JP2007055160A - Manufacturing method for electrode substrate, manufacturing method for electrostatic actuator, and manufacturing method for liquid droplet delivering head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an electrode substrate which enables reduction of the manufacturing cost in the manufacturing method for the electrode substrate with a plurality of step parts, and to provide a manufacturing method for an electrostatic actuator using the electrode substrate, and a manufacturing method for a liquid droplet delivering head. <P>SOLUTION: In the manufacturing method for the electrode substrate wherein a recessed part 32 for forming an electrode with the plurality of stair-like step parts is formed on a substrate to be worked, step parts of a maximum of 2<SP>n</SP>steps are formed on a bottom face of the recessed part 32 by repeating patterning and etching of an etching mask by n+1 times so that the electrode 31 has the stair-like step parts 32a to 32d of (2<SP>(n-1)</SP>+1) to 2<SP>n</SP>steps in the width direction or longitudinal direction of the recessed part 32. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode substrate manufacturing method applied to an electrostatic drive type electrostatic actuator, an electrostatic actuator manufacturing method using the electrode substrate, and a droplet discharge head manufacturing method using the electrostatic actuator.

  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 plate in which a plurality of nozzle holes for discharging ink droplets are formed, and an ink in a discharge chamber, a reservoir, or the like that is joined to the nozzle plate and communicates with the nozzle holes. And a cavity plate in which a flow path is formed, and an ink droplet is ejected from a selected nozzle hole by applying pressure to the ejection chamber by a 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. The individual electrode is formed of ITO (Indium Tin Oxide) or the like on the bottom surface of the recess formed on the surface of the glass substrate in order to ensure a predetermined gap length so as to enable displacement of the diaphragm.
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.

Such an electrostatic drive type ink jet head is required to have a high density, while ensuring an ink discharge amount without causing an increase in drive voltage. As one of the measures, a method has been proposed in which the gap length between the individual electrode and the diaphragm is formed in a multi-stepped shape by forming the bottom surface of the concave portion of the glass substrate in a multi-stepped shape (for example, Patent Documents). 1).
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), a predetermined ink discharge amount can be ensured.

JP 2000-318155 A (first page, FIG. 2)

By the way, regarding the manufacturing method of the electrostatic actuator, Patent Document 1 describes that "in an electrostatic actuator having n stepped steps and n gap lengths, ... nth gap patterning and etching. In this way, by repeating the gap patterning and etching, a gap having a number of steps is formed in the silicon oxide film or the glass substrate. ”(Page 5, column 7, line 22 to line No. 5) 8 column 19 line).
However, in such a manufacturing method, as the number of steps increases, the number of times of patterning and etching increases proportionally, thereby increasing the number of steps and lowering the yield. There is a problem of rising.

  In view of the above-described problems, the present invention provides a method for manufacturing an electrode substrate having a plurality of steps, and a method for manufacturing an electrode substrate capable of reducing manufacturing costs, as well as an electrostatic actuator using the electrode substrate. It is an object to provide a manufacturing method and a manufacturing method of a droplet discharge head.

In order to solve the above-mentioned problems, an electrode substrate manufacturing method according to the present invention includes an electrode substrate in which a recess for forming an electrode having a plurality of stepped step portions of four or more steps is formed on a substrate to be processed. A manufacturing method comprising:
Etching n + 1 times so that the electrode has a stepped step portion of (2 ^(n-1) +1) to 2 ⁿ (where n is an integer) in the width direction or longitudinal direction of the recess. By repeating mask patterning and etching, a maximum of 2 ⁿ step portions are formed on the bottom surface of the recess.

According to the present invention, since a step portion of a maximum of 2 ⁿ steps is formed on the bottom surface of the recess by repeating n + 1 etching patterning and etching, the number of patterning and etching steps can be increased even if the number of steps is increased. Since it increases only logarithmically, man-hours are reduced and the yield is improved. Therefore, the effect of reducing the manufacturing cost is extremely large.

The electrode substrate manufacturing method according to the present invention is a method for manufacturing an electrode substrate in which a recess for forming an electrode having a plurality of stepped step portions of four or more steps is formed on a substrate to be processed. ,
Etching n + 1 times so that the electrode has a stepped step portion of (2 ^(n-1) +1) to 2 ⁿ (where n is an integer) in the width direction or longitudinal direction of the recess. By repeating mask patterning and etching, a maximum of 2 ⁿ step portions are formed on the bottom surface of the recess, and the etching portion is overlapped in the second and subsequent etching mask patterning to form a depression at the boundary of the step portion. Is formed.

  In the patterning of the etching mask, if alignment misalignment occurs, a protrusion is formed at the boundary of the stepped portion. When such a protrusion is generated, the vibration plate, which is the other electrode, is coupled when the electrostatic actuator is driven. It becomes an obstacle to contact (the contact of the diaphragm along the stepped portions of one electrode in a deformed manner is referred to as “coupled contact”) and hinders driving of the electrostatic actuator. Therefore, by configuring as in the present invention, it is possible to form a recess without generating a protrusion at the boundary portion of the stepped portion by overlapping etching portions in the second and subsequent etching mask patterning.

Moreover, in the manufacturing method of the electrode substrate of this invention, it is preferable to use a glass substrate as a to-be-processed substrate.
By using the glass substrate, the glass substrate and the silicon diaphragm can be easily and firmly bonded using the anodic bonding method in which bonding technology is established.

The manufacturing method of the electrostatic actuator according to the present invention is such that the electrode substrate manufactured by any one of the above manufacturing methods is opposed to the electrode and has a stepped gap length of a maximum of 2 ⁿ steps, The silicon diaphragm is joined via an insulating film.
According to the present invention, a high-performance electrostatic actuator can be provided as a driving device for a micro device applied to a wide range of applications.

Further, it is preferable that the gap length is the largest at the center, the smallest at both ends, and substantially symmetrical.
In particular, when this electrostatic actuator is used for a droplet discharge head such as an inkjet head, the elastic deformation of the diaphragm is symmetrical with respect to the center by configuring as in the present invention. The amount can be obtained and stable ejection characteristics can be obtained.

A method for manufacturing a droplet discharge head according to the present invention is a method for manufacturing a droplet discharge head using any one of the above-described electrostatic actuator manufacturing methods.
According to the present invention, it is possible to provide a low-density and inexpensive droplet discharge head having stable discharge characteristics.

Embodiment 1. FIG.
Hereinafter, an embodiment of an electrostatic actuator to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of the electrostatic actuator according to the first embodiment.
The electrostatic actuator is formed in a recess 32 of the electrode substrate 3 and a diaphragm 22 made of silicon or the like constituting one electrode, and a plurality of stepped gap lengths Gi (here) Then, it is the structure provided with the counter electrode 31 which opposes so that it may have i = 1-4). An insulating film 26 made of SiO ₂ or TEOS (Tetraethylorthosilicate, Tetraethoxysilane) is formed on the surface of the diaphragm 22 that faces the counter electrode 31, and the diaphragm 22 and the electrode substrate are formed. 3 is bonded via an insulating film 26. The insulating film 26 is provided for the purpose of preventing dielectric breakdown or short circuit when the electrostatic actuator is driven.
Further, a drive control circuit 4 for applying a pulse voltage between the diaphragm 22 and the counter electrode 31 is connected between the electrodes.

  The recess 32 is formed in a substantially rectangular plane, and the bottom surface of the recess 32 is formed to have symmetrical stepped portions 32a, 32b, 32c, and 32d so that the depth increases toward the center. Has been. Accordingly, the counter electrode 31 is formed on the bottom surfaces of the plurality of steps in the recess 32 with substantially the same thickness by, for example, ITO (Indium Tin Oxide), and the step portion having the same number of steps as the bottom surface of the recess 32 is formed between the counter electrode 31 and the diaphragm 22. That is, it has a stepped gap length Gi. Note that these stepped portions can be provided in either the width direction (short side direction) or the longitudinal direction (long side direction) of the recess 32. FIG. 1 shows a cross section of the recess 32 in the width direction (short side direction).

In the case of the electrostatic actuator of FIG. 1, the bottom surface of the recess 32 and the counter electrode 31 are formed so as to have four steps, and the gap length Gi satisfies G4>G3>G2> G1. The gap length Gi is, for example, 140 μm at the largest (deep) central portion, and is, for example, 80 μm at the smallest (shallow) both ends.
Further, the step of each step of the counter electrode 31 is preferably formed so as to become smaller toward the center of the recess 32. However, you do n’t have to do that,
(G2-G1) ≧ (G3-G2) ≧ (G4-G3), where G1 ≧ (G2-G1)
It is good. In this way, the entire vibration plate 22 is easily brought into contact with the counter electrode 31 as shown by the dotted line in FIG. 1 at a driving voltage at which the vibration plate 22 and the counter electrode 31 are in contact with each other at the portion where the gap length Gi is the smallest.

The thickness of the counter electrode 31 is normally a constant thickness at each stage. Accordingly, when the depth of the concave portion 32 corresponding to G1, G2, G3, and G4 of the gap length Gi is A1, A2, A3, and A4, and the thickness of the counter electrode 31 is t,
A1 = G1 + t, A2 = G2 + t, A3 = G3 + t, A4 = G4 + t
It has become. That is, A4>A3>A2> A1.
In addition, the thickness t of the counter electrode 31 is preferably formed to be thicker than any step of each step on the bottom surface of the recess 32. This
Since the relationship of t>(A2-A1)>(A3-A2)> (A4-A3) is established, step disconnection (disconnection) at the step portion of the counter electrode 31 can be prevented.

  In the electrostatic actuator configured as described above, when a sufficient voltage is applied between the diaphragm 22 and the counter electrode 31 so that the diaphragm 22 corresponding to the gap length G1 contacts the counter electrode 31. The diaphragm 22 is held in contact with the first-stage counter electrode 31 having the smallest gap length. At this time, at the boundary corresponding to the gap lengths G1 and G2, the gap length temporarily becomes (G2-G1), and thereby a large electrostatic attraction force acts on the diaphragm 22, so that the next gap length G2 The portion of the diaphragm 22 corresponding to is also in contact with the counter electrode 31 at the same voltage. As described above, since the forward feeding action is continuously induced up to the portion corresponding to G4 having the largest gap length, the diaphragm 22 in the portion corresponding to the gap length G1 is eventually necessary and sufficient to contact the counter electrode 31. The entire diaphragm 22 can be brought into contact with the counter electrode 31 with a small voltage. Hereinafter, the manner or contact state in which the diaphragm 22 abuts along each step of the counter electrode 31 as described above will be referred to as “coupled abutment”. The diaphragm 22 does not necessarily have to be in contact with all the step portions of the counter electrode 31. For example, there is a case where the diaphragm 22 does not come into contact with the lowermost counter electrode 31, and such a state is also included in the concept of “coupled contact”.

  Therefore, the electrostatic actuator of the present embodiment can increase the displacement of the diaphragm 22 without increasing the driving voltage or even with a low driving voltage. Therefore, when used in an ink jet head as will be described later, the ink discharge amount can be stably secured.

Next, the manufacturing method of the electrode substrate 3 of the present invention will be described with reference to the process diagrams of FIGS. In the present invention, the stepped portion having the number of steps (2 ^(n-1) +1) to 2 ⁿ is formed by patterning and etching of the etching mask n + 1 times. Here, for example, a manufacturing method of the electrode substrate 3 having four steps is shown. Note that the thickness of the substrate, the etching depth, and the like in the following description are merely examples, and do not limit the present invention.

  First, as shown in FIG. 2A, a borosilicate glass substrate 300 processed to a predetermined thickness, for example, 1 mm, is prepared as a substrate to be processed. Next, an etching mask 301 made of chromium (Cr) is formed on the surface of the glass substrate 300 by, for example, sputtering, and a resist (not shown) having a predetermined shape is patterned and etched on the surface of the etching mask 301 by photolithography. Then, openings having shapes corresponding to the second step 32b and the fourth step 32d of the recess 32 are formed in the etching mask 301 (FIG. 2B).

  Next, by etching the glass substrate 300 with, for example, a hydrofluoric acid aqueous solution, for example, second and fourth recesses 305b and 305d are formed (FIG. 2C). At this time, the etching depth of the second-stage recess 305b is substantially equal to (A2-A1) in FIG. 1, and the etching depth of the fourth-stage recess 305d is (A4-A3) in FIG. ) To be approximately equal. Next, after the resist is stripped with an organic stripping solution or the like, the glass substrate 300 is immersed in a chrome etching solution to remove the etching mask 301 (FIG. 2D).

  Next, the second etching mask 302 is patterned and etched by photolithography so as to cover the portion from the end of the glass substrate 300 to the second-stage recess 304b (FIG. 2E). That is, an etching mask 302 made of chromium, for example, is formed on the surface of the glass substrate 300 of FIG. 2D by sputtering, and a resist (not shown) having a predetermined shape is patterned and etched on the surface of the etching mask 302 by photolithography. Then, openings having shapes corresponding to the third and fourth portions are formed in the etching mask 302. Then, for example, by etching the glass substrate 300 with a hydrofluoric acid aqueous solution, the third and fourth stage portions are dug down (FIG. 3F). At this time, the etching depth of the third stage is made substantially equal to (A3-A2) in FIG. Next, after the resist is stripped with an organic stripper or the like, the glass substrate 300 is immersed in a chrome etchant and the etching mask 302 is removed, so that the step portions 32b to 32d from the second step to the fourth step are formed stepwise. (FIG. 3 (g)).

  Next, the third etching mask 303 is patterned and etched by photolithography so as to cover the surface portion from the end of the glass substrate 300 to the end of the first stage (FIG. 3H). That is, an etching mask 303 made of chromium, for example, is formed by sputtering on the surface of the glass substrate 300 in FIG. 3G, and a resist having a predetermined shape (not shown) is patterned on the surface of the etching mask 303 by photolithography. Then, an opening having a shape corresponding to the first to fourth stage portions is formed in the etching mask 303. Then, for example, by etching the glass substrate 300 with a hydrofluoric acid aqueous solution, the first stage portion is dug down (FIG. 3I). At this time, the etching depth of the first stage is set to A1 in FIG. Then, after the resist is stripped with an organic stripping solution or the like, the glass substrate 300 is immersed in a chrome etching solution and the etching mask 303 is removed, so that the step portions 32a to 32d from the first step to the fourth step are formed stepwise. (FIG. 3 (j)).

  As described above, by repeatedly performing patterning and etching on the etching masks 301, 302, and 303 three times in total, the concave portion 32 having the four step portions 32a to 32d on the bottom surface can be formed. Note that the steps and depths A1, A2, A3, and A4 of each step can be formed to required dimensions by adjusting the etching time. For example, the etching depth is A1 = 180 nm, A2 = 200 nm, A3 = 220 nm, and A4 = 240 nm.

Thereafter, for example, an ITO (Indium Tin Oxide) film 306 is formed on the entire surface of the glass substrate 300 including the concave portion 32 by sputtering (FIG. 4K). The ITO film 306 is formed to be thicker than any step of the recess 32 formed in a step shape. For example, the ITO film 306 is formed so that t = 0.1 μm in FIG. Then, a resist (not shown) is patterned and etched by photolithography to form an ITO pattern corresponding to the portion of the counter electrode 31 (FIG. 4L).
The material of the counter electrode 31 is not limited to ITO, and a metal such as chromium may be used. However, since ITO is transparent, it is generally easy to confirm whether or not a discharge has occurred. ITO is used.

Thus, the electrode substrate 3 shown in FIG. 1 is manufactured. Thereafter, the diaphragm 22 is opposed to the counter electrode 31 and anodic bonded to the electrode substrate 3 via the insulating film 26, whereby the electrostatic actuator shown in FIG.
In the above description, a glass substrate is used as the substrate to be processed, but the substrate material is not particularly limited, and for example, a silicon substrate can be used.

  According to the method for manufacturing the electrode substrate 3 of the present embodiment, in order to form the four step portions 32a to 32d on the bottom surface of the recess 32, conventionally, patterning and etching of the etching mask is performed four times for each step portion. However, in the present embodiment, since the patterning and etching of the etching mask are performed three times in total, the manufacturing cost of the electrode substrate can be reduced. As the number of steps increases, the number of times of patterning and etching increases only logarithmically, so that the manufacturing cost can be further reduced.

For example, FIG. 5 schematically shows an etching mask patterning method in the case where eight step portions 32 a to 32 h are formed on the bottom surface of the recess 32. In this case, the etching mask may be repeatedly patterned and etched a total of four times 301 to 304.
Accordingly, in general, the present invention can form the stepped portion having the number of steps of (2 ^(n-1) +1) to ²ⁿ by patterning and etching of the etching mask n + 1 times. Since the number of times of etching increases only logarithmically, man-hours can be reduced and the yield can be improved. Therefore, significant cost reduction is possible.

Next, in the etching mask patterning method of the present invention, FIGS. 6 and 7 show cases where misalignment occurs. A simple explanation will be given by taking the case of four stages as an example. Since the manufacturing method is as described above, the description is omitted.
For example, when alignment misalignment occurs in the patterning of the first etching mask 301 and the second etching mask 302 (see FIG. 6E), a protrusion is formed at the boundary between the second and third step portions. 307 occurs (see FIG. 7G). In this case, although a dent arises in the boundary part of the other level | step-difference part, a dent does not have a problem. However, when such a protrusion 307 occurs when the glass substrate 300 is etched, the protrusion 307 becomes an obstruction factor for the coupled contact of the diaphragm 22, and the electrostatic actuator cannot be driven satisfactorily. .

Therefore, in the present invention, as shown in FIG. 8 and FIG. 9, the second step and the third step are provided so that etching portions overlap in the patterning of the first etching mask 301 and the second etching mask 302. The etching mask is patterned so that a recess 308 is formed by etching at both boundary portions (see FIGS. 8E and 9F).
By providing the depression 308 at the boundary portion of the stepped portion in this way, it is possible to prevent a projection that becomes an obstructive factor for the coupled contact of the diaphragm 22 from occurring. Note that the recess 308 causes a similar recess in the counter electrode made of the ITO film, but there is no problem in driving the electrostatic actuator.

FIG. 10 is an explanatory diagram (table) illustrating the locations where the projections 307 are generated (boundary portions of the stepped portions) in the case of 4 to 8 steps and 16 steps. In each table, the horizontal axis represents the number of steps, and the vertical axis represents the number of patterning of the etching mask. In the table, a column with a number means that the step is etched, and a column without a number means that the step is not etched. Also, the numbers below the margin represent the locations where the protrusions are generated (boundary portions of the step portions).
As shown in this figure, the locations where the protrusions are generated vary depending on the etching mask patterning method. Therefore, care must be taken not to cause misalignment in the second and subsequent patterning. Therefore, in the second and subsequent times, the alignment is strictly performed so as not to cause misalignment in the patterning of the etching mask, or the etching portions overlap as described above, that is, there is a depression at the boundary of the stepped portion. Patterning may be performed to produce it.

Embodiment 2. FIG.
FIG. 11 is an exploded perspective view showing an exploded schematic configuration of a droplet discharge head using an electrode substrate and an electrostatic actuator manufactured by the manufacturing method of the present invention, and a part thereof is shown in cross section. Here, as an example of a droplet discharge head, a face discharge type electrostatic drive type inkjet head 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 can be similarly applied to an edge discharge type droplet discharge head.

  FIG. 12 is a cross-sectional view of the ink jet head showing a schematic configuration of the right half of FIG. 11, and schematically shows a deformed state of the diaphragm with a dotted line. FIG. 13 is a top view of the inkjet head of FIG. 2, and FIG. 14 is an enlarged cross-sectional view of the electrostatic actuator section. 11 and 12 are shown upside down from the normally used state.

  As shown in FIGS. 11 and 12, the inkjet head (an example of a droplet discharge head) 10 according to the present embodiment includes a nozzle plate 1 in which a plurality of nozzle holes 11 are provided at a predetermined pitch, and each nozzle hole 11. A cavity plate 2 provided with an ink supply path independently, and individual electrodes having a plurality of stepped gap lengths Gi (here, i = 1 to 3) in a stepped manner against the diaphragm 22 of the cavity plate 2. The electrode substrate 3 on which 31 is disposed is bonded. The electrode substrate 3 is manufactured by the manufacturing method described above.

  The nozzle plate 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 plate 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 plate 1, and the introduction port portion 11b is the nozzle plate 1. Are opened on the back surface (the surface on the bonding side to be bonded to the cavity plate 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. 12 of the nozzle plate 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 joining side with the cavity plate 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 plate 2 described later. The diaphragm portion 14 is provided to suppress pressure fluctuation in the reservoir 23.

  The cavity plate 2 is made of, for example, a (110) plane-oriented silicon single crystal substrate having a thickness of about 50 μm (this substrate is also simply referred to as a silicon substrate hereinafter). This silicon substrate has a boron-doped layer, and by performing anisotropic dry etching and anisotropic wet etching on the silicon substrate, the recesses 24 and 25 for forming the discharge chamber 21 and the reservoir 23 of the ink flow path are high. Formed with precision. A plurality of recesses 24 are independently formed at positions corresponding to the nozzle holes 11. Therefore, as shown in FIG. 12, when the nozzle plate 1 and the cavity plate 2 are joined, the recesses 24 form discharge chambers 21, communicate with the nozzle holes 11, respectively, and the orifices 13 serving as ink supply ports. Both communicate with each other. And the diaphragm 22 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, as described above, the (110) orientation silicon single crystal substrate is used for the cavity plate 2 by performing anisotropic etching and anisotropic wet etching on the silicon substrate in two stages. This is because the side surfaces of the recesses and grooves can be etched perpendicularly to the upper or lower surface of the silicon substrate and with high dimensional accuracy, thereby increasing the density of the inkjet head, stabilizing the ejection characteristics, and reducing the cost. Can be achieved.

Further, an insulating film 26 made of, for example, 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 plate 2, that is, the surface facing the electrode substrate 3.
On the upper surface of the cavity plate 2, that is, the surface facing the nozzle plate 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 produced from a glass substrate having a thickness of 1 mm, for example, by the manufacturing method described above. As shown in FIG. 11, the electrode substrate 3 is provided with a concave portion 32 having a rectangular shape in plan view at the position of the surface of the cavity plate 2 facing each diaphragm 22. In this example, three stepped step portions 32a, 32b, and 32c are provided in the longitudinal direction on the bottom surface of the recess 32, and the same number of step portions are provided on the step portions 32a, 32b, and 32c. The electrode, that is, the individual electrode 31 is formed by sputtering with a thickness of 0.1 μm using, for example, ITO. Therefore, the individual electrode 31 is configured to have stepped gap lengths G1, G2, and G3 between the electrode substrate 3 and the cavity plate 2 and the diaphragm 22. 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 portion.
The individual electrode 31 has a lead portion 31a and a terminal portion 31b. Therefore, a communication groove 33 is formed in the recess 32 to pull out the lead portion 31a. The lead part 31a may be drawn out from any stage from the top to the bottom of the individual electrode 31.

  A flexible wiring board (not shown) is connected to the terminal portion 31 b of the individual electrode 31. As shown in FIGS. 11 to 13, these terminal portions 31b are exposed in an electrode extraction portion 29 in which the end portion of the cavity plate 2 is opened for wiring.

  As described above, the nozzle plate 1, the cavity plate 2, and the electrode substrate 3 are bonded together 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. 12 and 13, the drive control circuit 4 such as an IC driver is connected to the terminal portion 31 b of each individual electrode 31 and the common electrode 28 provided on the cavity plate 2. They are connected via a 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 4 is an oscillation circuit that controls the supply and stop of charges to the individual electrodes 31. 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 stepped portions so that the central portion in the longitudinal direction is the lowest, and the gap length Gi is thereby increased stepwise. 22 is displaced forwardly from the stepped portion of the first stage 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 11 as an ink droplet. 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 bottom surface of the recess 32 of the electrode substrate 3 has stepped steps 32a to 32c in the longitudinal direction, and the same number of individual electrodes 31 are formed on the bottom surface. Therefore, the elastic deformation of the diaphragm 22 is deformed and contacted along the stepped portion of the individual electrode 31 as shown by the dotted line in FIG. As a result, the volume increase of the discharge chamber 21 increases, and as a result, a necessary ink discharge amount can be ensured 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.

Embodiment 3. FIG.
FIG. 15 is a cross-sectional view in the width direction of an ink jet head showing another embodiment of the present invention, and FIG. 16 is a top view taken along the line AA of FIG. That is, it is a plan view of the electrode substrate 3.
In the above-described embodiment, the longitudinal section of the recess 32 in the electrode substrate 3 is shown. However, the present embodiment shows the section in the width direction of the recess 32 and the plane of the electrode substrate 3.
In the width direction of the concave portion 32, stepped step portions 32a, 32b, 32c and 32d having a maximum of 2 ⁿ steps are formed in the same manner as the longitudinal direction, and the individual electrodes 31 having the same number of stepped gap lengths on the bottom surface thereof. Can be formed.

  Also in the ink jet head 10 of the present embodiment, when driven, the diaphragm 22 is in continuous contact with the individual electrode 31 having a stepped gap length in the width direction as shown by a dotted line in FIG. Thus, the necessary ink discharge amount can be ensured without increasing the drive voltage, and stable discharge can always be realized.

In the above embodiment, the electrode substrate manufacturing method, the electrostatic actuator and the inkjet head using the electrode substrate, and the manufacturing method thereof have been described, but the present invention is not limited to the above embodiment, Various modifications can be made within the scope of the idea of the present invention. 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
In addition, although the vibration plate has been described as a thin plate type in which both ends are supported or a substantially rectangular whole circumference is fixed, a cantilever type may be used. In this case, the stepped portions of the counter electrode need only be on one side. Further, the shape of the diaphragm is not particularly limited. For example, it may be circular, and in this case, it is suitable to provide the stepped portion of the counter electrode in a concentric manner. An electrostatic actuator having a circular diaphragm can be used, for example, in a diaphragm portion of a micropump.

Sectional drawing which shows schematic structure of the electrostatic actuator which concerns on Embodiment 1 of this invention. Sectional drawing of the manufacturing process which shows the manufacturing method of the electrode substrate (in the case of 4 steps | paragraphs) of this invention. Sectional drawing of the manufacturing process following FIG. Sectional drawing of the manufacturing process following FIG. Sectional drawing of the manufacturing process which shows the manufacturing method of the electrode substrate (in the case of 8 steps | paragraphs) of this invention. Sectional drawing of the manufacturing process of an electrode substrate (in the case of 4 steps | paragraphs) when a protrusion generate | occur | produces in the boundary part of a level | step-difference part. Sectional drawing of the manufacturing process following FIG. Sectional drawing of the manufacturing process of the electrode substrate (in the case of 4 steps | paragraphs) when providing a hollow in the boundary part of a level | step-difference part. Sectional drawing of the manufacturing process following FIG. Explanatory drawing which shows an example of the location (border part of a level | step-difference part) where a protrusion generate | occur | produces about the case of 4-8 steps and 16 steps. FIG. 5 is an exploded perspective view illustrating a schematic configuration of an inkjet head according to a second embodiment of the invention. FIG. 12 is a cross-sectional view of an inkjet head showing a schematic configuration of the right half of FIG. The top view of the inkjet head of FIG. The expanded sectional view of an electrostatic actuator part. Sectional drawing of the width direction of the inkjet head which concerns on Embodiment 2 of this invention. The AA arrow top view of FIG.

Explanation of symbols

1 Nozzle plate, 2 Cavity plate, 3 Electrode substrate, 4 Drive control circuit, 10 Inkjet head, 11 Nozzle hole, 13 Orifice, 21 Discharge chamber, 22 Vibration plate, 23 Reservoir, 26 Insulating film, 28 Common electrode, 29 Extracting electrode Part, 31 counter electrode (individual electrode), 32 recessed part, 32a to 32h step part, 33 communication groove, 35 ink supply port, 37 sealing material, 300 glass substrate, 301 to 304 etching mask, 307 protrusion, 308 depression.

Claims (6)

An electrode substrate manufacturing method for forming a recess for forming an electrode having a plurality of stepped step portions of four or more steps on a workpiece substrate,
Etching n + 1 times so that the electrode has a stepped step portion of (2 ^(n-1) +1) to 2 ⁿ (where n is an integer) in the width direction or longitudinal direction of the recess. A method of manufacturing an electrode substrate, comprising forming a stepped portion having a maximum of 2 ⁿ steps on the bottom surface of the recess by repeating mask patterning and etching. An electrode substrate manufacturing method for forming a recess for forming an electrode having a plurality of stepped step portions of four or more steps on a workpiece substrate,
Etching n + 1 times so that the electrode has a stepped step portion of (2 ^(n-1) +1) to 2 ⁿ (where n is an integer) in the width direction or longitudinal direction of the recess. By repeating mask patterning and etching, a maximum of 2 ⁿ step portions are formed on the bottom surface of the recess, and the etching portion is overlapped in the second and subsequent etching mask patterning to form a depression at the boundary of the step portion. Forming an electrode substrate.   3. The method for manufacturing an electrode substrate according to claim 1, wherein a glass substrate is used as the substrate to be processed. A silicon diaphragm is formed on the electrode substrate manufactured by the manufacturing method according to claim 1 so as to face the electrode and have a stepped gap length of 2 ⁿ steps at maximum. The manufacturing method of the electrostatic actuator characterized by joining through this.   5. The method of manufacturing an electrostatic actuator according to claim 4, wherein the gap length is the largest at the center and the smallest at both ends, and is substantially symmetric. A method for manufacturing a droplet discharge head, wherein the droplet discharge head is manufactured using the method for manufacturing an electrostatic actuator according to claim 4.

Images