JP2009248560A - Electrostatic actuator, liquid droplet delivering head, method for manufacturing them and liquid droplet delivering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic actuator which is excellent in process adaptability and has a highly accurate step-like level difference, and to provide a method for manufacturing it or the like. <P>SOLUTION: In the electrostatic actuator equipped with an individual electrode 5 formed on a glass substrate, a vibrating plate 6 opposed and arranged in parallel to this individual electrode 5 through a predetermined gap, and a driving means 40 for generating an electrostatic force between the individual electrode 5 and the vibrating plate 6 to generate a displacement in the vibrating plate 6, an insulating membrane 7 having at least one step of step-like level difference on an opposing face to the vibrating plate 6 of the individual electrode 5, is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic actuator, a droplet discharge head, a manufacturing method thereof, and a droplet discharge device used for an electrostatic drive type inkjet head or the like.

  As a droplet discharge head for discharging droplets, for example, an electrostatic drive type inkjet head mounted on an inkjet recording apparatus is known. In general, an electrostatic drive type inkjet head includes an individual electrode (fixed electrode) formed on a glass substrate, and a silicon diaphragm (movable electrode) disposed in parallel to the individual electrode with a predetermined gap therebetween. ). Then, a nozzle substrate in which a plurality of nozzle holes for discharging ink droplets is formed, and an ink flow path such as a discharge chamber and a reservoir that are joined to the nozzle substrate and communicated with the nozzle holes are formed. The cavity substrate is provided, and an electrostatic force is generated in the electrostatic actuator unit so as to apply pressure to the discharge chamber to discharge ink droplets from selected nozzle holes.

In such an electrostatic drive type ink-jet head, a structure that increases the displacement amount of the diaphragm and increases the ejection energy of droplets without causing an increase in drive voltage has been studied. One of the structures is a method of providing a stepped step on the individual electrode. For example, in Patent Document 1, when a silicon substrate is used as a support substrate (electrode substrate) for an individual electrode, a recess having a stepped step is formed in an insulating film formed on the silicon substrate, and the bottom of the recess is formed. It is disclosed that an individual electrode having a stepped step is formed by forming an individual electrode, and when a glass substrate is used as a support substrate (electrode substrate) for the individual electrode, a stepped shape is formed on the glass substrate. It is disclosed that an individual electrode having a stepped step is formed by forming a recess having a step and forming an individual electrode on the bottom surface of the recess.
Patent Document 2 and Patent Document 3 are examples of forming a stepped step on an individual electrode by forming a recess having a stepped step on a glass substrate.

JP 2000-318155 A JP 2006-25622 A JP 2006-28964 A

However, when a silicon substrate is used as an electrode substrate as in Patent Document 1, processing is easier than when a glass substrate (for example, a borosilicate glass substrate) is used, but there are the following problems.
(1) Since the unit price of the silicon substrate is higher than the unit price of the glass substrate, the cost is increased.
(2) When joining the cavity substrates, anodic bonding is not possible.
(3) Since the silicon substrate is not transparent, the state inside the electrostatic actuator cannot be observed.
In addition, when a glass substrate is used as an electrode substrate as in Patent Document 1 and Patent Documents 2 and 3, a stepped step is formed by patterning and wet etching a plurality of times. It was difficult to control and it was difficult to form the step with high accuracy. For this reason, the gap length is likely to vary, and as a result, the ejection amount varies, and the printing quality is impaired.
Furthermore, although the electrostatic actuator is miniaturized as the density of the ink jet head is increased, it is necessary to increase the generated pressure of the electrostatic actuator with a drive voltage as low as possible in order to ensure the discharge pressure of the ink jet head. However, such a device is not made in Patent Document 1, Patent Document 2, and 3.

  An object of the present invention is to provide an electrostatic actuator having a highly accurate step-like step having excellent process adaptability, a method for manufacturing the same, and the like.

An electrostatic actuator according to the present invention includes a fixed electrode formed on a glass substrate, a movable electrode disposed in parallel to the fixed electrode via a predetermined gap, and a fixed electrode and a movable electrode. In the electrostatic actuator having a driving means for generating an electrostatic force on the movable electrode to cause displacement of the movable electrode, an insulating film having at least one stepped step is provided on the surface of the fixed electrode facing the movable electrode. It is provided.
According to this configuration, since one or more steps are formed in the insulating film formed on the fixed electrode, there is an effect that the accuracy of the steps is improved.

  The insulating film has a stepped step in the longitudinal direction or the width direction of the fixed electrode. The step of the insulating film can be provided in either the longitudinal direction or the width direction of the fixed electrode. Accordingly, the movable electrode can be continuously contacted in the longitudinal direction or the width direction of the fixed electrode without causing an increase in the driving voltage, and stable ejection can be performed with a large displacement.

In addition, the insulating film is formed in an arbitrary number of steps on the opposing surface of the fixed electrode other than the deepest part of the gap.
The surface of the fixed electrode can be exposed without providing an insulating film at the deepest part of the gap.

The insulating film includes at least a silicon oxide film.
The silicon oxide film can ensure the required withstand voltage and bonding strength.

The insulating film includes at least a diamond-like carbon film.
Since the diamond-like carbon film has high surface smoothness and low friction, the driving durability and driving stability of the electrostatic actuator are improved. In addition, it is desirable to use hydrogenated amorphous carbon among diamond-like carbon, and when the film is formed by the CVD method, the durability is high.

The insulating film includes at least a dielectric film made of a dielectric material having a relative dielectric constant larger than that of silicon oxide.
When a dielectric material having a relative dielectric constant larger than that of silicon oxide, a so-called High-k material, is used as the insulating film, the generated pressure of the electrostatic actuator can be improved, so that the electrostatic actuator can be miniaturized and densified. .
Among the high-k materials, aluminum oxide (Al ₂ O ₃ ), hafnium oxide (HfO ₂ ), hafnium nitride silicate (HfSiN), oxynitride hafnium silicate (HfSiON) are particularly preferable from the viewpoints of process suitability and film quality stability. ) Is desirable, and at least one of them may be selected.

A first manufacturing method of an electrostatic actuator according to the present invention includes a fixed electrode formed on a glass substrate, a movable electrode arranged in parallel to the fixed electrode via a predetermined gap, and a fixed electrode. In the manufacturing method of the electrostatic actuator comprising the driving means for generating a displacement in the movable electrode by generating an electrostatic force between the movable electrode and the movable electrode,
Forming an insulating film on the entire surface of the glass substrate on which the fixed electrode is formed;
A patterning step of patterning the insulating film formed on the entire surface;
An insulating film etching step of selectively removing the portion of the insulating film exposed by patterning by etching;
By repeating the patterning step and the insulating film etching step at least once or a plurality of times, an insulating film having one or more stepped steps is formed on the fixed electrode.

In this first manufacturing method, an insulating film is formed on the entire surface of the fixed electrode, and the insulating film formed on the entire surface is patterned at least once or a plurality of times, and a portion of the insulating film exposed by the patterning is formed. Since the insulating film to be removed is etched, an insulating film having a highly accurate step can be formed on the fixed electrode.
In the insulating film etching step, it is desirable to remove the insulating film by dry etching.

A second manufacturing method of an electrostatic actuator according to the present invention includes a fixed electrode formed on a glass substrate, a movable electrode disposed in parallel to the fixed electrode via a predetermined gap, and a fixed electrode. In the manufacturing method of the electrostatic actuator comprising the driving means for generating a displacement in the movable electrode by generating an electrostatic force between the movable electrode and the movable electrode,
An insulating film having one or more stepped steps is formed on the fixed electrode by sputtering using a mask member.

  In the second manufacturing method, an insulating film having one or more stepped steps can be directly formed on the fixed electrode by a sputtering method using a mask member. In comparison, the process is simplified, so that the manufacturing method is more effective as the number of stages is larger.

A droplet discharge head according to the present invention is one in which any one of the electrostatic actuators described above is mounted.
Since the droplet discharge head according to the present invention includes the electrostatic actuator in which the insulating film having a highly accurate step is formed on the fixed electrode as described above, the movable electrode can be stabilized without causing an increase in driving voltage. Thus, it is possible to realize a droplet discharge head having excellent discharge characteristics and high density.

A method of manufacturing a droplet discharge head according to the present invention is a method of manufacturing a droplet discharge head by applying any one of the above-described electrostatic actuator manufacturing methods.
As a result, a droplet discharge head having excellent discharge characteristics and capable of high density can be manufactured at low cost.

  A droplet discharge apparatus according to the present invention is equipped with the above-described droplet discharge head. Therefore, it is possible to provide a droplet discharge device that has excellent discharge characteristics and can have a high density.

  Hereinafter, embodiments of a droplet discharge head including an electrostatic actuator to which the present invention is applied will be described with reference to the drawings. Here, as an example of a droplet discharge head, a face discharge type electrostatic drive type inkjet head that discharges ink droplets from nozzle holes provided on the surface of a nozzle substrate will be described with reference to FIGS. . Note that the present invention is not limited to the structure and shape shown in the following drawings, and has a four-layer structure in which four substrates each having a discharge chamber and a reservoir portion provided on separate substrates are laminated, The present invention can be similarly applied to an edge discharge type droplet discharge head that discharges ink droplets from a nozzle hole provided at the end of the nozzle.

Embodiment 1 FIG.
FIG. 1 is an exploded perspective view showing an exploded schematic configuration of an ink jet head according to Embodiment 1 of the present invention, and a part thereof is shown in cross section. 2 is a cross-sectional view of the inkjet head showing a schematic configuration of the substantially right half of FIG. 1 in the assembled state (however, the configuration of the insulating film on the individual electrode is different from that of FIG. 1), and FIG. 3 is an enlarged view of AA in FIG. 4 is a top view of the ink jet head of FIG. 1 and 2 are shown upside down from a state in which they are normally used.

  As shown in FIGS. 1 to 4, the inkjet head 10 according to the first embodiment includes a nozzle substrate 1 in which a plurality of nozzle holes 11 are provided at a predetermined pitch, and ink independently for each nozzle hole 11. The cavity substrate 2 provided with the supply path and the electrode substrate 3 provided with the individual electrodes 5 facing the diaphragm 6 provided on the cavity substrate 2 are bonded together.

  As shown in FIG. 2 and FIG. 3, the electrostatic actuator unit 4 provided for each nozzle hole 11 of the inkjet head 10 includes an individual electrode 5 formed in the recess 32 of the glass electrode substrate 3 as a fixed electrode. The movable electrode is provided with a diaphragm 6 that is configured by a bottom wall of the discharge chamber 21 of the cavity substrate 2 made of silicon and is arranged to face the individual electrode 5 with a predetermined gap G therebetween. The individual electrode 5 includes an electrode portion 5a facing the diaphragm 6, a lead portion 5b extending toward the substrate end side, and a terminal portion 5c connected to a flexible printed circuit board (FPC) (not shown). .

Here, an insulating film 7 made of, for example, a silicon oxide film (SiO ₂ film) is formed in one or more steps on the surface of the individual electrode 5 facing the diaphragm 6 in the electrode portion 5a. The insulating film 7 can have an arbitrary number of steps, but in the first embodiment, the insulating film 7 is provided on the opposing surface other than the deepest part of the gap in the longitudinal direction by one step. Yes. That is, the gap length G at the deepest portion is in a state where the surface of the individual electrode 5 is exposed (the state where the insulating film 7 is not present in this portion). Therefore, the gap length of the insulating film 7 forming portion is G1 narrower than G (G> G1). As a result, the diaphragm 6 can be in contact with a minimum with the insulating film 7 formed. Here, coupled contact refers to the individual electrodes 5 while the diaphragm 6 sequentially contacts the end portions of the insulating films 7 by electrostatic attraction as shown schematically by broken lines in FIG. It means to abut. The coupled contact state can be changed depending on the magnitude of the drive voltage. Therefore, since the displacement amount of the diaphragm 6 changes, the ink discharge amount can be changed variously.
The step of the insulating film 7 (thickness difference in the case of two or more steps) can be arbitrarily set, but is preferably 20% or less of the gap length G of the deepest portion. If the level difference is too large, the diaphragm 6 will not be in contact with the coupling and the effects of the present invention will not be obtained. In the case of the first embodiment, the gap length G at the deepest part is 200 nm, the thickness of the insulating film 7 is 30 nm, and the thickness of the insulating film 9 on the diaphragm 6 side is 110 nm.

The individual electrode 5 is generally formed of ITO (Indium Tin Oxide), which is a transparent electrode, but is not particularly limited thereto. A transparent electrode of IZO (Indium Zinc Oxide) or a metal such as Au or Al may be used.
A drive control circuit 40 such as a driver IC is provided as a drive means for the electrostatic actuator as shown in FIG. 4 in a simplified manner in the terminal portion 5c of the individual electrode 5 and the common electrode 26 provided on the cavity substrate 2. Wiring is connected via the FPC. Also, an insulating film 9 made of a thermal oxide film of silicon is formed on the surface of the diaphragm 6 facing the individual electrode 5, that is, the entire bonding surface of the cavity substrate 2 in order to prevent dielectric breakdown or short circuit of the electrostatic actuator. Has been.

Hereinafter, the configuration of each substrate will be described in more detail.
The nozzle substrate 1 is made of, for example, a silicon substrate. The nozzle holes 11 for ejecting ink droplets are, for example, nozzle hole portions formed in a two-stage coaxial cylindrical shape having different diameters, that is, an ejection port portion 11a having a smaller diameter and an inlet port portion 11b having a larger diameter. It is composed of The ejection port portion 11a and the introduction port portion 11b are provided perpendicular to and coaxially with the substrate surface, and the ejection port portion 11a has a leading end that opens on the surface (ink ejection surface) of the nozzle substrate 1, and the introduction port portion. 11b is opened on the back surface of the nozzle substrate 1 (the surface on the bonding side to be bonded to the cavity substrate 2).
In addition, the nozzle substrate 1 is formed with an orifice 12 for communicating the discharge chamber 21 of the cavity substrate 2 and the reservoir 23 and a diaphragm portion 13 for compensating for pressure fluctuations in the reservoir 23 portion.

  By forming the nozzle hole 11 in two stages from the ejection port portion 11a and the inlet port portion 11b having a larger diameter than this, the ink droplet ejection direction can be aligned with the central axis direction of the nozzle hole 11 and stable. Ink discharge characteristics can be exhibited. That is, there is no variation in the flying direction of the ink droplets, there is no scattering of the ink droplets, and variation in the ejection amount of the ink droplets can be suppressed. In addition, the nozzle density can be increased.

  The cavity substrate 2 bonded to the electrode substrate 3 is made of, for example, a silicon substrate having a plane orientation of (110). The cavity substrate 2 is formed by etching with a recess 22 serving as a discharge chamber 21 provided in the ink flow path and a recess 24 serving as a reservoir 23. A plurality of recesses 22 are independently formed at positions corresponding to the nozzle holes 11. Therefore, as shown in FIG. 2, when the nozzle substrate 1 and the cavity substrate 2 are joined, each concave portion 22 constitutes a discharge chamber 21 and communicates with each nozzle hole 11 and the orifice 12 serving as an ink supply port. Both communicate with each other. The bottom of the discharge chamber 21 (concave portion 22) is the diaphragm 6. The diaphragm 6 is formed of a boron diffusion layer in which a high concentration of boron (B) is diffused on the surface of the silicon substrate, and the thickness of the boron diffusion layer is the same as the thickness of the diaphragm 6. It is. This is because, when the discharge chamber 21 is formed by anisotropic wet etching using alkali, the etching rate becomes extremely small when the boron diffusion layer is exposed. This is because it can be formed with high accuracy.

  The recess 24 is for storing a liquid material such as ink, and constitutes a reservoir (common ink chamber) 23 common to the ejection chambers 21. The reservoirs 23 (recesses 24) communicate with all the discharge chambers 21 through the orifices 12, respectively. A hole penetrating the electrode substrate 3 is provided at the bottom of the reservoir 23, and ink is supplied from an ink cartridge (not shown) through the ink supply hole 33 of the hole.

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

  The electrode substrate 3 and the cavity substrate 2 manufactured as described above are anodically bonded, and the nozzle substrate 1 is bonded and bonded thereon, whereby the main body of the inkjet head 10 is completed as shown in FIG. Thereafter, the drive control circuit 40 is wired to each individual electrode 5 and the common electrode 26 using FPC. Further, the electrode lead-out portion (also referred to as FRP mounting portion) 34 is hermetically sealed by applying a sealing material 35 such as an epoxy resin to the open end portion of the gap of the electrostatic actuator. As a result, moisture and foreign matter can be reliably prevented from entering the gap of the electrostatic actuator, and driving stability and durability can be realized. That is, the reliability of the inkjet head 10 is improved.

Next, the operation of the inkjet head 10 configured as described above will be described.
When a pulse voltage is applied between the individual electrode 5 and the common electrode 26 of the cavity substrate 2 by the drive control circuit 40, the diaphragm 6 is attracted and attracted to the individual electrode 5 side by electrostatic attraction. At that time, since the insulating film 7 having a step is formed on the individual electrode 5, the diaphragm 6 contacts the insulating film 7 from the smaller gap length, that is, from the upper stage in FIG. Of the individual electrodes 5. In other words, the diaphragm 6 contacts the insulating film 7 by applying a voltage sufficient to fill the upper gap length G1, and the next-stage gap length G−G1 = t (t: of the insulating film 7). The diaphragm 6 comes into contact with the individual electrode 5 by applying a voltage sufficient to fill the thickness. In this way, in contact with the end portions of the insulating film 7 in each step in sequence according to the number of steps of the insulating film 7, the abutting contact is made in contact with the individual electrodes 5. When the vibration plate 6 is displaced by the coupled contact, negative pressure is generated in the discharge chamber 21, the ink in the reservoir 23 is sucked, and ink vibration (meniscus vibration) is generated. When the voltage of the ink is released when the vibration of the ink becomes substantially maximum, the vibration plate 6 is detached, the ink is pushed out from the nozzle 11, and the ink droplet is ejected.

Therefore, according to the inkjet head 10 according to the first embodiment, a large amount of displacement can be obtained with a relatively low driving voltage, so that stable ejection with little variation is possible. Further, since the displacement amount of the diaphragm 6 can be controlled by controlling the drive voltage and the ink discharge amount can be changed, high-definition expression with various gradations becomes possible. In addition, the density of the ink jet head can be increased by miniaturizing the electrostatic actuator, and the cost can be reduced.
In addition, the structure in which the insulating film 7 on the individual electrode 5 is formed stepwise before and after the longitudinal direction as in the first embodiment has a high dielectric constant near the nozzle hole 11, so that the diaphragm can be easily controlled. Since control is easy to perform, this structure is desirable when performing MSDT (ink discharge amount control).

Next, the generated pressure of the electrostatic actuator will be described.
The electrostatic pressure (generated pressure) P that attracts the diaphragm 6 during driving is E, the electrostatic energy is E, the arbitrary position of the diaphragm 6 with respect to the individual electrode 5 is x, the area of the diaphragm 6 is S, and the applied voltage is Assuming V, the thickness of the insulating film is t, the dielectric constant in vacuum is ε ₀ , and the relative dielectric constant of the insulating film is ε _r , the following expression is obtained.

Further, average pressure P _e at the time of driving the diaphragm 6, the distance to the individual electrode 5 from the diaphragm 6 when the diaphragm 6 is not driven (the gap length) as d, is represented by the following formula .

Equations 1 and 2 are substantially applicable to each step when the insulating film 7 on the individual electrode 5 has a plurality of steps. Therefore, it can be seen from Equation 2 that the average pressure _Pe increases as the relative dielectric constant of the insulating film increases or as the ratio (t / ε) of the relative dielectric constant to the thickness of the insulating film decreases. Since silicon oxide has a relative dielectric constant of about 3.8, which is larger than that of air, when it is configured in multiple stages, a portion where the cumulative thickness of the insulating film is thicker than a portion where the cumulative thickness of the insulating film is thinner. The generated pressure of the electric actuator can be increased.
That is, when a voltage is applied to the electrostatic actuator according to the present invention, since the abutting occurs from the portion where the accumulated thickness of the insulating film having a relatively large generated pressure is thick, the portion where the cumulative thickness of the insulating film is thin is originally necessary. The electrostatic actuator can be brought into contact with a voltage lower than the contact voltage. For example, if the relative dielectric constant of the insulating film is doubled as a whole, almost the same generated pressure can be obtained even if the thickness of the insulating film is doubled. Dielectric breakdown strength, long-time dielectric breakdown strength), TZDB (Time Zero Dielectric Breakdown, instantaneous dielectric breakdown strength), etc. can be further improved. Further, when compared with the same contact voltage, the volume change amount of the discharge chamber can be increased, and a large ink rejection volume can be ensured.

  2 shows the case where the step of the insulating film 7 is provided in the longitudinal direction of the individual electrode 5. However, the step of the insulating film 7 may be provided in the width direction of the individual electrode 5 as shown in FIG. There is a similar effect. The longitudinal direction of the individual electrode 5 refers to the length direction in which the individual electrode 5 extends, that is, the length direction of the recess 32, and the width direction of the individual electrode 5 refers to the nozzle row direction, that is, the groove width of the recess 32. The direction.

Embodiment 2. FIG.
FIG. 6 is a schematic sectional view of an ink jet head according to Embodiment 2 of the present invention. In the second and subsequent embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The second embodiment is the same as the first embodiment except that the insulating film 7 is configured in two stages. Further, a step (1) and a step (2) are formed from the top. This manufacturing method will be described later. Both the first-stage insulating film 7a and the second-stage insulating film 7b are formed of a silicon oxide film. In addition, there is no insulating film 7 at the center of the electrode, which is the surface of the individual electrode 5. In FIG. 6, the first-stage and second-stage interfaces are shown for easy understanding. However, in the case of the same kind of dielectric material, this interface does not actually exist. The thickness of the insulating film 7 is 20 nm for both the first and second stages. The gap length G at the deepest part is 200 nm. Therefore, the first-stage gap length G1 = 160 nm, and the second-stage gap length G2 = 180 nm. In addition, the thickness of the insulating film 9 on the diaphragm 6 side is 110 nm.

  According to the second embodiment, in addition to the effects of the first embodiment, the pressure generated by the actuator can be increased by forming the insulating film 7 in two stages. This will further contribute to higher density.

Embodiment 3 FIG.
FIG. 7 is a schematic sectional view of an ink jet head according to Embodiment 3 of the present invention.
In the third embodiment, the second-stage insulating film 7b is formed on the entire surface of the electrode portion 5a of the individual electrode 5 in the second embodiment. Therefore, the level difference is one level. In this way, the insulating film 7 may not have a step, but for convenience, the insulating film including the step (2) is also referred to as a second-stage insulating film 7b. The other configuration is the same as that of the second embodiment. Further, the film thickness of the insulating film 7 is the same as that of the second embodiment, and the first stage and the second stage are each 20 nm, and the gap length G of the deepest part is 200 nm. The thickness of the insulating film 9 on the diaphragm 6 side is 110 nm.

  The third embodiment has the same effect as the second embodiment, and the diaphragm 6 and the individual electrode 5 are repeatedly brought into contact with and separated from each other through the insulating film 9 and the insulating film 7 of the same material. This has the effect of improving the drive durability and stability of the electric actuator.

Embodiment 4 FIG.
FIG. 8 is a schematic cross-sectional view of an inkjet head according to Embodiment 4 of the present invention.
In the first to third embodiments so far, the deepest part of the gap length G is provided at the center of the electrode part 5a of the individual electrode 5, but in the fourth embodiment, the tip part of the electrode part 5a is provided. The deepest part of the gap length G is provided (position close to the nozzle hole 11). The insulating film 7 on the individual electrode 5 has a two-stage structure, and is formed of a silicon oxide film. The film thickness and the like of the insulating film 7 are the same as those in the second embodiment, and the first stage and the second stage are each 20 nm, and the gap length G of the deepest part is 200 nm. In addition, the thickness of the insulating film 9 on the diaphragm 6 side is 110 nm.

  The fourth embodiment has the same effect as that of the third embodiment, and also has an ink rectifying effect during ejection because the deepest portion G of the gap length is provided at the tip of the electrode portion 5a close to the nozzle hole 11. Therefore, it is possible to increase the ink discharge weight. Therefore, the printing speed is improved.

Embodiment 5 FIG.
FIG. 9 is a schematic sectional view of an ink jet head according to Embodiment 5 of the present invention.
In the fifth embodiment, the insulating film 7 on the individual electrode 5 has a laminated structure made of a combination of different materials. That is, the first-stage insulating film 7a is formed of silicon oxide (SiO ₂ ), and the second-stage insulating film 7b is formed of aluminum oxide (Al ₂ O ₃ , alumina). When a so-called High-k material (high dielectric constant insulating material) such as alumina is used, the relative dielectric constant is about 7.9, which is larger than the relative dielectric constant 3.8 of silicon oxide. It becomes possible to raise more.

High-k materials having a relative dielectric constant larger than that of silicon oxide include alumina, silicon oxynitride (SiON), hafnium oxide (HfO ₂ ), tantalum oxide (Ta ₂ O ₃ ), hafnium nitride silicate (HfSiN), Hafnium oxynitride silicate (HfSiON), aluminum nitride (AlN), zirconium nitride (ZrO ₂ ), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), yttrium oxide (Y ₂ O ₃ ), zirconium silicate (ZrSiO), Examples thereof include hafnium silicate (HfSiO), zirconium aluminate (ZrAlO), nitrogen-added hafnium aluminate (HfAlON), and composite films thereof. Among them, when considering low-temperature film formability, film homogeneity, process adaptability, etc., aluminum oxide (Al ₂ O ₃ , alumina), hafnium oxide (HfO ₂ ), hafnium nitride silicate (HfSiN), oxynitride It is desirable to use hafnium silicate (HfSiON), at least one of which is selected.

  The insulating film 7 may be a combination of high-k materials, and the high-k material and silicon oxide are stacked opposite to the above, that is, the first stage is a high-k material and the second stage is silicon oxide. It is good. Further, the number of steps of the insulating film 7 is arbitrary, and therefore there is no particular limitation on the combination order of the dielectric materials.

Embodiment 6 FIG.
FIG. 10 is a schematic sectional view of an ink jet head according to Embodiment 6 of the present invention.
In the sixth embodiment, the insulating film 7 on the individual electrode 5 has a laminated structure of different materials as in the fifth embodiment, but the first-stage insulating film 7a is made of DLC (diamond-like carbon), particularly It is formed by hydrogenated amorphous carbon (aC: H). The second-stage insulating film 7b is silicon oxide as described above. Regarding the film thickness of the insulating film 7, the first-stage insulating film (aC: H) 7 a is 10 nm, the second-stage insulating film (SiO ₂ ) 7 b is 30 nm, the deepest gap length G = 200 nm, the diaphragm The thickness of the 6-side insulating film 9 is 110 nm.

  Since DLC has high surface smoothness and low friction, it is possible to further improve the driving durability and driving stability of the electrostatic actuator by forming it on the outermost surface of the insulating film 7. In particular, when an aC: H film is used as the DLC film, the aC: H film has high durability when formed by a CVD (Chemical Vapor Deposition) method. The thickness of the aC: H film, which is the first-stage insulating film 7a, is about 10 nm because the film stress increases if it is too thick. On the other hand, if it is too thin, the characteristics as an aC: H film cannot be exhibited.

(Inkjet head manufacturing method)
Next, an outline of a method for manufacturing the inkjet head 10 according to the first to sixth embodiments will be described with reference to FIGS. FIG. 11 is a flowchart showing a schematic flow of the manufacturing process of the inkjet head 10, and FIGS. 12 to 15 are schematic cross-sectional views of the manufacturing process showing the first manufacturing method of the electrode substrate according to the first to sixth embodiments. . However, the third and fourth embodiments are not shown. FIG. 16 is a cross-sectional view illustrating an outline of the manufacturing process of the inkjet head 10 according to the first embodiment.

  In FIG. 11, steps S <b> 1 to S <b> 6 show the manufacturing process of the electrode substrate 3, and steps S <b> 7 and S <b> 8 show the manufacturing process of the silicon substrate from which the cavity substrate 2 is based. The first manufacturing method is a method of forming a desired number of stages of insulating films 7 on the individual electrodes 5 by repeating patterning and insulating film etching a plurality of times.

(First manufacturing method of electrode substrate)
First, the 1st manufacturing method of the electrode substrate 3 which concerns on each embodiment is demonstrated.
1. In the case of Embodiment 1 (1) A recess 32 having a desired depth is obtained by etching a glass substrate 300 made of borosilicate glass or the like with a thickness of about 1 mm with hydrofluoric acid using, for example, an etching mask made of gold or chromium. Form. Note that the recess 32 has a groove shape slightly larger than the shape of the individual electrode 5, and a plurality of the recesses 32 are formed for each individual electrode 5.
Then, for example, an ITO (Indium Tin Oxide) film having a thickness of 100 nm is formed by sputtering, and this ITO film is patterned by photolithography to remove the portions other than the individual electrode 5 by etching to remove the inside of the recess 32. The individual electrodes 5 are formed on the substrate (S1 in FIG. 11, FIG. 12A).

(2) Next, as the insulating film 7 on the individual electrode 5, RF-CVD (Chemical Vapor Deposition) using TEOS (Tetraethoxysilane) as a source gas over the entire surface on the bonding surface side of the glass substrate 300. A SiO ₂ film having a thickness of 30 nm is formed by a method (hereinafter referred to as TEOS-CVD method) (S2 in FIG. 11, FIG. 12B).

(3) Next, a resist is applied to the SiO ₂ film formed on the entire surface, and the first patterning is performed by photolithography (S3 in FIG. 11). In the patterning, a resist is opened so as to remove the SiO ₂ film at the electrode central portion and the FPC mounting portion (electrode extraction portion) 34 of the individual electrode 5 and the bonding portion 36 of the glass substrate 300.
(4) Next, by RIE (Reactive Ion Etching) dry etching by CHF _3, SiO ₂ film of the electrode central portion, the SiO ₂ film of the FPC mounting portion 34, and simultaneously etching the SiO ₂ film is removed at the junction 36, further If the resist is removed by washing with sulfuric acid, the one-step insulating film 7 having the step (1) shown in the first embodiment can be formed on the individual electrode 5 (S4 in FIG. 11, FIG. 12 (c)). ).
(5) Thereafter, a hole 33a to be the ink supply hole 33 is formed in the glass substrate 300 by blasting or the like.

2. In the case of Embodiments 2 and 3 (1) The steps (a) and (b) of FIG. 13 are the same as (1) and (2) in Embodiment 1. However, the thickness of the SiO ₂ film formed on the entire surface is 40 nm.
(2) Next, the first resist patterning is performed in the same manner as in the above (3) (S3 in FIG. 11), and the SiO _{2 of the} center portion of the electrode, the FPC mounting portion 34 and the joining portion 36 is obtained by RIE dry etching with CHF _3. The film is etched away by 20 nm (S4 in FIG. 11, FIG. 13C). As a result, a first-stage insulating film 7a having a step (1) of 20 nm is formed.
(3) Next, after peeling off the resist, (S5 in FIG. 11) performs the resist patterning for the second time, by RIE dry etching by CHF _3, the electrode central portion, SiO ₂ of the FPC mounting portion 34 and the joint 36 The film is further etched away by 20 nm (S6 in FIG. 11). Then, if the resist is removed by washing with sulfuric acid, a second-stage insulating film 7b having a step (2) of 20 nm is formed (FIG. 13D). Thereby, the two-step insulating film 7 having the step (1) and the step (2) shown in the second embodiment can be formed on the individual electrode 5.
(4) Thereafter, a hole 33a to be the ink supply hole 33 is formed in the glass substrate 300 by blasting or the like.

In the case of the third embodiment, in the step (3) in the second embodiment, the second resist patterning may be performed so as to leave the SiO ₂ film at the center of the electrode.

3. Case of Embodiment 4 Although illustration is omitted, it is basically the same as the case of Embodiment 3. That is, the position where the step (1) is provided only changes from the electrode central portion to the tip portion of the individual electrode 5, and in the second resist patterning, patterning is performed so as to leave the SiO ₂ film at the tip portion of the individual electrode 5. Just do it.

4). In the case of Embodiment 5 (1) The process of FIG. 14A is the same as (1) of Embodiment 1.
(2) Using an ECR (Electron Cyclotron Resonance) sputtering method, an Al ₂ O ₃ film to be the second-stage insulating film 7b is formed with a thickness of 20 nm on the entire surface on the bonding surface side of the glass substrate 300 (FIG. 11). S2, FIG. 14 (b)).
(3) Further, an SiO ₂ film to be the first-stage insulating film 7a is formed on the entire surface of the Al ₂ O ₃ film with a thickness of 30 nm by TEOS-CVD (S2 in FIG. 11, FIG. 14 ( c)).
(4) Next, the resist patterning for the first time with respect to the SiO ₂ film by RIE dry etching by CHF _3, step on the SiO ₂ film is removed and the individual electrodes 5 of the FPC mounting portion 34 and the joint portion 36 ( 1) is formed (S3 and S4 in FIG. 11, FIG. 14D).
(5) Next, in order to remove the Al ₂ O ₃ film of FPC mounting portion 34 and the joint portion 36, resist patterning for the second time, the Al ₂ O ₃ film in that portion by RIE dry etching by CHF ₃ It is removed (S5, S6 in FIG. 11, FIG. 14E).
(6) Thereafter, a hole 33a to be the ink supply hole 33 is formed in the glass substrate 300 by blasting or the like.

5. In the case of Embodiment 6 (1) The process of FIG. 15A is the same as (1) of Embodiment 1.
(2) Using the TEOS-CVD method, an SiO ₂ film to be the second-stage insulating film 7b is formed to a thickness of 30 nm on the entire surface on the bonding surface side of the glass substrate 300 (S2 in FIG. 11, FIG. 15 ( b)).
(3) Further, an aC: H film (hydrogenated amorphous carbon) to be the first-stage insulating film 7a is formed on the SiO ₂ film by using an RF-CVD method (RF power: 900 W, source gas: toluene). A film is formed on the entire surface with a thickness of 10 nm (S2 in FIG. 11, FIG. 15C).
(4) Next, the a-C: perform resist patterning for the first time with respect to H film, a step on the SiO ₂ film is removed and the individual electrodes 5 of the FPC mounting portion 34 and the joint portion 36 by etching with O ₂ ashing A first-stage insulating film 7a having (1) is formed (S3, S4 in FIG. 11, FIG. 15 (d)).
(5) Next, in order to remove the SiO ₂ film of the FPC mounting portion 34 and the joint portion 36, second resist patterning is performed, and the SiO ₂ film in the portion is removed by RIE dry etching with CHF ₃ (FIG. 11 S5, S6, FIG. 15 (e)).
(6) Thereafter, a hole 33a to be the ink supply hole 33 is formed in the glass substrate 300 by blasting or the like.
As described above, the electrode substrate 3 of the first to sixth embodiments is manufactured. In S6 of FIG. 11, the n-th insulating film has an n-th level difference and the surface of the individual electrode 5 is exposed, and there is no n-th level difference and the surface of the individual electrode 5 is the n-th level. Sometimes covered with an insulating film.

  As is apparent from the above description, this first manufacturing method performs at least one patterning and insulating film etching on the insulating film 7 formed on the entire surface of the individual electrode 5, or a plurality of times. By repeating the patterning and the insulating film etching, at least one step is formed in the insulating film 7 on the individual electrode 5 in a stepped manner. Therefore, the step is etched on the bottom surface of the recess 32 of the glass substrate 300. Compared with the conventional method to form, the processing precision of a level | step difference improves remarkably. As a result, when the electrostatic actuator is configured, there is an effect that stability of the coupled contact state of the diaphragm 7 is improved.

6). Inkjet Head Manufacturing Method Next, an inkjet head manufacturing method will be described with reference to FIG. Here, the electrode substrate 3 of the first embodiment manufactured as described above is used, but the same applies to the electrode substrates 3 of the other embodiments 2 to 6.

  The cavity substrate 2 is manufactured after the silicon substrate 200 is anodically bonded to the electrode substrate 3 manufactured as described above.

First, for example, a silicon substrate 200 in which a boron diffusion layer 201 having a thickness of 0.8 μm, for example, is formed on the entire surface of one surface of the silicon substrate 200 having a thickness of 280 μm is produced (S7 in FIG. 11). Next, on the surface of the boron diffused layer 201 of the silicon substrate 200 (lower surface), as the insulating film 9, a SiO ₂ film is entirely formed to a thickness of 110nm by thermal oxidation (S8 in FIG. 11, FIG. 16 (A)).

Next, the silicon substrate 200 is aligned on the electrode substrate 3 and anodic bonded (S9 in FIG. 11, FIG. 16B).
Next, the entire surface of the bonded silicon substrate 200 is polished to reduce the thickness to, for example, about 50 μm (S10 in FIG. 11, FIG. 16C), and the entire surface of the silicon substrate 200 is wet etched. To remove the processing trace (S11 in FIG. 11).

  Next, resist patterning is performed by photolithography on the surface of the bonded silicon substrate 200 processed into a thin plate (S12 in FIG. 11), and ink flow channel grooves are formed by anisotropic wet etching using a KOH aqueous solution (FIG. 11). S13). As a result, a recess 22 that becomes the discharge chamber 21, a recess 24 that becomes the reservoir 23, and a recess 27 that becomes the FPC mounting part (electrode extraction part) 34 are formed (FIG. 16D). At this time, since etching is stopped on the surface of the boron diffusion layer 201, the thickness of the diaphragm 6 can be formed with high accuracy and surface roughness can be prevented.

Next, the bottom of the recess 27 is removed by ICP (Inductively Coupled Plasma) dry etching to open the FPC mounting portion 34 (FIG. 16 (e)), and then moisture adhering to the inside of the electrostatic actuator is removed. (S14 in FIG. 11). For the moisture removal, the silicon substrate is placed in, for example, a vacuum chamber, and the moisture is removed by heating and vacuuming. Then, after the required time has elapsed, nitrogen gas is introduced, and a sealing material 35 such as epoxy resin is applied to the gap opening end portion in a nitrogen atmosphere to seal it hermetically (S15 in FIG. 11, FIG. 16 (f)). . Thus, after removing the moisture adhering to the inside of the electrostatic actuator (in the gap), the driving durability of the electrostatic actuator can be improved by hermetically sealing.
Further, the ink supply hole 33 is formed by penetrating the bottom of the recess 24 by microblasting or the like. Further, an ink protective film (not shown) made of a TEOS-SiO ₂ film is formed on the surface of the silicon substrate by plasma CVD in order to prevent corrosion of the ink flow path grooves. A common electrode 26 made of metal is formed on the silicon substrate.

The cavity substrate 2 is manufactured from the silicon substrate 200 bonded to the electrode substrate 3 through the above steps.
Thereafter, the nozzle substrate 1 in which the nozzle holes 11 and the like are formed in advance is bonded onto the surface of the cavity substrate 2 by bonding (S16 in FIG. 11). Finally, by cutting into individual head chips by dicing, the above-described main body of the inkjet head 10 is completed (S17 in FIG. 11, FIG. 16 (g)).

According to the method for manufacturing the inkjet head 10, as described above, an inkjet head including an electrostatic actuator that can secure a stable discharge amount without increasing the drive voltage can be manufactured at low cost. Furthermore, the pressure generated by the electrostatic actuator is improved, and an ink jet head including an electrostatic actuator having excellent withstand voltage, driving durability, and ejection performance can be manufactured at low cost.
Since the cavity substrate 2 is manufactured from the silicon substrate 200 in a state of being bonded to the electrode substrate 3 prepared in advance, the cavity substrate 2 is supported by the electrode substrate 3. Even if it is made thin, it does not break or chip, and handling becomes easy. Therefore, the yield is improved as compared with the case where the cavity substrate 2 is manufactured alone.

(Second manufacturing method of electrode substrate)
Next, the second manufacturing method of the electrode substrate will be described with reference to FIG. 17 taking the case of the second embodiment as an example. Of course, this manufacturing method can also be applied to the other first and third embodiments. FIG. 17 is a schematic cross-sectional view of the manufacturing process showing the second manufacturing method of the electrode substrate according to the second embodiment.
(1) As shown in FIG. 17A, the concave portion 32 and the individual electrode 5 are formed in the concave portion 32 in the glass substrate 300 as described above, and is the same as the step (1) in the first manufacturing method. It is.
(2) Then, a first mask member 310 made of a silicon mask having an opening only on a portion where the first-stage insulating film 7a is formed on the individual electrode 5 is superposed on the glass substrate 300, and ECR (Electron Cyclotron Resonance). A sputtering method is used to form a SiO ₂ film with a thickness of 20 nm (FIG. 17B).
(3) Next, a second mask member 311 made of a silicon mask having an opening only at a portion to be the second-stage insulating film 7b is overlaid on the glass substrate 300, and an SiO ₂ film is formed by using an ECR sputtering method. A film is formed with a thickness of 20 nm (FIG. 17C). As a result, the insulating film 7 having the steps (1) and (2) can be formed on the individual electrode 5 in a form in which the second-stage insulating film 7b is laminated on the first-stage insulating film 7a.
(4) Thereafter, the second mask member 311 is removed, and a hole 33a to be the ink supply hole 33 is formed in the glass substrate 300 by blasting or the like (FIG. 17D).

  This second manufacturing method is a method in which the steps of the insulating film 7 are stacked from the bottom, and a mask member in which the area of the opening 312 is sequentially increased corresponding to the number of steps of the insulating film 7 may be used. Since the process can be simplified as compared with the first manufacturing method, the effect is larger as the number of stages is larger, and it is advantageous for forming the insulating film 7 having a multistage structure.

  In the above embodiment, the electrostatic actuator, the ink jet head, and the manufacturing method thereof have been described. However, the present invention is not limited to the above embodiment, and various modifications are made within the scope of the idea of the present invention. be able to. For example, the electrostatic actuator of the present invention can be used for an optical switch, a mirror device, a micropump, a drive unit of a laser operation mirror of a laser printer, or the like. Moreover, by changing the liquid material discharged from the nozzle holes, for example, in addition to the ink jet printer as shown in FIG. 18, the manufacture of color filters for liquid crystal displays, the formation of light emitting portions of organic EL display devices, genetic testing, etc. It can be used as a droplet discharge device for various uses such as production of a microarray of biomolecule solution to be used.

1 is an exploded perspective view showing a schematic configuration of an inkjet head according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of an inkjet head showing a schematic configuration of a substantially right half of FIG. 1 in an assembled state. The AA expanded sectional view of FIG. FIG. 3 is a top view of the ink jet head of FIG. 2. The expanded sectional view at the time of providing the level | step difference of an insulating film in the width direction of a fixed electrode. FIG. 6 is a schematic cross-sectional view of an inkjet head according to Embodiment 2 of the present invention. FIG. 5 is a schematic cross-sectional view of an inkjet head according to Embodiment 3 of the present invention. FIG. 6 is a schematic cross-sectional view of an ink jet head according to Embodiment 4 of the present invention. FIG. 7 is a schematic cross-sectional view of an ink jet head according to a fifth embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of an inkjet head according to a sixth embodiment of the present invention. The flowchart which shows the outline flow of the manufacturing process of an inkjet head. FIG. 3 is a schematic cross-sectional view of a manufacturing process showing a first manufacturing method of the electrode substrate according to the first embodiment. FIG. 5 is a schematic cross-sectional view of a manufacturing process showing a first manufacturing method of an electrode substrate according to a second embodiment. FIG. 6 is a schematic cross-sectional view of a manufacturing process showing a first manufacturing method of an electrode substrate according to a fourth embodiment. FIG. 6 is a schematic cross-sectional view of a manufacturing process showing a first manufacturing method of an electrode substrate according to a fifth embodiment. FIG. 3 is a schematic cross-sectional view of an inkjet head manufacturing process. FIG. 6 is a schematic cross-sectional view of a manufacturing process showing a second manufacturing method of an electrode substrate according to Embodiment 2. 1 is a schematic perspective view showing an example of an ink jet printer to which an ink jet head of the present invention is applied.

Explanation of symbols

  1 nozzle substrate, 2 cavity substrate, 3 electrode substrate, 4 electrostatic actuator, 5 individual electrode (fixed electrode), 6 diaphragm (movable electrode), 7 insulating film, 7a first stage insulating film, 7b second stage insulation Membrane, 9 Insulating film, 10 Inkjet head, 11 Nozzle hole, 12 Orifice, 13 Diaphragm part, 21 Discharge chamber, 23 Reservoir, 26 Common electrode, 32 Recessed part, 33 Ink supply hole, 34 Electrode takeout part (FPC mounting part), 35 sealing material, 36 joint, 40 drive control circuit (drive means), 200 silicon substrate, 300 glass substrate, 310 first mask member, 311 second mask member, 312 mask member opening, 500 inkjet printer .

Claims (13)

An electrostatic force is generated between the fixed electrode formed on the glass substrate, the movable electrode disposed in parallel to the fixed electrode with a predetermined gap therebetween, and the fixed electrode and the movable electrode. In the electrostatic actuator comprising a driving means for causing displacement of the movable electrode,
An electrostatic actuator comprising an insulating film having at least one stepped step on a surface of the fixed electrode facing the movable electrode.    The electrostatic actuator according to claim 1, wherein the insulating film has a stepped step in a longitudinal direction or a width direction of the fixed electrode.   3. The electrostatic actuator according to claim 1, wherein the insulating film is formed in an arbitrary number of steps on an opposing surface of the fixed electrode other than the deepest portion of the gap.   The electrostatic actuator according to claim 1, wherein the insulating film includes at least a silicon oxide film.   The electrostatic actuator according to claim 1, wherein the insulating film includes at least a diamond-like carbon film.   The electrostatic actuator according to claim 1, wherein the insulating film includes a dielectric film made of a dielectric material having a relative dielectric constant larger than that of at least silicon oxide. At least one of aluminum oxide (Al ₂ O ₃ ), hafnium oxide (HfO ₂ ), hafnium nitride silicate (HfSiN), and hafnium oxynitride silicate (HfSiON) is selected as a dielectric material having a higher dielectric constant than silicon oxide. The electrostatic actuator according to claim 6. An electrostatic force is generated between the fixed electrode formed on the glass substrate, the movable electrode disposed in parallel to the fixed electrode with a predetermined gap therebetween, and the fixed electrode and the movable electrode. In the manufacturing method of an electrostatic actuator comprising a driving means for causing displacement of the movable electrode,
Forming an insulating film on the entire surface of the glass substrate on which the fixed electrode is formed;
A patterning step of patterning the insulating film formed on the entire surface;
An insulating film etching step for selectively removing the portion of the insulating film exposed by the patterning by etching;
An insulating film having one or more stepped steps is formed on the fixed electrode by repeating the patterning step and the insulating film etching step at least once or a plurality of times. Production method.   9. The method of manufacturing an electrostatic actuator according to claim 8, wherein, in the insulating film etching step, the insulating film is removed by dry etching. An electrostatic force is generated between the fixed electrode formed on the glass substrate, the movable electrode disposed in parallel to the fixed electrode with a predetermined gap therebetween, and the fixed electrode and the movable electrode. In the manufacturing method of an electrostatic actuator comprising a driving means for causing displacement of the movable electrode,
A method of manufacturing an electrostatic actuator, wherein an insulating film having one or more stepped steps is formed on the fixed electrode by sputtering using a mask member.   A droplet discharge head comprising the electrostatic actuator according to claim 1.   A method for manufacturing a droplet discharge head, wherein the droplet discharge head is manufactured by applying the method for manufacturing an electrostatic actuator according to claim 8.   A droplet discharge apparatus comprising the droplet discharge head according to claim 11.

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