied from the ink supply holes 12 is supplied to the independent ink chambers 6 via the respective ink supply ports 8.

The glass substrate 4 bonded to the lower side of the cavity plate 3 is a borosilicate glass substrate having a coefficient of thermal expansion close to that of silicon. In the glass substrate 4, a concave portion 16 that forms a vibration chamber (gap) 15 is formed in a portion facing each of the vibration plates 5. This recess 1
On the bottom surface of 6, an individual electrode 17 facing the diaphragm 5 is formed. The individual electrode 17 has a segment electrode portion 18 made of ITO and a terminal portion 19.

By joining this glass substrate 4 to the cavity plate 3, the diaphragm 5 defining the bottom surface of each ink chamber 6 and the segment electrode portion 18 of the individual electrode 17 are formed.
Face each other with a very narrow gap. This gap 15 is sealed by a sealing material 20 arranged between the cavity plate 3 and the glass substrate 4.

The diaphragm 5 is made thin and has an out-of-plane direction,
That is, it can be elastically deformed vertically in FIG. The vibration plate 5 functions as a common electrode on each ink chamber side. The bottom surface 51 of the diaphragm 5 as the common electrode
Has hexamethyldisilazane ((CH ₃ ) ₃ SiNHS
A hydrophobic film 22 made of an organosilicon compound is formed using i (CH ₃ ) ₃ (hereinafter simply referred to as HMDS). A hydrophobic film 23 made of an organosilicon compound is also formed on the surface of the segment electrode portion 18 of the individual electrode 17 facing the diaphragm 5 using HMDS. A counter electrode is formed by the diaphragm 5 and the corresponding segment electrode portions 18 with the gap 15 interposed therebetween.

A voltage applying device 25 is connected between the diaphragm 5 and the individual electrodes 17. One output of the voltage applying device 25 is connected to the terminal 19 of each individual electrode 17, and the other output is connected to a common electrode terminal 26 formed on the cavity plate 3. Since the cavity plate 3 itself has conductivity, a voltage can be supplied from the common electrode terminal 26 to the diaphragm (common electrode) 5. When a voltage needs to be supplied to the diaphragm 5 with a lower electric resistance, for example, a thin film of a conductive material such as gold may be formed on one surface of the cavity plate 3 by vapor deposition or sputtering. . In this example, since the anodic bonding is used to connect the cavity plate 3 and the glass substrate 4, a conductive film is formed on the channel forming surface side of the cavity plate 3.

In the ink jet head 1 configured as described above, when the driving voltage from the voltage applying device 25 is applied between the opposing electrodes, a Coulomb force is generated by the electric charge charged between the opposing electrodes, and the diaphragm 5 Deflects toward the segment electrode portion 18, and the volume of the ink chamber 5 increases. next,
When the drive voltage from the voltage applying device 25 is released and the electric charge between the opposing electrodes is discharged, the diaphragm 5 is restored by its elastic restoring force, and the volume of the ink chamber 6 is rapidly reduced. Due to the change in the internal pressure generated at this time, a part of the ink stored in the ink chamber
Discharge from 1 toward the recording paper.

The ink used in the ink jet head 1 is prepared by dissolving or dispersing a surfactant such as ethylene glycol and a dye or pigment in a main solvent such as water, alcohol and toluene.
Furthermore, if a heater is provided in the inkjet head 1, hot melt ink can also be used.

(Manufacturing Method) An optimum manufacturing method of the electrostatic actuator will be described below.

FIG. 5 is a schematic flowchart showing an example of a manufacturing process of the ink jet head 1 having the above-described configuration. As shown in this figure, first, in step ST1, the cavity plate 3, the nozzle plate 2, and the glass substrate 4 constituting the inkjet head 1 are manufactured by processing each from a wafer. Next, step ST
In 2, the three members are assembled (joined) together to form an ink jet head. That is, the glass substrate 4 is mounted on the bottom surface side of the cavity plate 3 so that the space 15 is formed. In this state, neither the bottom surface 51 of the diaphragm 5 as a common electrode nor the surface of the segment electrode portion 18 has a hydrophobic film formed thereon.

Next, in the pretreatment (drying) step of step ST3, a pretreatment is applied to the ink jet head 1 to remove water adhering to its surface or to reduce as much as possible. For example, the inkjet head 1 may be left in a processing tank supplied with dry air. By performing such a pretreatment step, it is possible to stabilize the adhesion state of HMDS. That is, the bottom surface 5 of the diaphragm 5
1, and by reducing / removing excess adhered water from the surface of the segment electrode portion 18, stabilization of the HMDS adhesion state can be achieved, and it is possible to avoid occurrence of variation in the HMDS adhesion state in the next step. In addition to the method using dry air, a vacuum heating step in which the inside of the processing tank is heated by applying a vacuum, a step in which the inside of the processing tank is alternately switched to a vacuum atmosphere and a nitrogen atmosphere, and a combination thereof are adopted as pretreatment steps. Can be.

Next, in the HMDS attaching step of step ST4, hydrophobic films 22 and 23 made of HMDS are formed on the bottom surface 51 of the diaphragm 5 as a common electrode and on the surface of the segment electrode portion 18, respectively. For example, a container containing HMDS is placed in the processing tank, the supply of dry air is stopped, and the atmospheric pressure is set to atmospheric pressure at normal temperature and normal humidity. This state is maintained until the HMDS sufficiently enters the gap 15 by diffusion ( (About 20 hours in this embodiment). As a result, the hydrophobic film 22 made of HMDS is formed on the bottom surface 51 of the diaphragm 5 and the surface of the segment electrode portion 18 as the common electrode.
23 are formed. At this time, the HMDS concentration in the processing tank may be about 0.8% or more. As will be described later, since the gap between the opposing electrodes of the actuator is hermetically sealed outside the processing tank, the concentration of HMDS in the gap decreases until the gap is hermetically sealed. It becomes lower than the concentration in the processing tank. In anticipation of this decrease in concentration, the concentration of HMDS after hermetic sealing is at least 0.3%.
The HMDS concentration in the processing tank is set so as to be as described above.

FIG. 6 shows a molecular bonding state of the HMDS hydrophobic layers 22a and 23a formed on the bottom surface of the vibration plate 5 made of silicon and the surface of the segment electrode portion 18 made of ITO. As shown in this figure, on each surface, OH groups are replaced with OSi (CH3) 3 groups which are hydrophobic groups.

Next, in the hermetic sealing step of step ST5, the inkjet head 1 is taken out of the processing tank, and the space between the diaphragm 5 and the segment electrode portion 18 is hermetically sealed outside the processing tank within 3 minutes. To form a gap 15.
At this time, the HMDS concentration in the hermetically sealed gap 15 becomes about 0.3% or more.

FIG. 7 is a graph showing the correlation between the standing time and the durability of the hydrophobic films 22 and 23 when the inkjet head is left outside immediately after the formation of the hydrophobic films 22 and 23. This graph was obtained when the HMDS concentration in the treatment tank in the sealing step was set to 0.8% or more. In addition, the durability is one of the diaphragms 5.
The vibration was measured as one cycle.

As can be seen from this graph, after the hydrophobic films 22 and 23 made of HMDS are formed, they are taken out of the processing tank without sealing in this state, and left in the atmosphere, the hydrophobic film 22 , 23 immediately decrease immediately after being taken out of the processing tank (downward right region A). Then, after a few minutes, it stabilizes to a predetermined durability level. (Stable region B). After that, if left further, the durability gradually recovers again after several days. (Right-up region C). In addition, the durability of the upward-sloping region C is lower than the durability immediately after forming the hydrophobic films 22 and 23 (the downward-sloping region A).

In the manufacturing method of this embodiment, the HMDS
The gap 15 is hermetically sealed so that the concentration becomes about 0.3% or more. That is, the gap 15 is hermetically sealed in the lower right region A in FIG. For this reason, the durability of the hydrophobic films 22 and 23 formed on the surface of the diaphragm 5 and the surface of the segment electrode portion 18 is just after or close to the hydrophobic films 22 and 23 formed. As is clear from FIG. 8, if the HMDS concentration in the gap 15 is hermetically sealed with the HMDS concentration of about 0.3% or more after forming the hydrophobic films 22 and 23, the durability of about tens of millions to several billions of cycles is obtained. Is obtained.

FIG. 8 shows the correlation between the HMDS concentration in the gap 15 obtained when the gap 15 is hermetically sealed within the leaving time included in the lower right region A in FIG. 7 and the durability of the hydrophobic films 22 and 23. It is a graph of a relationship. As can be seen from this graph, the gap 15 of the inkjet head 1 is 0.3
%, So that the durability of the hydrophobic films 22 and 23 is about 20 million cycles or more. Therefore, after leaving the hydrophobic films 22 and 23 for several days after forming them, it is possible to obtain a hydrophobic film having a durability equal to or higher than that when the gap 15 is hermetically sealed. For example, the HMDS concentration in the gap 15 is about 0.4%
By doing so, the hydrophobic films 22, 23 having a durability of 100 million cycles or more can be obtained.

Here, as the HMDS concentration in the gap 15 increases, the durability of the hydrophobic films 22 and 23 increases. However, when the HMDS concentration is about 0.8%, the durability of the hydrophobic film is saturated to about 5 billion cycles. For this reason, considering the management error of the HMDS concentration in the processing tank, and the decrease in the concentration from the removal from the processing tank to the hermetic sealing, etc., the HMDS concentration in the processing tank is set to 1.0% to 2.0%. It is most preferable to set before and after.

As described above, according to the method of the present embodiment, it is necessary to leave the hydrophobic films 22 and 23 made of HMDS for several days after the formation of the hydrophobic films in order to ensure sufficient durability. Absent. That is, there is an advantage that the electrostatic actuator can be manufactured in a short time.

Here, if the HMDS adhering step of step ST4 is performed, a hydrophobic film is also formed on the other surface of the cavity plate 3 to impart hydrophobicity, and the discharging property of bubbles in the ink flow path is deteriorated. Problems occur. However, after performing the hermetic sealing step of step ST5, it is possible to easily remove the hydrophobic film from the ink flow path surface by performing RCA cleaning (cleaning using a mixed solution of ammonia and hydrogen peroxide). It is possible. For this reason, it is possible to prevent problems such as deterioration in bubble discharge performance from occurring.

(Structure of Sealing Portion of Ink Jet Head Gap) The structure of the sealing portion of the ink jet head gap between ink jet heads will be described below with reference to FIGS.

As described above, it is desirable to seal the gap between the opposing members in a state where the concentration of HMDS is high. For this purpose, it is preferable to adopt a step of performing an operation of sealing a gap in a tank filled with HMDS, but also has the following disadvantages. That is, it is not an easy task to seal the gap in the tank using a sealing material, specifically, an epoxy-based adhesive. Contamination of the inside of the tank with components of the adhesive other than HMDS is not preferable for quality control.

Therefore, it is more suitable to mass-produce electrostatic actuators by adopting a process in which the gap is quickly sealed after the electrostatic actuator placed in the tank for a predetermined time is taken out of the tank. I have.

Immediately after being taken out of the tank, H
It is also evident from FIG. 7 that the MDS is reduced and the durability is reduced if it takes time before the sealing. That is, the inclination of the area A in FIG. 7 indicates the speed at which the concentration of HMDS in the gap between the opposing members of the electrostatic actuator after being taken out of the tank decreases. There is a need to.

The present embodiment relates to a structure for sealing a gap between opposed members, and suppresses a decrease in the concentration of HMDS in the gap until the sealing.

FIG. 9 is a plan view showing a sealed portion of the gap between the opposing members of the ink jet head shown in FIG.
Reference numeral 18 denotes an individual electrode.
Are connected by a lead portion 17b. These electrodes 17 and 17b are formed by depositing ITO in the concave portions 16 provided on the glass substrate 4.

As shown, the recess 16 is divided into two parts. The dimensions of the concave portion of the portion to be the actuator portion (vibration chamber 15) are width b and length a.
The dimensions of the concave portion at the portion that becomes the tube 15b connecting the outside and the outside are width d and length L. After joining the glass substrate 4 and the cavity plate 3 and attaching and attaching the HMDS into the vibration chamber 15, the open end of the tube 15 b is closed by the sealing material 20.

The volume of the vibration chamber 15 is defined as V (a × b × g, g is the distance between the opposing members (the distance between the diaphragm 5 and the electrode 17).
Assuming that the cross-sectional area of 5b is S (d × g), the magnitude of the value K expressed by the following equation is the concentration of HMDS in the gap between the opposing members of the electrostatic actuator after being taken out of the tank. Experiments have shown that if K ≧ 25, the durability of the electrostatic actuator can be sufficiently ensured even if the gap is sealed outside the tank if K ≧ 25.

K = V · L / S In the area A of FIG. 7, the solid line portion is K = 10, and the wavy line portion is K = 2.
5 shows the correlation between the durability and the time until hermetic sealing in the case of No. 5. As is clear from the figure, if the sealing is performed within one minute, the durability of about 100 million pulses can be obtained if K = 25, whereas the durability of about 10 million pulses can be obtained if K = 10. It is also difficult. In order to obtain a durability of 100 million pulses at K = 10, it is necessary to exit the tank and complete the sealing process in about 10 seconds, which is practically impossible in a process assuming mass production.

Hereinafter, the electrostatic actuator of the present invention will be described with reference to FIG.

FIG. 10 is a plan view of a sealing portion of a gap of an ink jet head according to another embodiment. 9 are the same as those in the embodiment described with reference to FIG.

The plurality of vibration chambers 15 arranged in a row have
Tubes 15b connecting each vibration chamber 15 and the sealing portion 20a, respectively
Are connected, and a bypass pipe 15c connecting the pipes 15b is further provided. A sealing portion 20b is also provided on the open end side of the bypass pipe 15c.

The HMDS is sealed in the vibration chamber 15 and manufactured according to the following procedure.

First, a predetermined portion of the glass substrate 4 is etched to form a concave portion, and the individual electrode 1 is placed at a predetermined position in the concave portion.
7 is formed. By anodically bonding the glass substrate 4 and the cavity plate 3 provided with the vibration plate 5, the vibration chamber 15, the tubes 15b and 15c are formed. Each tube 15
After sealing the open end of b with the sealing material 20a, the inkjet head is put into a tank filled with HMDS of a predetermined concentration and left in the tank for a predetermined time. Thereafter, the inkjet head is taken out of the tank, the open end of the bypass pipe 15c is sealed with a sealing material 20b, and the vibration chamber is shut off from the outside air while HMDS having a predetermined concentration or more is kept in the vibration chamber.

By providing such a bypass pipe, the K value can be increased by 50 to 60 as compared with the case where no bypass pipe is provided, without increasing the area of the ink jet head itself.
About twice as much. That is, the HM of the gap between the opposing members of the electrostatic actuator after being taken out of the tank.
It is possible to suppress a decrease in DS concentration.

Further, after the HMDS adhering step, there is only one place for sealing the gap, and the area for sealing is smaller than that without the bypass pipe, so that there is an advantage that the sealing can be performed more quickly.

[Other Embodiments] In the above-described embodiment, the compound hermetically sealed between the opposing members is H.
Although MDS has been described as an example, the present invention is not limited to this, and any organic silicon compound having a hydrophobic group and capable of reacting with a hydroxyl group can be applied to the present invention. This organosilicon compound is, for example, of the formula R ₃ —Si—X or the formula R ₃ —SiNHS
i-R ₃ (R is an alkyl group, X is a halogen or an amino group) and the compounds represented by, in addition to HMDS example, hexaethyl disilazane _{((C 2 H 5) 3} S
iNHSi (C ₂ H ₅ ) ₃ ), trimethylchlorosilane ((CH ₃ ) ₃ SiCl), triethylchlorosilane ((C ₂ H ₅ ) ₃ SiCl), trimethylaminosilane ((CH ₃ ) ₃ SiNH ₂ ), triethylaminosilane (( C ₂ H ₅ ) ₃ SiNH ₂ ) and the like. Further, for example, dimethyldichlorosilane ((CH ₃ ) ₂ SiCl
₂ ), etc., an organosilicon compound represented by the formula R ₂ —Si—X (R represents an alkyl group, X represents a halogen or an amino group) may be applied to the present invention. In addition, a hydrophobic film is formed by hermetically sealing the actuator at a predetermined concentration or higher while maintaining a predetermined concentration or more, and is not limited to the organosilicon compound. Compounds containing the same can be applied to the present invention.

The ink jet head 1 described above
Is a face inkjet type in which ink droplets are ejected from an ink nozzle provided on the upper surface of a substrate, but the inkjet head of the present invention can also be applied to an edge inkjet type in which ink droplets are ejected from an ink nozzle provided at an end of the substrate.

In the above example, the present invention is applied to an ink jet head. However, the present invention is disclosed in an electrostatic actuator other than the ink jet head, for example, Japanese Patent Application Laid-Open No. 7-54259. The present invention can be similarly applied to a micromechanical device, a display device using an electrostatic actuator, a micropump, and the like.

[0067]

As described above, in the electrostatic actuator according to the present invention, the bypass is provided for the first pipe which is indispensable for connecting the segment electrode formed in each vibration chamber and the drive circuit. By providing the second tube functioning as the above, after the hydrophobic film is adhered, the compound forming the hydrophobic film is maintained at a predetermined concentration by using only the second tube outside the treatment tank, and each vibration chamber (opposing member) (A gap between them) can be hermetically sealed. Since the cross-sectional area of the second pipe is smaller than the total cross-sectional area of the first pipe, even if the sealing step is performed outside the processing tank, the sealing is completed as compared with the case where the second pipe is not used. During this period, a decrease in the concentration of the compound in the vibration chamber is suppressed. Also, the first tube is required as the number of vibration chambers increases (in the case of an ink jet head, the number of nozzles increases). In addition, since only one place is required to seal the gap and the area to be sealed is smaller than that without the bypass pipe, there is an advantage that the sealing can be performed more quickly. Therefore, even if the gap is sealed outside the tank, the durability of the electrostatic actuator can be sufficiently ensured.

Accordingly, an electrostatic actuator having a durable hydrophobic film is provided, and the compound for forming the hydrophobic film injected into the actuator is maintained at a high concentration and sealed outside the tank. There is an effect that an electrostatic actuator that can be stopped, that is, a shape suitable for mass production can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an inkjet head to which the present invention has been applied.

FIG. 2 is a schematic longitudinal sectional view of the inkjet head of FIG.

FIG. 3 is a plan view of the inkjet head of FIG. 1;

FIG. 4 is a schematic cross-sectional view showing a part of the inkjet head of FIG.

FIG. 5 is a schematic flowchart showing a manufacturing process of the inkjet head of FIG.

FIG. 6 is a schematic diagram showing a formed HMDS hydrophobic layer.

FIG. 7 is a graph showing the correlation between the standing time and the durability of the hydrophobic film when the inkjet head is left outside immediately after the formation of the hydrophobic film.

8 is a graph showing the correlation between the HMDS concentration in the gap and the durability of the hydrophobic film obtained when the gap is hermetically sealed within the leaving time included in the lower right region of FIG. 7;

FIG. 9 is a plan view showing a sealing portion of a gap between opposing members of the inkjet head shown in FIG.

FIG. 10 is a plan view showing a sealing portion of a gap of an inkjet head according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet head 2 Nozzle plate 3 Cavity plate 4 Glass substrate 5 Vibration plate (Common electrode) 6 Ink chamber 8 Ink supply port 10 Ink reservoir 15 Gap 17 Individual electrode 18 Segment electrode part 20 Sealing material 25 Voltage applying device 26 Common electrode Terminal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Keiichi Mukaiyama 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation

Claims (10)

[Claims] 1. A plurality of opposing members that are disposed opposite to each other at a fixed interval and that can be relatively displaced, and a drive that selectively generates an electrostatic force between the opposing members to selectively displace the opposing members relative to each other. A segment electrode provided on one member side of each opposing member and selectively energized by the driving means, and a surface on which each opposing member is formed is part of a wall surface. A vibration chamber in which a segment electrode is formed, a first tube in which each vibration chamber is connected to the outside of the actuator, and a lead portion for electrically connecting the segment electrode and the driving means is formed; A first sealing member for sealing the outer ends of all the first tubes in the vibration chamber for enclosing a compound forming a hydrophobic film between the opposed members; and a plurality of the first tubes. And outside the actuator Second tube and said second electrostatic actuator comprising the second sealing member for sealing the outer end of the tube passing. 2. The electrostatic actuator according to claim 1, wherein the compound is an organic silicon compound having a hydrophobic group and capable of reacting with a hydroxyl group. 3. The method according to claim 2, wherein the organosilicon compound has a formula of R ₃ —Si—X or a formula of R ₃ —SiNHSi.
-An electrostatic actuator, characterized by being a compound represented by R ₃ (R represents an alkyl group, X represents a halogen or an amino group). 4. The method according to claim 2, wherein the compound is hexamethyldisilazane ((CH ₃ ) ₃ SiNHSi (CH
₃ ) ₃ ), Hexaethyldisilazane ((C ₂ H ₅ ) ₃ S
iNHSi (C ₂ H ₅ ) ₃ ), trimethylchlorosilane ((CH ₃ ) ₃ SiCl), triethylchlorosilane ((C ₂ H ₅ ) ₃ SiCl), trimethylaminosilane ((CH ₃ ) ₃ SiNH ₂ ), triethylaminosilane (( C ₂ H ₅ ) ₃ SiNH ₂ ). 5. The organic silicon compound according to claim 2, wherein the organic silicon compound is a compound represented by the formula R ₂ —Si—X (R represents an alkyl group, X represents a halogen or an amino group). Electrostatic actuator. 6. The electrostatic actuator according to claim 5, wherein the compound is dimethyldichlorosilane ((CH ₃ ) ₂ SiCl ₂ ). 7. The electrostatic actuator according to claim 1, wherein the concentration of the compound between the opposed members is 0.3% or more. 8. The electrostatic actuator according to claim 1, wherein the concentration of the compound between the opposed members is 0.8% or more. 9. The driving unit according to claim 1, further comprising: an ink chamber whose volume is changed by a relative displacement of the facing member, and an ink nozzle communicating with the ink chamber. Comprises an opposing electrode formed on each of the opposing members, and voltage applying means for applying an electric pulse between these opposing electrodes, and ink droplets are ejected from the ink nozzle in response to the application of the electric pulse. An electrostatic actuator characterized in that the electrostatic actuator is adapted to be operated. 10. The method for manufacturing an electrostatic actuator according to claim 1, wherein the first tube is sealed with the first sealing material, and the actuator is placed in a processing tank filled with the compound. Placing the compound between the opposing members, attaching a hydrophobic film between the opposing members, and sealing the second tube with the second sealing material outside the treatment tank. Manufacturing method of an electrostatic actuator.