JP2009081944A - Electrostatic actuator, droplet discharging head, and droplet discharging device having the head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the large displacement and the stable displacement of a diaphragm which constitutes an electrostatic actuator. <P>SOLUTION: An individual electrode 10 of an electrode board 4 comprises: first individual electrodes 10A which are oppositely arranged at the center of the diaphragm 51 along the longitudinal direction of the horizontally-long shape of the diaphragm 51; and second individual electrodes 10B which are oppositely arranged at both sides of the center of the diaphragm 51 along the longitudinal direction of the horizontally-long shape of the diaphragm 51. The first individual electrodes 10A and the second individual electrodes 10B can be controlled independently, and when the first individual electrodes 10A and the second individual electrodes 10B are simultaneously driven, electrostatic force generated between the diaphragm 51 and the second individual electrodes 10B is set larger than that generated between the diaphragm 51 and the first individual electrodes 10A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic drive type electrostatic actuator, a droplet discharge head to which the actuator is applied, and a droplet discharge apparatus including the droplet discharge head.

An inkjet head that uses an electrostatic actuator uses the electrostatic force generated by turning the voltage on and off between the diaphragm that forms one surface of the ink ejection pressure chamber and the opposing electrode that faces it. Then, the diaphragm is deformed, and ink is ejected from the nozzles using a pressure change caused by the deformation. And the invention which made the point in the structure of a counter electrode is disclosed so that deformation | transformation of a diaphragm can be controlled.
For example, the counter electrode is divided into two, a first counter electrode and a second counter electrode, and ink is ejected by the first counter electrode, and ink in the nozzle portion is vibrated by the second counter electrode. (For example, Patent Document 1). This prevents ink from forming on the meniscus, prevents an increase in viscosity, and improves printing quality.
In addition, the counter electrode is composed of a plurality of divided electrodes formed along the longitudinal direction of the diaphragm. By driving each of the divided electrodes, a potential difference is generated between the electrodes of the diaphragm and vibration is caused by electrostatic force. There is also one in which a plate is deformed to eject ink from a nozzle (for example, Patent Document 2).
JP 2000-168070 A JP 2000-15801 A

However, in the case of Patent Document 1, when the longitudinal direction of the diaphragm is the left-right direction, the first counter electrode and the second counter electrode are divided into two on the left and right sides. The vibration centers of the two counter electrodes are different. Therefore, each of driving the first counter electrode and the second counter electrode has a different natural frequency and changes its vibration characteristics, making it difficult to control.
On the other hand, in Patent Document 2, a plurality of divided electrodes are arranged along the longitudinal direction of the rectangular diaphragm. However, in this case, vibration is generated by a voltage applied to the divided electrode at the central portion along the longitudinal direction of the diaphragm. The voltage applied to the divided electrode at the end along the longitudinal direction of the diaphragm on which the plate is supported is low. Therefore, at the end portion along the longitudinal direction of the diaphragm, the diaphragm is not easily displaced with respect to the central portion, and the effect as an auxiliary electrode for displacing the diaphragm cannot be sufficiently obtained. .

  The present invention addresses the above-described problems, and an object thereof is to enable a large displacement and a stable displacement of a diaphragm constituting an electrostatic actuator. Another object of the present invention is to control droplet displacement by controlling the displacement mode of a diaphragm in a droplet discharge head and a droplet discharge device using an electrostatic actuator.

  The electrostatic actuator according to the present invention is arranged so as to be opposed to the vibration substrate with a gap between the vibration portion in which the vibration portion deformed by the electrostatic force is formed in a horizontally long shape in the plate surface and the vibration portion, and vibrates. And an electrode substrate on which an individual electrode for generating an electrostatic force is formed at an opposing portion of the vibrating portion, and the individual electrode is disposed opposite to the central portion of the vibrating portion along the longitudinal direction of the horizontally long shape of the vibrating portion. An individual electrode, and a second individual electrode disposed opposite to both sides of the central portion of the vibration part along the longitudinal direction of the horizontally long shape of the vibration part, the first individual electrode and the second individual electrode being independent When the first individual electrode and the second individual electrode are driven simultaneously, the electrostatic force generated between the vibration unit and the second individual electrode is generated between the vibration unit and the first individual electrode. It is designed to be larger than the electrostatic force generated in

  Thus, by dividing the individual electrode into the first individual electrode and the second individual electrode and controlling them independently, the displacement amount and the displacement mode of the diaphragm can be changed. In addition, when the first individual electrode and the second individual electrode are simultaneously driven, the electrostatic force generated between both side portions (end portions) of the central portion of the vibration part that is difficult to deform and the second individual electrode is Since the electrostatic force generated between the central portion and the first individual electrode is made larger, it is possible to obtain a large displacement amount of the diaphragm including the end of the diaphragm (diaphragm). Moreover, since these electrodes are divided along the longitudinal direction of the diaphragm, the center of vibration during driving is the same in the longitudinal direction, and vibration characteristics such as different natural frequencies do not change. The controllability is also improved. For this reason, when this electrostatic actuator is used for ink ejection, the amount of ink ejected can be increased, and the displacement of the diaphragm is made different depending on the first individual electrode and the second individual electrode. Thus, it is possible to prevent ink from being formed by adjusting the amount of ejected ink or by vibrating the meniscus, thereby realizing stable ejection.

In the electrostatic actuator, it is preferable that a gap width between the vibration part and the second individual electrode is narrower than a gap width between the vibration part and the first individual electrode in the gap between the vibration part and the individual electrode. . Since the electrostatic force increases in inverse proportion to the square of the distance between the opposing electrodes, even if the same voltage is applied to the first individual electrode and the second individual electrode, it is generated between the vibrating part and the second individual electrode. This is because the electrostatic force is larger than the electrostatic force generated between the vibrating portion and the first individual electrode, and the displacement of the entire diaphragm can be greatly increased.
Further, when an insulating film is formed on the surface of the vibration part, it is preferable that the dielectric constant of the part corresponding to the second individual electrode is higher than the dielectric constant of the part corresponding to the first individual electrode. Since the electric charge stored in the electrode increases in proportion to the dielectric constant between the electrodes, even if the same voltage is applied to the first individual electrode and the second individual electrode, it is generated between the vibrating part and the second individual electrode. This is because the electrostatic force is larger than the electrostatic force generated between the vibrating portion and the first individual electrode, and the displacement of the entire diaphragm can be greatly increased. For the same reason, when an insulating film is formed on the surface of the first individual electrode and the second individual electrode, the dielectric constant of the second individual electrode should be higher than the dielectric constant of the first individual electrode. preferable.

Furthermore, in the electrostatic actuator, the first individual electrode and the second individual electrode may be selectively driven. By selectively controlling the first individual electrode and the second individual electrode, the displacement amount and displacement mode of the diaphragm can be partially different. Therefore, this electrostatic actuator was used for ink ejection. In this case, the ink can be prevented from being formed by adjusting the amount of ink ejected or by meniscus vibration, and stable ejection can be realized.
Alternatively, the drive voltage of the first individual electrode and the second individual electrode may be made different to change the deformation of the diaphragm into a desired mode. For example, when the other conditions are the same, if the drive voltage of the second individual electrode is made higher than the drive voltage of the first individual electrode, the central portion of the vibration part can be The electrostatic force generated between the both side portions and the second individual electrode becomes larger than the electrostatic force generated between the central portion of the vibrating portion and the first individual electrode, and the displacement amount of the diaphragm can be increased.

  The droplet discharge head according to the present invention includes any one of the electrostatic actuators described above, and its vibration part constitutes a part of a pressure chamber that takes in the discharge liquid and discharges it from the nozzle. Furthermore, the second individual electrode is used for vibration control of the meniscus of the discharge liquid stored in the nozzle portion. The droplet discharge device of the present invention includes those droplet discharge heads. These droplet ejection heads and droplet ejection devices can increase the amount of ejected liquid due to the characteristics of the electrostatic actuator described above. Furthermore, stable ejection can be achieved by adjusting the amount of ejected liquid and meniscus vibration. Can be realized.

Embodiment 1 FIG.
FIG. 1 is an exploded perspective view of an inkjet head that is an electrostatically driven droplet discharge head according to Embodiment 1 of the present invention, and FIG. 2 is an individual substrate formed on an electrode substrate constituting the inkjet head shown in FIG. FIG. 3 is an explanatory sectional view (plan view) of the electrode and FIG. In the drawings shown below, the same reference numerals represent the same or equivalent.
As shown in FIGS. 1 to 3, the ink jet head 1 includes a silicon substrate 2 and a nozzle substrate 3 made of silicon or the like having a nozzle 11 on the upper side, and a borosilicate glass having a thermal expansion coefficient close to that of silicon on the lower side. It has a three-layer structure in which electrode substrates 4 made of a substrate or the like are laminated. The central silicon substrate 2 is etched from the surface thereof, whereby a plurality of independent pressure chambers 5 communicating with the nozzles 11 of the nozzle substrate 3, a reservoir 6 for storing ink sent to each pressure chamber 5, and this An ink supply path 7 that communicates the reservoir 6 with each pressure chamber 5 is formed as a groove to constitute a flow path. These grooves are closed by the nozzle substrate 3, and the portions 5, 6, and 7 are partitioned. Since each part of the flow path is formed in the silicon substrate 2, it is also called a cavity substrate.

  In the nozzle substrate 3, nozzles 11 that eject ink are formed at positions corresponding to the tip side portions of the pressure chambers 5, and they communicate with the pressure chambers 5. In addition, an ink supply port 12 communicating with the electrode substrate 4 where the reservoir 6 is located is formed, and ink is supplied from the external ink tank to the reservoir 6 through the ink supply port 12. Supplied. The ink supplied to the reservoir 6 is supplied to each pressure chamber 5 through each ink supply path 7.

  Each independent pressure chamber 5 has a laterally long groove shape, and its bottom wall 51 is thin so that it functions as a vibration part that can be elastically deformed in the out-of-plane direction, in the vertical direction in FIG. Is formed. Therefore, the bottom wall 51 functions as a diaphragm formed in a horizontally long shape (including a general rectangular shape) in the plate surface of the silicon substrate 2. In this specification, the bottom wall 51 is also referred to as a diaphragm 51 as necessary. Further, the silicon substrate 2 on which such a vibration part is formed is also referred to as a vibration substrate. The bottom wall 51 of each pressure chamber 5 is paired with an individual electrode 10 described later to constitute an electrostatic actuator.

  The electrode substrate 4 located below the silicon substrate 2 is shallowly etched at a position corresponding to each pressure chamber 5 of the silicon substrate 2, which is a bonding surface with the silicon substrate 2 that is the upper surface of the electrode substrate 4. Recesses 9 are formed, and individual electrodes 10 are formed in the recesses 9. The bottom wall 51 of each pressure chamber 5 faces the individual electrode 10 with a very small gap (gap) 8 therebetween. The gap 8 is sealed with sealing materials 15A and 15B.

The bottom wall 51 of each pressure chamber 5 is electrically connected and functions as a common electrode. The individual electrode 10 facing the bottom wall 51 is composed of a first individual electrode 10A and a second individual electrode 10B.
As shown in the explanatory view of the electrode substrate in FIG. 2, the first individual electrode 10 </ b> A is disposed to face the center portion of the diaphragm 51 along the longitudinal direction of the horizontally long shape of the diaphragm 51, and the second individual electrode 10 </ b> B. Are arranged opposite to both side portions of the central portion of the diaphragm 51 along the longitudinal direction of the horizontally long shape of the diaphragm 51. In addition, here, the first individual electrode 10A extends from one end side in the longitudinal direction of the diaphragm 51, and the second individual electrode 10B extends from the other end side. The second individual electrode 10B is arranged symmetrically on both sides of the electrode 10A.
In order to prevent sticking between the bottom wall 51 and the individual electrode 10, it is necessary to provide an insulating film on at least one of them, and here, the insulating film 52 is formed on the bottom wall 51.

Next, in order to clarify the relationship between the first individual electrode 10 </ b> A and the second individual electrode 10 </ b> B and the diaphragm 51, it is a cross-sectional view in the YY direction of FIG. 3 and a partial cross-sectional view corresponding to one pressure chamber 5. Is shown in FIG. As shown in FIG. 4, in this example, an insulating film 52 is formed on the bottom wall 51 of the pressure chamber 5, and the gap 8 between the bottom wall 51 and the first individual electrode 10A and the second individual electrode 10B is formed. The width is basically the same.
In the individual electrode 10 configured as described above, the first individual electrode 10A is used as a main electrode, and the second individual electrode 10B is used as an auxiliary electrode. The first individual electrode 10A and the second individual electrode 10B are connected to voltage application means 21A and 21B, which are separate drive sources, and can be independently controlled.
In order to make the first individual electrode 10A act as a main electrode, the electrode width of the first individual electrode 10A is set to be equal to or larger than the electrode widths of the second individual electrodes 10B arranged on both sides of the first individual electrode 10A. Is preferred.

As shown in FIG. 3, the voltage applying means 21A and 21B for applying a driving voltage between these opposing electrodes are charged between these opposing electrodes according to an external print signal (not shown). Discharge. That is, one output of the voltage applying means 21A is connected to the first individual electrode 10A, and the other output is connected to the common electrode terminal 22 formed on the silicon substrate 2. Similarly, one output of the voltage applying means 21B is connected to the second individual electrode 10B, and the other output is connected to the common electrode terminal 22.
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 electrical resistance, for example, a thin film of a conductive material such as gold may be formed on one surface of the silicon substrate 2 by vapor deposition or sputtering.

  The ink jet head 1 operates as follows. For example, when a driving voltage is applied from the voltage applying unit 21A between the diaphragm 51 and the first individual electrode 10A, the diaphragm 51 in the portion facing the first individual electrode 10A is statically caused by the charges generated there. The electric power (Coulomb force) is bent toward the first individual electrode 10A, and the volume of the pressure chamber 5 is increased. Next, when the driving voltage is released and the electric charge between the counter electrodes is discharged, the diaphragm 51 is restored by the elastic restoring force, and the volume of the pressure chamber 5 is rapidly contracted. By utilizing the ink pressure generated at this time, a part of the ink filling the pressure chamber 5 is ejected as an ink droplet from the nozzle 11 communicating with the pressure chamber 5.

  Similarly, when a driving voltage is applied between the diaphragm 51 and the second individual electrode 10B from the voltage applying means 21B, the portion of the diaphragm 51 facing the second individual electrode 10B is caused by the electric charges generated there. The electrostatic force (Coulomb force) causes the second individual electrode 10B to bend and the volume of the pressure chamber 5 increases. Next, when the driving voltage is released and the electric charge between the counter electrodes is discharged, the diaphragm 51 is restored by its elastic restoring force, and the volume of the pressure chamber 5 contracts and is stored in the pressure chamber 5 and the nozzle 11. Causes ink to vibrate. As described above, the second individual electrode 10B is designed to act as an auxiliary electrode, and ink cannot be ejected from the nozzle 11 only by driving the second individual electrode 10B. However, when used at the same time as the first individual electrode 10A, the displacement of the diaphragm 51 is increased and the amount of ink ejected from the nozzle 11 is increased.

By the way, when the first individual electrode 10A and the second individual electrode 10B are driven simultaneously, the voltage applied to the second individual electrode 10B is made larger than the voltage applied to the first individual electrode 10A, so that the diaphragm 51 and the second individual electrode The electrostatic force generated between the electrodes 10B is set to be larger than the electrostatic force generated between the diaphragm 51 and the first individual electrode 10A. This is because the end along the longitudinal direction of the vibration plate 51 is held by the silicon substrate 2, so that it is less likely to be deformed than the central portion corresponding to the first individual electrode 10 </ b> A. By doing so, the vibration plate 51 can be largely displaced, and the amount of ink discharged can be increased.
On the other hand, when the second individual electrode 10B is operated alone, the displacement of the vibration plate 51 is limited to the longitudinal end portion of the vibration plate 51. The ink stored in the flow path from the pressure chamber 5 to the nozzle 11 is vibrated, and the ink meniscus of the nozzle 11 is vibrated.

Embodiment 2. FIG.
FIG. 5 is a view corresponding to FIG. 4 for explaining the droplet discharge head according to Embodiment 2 of the present invention. In Embodiment 2, the width of the gap 8 between the bottom wall 51 and the second individual electrode 10B is configured to be narrower than the width of the gap 8 between the bottom wall 51 and the first individual electrode 10A. This is different from the first embodiment. The electrostatic force generated between the opposing electrodes increases in inverse proportion to the square of the distance between the electrodes. Therefore, according to this configuration, even when the same voltage is applied to the first individual electrode 10A and the second individual electrode 10B, the end along the longitudinal direction of the diaphragm 51 and the second individual electrode 10B Is larger than the electrostatic force generated between the central portion along the longitudinal direction of the diaphragm 51 and the first individual electrode 10A. Therefore, when the first individual electrode 10A and the second individual electrode 10B are driven at the same time, it is possible to obtain a larger displacement amount of the diaphragm 51 including the longitudinal end portion of the diaphragm 51. The discharge amount can be increased.

Embodiment 3 FIG.
FIG. 6 is a view corresponding to FIG. 4 for explaining a droplet discharge head according to Embodiment 3 of the present invention. In the third embodiment, among the insulating films formed on the surface of the bottom wall 51, the dielectric constant of the insulating film 52B facing the second individual electrode 10B is the dielectric constant of the insulating film 52A facing the first individual electrode 10A. It differs from the first embodiment in that it is configured higher than the rate. The amount of charge generated in the electrodes increases in proportion to the dielectric constant between the electrodes. Therefore, according to this configuration, even when the same voltage is applied to the first individual electrode 10A and the second individual electrode 10B, the end along the longitudinal direction of the diaphragm 51 and the second individual electrode 10B Is larger than the electrostatic force generated between the central portion along the longitudinal direction of the diaphragm 51 and the first individual electrode 10A. Therefore, when the first individual electrode 10 </ b> A and the second individual electrode 10 </ b> B are driven simultaneously, it is possible to obtain a larger displacement amount of the diaphragm 51 including the longitudinal end portion of the diaphragm 51.

Embodiment 4 FIG.
FIG. 7 is a view corresponding to FIG. 4 for explaining a droplet discharge head according to Embodiment 4 of the present invention. In the fourth embodiment, an insulating film is formed not on the surface of the bottom wall 51 of the silicon substrate 2 but on the surfaces of the first individual electrode 10A and the second individual electrode 10B, and the insulation corresponding to the second individual electrode 10B. The film 53B is different from the first embodiment in that the dielectric constant of the film 53B is higher than that of the insulating film 53A corresponding to the first individual electrode 10A. According to this configuration, the end of the diaphragm 51 along the longitudinal direction can be obtained by applying the same voltage to the first individual electrode 10A and the second individual electrode 10B by the same operation as in the third embodiment. The electrostatic force generated between the central portion and the second individual electrode 10B is larger than the electrostatic force generated between the central portion along the longitudinal direction of the diaphragm 51 and the first individual electrode 10A. Therefore, when the first individual electrode 10 </ b> A and the second individual electrode 10 </ b> B are driven simultaneously, it is possible to obtain a larger displacement amount of the diaphragm 51 including the longitudinal end portion of the diaphragm 51.

Embodiment 5 FIG.
Here, the drive aspect of the inkjet head 1 demonstrated above is demonstrated. In addition, what is demonstrated below is an example and the control performed using each divided | segmented individual electrode 10A, 10B is not limited to the following aspects.
FIG. 8 is an explanatory diagram of drive waveforms according to the fifth embodiment showing an example of drive control of the first individual electrode 10A and the second individual electrode 10B. When it is desired to eject a large amount of ink by the inkjet head 1 according to the first embodiment, a pulse voltage is simultaneously applied to both the first individual electrode 10A and the second individual electrode 10B. In this case, the electrostatic force generated between the diaphragm 51 and the second individual electrode 10B is set to be larger than the electrostatic force generated between the diaphragm 51 and the first individual electrode 10A. Therefore, in the case of the ink jet head shown in the first embodiment, the voltage applied to the second individual electrode 10B is applied to the first individual electrode 10A as shown in the column of “Large ink discharge” in FIG. Set higher than the applied voltage. By applying such a voltage to both the first individual electrode 10A and the second individual electrode 10B and driving them simultaneously, the diaphragm 51 has an attractive force acting on the whole including its longitudinal end. Thus, the diaphragm 51 is greatly deformed, and most of the diaphragm 51 comes into contact with the individual electrode 10. For this reason, the ink discharge amount from the nozzle 11 can be increased.
The longitudinal end portion of the diaphragm 51 is close to the fixed part of the diaphragm 51, so that the structure is difficult to bend. However, by increasing the driving voltage of the second individual electrode 10B, the displacement amount of the part is increased. In combination with the displacement of the central portion of the diaphragm 51 by the first individual electrode 10A, it is possible to greatly deflect the diaphragm 51 and increase the discharge amount.
On the other hand, when a small volume of ink is to be ejected by the inkjet head 1, a pulse voltage is applied only to the first individual electrode 10A as shown in the “small ink ejection” column of FIG. No voltage is applied to the second individual electrode 10B. According to this, the suction force does not act on the part corresponding to the second individual electrode 10B of the diaphragm 51, and only the central part of the diaphragm 51 facing the first individual electrode 10A is attracted to the first individual electrode 10A. As a result, a part thereof comes into contact with the first individual electrode 10A. For this reason, the amount of ink discharged from the nozzle 11 can be reduced as compared with the case where the first individual electrode 10A and the second individual electrode 10B are driven simultaneously.
Further, as shown in the column of “meniscus ink vibration” in FIG. 8, when a voltage is not applied to the first individual electrode 10A but a voltage is applied only to the second individual electrode 10B, the diaphragm In 51, an attractive force acts only on the end portion facing the second individual electrode 10B. Since the portion of the diaphragm facing the second individual electrode 10B is close to the portion where it is fixed, the diaphragm 51 is in contact with the second individual electrode 10B even if a suction force acts on that portion. There is nothing. Therefore, by repeating the voltage application to the second individual electrode 10B, minute ink vibration is possible, and fine vibration control of the meniscus of the ink remaining in the nozzle 11 portion can be performed without ejecting ink. Become. That is, by repeating charging and discharging between the second individual electrode 10 </ b> B and the diaphragm 51, the meniscus can be vibrated continuously, and the ink near the nozzle 11 and the ink filling the pressure chamber 5 can be stirred.

Embodiment 6 FIG.
FIG. 9 is a drive waveform explanatory diagram according to Embodiment 6 showing another example of drive control of the first individual electrode 10A and the second individual electrode 10B. When it is desired to eject a large amount of ink by the inkjet head 1 according to the second to fourth embodiments, a pulse voltage is simultaneously applied to both the first individual electrode 10A and the second individual electrode 10B, and the diaphragm 51 and the first The electrostatic force generated between the two individual electrodes 10B is made larger than the electrostatic force generated between the diaphragm 51 and the first individual electrode 10A. In the case of the ink jet head shown in the second to fourth embodiments, as shown in the column “Large ink discharge” in FIG. 9, the first individual electrode 10A and the second individual electrode 10B have the same height. Even if a voltage is applied, the electrostatic force generated between the diaphragm 51 and the second individual electrode 10B is larger than the electrostatic force generated between the diaphragm 51 and the first individual electrode 10B due to their structure. Become. Therefore, for example, by applying a voltage of the same height to the first individual electrode 10A and the second individual electrode 10B and driving them simultaneously, the diaphragm 51 has a suction force as a whole including its longitudinal ends. By acting, the diaphragm 51 is greatly deformed, and most of the diaphragm 51 comes into contact with the individual electrode 10. For this reason, the ink discharge amount from the nozzle 11 can be increased.
On the other hand, when it is desired to eject a small volume of ink by the inkjet head 1, a pulse voltage is applied only to the first individual electrode 10A as shown in the “small ink ejection” column in FIG. No voltage is applied to the second individual electrode 10B. According to this, the suction force does not act on the part corresponding to the second individual electrode 10B of the diaphragm 51, and only the central part of the diaphragm 51 facing the first individual electrode 10A is attracted to the first individual electrode 10A. As a result, a part thereof comes into contact with the first individual electrode 10A. For this reason, the amount of ink discharged from the nozzle 11 can be reduced as compared with the case where the first individual electrode 10A and the second individual electrode 10B are driven simultaneously.
Further, as shown in the column of “meniscus ink vibration” in FIG. 9, when no voltage is applied to the first individual electrode 10A and a pulse voltage is applied only to the second individual electrode 10B, vibration occurs. In the plate 51, an attractive force acts only on a portion facing the second individual electrode 10B. Since the portion of the diaphragm facing the second individual electrode 10B is close to the portion where it is fixed, the diaphragm 51 is in contact with the second individual electrode 10B even if a suction force acts on that portion. There is nothing. Therefore, by repeating the voltage application to the second individual electrode 10B, minute ink vibration is possible, and fine vibration control of the meniscus of the ink remaining in the nozzle 11 portion can be performed without discharging ink. Become. That is, by repeating charge and discharge between the second individual electrode 10B and the diaphragm 51, the meniscus can be vibrated continuously, and the ink in the vicinity of the nozzle 11 and the ink filling the pressure chamber 5 can be stirred.

  Since the first individual electrode 10A and the second individual electrode 10B are divided in parallel along the longitudinal direction of the diaphragm 51, in the case of the respective driving modes in the fifth and sixth embodiments, the diaphragm The vibration center 51 is the same part in the longitudinal direction, and therefore, vibration characteristics such as different natural frequencies are not changed, and controllability is improved.

Here, the manufacturing method of the inkjet head 1 shown in Embodiment 1 is demonstrated easily based on FIGS.
FIG. 10 is a flowchart showing an example of the manufacturing process of the electrode substrate 4. First, chromium is formed on a glass substrate such as borosilicate glass by sputtering (S1), and the chromium is etched to pattern a portion to be an individual electrode forming portion (S2). Thereafter, the glass substrate is etched to form glass grooves (recesses 9) that serve as individual electrode forming portions (S3). Subsequently, after removing and removing the chromium (S4), an ITO film to be an individual electrode later is formed by sputtering on the entire surface of the glass substrate on which the concave portion 9 is formed (S5). Further, the ITO-side surface of the glass substrate is patterned to remove the remaining ITO, leaving only the first individual electrode 10A, the second individual electrode 10B, and their lead and terminal portions (S6). . Finally, a through-hole serving as the ink supply port 13 is formed (S7), and the electrode substrate is completed (S8).
In the case of the inkjet head of the second embodiment, the depth of the surface corresponding to the first individual electrode 10A and the second individual electrode 10B is obtained by performing the etching of the recess 9 a plurality of times using the etching protective film. Make the difference.
In the case of the inkjet head of the fourth embodiment, different insulating films are formed on the surfaces of the first individual electrode 10A and the second individual electrode 10B using a mask or the like.

FIG. 11 is a flowchart showing an example of the manufacturing process of the silicon substrate 2. First, boron diffusion treatment for doping boron is performed on one side of a silicon wafer (S11). Subsequently, the silicon substrate is heat-treated to form a thermal oxide film of SiO2 on both surfaces (S12). This thermal oxide film serves as a hard mask when the silicon substrate is etched. Subsequently, the thermal oxide film is patterned to form the pressure chamber 5, the reservoir 6, and a portion serving as an electrode extraction part (S13). Thereafter, the silicon substrate is etched with a KOH solution or the like to form the pressure chamber 5, the reservoir 6, and the flow path portion serving as the electrode extraction portion (S14). In this case, in the portion doped with boron, the boron doped layer acts as an etching stop layer, and the etching with the KOH liquid stops. Therefore, the boron doped layer becomes the bottom wall of the pressure chamber 5, that is, the diaphragm 51. Finally, the thermal oxide film remaining on the silicon substrate 2 is once removed, and then a thermal oxide film (or TEOS oxide film) is formed again on both sides of the silicon substrate (S15). The oxide film acts as an ink protective film on the pressure chamber 5 and reservoir 6 side, and acts as an insulating film on the opposite side. Thus, the silicon substrate 2 on which the cavity constituting the ink flow path is formed is completed (S16).
In the case of the ink jet head according to the third embodiment, different insulating films are respectively formed on the portion facing the first individual electrode 10A and the portion facing the second individual electrode 10B using a mask or the like. Form.

  FIG. 12 is a flowchart showing an example of the assembly process of the inkjet head. The electrode substrate 4 manufactured as shown in FIG. 10 and the silicon substrate 2 manufactured as shown in FIG. 11 are laminated by anodic bonding (S21). Then, the gap 8 between the individual electrodes (the first individual electrode 10A and the second individual electrode 10B) formed by the lamination and the diaphragm 51 is sealed with a sealing material (S22). Thereafter, the nozzle substrate 3 is bonded and bonded to the silicon substrate 2 side (S23). Further, the laminated substrate composed of the silicon substrate 2, the electrode substrate 4 and the nozzle substrate 3 manufactured in units of silicon wafers is cut into predetermined units (S24). Thereafter, a terminal with a signal and power supply cable (FPC) is attached to each electrode (S25), thereby completing the basic form of the inkjet head 1 (S26).

  As described above, the inkjet head 1 which is an aspect of the droplet discharge head of the present invention configures the diaphragm 51, the first individual electrode 10A, and the electrostatic actuator that constitute the electrostatic actuator. By controlling the charging / discharging mode between the diaphragm 51 and the second individual electrode 10B, the amount of ink discharged from the nozzle 11 and the vibration control of the ink meniscus in the nozzle 11 portion can be controlled. It becomes possible. That is, it has the effect of increasing the ink discharge amount, and the effect of not causing a printing defect due to ink non-discharge or abnormal discharge even after a state where ink droplets are not discharged from the nozzles for a certain time or longer due to non-use of the nozzles. As described above, the first and second individual electrodes 10A and 10B are driven simultaneously or selectively as the charge / discharge mode of the electrodes constituting the electrostatic actuator, or the first individual electrode 10A. Various modes can be applied, such as making the drive voltages of the second and individual electrodes 10B different.

  In the above embodiment, the example in which the diaphragm 51 and the first individual electrode 10A and the diaphragm 51 and the second individual electrode 10B are applied to the droplet discharge head has been described. The electrostatic actuator is not limited to application to the droplet discharge head, and can be applied to other devices that perform operations using deformation of the diaphragm.

Embodiment 7 FIG.
FIG. 13 is a perspective view of a printer 100 provided with an inkjet head 1 showing an example of a droplet discharge device according to Embodiment 7 of the present invention. Since the printer 100 has the effects of the inkjet head 1 described above, it has excellent durability and printing characteristics.
In addition to the application to the printer as shown in FIG. 13, the liquid droplet ejection head described in the above embodiment can be used for variously changing the liquid droplets to be ejected to produce a color filter manufacturing apparatus for a liquid crystal display. The present invention can be applied to the discharge of various droplets such as a device for forming a light emitting portion of an organic EL display device and a discharge device for biological liquid.

1 is an exploded perspective view of a droplet discharge head according to Embodiment 1 of the present invention. FIG. 2 is an explanatory diagram (plan view) of individual electrodes formed on an electrode substrate constituting the droplet discharge head shown in FIG. 1. XX direction longitudinal cross-sectional view of the state which the droplet discharge head shown in FIG. 1 was assembled. FIG. 4 is a partial cross-sectional view corresponding to one pressure chamber 5 in the YY direction cross-sectional view of FIG. 3. FIG. 5 is a diagram corresponding to FIG. 4 for explaining a droplet discharge head according to a second embodiment. FIG. 5 is a diagram corresponding to FIG. 4 for explaining a droplet discharge head according to a third embodiment. FIG. 5 is a diagram corresponding to FIG. 4 for explaining a droplet discharge head according to a fourth embodiment. Drive waveform explanatory drawing which concerns on Embodiment 5 which shows an example of the drive control of a 1st separate electrode and a 2nd separate electrode. Drive waveform explanatory drawing which concerns on Embodiment 6 which shows the other example of drive control of a 1st separate electrode and a 2nd separate electrode. The flowchart which shows an example of the manufacturing process of an electrode substrate. The flowchart which shows an example of the manufacturing process of a silicon substrate. 5 is a flowchart showing an example of an assembly process of an inkjet head. FIG. 10 is a perspective view of a printer showing an example of a droplet discharge device according to Embodiment 7.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Inkjet head, 2 Silicon substrate (cavity substrate), 3 Nozzle substrate, 4 Electrode substrate, 5 Pressure chamber, 6 Reservoir, 7 Ink supply path, 8 Gap between a diaphragm and an individual electrode, 9 Recessed part of an electrode substrate, DESCRIPTION OF SYMBOLS 10 Individual electrode, 10A 1st individual electrode, 10B 2nd individual electrode, 11 nozzle, 12 Silicon substrate ink supply port, 13 Electrode substrate ink supply port, 21A, 21B Voltage application means, 22 Common electrode terminal, 51 Pressure chamber Bottom wall (diaphragm), 52A, 52B, 53A, 53B insulating film, 100 printer.

Claims (10)

A vibrating substrate in which a vibrating portion deformed by an electrostatic force is formed in a horizontally long shape in the plate surface;
An electrode substrate that is disposed opposite to the vibration substrate with a gap between the vibration portion and an individual electrode that generates an electrostatic force at an opposing portion of the vibration portion;
The individual electrode includes a first individual electrode disposed opposite to a central portion of the vibrating portion along a longitudinal direction of the vibrating portion of the vibrating portion, and a vibrating portion of the vibrating portion along the longitudinal direction of the vibrating portion of the vibrating portion. A second individual electrode disposed opposite to both sides of the central portion,
The first individual electrode and the second individual electrode are independently controllable,
During simultaneous driving of the first individual electrode and the second individual electrode, an electrostatic force generated between the vibration unit and the second individual electrode is generated between the vibration unit and the first individual electrode. An electrostatic actuator characterized in that the electrostatic actuator is larger than the electrostatic force.   The gap width between the vibrating part and the second individual electrode among the gaps is narrower than the gap width between the vibrating part and the first individual electrode. 1. The electrostatic actuator according to 1.   An insulating film is formed on the surface of the vibration portion, and a dielectric constant of a portion corresponding to the second individual electrode in the insulating film is higher than a dielectric constant of a portion corresponding to the first individual electrode. The electrostatic actuator according to claim 1.   An insulating film is formed on the surfaces of the first individual electrode and the second individual electrode, and the dielectric constant of the second individual electrode is higher than the dielectric constant of the first individual electrode. The electrostatic actuator according to claim 1, wherein:   The electrostatic actuator according to claim 1, wherein the first individual electrode and the second individual electrode are selectively driven.   The electrostatic actuator according to claim 1, wherein drive voltages of the first individual electrode and the second individual electrode are made different.   The electrostatic actuator according to claim 6, wherein the driving voltage of the second individual electrode is higher than the driving voltage of the first individual electrode. An electrostatic actuator according to any one of claims 1 to 7,
The liquid droplet ejection head, wherein the vibration part constitutes a part of a pressure chamber that takes in the ejection liquid and ejects it from the nozzle.   9. The droplet discharge head according to claim 8, wherein the second individual electrode is used for vibration control of a meniscus of discharge liquid stored in the nozzle portion.   A droplet discharge apparatus comprising the droplet discharge head according to claim 8.

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