JP3227285B2 - Method of manufacturing inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an ink jet head for selectively depositing ink droplets on an image recording medium.

[0002]

2. Description of the Related Art As a conventional piezoelectric ink jet printer head, there is a Kaiser method in which a partition wall of a channel filled with ink is deformed by utilizing the bending of a piezoelectric element due to bimorph, and ink is ejected by the pressure at that time. For example, it is disclosed in Japanese Patent Publication No. 57-20904.

Also, a laminated actuator in which one end of a piezoelectric element composed of laminated piezoelectric plates is fixed to a base, and the other end is opposed to a nozzle opening with the other end as a free end, and an ink reservoir is formed between the free end and the nozzle opening. There is a system, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-1052.

Further, there is a pressure chamber contraction method in which one pressure chamber is formed by hollowing out one piezoelectric plate polarized in the thickness direction and laminating the piezoelectric plates to constitute a multi-nozzle ink jet head. JP-A-4-22317
No. 4 discloses this.

[0005]

However, each of the above-mentioned conventional systems has a problem. In the Kaiser method, in order to form an ink droplet having a large flying force, sufficient deformation of the piezoelectric element is required, and a piezoelectric element having an extremely small expansion / contraction ratio needs to have a sufficient size. Therefore, the pressure chamber becomes large, the pitch of the multi-nozzles cannot be increased, and a large voltage is required to drive the piezoelectric element.

The stacked actuator system has many problems as described in detail below.

FIG. 12 is a sectional view showing the configuration of the laminated actuator system disclosed in Japanese Patent Laid-Open No. 4-1052. In this configuration, a part of the wall of the ink pressure chamber 90 functions as a vibration plate 91, which is supported by the free end 92a of the elongated rod-shaped piezoelectric element 92, as described later. Container configuration cannot be adopted. For this reason, it takes more time for the ink pressure chamber to return to the initial state in which no voltage is applied, compared to a head formed of a hard container, and thus there is a limit to the continuous response of ink ejection.

Further, since the extension of the plate-like piezoelectric element 92 in the direction perpendicular to the thickness direction is used, the deformation amount is not integrated even when the piezoelectric elements 92 are laminated. Since the deformation of the piezoelectric material is small, the piezoelectric element 92 needs to have a sufficient length in order to take a sufficient displacement amount to eject ink. For this reason, the entire head is increased in size, the structure is complicated, and the manufacturing is difficult and expensive due to the requirement of high-precision tolerance in joining the free end 92a of the piezoelectric element 92 and the diaphragm 91.

FIG. 13 is a sectional view showing a laminated actuator system having a different structure from that of FIG. 9 disclosed in Japanese Patent Laid-Open No. 4-1052. Free end 1 of laminated piezoelectric element 101
01a is opposed to the nozzle opening 102, and the free end 10a
The ink between the nozzle opening 1a and the nozzle opening 102 is pushed by the free end 101a of the piezoelectric element 101, and the ink is ejected by the dynamic pressure at this time. In this configuration, at the same time as the free end 101a moves, the ink escapes into the ink reservoir in a direction perpendicular to the nozzle opening 102. For this reason, high efficiency cannot be expected, and the flying capability is limited by the nozzle opening 102 and the free end 10 of the piezoelectric element 101.
The accuracy requirement is severe because it depends on the size of the gap 1a.

Further, the volume extruded to eject ink is proportional to the area and length of the piezoelectric element 101 and the applied voltage. For this reason, a sufficient element size is required, so that there is a problem that the size of the ink jet head is increased.

Furthermore, it is necessary to maintain the insulation between the filled ink and the electrodes so that electrolysis of the ink does not occur in the water-based ink. However, since the electrode 103 is basically formed on the surface of a non-smooth piezoelectric material having pores or the like, the electrode 103 is missing on the pore, and even if an insulating film is provided on the surface of the electrode 103, the missing portion is not formed. A stable film cannot be formed, and complete electrical insulation cannot be obtained. For this reason, there is also a problem that the ink comes into contact with the missing portion and the electrode 103 is corroded due to a chemical change of the ink, or a gas is generated to make it impossible to discharge the ink.

An object of the present invention is to solve the problems caused by the structure and mechanism of the conventional piezoelectric ink jet, to have excellent performance such as ejection force and continuous response, to be driven at a low voltage, and to be compact. Another object of the present invention is to provide a method of manufacturing an inkjet head which is simple and easy to manufacture .

[0013]

In order to achieve the above object, a method of manufacturing an ink jet head according to the present invention employs the following means .

Manufacturing of an ink jet head according to the present invention
The method comprises laminating a plurality of plate-shaped piezoelectric materials having a hollow portion serving as a pressure chamber and polarized in the thickness direction via a conductive material.
Forming a piezoelectric element block by
The piezoelectric element block is joined to the formed substrate,
An exposed surface of the plate where the piezoelectric element blocks are not joined;
Forming electrodes on the wall surface of the piezoelectric element block
When, forming grooves in said piezoelectric element block and the substrate
Process and the lid on which the ink supply port is formed
Bonding to the rack .

Production of an ink jet head according to the present invention
In the method , a plurality of the pressure chambers may be provided, and the lid may be provided for each of the pressure chambers.
Are joined .

Production of an ink jet head according to the present invention
The method is characterized in <br/> to the formation of the coating film to the pressure chamber of the partition wall.

Production of an ink jet head according to the present invention
The method is characterized in that the coating film is polyparaxylene.
It is characterized by that .

Production of an ink jet head according to the present invention
The method is characterized that you connect the drive electrode to the electrode of the substrate.

According to the above-described method for manufacturing an ink jet head of the present invention, since a part of the pressure chamber is formed by the piezoelectric element and the plate-like piezoelectric material is laminated, the amount of deformation of the piezoelectric element is reduced. It can be large enough. Therefore, a small-sized pressure chamber can be formed, and a high-density and small-sized inkjet head can be provided.

Further, since the pressure chamber is formed of a highly rigid partition wall, a substrate and a lid, there is a sufficient pushing force against the generated internal pressure. Therefore, it is possible to provide an ink jet head having a high response frequency of the pressure chamber and a high continuous response speed.

Further, the partition also serves as a drive actuator. Therefore, an inexpensive ink jet head having a small number of components can be provided.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an ink jet head according to an embodiment of the present invention will be described below with reference to the drawings.

Embodiment 1 FIGS. 1 and 2 show an ink jet head according to a first embodiment of the present invention. FIG. 1 is a sectional view showing a pressure chamber, and FIG. FIG. 4 is an exploded perspective view showing a part in a cutaway manner. Hereinafter, description will be made with reference to FIGS. 1 and 2 alternately.

As shown in FIGS. 1 and 2, the first plate-shaped piezoelectric material 1a polarized in the thickness direction and hollowed out at the center is provided with the first plate-shaped piezoelectric material 2a via the first conductive material 2a. Material 1a
And a third plate-shaped piezoelectric material polarized in the opposite direction to the second plate-shaped piezoelectric material 1b via the second conductive material 2b. 1c. Similarly, a necessary number of the conductive materials and the plate-like piezoelectric materials are sequentially laminated to form the partition walls 10.

The first conductive material 2a, the third conductive material 2c and the like are electrically connected to the first collector electrode 3a, and the second conductive material 2b and the fourth conductive material 2d are the second conductive material 2d. Conduction is established with the collecting electrode 3b.

With such a configuration, the first collector electrode 3a,
When a voltage is applied between the second collector electrodes 3b, a voltage is generated between the conductive materials, and an electric field is generated in the thickness direction of the plate-shaped piezoelectric material. For this reason, the partition 10 functions as a piezoelectric element.

A plurality of the partition walls 10 composed of the piezoelectric elements are arranged on a substrate 11 formed so as to open the ink ejection ports 12, and the partition walls 10 and the substrate 11 are fixed with an adhesive. Then, a plurality of depressions corresponding to the hollow portions of the plate-shaped piezoelectric material are formed.

This recess is used to cover the lid 1 with the ink supply port 13 open.
4, and a plurality of independent pressure chambers 15 are formed by fixing the partition 10 and the lid 14 with an adhesive.

In this embodiment, the ink jet port 12 is connected to the substrate 11
The ink supply port 13 was formed on the lid 14,
The ink ejection port 12 may be formed on the lid 14, and the ink supply port 13 may be formed on the substrate 11.

In the constructions shown in FIGS. 1 and 2,
Although 2 is formed in the substrate 11, a nozzle plate of another member may be attached to the substrate.

Further, the ink supplied from the ink supply port 13 is configured to flow directly into the pressure chamber 15, but a recess 30 is provided in a part of the partition wall 10 as shown in FIG. An ink supply channel for suppressing backflow of ink may be formed.

Further, the partition wall 10 is formed in a box shape from a plate-shaped piezoelectric material having an elliptical hollow portion. However, as shown in FIG. 4, a configuration in which a sealing plate 41 is attached to a U-shaped partition wall 40 as shown in FIG. Good.

Further, in the description, the electrodes made of a conductive material are not formed on the bonding surface of the partition wall 10 with the substrate 11 and the bonding surface of the partition wall 10 with the lid 14. The piezoelectric element may be driven.

Next, the operation of the ink jet head according to the first embodiment of the present invention will be described with reference to FIGS.

When a voltage is applied to the first drive electrode 16a and the second drive electrode 16b formed of a flexible wiring board connected to the first collector electrode 3a and the second collector electrode 3b, respectively, the first conductive material A voltage is generated between 2a and the second conductive material 2b. Then, an electric field is generated in the second plate-shaped piezoelectric material 1b in the thickness direction.

Since the second plate-like piezoelectric material 1b is polarized in the direction opposite to the electric field in the thickness direction, it contracts in the thickness direction. The thickness of the plate-like piezoelectric material is t, the amount of deformation is δt, the applied voltage is V,
When the thickness direction of the piezoelectric constant is d _33, the strain is proportional to the field _{strength, δt / t = d 33 V} / t, that is, the δt = d ₃₃ V.

The above equation means that the amount of deformation is proportional to the voltage and does not depend on the thickness of the piezoelectric material.

Each of the laminated plate-like piezoelectric materials undergoes the same deformation as the second plate-like piezoelectric material 1b, and the deformation in the entire thickness direction is caused by the plate-like piezoelectric material having electrodes formed on both surfaces. M × δt is obtained in proportion to the number m of stacked layers, and a large amount of deformation can be obtained, which is m times larger than one sheet.

Since the force of this deformation is large and the lid 14 approaches the substrate 11 by an amount substantially equal to the amount of deformation, when the sectional area of the pressure chamber is S, the volume of S × m × δt shrinks. Due to the contraction of the volume, a pressure is generated in the pressure chamber 15, and the ink droplet 17 is ejected from the ink ejection port 12.

Although a certain amount of volume change is required to form the ink droplets 17, in this embodiment, the amount of deformation of one plate-like piezoelectric material can be amplified by m times, so that the pressure chamber is cut off. The area S can be reduced to approximately 1 / m of that of a single piezoelectric element, and a small pressure chamber can be formed.

Therefore, since a plurality of pressure chambers can be mounted at high density, an ink jet head having a high density multi-nozzle head can be constructed.

Further, in the ink ejection characteristics, since the lid 14 is displaced toward the ink ejection port 12, this pressure directly acts on the ink ejection, and loss due to fluid resistance is small.

Further, since the pressure chamber 15 has a configuration in which the partition wall 10 is a continuous box-shaped wall and the open portion of the pressure chamber 15 is pressed by the substrate 11 and the lid 14, the pressure chamber 15 can sufficiently withstand the internally generated pressure. It has good rigidity.

Therefore, the response vibration to the distortion of the partition wall 10 and the substrate 11 and the lid 14 caused by the ink jetting operation is performed quickly, so that the continuous response is good. Therefore, since the number of ink jets per unit time can be increased, high-speed printing is possible.

Further, since the amount of deformation is amplified by lamination, the voltage to be applied required to obtain the required amount of deformation can be made lower than in the case of a single piezoelectric element. Therefore, low voltage driving is possible.

Further, the partition 10 is a drive actuator and also serves as a partition as a structure. For this reason, the number of parts is small, and there is no strict requirement for accuracy, and it is easy to manufacture and can be manufactured at low cost.

In the above description, the ink ejection operation by the contraction of the piezoelectric element has been described. However, the direction of the electric field and the direction of the polarization are made the same, and the plate-like piezoelectric material is stretched in the thickness direction to increase the pressure volume. By stopping the voltage application and returning the piezoelectric element to its original state, it is also possible to generate pressure and eject ink.

Next, a manufacturing method for forming the structure of the ink jet head according to the present invention will be described. FIGS. 5, 6, 7, and 8 are perspective views, partially in section, showing a method for manufacturing an ink jet head according to the first embodiment of the present invention. Hereinafter, description will be made in the order of the manufacturing process with reference to these drawings.

As shown in FIG. 5, a central portion of a first green sheet 50a made of piezoelectric ceramic which is a plate-shaped piezoelectric material is punched out in an elliptical shape, and a first exposed portion 51a is left on a part of the surface. One conductive material 52a is formed by a printing method.

Next, as shown in FIG. 6, a new second green sheet 50b to be a plate-like piezoelectric material is stacked on the first conductive material 52a, and the end face on the opposite side of the first exposed portion 51a. The second conductive material 52b is formed by a printing method so that the second exposed portion 51b remains in the portion located at the position.

As described above, the green sheets and the conductive material which become the plate-like piezoelectric material are alternately stacked and then subjected to the pressure sintering process, thereby obtaining the piezoelectric element block 5 as shown in FIG.
3 can be formed.

Then, as shown in FIG.
The piezoelectric element block 53 is adhered on the glass substrate 11 on which the substrate 2 is formed. Further, after masking the upper surface 54 of the piezoelectric element block, an electrode 55 is formed by forming a conductive material such as gold (Au) on the entire surface by a vapor deposition method.

At this time, the first in the piezoelectric element block 53
Conductive material 52a, second conductive material 52b (see FIG. 6)
And the like, respectively, on the piezoelectric element block wall surface 56, the electrode 5
5 can be conducted.

Further, as shown in FIG. 8, the piezoelectric element block 53 and a part of the substrate 11 are cut by a cutting tool such as a diamond cutter. As a result, a groove 57 is formed, and the piezoelectric element block 53 and the electrode 55 are divided.

Next, a lid 14 made of glass having the ink supply port 13 formed thereon is adhered to the piezoelectric element,
A plurality of pressure chambers 15 can be formed.

The manufacturing method for forming the structure of the ink jet head according to the first embodiment of the present invention has been described above, but the present invention is not limited to this manufacturing method.

For example, the substrate 11 is not limited to glass, but may be ceramic, plastic, or the like. Also the lid 14
Is not glass, but may be ceramic, plastic, or metal. In this embodiment, a piezoelectric ceramic is used as the plate-shaped piezoelectric material. However, an organic polymer piezoelectric film may be used.

In the present embodiment, no electrodes were formed on the bonding surface between the piezoelectric element and the substrate and between the piezoelectric element and the lid. However, a conductive material was applied to the surface of the piezoelectric block 53 where the substrate 11 and the lid 14 were in contact with each other. By forming, it is also possible to drive the plate-shaped piezoelectric material adjacent to the substrate and the lid.

Further, the method of taking out the electrodes is not limited to the embodiment. For example, a vacuum deposition method was used to form the collector, but a conductive coating may be applied to the end face of the piezoelectric element. A flexible wiring board may be directly connected from the collector electrode on the element.

[Embodiment 2] FIG. 9 is an exploded perspective view showing a part of the structure of an ink jet head according to a second embodiment of the present invention.

As shown in FIG. 9, an ink supply port 13 is formed in each of a plurality of depressions formed by arranging a plurality of partitions 10 having the same configuration as that described in the first embodiment on a substrate 11. Then, the independent lid 60 is bonded to form the pressure chamber 15.

The same first and second collector electrodes 91a and 91b as those described in the first embodiment are formed on the end face of the partition 10, and are electrically connected to the first and second drive electrodes 92a and 92b, respectively. Connection is established.

The first drive electrode 92a and the second drive electrode 9
2b, a voltage is applied between the cover 6
0 is displaced to the substrate 11 side. At this time, each lid 6
Since 0s are independent of each other, they do not cause any mechanical interference with each other.

With the configuration shown in FIG. 9, the individual pressure chambers 15 are completely independent. Therefore, the interference between the pressure chambers 15 is completely eliminated. Therefore, it is possible to provide an ink jet head having a constant ejection characteristic regardless of the printing mode.

The lid 60 is made of plastic, ceramic, metal or the like. If the lid 60 is lightweight and has high elasticity, the member in which the partition wall 10 and the lid 14 are connected has an ink jet having a high natural frequency and a high-speed continuous response. The head is obtained.

Embodiment 3 FIG. 10 is a sectional view showing the structure of an ink jet head according to a third embodiment of the present invention.

As shown in FIG. 7, a coating film 70 formed by a chemical vapor deposition method using a polyparaxylene resin is provided on the inner surface of the partition wall 10 forming the pressure chamber 15. The coating film 70 has a high electrical insulation property, and the conductive materials 71 a and 7 serving as electrodes in contact with the pressure chamber 15.
1b, 71c and the like can be electrically insulated from the pressure chamber 15 filled with ink.

Further, according to the structure of the present invention shown in FIG. 10, the conductive materials 71a, 71b, 71c, etc., which are the electrodes for driving the respective plate-like piezoelectric materials, form the wall surface 72 of the pressure chamber at the end face. For this reason, there is no problem of an insulating film defect occurring in the pores on the surface of the plate-shaped piezoelectric material.

Further, in the configuration shown in FIG. 10, the driving electrodes formed of the conductive materials 71a, 71b, 71c, etc. do not contact the ink. For this reason, a drive electrode is not corroded or a gas is not generated due to a chemical change of the ink, and an ink jet head that can be used with either a water-based ink or an oil-based ink (non-aqueous) ink is obtained.

In the third embodiment of the present invention described with reference to FIG. 10, a configuration using a coating film 70 using a polyparaxylene resin is shown. However, the present invention is not limited to this configuration. For example, the conductive materials 71a, 71b, 71c, etc.
5 is printed so as not to come out of the wall forming the pressure chamber 5, and then the piezoelectric element is pressure-sintered to form a partition wall 10 forming the pressure chamber 15.
It is also possible to adopt a configuration in which the electrode is not exposed on the wall surface of.

Fourth Embodiment FIG. 11 is a perspective view, partly in section, showing the structure of an ink jet head according to a fourth embodiment of the present invention.

As shown in FIG. 11, a partition 10 having the same structure as that described in the first embodiment is provided on a substrate 11 provided with an ink ejection port 12 for ejecting ink. Arrange and adhere in a matrix to correspond to one.

Further, the plurality of depressions formed on the substrate 11 are respectively covered with the lids 14 provided with the ink supply ports 13, and the plurality of pressure chambers 15 are formed in a matrix.
As shown in FIG. 11, the partition walls 10 are arranged on the substrate 11 with an interval dimension P in the X-axis direction and an interval dimension R in the Y-axis direction.

When a voltage is applied to the partition wall 10 made of a piezoelectric material,
Pressure is generated in the pressure chamber 15 filled with ink, and ink droplets 17 are ejected from the ink ejection ports 12 arranged on the pressure chamber 15. Since the interval dimension P and the interval dimension R are small, ink can be ejected in a planar manner from the plane of the small substrate 11. Although not shown in FIG. 11, the ink is supplied from a common ink reservoir of the ink cartridge connected to the ink supply port 13.

Although the wiring pattern is not shown in FIG. 11, the wiring is patterned on the back side of the substrate 11 so that each pressure chamber 15 can be driven from the outside.

The principle of operation of the configuration shown in FIG. 11 is the same as that of the first embodiment, and an ink jet head having a high ejection force and good ink continuous ejection characteristics can be obtained by the effect of laminating the plate-like piezoelectric material.

The manufacturing method is the same as that of the first embodiment. A piezoelectric element having a hollow portion formed in a matrix is attached to a substrate and cut to form an ink jet head shown in FIG.

In the structure of the ink jet head shown in FIG.
Since a, 80b, 80c, and 80d are formed and a large number of ink ejection ports 12 can be formed on a plane, it is possible to increase the number of nozzles.

As described in the first embodiment of the present invention,
This is due to the characteristic configuration of the present invention that a small pressure chamber can be formed and a large number of independent pressure chambers can be formed on a surface.

Further, the positions of the ink ejection ports 12 in the rows 80a and 80b of the adjacent ink ejection ports are deviated by the dimension Q with respect to the axis orthogonal to the rows. In this way, the pitch dimension determined by the limit at which the partition walls 10 can be arranged on the substrate 11 is equal to the rows 80a and 80b of the ink ejection ports 12.
It is possible to increase the density by the number. In the figure, since the number of rows is four, if the arrangement interval of the partition walls 10 is P as shown in FIG. 11, the pitch size of the ink ejection ports can be increased by Q = P / 4.

[0081]

As is apparent from the above description, according to the present invention, since the piezoelectric plates are laminated, the amount of deformation of the piezoelectric element can be made sufficiently large. For this reason, an ejection force is high and a small pressure chamber can be formed, so that there is an effect that a high-density and small inkjet head can be obtained.

Further, a part of the pressure chamber is formed by the piezoelectric element, and the entire pressure chamber is constituted by a hard wall. Therefore, there is an effect that an ink jet head having a high response frequency and a high continuous response speed can be obtained.

Further, the partition also functions as a drive actuator. For this reason, the number of parts is small and the configuration is simple, so that there is an effect that an easy-to-manufacture and inexpensive inkjet head can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a part of the configuration of the ink jet head according to the first embodiment of the present invention, which is cut away.

FIG. 3 is a sectional view showing another embodiment of the structure of the ink jet head according to the embodiment of the present invention.

FIG. 4 is an exploded perspective view showing another embodiment of the structure of the partition of the ink jet head according to the embodiment of the present invention.

FIG. 5 is a perspective view illustrating a manufacturing method for forming the structure of the piezoelectric element of the inkjet head according to the first embodiment of the present invention.

FIG. 6 is a perspective view showing a manufacturing method for forming the structure of the piezoelectric element of the inkjet head according to the first embodiment of the present invention.

FIG. 7 is a perspective view showing a manufacturing method for forming the structure of the piezoelectric element of the ink jet head according to the first embodiment of the present invention.

FIG. 8 is a perspective view showing a manufacturing method for forming the structure of the piezoelectric element of the inkjet head according to the first embodiment of the present invention.

FIG. 9 is an exploded perspective view showing a part of the configuration of an ink jet head according to a second embodiment of the present invention, which is cut away.

FIG. 10 is a cross-sectional view illustrating a configuration of an inkjet head according to a third embodiment of the present invention.

FIG. 11 is a perspective view illustrating a configuration of an inkjet head according to a fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating a configuration of an inkjet head in a conventional example.

FIG. 13 is a cross-sectional view illustrating a configuration of a conventional inkjet head.

[Explanation of symbols]

 1a First plate-shaped piezoelectric material 1b Second plate-shaped piezoelectric material 1c Third plate-shaped piezoelectric material 2a First conductive material 2b Second conductive material 10 Partition wall 11 Substrate 12 Ink ejection port 13 Ink supply port 14 Cover 15 Pressure chamber 17 Ink droplet

Claims (5)

(57) [Claims] A step of forming a piezoelectric element block by laminating a plurality of plate-shaped piezoelectric materials having a hollow portion serving as a pressure chamber and polarized in a thickness direction via a conductive material ; Put the piezoelectric element block on the formed substrate
Joined, the piezoelectric element block of the substrate is joined
Electrodes on the unexposed surface and the wall surface of the piezoelectric element block.
Forming and forming a groove in the piezoelectric element block and the substrate
And a lid having an ink supply port formed thereon is connected to the piezoelectric element block.
A method of manufacturing an ink jet head, characterized by a step of coupling. 2. A method according to claim 1, wherein a plurality of pressure chambers are provided.
The method according to claim 1, wherein the lid is joined . 3. A coating film is formed on a partition of said pressure chamber.
2. The method for manufacturing an ink jet head according to claim 1, wherein the method is performed . 4. The coating film according to claim 1, wherein said coating film is polyparaxylylene.
4. The ink jet according to claim 3, wherein
Head manufacturing method. 5. A method of manufacturing an ink jet head according to claim 1, wherein <br/> be tied to drive electrodes on the electrode of the substrate.