JP5560535B2 - Electrostatic actuator - Google Patents

Description

  The present invention relates to an electrostatic actuator, a droplet discharge head, a manufacturing method of the electrostatic actuator, 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 opposite to the individual electrode via a predetermined gap. The electrostatic actuator part comprised from these is provided. 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 this type of electrostatic actuator, it is required to improve the driving stability and driving durability of the actuator. As a technology that meets this requirement, there has conventionally been a technique in which diamond-like carbon (hereinafter referred to as DLC) is formed as a surface layer on at least one facing surface where the diaphragm of the actuator and the individual electrode face each other (for example, , See Patent Document 1). According to this technology, the opposing contact surfaces are made of DLC, which is a hard material with a low coefficient of friction, thereby preventing damage and wear due to contact, improving reliability, and enabling longer life. It was.

JP 2007-136856 A

  In the above-mentioned Patent Document 1, the use of DLC on the opposing surfaces of the diaphragm and the individual electrodes enables an improvement in driving durability and a longer life. However, in order to increase the life more efficiently, It is necessary to stabilize the driving of the diaphragm and improve the durability with a simple configuration.

  The present invention has been made in view of such points, and an electrostatic actuator, a droplet discharge head, an electrostatic actuator manufacturing method, and a liquid that can improve driving durability and reliability with a simple configuration. It aims at providing a droplet discharge device.

An electrostatic actuator according to the present invention includes a fixed electrode formed in a concave portion on a substrate, and a movable electrode disposed to face the fixed electrode with a predetermined gap therebetween, and the gap is between the fixed electrode and the movable electrode. In an electrostatic actuator that generates an electrostatic force to cause displacement of a movable electrode, the fixed electrode is composed of a conductive amorphous carbon-based thin film.
In this way, the fixed electrode is made of a conductive amorphous carbon-based thin film that is a hard material with a low coefficient of friction. Therefore, the durability of the drive by repeated contact and release of the movable electrode is improved and it has excellent durability. A highly reliable electrostatic actuator can be realized. In addition, since the fixed electrode itself is composed of an amorphous carbon-based thin film, the structure can be made simpler than the conventional structure in which an amorphous carbon-based thin film is further formed on the fixed electrode for the purpose of improving driving durability.

The electrostatic actuator according to the present invention includes a fixed electrode formed in a recess on the substrate, and a movable electrode disposed opposite to the fixed electrode via a predetermined gap, and includes a fixed electrode and a movable electrode. In an electrostatic actuator that generates a displacement in the movable electrode by generating an electrostatic force between them, the fixed electrode is composed of a facing portion that faces the movable electrode and other wiring portions, and the facing portion is made of conductive amorphous carbon. The wiring portion is made of a film having higher conductivity than the conductive amorphous carbon thin film.
In this way, among the fixed electrodes, the facing part facing the movable electrode in particular is composed of a conductive amorphous carbon thin film, and the wiring part is composed of a low resistance film having higher conductivity than the conductive amorphous carbon thin film. By doing, resistance can be made low compared with the case where the whole fixed electrode is comprised with an electroconductive amorphous carbon-type thin film. Therefore, when it is attempted to secure the same responsiveness as in the case where the entire fixed electrode is made of a conductive amorphous carbon-based thin film with this configuration, the opposing portion of the fixed electrode has a high resistance corresponding to the low resistance of the wiring portion. Even that would be acceptable. Specifically, the same function and performance (conductivity and responsiveness) can be ensured even if the conductive amorphous carbon-based thin film constituting the facing portion is thinned. Therefore, the film forming load can be reduced, which can contribute to simplification of the manufacturing process and cost reduction.

The electrostatic actuator according to the present invention includes a fixed electrode formed in a recess on the substrate, and a movable electrode disposed opposite to the fixed electrode via a predetermined gap, and includes a fixed electrode and a movable electrode. In an electrostatic actuator that generates a displacement in the movable electrode by generating an electrostatic force therebetween, the fixed electrode is composed of a facing portion facing the movable electrode and other wiring portions, and the facing portion of the fixed electrode is A contact portion that contacts the movable electrode when the actuator is driven, and a circumferential wiring portion that is formed integrally with the wiring portion and surrounds the periphery of the contact portion. The contact portion is a conductive amorphous carbon thin film. The other part is composed of a film having higher conductivity than the conductive amorphous carbon-based thin film.
According to this configuration, the resistance of the fixed electrode as a whole can be further reduced as compared to the case where the opposing portion of the fixed electrode is formed of a conductive amorphous carbon-based thin film. Therefore, it is possible to further reduce the film thickness of the conductive amorphous carbon-based thin film, thereby further reducing the deposition load. Therefore, it is possible to contribute to further simplification and cost reduction of the manufacturing process.

  An amorphous carbon film can be used as the conductive amorphous carbon-based thin film.

In addition, the electrostatic actuator according to the present invention includes an insulating film provided on the surface of the movable electrode facing the fixed electrode, and an insulating amorphous carbon thin film provided on the surface of the insulating film.
According to this configuration, the surfaces of the movable electrode surface and the fixed electrode surface that are in contact with each other during driving are composed of a hard, low-friction coefficient amorphous carbon-based thin film. Since the true contact area is small and the material is the same, there is almost no contact charging, charging due to repeated driving due to repeated contact is suppressed, and there is less residual charge, enabling more stable driving.

  Further, as the insulating amorphous carbon-based thin film, an amorphous hydrogenated carbon or a tetrahedral amorphous carbon film can be used.

In addition, a method for manufacturing an electrostatic actuator according to the present invention includes a fixed electrode formed in a concave portion on a substrate, and a movable electrode disposed to face the fixed electrode with a predetermined gap therebetween. In a method for manufacturing an electrostatic actuator that generates a displacement in a movable electrode by generating an electrostatic force between the electrode and the electrode, a step of forming a conductive amorphous carbon-based thin film on the surface of the glass substrate on which the recess is formed; Of the conductive amorphous carbon thin film by etching away unnecessary portions to form a fixed electrode in the recess, forming an insulating film on the silicon substrate, and insulating the silicon substrate from the fixed electrode forming surface of the glass substrate The method includes a step of anodic bonding the film forming surface and a step of forming a movable electrode by etching the silicon substrate from the surface opposite to the bonding surface.
As a result, it is possible to manufacture a highly reliable actuator with excellent durability by improving the durability of driving by repeated contact and separation of the movable electrode. In addition, since the fixed electrode itself is composed of an amorphous carbon-based thin film, the manufacturing process is simplified compared to the conventional structure in which an amorphous carbon-based thin film is further formed on the fixed electrode for the purpose of improving driving durability. can do.

In addition, a method for manufacturing an electrostatic actuator according to the present invention includes a fixed electrode formed in a concave portion on a substrate, and a movable electrode disposed to face the fixed electrode with a predetermined gap therebetween. In a method for manufacturing an electrostatic actuator that generates a displacement in a movable electrode by generating an electrostatic force between the electrode and the electrode, a step of forming a conductive amorphous carbon-based thin film on the surface of the glass substrate on which the recess is formed; Of the conductive amorphous carbon-based thin film, unnecessary portions are etched away to form a fixed electrode in the recess, an insulating film is formed on the silicon substrate, and an insulating amorphous carbon-based thin film is formed on the surface of the insulating film. A step of forming, a step of etching and removing a portion of the insulating amorphous carbon-based thin film other than a portion that contacts the fixed electrode when the actuator is driven, and a glass substrate A step of the fixed electrode forming surface and the silicon substrate of the insulating film forming surface to anodic bonding, and a step of forming a movable electrode of the silicon substrate from the junction surface opposite to the surface by etching.
According to this manufacturing method, both the movable electrode surface and the fixed electrode surface that are in contact with each other during driving are composed of a hard, low-coefficient amorphous carbon-based thin film. Electrostatic actuators that can be driven more stably because the true contact area of the material is small and there is almost no contact charging due to the same type of material, and there is little residual charge by suppressing charging due to repeated driving due to repeated contact. Can be manufactured.

  The conductive amorphous carbon-based thin film can be formed by using ECR sputtering with graphite as a target.

  The insulating amorphous carbon-based thin film can be formed by vaporizing toluene and using RF-CVD.

The droplet discharge head according to the present invention has a nozzle substrate having a single or a plurality of nozzle holes for discharging droplets, and a recess serving as a discharge chamber communicating with each of the nozzle holes. Droplet discharge comprising a formed cavity substrate and an electrode substrate on which an individual electrode of a fixed electrode is formed so as to face a diaphragm of a movable electrode formed at the bottom of a discharge chamber with a predetermined gap. The head includes any one of the electrostatic actuators described above.
As described above, the droplet discharge head of the present invention is equipped with a highly reliable electrostatic actuator having high driving durability and excellent sustainability, so that the droplet discharge excellent in droplet discharge stability and sustainability is achieved. A head is obtained.

A droplet discharge apparatus according to the present invention includes the above-described droplet discharge head.
Since the droplet discharge device according to the present invention includes the above-described droplet discharge head, a droplet discharge device having excellent droplet discharge stability and sustainability can be obtained.

  Embodiments of a droplet discharge head including an electrostatic actuator to which the present invention is applied will be described below 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 the ink jet head according to the first embodiment, 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 an assembled state, FIG. 3 is an enlarged cross-sectional view of a portion A in FIG. 2, and FIG. 5 is a top view of the inkjet head of FIG. 1 and 2 are shown upside down from a state in which they are normally used.

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

  As shown in FIG. 2 to FIG. 4, the electrostatic actuator unit 4 provided for each nozzle hole 11 of the inkjet head 10 includes the 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 has a wiring part 5c composed of a lead part 5a and a terminal part 5a connected to a flexible wiring board (not shown). An insulating film 7 is formed on the surface of each diaphragm 6 facing the individual electrode 5, that is, the entire bonding surface of the cavity substrate 2 bonded to the electrode substrate 3.

Here, a silicon oxide film (SiO ₂ ) is used as the insulating film 7, but the present invention is not limited to this, and the following materials may be used. For example, when any one of aluminum oxide, silicon oxynitride, tantalum oxide, hafnium silicate, or hafnium oxynitride having a relative dielectric constant larger than that of silicon oxide (3.2) is used, silicon oxide Higher insulation resistance can be secured after securing the same electrostatic suction pressure by increasing the thickness. In other words, the required insulation resistance can be ensured by reducing the equivalent oxide thickness (EOT).

By the way, conventionally, in order to improve driving durability, a configuration in which an amorphous carbon-based thin film (DLC: diamond-like carbon) is provided on the individual electrode 5 has been proposed. In this example, the individual electrode itself is electrically conductive. It is formed by an amorphous carbon-based thin film having a property (hereinafter referred to as a conductive amorphous carbon-based thin film), which has one feature. Specifically, the conductive amorphous carbon-based thin film used as the individual electrode 5 is formed of an amorphous carbon film (a-C). In addition, the conductive amorphous carbon-based thin film used in this example has a resistivity as low as 5 × 10 ⁻² Ω · cm, for example, and the conductivity is reduced by reducing the resistivity. To function as. Since the amorphous carbon-based thin film has a high durability against the damage caused by repeated contact, adsorption holding, and detachment of the electrostatic actuator, the individual electrode 5 itself is made of an amorphous carbon-based thin film. By configuring, it is possible to configure a long-life electrostatic actuator that has a simple configuration but has improved driving durability and high durability and high reliability.

  Here, the amorphous carbon-based thin film is classified by the composition ratio sp2 / sp3, and when the composition of sp3 is large, the amorphous carbon-based thin film exhibits properties close to diamond, harder, and exhibits high resistivity and becomes insulating, while the composition of sp2 When there are many, it shows the property close to a graphite, and it becomes possible to suppress a resistivity low with a comparatively low stress. Therefore, in order to make the amorphous carbon-based thin film conductive, the amount of hydrogen in the film may be reduced so that the composition ratio sp2 / sp3 of sp2 and sp3 is 1 or more. In this example, an amorphous carbon (a-C) film is used as the sp2 rich film (low resistance). The composition ratio sp2 / sp3 of the amorphous carbon-based thin film is confirmed by a ratio in an evaluation method such as Raman scattering spectroscopy. That is, by comparing the sp2 cluster with the d-band peak and the sp3 cluster with the d-band shoulder by the intensity against the Raman shift, the ratio thereof is confirmed. A specific manufacturing method will be described in a fourth embodiment described later.

  Regarding the film thickness, the conductive amorphous carbon thin film is 200 nm, the silicon oxide film is 120 nm, and the distance of the gap G is 200 nm.

Here, the resistivity ρ of the conductive amorphous carbon thin film is set to 5 × 10 ⁻² Ω · cm in this example, and this point will be described below.
Assuming that the electrode thickness t, length l, and width b of the individual electrode of the electrostatic actuator, the resistance R of the individual electrode is expressed by the following equation (1).

  R = ρ · l / (b · t) (1)

  The time constant of the electrostatic actuator is τ = CR when the capacitance of the electrostatic actuator is C. Therefore, when this is substituted into the equation (1), the following equation (2) is obtained.

  τ = ρ · C · l / (b · t) (2)

  In order to ensure the responsiveness of a device such as an ink jet head as an electrostatic actuator and to quickly charge and discharge the actuator, there is an upper limit to the time constant τ of the electrostatic actuator, and when this is τmax, The following equation (3) holds.

  CR ≦ τmax (3)

  Substituting equation (1) into equation (3) gives the following equation (4).

  ρ ≦ τmax · b · t / (l · C) (4)

From equation (4), it can be seen that there is an upper limit to the resistivity of the conductive amorphous carbon-based thin film constituting the individual electrode 5, and that the resistivity needs to be low. In this example, the electrode thickness t = 20, the length l = 1 mm, the width b = 30 μm, the capacitance C = 10 pF, and the time constant τ ≦ 0.1 sec, so that ρ ≦ 6.0 × 10 ⁻² Ω. Calculated as cm. In this example, the individual electrode 5 is composed of a conductive amorphous carbon-based thin film of 5.0 × 10 ⁻² Ω · cm among 6.0 × 10 ⁻² Ω · cm or less.

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 composed of, for example, two-stage cylindrical nozzle holes having different diameters, that is, an ejection port portion 11a having a smaller diameter and an introduction port portion 11b having a larger diameter. It is configured. The injection port portion 11a and the introduction port portion 11b are provided perpendicular to and coaxially with respect to the substrate surface. The injection port portion 11a has a tip opening on the surface of the nozzle substrate 1, and the introduction port portion 11b is formed on the nozzle substrate 1. Are opened on the back surface (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 ink droplets, there is no scattering of ink droplets, and variations in the ejection amount of ink droplets can be suppressed. In addition, the nozzle density can be increased.

  The cavity substrate 2 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. Further, the diaphragm 6 is formed thin by the thickness of the boron diffusion layer formed by diffusing boron (B) from the surface of the silicon substrate to form a boron diffusion layer, stopping etching by wet etching. Further, the insulating film 7 is formed on the surface of the cavity substrate 2 facing the individual electrode 5 of the diaphragm 6 as described above.

  The recess 22 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. Further, a hole penetrating the electrode substrate 3 described later is provided in 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, for example. 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 is provided with a recess 32 at a surface position facing the diaphragm 6 of the cavity substrate 2. The recess 32 is formed at a required depth by etching. And in each recessed part 32, the individual electrode 5 which consists of an electroconductive amorphous carbon film is formed by thickness of 200 nm, for example. Therefore, the gap (gap) G formed between the diaphragm 6 and the individual electrode 5 is determined by the depth of the recess 32 and the thicknesses of the individual electrode 5 and the insulating film 7. Since the gap G greatly affects the ejection characteristics of the inkjet head, it is necessary to process the depth of the recess 32, the thickness of the individual electrode 5, and the thickness of the insulating film 7 with high accuracy.

The individual electrode 5 has a terminal portion 5a connected to a flexible wiring board (not shown). The terminal portion 5a is exposed in the electrode extraction portion 34 where the end portion of the cavity substrate 2 is opened.
The open end of the gap G formed between the diaphragm 6 and the individual electrode 5 is sealed with a sealing material 35 made of resin such as epoxy. Thereby, moisture and dust can be prevented from entering the gap between the electrodes, and the reliability of the inkjet head 10 can be kept high.

  The nozzle substrate 1, the cavity substrate 2 and the electrode substrate 3 are bonded together as shown in FIG. That is, the cavity substrate 2 and the electrode substrate 3 are bonded by anodic bonding, and the nozzle substrate 1 is bonded to the upper surface (the upper surface in FIG. 2) of the cavity substrate 2 by adhesion or the like.

Finally, as shown in FIGS. 2 and 5 in a simplified manner, a drive control circuit 40 such as a driver IC is connected to the terminal portion 5a of each individual electrode 5 and the common electrode 26 on the upper surface of the cavity substrate 2 with the flexible wiring board ( (Not shown).
Thus, the ink jet head 10 is completed.

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 to and attracted to the individual electrode 5 side to generate a negative pressure in the discharge chamber 21. Thus, the ink in the reservoir 23 is sucked to generate ink vibration (meniscus vibration). When the voltage 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 hole 11, and the ink droplet is ejected.

  When the ink jet head 10 is driven, the diaphragm 6 repeatedly contacts and separates from the individual electrode 5. At this time, stress or the like due to repeated contact acts on the individual electrode 5, but the amorphous carbon-based thin film constituting the individual electrode 5 is a hard film, so that the film is not broken and driving durability can be improved. It is. In addition, the amorphous carbon-based thin film has better adhesion to the glass substrate constituting the electrode substrate 3 than ITO (Indium Tin Oxide), which has been generally used as an individual electrode. It is possible to construct a high-quality electrostatic actuator free from defects and defects such as peeling.

As described above, in the electrostatic actuator unit 4 according to the first embodiment, the individual electrode 5 is composed of an amorphous carbon-based thin film that is a hard material having a small friction coefficient. It is possible to realize a highly reliable actuator with excellent sustainability by improving driving durability. In addition, since the individual electrode 5 itself is composed of an amorphous carbon-based thin film, it can be made simpler than the conventional structure in which an amorphous carbon-based thin film is further formed on the individual electrode for the purpose of improving driving durability. .
In addition, since the inkjet head 10 includes the electrostatic actuator unit 4 configured as described above, it is excellent in the stability and sustainability of droplet discharge, and can realize high-quality printing with a long life. Can be.

Embodiment 2. FIG.
FIG. 6 is a schematic cross-sectional view of the inkjet head 10 having the electrostatic actuator portion 4A of the second embodiment, and FIG. 7 is an enlarged cross-sectional view of a portion B in FIG. In the second and subsequent embodiments, the same reference numerals are given to portions corresponding to those in the first embodiment unless otherwise specified, and the description thereof is omitted.
The electrostatic actuator unit 4A according to the second embodiment is obtained by forming a surface layer 8 on the surface of the insulating film 7 formed on the diaphragm 6 in the electrostatic actuator unit according to the first embodiment. The same as in the first embodiment.

  The surface layer 8 is formed of an insulating high-resistance amorphous carbon-based thin film (hereinafter referred to as an insulating amorphous carbon-based thin film) with a thickness of about 10 nm, and is formed on a portion of the diaphragm 6 that is in contact with the individual electrode 5. Yes. The insulating amorphous carbon-based thin film differs from the conductive amorphous carbon-based thin film constituting the individual electrode 5 and is mainly composed of a SP3 rich or hydrogen rich film. A method for manufacturing the insulating amorphous carbon-based thin film will be described in a fourth embodiment described later. As the insulating amorphous carbon-based thin film, α-C: H (amorphous hydrogenated carbon) is used here. ta-C) may be used.

  As described above, the electrostatic actuator according to the second embodiment is composed of an amorphous carbon-based thin film that is hard and has a low friction coefficient, both of the surfaces of the diaphragm and the individual electrode surfaces that are in contact with each other when the actuator is driven. Real contact area at the time of contact (contact) is small, and since it is the same type of material, there is almost no contact charging, charging by repeated driving due to repeated contact is suppressed, residual charge is less, and more stable driving Is possible. In addition, there is no destruction due to wear. As a result, it is possible to realize an electrostatic actuator with higher driving stability and reliability than in the first embodiment, and to improve the durability of the inkjet head 10.

Embodiment 3 FIG.
In the third embodiment, the configuration of the individual electrode 5 is devised to reduce the film forming load when the individual electrode 5 is formed of a conductive amorphous carbon thin film. In the following, the individual electrode part, which is a characteristic part of the third embodiment, will be described with reference to the drawings, and the configuration and the like of the entire inkjet head 10 are the same as those of the first and second embodiments. To do.

  The time constant τ of the electrostatic actuator has an upper limit as described above, and it is desirable to reduce the resistance of the individual electrode 5 in order to secure a desired response. As a method of reducing the resistance of the individual electrode 5, there is a method of increasing the film thickness. However, if the film thickness is increased, the time required for film formation becomes longer in proportion to the film thickness, and thus the productivity is poor. Therefore, a large amount of material required for film formation is consumed, and there is a problem in terms of cost.

  Such a problem is sought to be solved by the configuration of the individual electrode 5, and the configuration of the individual electrode 5 will be described in order with two configuration examples.

(First configuration example)
FIG. 8 is a plan view of the individual electrode portion of the first configuration example of the electrostatic actuator according to the third embodiment. In FIG. 8, the arrows indicate the flow of charges, which will be described in the second configuration example below.
In the individual electrode 5 of the first configuration example, the actuator unit 50, which is the opposed part facing the diaphragm 6, is composed of a conductive amorphous carbon-based thin film, and the other wiring unit 5 c is general. In particular, it is used as a wiring and is composed of a conductive film (for example, Cr / Au film) having higher conductivity than the conductive amorphous carbon thin film.

  When the individual electrode 5 is configured as described above, the resistance of the entire individual electrode can be reduced as compared with the case where the entire individual electrode is formed of a conductive amorphous carbon-based thin film. Therefore, when the same responsiveness as that in the case where the entire individual electrode is composed of the conductive amorphous carbon-based thin film is to be secured with the configuration of FIG. 8, the actuator portion 50 of the individual electrode 5 is equivalent to the low resistance of the wiring portion 5c. Even if the resistance is high, it is acceptable. That is, the same function and performance (conductivity and responsiveness) can be ensured even if the conductive amorphous carbon-based thin film constituting the actuator unit 50 is thinned.

  As described above, according to the first configuration example of the third embodiment, it is possible to reduce the film forming load when manufacturing the individual electrode 5, and it is possible to contribute to simplification of the manufacturing process and cost reduction. It is. In addition, since the configuration is simple compared to the second configuration example described below, even if this configuration is applied to an actuator having a relatively narrow width and a small pitch, it is necessary to perform alignment with higher accuracy. In addition, the inkjet head can easily cope with problems such as high accuracy of the wiring formation process for miniaturization of wiring accompanying the increase in nozzle density.

(Second configuration example)
FIG. 9 is a plan view of the individual electrode portion of the second configuration example of the electrostatic actuator according to the third embodiment. 10 and 11 are cross-sectional views of the electrostatic actuator unit having the individual electrodes of FIG. 9, where FIG. 10 shows when the diaphragm is detached and FIG. 11 shows when the diaphragm is in contact.
The individual electrode 5 of the second configuration example divides the actuator unit 50 of the first configuration example into a contact portion 50a that contacts the diaphragm 6 and a circumferential wiring portion 50b that surrounds the periphery of the contact portion 50a. The contact portion 50a is made of a conductive amorphous carbon-based thin film, and the peripheral wiring portion 50b is made of a conductive film (for example, Cr / Au) integrally with the wiring portion 5c.

  In FIG. 9, the arrows indicate the flow of charges, and the charge supplied from the outside to the wiring part 50 c is supplied to the peripheral wiring part 50 b having a lower resistance than the contact part 50 a, and then the contact part. 50a is supplied toward the center in the width direction (vertical direction in the figure). Here, the flow of electric charge will also be described for the first configuration example. In the case of the first configuration example, the charge supplied from the outside to the wiring portion 5 c flows in the direction of the arrow through the actuator portion 50 of the individual electrode 5. . Since the resistance increases in proportion to the length in the direction in which the electric charge flows, in the first configuration example and the second configuration example, the portion composed of the conductive amorphous carbon-based thin film (that is, the entire actuator unit 50 and Comparing the resistance of the contact portion 50a), the second configuration example can be lowered. It should be noted that the resistance of the portions made of the conductive film (the wiring portion 50c and the circumferential wiring portion 50b) is much smaller than that of the conductive amorphous carbon-based thin film and can be ignored here.

  Therefore, in the configuration of the second configuration example, even when the conductive amorphous carbon-based thin film is formed thinner than the first configuration example, the same responsiveness as that of the first configuration example can be ensured. . That is, the film forming load can be further reduced. Therefore, it is possible to contribute to further simplification and cost reduction of the manufacturing process.

Embodiment 4 FIG.
Embodiment 4 outlines an example of a method for manufacturing the inkjet head 10 according to Embodiments 1 to 3 with reference to FIGS. 12 to 14. 12 is a flowchart showing a schematic flow of the manufacturing process of the inkjet head 10, FIG. 13 is a cross-sectional view showing an outline of the manufacturing process of the electrode substrate 3, and FIG. 14 is a cross-sectional view showing an outline of the manufacturing process of the inkjet head 10. .

In FIG. 12, steps S <b> 1 to S <b> 4 indicate the manufacturing process of the electrode substrate 3, and steps S <b> 5 to S <b> 9 indicate the manufacturing process of the silicon substrate that is the basis of the cavity substrate 2.
Here, a method for manufacturing the inkjet head 10 including the electrostatic actuator unit 4A according to the second embodiment will be mainly described.

The electrode substrate 3 is manufactured as follows.
First, a concave portion 32 having a desired depth is formed on a glass substrate 300 made of borosilicate glass or the like by etching with hydrofluoric acid using, for example, a gold / chromium etching mask (see FIG. 12). S1, FIG. 13 (a)). 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, a conductive amorphous carbon thin film 51 to be the individual electrode 5 is formed on the entire surface of the glass substrate 300 on which the recesses 32 are formed (S2 in FIG. 12, FIG. 13B).

  Table 1 shows the specifications of the amorphous carbon film (a-C) formed as the conductive amorphous carbon-based thin film 51 constituting the individual electrode 5 in this example and the film forming method, and Table 2 shows ECR plasma sputtering. The film forming conditions are shown.

As shown in Table 1, the amorphous carbon film (a-C) is formed with a thickness t = 200 nm by ECR (electron cyclotron resonance) plasma sputtering (solid source ECR film forming method) using graphite as a target. As the resistivity, ρ = 5 × 10 ⁻² (Ω · cm) or less is ensured to be a conductor. The film density is 2.3 g / cm ³ . Further, as shown in Table 2, the microwave power is 500 W, the target voltage is 500 V, the substrate bias is −40 V, and the irradiation ion acceleration voltage is 150 V.

  Here, since the ECR plasma sputtering method is used here as a method for forming the amorphous carbon film, the amorphous carbon film becomes a crystalline carbon film and can conduct electricity by π electrons. For this reason, it is possible to form a film that is hard and has low resistance and conductivity. As a result, it is possible to realize a low-resistance individual electrode 5 that can prevent damage due to repeated contact between the surface of the diaphragm and the individual electrode 5 when driving the electrostatic actuator, and can ensure sufficient responsiveness.

  The amorphous carbon film may be formed of amorphous carbon having a low hydrogen content by an arc discharge method in addition to the method of forming a film using graphite as a target by ECR sputtering as described above. Alternatively, the amorphous carbon-based thin film can be formed by CVD and then annealed at 300 ° C. to 500 ° C., for example.

Thereafter, a dry film resist is laminated on the formed conductive amorphous carbon-based thin film 51 to form a resist film, and the conductive amorphous carbon-based thin film 51 is patterned by leaving a portion to be the individual electrode 5. To remove and form compartments (S3 in FIG. 12). Next, the conductive amorphous carbon thin film 51 is oxidized and removed by oxygen plasma and etched. Thereafter, the resist is stripped with a resist stripping solution, and the conductive amorphous carbon-based thin film 51 is sectioned to form the individual electrodes 5 (S4 in FIG. 12, FIG. 13 (c)).
As described above, the electrode substrate 3 of the first embodiment and the second embodiment can be manufactured.

  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, for example, a boron diffusion layer 201 having a thickness of 0.8 μm is formed on the entire surface of one surface of the silicon substrate 200 having a thickness of 280 μm (S5 in FIG. 12).
Next, an insulating film 7 such as a silicon oxide film is formed on the entire surface (lower surface) of the boron diffusion layer 201 of the silicon substrate 200 (S6 in FIG. 12), and then an insulating amorphous carbon thin film is formed on the surface. 80 is formed as a surface layer (insulator surface layer) (S7 in FIG. 12, FIG. 14A).

  Table 3 shows the specifications of the amorphous hydrogenated carbon film (aC: H) formed as the insulating amorphous carbon thin film 80 in this example and the film forming method.

As shown in Table 3, the amorphous hydrogenated carbon film is formed in a thickness t = 10 (nm) by RF-CVD with toluene rich in hydrogen. The resistivity is ρ = 1 × 10 ¹⁵ (Ω · cm), and an insulator is used.

Thereafter, a dry film resist is laminated on the formed insulating amorphous carbon-based thin film 80 to form a resist film, and is patterned by leaving the contact portion of the diaphragm 6 of the insulating amorphous carbon-based thin film 80. Are removed and formed (S8 in FIG. 12, FIG. 14B). Next, the insulating amorphous carbon thin film 80 is oxidized and removed by oxygen plasma and etched. Thereafter, the resist is stripped with a resist stripping solution to partition and form the insulating amorphous carbon-based thin film 80 (S9 in FIG. 12, FIG. 14 (v)).
As described above, the silicon substrate 200 of the first to third embodiments can be manufactured.

Next, the silicon substrate 200 fabricated as described above is aligned (aligned) on the electrode substrate 3 and anodic bonded (S10 in FIG. 12, FIG. 14 (c)).
Next, the entire surface of the bonded silicon substrate 200 is polished by grinding / CMP to reduce the thickness to, for example, about 50 μm (S11 in FIG. 12, FIG. 14D). Thereafter, a silicon oxide film is formed on the polished silicon substrate surface by CVD.

  This silicon oxide film is photolithographically patterned to form an etching mask (S12 in FIG. 12), and anisotropic wet etching is performed with a KOH aqueous solution or the like to form ink channel grooves (S13 in FIG. 12). As a result, a recess 22 serving as the discharge chamber 21, a recess 24 serving as the reservoir 23, and a recess 27 serving as the electrode take-out portion 34 are formed, and a thin plate portion serving as the diaphragm 6 is formed by etch stop (FIG. 14 ( e)). 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 concave portion 27 is removed by dry etching or the like to open the electrode lead-out portion 34 (FIG. 14F).

  And the sealing material 35, such as an epoxy resin and an adhesive agent, is apply | coated to an open end part of a gap, and airtightly sealed. Further, the ink supply hole 33 is formed by penetrating the bottom of the recess 24 by microblasting or the like. Then, an ink protective film (not shown) is formed by CVD in the recess 22 that becomes the discharge chamber 21 of the silicon substrate 200. At this time, the electrode extraction unit 34 is masked to form a film. The gap opening end may be sealed together with the formation of the ink protective film (S14 in FIG. 12). Further, the common electrode 26 made of metal is formed on the silicon substrate 200 (FIG. 14G).

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 (S15 in FIG. 12, FIG. 14 (g)). Finally, by cutting into individual head chips by dicing, the above-described main body of the inkjet head 10 is completed (S16 in FIG. 12, FIG. 14 (h)).

According to the method for manufacturing the inkjet head 10, it is possible to manufacture an inkjet head including a highly reliable electrostatic actuator having high driving durability and excellent sustainability.
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.

  In the above embodiment, the electrostatic actuator, the inkjet head, and the manufacturing method thereof have been described. However, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the idea of the present invention. can do. For example, the electrostatic actuator of the present invention can be applied as a mirror device used in a projector or an actuator for a laser scan mirror used in a laser printer. Moreover, it is applicable as actuators, such as an optical switch and an optical filter used for a communication apparatus and an analysis apparatus. In addition, by applying the present invention, similar actions and effects can be obtained, a highly reliable actuator can be provided, and various types of information equipment with a long life can be realized.

  Also, by changing the liquid material discharged from the nozzle holes, in addition to inkjet printers, the production of color filters for liquid crystal displays, the formation of light emitting portions of organic EL display devices, the microarray of biomolecule solutions used for genetic testing, etc. It can be used as a droplet discharge device for various uses such as manufacture of

For example, FIG. 15 shows an outline of an ink jet printer including the ink jet head of the present invention.
The ink jet printer 500 includes a platen 502 that conveys the recording paper 501 in the sub-scanning direction Y, the ink jet head 10 (or 10A) having an ink nozzle surface facing the platen 502, and the ink jet head 10 (or 10A) has a carriage 503 for reciprocating in the main scanning direction X, and an ink tank 504 for supplying ink to each ink nozzle of the inkjet head 10.
Therefore, a high-resolution, high-speed ink jet printer can be realized.

FIG. 2 is an exploded perspective view illustrating a schematic configuration of the inkjet head according to the first embodiment. FIG. 3 is a cross-sectional view of an inkjet head having the electrostatic actuator unit 4 according to the first embodiment. The expanded sectional view of the A section of FIG. The aa expanded sectional view of FIG. FIG. 3 is a top view of the inkjet head of FIG. 2. FIG. 4 is a cross-sectional view of an inkjet head having an electrostatic actuator section 4A according to a second embodiment. The expanded sectional view of the B section of FIG. FIG. 6 is a plan view of an individual electrode 5 of a first configuration example according to Embodiment 3. FIG. 10 is a plan view of an individual electrode 5 of a second configuration example of the third embodiment. Sectional drawing of the electrostatic actuator part which has the individual electrode of FIG. 9 (at the time of diaphragm removal). Sectional drawing of the electrostatic actuator part which has the individual electrode of FIG. 9 (at the time of diaphragm contact). The flowchart which shows the outline flow of the manufacturing process of an inkjet head. Sectional drawing which shows the outline | summary of the manufacturing process of an electrode substrate. Sectional drawing which shows the outline | summary of the manufacturing process of an inkjet head. 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

  DESCRIPTION OF SYMBOLS 1 Nozzle board | substrate, 2 cavity board | substrate, 3 electrode board | substrate, 4,4A electrostatic actuator part, 5 individual electrode, 5c wiring part, 6 diaphragm, 7 insulating film, 8 surface layer, 10 inkjet head, 11 nozzle hole, 21 discharge Chamber, 26 Common electrode, 50 Actuator part (opposing part), 50a Contact part, 50b Circumferential wiring part, 50c Wiring part, 51 Conductive amorphous carbon-based thin film.

Claims (5)

A fixed electrode formed in a concave portion on the substrate, and a movable electrode disposed opposite to the fixed electrode with a predetermined gap, and generating an electrostatic force between the fixed electrode and the movable electrode In an electrostatic actuator that causes displacement in the movable electrode,
The fixed electrode includes a facing portion that faces the movable electrode and a wiring portion, and the facing portion of the fixed electrode is integrated with the contact portion that contacts the movable electrode when the actuator is driven, and the wiring portion. And is formed of a peripheral wiring portion surrounding the periphery of the contact portion, the contact portion is formed of a conductive amorphous carbon-based thin film, and the wiring portion and the peripheral wiring portion are An electrostatic actuator comprising a film having higher conductivity than the conductive amorphous carbon-based thin film. The electrostatic actuator according to claim 1, wherein the conductive amorphous carbon-based thin film is an amorphous carbon film. An insulating film on the opposing surface of the fixed electrode of the movable electrode is provided, the electrostatic according to claim 1 or 2, characterized in that is provided with an insulating amorphous carbon-based thin film on the surface of the insulating film Actuator. The electrostatic actuator according to claim 3, wherein the insulating amorphous carbon-based thin film is an amorphous hydrogenated carbon or a tetrahedral amorphous carbon film. An electrostatic actuator comprising a fixed electrode and a movable electrode disposed opposite to the fixed electrode via a gap, and generating an electrostatic force between the fixed electrode and the movable electrode to cause displacement of the movable electrode In
The fixed electrode includes a facing portion facing the movable electrode, and a wiring portion, and the facing portion is formed integrally with the first portion and the wiring portion, and surrounds the first portion. And a second part surrounding
The first part is composed of a conductive amorphous carbon-based thin film,
The electrostatic actuator, wherein the second part and the wiring part are formed of a film having higher conductivity than the conductive amorphous carbon thin film.

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