JP2011000756A - Electrostatic actuator, driving method therefor, liquid droplet ejecting head including the electrostatic actuator and liquid droplet ejecting device equipped therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrostatic actuator capable of controlling displacing operation of a diaphragm so that excluded volume may not change suddenly, a driving method therefor, a liquid droplet ejecting head mounted with the electrostatic actuator and a liquid droplet ejecting device mounted with the liquid droplet ejecting head.SOLUTION: An area of a fixed electrode 5 opposed to the diaphragm 4 is formed in a stair shape so that a gap may be larger from one end to the other end in a longitudinal direction of the area and constituted of three stages 5c to 5e.

Description

  The present invention relates to an electrostatic actuator of an electrostatic drive type, a driving method thereof, a droplet discharge head provided with the electrostatic actuator, and a droplet discharge apparatus equipped with the droplet discharge head.

  As an ink ejection method in an ink jet recording apparatus, a so-called electrostatic driving method using electrostatic force as a driving unit is known. The electrostatic drive type ink jet recording apparatus is a fixed electrode for a diaphragm by applying a voltage to generate an electrostatic force between a diaphragm that is a movable electrode and a fixed electrode that is positioned opposite to the gap. An operation of releasing the voltage from the stationary electrode of the diaphragm by releasing the voltage is performed, and ink is ejected from the nozzle hole using a pressure change generated thereby. Therefore, the vibration plate and the fixed electrode act as an electrostatic actuator that varies the pressure of the discharge chamber in which ink is stored, and the droplet discharge head is configured by mounting the electrostatic actuator.

  In such electrostatic actuators or droplet discharge heads, the density has been increasing recently, and the width of the diaphragm has been reduced with the increase in density. In this case, the volume of the portion recessed toward the gap due to the displacement of the diaphragm from the initial state of the diaphragm (hereinafter referred to as “excluded volume”) is reduced, and the amount of ink discharged is also reduced. In order to solve this problem, it is conceivable to widen the gap and secure an excluded volume of ink. However, if the gap between the diaphragm and the counter electrode is widened, the driving voltage for driving the diaphragm is increased. There was a problem that had to be done.

In order to solve such a problem, as a droplet discharge head for lowering the driving voltage, the opposing wall facing the diaphragm is formed in a stepped shape, and the diaphragm portion located in the small gap portion is opposed to it. By applying a driving voltage for contacting the wall, the diaphragm portion located in the small gap portion is easily elastically displaced toward the opposing wall, and this displacement is located in the large gap portion. Some diaphragms are attracted to and closely adhered to the opposing wall side by the Coulomb force as a whole (see, for example, Patent Document 1).
In addition, the short side of the gap is concave, and the individual electrodes are formed in a staircase shape so that the step of the groove portion formed in the staircase shape becomes smaller from the end of the groove portion toward the center portion. There is an electrostatic actuator that can be formed and brought into contact with the counter electrode with a driving voltage at which the diaphragm and the counter electrode are in contact with each other at the end of the groove where the gap is the smallest (see FIG. For example, see Patent Document 2 and Patent Document 3).

Japanese Patent Laid-Open No. 9-39235 (page 5-6, FIG. 1) JP 2000-318155 A (5th page, FIG. 5) JP 2006-289944 A (page 9-11, FIG. 3-4)

  However, in any of the droplet discharge head according to Patent Document 1 and the electrostatic actuators according to Patent Document 2 and Patent Document 3, it is not possible to reduce the drive voltage for bringing the diaphragm and the counter electrode into contact with each other. However, the displacement operation of the diaphragm cannot be controlled, and the acceleration operation causes the ink flow in the discharge chamber to be disturbed, resulting in a decrease in discharge performance. It was.

  The present invention has been made to solve the above problems, and an electrostatic actuator capable of controlling the displacement operation of the diaphragm so that the excluded volume does not change rapidly, and a driving method thereof Another object of the present invention is to obtain a droplet discharge head equipped with the electrostatic actuator and a droplet discharge device equipped with the droplet discharge head.

The electrostatic actuator according to the present invention applies a driving voltage between a fixed electrode formed on a substrate, a movable electrode disposed opposite to the fixed electrode with a predetermined gap therebetween, and the fixed electrode and the movable electrode. Drive control means for generating a displacement in the movable electrode by generating an electrostatic force, and the fixed electrode is formed by a plurality of steps having a step shape with different gap sizes. On the other hand, the excluded volume when the opposed movable electrodes are in contact with each other is the same in each stage.
According to the present invention, it is possible to control the excluded volume so that it does not change suddenly in the process in which the movable electrode is in contact with each stage. It is also possible to suppress variations in the behavior of the movable electrode due to.

Further, the electrostatic actuator according to the present invention is characterized in that the plurality of steps of the fixed electrode are formed such that a gap increases from one end to the other end in the longitudinal direction of the region of the fixed electrode facing the movable electrode. It is what.
According to the present invention, since the gap that is one end of the region of the fixed electrode that faces the movable electrode can be made to contact in order from the portion that has the smallest gap that is the other end, the excluded volume is reduced. It can be controlled so that it does not change rapidly.

Further, the electrostatic actuator according to the present invention is characterized in that the plurality of steps of the fixed electrode are formed such that the gap increases from the longitudinal ends to the center of the fixed electrode region facing the movable electrode. To do.
According to the present invention, since the gap that is the opposite end of the region of the fixed electrode that faces the movable electrode can be sequentially contacted from the portion that has the largest gap that is the center of the region, the excluded volume Can be controlled so as not to change rapidly.

Further, in the electrostatic actuator according to the present invention, the plurality of stages in the fixed electrode apply a driving voltage that is less than the voltage value of the minimum driving voltage for the drive control means to contact a certain stage in the plurality of stages. When the step corresponding to the next smallest gap of the gap corresponding to the specific step abuts, the specific step is formed to have a level difference that does not come into contact with the contact operation. It is what.
According to the present invention, an operation in which a specific step in a plurality of steps abuts prevents an operation in which a step corresponding to the next largest gap corresponds to the size of the gap corresponding to the specific step, and an excluded volume. The variation of the change of the can be suppressed.

Further, the electrostatic actuator driving method according to the present invention includes a step by repeatedly applying a rising portion of the voltage value and a holding portion that holds the voltage value increased by the rising between the fixed electrode and the movable electrode. A drive voltage having a shape voltage waveform is applied.
According to the present invention, by applying a staircase-shaped drive voltage, the movable electrode can be brought into contact with each step of the fixed electrode formed in a staircase step shape, and a sudden change in the excluded volume is controlled. be able to.

In the driving method of the electrostatic actuator according to the present invention, the number of voltage steps in the driving voltage having a stepped voltage waveform and the number of steps having different gap sizes in the plurality of steps of the fixed electrode are the same. It is characterized by.
According to the present invention, it becomes a drive voltage waveform in which the movable electrode is brought into contact with each step in the fixed electrode formed in a stepped shape, and a sudden change in the excluded volume can be controlled.

Further, in the driving method of the electrostatic actuator according to the present invention, the number of voltage stages in the driving voltage having a staircase-shaped voltage waveform is n, and the holding unit constituting the driving voltage having the staircase-shaped voltage waveform is used. The voltage values are set to E ₁ , E ₂ ,..., E _n−1 and E _n respectively from the application time earlier, and the region of the movable electrode facing the step in the plurality of steps of the fixed electrode is the step. the voltage value of the minimum driving voltage required to contact, EL _1, EL ₂ each from those corresponding to the stage the gap is small, ..., when the EL _n-1 and EL _n, EL ₁ <E ₁ <EL ₂ , EL ₂ <E ₂ <EL ₃ ,..., EL _n−1 <E _n−1 <EL _n , and EL _n <E _n. is there.
According to the present invention, the movable electrode can be reliably brought into contact with each step in the fixed electrode formed in the stepped shape.

The driving method of the electrostatic actuator according to the present invention, the displacement volume on the vertical axis, the graph of the time and the horizontal _{axis, E 1, E 2, ···} , EL n-1 and E _n each voltage When a driving voltage of a value is applied, the line connecting points on the graph determined by the time and the excluded volume when the contact state between the fixed electrode and the movable electrode is stabilized is a straight line. .
According to the present invention, it is possible to displace the excluded volume linearly, and it is possible to further suppress an abrupt change in the excluded volume.

In addition, a liquid droplet ejection head according to the present invention includes the electrostatic actuator described above.
According to the present invention, it is possible to obtain a droplet discharge head with improved discharge performance by suppressing a sudden change in the excluded volume and suppressing the disturbance of the ink flow in the discharge chamber.

In the droplet discharge head according to the present invention, the drive control unit repeatedly applies the rising portion of the voltage value and the holding portion that holds the voltage value increased by the rising between the fixed electrode and the movable electrode. Thus, a drive voltage that has a stepped voltage waveform is applied.
According to the present invention, by applying a staircase-shaped drive voltage, the movable electrode can be brought into contact with each step of the fixed electrode formed in a staircase step shape, and a sudden change in the excluded volume is controlled. A droplet discharge head that can be obtained can be obtained.

Further, in the liquid droplet ejection head according to the present invention, the drive control means has the same number of voltage steps in the drive voltage having the stepped voltage waveform and the number of steps having different gap sizes in the plurality of steps of the fixed electrode. A drive voltage is applied so as to be.
According to the present invention, it is possible to obtain a liquid droplet ejection head that has a driving voltage waveform in which a movable electrode is brought into contact with each step of a fixed electrode formed in a stepped shape, and can control a sudden change in excluded volume. Can do.

Further, the droplet discharge head according to the present invention has n voltage steps in the drive voltage having a staircase-shaped voltage waveform applied by the drive control means, and has a staircase-shaped voltage waveform applied by the drive control means. The voltage value in the holding part constituting the driving voltage is set to E ₁ , E ₂ ,..., E _n-1 and E _n from the one having the earlier application time, respectively, and the movable electrode facing the plurality of stages of the fixed electrode When the minimum drive voltage value required for the region to abut the step is EL ₁ , EL ₂ ,..., EL _n−1 and EL _n from those corresponding to the step with a small gap, respectively. The drive control means satisfy EL ₁ <E ₁ <EL ₂ , EL ₂ <E ₂ <EL ₃ ,..., EL _n−1 <E _n−1 <EL _n , and EL _n <E _n. Thus, a drive voltage is applied.
According to the present invention, it is possible to obtain a droplet discharge head that can reliably contact a movable electrode for each step in a fixed electrode formed in a stepped shape.

The liquid drop discharge head of the present invention, the drive control means, the displacement volume on the vertical axis, the graph of the time and the horizontal _{axis, E 1, E 2, ···} , EL n-1 and E _n When applying a driving voltage of each voltage value, the driving voltage is set so that the line connecting the points on the graph determined by the time and the excluded volume when the contact state between the fixed electrode and the movable electrode is stabilized becomes a straight line. It is characterized by applying.
According to the present invention, it is possible to obtain a liquid droplet ejection head capable of displacing the excluded volume linearly and further suppressing a rapid change in the excluded volume.

In addition, a droplet discharge apparatus according to the present invention is characterized by mounting the above-described droplet discharge head.
According to the present invention, it is possible to obtain a droplet discharge device with improved discharge performance by suppressing a sudden change in the excluded volume and suppressing the disturbance of the ink flow in the discharge chamber.

It is a disassembled external appearance perspective view of the inkjet head 51 which concerns on Embodiment 1 of this invention. It is a cross-sectional view of the inkjet head 51 which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement at the time of the drive voltage application in the inkjet head 51 which concerns on Embodiment 1 of this invention. It is a figure which shows the displacement of the drive voltage waveform and exclusion volume in the operation | movement at the time of the drive voltage application shown by FIG. It is a figure explaining the relationship between the exclusion volume when the diaphragm contact | abuts to each step | level in a fixed electrode, and its displacement. It is a cross-sectional view of the inkjet head 51 which concerns on Embodiment 2 of this invention. It is a figure which shows the operation | movement at the time of the drive voltage application in the inkjet head 51 which concerns on Embodiment 2 of this invention. It is an external view which shows an example of the droplet discharge apparatus which concerns on Embodiment 3 of this invention. It is a figure which shows an example of the main structure means of the droplet discharge apparatus which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is an exploded external perspective view of an ink jet head 51 according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of the ink jet head 51.
As shown in FIGS. 1 and 2, the ink jet head 51 shown in the present embodiment is a laminated structure formed by bonding three substrates. The three substrates are a nozzle substrate 1 in which a plurality of nozzle holes 11 are provided at a predetermined pitch, a cavity substrate 2 in which an ink flow path is formed independently for each nozzle hole 11, and each ink. This is an electrode substrate 3 in which a fixed electrode 5 is disposed so as to face a diaphragm 4 that is a movable electrode that constitutes a bottom wall of a discharge chamber 21 provided in a flow path.
The inkjet head 51 corresponds to the “droplet ejection head” of the present invention.

(Nozzle substrate 1)
The nozzle substrate 1 is made of a single crystal silicon substrate, and includes a nozzle hole 11 that is communicated with the discharge chamber 21 of the cavity substrate 2 by etching and is formed to penetrate the nozzle substrate 1 perpendicularly. Yes. The nozzle hole 11 can improve the straightness of the ink droplet by being configured in two stages of the ejection port portion having a small diameter and the introduction port portion having a larger diameter. The nozzle substrate 1 is bonded to the cavity substrate 2 by adhesive bonding or direct bonding with an adhesive using an epoxy resin or the like. As shown in FIG. 1, the nozzle holes 11 are formed in two rows, and each head has a head portion on each side, but this is not a limitation. Instead, the head portion may be configured in one row, and the number of nozzle holes 11 is not limited.

(Cavity substrate 2)
The cavity substrate 2 is made of, for example, a single crystal silicon substrate having a plane orientation of (110), and grooves or recesses serving as a plurality of ink flow paths are formed on the surface. The groove or recess serving as the ink flow path is formed by performing boron diffusion on the bottom surface side of the cavity substrate 2 to form an etching stop layer, and performing photolithography and wet etching. A discharge chamber 21 is formed by the bottom surface of the nozzle substrate 1. In the discharge chamber 21 formed in this way, the bottom portion is the diaphragm 4 which is a movable electrode formed with a very thin thickness (for example, 2 μm) with high accuracy as a boron diffusion layer. In addition, a concave reservoir 23 that communicates in common is formed in each flow path.

(Electrode substrate 3)
Since the electrode substrate 3 is bonded to the cavity substrate 2 by anodic bonding, borosilicate glass having a thermal expansion coefficient close to that of silicon is generally used in order to ensure bonding strength without peeling. . On this electrode substrate 3, a fixed electrode 5 (thickness is, for example, 0.1 μm) generally made of ITO (Indium Tin Oxide) is formed by sputtering, for example. . Each fixed electrode 5 is formed at the bottom in a recess 31 that is partitioned by etching at a position facing the diaphragm 4. By forming the recess 31, the diaphragm 4 and the fixed electrode 5 are disposed to face each other with a predetermined gap (hereinafter referred to as a gap) G. As shown in FIG. 2, the region of the concave portion 31 facing the diaphragm 4 in the fixed electrode 5 is the other end in the longitudinal direction of the region (from the nozzle hole 11 side in the nozzle substrate 1 in FIG. 2). It is formed in a staircase shape so that the gap increases toward the end, and is constituted by three steps 5c to 5e. In addition, one or a plurality of ink supply holes 32 are formed in the electrode substrate 3. The ink supply holes 32 are formed by grinding or microblasting, and are formed through the bottom of the cavity substrate 2 so as to communicate with the reservoir 23 described above. The ink supply hole 32 is connected to an ink tank (not shown). As shown in FIG. 2, the region of the fixed electrode 5 facing the diaphragm 4 has a gap that increases from one end on the nozzle hole 11 side in the longitudinal direction of the region toward the other end. However, the present invention is not limited to this, and the gap may be increased from the other end toward one end on the nozzle hole 11 side.

(Sealing agent 28)
The open end of the gap G formed between the diaphragm 4 and the fixed electrode 5 was deposited with an oxide film such as epoxy resin or TEOS (Tetraethoxysilane) by CVD (Chemical Vapor Deposition) method. It is hermetically sealed by a sealing agent 28 formed of a thing. Accordingly, moisture, dust and the like can be prevented from entering the gap G, and the reliability of the inkjet head 51 can be kept high.

(Drive control circuit 41)
As shown in FIGS. 1 and 2, the rear end portions of the cavity substrate 2 and the electrode substrate 3 are electrode extraction portions 34 opened by etching. The fixed electrode 5 formed on the electrode substrate 3 has a lead portion 5 a and a terminal portion 5 b, and the terminal portion 5 b is formed so as to be exposed at the electrode extraction portion 34. A common electrode 26 made of a metal film is formed on one side or both sides of the rear end portion of the cavity substrate 2. A drive control circuit 41 such as a driver IC for applying a drive voltage between the diaphragm 4 and the fixed electrode 5 as a drive means for the electrostatic actuator includes a terminal portion 5b of each fixed electrode 5 and a common electrode 26. For example, it is bonded using a conductive adhesive. Here, it is assumed that the electrostatic actuator includes at least the diaphragm 4, the fixed electrode 5, and the drive control circuit 41.
The drive control circuit 41 corresponds to the “drive control means” of the present invention.

(Outline of operation of inkjet head 51)
The ink is filled without generating bubbles until the reservoir 23 and the discharge chamber 21 provided in the cavity substrate 2 and the tip of the nozzle hole 11 of the nozzle substrate 1 are formed. Ink flows in the direction shown. When printing is performed, the drive control circuit 41 applies a driving voltage between the diaphragm 4 and the fixed electrode 5 to generate an attractive force due to electrostatic force, and the diaphragm 4 moves toward the fixed electrode 5. The negative pressure is generated in the discharge chamber 21 by being pulled and bent and coming into contact with the fixed electrode 5. As a result, the ink in the reservoir 23 is sucked into the discharge chamber 21.
When the driving voltage is released, the diaphragm 4 is detached from the fixed electrode 5, and the ink is pushed out from the nozzle hole 11 by the restoring force, and the pushed ink droplet is directed to the recording paper (not shown). Discharged.

(Drive voltage application operation in the inkjet head 51)
FIG. 3 is a diagram showing an operation when a drive voltage is applied in the inkjet head 51 according to the first embodiment of the present invention, and FIG. 4 is a diagram showing a drive voltage waveform and displacement of the excluded volume. Hereinafter, the operation at the time of applying the drive voltage between the diaphragm 4 and the fixed electrode 5 will be described with reference to FIGS. 3 and 4.
First, the drive control circuit 41 raises the drive voltage, applies the drive voltage to a voltage value E1 (for example, 10 V), and holds the voltage value E1 for a predetermined time. Assuming that the time when the drive voltage reaches the voltage value E1 is t11 (for example, 0.5 μsec), at the time t1 after this time t11, the portion of the diaphragm 4 facing the step 5c of the fixed electrode 5 becomes the step 5c. It contacts and it will be in the state shown by Fig.3 (a). Exclusion volume V1 arises by contact at this time.

  Next, the drive control circuit 41 raises the drive voltage from the voltage value E1, applies the drive voltage to the voltage value E2 (for example, 15 V), and holds the voltage value E2 for a predetermined time. Assuming that the time when the drive voltage reaches the voltage value E2 is t21 (for example, 2 μsec), at time t2 after this time t21, the portion of the diaphragm 4 facing the step 5d of the fixed electrode 5 contacts the step 5d. The state shown in FIG. The excluded volume V2 is further generated by the contact of the portion of the diaphragm 4 facing the stage 5d with the step 5d, and the excluded volume of the entire diaphragm 4 is V1 + V2.

  Further, the drive control circuit 41 raises the drive voltage from the voltage value E2, applies the drive voltage so as to become the voltage value E3 (for example, 25 V), and holds the voltage value E3 for a predetermined time. Assuming that the time when the drive voltage reaches the voltage value E3 is t31 (for example, 6 μsec), the portion of the diaphragm 4 facing the step 5e of the fixed electrode 5 contacts the step 5e at time t3 after the time t31. The state shown in FIG. The excluded volume V3 is further generated by the contact of the portion of the diaphragm 4 facing the stage 5e with the step 5e, and the excluded volume of the entire diaphragm 4 is V1 + V2 + V3.

  Then, when the drive control circuit 41 releases the application state of the drive voltage having the voltage value E3, the diaphragm 4 is detached from the fixed electrode 5, and the ink is ejected from the nozzle hole 11 by the restoring force. Discharged.

  By repeating the rise of the drive voltage and the holding of the voltage value as in the above operation, the drive voltage becomes a stepped voltage waveform as shown in FIG. Further, in each of the held voltage values E1 to E3, the diaphragm 4 abuts against the steps 5c to 5e of the fixed electrode 5, respectively, so that the number of steps of the voltage waveform of the stepped drive voltage (FIG. 4). 3) and the number of steps of the fixed electrode 5 formed in a staircase shape, that is, the number of steps having different gap sizes (three in FIG. 3) are the same. Further, in the graph showing the displacement of the excluded volume with time as the horizontal axis and the excluded volume at each time as the vertical axis as shown in FIG. 4B, on the graph determined at time t1 when the excluded volume becomes V1. The point A on the graph determined at time t2 when the excluded volume becomes V1 + V2 and the point C on the graph determined at time t3 when the excluded volume becomes V1 + V2 + V3 are on the ideal excluded volume displacement straight line 101 and are actually The displacement of the excluded volume becomes an excluded volume displacement curve 102 passing through points A to C. At this time, the drive control circuit 41 adjusts the times t11, t21, and t31 so as to apply the drive voltage so that the points A to C are on the ideal excluded volume displacement straight line 101 as described above. Furthermore, assuming that the minimum drive voltage voltage values for the diaphragm 4 to come into contact with the stages 5c to 5e are EL1, EL2, and EL3, the drive control circuit 41 performs the following drive voltage application operation. Voltage values E1 to E3 that satisfy the expressions (1) to (3) are applied.

EL1 <E1 <EL2 (1)
EL2 <E2 <EL3 (2)
EL3 <E3 (3)

  The drive control circuit 41 applies the drive voltage satisfying the above formulas (1) to (3), so that the diaphragm 4 is fixed to the fixed electrode in each of the voltage values E1 to E3 that are held. 5 can be reliably brought into contact with the steps 5c to 5e. Further, for example, the step between the step 5c and the step 5d is driven by the operation when the drive control circuit 41 applies a drive voltage having the voltage value E1 and the diaphragm 4 contacts the step 5c in the fixed electrode 5. Thus, it is configured with a size sufficient to prevent it from coming into contact with the step 5d. The same applies to the step between the step 5d and the step 5e.

  FIG. 5 is a diagram for explaining the relationship between the displacement volume and its displacement when the diaphragm comes into contact with each step of the fixed electrode.

FIG. 5A is a diagram illustrating displacement of the excluded volume by the diaphragm when the fixed electrode is not formed in a staircase shape.
Here, at time t1a, the diaphragm is completely in contact with the fixed electrode, the excluded volume at that time is V1a, and the point determined by the time t1a and the excluded volume V1a is A ′.
The electrostatic force generated when a driving voltage is applied between the diaphragm and the fixed electrode is inversely proportional to the square of the size of the gap, so the excluded volume increases, that is, the closer the diaphragm is to the fixed electrode. As a result of increasing the electrostatic force and increasing the speed of the diaphragm, the displacement curve of the actual displacement volume is a displacement volume displacement greatly curved with respect to the ideal displacement volume displacement straight line 101 as shown in FIG. A curve 102a is obtained.

FIG. 5B shows an excluded volume when the fixed electrode is formed in a three-step staircase shape like the fixed electrode 5 in the inkjet head 51 according to the present embodiment, but the excluded volume at each step is different. FIG.
Here, the time when the gap is the smallest is completely abutted at time t1b, the excluded volume at that time is V1b, and the time when the gap is the next largest is completely abutted at time t2b, and is abutted on that stage at that time. The excluded volume due to this is V2b, and at time t3b, it completely contacts the step with the largest gap, and the excluded volume due to contact with that step at that time is V3b. The point determined by the time t1b and the excluded volume V1b is A ″, the point determined by the time t2b and the entire excluded volume V1b + V2b at that time is B ″, and the time t3b and the entire excluded volume V1b + V2b + V3b at that time The point determined by is C ″. Here, as shown in FIG. 5B, it is assumed that the staircase-shaped fixed electrode is formed so that the excluded volume V3b is larger than the excluded volumes V1b and V2b.
As shown in FIG. 5B, the points A ″ to C ″ are all on the ideal excluded volume displacement straight line 101, but the excluded volume V3b is larger than the excluded volumes V1b and V2b. The time from time t2b to time t3b is also increased and is greatly affected by the increase in the speed of the diaphragm, and the displacement curve of the actual displacement volume from the time t2b to time t3b is the ideal displacement volume displacement straight line 101. The displacement volume displacement curve 102b is greatly curved.

FIG. 5C is a diagram showing a displacement curve of the diaphragm 4 of the ink jet head 51 according to the present embodiment. Until the time t3 in the diagram showing the displacement of the excluded volume shown in FIG. 4B above. It is the figure which extracted and showed the part of.
As shown in FIG. 5C, in the present embodiment, the staircase-shaped fixed electrode 5 is formed so that the excluded volumes V1 to V3 are substantially the same, that is, V1≈V2≈V3. Therefore, the width in the longitudinal direction of the fixed electrode 5 of each of the steps 5a, 5b and 5c facing the diaphragm 4 shown in FIG. 2 decreases in the order of the steps 5a, 5b and 5c. At this time, as described above, since the points A to C are on the ideal excluded volume displacement straight line 101, the time from the displacement start time of the diaphragm 4 to time t1 (hereinafter referred to as T1), time t1 to time The time t2 (hereinafter referred to as T2) and the time t2 to time t3 (hereinafter referred to as T3) are substantially the same, and T1≈T2≈T3. Therefore, the influence of the increase in the speed of the diaphragm 4 on the excluded volume displacement curve 102 shown in FIG. It becomes smaller than the excluded volume displacement curve 102a shown in FIG. 5A and the excluded volume displacement curve 102b shown in FIG. Thereby, the excluded volume by the diaphragm 4 can be displaced linearly, and the rapid change of the excluded volume can be further suppressed.

(Effect of Embodiment 1)
As described above, the fixed electrode 5 is formed in a stepped shape having a plurality of steps, and the diaphragm 4 is movable in each step by making the excluded volume the same by contacting each step. It is possible to control the excluded volume so as not to change abruptly in the process in which the electrodes are in contact with each other, and it is possible to suppress disturbance of the ink flow in the discharge chamber 21, and Variations in the behavior of the diaphragm 4 due to variations in dimensions and the like can also be suppressed.
Further, the region of the fixed electrode 5 that faces the diaphragm 4 is formed so that the gap increases from one end to the other end in the longitudinal direction of the region. Since the gap that is one end of the region can be contacted in order from the portion having the smallest gap that is the other end to the portion that has the largest gap, the exclusion volume can be controlled so as not to change suddenly. .
Further, the stepped step formed in the fixed electrode 5 is brought into contact with the next step corresponding to the gap next to the gap at the specific step as the diaphragm 4 comes into contact with the specific step. Since it is formed to such an extent that it does not occur, it is possible to suppress variation in the change in the excluded volume.
Also, as shown in FIG. 4A, the drive control circuit 41 drives in a stepped voltage waveform by repeating the rise of voltage and holding of the voltage value between the diaphragm 4 and the fixed electrode 5. Since a voltage is applied, the diaphragm 4 can be brought into contact with each step of the fixed electrode 5 formed in a stepped shape, and a sudden change in the excluded volume can be controlled.
In addition, since the number of voltage steps in the staircase-shaped driving voltage is the same as the number of steps of the fixed electrode 5 formed in the staircase shape, that is, the number of steps having different gap sizes, the fixed electrode formed in the staircase shape 5 is a drive voltage waveform for bringing the diaphragm 4 into contact with each stage in step 5, and a sudden change in the excluded volume can be controlled.
Further, the drive control circuit 41 applies the drive voltage satisfying the above-described formulas (1) to (3), so that the diaphragm 4 is placed on each stage of the fixed electrode 5 according to the voltage value held in the drive voltage. Can be reliably brought into contact with each other.
Further, in the graph in which the drive control circuit 41 has the excluded volume as the vertical axis and the time as the horizontal axis, the contact state between the fixed electrode 5 and the diaphragm 4 by applying the voltage held in the staircase-shaped drive voltage. By applying a driving voltage so that the line connecting the points on the graph determined by the time and the excluded volume when each becomes stable, the excluded volume can be displaced linearly, Changes can be further suppressed.

In the drive voltage application operation by the drive control circuit 41, as shown in FIG. 4B and FIG. 5C, the points A to C are on the ideal excluded volume displacement straight line 101. Although the line connecting points A to C is a straight line, it is not necessarily strictly a straight line, and the above effect can be obtained if the line is a curve approximated to a straight line.
In addition, the fixed electrode 5 of the inkjet head 51 according to the present embodiment is formed in a staircase shape with three steps 5c to 5e, but is not limited to this, and has a staircase shape with a different number of steps. It may be formed. In this case, the number of steps of the voltage waveform of the staircase-shaped drive voltage applied between the diaphragm 4 and the fixed electrode 5 by the drive control circuit 41 is the same as the number of steps of the fixed electrode 5 in the staircase shape. The fixed electrode 5 is formed so that the excluded volume due to contact with each stage of the fixed electrode 5 is substantially the same, and the time of contact with each stage in the graph showing the displacement of the excluded volume by the diaphragm 4 and its time The application time of the drive voltage by the drive control circuit 41 is adjusted so that the line connecting the points determined by the entire excluded volume at the time becomes a substantially straight line, and the drive control circuit 41 further adjusts the above-described formulas (1) to ( The drive voltage may be applied so as to satisfy the condition according to 3).

Embodiment 2. FIG.
FIG. 6 is a cross-sectional view of the inkjet head 51 according to Embodiment 2 of the present invention. Hereinafter, in the present embodiment, description will be made focusing on differences from the configuration and operation in the first embodiment.
As shown in FIG. 6, the region of the fixed electrode 5 of the electrode substrate 3 facing the diaphragm 4 is formed in a staircase shape so that the gap increases from both ends in the longitudinal direction toward the center. , Stages 5f to 5j. Further, the size of the gap with the diaphragm 4 corresponding to each of the steps 5f and 5j is the same, and the size of the gap with the diaphragm 4 corresponding to each of the steps 5g and 5i is also configured to be the same. ing.

(Drive voltage application operation in the inkjet head 51)
FIG. 7 is a diagram showing an operation when a drive voltage is applied in the inkjet head 51 according to Embodiment 2 of the present invention.
7A is a diagram showing a state in which the diaphragm 4 is in contact with the step 5f and the step 5j having the same gap size with the diaphragm 4, and the diaphragm 4 has the step 5f. V1a is an excluded volume caused by abutting on the plate 5, and V1b is an excluded volume caused when the diaphragm 4 is brought into contact with the step 5j. FIG. 7B is a view showing a state in which the diaphragm 4 is in contact with the step 5g and the step 5i having the same gap size with the diaphragm 4 in addition to the state of FIG. 7A. The excluded volume due to the diaphragm 4 abutting against the step 5g is V2a, and the excluded volume due to the diaphragm 4 abutting against the step 5i is V2b. FIG. 7C is a view showing a state in which the diaphragm 4 is in contact with the step 5h in addition to the state of FIG. 7B, and an excluded volume due to the contact of the diaphragm 4 with the step 5h. Is V3.
Here, the sum of the excluded volume V1a and the excluded volume V1b shown in FIG. 7A is V1, the sum of the excluded volume V2a and the excluded volume V2b shown in FIG. The stage 5j corresponds to the stage 5c in the first embodiment, the stage 5g and the stage 5i correspond to the stage 5d in the first embodiment, and the stage 5h corresponds to the stage 5e in the first embodiment. Shall. At this time, the drive control circuit 41 in the present embodiment is driven between the diaphragm 4 and the fixed electrode 5 by the same operation as the drive voltage application operation described in FIGS. 4 and 5 in the first embodiment. Apply voltage.

(Effect of Embodiment 2)
With the above configuration and operation, the same effects as those of the inkjet head 51 according to Embodiment 1 can be obtained. Moreover, about the fixed electrode 5 which concerns on Embodiment 1, the area | region which opposes the diaphragm 4 in the fixed electrode 5 is formed so that a gap may become large toward the other end from the longitudinal direction of the area | region. On the other hand, for the fixed electrode 5 according to the present embodiment, the region of the fixed electrode 5 facing the diaphragm 4 is formed so that the gap increases from both ends of the region toward the center. Since the gap which is the both ends of the region of the fixed electrode 5 facing the diaphragm 4 can be abutted in order from the portion where the gap which is the center of the region is the largest, the excluded volume changes rapidly. It can be controlled so that it does not.

Embodiment 3 FIG.
(Configuration of the droplet discharge device 201)
FIG. 8 is an external view showing an example of a droplet discharge device according to Embodiment 3 of the present invention, and FIG. 9 is a diagram showing an example of main constituent means of the droplet discharge device.
A droplet discharge device 201 shown in FIG. 8 is a so-called serial type device intended for printing by an ink jet method. As shown in FIG. 9, the droplet discharge device 201 includes at least a drum 202 on which the print paper 208 is supported, and the first embodiment in which ink is discharged onto the print paper 208 to perform printing. The inkjet head 51 according to the second embodiment, an ink supply means (not shown) for supplying ink to the inkjet head 51, and a paper press roller 203 provided in parallel to the axial direction of the drum 202 are provided. Yes. Furthermore, the droplet discharge device 201 includes an inkjet head 51, a feed screw 204 provided in parallel with the axial direction of the drum 202, a motor 206 that rotates the drum 202 via the belt 205, and print data and control. A print control means 207 for rotating the feed screw 204 and the motor 206 based on the signal is provided.

(Operation of the droplet discharge device 201)
The print paper 208 placed on the drum 202 is pressed against the drum 202 by the paper press roller 203 and held. Next, the print control means 207 rotates the motor 206 to rotate the drum 202 via the belt 205, and feeds the print paper 208 in the rotation direction of the drum 202. At the same time, the print control unit 207 rotates the feed screw 204 to move the ink jet head 51 in the axial direction of the drum 202, and ink is discharged from the nozzle holes 11 in the ink jet head 51 based on the print data and the control signal. The ink droplets are ejected and ink droplets are landed on the print paper 208 to perform printing.

  As described above, the droplet discharge device 201 according to the present embodiment includes the inkjet head 51 according to the first or second embodiment, thereby suppressing a rapid change in the excluded volume. It is possible to obtain a droplet discharge device that suppresses the disturbance of the ink flow in the discharge chamber and improves the discharge performance.

  In the present embodiment, ink is ejected onto the print paper 208 as the liquid ejected from the inkjet head 51, but the liquid ejected from the inkjet head 51 is not limited to ink. For example, a liquid containing a pigment for a color filter in an application for discharging to a substrate to be a color filter, a liquid containing a compound to be a light emitting element in an application for wiring on an OLED substrate, or an application for wiring on a substrate For example, a liquid containing a conductive metal may be discharged from a droplet discharge head provided in each device. In addition, it may be used for discharging dye such as cloth.

  As described above, the inkjet head 51 according to the first and second embodiments and the droplet discharge device 201 according to the third embodiment are a droplet discharge device such as a biochip manufacturing device or a liquid crystal color filter manufacturing device. It can also be applied to.

  1 nozzle substrate, 2 cavity substrate, 3 electrode substrate, 4 diaphragm, 5 fixed electrode, 5a lead part, 5b terminal part, 5c-5j stage, 11 nozzle hole, 21 discharge chamber, 23 reservoir part, 26 common electrode, 28 Sealant, 31 Concave part, 32 Ink supply hole, 34 Electrode extraction part, 41 Drive control circuit, 51 Ink jet head, 101 Ideal excluded volume displacement straight line, 102, 102a, 102b Excluded volume displacement curve, 201 Liquid droplet ejection device, 202 drum, 203 paper press roller, 204 feed screw, 205 belt, 206 motor, 207 print control means, 208 print paper.

Claims (14)

A fixed electrode formed on the substrate;
A movable electrode disposed opposite to the fixed electrode via a predetermined gap;
Drive control means for applying a drive voltage between the fixed electrode and the movable electrode to generate an electrostatic force to cause displacement of the movable electrode;
With
The fixed electrode is
Each step is formed by a plurality of steps having a step shape with different gap sizes,
The electrostatic actuator, wherein the excluded volume when the opposing movable electrode abuts on each of the plurality of stages is the same in each of the stages. The plurality of steps of the fixed electrode are formed such that the gap increases from one end to the other end in the longitudinal direction of the region of the fixed electrode facing the movable electrode. Electrostatic actuator. The plurality of steps of the fixed electrode are formed such that the gap increases from both ends in the longitudinal direction of the region of the fixed electrode facing the movable electrode toward the center. Electrostatic actuator. The plurality of stages in the fixed electrode may be configured such that the drive control unit applies the drive voltage that is less than a voltage value of the minimum drive voltage for a certain stage in the plurality of stages to contact the specific stage. When the step corresponding to the gap that is the next smallest in size of the gap corresponding to the contact is made, the specific step is formed to have a level difference that does not come into contact with the contact operation. The electrostatic actuator according to any one of claims 1 to 3. It is a drive method of the electrostatic actuator in any one of Claims 1-4, Comprising:
The drive voltage that forms a stepped voltage waveform by repeatedly applying a rising portion of the voltage value and a holding portion that holds the voltage value increased by the rising between the fixed electrode and the movable electrode. A method for driving an electrostatic actuator, comprising: applying the electrostatic actuator. 6. The number of steps of the voltage in the driving voltage having a stepped voltage waveform and the number of steps having different gap sizes in the plurality of steps of the fixed electrode are the same. Driving method of electrostatic actuator. The number of voltage stages in the drive voltage having a stepped voltage waveform is n,
E ₁ , E ₂ ,..., E _n-1 and E _n are respectively applied to the voltage values in the holding unit constituting the drive voltage having a staircase-shaped voltage waveform from the ones with earlier application time,
The voltage value of the minimum driving voltage required for the movable electrode region facing the step in the plurality of steps of the fixed electrode to be in contact with the step is changed from EL corresponding to the step having the small gap, respectively. ₁ , EL ₂ ,..., EL _n-1 and EL _n ,
EL ₁ <E ₁ <EL ₂ , EL ₂ <E ₂ <EL ₃ ,..., EL _n−1 <E _n−1 <EL _n , and EL _n <E _n Item 7. A driving method of an electrostatic actuator according to Item 6. In the graph in which the excluded volume is the vertical axis and the time is the horizontal axis, the fixed voltage is applied when the driving voltages of the voltage values of E ₁ , E ₂ ,..., EL _n−1 and E _n are applied. 8. The electrostatic actuator according to claim 7, wherein a line connecting the points on the graph determined by the time and the excluded volume when the contact state between the electrode and the movable electrode is stabilized is a straight line. Driving method.   A droplet discharge head comprising the electrostatic actuator according to claim 1. The drive control means forms a stepped voltage waveform by repeatedly applying a rising portion of the voltage value and a holding portion that holds the voltage value increased by the rising between the fixed electrode and the movable electrode. The droplet discharge head according to claim 9, wherein the drive voltage is applied. The drive control means is configured so that the number of voltage stages in the drive voltage having a staircase-shaped voltage waveform and the number of stages in which the gap sizes of the fixed electrodes are different are the same. The droplet discharge head according to claim 10, wherein the droplet discharge head is applied. The number of voltage steps in the drive voltage having a stepped voltage waveform applied by the drive control means is n,
E ₁ , E ₂ ,..., E _n-1 and voltage values in the holding unit constituting the drive voltage having the staircase-shaped voltage waveform applied by the drive control means, respectively, from the earlier application time. E _n
The voltage value of the minimum driving voltage required for the movable electrode region facing the step in the plurality of steps of the fixed electrode to be in contact with the step is changed from EL corresponding to the step having the small gap, respectively. ₁ , EL ₂ ,..., EL _n-1 and EL _n ,
The drive control means satisfies EL ₁ <E ₁ <EL ₂ , EL ₂ <E ₂ <EL ₃ ,..., EL _n−1 <E _n−1 <EL _n , and EL _n <E _n. The droplet discharge head according to claim 11, wherein the driving voltage is applied as described above. In the graph with the excluded volume as the vertical axis and the time as the horizontal axis, the drive control means represents the drive voltages of the voltage values of E ₁ , E ₂ ,..., EL _n−1 and E _n. When applying, the drive voltage is applied so that a line connecting the points on the graph determined by the time and the excluded volume when the contact state between the fixed electrode and the movable electrode is stabilized is a straight line. The droplet discharge head according to claim 12. A droplet discharge apparatus comprising the droplet discharge head according to claim 9.

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