JP2001268947A - Electrostatic actuator and ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure a stable hermetical sealing of as route to prevent the entry of a sealing agent into a vibration chamber in an electrostatic actuator provided with the vibration chamber that is relatively displaced with an electrostatic force and a route that communicates with the vibration chamber and is hermetically sealed. SOLUTION: A sealing agent reservoir 94, in which a sealing adhesive 93 is reserved in a route 9 communicating with the vibration chamber 16 of an ink jet head 1 as an electrostatic actuator, is formed of a glass substrate. Since a plurality of sealing agent reservoirs 94 are formed, the length of unsealed allowance portion can be controlled easily and the sealing agent reservoir 94 can surely prevent the entry of the sealing adhesive 93 and thereby the sealing adhesive 93 never enters the vibration chamber 16. Accordingly, the vibration chamber 16 can be placed in the stably and hermetically sealed condition to realize highly reliable electrostatic actuator.

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 a diaphragm and a counter electrode as a driving source.

[0002]

2. Description of the Related Art An ink-jet head of an ink-jet printer is an actuator having a minute structure formed by using a semiconductor fine processing technique. As an actuator having such a minute structure, an actuator utilizing electrostatic force as a driving source thereof is known. For example, the present applicant discloses an electrostatic ink jet head that discharges ink droplets by using an electrostatic force in JP-A-5-50601 and JP-A-6-71882.

In an ink jet head of this type, the bottom surface of an ink flow path communicating with a nozzle is formed as a vibrating plate which can be elastically deformed, and a substrate is arranged on the vibrating plate at regular intervals. And a substrate on which counter electrodes are arranged. When a voltage is applied between the opposing electrodes, the vibrating plate is electrostatically attracted to the substrate side and vibrates due to the electrostatic force generated between them. Ink droplets are ejected from the nozzles by fluctuations in the internal pressure of the ink flow path caused by the vibration of the diaphragm.

[0004]

However, the above-mentioned conventional electrostatic actuator has the following problems. First, in the former case, since the gap between the opposing electrodes is in communication with the atmosphere, water and dust in the atmosphere enter the gap between the opposing electrodes due to the action of static electricity, and the diaphragm is statically positioned on the substrate side. Electric suction is stopped.

[0005] On the other hand, in the latter case, it has been proposed to hermetically seal the passage communicating with the gap between the opposing electrodes with an epoxy-based adhesive in order to solve the above problem.

However, the above-mentioned hermetic sealing structure has a problem as described below because it is not a structure for reliably stopping the sealing material. The sealing material entered the vibration chamber of the actuator and hindered the function, or the yield of the inkjet head was poor. Further, when the length of the passage communicating with the gap between the opposing electrodes is made as long as possible so that the sealing material does not enter the vibration chamber, the size of the ink jet head has been increased.

[0007] In view of the above, the object of the present invention is to provide:
An object of the present invention is to provide a highly reliable electrostatic actuator that stably hermetically seals a passage communicating with a gap between opposed electrodes.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a vibration plate, a counter electrode disposed to face the vibration plate, and the diaphragm and the counter electrode. In an electrostatic actuator having a vibration chamber and a passage one of which communicates with the vibration chamber and the other of which is hermetically sealed by a sealing material, the sealing material reservoir in which the width of the passage is wide is formed by the passage. Is formed on the vibration chamber side.

With the above-described structure, the sealing material has a sudden increase in the volume of the passage at the sealing material accumulation portion, so that the approach speed is rapidly reduced, and the incomplete sealing margin is reduced. . By providing the sealing material reservoir, the length of the passage can be shortened.

[0010] It is preferable that the encapsulant reservoir is formed of a glass substrate. Further, in the present invention, it is preferable that the length of a sealing margin hermetically sealed by the sealing material for the passage is 1 mm or more.

According to the above configuration, the quality of hermetic sealing can be improved.

Further, it is preferable that a plurality of the sealing material reservoirs are arranged at a position where the distance from the sealing material reservoir to the vibration chamber is at least 0.2 mm.

According to the above configuration, it is possible to prevent the sealing material from entering the vibration chamber. On the other hand, a nozzle, an ink flow path in which the vibration plate is formed in a part in communication with the nozzle, a counter electrode disposed to face the vibration plate with a certain gap, and one surface by the vibration plate An ink-jet head having a vibration chamber partitioned and including the counter electrode, and a passage one of which communicates with the vibration chamber and the other of which is hermetically sealed by a sealing material, wherein the width of the passage is widened. A stop material reservoir is formed on the side of the vibration chamber of the passage.

According to the above configuration, since the volume of the passage of the sealing material suddenly increases at the sealing material accumulation portion, the approach speed is sharply reduced, and the incomplete sealing margin is shortened. As a result, the size of the head can be reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ink jet head which is an electrostatic actuator to which the present invention is applied will be described with reference to the drawings.

FIG. 1 is a sectional view of an ink jet head as an electrostatic actuator to which the present invention is applied.
Is a plan view thereof.

As shown in these figures, an ink jet head 1 has a silicon substrate 2 sandwiched therebetween, a nozzle plate 3 also made of silicon on the upper side, and a borosilicate glass substrate 4 having a thermal expansion coefficient close to that of silicon on the lower side. It has a three-layer structure.

The central silicon substrate 2 is etched from its surface so that five independent ink chambers 5, one common ink chamber 6, and this common ink chamber 6 communicate with each ink chamber 5. The grooves functioning as the ink supply paths 7 are formed. These grooves are closed by the nozzle plate 3 to define the respective portions 5, 6, and 7.

Nozzles 11 are formed in the nozzle plate 3 at positions corresponding to the front end portions of the respective ink chambers 5, and these nozzles communicate with the respective ink chambers 5. Further, an ink supply port 12 (FIG. 2) communicating with the common ink chamber 6 is provided at a portion of the nozzle plate 3 where the common ink chamber 6 is located.
Reference) is formed. The ink is supplied from an external ink tank (not shown) to the common ink chamber 6 through the ink supply port 12. The ink supplied to the common ink chamber 6 is supplied to each independent ink chamber 5 through each ink supply path 7.

Each of the independent ink chambers 5 has a thin bottom wall 51 and is set so as to function as a diaphragm that can be elastically displaced in an out-of-plane direction, that is, in a vertical direction in FIG. Therefore, the bottom wall 51 may be referred to as a diaphragm for convenience of the following description.

Next, in the glass substrate 4 located below the silicon substrate 2, the upper surface of the glass substrate 4, which is in contact with the silicon substrate 2, is located at a position corresponding to each ink chamber 5 of the silicon substrate 2. A recess 8 which is shallowly etched and which communicates with the recess 8 to form a passage 9 is formed. On the surface of the concave portion of the glass substrate 4, a segment electrode 10 made of ITO is formed.

Here, the distance between the diaphragm 51 and the segment electrode 10 arranged opposite thereto, that is, the distance G between the vibration chambers 16 (hereinafter, referred to as "gap length") is determined.
The difference is the difference between the depth of the recess 8 and the thickness of the segment electrode 10. The vibration chamber 16 is hermetically sealed by sealing the passage 9 with a sealing adhesive 93.

As shown in FIG. 2, a voltage applying means 21 for applying a driving voltage between these opposing electrodes is driven between these opposing electrodes in accordance with a printing signal (not shown) from outside. Apply voltage. One output of the voltage applying means 21 is connected to each segment electrode 10, and the other output is connected to a common electrode terminal 22 formed on the silicon substrate 2.

Since the silicon substrate 2 itself has conductivity,
A voltage can be supplied from the common electrode terminal 22 to the common electrode on the bottom wall 51. When it is necessary to supply a voltage to the common electrode 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 silicon substrate by vapor deposition or sputtering. In this embodiment, since the anodic bonding is used to connect the silicon substrate 2 and the glass substrate 4, a conductive film is formed on the flow channel forming surface side of the silicon substrate 2.

Here, in the ink jet head 1 configured as described above, when the driving voltage from the voltage applying means 21 is applied between the opposed electrodes, an electrostatic force is generated by the electric charge charged between the opposed electrodes, The bottom wall (diaphragm) 51 bends toward the segment electrode 10 and the volume of the ink chamber 5 increases. Next, when the application is stopped, the bottom wall 51 is restored by its elastic restoring force, and the volume of the ink chamber 5 is rapidly contracted. Due to the ink pressure generated at this time, a part of the ink filling the ink chamber 5 is ejected as an ink droplet from the nozzle 11 communicating with the ink chamber.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described in more detail using FIG. FIG. 3 is an enlarged view of the vicinity of the passage 9 in FIG. 2 of the present invention. FIG. 4 is an enlarged view of the vicinity of the passage 9 of the related art having no sealing material reservoir for comparison with FIG. 3 and 4, the broken line indicates the tip position of the sealing adhesive 93 that has entered.

In the electrostatic actuator, the interval between the opposing electrodes is made as small as possible in order to make the electrostatic force generated between the opposing electrodes relatively displaced sufficiently large. In this embodiment, the depth of the concave portion 8 of the electrode glass substrate 3 is set to 0.3 μm, and the thickness of the segment electrode 10 is set to 0.1 μm.
μm. Therefore, the gap length G of the vibration chamber 16 is 0.2 μm.

When the electrostatic actuator having such a shape is hermetically sealed with an epoxy-based low-temperature thermosetting sealing adhesive 93 having a viscosity of 20 to 50 Pa · s, and the sealing adhesive 93 is cured, The sealing adhesive 93 entered from the vicinity of the terminal portion 24 and stopped at the sealing material accumulation portion 94 (see FIG. 3).
Therefore, the sealing adhesive 93 did not flow into the vibration chamber 16. In FIG. 3, the length a1 indicates the length of the sealing allowance in which the width direction of the passage is completely filled with the sealing adhesive and the airtight sealing is possible, and the length b1 indicates that the sealing adhesive has entered. The length c1 indicates the length of the incomplete sealing margin that cannot be hermetically sealed, but the length c1 indicates the length of the unsealing margin of the passage 9 where the sealing adhesive 93 does not enter. Here, in order to clarify the present invention, FIG.
And compare them. The length a2 indicates the length of the complete sealing allowance that can be hermetically sealed, and the length b2 indicates the length of the incomplete sealing allowance that the sealing adhesive has entered but cannot be hermetically sealed. The length c2 indicates the length of the unsealed portion of the passage 9 where the sealing adhesive 93 does not enter.

When there is no sealing material pool, compared to the case where there is a sealing material pool, a2> a1 and b2> b1, so that the tip of the sealing adhesive has a vibration chamber. 16 may flow. In fact, the sealing adhesive 9
In the case where the viscosity of No. 3 was relatively low, the sealing adhesive 93 had entered the vibration chamber 16 after the sealing adhesive was cured.

By forming the sealing material reservoir 94 as in the present invention, the sealing adhesive 93 suddenly increases the volume of the passage 9 at the sealing material reservoir 94. The approach speed is sharply reduced, and as a result, the incomplete sealing margin is shortened, and the incomplete sealing margin is reliably stopped at the sealing material reservoir 94. Also,
Since the incomplete sealing margin is short, it is possible to shorten the length of the passage 9. Furthermore, even if there are a plurality of actuators, the complete sealing allowance, the incomplete sealing allowance, and the unsealed allowance can be made substantially the same, so that the operation characteristics of the actuator are leveled and the quality is thereby improved. Was completed. In this embodiment, in FIG. 3, a plurality of sealing material reservoirs 94 are arranged in the passage 9 so that a1 is 1.0 mm or more and c1 is 0.2 mm or more. This is for the following reason.

When the complete sealing allowance (a1) is shorter than 1 mm, by repeatedly applying a voltage between the opposing electrodes, the moisture and the like in the atmosphere pass through the sealing adhesive 93 and vibrate. It enters the room 16. Moisture or the like that has entered the vibration chamber 16 generates charging between the opposing electrodes by repeating driving. The pressure generated by the diaphragm changes depending on the magnitude and direction of the generated charge, making it impossible to obtain a stable pressure. When the sealing adhesive is cured, a small amount of gas such as water vapor is generated from the sealing adhesive. This gas diffuses from the tip of the sealing adhesive toward the vibration chamber 16 to a certain extent. When the unsealed allowance (c1) is shorter than 0.2 mm, the diffusion extends to the vibration chamber. Therefore, by repeatedly applying a voltage between the opposed electrodes, the gas is charged, and the magnitude of the charge is increased. The pressure generated by the diaphragm changes depending on the direction and direction, making it impossible to obtain a stable pressure.

Further, in this embodiment, the sealing material reservoir 94 is made of an electrode glass. In FIG.
w1 indicates the width of the sealing material reservoir 94, and w2 indicates the depth of the sealing material reservoir 94. In this embodiment, w
1 is 20 μm and w2 is 40 μm. That is, by expanding w2 as much as possible, it is possible to increase the volume of the sealing material reservoir 94. Also, FIG. 3 shows only one vibration chamber as an example, but when the vibration chambers are adjacent to each other, w2 may be increased so that the distance between the sealing pools of the adjacent vibration chambers becomes zero. Good. Therefore, when the depth of the concave portion 8 of the electrode glass substrate 3 is 0.3 μm,
The volume of one sealing material reservoir is 240 μm 3.

FIG. 3 shows an example in which six sealing material pools are provided. However, the viscosity of the sealing adhesive and the sealing property are set so that the desired unsealing allowance (c1) is obtained. The number of the material pools may be changed.

Also in FIG. 5, a sealing material reservoir is formed as in FIG. 3, but this is an example in which a segment electrode is formed in the sealing material reservoir 94. In this example, the same effect as in FIG. 3 can be obtained.

The sealing material reservoir 94 shown in FIGS. 3 and 5 is an example in which an electrode glass substrate is used. The sealing material reservoir 94 functioning as a sealing reservoir is limited to this shape and size. It was not done. In this embodiment, the sealing adhesive 93 is an epoxy-based low-temperature thermosetting type. This adhesive is at room temperature (25 ° C.) to 65
The curing proceeds within the range of ° C. and is completed in 48 to 2 hours.
Since the epoxy resin is excellent in gas barrier properties against water vapor, good hermetic sealing can be achieved. When the sealing adhesive is hermetically sealed, even when the sealing adhesive is heated at the time of curing, the penetration of the sealing adhesive is reliably stopped at the sealing material reservoir 94, and the vibration chamber No intrusion into 16 was seen.

(Other Embodiments) The above description is an example in which the present invention is applied to an ink jet head. The present invention can be similarly applied to an electrostatic actuator other than the inkjet head. For example, the present invention can be similarly applied to a micromechanical device disclosed in JP-A-7-130007.

[0037]

As described above, the electrostatic actuator according to the present invention employs a structure in which a sealing material accumulation portion for accumulating a sealing adhesive is formed in a passage communicating with a vibration chamber relatively displaced by static electricity. ing. In the electrostatic actuator, the interval between the vibration chambers is made as small as possible in order to make the electrostatic force generated in the vibration chambers that are relatively displaced sufficiently large. According to the present invention, by forming a plurality of sealing material reservoirs in the passage, not only can the length of the unsealed portion be easily controlled, but also the intrusion of the sealing adhesive can be ensured at the sealing material reservoir. The sealing adhesive does not enter the vibration chamber.

Further, the present invention has the advantage that the following characteristics between the actuators are made constant in the electrostatic actuator. This is because the penetration length of the sealing adhesive becomes constant between the actuators by forming the sealing material reservoir, and the capacitance of the actuators becomes equal between the actuators. As a result, when the present invention is applied to an ink jet head, the ink ejection characteristics are equal among the actuators, and high-quality printing can be performed.

Further, there is an advantage that an incomplete sealing margin is eliminated, the passage can be made as short as possible, and the electrostatic actuator can be further miniaturized.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an ink jet head to which the present invention is applied.

FIG. 2 is a plan view of the inkjet head of FIG.

FIG. 3 is an enlarged view of the inkjet head in which the vicinity of a passage in FIG. 2 is enlarged.

FIG. 4 is an enlarged view of the ink jet head in which the vicinity of a passage when there is no sealing material reservoir is enlarged.

FIG. 5 is an enlarged view of the inkjet head in which the vicinity of a passage in FIG. 2 is enlarged.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet head 2 Silicon substrate 3 Nozzle plate 4 Glass substrate 5 Ink chamber 51 Bottom wall of ink chamber (common electrode, diaphragm) 6 Common ink chamber 7 Ink supply path 8 Depression 9 Passage 10 Segment electrode 11 Nozzle 12 Ink supply port 16 Vibration chamber 21 Voltage applying means 22 Common electrode terminal 24 Terminal part 93 Sealing adhesive 94 Sealing material reservoir

Claims (7)

[Claims] 1. A vibrating plate, a counter electrode disposed to face the vibrating plate, and a vibrating chamber formed by the vibrating plate and the counter electrode, one communicating with the vibrating chamber and the other being sealed. An electrostatic actuator having a passage hermetically sealed by a stopper, wherein a sealing material accumulation portion in which the width of the passage is formed is formed on the vibration chamber side of the passage. Electrostatic actuator. 2. The electrostatic actuator according to claim 1, wherein the encapsulant reservoir is formed of a glass substrate. 3. A plurality of the sealing material reservoirs in the passage according to claim 1, wherein a length of a sealing margin hermetically sealed by the sealing material of the passage is 1 mm or more. An electrostatic actuator characterized by being performed. 4. The sealing material reservoir according to claim 1, wherein the sealing material reservoir is disposed in the passage so that a distance from the sealing material reservoir to the vibration chamber is 0.2 mm or more. Electrostatic actuator. 5. The electrostatic actuator according to claim 1, wherein the sealing material is an epoxy-based low-temperature thermosetting type and has a viscosity of 20 to 50 Pa · s. 6. The electrostatic actuator according to claim 1, wherein the height of the passage is 0.05 to 0.5 μm. 7. A nozzle, an ink flow passage communicating with the nozzle and partially forming the vibration plate, an opposing electrode disposed to face the vibration plate with a certain gap, and one of the vibration plates. An ink jet head having a vibrating chamber defining one surface and containing the counter electrode, and a passage having one communicating with the vibrating chamber and the other being hermetically sealed by a sealing material; An encapsulating material reservoir formed on the vibration chamber side of the passage.