JP4797589B2 - Electrostatic actuator, droplet discharge head, droplet discharge apparatus, and electrostatic device - Google Patents

Description

  The present invention relates to an electrostatic actuator, a droplet discharge head using the same, a droplet discharge apparatus and an electrostatic device, a method for manufacturing an electrostatic actuator, and a method for manufacturing a droplet discharge head.

As an ink discharge method in an ink jet recording apparatus, a so-called electrostatic driving ink jet recording apparatus using electrostatic force as a driving unit is known. The electrostatic drive type ink jet recording apparatus performs an operation of attracting and isolating the diaphragm from the counter electrode by supplying / cutting off a voltage between the diaphragm and the counter electrode which is a fixed electrode. Ink is ejected using pressure change. Therefore, the diaphragm and the counter electrode act as an electrostatic actuator that varies the pressure in the pressure chamber in which ink is stored. In an apparatus to which such an electrostatic actuator is applied, an insulating film of a silicon oxide film is generally formed between a charged diaphragm and a counter electrode to prevent dielectric breakdown or short circuit (for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-165413

  However, the conventional insulating film has a problem that the electrostatic suction pressure is not stabilized due to the influence of the residual charge on the surface of the insulating film, and the stable driving of the actuator cannot be secured. In addition, when the insulating film is thick, the electrostatic attractive force is reduced, which makes it difficult to reduce the size and increase the density of the electrostatic actuator.

  The present invention has been made in response to the above-mentioned problems. A first object of the present invention is to obtain an electrostatic actuator capable of stable driving by reducing the influence of residual charges between the diaphragm and the counter electrode. And It is a second object of the present invention to obtain a small-sized electrostatic actuator with excellent driving durability, which can reduce the actuator driving voltage. In addition to these, a droplet discharge head, a droplet discharge device, and an electrostatic device provided with the electrostatic actuator are obtained, and a manufacturing method thereof is proposed.

Electrostatic actuator of the present invention, a plurality of silicon diaphragm to have a parallel side by side are formed flexible to act as one electrode, opposite to the diaphragm with a gap in the diaphragm A plurality of counter electrodes to which a voltage is applied, and an insulating film formed on a surface of the diaphragm facing the counter electrode, wherein the insulating film is formed When a surface layer made of diamond-like carbon is formed on each surface of the opposing surface of the diaphragm and the counter electrode, and the direction in which the plurality of diaphragms are arranged in parallel is a width direction, The width and the width of each counter electrode facing each diaphragm are set equal, and the width of each surface layer in the width direction is set narrower than the width of each diaphragm and each counter electrode, and the surface The layer is driven by the vibration. A dielectric protective film having a relative dielectric constant larger than that of silicon oxide is formed on a surface of the surface where the plate and the counter electrode are in contact with each other, and the surface thereof is water-repellent. And the surface layer is formed on the protective film.
Thus, by forming a surface layer made of diamond-like carbon on each surface of the opposing surface of the diaphragm and the counter electrode, the hydroxyl group density on the outermost surface of the diaphragm becomes extremely small, and The charge density and surface residual charge due to moisture adsorption are suppressed, and the electrostatic actuator can be stably driven and the durability can be improved.

It is preferable that the surface layer is partitioned and formed on a surface where the diaphragm and the counter electrode come into contact with each other by driving. By doing so, adsorption of the diaphragm to the counter electrode can be prevented with a minimum film stress, and stable driving of the electrostatic actuator can be realized.
When the surface layer is formed on the counter electrode side, a dielectric protective film is preferably formed on the surface of the counter electrode, and a carbon material is preferably formed on the protective film. Thereby, the withstand voltage can be improved and the oxidation of the electrode when the carbon material deposited on the substrate is patterned into a predetermined shape can be prevented.

A droplet discharge head of the present invention includes any one of the electrostatic actuators described above, and the diaphragm constitutes a bottom surface of a pressure chamber that stores and discharges droplets. According to this droplet discharge head, the influence of the residual charge of the actuator is suppressed and stable driving is possible. Therefore, highly accurate and stable ink discharge characteristics are ensured, and high printing characteristics can be obtained.
Moreover, a droplet discharge device of the present invention includes the above-described droplet discharge head.
Furthermore, an electrostatic device of the present invention includes any one of the electrostatic actuators described above.

Embodiment 1 (electrostatic actuator)
FIG. 1 is a longitudinal sectional view of an electrostatic actuator according to Embodiment 1 of the present invention. The electrostatic actuator according to the first embodiment includes a flexible diaphragm 12 that functions as one electrode, and an electrode in which a counter electrode 17 facing the diaphragm 12 with a gap 10 is formed in the groove. A drive circuit 20 (block display in FIG. 1) that applies a pulse voltage to the substrate 3, the diaphragm 12, and the counter electrode 17 is provided.

The diaphragm 12 is made of a silicon substrate, and an insulating film 16B and a surface layer 16C are laminated on the surface facing the counter electrode 17.
The insulating film 16 </ b> B functions to prevent dielectric breakdown and short circuit between the diaphragm 12 and the counter electrode 17 when the diaphragm 12 is driven. Silicon oxide can be used as the insulating film 16B. However, as the insulating film 16B, any one of aluminum oxide, silicon oxynitride, tantalum oxide, hafnium silicate, or hafnium oxynitride silicate having a relative dielectric constant larger than that of silicon oxide (3.2) is used. In addition, it can be made thicker than silicon oxide to ensure the same electrostatic attraction pressure and further ensure high insulation resistance. In other words, the required insulation resistance can be ensured by reducing the equivalent oxide thickness (EOT).

On the other hand, the surface layer 16 </ b> C functions to prevent charging of the outermost surface of the diaphragm 12. A preferable film forming material for the surface layer 16C is a carbon material such as diamond-like carbon (hereinafter referred to as DLC), diamond, fullerene C60, or carbon nanotube. The fullerene C60 attaches ultrafine particles having a diameter of about 0.7 nm to the surfaces of the insulating film 16B and the counter electrode 17, and the carbon nanotubes plant the surface layer 16C by flocking the surfaces of the insulating film 16B and the counter electrode 17. Can be formed.
By using DLC or the like for the surface layer 16C, the density of hydroxyl groups on the outermost surface of the diaphragm 12 becomes extremely small, the surface charge density of the diaphragm 12 and the surface residual charge due to moisture adsorption are suppressed, and the diaphragm 12 is stabilized. Drive becomes possible. In particular, by providing the surface layer 16C on the surface where the diaphragm 12 and the counter electrode 17 abut, stable driving can be realized with a minimum film stress. Further, since the hardness of the contact surface between the diaphragm 12 and the counter electrode 17 is increased, the true contact area is reduced, and the contact charge amount, that is, the surface residual charge is also reduced.

  The electrode substrate 3 is made of, for example, borosilicate glass, and a plurality of counter electrodes 17 facing the diaphragm 12 with a gap 10 therebetween are formed in the groove. The gap 10 is set between 100 and 300 nm, for example. The counter electrode 17 can be formed, for example, by sputtering ITO (Indium Tin Oxide).

  Here, the operation of the electrostatic actuator will be described. By controlling the drive circuit 20 to supply / shut off the voltage between the diaphragm 12 and the counter electrode 17, the diaphragm 12 is bent and brought into contact with the counter electrode 17, and the diaphragm 12 is brought into contact with the counter electrode. The operation of returning to the original position away from 17 is performed. The electrostatic actuator using such an operation of the diaphragm 12 can be applied to various apparatuses and devices.

According to the electrostatic actuator, the surface layer 16C suppresses the charge density at the outermost surface of the diaphragm 12 and the surface residual charge. Therefore, adsorption of the diaphragm 12 to the counter electrode 17 is prevented, and the electrostatic actuator can be driven stably.
In addition, if the insulating film 16B is formed of aluminum oxide or the like having a relative dielectric constant larger than that of silicon oxide, the equivalent oxide thickness (EOT) can be reduced to ensure a dielectric breakdown voltage. Voltage power can be increased. As a result, the actuator drive voltage can be lowered, and a small electrostatic actuator with excellent driving durability can be obtained.
The same effect can be obtained even when the surface layer 16C is formed not on the surface of the diaphragm 12 but on the surface of the counter electrode 17.

Embodiment 2 (Droplet ejection head)
Next, a droplet discharge head to which the electrostatic actuator of Embodiment 1 is applied will be described.
Example 1
FIG. 2 is a longitudinal sectional view showing a droplet discharge head according to Example 1 of Embodiment 2 of the present invention, and FIG. 3 is a cross section near the pressure chamber when the droplet discharge head of FIG. FIG. In this droplet discharge head 1, a cavity substrate 2, an electrode substrate 3, and a nozzle substrate 4 are laminated and bonded, and a flexible vibration plate 12 formed on the cavity substrate 2 and an electrode substrate 3. The counter electrode 17 which is the formed fixed electrode constitutes an electrostatic actuator. The counter electrode 17 is also called an individual electrode because it is formed for each corresponding pressure chamber. In FIG. 2, only the insulating film 16B is displayed on the surface of the diaphragm 12 facing the counter electrode 17, and the surface layer (corresponding to the reference numeral 16C in FIG. 1) is not shown.

  The cavity substrate 2 is made of, for example, single crystal silicon, has a bottom wall formed as a diaphragm 12, and a plurality of concave portions serving as pressure chambers (also referred to as discharge chambers) 13 for storing and discharging the discharge liquid. The pressure chambers 13 are formed in parallel from the front side to the back side in FIG. 2, and the diaphragm 12 constituting the bottom surface of the pressure chamber 13 is boron-doped by diffusing boron (B) from the silicon substrate surface. It is formed as a layer. The cavity substrate 2 has a recess serving as a reservoir 14 for supplying a droplet of ink or the like to each pressure chamber 13, and a recess serving as a narrow groove-like orifice 15 that communicates the reservoir 14 with each pressure chamber 13. Is formed. The reservoir 14 is formed from a single recess, and one orifice 15 is formed for each pressure chamber 13. The orifice 15 may be formed on the nozzle substrate 4.

  The insulating film 16B and the surface layer 16C described in the first embodiment are formed on the surface of the cavity substrate 2 where the electrode substrate 3 is bonded. On the other hand, a droplet-proof protective film 19 is formed on the surface of the cavity substrate 2 on the side where the nozzle substrate 4 is bonded. The droplet-resistant protective film 19 is for preventing the cavity substrate 2 from being etched by droplets inside the pressure chamber 13 and the reservoir 14.

  The electrode substrate 3 is made of, for example, borosilicate glass, and is bonded so as to face the diaphragm 12 of the cavity substrate 2. A plurality of counter electrodes 17 are formed on the electrode substrate 3 to face the diaphragm 12 with a gap 10 therebetween. The gap 10 is sealed with a sealing material 11. The counter electrode 17 can be formed, for example, by sputtering ITO (Indium Tin Oxide). A discharge liquid supply port 18 communicating with the reservoir 14 is formed in the electrode substrate 3. The discharge liquid supply port 18 is connected to a hole provided in the bottom wall of the reservoir 14 and is provided to supply droplets such as ink to the reservoir 14 from the outside.

  The nozzle substrate 4 is a substrate provided with a plurality of nozzles 8 corresponding to the pressure chambers, and is bonded to the surface of the cavity substrate 2 opposite to the surface where the electrode substrate 3 is bonded. The nozzle substrate 4 is made of silicon or the like, and the nozzle 8 includes, for example, a cylindrical first nozzle hole and a cylindrical second nozzle that communicates with the first nozzle hole and has a larger diameter than the first nozzle hole. It consists of holes.

In the actuator portion of the droplet discharge head 1, the DLC film forming the surface layer 16C is provided in a portion where the diaphragm 12 and the counter electrode 17 are adsorbed, and the residual charge remaining in the adsorbed portion is efficiently removed. In addition to the suppression, the bonding strength such as the anodic bonding of the electrode substrate 3 and the cavity substrate 2 and the airtightness are ensured.
In the example shown in FIG. 3, the thickness of the insulating film (SiO ₂ ) 16B is 80 nm, the surface layer (DLC film) 16C is 10 nm, and the thickness ratio of the SiO ₂ film having excellent withstand voltage is increased. ing. The distance of the gap 10 is 110 nm. Further, in order to suck the diaphragm 12 to the counter electrode 17 efficiently, the width of the diaphragm 12 and the width of each counter electrode 17 are set to be substantially equal, and the width of the surface layer 16C is set to be narrower than that of the diaphragm 12. Yes. Thus, by setting the width of the surface layer 16C to be narrower than the width of the diaphragm 12, the problem that the diaphragm 12 is bent due to a large film stress of the DLC film of the surface layer 16C is eliminated.

  Since the DLC film is hard and the real contact area when the diaphragm 12 is adsorbed to the counter electrode 17 is small, the residual charge due to contact charging of the insulating film 16B can be reduced. In addition, since it is a diamond-like film, it is difficult to form hydroxyl groups on the surface when all the orbitals of the SP3 hybrid orbits constituting the crystal are filled with electrons. Electric charge can also be reduced. Instead of the DLC film, a diamond thin film formed by CVD which is also hard and does not form a hydroxyl group on the surface may be formed. According to the diamond thin film, a harder and denser surface layer can be formed. Therefore, the surface layer 16C is superior to the DLC film for the purpose of reducing residual charges. However, the DLC film can form a desired surface layer more easily than the diamond thin film.

  Next, the operation of the droplet discharge head 1 shown in FIG. 3 will be described. A drive circuit 20 is connected to the cavity substrate 2 and each counter electrode 17. When a pulse voltage is applied between the cavity substrate 2 and the counter electrode 17 by the drive circuit 20, the diaphragm 12 is attracted to the counter electrode 17 and the surface layer 16 </ b> C is adsorbed to the counter electrode 17. As a result, a negative pressure is generated in the pressure chamber 13, and a liquid such as ink that has accumulated in the reservoir 14 flows into the pressure chamber 13. When the voltage applied between the cavity substrate 2 and the electrode 17 is released at the timing when the pressure inside the pressure chamber 13 increases due to the liquid that has flowed in, the diaphragm 12 returns to its original position and returns to the pressure chamber. Since the pressure inside 13 further rises and becomes higher, droplets are ejected from the nozzle 8.

Example 2
Here, an example of a droplet discharge head in which the surface layer 16C is formed on the counter electrode 17 that is a fixed electrode instead of the surface of the diaphragm 12 will be described. FIG. 4 is an enlarged view of the vicinity of the pressure chamber of the droplet discharge head according to the second embodiment corresponding to FIG. The droplet discharge head has the same configuration as the droplet discharge head of FIG. 2 except that the surface layer 16C is formed on the counter electrode 17.
Here, the insulating film (SiO ₂ ) 16B is 80 nm, and the surface layer (DLC film) 16C is 10 nm. The gap determined by the distance between the insulating film 16B and the surface layer 16C is 110 nm. In addition, since the width of the diaphragm 12 in contact with the counter electrode 17 is narrower than the width of the counter electrode 17, the surface layer C 16 is considered in consideration of misalignment of partition formation by patterning of the surface layer 16 C with respect to the counter electrode 17. Is set to be narrower than the width of the counter electrode 17. Since the DLC is hard and the real contact area between the DLC film and the SiO ₂ film when the diaphragm 12 is adsorbed to the counter electrode 17 is small, the residual charge due to the contact charging of the insulating film 16B can be reduced even in this configuration. In the liquid droplet ejection head of Example 2, the cavity substrate 2 only needs to be provided with an insulating film (dielectric layer), so that the cavity substrate 2 can be easily manufactured.

Example 3
Here, the example which further changed the arrangement | positioning aspect of the surface layer 16C of Example 2 is shown. FIG. 5 is an enlarged view of the vicinity of the pressure chamber of the droplet discharge head according to the third embodiment corresponding to FIG. This droplet discharge head has the same configuration as the droplet discharge head of FIG. 2 except that the surface layer 16C is formed on the dielectric layer formed on the counter electrode 17.
In Example 3, a protective film 16D is formed on the surface of the counter electrode 16, and a surface layer 16C is formed on the protective film 16D. The protective film 16D preferably has both functions of a dielectric and an insulator. Silicon oxide, aluminum oxide, silicon oxynitride, tantalum oxide, hafnium silicate, or the like is formed. Thereby, when the surface layer 16C is partitioned and formed on the counter electrode 17 using oxygen plasma or the like, the counter electrode 17 can be prevented from being oxidized. In the case of Example 3, the film thicknesses are, for example, 60 nm for the insulating film 16B, 10 nm for the surface layer 16C, and 30 nm for the protective film 16D.

  In FIGS. 3 to 5, the surface layer 16C is provided on one of the opposing surfaces of the diaphragm 12 and the counter electrode 17, but the surface layer 16C may be provided on both of the opposing surfaces. . In this case, since the real contact area when the diaphragm 12 and the counter electrode 17 are in contact with each other becomes smaller, it is possible to further reduce the residual charge due to contact charging and the influence on the fluctuation of the drive voltage.

(Manufacturing method of the droplet discharge head-in the case of the droplet discharge head shown in FIG. 3)
FIG. 6 is a flowchart showing manufacturing steps of the droplet discharge head according to the first embodiment.
(A) First, the electrode substrate 3 is manufactured (S0). For example, the electrode substrate 3 is formed by applying a gold / chromium etching mask to a borosilicate glass substrate, etching the glass substrate with a hydrofluoric acid aqueous solution or the like to form a recess (or a groove), and then sputtering the ITO into the recess by sputtering or the like. The counter electrode 17 can be formed.
(B) Next, for example, a silicon substrate having a thickness of 525 μm to be a cavity substrate is prepared. The silicon substrate is mirror-polished on both sides, and boron is doped on one side surface to form a boron dove layer having a thickness of about 2 μm, for example. This boron dove layer will later become the diaphragm 12. Further, an insulating film (or dielectric layer) 16B is formed on the surface of the silicon substrate on which the boron dove layer is formed (S1). The insulating film 16B is preferably formed by forming a dense silicon oxide film having excellent insulating properties by TESO plasma CVD. The insulating film 16B may be formed of aluminum oxide or silicon oxynitride by an ALD (Atomic Layer Deposition) method, ECR sputtering, or plasma CVD.
(C) Subsequently, a surface layer 16C is formed on the surface of the insulating film 16B. The surface layer 16C is formed by depositing DLC or diamond by RF plasma CVD or the like (S2). Alternatively, the surface layer 16C may be formed by a method of attaching ultrafine particles of fullerene C60 to the surface of the insulating film 16B or a method of implanting carbon nanotubes on the surface of the insulating film 16B.
Further, after patterning the surface layer 16C with a dry film resist to protect the portion corresponding to the contact portion with the counter electrode 17 (S3), excess DLC is oxidized and removed by oxygen plasma (S4). If oxygen plasma is used, carbon materials such as DLC and diamond thin film can be efficiently oxidized and removed to form compartments.
The surface of the formed surface layer 16C is subjected to hydrogen termination by surface treatment with a nitric acid-based or hydrofluoric acid-based cleaning liquid and rinsing before the step S3, thereby reducing surface hydroxyl groups, It should be water-repellent.

(D) The silicon substrate on which the insulating layer 16B is formed as described above is bonded to the electrode substrate 3 on which the counter electrode 17 is formed (S5). Here, the electrode substrate 3 is heated to, for example, 360 ° C., an anode is connected to the silicon substrate, and a cathode is connected to the electrode substrate 3. A voltage of about 800 V is applied and bonded by anodic bonding. Note that the silicon substrate and the electrode substrate can be joined with an adhesive. After the bonding, the inner wall surface of the gap 10 formed by the silicon substrate and the electrode substrate is hydrophobized with a silane-based or fluorine-based processing agent for the purpose of suppressing the accumulation of residual charges. It is preferable to leave.
(E) Subsequently, the entire silicon substrate bonded to the electrode substrate 3 is thinned to a thickness of about 140 μm by, for example, mechanical grinding (S6). After mechanical grinding, it is desirable to perform light etching with an aqueous potassium hydroxide solution or the like to remove the work-affected layer (S7). Instead of mechanical grinding, the silicon substrate may be thinned by wet etching with an aqueous potassium hydroxide solution.
(F) Then, a silicon oxide film having a thickness of, for example, 1.5 μm is formed on the entire upper surface of the silicon substrate (the surface opposite to the surface to which the electrode substrate 3 is bonded) by TEOS plasma CVD. Then, the silicon oxide film is patterned with a resist for forming a concave portion to be the pressure chamber 13, a concave portion to be the reservoir 14, and a concave portion to be the orifice, and the silicon oxide film in this portion is removed by etching. (S8).

(G) Thereafter, the silicon substrate is anisotropically wet etched with an aqueous potassium hydroxide solution or the like to thereby form a recess to be the pressure chamber 13, a recess to be the reservoir 14 (not shown), and a recess to be the orifice (not shown). After that, the silicon oxide film is removed (S9). In this wet etching step, it is preferable to perform two-stage etching using, for example, a 35% by weight potassium hydroxide aqueous solution first and then a 3% by weight potassium hydroxide aqueous solution. This is because surface roughness of the diaphragm 12 can be suppressed. In the above etching process, the previously formed boron doped layer acts as an etch stop, and the remaining boron doped layer is formed as the diaphragm 12.
Thereafter, a droplet-resistant protective film made of silicon oxide or the like is formed with a thickness of, for example, 0.1 μm on the surface of the silicon substrate on which the recesses or the like that will become the pressure chambers 13 are formed. Further, a gap formed between the vibration plate 12 of the silicon substrate and the counter electrode of the electrode substrate is sealed (S10).
(H) Next, the nozzle substrate 4 on which the nozzle 8 is formed by dry etching or the like by ICP (Inductively Coupled Plasma) discharge is opposite to the side where the electrode substrate 3 of the silicon substrate (same as the cavity substrate 2) is bonded. Bonded to the side by an adhesive or the like (S11).
(I) Finally, for example, the bonded substrate to which the cavity substrate 2, the electrode substrate 3, and the nozzle substrate 4 are bonded is separated by dicing (cutting), thereby completing the droplet discharge head 1 (S12).

  According to the method for manufacturing a droplet discharge head according to the process of FIG. 6, it is possible to suppress the influence of residual charges on the surface layer 16 </ b> C constituting the surface of the diaphragm 12, and the droplet discharge that enables stable driving. The head can be manufactured. Further, by forming a material having a relative dielectric constant higher than that of silicon oxide as the insulating film 16B, a necessary withstand voltage is ensured between the diaphragm 12 and the counter electrode 17 even if the thickness of the insulating film is reduced. Therefore, it is possible to manufacture a droplet discharge head that is small in size and excellent in driving durability, in which the actuator driving voltage is reduced.

(Droplet Discharge Head Manufacturing Method—Droplet Discharge Head Shown in FIG. 4)
FIG. 7 is a flowchart showing manufacturing steps of the droplet discharge head according to the second embodiment.
(A) First, the electrode substrate 3 is formed. For example, the electrode substrate 3 is formed by applying a gold / chromium etching mask to a borosilicate glass substrate, etching the glass substrate with a hydrofluoric acid aqueous solution or the like to form a recess (or a groove), and then sputtering the ITO into the recess by sputtering or the like. The counter electrode 17 is formed (S01).
(B) Subsequently, a surface layer 16C is formed on the side of the electrode substrate 3 on which the counter electrode 17 is formed. The surface layer 16C is formed by depositing DLC or diamond by plasma CVD (S02). When manufacturing the droplet discharge head of Example 3, the dielectric layer 16D is formed on the surface of the counter electrode 17, and then DLC or diamond is formed.
(C) Further, the surface layer 16C is patterned with a dry film resist to protect the portion corresponding to the counter electrode and the contact portion (S03). In consideration of misalignment of partition formation due to patterning of the DLC film with respect to the counter electrode 17, the DLC film is preferably slightly narrower than the width of the counter electrode 17 as shown in FIG. 4.
(D) Then, excess DLC is oxidized and removed by oxygen plasma, and then the dry film resist is peeled off (04).
(E) Thereafter, a discharge liquid supply port is opened in the electrode substrate 3 by using a drill or the like (S05).
(F) On the other hand, for example, a silicon substrate having a thickness of 525 μm to be a cavity substrate is prepared. The silicon substrate is mirror-polished on both sides, and boron is doped on one side surface to form a boron dove layer having a thickness of about 2 μm, for example. This boron dove layer will later become the diaphragm 12. Further, an insulating film 16B is formed on the surface of the silicon substrate where the boron dove layer is formed. The insulating film 16B can be formed by forming a dense and excellent insulating silicon oxide film by TESO plasma CVD. The insulating film 16B may be formed of aluminum oxide or silicon oxynitride by ALD, ECR sputtering, or plasma CVD (S1).
(G) Then, the surface on which the surface layer 16C is formed and the surface on which the insulating film 16B is formed are opposed to the electrode substrate 3 on which the steps S01 to S05 are completed and the silicon substrate on which the step S1 is completed. And anodic bonding (S5). Thereafter, the same steps as S6 to S12 in FIG. 6 are performed to complete the droplet discharge head.

  Also by the above method of FIG. 7, substantially the same effect as the method of FIG. 6 can be obtained. In addition, according to the method of FIG. 7, since the surface layer 16C is not formed on the cavity substrate, the processing of the cavity substrate is simplified correspondingly.

Embodiment 3 (Droplet Discharge Device)
FIG. 8 is an external view showing an example of a droplet discharge device according to a third embodiment of the present invention that includes the droplet discharge head according to the second embodiment. A droplet discharge device 100 shown in FIG. 8 is an inkjet printer that discharges ink as droplets. In this droplet discharge device 100, the effect of the residual charge in the electrostatic actuator portion is reduced by the action of the droplet discharge head employed therein, and therefore, highly accurate ink discharge by stable driving becomes possible. Further, the droplet discharge device 100 can be driven with low power, and is small in size and excellent in driving durability.
In addition to the ink jet printer shown here, the droplet discharge head according to the second embodiment can form a matrix pattern of a color filter and a light emitting portion of an organic EL display device by changing various droplets to be discharged. The present invention can also be applied to a droplet discharge device that discharges a biological liquid sample.

Embodiment 4 (electrostatic device)
FIG. 9 is a perspective view showing an example of the electrostatic device according to the fourth embodiment of the present invention including the electrostatic actuator according to the first embodiment. The electrostatic device shown in FIG. 9 is a wavelength tunable filter 200, which includes a drive electrode unit 210, a movable unit 220, and a package unit 230, and uses a position variation of the movable unit 220 to specify a specific wavelength from incident light. It filters light of wavelength and emits it.

The movable part 220 has a movable reflection surface 223, and is displaced in a direction perpendicular to the surface direction of the movable reflection surface 223 so as to transmit light having a predetermined wavelength and reflect light having a wavelength other than the predetermined wavelength. The connecting portion 221b and the supporting portions 221c and 221d that support the movable body 221a so as to be displaceable, and the spacer 221e that forms a space on the opposite side of the movable reflecting surface 223 are integrally formed. The movable body 221a is made of, for example, a silicon active layer having a thickness of 1 μm to 10 μm.
The drive electrode section 210 is arranged with the movable body 221a and the electrostatic gap having an EG, and is opposed to the movable body 221a and constitutes the other electrode, the movable reflection surface 223, and the optical gap. A spacer 221e is formed so that the movable reflective surface 223 and the fixed reflective surface 218 are opposed to each other. The fixed reflective surface 218 further reflects the light reflected by the movable reflective surface 223. The movable portion 220 is joined to the opposite side to the above-mentioned side. For example, a glass substrate can be used as the base material of the drive electrode unit 210.
The package part 230 is joined to the tip of the spacer 221e so as to close the space formed by the spacer 221e of the movable part 220.

  In the wavelength tunable filter 200 having the above configuration, the movable body 221a corresponds to the diaphragm 12 of the first embodiment, and the drive electrode 212 corresponds to the counter electrode 17 of the first embodiment, which constitute an electrostatic actuator. Yes. Therefore, by forming an insulating layer corresponding to the insulating layer 16 of Embodiment 1 on the surface of the movable body 221a on the driving electrode 212 side, the influence of the residual charge of the electrostatic actuator is reduced, and the operation of the movable body 221a is stable. In addition, highly accurate optical filtering is possible. In addition, the withstand voltage and electrostatic pressure of the electrostatic actuator are improved, and the wavelength tunable filter 200 can be made compact and excellent in driving durability.

  Thus, the electrostatic actuator according to the present invention can be used as an actuator for various devices, particularly a micromachine. For example, the pump unit of the micro pump, the switch drive unit of the optical switch, the mirror drive unit of the mirror device that controls the direction of the light by tilting these mirrors, and further lasers The electrostatic actuator according to the present invention can be applied to a drive unit of a laser scanning mirror of a printer.

1 is a longitudinal sectional view of an electrostatic actuator according to Embodiment 1 of the present invention. FIG. 6 is a longitudinal sectional view of a droplet discharge head according to Embodiment 2 of the present invention. FIG. 3 is an enlarged cross-sectional view of the vicinity of a pressure chamber according to Embodiment 1 of the droplet discharge head of FIG. 2. FIG. 4 is an enlarged cross-sectional view of the vicinity of a pressure chamber according to a second embodiment of the droplet discharge head of FIG. 2. FIG. 6 is an enlarged cross-sectional view of the vicinity of a pressure chamber according to a third embodiment of the droplet discharge head of FIG. 2. 6 is a flowchart showing a manufacturing process of the droplet discharge head according to the first embodiment. 9 is a flowchart showing a manufacturing process of a droplet discharge head according to the second embodiment. FIG. 6 is an external view showing an example of a droplet discharge device according to a third embodiment of the present invention on which the electrostatic actuator according to the present invention is mounted. The perspective view which shows an example of the device which concerns on Embodiment 4 of this invention carrying the electrostatic actuator which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Droplet discharge head, 2 cavity substrate, 2a silicon substrate, 3 electrode substrate, 4 nozzle substrate, 8 nozzle, 10 gap, 11 sealing material, 12 diaphragm, 13 pressure chamber, 14 reservoir, 15 orifice, 16B insulating film (Or dielectric film), 16C surface layer, 16D insulating film (or dielectric film), 17 counter electrode, 18 discharge liquid supply port, 19 droplet-resistant protective film, 20 drive circuit, 100 droplet discharge device, 200 wavelength Variable filter.

Claims (4)

A plurality of silicon diaphragm to have a parallel side by side are formed flexible to act as one electrode, a voltage is applied between opposing said diaphragm with a gap in the diaphragm and a plurality of counter electrodes, a said electrostatic actuator to the surface facing the counter electrode insulating film is formed of the diaphragm,
A surface layer made of diamond-like carbon is formed on each surface of the opposing surface of the diaphragm and the counter electrode on which the insulating film is formed,
When the direction in which the plurality of diaphragms are arranged in parallel is a width direction, the width of each diaphragm and the width of each counter electrode facing each diaphragm are set to be equal, and each surface layer in the width direction is The width is set narrower than the width of each diaphragm and the width of each counter electrode ,
The surface layer is partitioned and formed in a contact portion of a surface where the diaphragm and the counter electrode abut by driving, and the surface is water-repellent.
An electrostatic actuator, wherein a protective film made of a dielectric having a relative dielectric constant larger than that of silicon oxide is formed on the surface of the counter electrode, and the surface layer is formed on the protective film.   A droplet discharge head comprising the electrostatic actuator according to claim 1, wherein the vibration plate constitutes a bottom surface of a pressure chamber for storing and discharging droplets.   A droplet discharge apparatus comprising the droplet discharge head according to claim 2.   An electrostatic device comprising the electrostatic actuator according to claim 1.

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