JP2007105860A - Electrode substrate, electrostatic actuator, droplet discharge head, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode substrate configured that an electrode formed in an indentation of a substrate has a high-precision staircase-like step part, and a manufacturing method thereof. <P>SOLUTION: In this electrode substrate 3, an electrode 31 is formed in an indentation 32 formed on a substrate. The electrode 31 is constituted of a plurality of laminates constituted by laminating electrode materials to have staircase-like step parts 31a, 31b, 31c, 31d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode substrate in which a stepped step portion is provided on an electrode, an electrostatic actuator using the electrode substrate, a droplet discharge head, and a manufacturing method thereof.

  As a droplet discharge head for discharging droplets, for example, an inkjet head mounted on an inkjet recording apparatus is known. Ink jet heads generally include a nozzle substrate in which a plurality of nozzle holes for ejecting ink droplets are formed, and ink such as a discharge chamber and a reservoir that are joined to the nozzle substrate and communicate with the nozzle holes. And a cavity substrate on which a flow path is formed, and is configured to eject ink droplets from selected nozzle holes by applying pressure to the ejection chamber by the driving unit. As a driving means, there are a method using an electrostatic force, a piezoelectric method using a piezoelectric element, a bubble jet (registered trademark) method using a heating element, and the like.

By the way, an electrostatic drive type inkjet head generally has a configuration in which a bottom portion of a discharge chamber is used as a vibration plate, and an individual electrode facing the vibration plate with a predetermined gap (gap) is formed on a glass substrate. ing. In order to ensure a predetermined gap length for the individual electrode to enable displacement of the diaphragm, an electrode material such as ITO (Indium Tin Oxide) is formed on the bottom surface of the recess formed on the surface of the glass substrate. It is formed by.
When ejecting ink droplets, a driving voltage is applied between the diaphragm and the individual electrodes, the diaphragm is elastically deformed by the electrostatic attractive force generated at this time, and the restoring force of the diaphragm when the driving voltage is turned off Thus, a part of the ink in the discharge chamber is discharged as an ink droplet from the nozzle hole.

In such an electrostatic drive type inkjet head, while high density is required, it is required to improve discharge power without causing an increase in drive voltage and to stably secure a necessary ink discharge amount. It has been. As one of the measures, the bottom of the concave portion of the glass substrate is formed in a multi-stepped shape, and a single layer of electrode material is formed thereon, thereby forming a stepped step portion on the individual electrode, thereby individually There has been proposed one in which the gap length between the electrode and the diaphragm is formed in a multi-step shape (see, for example, Patent Documents 1 and 2).
By forming the individual electrodes in a stepwise manner in this way, when the diaphragm is elastically deformed due to electrostatic attraction, it abuts along the stepped portion of the stepped individual electrode and sufficient elastic deformation is obtained. Even if the drive voltage is not increased (or even if the drive voltage is lowered), the discharge power can be improved, and a predetermined ink discharge amount can be secured.

JP-A-9-39235 JP 2000-318155 A

However, in the electrode substrate of the ink jet head disclosed in Patent Documents 1 and 2, a stepped step portion is formed by wet etching on the bottom surface of the recess provided in the glass substrate, and a single layer electrode material is formed thereon. Therefore, since the pattern is formed, there is a problem that variation in the step accuracy is large. That is, the step accuracy of the step portion provided on the individual electrode (fixed electrode member) depends on the step accuracy of the stepped step portion on the bottom surface of the recess. In addition, since the depth of the recess is adjusted by time management of wet etching, it is difficult to form a minute step on the bottom surface of the recess with high accuracy by wet etching. Therefore, the variation between substrates and the variation in a substrate become large. There are also individual differences.
On the other hand, dry etching has a relatively small variation, but takes a long time, and therefore has a great disadvantage in terms of productivity.

Therefore, an object of the present invention is to provide an electrode substrate configured so that an electrode formed in a recess of the substrate has a stepped step portion with high accuracy, and a manufacturing method thereof.
It is another object of the present invention to provide an electrostatic actuator and a droplet discharge head that can be driven at a low voltage by using such an electrode substrate, and a method for manufacturing the same.

  In order to solve the above-mentioned problems, an electrode substrate according to the present invention is an electrode substrate in which an electrode is formed in a recess formed in the substrate, and an electrode material is laminated so that the electrode has a stepped step portion. It consists of the laminated body of the multistage comprised by the above.

  The electrode substrate of the present invention is configured such that the electrode formed in the recess of the substrate has a stepped step portion by a multi-layered stack of electrode materials. Since the step accuracy can be obtained, a highly accurate step portion can be formed.

  In this case, the said recessed part is comprised by the single step so that it may have a fixed depth. That is, the bottom surface of the recess is a flat surface.

  The concave portion is formed by one etching. By forming the concave portion by one etching, the bottom surface of the concave portion can be formed flat even by wet etching.

  Further, it is preferable to use a borosilicate glass substrate as the substrate. By using the borosilicate glass substrate, it is possible to easily and firmly join the movable electrode member made of silicon when forming the electrostatic actuator by anodic bonding.

The electrostatic actuator according to the present invention is formed by joining an elastically deformable movable electrode member to any one of the electrode substrates described above so as to face the electrode via an insulating film and a gap.
In the electrode substrate of the present invention, since the electrode formed in the concave portion of the substrate has a stepped step portion with high accuracy as described above, when a voltage is applied between the electrode and the movable electrode member, both electrodes The movable electrode member is deformed and abutted along the stepped step portion of the electrode (fixed electrode member) due to the electrostatic attractive force generated between the two electrodes (this contact state is referred to as “coupled contact”). ). Therefore, the electrostatic actuator of the present invention can increase the displacement of the movable electrode member even with a low driving voltage.

Further, it is preferable that the step portions of the plurality of steps of the electrode are formed substantially symmetrically so that the gap length at the center portion is the largest and the gap lengths at both end portions are the smallest.
As a result, the movable electrode member can be displaced in a concave curve, which is suitable when the electrostatic actuator of the present invention is used for a droplet discharge head.

A droplet discharge head according to the present invention includes a discharge chamber provided in a flow path communicating with a nozzle hole, an elastically deformable movable electrode member constituting a bottom wall of the discharge chamber, and an insulating film on the movable electrode member And an electrostatically driven droplet discharge head comprising: a fixed electrode member disposed oppositely through a gap; and a driving means for generating an electrostatic force between the movable electrode member and the fixed electrode member. The fixed electrode member is composed of any one of the electrode substrates described above.
With this configuration, the droplet discharge head according to the present invention can be driven at a low voltage and can increase displacement by the coupled contact of the movable electrode member, thereby improving the discharge power. It is possible to always secure a stable discharge amount.

The electrode substrate manufacturing method according to the present invention includes a step of forming a recess having a certain depth on a substrate by etching, and forming an electrode material on the surface of the substrate including the recess, and then forming the film A step of patterning and etching the electrode material a plurality of times to form a stacked body of electrode films having stepped step portions in the recesses.
According to the electrode substrate manufacturing method of the present invention, the electrode material film formation and patterning are repeated by the required number of steps, so that the electrode in the recess of the substrate (consisting of a laminate of electrode films) has a highly accurate stepped step. The part can be formed.

  Further, the stepped step portion is formed on the final electrode film. As a result, the electrode film at the final stage is a series of stepped step portions, so that there is less risk of peeling.

The method for manufacturing an electrode substrate according to the present invention includes a step of forming a recess having a certain depth on the substrate by etching, and depositing an electrode material on the surface of the substrate including the recess using a mask. Steps for forming a laminated body of electrode films having stepped step portions by repeating the mask film formation a plurality of times, and finally patterning and etching the laminated body of the electrode films so that electrodes other than necessary portions are formed. And a step of removing the film portion.
According to the method for manufacturing an electrode substrate of the present invention, a high-precision staircase is formed on an electrode (consisting of a laminate of electrode films) in a concave portion of the substrate by repeating mask film formation of an electrode material using a mask by the required number of steps. A stepped portion having a shape can be formed. Further, since the patterning of the electrode film stack may be performed only once, the manufacturing process becomes simple.

Moreover, it is preferable that the stepped step portions are formed substantially symmetrically so that the center portion is the lowest and the both end portions are the highest.
As a result, the movable electrode member can be displaced in a concave curve, which is suitable when the electrostatic actuator of the present invention is used for a droplet discharge head.

An electrostatic actuator manufacturing method according to the present invention includes an electrode substrate manufactured by any one of the manufacturing methods described above, an elastically deformable movable electrode member facing an electrode film laminate, and an insulating film and a gap. It joins via.
Thereby, an electrostatic actuator that can be driven at a low voltage is obtained.

A method for manufacturing a droplet discharge head according to the present invention includes a step of bonding a silicon substrate to an electrode substrate manufactured by any one of the manufacturing methods described above, and then processing the silicon substrate into a thin plate;
Forming a recess that becomes a discharge chamber by etching on a silicon substrate processed into a thin plate.
As a result, a cavity substrate made of a silicon substrate having a recess serving as a discharge chamber can be formed in a state of being bonded to the electrode substrate of the present invention, so that the cavity substrate can be easily handled and the substrate can be increased in diameter. It becomes possible. Therefore, the manufacturing cost of the droplet discharge head can be reduced.

  Hereinafter, embodiments to which the present invention is applied will be described with reference to the drawings.

Embodiment 1. FIG.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an electrostatic actuator including an electrode substrate according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA in FIG.
The electrode substrate 3 of the present embodiment has a plurality of steps formed by laminating electrode materials so that a recess 32 is formed in a glass substrate, and stepped step portions 31a, 31b, 31c, 31d are formed in the recess 32. An electrode (fixed electrode member) 31 made of a laminated body (for example, four stages) is formed.
The depth of the recess 32 is, for example, 0.3 μm, and is formed by one etching so as to have a certain depth. Thus, since the recessed part 32 is a single step structure, the bottom face of the recessed part 32 can be accurately and evenly formed by wet etching.

In general, ITO (Indium Tin Oxide) is used as the electrode material, but the electrode material is not particularly limited to this, and for example, IZO (Indium Zinc Oxide) can also be used. Moreover, there is no limitation in particular also about the film thickness of the electrode material of each step | level. However, the total thickness of the entire laminate is set to be slightly smaller than the depth of the recess 32. Here, for example, each stage from the first stage (lowermost stage) to the third stage has a film thickness of 200 angstroms, and the uppermost stage (fourth stage) has a film thickness of 1800 angstroms.
By sputtering the electrode material as described above, it is possible to form the electrode 31 composed of a multi-layered structure having stepped step portions 31a, 31b, 31c, 31d in the recess 32 with high accuracy. The method for manufacturing the electrode substrate 3 will be described in detail later.
The substrate material of the electrode substrate 3 is not particularly limited, but borosilicate glass is suitable. Of course, other substrate materials can be used, and silicon or resin may be used.

  By bonding the movable electrode member 22 that can be elastically deformed to the surface of the electrode substrate 3 via the insulating film 26, the electrostatic actuator 5 as shown in FIGS. 1 and 2 can be configured. Here, the movable electrode member 22 is made of an extremely thin flat plate made of silicon. The plate thickness is, for example, about 1 μm. Further, the step portions 31a, 31b, 31c, 31d of the electrode (fixed electrode member) 31 made of the laminated body have, for example, the largest gap length G1 at the central portion and the smallest gap length G4 at both end portions. It is formed almost symmetrically. That is, G1> G2> G3> G4 and the gap length is formed so as to be sequentially reduced from the lowest level (first level). The gap length Gi (here, i = 1 to 4) is a distance between the lower surface of the insulating film 26 and the surface of the i-th electrode film. And the electrostatic actuator 5 is comprised by connecting a voltage application apparatus as the drive means 4 between the electrode 31 and the movable electrode member 22. FIG.

  This electrostatic actuator 5 can be applied to, for example, a drive unit of an inkjet head. In the case of an ink jet head, the movable electrode member 22 is generally referred to as a “vibrating plate” and the electrode (fixed electrode member) 31 is generally referred to as an “individual electrode”. Therefore, these names may be used in the following description.

  In the electrostatic actuator 5, the movable electrode member 22 corresponding to the uppermost (fourth) gap length G <b> 4 is placed between the electrode 31 and the movable electrode member 22 arranged to face each other by the driving unit 4. When a voltage necessary and sufficient to contact 31 is applied, the movable electrode member 22 contacts and is held by the fourth step portion 31d having the smallest gap length. At this time, the gap length temporarily becomes (G3-G4) at the boundary corresponding to the fourth and third gap lengths G4 and G3, so that a large electrostatic attraction force is applied to the movable electrode member 22. In order to act, the movable electrode member 22 corresponding to the next gap length G3 also comes into contact with the third stepped portion 31c of the electrode 31 at the same voltage. In this way, the forward feed action is continuously induced up to the portion corresponding to the first stage (lowermost stage) G1 having the largest gap length, so that eventually the movable electrode of the part corresponding to the uppermost gap length G4 is obtained. The entire movable electrode member 22 bends as indicated by the dotted line in FIG. 1 at a voltage sufficient to cause the member 22 to contact the electrode 31, and can contact the electrode 31. Hereinafter, the manner or contact state in which the movable electrode member 22 abuts along each step of the electrode 31 as described above will be referred to as “coupled abutment”. The movable electrode member 22 does not necessarily have to be in contact with all the step portions of the electrode 31. For example, the movable electrode member 22 may not come into contact with the lowermost step portion 31a, but such a state is also included in the concept of “coupled contact”.

  Therefore, the electrostatic actuator 5 of the present embodiment can increase the displacement of the movable electrode member 22 without increasing the driving voltage or even with a low driving voltage. Therefore, when this electrostatic actuator 5 is used in an ink jet head as will be described later, it can be driven at a low voltage, and the displacement of the movable electrode member 22 can be increased by the coupled contact. A discharge power can be obtained, and a stable ink discharge amount can be secured.

  Note that the stepped step portions 31a, 31b, 31c, and 31d of the electrode 31 are formed substantially symmetrically in the longitudinal direction of the electrode 31 in the example shown in FIG. You can also Moreover, when using this electrostatic actuator 5 for the diaphragm part of a micropump, it is preferable to form the level | step-difference parts 31a, 31b, 31c, 31d in the shape of a step-like concentric circle. In addition, the movable electrode member 22 is an example in which the entire peripheral edge in a plan view is fixed, but is not limited thereto, and can be configured as both-end supported or cantilevered. In the case of a cantilever, the step portions 31a, 31b, 31c, and 31d are formed in a step shape that is inclined on one side.

Embodiment 2. FIG.
In the present embodiment, a configuration example of an inkjet head will be described with reference to FIGS. 3 to 5 as an example of a droplet discharge head configured using the electrostatic actuator 5 described above. This ink jet head is a face discharge type that discharges ink droplets from nozzle holes provided on the surface of a nozzle substrate. However, the present invention is not limited to the shape and structure shown in the figure, and the end of the substrate is not limited. The present invention can also be applied to an edge discharge type inkjet head that discharges ink droplets from nozzle holes provided in the section.
FIG. 3 is an exploded perspective view showing an exploded schematic configuration of the ink jet head according to the present embodiment, and a part thereof is shown in cross section. FIG. 4 is a cross-sectional view of the ink jet head showing the schematic configuration of the right half of FIG. 3, and the deformation state of the diaphragm is schematically represented by a dotted line. FIG. 5 is a top view of the inkjet head of FIG. 3 and 4 are shown upside down from the normally used state.

  As shown in FIGS. 3 and 4, the inkjet head (an example of a droplet discharge head) 10 according to this 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. Contrary to the cavity substrate 2 provided with the ink supply path independently and the diaphragm 22 of the cavity substrate 2, the concave portion has a stepped gap length Gi (here, i = 1 to 3). The electrode substrate 3 having the individual electrodes 31 formed by laminating a plurality of electrode materials in the layer 32 is bonded together.

  Here, the electrostatic actuator 5 of the present embodiment includes a diaphragm 22 provided independently on the cavity substrate 2, and a plurality of stages formed in the recess 32 of the electrode substrate 3 so as to face the diaphragm 22. (In this case, three steps) The step portions 31a, 31b, and 31c are provided independently from each other and the individual electrode 31 made of a laminate of electrode materials. An insulating film 26 is formed on the lower surface of the diaphragm 22, that is, the surface bonded to the electrode substrate 3 to prevent dielectric breakdown and short circuit. In addition, a drive control circuit composed of a driver IC or the like is provided between the diaphragm 22 and the individual electrode 31 as the drive unit 4 that applies a drive voltage to generate an electrostatic force. The drive control circuit is mounted on a flexible wiring board (not shown), and the flexible wiring board is connected to the terminal portion 31C of each individual electrode 31 and the common electrode 28 provided on the cavity substrate 2. When a drive voltage is applied between the diaphragm 22 and the individual electrode 31 by the drive control circuit to generate an electrostatic force, the diaphragm 22 can be deformed as shown by a dotted line in FIG.

Hereinafter, the configuration of each substrate will be described in detail.
The nozzle substrate 1 is made of, for example, a silicon single crystal substrate (hereinafter also simply referred to as a silicon substrate) having a thickness of 180 μm. In the nozzle substrate 1, a recess 12 is formed in a region where a plurality of nozzle holes 11 are provided, and a nozzle hole 11 for ejecting ink droplets is opened on the bottom surface of the recess 12. That is, the flow path resistance of each nozzle hole 11 is adjusted by thinning the length of the nozzle portion (substrate thickness) by the recess 12. This ensures uniform ejection performance and prevents other objects such as recording paper from coming into direct contact with the ejection surface (bottom surface of the recess 12), so that the recording paper is soiled or the tip of the nozzle hole 11 is damaged. Can be prevented.

  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).

  As described above, the nozzle hole 11 is configured in two stages from the ejection port portion 11a and the inlet port portion 11b having a larger diameter, thereby aligning the ink droplet ejection direction with the central axis direction of the nozzle hole 11. And stable ink ejection 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.

  Further, in FIG. 4 of the nozzle substrate 1, an orifice (narrow groove) 13 that forms a part of the ink flow path is provided on the lower surface (the surface on the bonding side with the cavity substrate 2). Further, a diaphragm portion 14 that is thinned by a concave portion is provided at a position corresponding to a reservoir 23 of the cavity substrate 2 described later. The diaphragm portion 14 is provided to suppress pressure fluctuation in the reservoir 23.

  The cavity substrate 2 is made of, for example, a (110) plane silicon single crystal substrate having a thickness of about 140 μm (hereinafter, this substrate is also simply referred to as a silicon substrate). This silicon substrate has a boron-doped layer having the same thickness as that of the diaphragm 22 and is subjected to anisotropic wet etching on the silicon substrate to thereby form the recesses 24 and 25 for constituting the discharge chamber 21 and the reservoir 23 of the ink flow path. Is formed with high accuracy. A plurality of recesses 24 are independently formed at positions corresponding to the nozzle holes 11. Therefore, as shown in FIG. 4, when the nozzle substrate 1 and the cavity substrate 2 are joined, each concave portion 24 constitutes a discharge chamber 21, communicates with the nozzle hole 11, and serves as the ink supply port. Both communicate with each other. And the diaphragm 11 with high thickness precision is comprised by the thickness of the boron dope layer which comprises the bottom wall of the discharge chamber 21 (recessed part 24).

  The other recess 25 is for storing liquid material ink, and constitutes a common reservoir (common ink chamber) 23 for each discharge chamber 21. The reservoirs 23 (recesses 25) communicate with all the discharge chambers 21 through the orifices 13, 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 an ink supply port 35 of the hole.

Further, an insulating film 26 made of, for example, a SiO ₂ film or a TEOS film is formed to a thickness of 0.1 μm by plasma CVD (Chemical Vapor Deposition) on at least the lower surface of the cavity substrate 2, that is, the surface facing the electrode substrate 3. Yes.
On the upper surface of the cavity substrate 2, that is, the surface facing the nozzle substrate 1 (including the inner surface of the discharge chamber 21 and the reservoir 23), an SiO ₂ film (including a TEOS film) serving as an ink protection film (not shown) is formed by plasma CVD or sputtering. Is formed. This ink protective film is provided to prevent corrosion of the flow path by ink.

The electrode substrate 3 is made of, for example, a glass substrate having a thickness of 1 mm. As shown in FIGS. 3 and 4, the electrode substrate 3 is provided with a recess 32 having a certain depth at the position of the surface of the cavity substrate 2 facing each diaphragm 22. The depth of the recess 32 is, for example, 0.3 μm.
In this recess 32, for example, an individual electrode 31 having stepped step portions 31a, 31b, and 31c is formed by stacking a plurality of electrode films made of ITO (Indium Tin Oxide) by sputtering. Therefore, the individual electrode 31 has a stepped gap length G1, G2, G3 (where G1>G2> G3) between the electrode substrate 3 and the cavity substrate 2 when the electrode substrate 3 and the cavity substrate 2 are joined. ing. The gap length Gi is formed substantially symmetrically in the longitudinal direction of the individual electrode 31 so that the center portion is the largest and the both end portions are the smallest. The gap length Gi is the distance between the surface (lower surface) of the insulating film 26 formed on the lower surface of the diaphragm 22 and the surface of the i-th electrode film.

The individual electrode 31 includes an electrode part 31A, a lead part 31B, and a terminal part 31C. A communication groove 33 is formed in the recess 32 to pull out the lead portion 31B. In FIG. 4, the recess 32 and the communication groove 33 are formed with the same depth, but of course the depth may be different. For example, the depth of the communication groove 33 may be formed shallower than the recess 32. That is, the lead part 31B and the terminal part 31C may have a single layer or a laminated structure having a smaller number than the electrode part 31A. Further, it is preferable that the electrode pad is formed so that the terminal portion 31C substantially coincides with the surface of the electrode substrate 3 or is slightly discharged from the surface of the substrate.
Therefore, the above-described constant depth of the concave portion 32 means that at least the concave portion 32 in a range where the electrode portion 31A corresponding to the diaphragm 22 is formed has a constant depth. However, from the viewpoint of processing of the electrode substrate 3, it is preferable to form the recess 32 and the communication groove 33 by the same etching at the same depth.

  A flexible wiring board (not shown) is connected to the terminal portion 31 </ b> C of the individual electrode 31. As shown in FIGS. 3 to 5, these terminal portions 31 </ b> C are exposed in an electrode extraction portion 29 in which the end portion of the cavity substrate 2 is opened for wiring.

  As described above, the nozzle substrate 1, the cavity substrate 2, and the electrode substrate 3 are bonded to each other as shown in FIG. Furthermore, the open end portion of the interelectrode gap formed between the diaphragm 22 and the individual electrode 31 is sealed with a sealing material 37 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.

Finally, as shown in a simplified manner in FIGS. 4 and 5, a drive control circuit such as a driver IC is provided as the drive means 4 with the terminal portions 31 </ b> C of the individual electrodes 31 and the common electrode 28 provided on the cavity substrate 2. To 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.
The drive control circuit is an oscillation circuit that controls supply and stop of electric charges to the individual electrode 7. This oscillation circuit oscillates at, for example, 24 kHz, and supplies electric charges by applying pulse potentials of, for example, 0 V and 30 V to the individual electrodes 31. When the oscillation circuit is driven and charges are supplied to the individual electrode 31 to be positively charged, the diaphragm 22 is negatively charged and an electrostatic force (Coulomb force) is generated between the individual electrode 31 and the diaphragm 22. Therefore, the diaphragm 22 is attracted to the individual electrode 31 by this electrostatic force and bends (displaces). At this time, as described above, the individual electrode 31 is provided with a plurality of step portions 31a, 31b, 31c so that the central portion in the longitudinal direction is the lowest, so that the gap length Gi is a step toward the central portion. Therefore, the diaphragm 22 is displaced from the uppermost step portion 31 c by forward feeding and is in continuous contact with the individual electrode 31. As a result, the volume of the discharge chamber 21 increases. When the supply of electric charges to the individual electrode 31 is stopped, the diaphragm 22 returns to its original state due to its elastic force, and at this time, the volume of the discharge chamber 21 decreases rapidly. Part of the ink is ejected from the nozzle hole 4 as ink droplets. Next, when the vibration plate 22 is similarly displaced, ink is supplied from the reservoir 23 to the discharge chamber 21 through the orifice 13.

  Thus, in the inkjet head 10 of this embodiment, the individual electrodes 31 in the recesses 32 of the electrode substrate 3 have stepped step portions 31a, 31b, 31c made of a laminate of electrode materials and a stepped gap length G1. , G2 and G3, the elastic deformation of the diaphragm 22 during driving is deformed and contacted along the step portion of the individual electrode 31 (coupled contact) as shown by the dotted line in FIG. Therefore, the increase in the volume of the discharge chamber 21 is increased, and as a result, the discharge power can be improved and the necessary ink discharge amount can be stably secured without increasing the drive voltage. In other words, a required amount of ink droplets can always be stably ejected even with a low driving voltage.

  Next, the 1st example of the manufacturing method of the electrode substrate of this invention is demonstrated with reference to the process drawing of FIG. 6 and FIG. Here, for example, a method for manufacturing the electrode substrate 3 including the individual electrodes 31 having four step portions for the inkjet head 10 will be described. 6 and 7, the inkjet head 10 shown in FIG. 3 is symmetrical, and therefore, for the sake of convenience, the right half of the cross section is shown. However, in practice, the left portion is simultaneously formed. Further, the thickness of the substrate and the etching depth in the following description are merely examples, and do not limit the present invention.

First, as shown in FIG. 6A, a borosilicate glass substrate 300 processed to a predetermined thickness, for example, 1 mm, is prepared as a substrate to be processed, and on the surface of the glass substrate 300, For example, an etching mask 301 made of chromium (Cr) is formed by sputtering.
Next, a resist 302 is applied to the entire surface of the etching mask 301 (FIG. 6B).

  Next, by patterning the resist 302 by photolithography and etching the etching mask 301, an opening 303 having a shape corresponding to the recess 32 is formed in the etching mask 301 (FIG. 6C).

  Next, for example, the glass substrate 300 is etched by a predetermined amount with a hydrofluoric acid aqueous solution at a time, thereby forming a groove-like recess 32 having a certain depth (for example, a depth of 0.3 μm) (FIG. 6 ( d)). Then, after removing the resist 302 with an organic stripper or the like, the glass substrate 300 is immersed in a chrome etchant to remove the etching mask 301 (FIG. 6E).

Next, a first layer electrode film 311 made of ITO as an electrode material is formed by sputtering on the entire surface of the glass substrate 300 on which the recesses 32 are formed (FIG. 7F).
Next, a resist 304 is applied to the surface of the first-layer electrode film 311 and the resist 304 is patterned by photolithography (FIG. 7G). Next, the first-layer electrode film 311 a having a stepped portion is formed in the recess 32 by etching the first-layer electrode film 311. Thereafter, the resist 304 is stripped with an organic stripper or the like (FIG. 7 (h)).

  Next, the steps from (f) to (h) in FIG. 7 are repeated as many times as necessary to form a laminate of electrode films up to the final stage (uppermost stage). For example, when the second-stage electrode film 312a having a stepped portion is formed, a second-layer electrode film 312 made of the same ITO is formed on the first-stage electrode film 311a as shown in FIG. A film having a desired thickness is formed by sputtering. As a result, the second-layer electrode film 312 is laminated on the first-stage electrode film 311a to form a stepped step portion. Then, a resist 304 is applied to the surface of the second-layer electrode film 312 in the same manner as in FIG. 7G, the resist 304 is patterned by photolithography, and the second-layer electrode film 312 is etched. A second-stage electrode film 312a having a stepped portion can be formed. Thereafter, the resist 304 is peeled off. Thereafter, the third and subsequent electrode films 313a and later can be formed in the same manner as described above.

When the uppermost (fourth) electrode film 314a is laminated in this manner, the uppermost electrode film 314a is formed as a stack of four electrode films as shown in FIG. 7 (j). Since it is formed in an attached shape, the individual electrode 31 having a plurality of stepped step portions 31 a to 31 d can be formed in the concave portion 32 of the glass substrate 300 by the laminated body of the electrode films.
Thus, the electrode substrate 3 for the ink jet head 10 is manufactured. Although a pad portion is finally formed on the terminal portion of the individual electrode 31 by sputtering, the illustration is omitted.
The electrostatic actuator shown in FIG. 4 is manufactured by anodic bonding to the electrode substrate 3 with the diaphragm 22 facing the individual electrode 31 through the insulating film 26.

  According to the method for manufacturing the electrode substrate 3 of the present embodiment, the electrode film 3 and the patterning are repeated by the required number of steps, whereby the individual electrode 31 made of a laminate of electrode films and having stepped step portions is recessed. 32 can be formed. Moreover, in order to increase the step accuracy in electrode film formation, a step portion is formed on the bottom surface of the recess by wet etching, and a step portion with higher accuracy is formed compared to the conventional method in which a single layer electrode film is formed thereon. Can be formed. Further, since the electrode film 314a at the final stage is formed with the stepped step portions 31a to 31d continuously, there is little risk of peeling.

  Next, FIG. 8 and FIG. 9 show a second example of the manufacturing method of the electrode substrate 3 of the present invention. FIGS. 10A to 10C are top views showing the state of mask film formation used in this manufacturing method, and FIG. 11 shows a state after removing unnecessary portions of the electrode film formed in a laminated form. 3 is a top view of an individual electrode 31. FIG. 10A to 10C and FIG. 11 show a part of the recesses 32 and the individual electrodes 31 in the left and right two-row groups formed on the glass substrate. 8 and 9 are cross-sectional views of the right part thereof.

  8 (a) to 9 (f) are the same as the steps shown in FIGS. 6 (a) to 7 (f). Therefore, the same reference numerals are given to the respective parts, and description thereof is omitted. . A top view corresponding to FIG. 9F is as shown in FIG.

In FIG. 9G, a second silicon layer 305 is formed on the first electrode film 311 using the first silicon mask 305 masking the first step 31a. An electrode film 312 is formed. The top view at this time is as shown in FIG. The second-layer electrode film 312 is laminated in a direction orthogonal to the respective recesses 32. The same applies to the third and subsequent stages. Note that the first-layer electrode film 311 may be similarly formed using a silicon mask.
Next, as shown in FIG. 9H, the third stepped portion 31 c is formed on the second-layer electrode film 312 using the second silicon mask 306 masking the second stepped portion 31 b. A third-layer electrode film 313 is formed.
Further, as shown in FIG. 9 (i), the last step portion of the fourth step is formed on the third-layer electrode film 313 using a third silicon mask 307 in which the step portion 31c of the third step is masked. A fourth-layer electrode film 314 to be 31d is formed. The top view at this time is as shown in FIG.
In this manner, the mask film formation using the mask is repeated as many times as necessary to form a stacked body of electrode films having stepped step portions.

Finally, as shown in FIGS. 9 (j) and 11, a resist (not shown) is applied to the laminate of the electrode films, and the resist is patterned and etched by photolithography to eliminate the need for the electrode films. A portion (a portion other than the electrode film in the recess 32) is removed.
As described above, the electrode substrate 3 for the ink jet head 10 which is made of the laminated body of the electrode films as shown in FIG. 4 and has the individual electrodes 31 having the stepped step portions formed in the recesses 32 can be manufactured. it can.

  According to the method for manufacturing the electrode substrate 3 of the present embodiment, the individual electrode 31 formed of a laminate of electrode films having stepped step portions is placed in the recess 32 by repeating mask film formation using a mask a required number of times. Can be formed. Therefore, also in this manufacturing method, a highly accurate step part can be formed by mask film formation for the required number of steps. Moreover, since the patterning with respect to the laminated body of electrode films may be performed only once, the manufacturing process can be simplified.

  Next, an example of a method for manufacturing the inkjet head 10 of the present invention will be described with reference to FIGS. Here, the electrode substrate 3 manufactured by the method shown in FIGS. 9 to 11 is used, but the electrode substrate 3 by the method of FIGS. 6 and 7 may be used.

First, as shown in FIG. 12A, a silicon substrate 200 having a thickness of 525 μm, for example, is prepared by polishing both sides of a (110) plane silicon substrate having a boron doped layer 201. A TEOS film 202 to be the insulating film 26 is formed on the entire lower surface of the boron doped layer 201 to a thickness of 0.1 μm, for example, by plasma CVD. The TEOS film 202 is formed, for example, at a temperature of 360 ° C., a high frequency output of 250 W, a pressure of 66.7 Pa (0.5 Torr), a gas flow rate of TEOS flow rate of 100 cm ³ / min (100 sccm), and an oxygen flow rate of 1000 cm ³ / min (1000 sccm). Perform under the conditions of The insulating film 26 may be SiO ₂ .

Next, the electrode substrate 3 fabricated as shown in FIG. 9J and the silicon substrate 200 are anodic bonded through the TEOS film 202 (FIG. 12B). The electrode substrate 3 is processed with a drill or the like so as not to penetrate the hole 35a serving as the ink supply port 35 before bonding. This is because if the hole 35a is penetrated, the etching solution enters the gap between the electrodes in the subsequent manufacturing process, and the malfunction of the diaphragm 22 occurs.
In anodic bonding, the electrode substrate 3 and the silicon substrate 200 are heated to 360 ° C., a negative electrode is connected to the electrode substrate 3, and an anode is connected to the silicon substrate 200, and a voltage of 800 V is applied and bonded.

  Next, after the anodic bonding, the surface of the silicon substrate 200 is ground until the thickness of the silicon substrate 200 becomes about 150 μm (FIG. 12C). Thereafter, in order to remove the work-affected layer, the silicon substrate 200 is etched by about 10 μm with a potassium hydroxide solution having a concentration of 32 wt%. As a result, the thickness of the silicon substrate 200 becomes about 140 μm.

Next, a TEOS etching mask 203 with a thickness of 0.5 μm is formed on the entire etching surface of the silicon substrate 200 by using plasma CVD (FIG. 12D). The TEOS etching mask 203 is formed, for example, at a temperature of 360 ° C., a high frequency output of 700 W, a pressure of 33.3 Pa (0.25 Torr), a gas flow rate of TEOS flow rate of 100 cm ³ / min (100 sccm), and an oxygen flow rate of 1000 cm ³ / min ( 1000 sccm).

  Next, resist patterning is performed in order to etch the TEOS etching mask 203 of the portion 21a serving as a discharge chamber, the portion 23a serving as a reservoir, and the portion 29a serving as an electrode extraction portion (FIG. 12E). After patterning the TEOS etching mask 203, the resist is removed. Here, depending on the case, in order to make the depth of each part 21a, 23a, 29a different, the etching depth of the corresponding TEOS etching mask 203 may be made different.

Next, by etching a bonded substrate (referred to as a substrate after bonding of the silicon substrate 200 and the electrode substrate 3) with a potassium hydroxide aqueous solution, a recess 24 serving as a discharge chamber 21 is formed in the thinned silicon substrate 200. Then, a concave portion 25 to be the reservoir 23 and a concave portion 29b to be the electrode extraction portion 29 are formed (FIG. 12F). In this etching process, first, etching is performed using a potassium hydroxide aqueous solution having a concentration of 35 wt% until the remaining thickness of the silicon substrate 200 becomes, for example, 5 μm, and then switching to a potassium hydroxide aqueous solution having a concentration of 3 wt%. Etching is performed. As a result, when the surface of the boron doped layer 201 appears, the etching rate is extremely reduced and the etching stop sufficiently works, so that the surface of the diaphragm 22 is prevented from being rough and the thickness thereof is 0.80 ± 0.05 μm. And can be formed to a highly accurate thickness.
Then, after the etching is completed, the bonded substrate is immersed in a hydrofluoric acid aqueous solution, and the TEOS etching mask 203 is peeled off.

Next, in order to remove the silicon thin film remaining on the electrode extraction portion 29, a silicon mask is attached to the surface of the silicon substrate, RF power 200W, pressure 40Pa (0.3 Torr), CF ₄ flow rate 30 cm ³ / min (30 sccm). Under these conditions, RIE dry etching is performed for 1 hour, and plasma is applied only to the electrode extraction portion to open (FIG. 13G). At this time, the gap between the electrodes is opened to the atmosphere.

Next, a silicon mask having an opening only in a portion (discharge chamber and reservoir portion) where the TEOS ink protective film 27 is to be formed is attached to the surface of the silicon substrate. Then, a TEOS ink protective film 27 is formed to a thickness of 0.1 μm on the upper surface of the silicon substrate by plasma CVD (FIG. 13H). The TEOS ink protective film 27 is formed, for example, at a temperature of 360 ° C., a high frequency output of 250 W, a pressure of 66.7 Pa (0.5 Torr), a gas flow rate of TEOS flow rate of 100 cm ³ / min (100 sccm), and an oxygen flow rate of 1000 cm ³ / min ( 1000 sccm). The TEOS ink protective film may be a SiO ₂ film formed by sputtering other than plasma CVD.
The ink protective film 27 has the effect of preventing the corrosion of the flow path due to the ink, and also has the effect of reducing the warpage of the diaphragm portion because the stress of the insulating film 26 and the stress of the ink protective film 27 are offset.

Further, a common electrode 28 made of a metal such as Pt is formed on the end portion of the surface of the silicon substrate by a sputtering method using a metal mask or the like.
Further, the ink supply port 35 is formed by performing laser processing from the hole portion serving as the ink supply port 35 of the electrode substrate 3 and penetrating the bottom of the reservoir portion of the silicon substrate 200.
And an epoxy resin is poured along the open end part of the gap between electrodes, and the gap between electrodes is sealed. With this sealing material 37, the gap between the electrodes is in a sealed state.
As described above, each part of the cavity substrate 2 is manufactured. As shown in FIG. 13 (i), the nozzle substrate 1 prepared in advance is bonded to the upper surface of the cavity substrate 2 with an epoxy adhesive.

  Finally, as shown in FIG. 13 (j), the main body of the inkjet head 10 shown in FIG. 4 is obtained by cutting into individual heads by dicing.

  According to the inkjet head manufacturing method of the present embodiment, the electrode substrate has a function of reinforcing the support of the silicon substrate by using a method of forming each part such as a discharge chamber after the silicon substrate and the electrode substrate are joined. Therefore, the silicon substrate can be easily handled. Therefore, damages such as cracks and chipping of the silicon substrate can be reduced, and the substrate can be increased in diameter. If the diameter can be increased, a large number of inkjet heads can be taken out from a single substrate, so that productivity can be improved.

  In the above embodiment, the electrode substrate, the electrostatic actuator using the electrode substrate, the ink jet head, and the manufacturing method thereof have been described. However, the present invention is not limited to the above embodiment, and the idea of the present invention. Various modifications can be made within the range of For example, by changing the liquid material ejected 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

Sectional drawing which shows schematic structure of the electrostatic actuator provided with the electrode substrate which concerns on Embodiment 1 of this invention. AA sectional drawing of FIG. FIG. 5 is an exploded perspective view illustrating a schematic configuration of an inkjet head according to a second embodiment of the invention. FIG. 4 is a cross-sectional view of an inkjet head showing a schematic configuration of the right half of FIG. 3. FIG. 5 is a top view of the ink jet head of FIG. 4. Sectional drawing of the manufacturing process which shows the 1st example of the manufacturing method of the electrode substrate for inkjet heads of this invention. Sectional drawing of the manufacturing process following FIG. Sectional drawing of the manufacturing process which shows the 2nd example of the manufacturing method of the electrode substrate for inkjet heads of this invention. Sectional drawing of the manufacturing process following FIG. The top view showing the condition of the mask film formation used in the manufacturing method of the 2nd example. The top view of the individual electrode after removing the unnecessary part of the electrode film formed into the laminated form. Sectional drawing of the manufacturing process which shows the manufacturing method of the inkjet head of this invention. Sectional drawing of the manufacturing process following FIG.

DESCRIPTION OF SYMBOLS 1 Nozzle board | substrate, 2 cavity board | substrate, 3 electrode board | substrate, 4 drive means, 5 electrostatic actuator, 10 inkjet head, 11 nozzle hole, 13 orifice, 21 discharge chamber, 22 diaphragm (movable electrode member), 23 reservoir, 26 insulation Membrane, 28 Common electrode, 29 Electrode takeout part, 31 Electrode (fixed electrode member, individual electrode), 31a to 31d Step part, 32 Recess, 33 Communication groove, 35 Ink supply port, 37 Sealing material, 300 Glass substrate, 311 ~ 314 Electrode film.

Claims (13)

  An electrode substrate in which an electrode is formed in a recess formed in a substrate, wherein the electrode is composed of a multi-layered structure formed by laminating electrode materials so as to have a stepped step portion. Electrode substrate.   The electrode substrate according to claim 1, wherein the recess is formed in a single stage so as to have a certain depth.   The electrode substrate according to claim 1, wherein the concave portion is formed by one etching.   The electrode substrate according to claim 1, wherein a borosilicate glass substrate is used as the substrate.   5. An electrostatic actuator comprising: an electrode substrate according to claim 1; and an elastically deformable movable electrode member bonded to the electrode substrate through an insulating film and a gap so as to face the electrode.   6. The static step according to claim 5, wherein the step portions of the plurality of steps of the electrode are formed substantially symmetrically so that the gap length at the center portion is the largest and the gap lengths at both end portions are the smallest. Electric actuator.   A discharge chamber provided in a flow path communicating with the nozzle hole, an elastically deformable movable electrode member that constitutes the bottom wall of the discharge chamber, and a fixed electrode disposed opposite to the movable electrode member via an insulating film and a gap An electrostatic drive type droplet discharge head comprising: an electrode member; and a drive unit that generates an electrostatic force between the movable electrode member and the fixed electrode member, wherein the fixed electrode member is the fixed electrode member. A droplet discharge head comprising the electrode substrate according to any one of claims 1 to 4. Forming a recess having a certain depth on the substrate by etching;
A laminate of electrode films having stepped step portions by repeating the step of patterning and etching the electrode material formed on the surface of the substrate including the recesses, and then patterning and etching the formed electrode material. Forming in the recess;
A method for manufacturing an electrode substrate, comprising:   9. The method of manufacturing an electrode substrate according to claim 8, wherein the stepped step portion is formed in the final electrode film. Forming a recess having a certain depth on the substrate by etching;
Forming a stacked body of electrode films having stepped steps by repeating mask film formation for forming an electrode material using a mask on the surface of the substrate including the recesses a plurality of times;
Finally, by patterning and etching the laminate of the electrode film, removing the electrode film part other than the necessary part,
A method for manufacturing an electrode substrate, comprising:   11. The electrode substrate according to claim 8, wherein the stepped step portions are formed substantially symmetrically so that the center portion is the lowest and the both end portions are the highest. Production method.   A movable electrode member that is elastically deformable is bonded to an electrode substrate manufactured by the manufacturing method according to any one of claims 8 to 11 through an insulating film and a gap so as to face the laminate of the electrode films. A manufacturing method of an electrostatic actuator characterized by the above. A step of bonding the silicon substrate to the electrode substrate manufactured by the manufacturing method according to claim 8, and then processing the silicon substrate into a thin plate;
Forming a recess serving as a discharge chamber by etching on a silicon substrate processed into a thin plate, and a method for manufacturing a droplet discharge head.

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