JP6350904B2

JP6350904B2 - Electromechanical conversion member, droplet discharge head, image forming apparatus, and electromechanical conversion element polarization processing method

Info

Publication number: JP6350904B2
Application number: JP2014105419A
Authority: JP
Inventors: 智水上
Original assignee: 株式会社リコー
Priority date: 2014-05-21
Filing date: 2014-05-21
Publication date: 2018-07-04
Anticipated expiration: 2034-05-21
Also published as: JP2015220433A

Description

The present invention relates to an electromechanical conversion member, a droplet discharge head that discharges droplets using the electromechanical conversion member, an image forming apparatus including the droplet discharge head, and a polarization processing method for an electromechanical conversion element used in the electromechanical conversion member It is about.

In general, printers, facsimiles, copiers, plotters, or image forming apparatuses that combine a plurality of these functions include, for example, an ink jet recording apparatus that includes a droplet discharge head that discharges droplets of ink or the like.

As the droplet discharge head, a nozzle that discharges a droplet of liquid such as ink, a liquid chamber (also referred to as a pressure chamber, a pressure chamber, a discharge chamber, or the like) that communicates with the nozzle and stores a liquid, A structure having an electromechanical conversion member provided with a piezoelectric element as an electromechanical conversion element for pressurizing a liquid in a liquid chamber is known. In this droplet discharge head, when a voltage is applied to the piezoelectric element, it vibrates so as to deform a diaphragm that forms part of the wall of the liquid chamber, and the liquid in the liquid chamber is applied by the deformation of the diaphragm. The liquid droplets can be discharged from the nozzle. A droplet discharge head using a piezoelectric actuator of a flexural vibration mode of a piezoelectric element has been put into practical use.

A piezoelectric element used in a piezoelectric actuator in a flexural vibration mode includes a first drive electrode, a piezoelectric film, and a second drive electrode. A diaphragm and a piezoelectric element are laminated on a substrate forming a liquid chamber, and further, an insulating film, wiring for connecting the first and second drive electrodes to the outside, and terminal electrodes are formed on the piezoelectric element. doing. Further, a holding substrate that covers the piezoelectric element is bonded to the surface of the substrate on which the piezoelectric element is formed so as not to prevent displacement of the piezoelectric element (see Patent Document 1).

The crystal of the piezoelectric film constituting the piezoelectric element has a random polarization direction as shown in FIG. 20A immediately after the piezoelectric element is manufactured. Thereafter, by repeating the voltage application, as shown in FIG. 20B, the crystal of the piezoelectric film becomes an aggregate of domains in which the directions of polarization are aligned. The direction of polarization of the crystal of the piezoelectric film is preferably aligned from the beginning of use of the droplet discharge head in order to stabilize the polarization characteristics of the piezoelectric element and the properties of the droplet discharge head using the piezoelectric element. .

Conventionally, there has been proposed a method of performing a polarization process for aligning the polarization direction of a piezoelectric element before the start of use of a droplet discharge head. For example, in Patent Documents 2 and 3, a piezoelectric element that performs a polarization process in which a piezoelectric element is applied with a polarization voltage larger than a driving voltage in actual use, and stabilizes the displacement of the piezoelectric element with respect to the driving voltage. A manufacturing method is disclosed. In Patent Document 4, a discharge electrode for generating corona discharge is disposed so as to face the surface of the piezoelectric film through a gap, and electric charges are supplied to the surface of the piezoelectric film by the corona discharge. A method of performing polarization treatment by generating an electric field in a film is disclosed.

However, in order to realize an appropriate polarization process of the piezoelectric element, it is necessary to stably form an appropriate electric field for polarization in the piezoelectric film by any method. That is, even when a voltage is applied to the piezoelectric element by directly contacting the probe card with the drive electrode constituting the piezoelectric element or the terminal electrode connected to the drive electrode, a polarization electric field is formed in the piezoelectric film. Even if the electric field for polarization is formed in the piezoelectric film by supplying the electric charge generated by the discharge, or the electric field for polarization is formed in the piezoelectric film by another method, it is suitable for the piezoelectric film. It is necessary to form a stable electric field.

In order to stably form an appropriate electric field in the piezoelectric film, one surface of the piezoelectric film (the surface on which either the first drive electrode or the second drive electrode is formed) is formed. It is effective to drop it to earth. However, if this ground is unstable, the electric field formed in the piezoelectric film tends to become unstable, and appropriate polarization processing is difficult. For this reason, it is insufficient to align the polarization directions of the piezoelectric elements, and it becomes difficult to obtain stable ink ejection characteristics.

Note that this problem is not limited to the electromechanical conversion member used in the droplet discharge head, and is a problem that occurs widely in general electromechanical conversion members.

In order to solve the above-described problem, the present invention provides an electromechanical transducer provided on a substrate, a first terminal electrode connected to a first drive electrode on the substrate side of the electromechanical transducer, A second terminal electrode connected to a second drive electrode opposite to the substrate of the electromechanical conversion element; and a holding substrate provided on the substrate so as to displaceably cover the electromechanical conversion element. In the electromechanical conversion member provided, the electromechanical conversion element is connected to the grounding terminal electrode which is one of the first terminal electrode and the second terminal electrode, or After the charge transfer portion connected to the ground terminal electrode is formed on the holding substrate, the first terminal electrode and the second terminal electrode are connected to the holding substrate or the charge transfer portion while being connected to the ground. The other is for charge supply Supplying a charge to the child electrodes, the Der those polarized by an electric field between the first driving electrode and the second driving electrodes is, the charge transfer part, the said holding substrate A conductive film formed on a surface opposite to the substrate, wherein the electromechanical conversion element is subjected to the polarization treatment in a state where the charge transfer portion and the ground terminal electrode are connected by wire bonding. and wherein the der Rukoto.

According to the present invention, an excellent effect is provided that an electromechanical conversion member using an electromechanical conversion element having good polarization characteristics can be provided.

FIG. 3 is a schematic configuration diagram illustrating a configuration example of a droplet discharge unit that is a basic component of the droplet discharge head according to the embodiment. FIG. 2 is a cross-sectional view of a row in which a plurality of droplet discharge units in FIG. 1 are arranged. It is sectional drawing which shows an example of the layer structure of the diaphragm on a board | substrate, and a piezoelectric element. FIG. 5 is a more detailed transmission plan view around the piezoelectric element of the liquid droplet ejection head according to the embodiment. 5A and 5B are cross-sectional views around the piezoelectric element of the droplet discharge head according to the embodiment, in which FIG. 4A shows a cross section 1 in FIG. 4 and FIG. It is explanatory drawing which shows typically the mode of the electric charge provision by discharge processing. It is an equivalent circuit diagram which shows the principle of the polarization of a piezoelectric element. (A) And (b) is a characteristic view which shows the example of a measurement of the PE hysteresis loop characteristic of the piezoelectric element before polarization processing and after polarization processing, respectively. It is an external view of a polarization processing apparatus. It is explanatory drawing of the wiring of a polarization processing apparatus. 11 is a cross-sectional view taken along line A-A ′ in FIG. 9. 6 is a more detailed transmission plan view of the periphery of a piezoelectric element of a droplet discharge head according to Modification 1. FIG. It is sectional drawing of the piezoelectric element periphery of the droplet discharge head which concerns on the modification 1, (a) shows the cross section 1 in FIG. 12, (b) shows the cross section 2 in FIG. FIG. 10 is a more detailed transmission plan view around the piezoelectric element of a droplet discharge head according to another example. It is sectional drawing of the piezoelectric element periphery of the droplet discharge head which concerns on the said other example, (a) shows the cross section 1 in FIG. 14, (b) shows the cross section 2 in FIG. FIG. 10 is a more detailed transmission plan view of the periphery of a piezoelectric element of a droplet discharge head according to Modification 2. FIG. 17 is a cross-sectional view of the periphery of a piezoelectric element of a droplet discharge head according to Modification 2, where (a) shows cross-section 1 in FIG. 16 and (b) shows cross-section 2 in FIG. 1 is a perspective view illustrating a configuration example of an inkjet recording apparatus including a droplet discharge head according to an embodiment. FIG. 2 is a side view illustrating a configuration example of a mechanism unit of an ink jet recording apparatus including the droplet discharge head according to the embodiment. (A) is explanatory drawing which shows the mode of the domain of the piezoelectric film before polarization processing. (B) is explanatory drawing which shows the mode of the domain of the piezoelectric film after polarization processing. It is a graph which shows the PE hysteresis loop characteristic of a piezoelectric element before polarization processing, after polarization processing, and after thermal history, respectively.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the basic configuration of the droplet discharge head according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a configuration example of a droplet discharge unit 10 which is a basic component of the droplet discharge head according to the present embodiment.

In FIG. 1, a droplet discharge unit 10 includes a nozzle plate 12 having nozzles 11 for discharging liquid droplets of liquid such as ink, and a liquid chamber substrate 14 that forms a liquid chamber 13 that communicates with the nozzles 11 and stores liquid. Hereinafter, it is simply referred to as “substrate”). Furthermore, on the substrate 14, a vibration plate 15 and a piezoelectric element 16 as an electromechanical conversion element for pressurizing the liquid in the liquid chamber 13 via the vibration plate 15 are provided. The piezoelectric element 16 includes a common electrode (lower electrode) 161 serving as a first drive electrode on the substrate 14 side, a piezoelectric film 162 such as PZT described later as an electromechanical conversion film, and the substrate 14 side of the piezoelectric film 162. Are stacked with an individual electrode (upper electrode) 163 which is a second driving electrode on the opposite side. The common electrode 161 is connected to a common electrode pad which is a first terminal electrode for external connection described later. The individual electrode 163 is connected to an individual electrode pad which is a second terminal electrode for external connection described later.

In the droplet discharge unit 10 of FIG. 1, a driving voltage having a predetermined frequency and amplitude is applied between the common electrode 161 and the individual electrode 163 of the piezoelectric element 16 via the common electrode pad and the individual electrode pad. The piezoelectric element 16 to which the drive voltage is applied vibrates so as to deform the diaphragm 15 between the substrate 14 and the piezoelectric element 16. Due to the deformation of the vibration plate 15, the liquid in the liquid chamber 13 is pressurized and droplets can be discharged from the nozzle 11.

In FIG. 1, the droplet discharge unit 10 including one nozzle 11 has been described. However, in an actual droplet discharge head, a plurality of droplet discharge units 10 are arranged in a row as shown in FIG. 2. It has a configuration.

FIG. 3 is a cross-sectional view showing an example of the layer structure of the diaphragm and the piezoelectric element on the substrate.
FIG. 4 is a more detailed transmission plan view around the piezoelectric element 16.
5A and 5B are more detailed cross-sectional views around the piezoelectric element 16. FIG. 5A shows a cross-section 1 in FIG. 4, and FIG. 5B shows a cross-section 2 in FIG. FIG. 4 is a transmission plan view in a state of being transmitted through the holding substrate 26, and illustration of the first insulating protective film 18 and the second insulating protective film 23 is omitted.

A diaphragm 15 formed by film formation is disposed between the common electrode 161 of the piezoelectric element 16 and the substrate 14. The common electrode 161, the piezoelectric film 162, and the individual electrode 163 that constitute the piezoelectric element 16 are laminated so as to be in contact with the vibration plate 15. After the individual electrode 163 is formed, the piezoelectric film 162 and the individual electrode 163 are individualized by etching. After the piezoelectric element 16 is formed, a first insulating protective film 18 is formed. Further, a common electrode lead-out wiring 20 is formed as a first wiring member that connects the common electrode 161 and the common electrode pad 19 that is the first terminal electrode. In addition, an individual electrode lead-out wiring 22 is formed as a first wiring member that connects the individual electrode 163 and the individual electrode pad 21 that is the second terminal electrode. The first insulating protective film 18 electrically insulates between the common electrode 161 and the individual electrode lead-out wiring 22. Further, a contact hole 18 a which is an opening formed in the first insulating protective film 18 is formed between the common electrode 161 and the common electrode lead-out wiring 20 and between the individual electrode 163 and the individual electrode lead-out wiring 22. Connected through.

After the common electrode lead-out wiring 20 and the individual electrode lead-out wiring 22 are formed, a second insulating protective film 23 is formed so as to cover the whole. The second insulating protective film 23 is provided with a plurality of openings 23a, and the common electrode pad 19 and the individual electrode pads 21 are exposed. The composite laminated substrate including the substrate 14, the piezoelectric element 16, and various electrodes after the second insulating protective film 23 is formed is called an actuator substrate 25.

A holding substrate 26 as a structure provided so as to cover the piezoelectric element 16 in a non-contact state with the piezoelectric element 16 through a gap is bonded to the actuator substrate 25 with an adhesive. The holding substrate 26 is formed with a recess 26a for covering the piezoelectric element 16 through a gap at a portion where the piezoelectric element 16 is located. The holding substrate 26 has an opening 26d in which a piezoelectric element driving IC as a driving electric circuit element for applying a pulse driving voltage having a predetermined amplitude and frequency to the plurality of piezoelectric elements 16 is disposed. Yes. The individual electrode pad 21 is exposed in the opening 26d, and the piezoelectric element driving IC is electrically connected to the individual electrode pad 21 via a bump electrode or the like. Hereinafter, the opening 26d is referred to as an individual pad opening 26d. The holding substrate 26 has an opening (hereinafter referred to as “common pad opening”) 26 c from which the common electrode pad 19 is exposed.

In addition, although description was abbreviate | omitted about the liquid supply means, flow path, fluid resistance, etc. which comprise a droplet discharge head, the incidental equipment which can be provided in a droplet discharge head can be provided naturally.

Next, the polarization process of the piezoelectric element 16 performed after the holding substrate 26 is bonded to the actuator substrate 25 will be described.
In the polarization process of this embodiment, the corona discharge method or the glow discharge method is applied to the holding substrate 26 having the common pad opening 26c and the individual pad opening 26d from which the common electrode pad 19 and the individual electrode pad 21 are exposed. Discharge treatment is performed. By this discharge process, the individual electrode pad 21 is given a charge having a predetermined polarity (plus polarity in the present embodiment). In this embodiment, a discharge voltage is applied to the individual electrode pad 21 and a predetermined voltage is applied to the individual electrode 163 of the piezoelectric element 16. However, there is no particular limitation on a method for applying the predetermined voltage to the individual electrode 163. Absent. Therefore, for example, a method in which a contact member is brought into contact with the individual electrode pad 21 and a predetermined voltage is applied from the contact member to the individual electrode 163 of the piezoelectric element 16 via the individual electrode pad 21 may be used.

FIG. 6 is an explanatory view schematically showing the state of charge application by the discharge treatment.
FIG. 7 is an equivalent circuit diagram illustrating the principle of polarization of the piezoelectric element 16.
In FIG. 6, for example, when corona discharge is performed using the corona electrode 71, molecules in the atmosphere are ionized to generate cations and anions. Among the generated ions, positive ions are supplied to both the common electrode pad 19 and the individual electrode pad 21. The charge supplied to the individual electrode pad 21 flows into the individual electrode 163 as it is and is accumulated. On the other hand, most of the charge supplied to the common electrode pad 19 flows to the ground (GND) through the diaphragm 15 and the substrate 14 below the common electrode 161, but a part of the charge is accumulated in the common electrode 161. There is a risk.

In order to realize an appropriate polarization process, it is important to stably generate a large potential difference between the common electrode 161 and the individual electrode 163, and the electric charge accumulated in the common electrode 161 is an obstacle. Therefore, it is preferable that the common electrode 161 is securely connected to the ground, the electric charge supplied to the common electrode pad 19 is released to the ground, and the common electrode 161 is stably maintained at zero [V].

Therefore, in this embodiment, before performing the polarization process, as shown in FIG. 5B, the common electrode pad 19 and the upper surface (the surface opposite to the substrate 14) of the holding substrate 26 are bonded by wire bonding. Connect by. The wire bonding method is not particularly limited. For example, gold bumps 171b are formed on the common electrode pad 19 and the upper surface of the holding substrate 26 (the surface opposite to the substrate 14). Are bonded by a bonding wire 171a. Note that the connection method between the common electrode pad 19 and the upper surface of the holding substrate 26 (the surface opposite to the substrate 14) is not limited to wire bonding.

The holding substrate 26 is connected to the ground during the polarization process of the present embodiment. The holding substrate 26 of the present embodiment has an electric resistance value that allows the electric charge supplied to the common electrode pad 19 to flow to the ground more easily than the route of flowing the electric charge to the ground via the diaphragm 15 and the substrate 14 below the common electrode 161. Is set to The holding substrate 26 of the present embodiment only needs to have such a conductivity as to have such an electric resistance value. For example, a substrate obtained by processing Si can be used. According to this embodiment, the electric charge accumulated in the common electrode 161 can be released from the holding substrate 26 to the ground, and the common electrode 161 can be stably dropped to the ground.

Here, the state of the polarization treatment of the piezoelectric film 162 can be determined from the PE hysteresis loop characteristics of the piezoelectric element.
FIGS. 8A and 8B are graphs showing measurement examples of the PE hysteresis loop characteristics of the piezoelectric elements before and after the polarization treatment, respectively.
As shown in FIG. 8, a hysteresis loop is measured with an electric field strength of ± 150 [kV / cm]. The first polarization at 0 [kV / cm] is Pini, and after applying a voltage of +150 [kV / cm], the polarization at 0 [kV / cm] when returning to 0 [kV / cm] is Pr. Then, the value of Pr−Pini is defined as a polarization amount difference. Whether the polarization state is good or bad can be determined from this polarization amount difference (Pr-Pini).

For example, the polarization amount difference (Pr−Pini) is preferably 10 [μC / cm ² ] or less, and as shown in FIG. 8B, it is 5 [μC / cm ² ] or less. Further preferred. On the other hand, when the value of the polarization difference (Pr−Pini) is larger than 10 [μC / cm ² ] as shown in FIG. 8A, the displacement deterioration after continuous driving as a piezoelectric actuator composed of a piezoelectric element. However, sufficient characteristics cannot be obtained.

By adjusting the corona electrode voltage, the grid electrode voltage, the sample stage, the distance between the corona electrode and the grid electrode, etc., it is possible to obtain a desired polarization difference (Pr-Pini). However, in order to obtain a desired polarization difference (Pr−Pini), it is usually necessary to generate a high electric field between the electrodes of the piezoelectric element. In order to generate such a high electric field, it is important to efficiently supply electric charges due to discharge to the individual electrodes of the piezoelectric element. Specifically, if the amount of leakage current is large when the current between the individual electrodes or the current between the common electrode and the individual electrode is measured, a high electric field cannot be generated between the electrodes of the piezoelectric element, and the polarization It has been found that processing does not proceed.

The amount of leakage current between individual electrodes or between an individual electrode and a common electrode should be 1.0 × 10 ⁻⁸ [A] or less when a voltage of 50 [V] is applied between the electrodes of the piezoelectric element. For example, a high electric field can be generated between the electrodes of the piezoelectric element. More preferably, it is 8.0 × 10 ⁻¹⁰ [A] or less.

Next, an example of the configuration of a polarization processing apparatus that performs polarization processing will be described with reference to FIGS.
FIG. 9 shows an external view of the polarization processing apparatus, and FIG. 10 is an explanatory diagram of wiring of the polarization processing apparatus. FIG. 11 is a sectional view taken along line AA ′ in FIG.
This polarization processing apparatus includes a corona electrode 71 and a grid electrode 73. The corona electrode 71 and the grid electrode 73 are connected to a corona electrode power source 72 and a grid electrode power source 74, respectively. At this time, as shown in FIG. 10, the other terminal not connected to the electrodes of the corona electrode power source 72 and the grid electrode power source 74 can be connected to the sample stage 75 where the sample is placed, for example. it can. Further, when the ground wire 76 is connected to the sample stage 75 as described later, it can be connected to the ground wire 76.

The configuration of the corona electrode 71 is not particularly limited. For example, the corona electrode 71 can have a wire shape as shown in the figure, and can be formed of various conductive materials.
The grid electrode 73 is disposed between the corona electrode 71 and the sample stage 75. The configuration of the grid electrode 73 is not particularly limited. For example, when the mesh process is performed and a high voltage is applied to the corona electrode 71, the sample stage that efficiently lowers ions, charges, and the like generated by corona discharge. It is preferable to be configured to pour down to 75.

A heating mechanism is added to the sample stage 75 so that the piezoelectric element 16 can be heated. The specific means of the heating mechanism for heating the piezoelectric element 16 is not particularly limited, and can be configured to heat using various heaters, lamps and the like. Further, the heating mechanism can be installed in the sample stage 75 or can be installed so as to heat from the outside of the sample stage 75. In particular, in order to avoid interference with an electrode or the like, it is preferably installed in the sample stage 75.

A configuration example when a heating mechanism is installed in the sample stage 75 will be described with reference to FIG. In addition, as above-mentioned, it is not limited to the following structures.
As shown in FIG. 11A, the sample stage 75 includes a sample holding groove 751 formed in accordance with the sample shape and a heating mechanism 753 including a heating wire in the sample holding portion 752. It can be. In addition, as will be described later, a ground wire 76 may be provided on the sample stage 75. The above structure is preferable because the sample is particularly easily heated by the heating mechanism 753 uniformly. In particular, from the viewpoint of heating the sample uniformly, the sample holder 752 is preferably made of a metal, and for example, stainless steel or Inconel can be used more preferably. Inconel can be used particularly preferably from the viewpoint of heating the sample uniformly.

As another configuration example, as illustrated in FIG. 11B, the sample stage 75 may be divided into a sample holding unit 752 and a heating mechanism holding unit 754. In this case, a sample holding groove 751 can be formed in the sample holding portion 752. Further, the heating mechanism holding portion 754 can have a heating mechanism 753 made of a heating wire or the like. In this case, the sample holding part 752 is preferably made of a metal in order to improve heat transfer, for example, stainless steel or Inconel can be used more preferably, and Inconel is particularly preferable from the viewpoint of heating uniformly. Can be used. In the configuration shown in FIG. 11B, the sample holding unit 752 and the heating mechanism holding unit 754 can be simply stacked, or both can be fixed with an adhesive or a fixture. You can also.

In FIGS. 11A and 11B, a configuration in which a sample holding groove 751 is provided is described as an example. However, the groove is not provided, and a sample is placed at an arbitrary location on the sample holding portion 752. You may comprise so that it may install.
The maximum heating temperature of the heating mechanism is not particularly limited as long as the heating mechanism can be heated to a predetermined temperature according to the Curie temperature of the piezoelectric film 162 of the piezoelectric element 16 to be manufactured. In particular, it is preferable to be configured to be able to heat up to 350 ° C. so as to be compatible with various piezoelectric elements.
Moreover, it is preferable that the sample stage 75 on which the sample is placed is grounded (grounded) so that charges from the sample arranged on the sample stage can easily flow. That is, the ground wire 76 is preferably connected to the sample stage 75.
The magnitude of the voltage applied to the corona electrode and grid electrode, and the distance between the sample and each electrode are not particularly limited, and these are adjusted so that sufficient polarization treatment can be performed, and the strength of the corona discharge can be adjusted. You can turn it on.

In addition, the sample stage 75 has a moving mechanism (not shown) capable of moving the sample so that the entire sample can be processed because the area to which the sample is irradiated (supplied) with a corona discharge is limited. Has been. The moving means is not particularly limited.

In addition, the amount of charge Q required for performing the polarization treatment is not particularly limited, but it is preferable that a charge amount of 1.0 × 10 ⁻⁸ [C] or more is accumulated in the electromechanical transducer. More preferably, a charge amount of 4.0 × 10 ⁻⁸ [C] or more is accumulated. By accumulating the charge amount in such a range in the piezoelectric element 16, it is possible to perform a favorable polarization process so as to have the polarization amount difference more reliably.

Here, in the polarization processing method described in Patent Document 4, it is necessary to perform the polarization processing with the surface of the piezoelectric film 162 exposed. Therefore, a step of forming the first insulating protective film 18, the common electrode lead-out wiring 20, the individual electrode lead-out wiring 22, the second insulating protective film 23, etc., accompanied by high-temperature heat treatment, on the piezoelectric element subjected to the polarization treatment Will be implemented. Furthermore, the process of joining the holding substrate 26 with an adhesive accompanied by heat treatment at 100 to 200 ° C. is also performed. For this reason, there is a possibility that the piezoelectric element is depolarized due to the influence of a thermal history or the like in a subsequent process after the polarization process, and the characteristics of the electromechanical conversion ability are returned to the state before the polarization process.

In the present embodiment, the actuator substrate 25 is formed through the steps of forming the first insulating protective film 18, the common electrode lead-out wiring 20, the individual electrode lead-out wiring 22, the second insulating protective film 23, and the like, and the actuator substrate 25. By performing the polarization process at a stage close to the final process after bonding the holding substrate 26 to the substrate, it is possible to prevent depolarization due to the influence of the thermal history in the subsequent process. Specifically, the polarization process is performed according to the following procedure.

After the holding substrate 26 is bonded to the actuator substrate 25, gold bumps 171 b are respectively formed on the common electrode pad 19 exposed from the common pad opening 26 c of the holding substrate 26 and the upper surface of the holding substrate 26. Then, after these are bonded with a bonding wire, the corona electrode 71 of the polarization device described above is made to face the surface of the holding substrate 26 on which the individual pad openings 26d are formed. Then, the corona electrode 71 performs a discharge process toward the individual pad opening 26 d where the individual electrode pad 21 is exposed, and supplies electric charges to the individual electrode pad 21.

The corona electrode 71 of the polarization device is preferably arranged to face the individual electrode pad 21 exposed from the individual pad opening 26d of the holding substrate 26. This is because by arranging in this way, charges can be efficiently applied to the individual electrode pads 21 to be charged. Needless to say, the corona electrode 71 may be arranged in any manner as long as the charge generated by the corona electrode 71 can be applied to the charge application target without arranging the corona electrode 71 to face the charge application target (individual electrode pad 21). In addition, the longitudinal direction of the corona electrode 71 may be parallel to or inclined with respect to the arrangement direction of the individual electrode pads 21 (nozzle arrangement direction), or may be an orthogonal direction.

At this time, charges are also supplied to the common electrode pad 19 through the common pad opening 26c, but the charges supplied to the common electrode pad 19 are transferred from the bonding wire to the ground through the holding substrate 26. Flowing. As a result, the positive electrode charge due to the discharge process is accumulated in the individual electrode 163 of the piezoelectric element 16, while the common electrode 161 of the piezoelectric element 16 is stably grounded, resulting in a large potential difference in the piezoelectric element 16. It can be generated stably. Therefore, the piezoelectric element 16 having good polarization characteristics can be manufactured, and stable ink ejection performance can be realized.

[Modification 1]
Next, a modification of the configuration for polarization processing in the present embodiment (hereinafter, this modification is referred to as “modification 1”) will be described.
In the above-described embodiment, the charge transfer unit connected to the ground is the main body of the holding substrate 26. However, in the first modification, the charge transfer unit connected to the ground is the main body of the holding substrate 26. It is an example formed separately.

FIG. 12 is a more detailed transmission plan view around the piezoelectric element 16 in the first modification.
FIGS. 13A and 13B are more detailed cross-sectional views around the piezoelectric element 16 in the first modification. FIG. 13A shows a cross-section 1 in FIG. 12, and FIG. 13B shows a cross-section 2 in FIG. ing.
In the first modification, an insulating film 27 a is formed on the upper surface of the holding substrate 26 so as to cover the entire surface. For example, a material such as SiO ₂ , SiN, or Al ₂ O ₃ can be used as the material of the insulating film 27a. In the first modification, the conductive film 27b is formed on the insulating film 27a so as to surround the periphery of the common pad opening 26c exposing the common electrode pad 19. As a material of the conductive film 27b, for example, a metal electrode material such as an Ag alloy, Cu, Al, Au, Pt, or Ir can be used.

In the first modification, the conductive film 27b functions as a charge transfer portion, a gold bump 171b is formed on the conductive film 27b, and is connected to the gold bump 171b on the common electrode pad 19 by wire bonding. The conductive film 27b provided on the holding substrate 26 is connected to an external ground.

In the above-described embodiment, when the main body of the holding substrate 26 is used as the charge transfer unit, there is a limit to increase the conductivity of the holding substrate due to the nature of the holding substrate 26, and the common electrode 161 can be sufficiently dropped to the ground. difficult. On the other hand, as in Modification 1, by using a conductive film 27b different from the main body of the holding substrate 26 as the charge transfer unit, the common electrode 161 and the ground are not affected regardless of the nature of the holding substrate 26. It is easy to drop the common electrode 161 to the ground sufficiently.

Here, as shown in FIGS. 14 and 15, the conductive film 27 b as the charge transfer portion may be formed so as to cover the entire surface of the holding substrate 26, but in this case, the individual pad that exposes the individual electrode pad 21. The conductive film 27b is also formed on the periphery of the opening 26d for use. With such a configuration, the cations generated by the discharge during the polarization process are supplied to the conductive film 27b at the periphery of the individual pad opening 26d, and the cations are supplied to the individual electrode pads 21 in the individual pad opening 26d. It becomes difficult. For this reason, the amount of charge accumulated in the individual electrode 163 decreases, and the potential difference between the common electrode 161 and the individual electrode 163 becomes insufficient, which may make it difficult to perform sufficient polarization processing.

Therefore, in the first modification, as shown in FIGS. 12 and 13, the conductive film 27b is formed on the periphery of the common pad opening 26c, and the conductive film 27b is not formed on the periphery of the individual pad opening 26d. I am doing so. As a result, both reliable grounding of the common electrode 161 and sufficient charge supply to the individual electrode 163 are achieved. In particular, in the first modification, since the peripheral edge of the individual pad opening 26d is covered with the insulating film 27a, more stable charge supply to the individual electrode 163 is possible.

[Modification 2]
Next, another modified example of the configuration for polarization processing in the present embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
Also in the second modification, the main body of the holding substrate 26 is used as the charge transfer unit connected to the ground, but the peripheral edge of the individual pad opening 26d is covered with the insulating film 27a.

FIG. 16 is a more detailed transmission plan view around the piezoelectric element 16 in the second modification.
FIGS. 17A and 17B are more detailed cross-sectional views around the piezoelectric element 16 in the second modification, FIG. 17A shows a cross section 1 in FIG. 16, and FIG. 17B shows a cross section 2 in FIG. ing.
In the second modification, an insulating film 27a is formed on the upper surface of the holding substrate 26 so as to cover the entire surface, and the insulating film portion at the periphery of the common pad opening 26c is removed by etching or the like. For example, a material such as SiO ₂ , SiN, or Al ₂ O ₃ can be used as the material of the insulating film 27a. In the second modification, the main body of the holding substrate 26 is exposed at the peripheral edge of the common pad opening 26c, and a gold bump 171b is formed on the exposed portion, and is bonded to the gold bump 171b on the common electrode pad 19 by wire bonding. It is connected.

Also in the second modification, as in the first modification, sufficient charge supply to the individual electrode 163 can be realized. In particular, in the second modification, since the peripheral edge of the individual pad opening 26d is covered with the insulating film 27a, more stable charge supply to the individual electrode 163 is possible.

Next, materials and construction methods that constitute the droplet discharge head of the present embodiment will be specifically described.

[substrate]
As the substrate 14, it is preferable to use a silicon single crystal substrate, and it is preferable to have a thickness in the range of 100 [μm] to 600 [μm]. There are three types of plane orientations: (100), (110), and (111), but (100) and (111) are generally widely used in the semiconductor industry. In this configuration example, A single crystal substrate having a (100) plane orientation was mainly used. Further, when the liquid chamber (pressure chamber) 13 as shown in FIG. 1 is manufactured, the silicon single crystal substrate is processed using etching. As an etching method in this case, it is common to use anisotropic etching. Anisotropic etching utilizes the property that the etching rate differs with respect to the plane orientation of the crystal structure. For example, in anisotropic etching immersed in an alkaline solution such as KOH, the (111) plane has an etching rate of about 1/400 compared to the (100) plane. Therefore, while a structure having an inclination of about 54 ° can be produced in the plane orientation (100), a deep groove can be removed in the plane orientation (110), so that the arrangement density is increased while maintaining rigidity. I know you can. As this configuration example, it is possible to use a single crystal substrate having a (110) plane orientation. However, in this case, SiO ₂ which is a mask material is also etched, so it is preferable to use this point in consideration.

[Diaphragm]
As shown in FIG. 1, upon receiving the force generated by the piezoelectric element 16 as an electromechanical transducer, the underlying diaphragm 15 is deformed, and liquid droplets such as ink in the liquid chamber (pressure chamber) 13 are discharged. Discharge. Therefore, it is preferable that the diaphragm 15 has a predetermined strength. Examples of the material include materials made of Si, SiO ₂ , Si ₃ N _{4 and the} like by, for example, a CVD (Chemical Vapor Deposition) method. Furthermore, it is preferable to select a material close to the linear expansion coefficient of the common electrode 161 and the piezoelectric film 162 as shown in FIG. In particular, as a piezoelectric film, PZT described later is often used as a material in general. Therefore, the material of the diaphragm 15 is in the range of 5 × 10 ⁻⁶ (1 / K) to 10 × 10 ⁻⁶ (1 / K), which is close to the linear expansion coefficient 8 × 10 ⁻⁶ (1 / K) of PZT. A material having a linear expansion coefficient is preferably 7 × 10 ⁻⁶ (1 / K) or more and 9 × 10 ⁻⁶ (1 / K) or less. Specific examples of the material include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof. These materials can be produced by a spin coater using, for example, a sputtering method or a sol-gel method. The film thickness is preferably in the range of 0.1 [μm] to 10 [μm], and more preferably in the range of 0.5 [μm] to 3 [μm]. If it is smaller than this range, it becomes difficult to process the liquid chamber (pressure chamber) 13 as shown in FIG. On the other hand, if it is larger than the above range, the diaphragm 15 is difficult to deform, and the ejection of droplets such as ink droplets becomes unstable.

[Common electrode (lower electrode)]
The common electrode (lower electrode) 161 is preferably made of metal or a metal and an oxide. Here, both materials are devised so as to suppress peeling and the like by inserting an adhesion layer between the diaphragm 15 and the metal film constituting the common electrode 161. Details of the metal electrode film and the oxide electrode film including the adhesion layer are described below.

[Adhesion layer]
The adhesion layer is formed as follows, for example. After Ti is formed by sputtering, the formed titanium film is thermally oxidized using an RTA (Rapid Thermal Annealing) apparatus to form a titanium oxide film. The conditions for thermal oxidation are, for example, a temperature in the range of 650 [° C.] to 800 [° C.], a treatment time in the range of 1 [min] to 30 [min], and an O ₂ atmosphere. To form the titanium oxide film, reactive sputtering may be used, but thermal oxidation of the titanium film at a high temperature is desirable. The production by reactive sputtering requires a special sputtering chamber configuration because the silicon substrate needs to be heated at a high temperature. Furthermore, the crystallinity of the titanium O ₂ film is better in the oxidation by the RTA apparatus than in the oxidation by a general furnace. This is because, according to oxidation in a normal heating furnace, a titanium film that is easily oxidized forms several crystal structures at a low temperature, and thus it is necessary to break it once. Therefore, oxidation by RTA having a high temperature rising rate is advantageous in order to form better crystals. Moreover, as materials other than Ti, materials such as Ta, Ir, and Ru can be used. The thickness of the adhesion layer is preferably in the range of 10 [nm] to 50 [nm], and more preferably in the range of 15 [nm] to 30 [nm]. If it is below this range, there is concern about the adhesion, and if it exceeds this range, the quality of the crystal of the electrode film produced on the adhesion layer will be affected.

[Metal electrode film]
Conventionally, platinum having high heat resistance and low reactivity has been used as the metal material of the metal electrode film, but it may not be said that it has sufficient barrier properties against lead. -Platinum group elements, such as rhodium, and these alloy films are also mentioned. Further, when platinum is used, it is preferable that the above-mentioned adhesion layer is laminated first because adhesion to the base (particularly SiO ₂ ) is poor. As a manufacturing method, vacuum film formation such as sputtering or vacuum deposition is generally used. The film thickness is preferably in the range of 80 [nm] to 200 [nm], and more preferably in the range of 100 [nm] to 150 [nm]. When the thickness is smaller than this range, a sufficient current cannot be supplied as the common electrode 161, and a problem occurs when ejecting droplets. Further, when the thickness is larger than this range, the cost increases when an expensive material of a platinum group element is used. In the case of using platinum as a material, the surface roughness increases when the film thickness is increased, which affects the surface roughness and crystal orientation of the oxide electrode film and PZT produced thereon. This causes a problem that sufficient displacement for ink ejection cannot be obtained.

[Oxide electrode film]
As a material for the oxide electrode film, strontium ruthenate (SrRuO ₃ , hereinafter, abbreviated as “SRO” as appropriate) is preferably used. A material in which a part of strontium ruthenate is substituted, specifically, Sr _x A _(1-x) Ru _y B _(1-y) O ₃ (where A is Ba, Ca, B is Co, Ni, The material represented by x, y = 0 to 0.5) can also be preferably used. The oxide electrode film can be produced by a film forming method such as sputtering. The film quality of the SrRuO ₃ thin film varies depending on the sputtering conditions. Accordingly, in order to place the SrRuO ₃ film in the (111) orientation in accordance with the common electrode Pt (111) with particular emphasis on the crystal orientation, it is necessary to heat the substrate at a deposition temperature of 500 [° C.] or higher. Preferably, the film is formed. For example, with respect to the SRO film formation conditions described in Patent Document 2, thermal oxidation is performed at room temperature film formation and then at a crystallization temperature (650 ° C.) by RTA treatment. In this case, the SRO film is sufficiently crystallized and a sufficient value is obtained as the specific resistance as an electrode. However, as the crystal orientation of the film, (110) is easily preferentially oriented, and the film is formed thereon. The (110) orientation of the deposited PZT is also facilitated.

[Piezoelectric film (electromechanical conversion film)]
PZT was mainly used as the material for the piezoelectric film 162. PZT is a solid solution of lead zirconate (PbTiO ₃ ) and titanic acid (PbTiO ₃ ), and the characteristics differ depending on the ratio. In general, the composition exhibiting excellent piezoelectric characteristics has a ratio of PbZrO ₃ and PbTiO ₃ of 53:47. When expressed by the chemical formula, Pb (Zr _0.53 , Ti _0.47 ) O ₃ , general PZT (53 / 47). Examples of composite oxides other than PZT include barium titanate. In this case, it is also possible to prepare a barium titanate precursor solution by dissolving barium alkoxide and a titanium alkoxide compound in a common solvent. is there. These materials are described by the general formula ABO ₃ , and A = Pb, Ba, Sr, B = Ti, Zr, Sn, Ni, Zn, Mg, and a composite oxide mainly composed of Nb. Specific descriptions thereof include (Pb _1-x , Ba _x ) (Zr, Ti) O ₃ , (Pb _1-x , Sr _x ) (Zr, Ti) O ₃ , and this is because part of Pb at the A site is Ba. This is the case where it is replaced with Sr. Such substitution is possible with a divalent element, and the effect thereof has an effect of reducing characteristic deterioration due to evaporation of lead during heat treatment.

As a method for manufacturing the piezoelectric film 162, it can be manufactured by a spin coater using a sputtering method or a sol-gel method. In that case, since patterning is required, a desired pattern is obtained by photolithography etching or the like. When PZT is produced by a sol-gel method, a PZT precursor solution can be produced by using lead acetate, zirconium alkoxide, and titanium alkoxide compounds as starting materials and dissolving them in methoxyethanol as a common solvent to obtain a uniform solution. Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of a stabilizer such as acetylacetone, acetic acid or diethanolamine may be added to the precursor solution as a stabilizer.

When the piezoelectric film (PZT film) 162 is obtained on the entire surface of the substrate 14, it is obtained by forming a coating film by a solution coating method such as spin coating and performing heat treatments such as solvent drying, thermal decomposition, and crystallization. Since the transformation from the coating film to the crystallized film involves volume shrinkage, it is necessary to adjust the precursor concentration so that a film thickness of 100 nm or less can be obtained in one step in order to obtain a crack-free film. Become.

The film thickness of the piezoelectric film 162 is preferably in the range of 0.5 [μm] to 5 [μm], and more preferably in the range of 1 [μm] to 2 [μm]. If it is smaller than this range, it will not be possible to generate sufficient deformation (displacement), and if it is larger than this range, many layers will be laminated, resulting in an increase in the number of steps and a longer process time.
The relative dielectric constant of the piezoelectric film 162 is preferably in the range of 600 to 2000, and more preferably in the range of 1200 to 1600. At this time, when it is smaller than this range, there is a problem that sufficient deformation (displacement) characteristics cannot be obtained. On the other hand, if it is larger than this range, the polarization process is not sufficiently performed, and there arises a problem that sufficient characteristics cannot be obtained for the displacement deterioration after continuous driving.

[Individual electrode (upper electrode)]
The individual electrode (upper electrode) 163 is preferably made of a metal or an oxide and a metal. Details of the oxide electrode film and the metal electrode film are described below.

[Oxide electrode film]
As for the material and the like of the oxide electrode film, the same materials as those described for the oxide electrode film used in the common electrode (lower electrode) 161 can be given. The thickness of the oxide electrode film (SRO film) is preferably in the range of 20 [nm] to 80 [nm], and more preferably in the range of 40 [nm] to 60 [nm]. If the thickness is less than this range, sufficient characteristics cannot be obtained for the deterioration characteristics of initial deformation (displacement) and deformation (displacement). In addition, if this range is exceeded, the dielectric breakdown voltage of the piezoelectric film (PZT film) 162 formed thereafter is very poor and leaks easily.

[Metal electrode film]
Examples of the material for the metal electrode film include the same materials as those described for the metal electrode film used in the common electrode (lower electrode) 161 described above. The film thickness is described as a metal electrode film, and the film thickness is preferably in the range of 30 [nm] to 200 [nm], and more preferably in the range of 50 [nm] to 120 [nm]. When the thickness is smaller than this range, a sufficient current cannot be supplied as the individual electrode 163, and a problem occurs when a droplet is ejected. On the other hand, if the thickness is larger than the above range, the cost increases when an expensive material of a platinum group element is used. In addition, when platinum is used as the material, the surface roughness increases when the film thickness is increased, and process defects such as film peeling are likely to occur when wiring is formed through an insulating protective film. .

[First insulating protective film]
Since it is necessary to select a material that prevents moisture in the atmosphere from permeating while preventing damage to the piezoelectric element due to the film formation / etching process, the material of the first insulating protective film 18 needs to be a dense inorganic material. There is. Further, when an organic material is used as the first insulating protective film 18, it is not suitable because it is necessary to increase the film thickness in order to obtain sufficient protection performance. If the first insulating protective film 18 is a thick film, the vibration of the diaphragm 15 is remarkably hindered, resulting in a droplet discharge head with low discharge performance. In order to obtain high protection performance with a thin film, it is preferable to use an oxide, nitride, or carbide film. However, the electrode material, the piezoelectric film material, and the diaphragm material serving as the base of the first insulating protective film 18 have adhesiveness. It is necessary to select a high material. In addition, it is necessary to select a film forming method that does not damage the piezoelectric element 16 as a method for forming the first insulating protective film 18. That is, a plasma CVD method in which a reactive gas is turned into plasma and deposited on a substrate, or a sputtering method in which a film is formed by causing a plasma to collide with a target material and flying away is not preferable. Examples of a preferable film formation method for the first insulating protective film 18 include an evaporation method and an ALD (Atomic Layer Deposition) method, but an ALD method with a wide range of materials that can be used is preferable. As a preferable material, an oxide film used for a ceramic material such as Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , Ta ₂ O ₃ , TiO ₂ is exemplified. In particular, by using the ALD method, a thin film having a very high film density can be produced and damage in the process can be suppressed.

The film thickness of the first insulating protective film 18 needs to be a thin film enough to ensure the protection performance of the piezoelectric element 16 and at the same time as thin as possible so as not to inhibit the deformation (displacement) of the diaphragm 15. There is a need. The film thickness of the first insulating protective film 18 is preferably in the range of 20 [nm] to 100 [nm]. When the thickness is greater than 100 [nm], the deformation (displacement) amount of the vibration plate 15 is reduced, so that a droplet discharge head with low discharge efficiency is obtained. On the other hand, when the thickness is smaller than 20 [nm], the function of the piezoelectric element 16 as a protective layer is insufficient, so that the performance of the piezoelectric element 16 is deteriorated as described above.

Further, a configuration in which the first insulating protective film 18 has two layers is also conceivable. In this case, in order to increase the thickness of the second insulating protective film, a structure in which the second insulating protective film is opened in the vicinity of the individual electrode (upper electrode) 163 so as not to significantly disturb the vibration of the diaphragm 15 is also possible. Can be mentioned. In this case, as the second insulating protective film, any oxide, nitride, carbide or a composite compound thereof can be used, and SiO ₂ generally used in semiconductor devices can also be used. . Arbitrary methods can be used for forming the two-layer first insulating protective film 18, and examples thereof include a CVD method and a sputtering method. It is preferable to use a CVD method capable of forming an isotropic film in consideration of the step coverage of the pattern forming portion such as the electrode forming portion. The film thickness of the second insulating protective film needs to be a film thickness that does not cause dielectric breakdown by a voltage applied between the common electrode (lower electrode) 161 and the individual electrode lead-out wiring 22. That is, it is necessary to set the electric field strength applied to the first insulating protective film 18 within a range not causing dielectric breakdown. Furthermore, in consideration of the surface property of the base of the first insulating protective film 18 and pinholes, the film thickness of the first insulating protective film 18 needs to be 200 [nm] or more, more preferably 500 [nm] or more. It is.

[wiring]
The material of the common electrode lead-out wiring 20 and the individual electrode lead-out wiring 22 is preferably a metal electrode material made of Ag alloy, Cu, Al, Au, Pt, or Ir. As a method for manufacturing these wirings, a sputtering method and a spin coating method are used, and then a desired pattern is obtained by photolithography etching or the like. The film thickness is preferably in the range of 0.1 [μm] to 20 [μm], and more preferably in the range of 0.2 [μm] to 10 [μm]. If it is smaller than this range, the resistance becomes large, and a sufficient current cannot flow through the electrodes, making the head ejection unstable. On the other hand, if it is larger than this range, the process time becomes longer. Further, the contact resistance in a contact hole (for example, 10 [μm] × 10 [μm]) connected to the common electrode 161 and the individual electrode 163 is 10 [Ω] or less with respect to the common electrode 161, On the other hand, 1 [Ω] or less is preferable. More preferably, it is 5 [Ω] or less for the common electrode 161 and 0.5 [Ω] or less for the individual electrode 163. If this range is exceeded, it will not be possible to supply a sufficient current, causing problems when discharging droplets.

Of the common electrode lead-out wiring 20, a portion exposed from the opening 23a of the second insulating protective film 23 becomes a common electrode pad 19 as a lower terminal electrode. In addition, in the individual electrode lead-out wiring 22, a portion exposed from the opening 23 a of the second insulating protective film 23 becomes an individual electrode pad 21 as an upper terminal electrode.

[Second insulating protective film]
The function as the second insulating protective film 23 is a passivation layer having a function as a protective layer for the individual electrode lead-out wiring 22 and the common electrode lead-out wiring 20. As described above, the second insulating protective film 23 is formed of the individual electrode lead-out wiring 22 and the common electrode except for the opening 23 a for forming the individual electrode pad 21 and the opening 23 a for forming the common electrode pad 19. The lead wiring 20 is covered. Thereby, an inexpensive Al or an alloy material containing Al as a main component can be used as the electrode material. As a result, a low-cost and highly reliable droplet discharge head (inkjet head) can be obtained. As a material of the second insulating protective film 23, any inorganic material or organic material can be used, but it is necessary to use a material with low moisture permeability. Examples of the inorganic material include oxides, nitrides, and carbides, and examples of the organic material include polyimide, acrylic resin, and urethane resin. However, an organic material is not suitable for patterning because it needs to be a thick film. Therefore, it is preferable to use an inorganic material that can exhibit a wiring protection function with a thin film. In particular, it is preferable to use Si ₃ N ₄ on the Al wiring because it is a proven technology for semiconductor devices. The film thickness is preferably 200 [nm] or more, and more preferably 500 [nm] or more. When the film thickness is thin, a sufficient passivation function cannot be exhibited, so that disconnection due to corrosion of the wiring material occurs, and the reliability of the ink jet is lowered.

Further, a structure having openings on the piezoelectric element 16 and the surrounding diaphragm 15 is preferable. This is the same reason that the region corresponding to the individual liquid chamber of the first insulating protective film 18 is thinned. As a result, a highly efficient and highly reliable droplet discharge head (inkjet head) can be obtained.

Since the piezoelectric element 16 is protected by the insulating protective films 18 and 23, the opening of the second insulating protective film 23 can be formed by photolithography and dry etching. In addition, the area of the individual electrode pad 21 and the common electrode pad 19 provided by the opening of the second insulating protective film 23 is preferably 50 × 50 [μm ² ] or more, and further 100 × 300 [ μm ² ] or more is preferable. When the value is less than this value, sufficient polarization processing cannot be performed, and there is a problem that sufficient characteristics cannot be obtained with respect to deformation (displacement) deterioration after continuous driving.

[Holding substrate]
Since the actuator substrate 25 in which the above-described members such as the piezoelectric elements 16 are formed on the substrate 14 has a thickness of 20 to 100 [μm], the holding substrate 26 is bonded to ensure the rigidity of the actuator substrate 25. Although any material can be used as the material of the holding substrate 26, it is necessary to select a material having a thermal expansion coefficient close to prevent the actuator substrate 25 from warping. Therefore, it is preferable to use ceramic materials such as glass, silicon, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ . The holding substrate 26 has a recess 26a for covering the piezoelectric element 16 with a gap, and an opening (not shown) that forms part of a common liquid supply path for supplying liquid to the plurality of liquid chambers 13. . Further, a common pad opening 26 c for exposing the common electrode pad 19 and an individual pad opening 26 d for exposing the individual electrode pad 21 are provided.

Next, more specific examples of the polarization process using the discharge in the manufacturing method of the droplet discharge head according to the present embodiment, and the results of the evaluation experiment on these examples will be described.

[Example 1]
In the first embodiment, a thermal oxide film (film thickness 1 [μm]) is formed on a 6-inch silicon wafer to be the substrate 14, and then the common electrode 161 is formed. The common electrode 161 is formed by forming a titanium film (film thickness 30 [nm]) as an adhesion film with a sputtering apparatus at a film formation temperature of 350 [° C.] and then thermally oxidizing at 750 [° C.] using RTA. did. Subsequently, after forming a platinum film (film thickness 100 [nm]) as a metal film with a sputtering apparatus at a film formation temperature of 550 [° C.], Ti is formed with a sputtering apparatus, and then using RTA. It processed at 750 [degreeC].

Next, a piezoelectric film (electromechanical conversion film) 162 is formed. The piezoelectric film 162 was formed by preparing a solution adjusted to Pb: Zr: Ti = 115: 49: 51 and forming the film by spin coating. Specifically, for the synthesis of the precursor coating solution, lead acetate trihydrate, isopropoxide titanium, and isopropoxide zirconium were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and then dehydrated. The lead amount is excessive with respect to the stoichiometric composition. This is to prevent crystallinity deterioration due to so-called lead loss during heat treatment. Isopropoxide titanium and isopropoxide zirconium were dissolved in methoxyethanol, the alcohol exchange reaction and the esterification reaction were advanced, and the PZT precursor solution was synthesized by mixing with the methoxyethanol solution in which the lead acetate was dissolved. The PZT concentration of this PZT precursor solution was 0.5 [mol / liter]. Using this PZT precursor solution, a film was formed by spin coating, and after the film formation, drying at 120 [° C.] and thermal decomposition at 500 [° C.] were performed. After thermal decomposition treatment of the third layer, crystallization heat treatment (temperature 750 [° C.]) was performed by RTA (rapid heat treatment). At this time, the film thickness of PZT was 240 [nm]. This process was performed a total of 8 times (24 layers) to obtain a PZT film thickness of about 2 [μm].

Next, the individual electrode 163 is formed. In order to form the individual electrode 163, first, an SrRuO film (film thickness 40 [nm]) as an oxide film and a Pt film (film thickness 125 [nm]) as a metal film are formed by sputtering. Thereafter, a photoresist made by Tokyo Ohka Co., Ltd. (TSMR8800) is formed by a spin coat method, a resist pattern is formed by a normal photolithography method, and then, using the ICP etching apparatus (manufactured by Samco), the above-described FIG. A pattern as shown was prepared.

Next, as the first insulating protective film 18, an Al ₂ O ₃ film having a thickness of 50 [nm] was formed using an ALD method. At this time, TMA (Sigma Aldrich Co.) was used as the Al raw material, O ₃ generated by an ozone generator was used as the O raw material, and the film formation proceeded by alternately laminating Al and O. Thereafter, as shown in FIGS. 4 and 5, a contact hole 18a was formed by etching.

Next, Al was sputtered as the common electrode lead-out wiring 20, the individual electrode lead-out wiring 22, the common electrode pad 19, and the individual electrode pad 21, and individualized by etching.

Next, 500 nm of Si ₃ N ₄ was formed as the second insulating protective film 23 by plasma CVD. Thereafter, openings 23a and the like were formed by etching, and an actuator substrate 25 in which common electrode pads 19 and individual electrode pads 21 were arranged in a row as shown in FIG. 5 was produced.

Next, a gold bump 171b is formed on the common electrode pad 19, and a silicon substrate (400 [μm]) in which a recess 26a, a common pad opening 26c, and an individual pad opening 26d are formed as the holding substrate 26. Was bonded to the actuator substrate 25 with an adhesive. Thereafter, gold bumps were formed on the upper surface of the holding substrate 26, and the common electrode pad 19 and the holding substrate 26 were connected by gold wire bonding as shown in FIG.

Thereafter, polarization treatment was performed by corona charging treatment. For corona charging treatment, a tungsten wire of φ50 [μm] was used as the corona electrode 71. As polarization treatment conditions, the treatment temperature is 80 [° C.], the corona voltage is 9 [kV], the grid voltage is 2.5 [kV], the treatment time is 30 [s], and the distance between the corona electrode and the grid electrode is 4 [ mm], and the distance between the grid electrode and the stage was 4 [mm].

[Example 2]
In Example 2, an SiO ₂ film was formed as an insulating film 27a on the upper surface of the holding substrate 26 by 1 [μm] by plasma CVD, and then Al [1 μm] was formed by sputtering. Thereafter, the conductive film 27b was formed by performing an etching process so that the Al film remains only at the peripheral edge of the common pad opening 26c for exposing the common electrode pad 19. Then, after the gold bump 171b is formed on the Al film, the common electrode pad 19 and the Al film (conductive film 27b) on the holding substrate 26 are connected by gold wire bonding, and the above-described examples shown in FIGS. The actuator substrate 25 and the holding substrate 26 of Modification 1 were produced. Other conditions are the same as in the first embodiment.

Example 3
In Example 3, an SiO ₂ film is formed on the upper surface of the holding substrate 26 as an insulating film 27a by 1 [μm] by plasma CVD. Etching was performed. Then, after producing gold bumps 171b on the exposed upper surface of the holding substrate 26, the common electrode pad 19 and the holding substrate 26 are connected by gold wire bonding, and the actuator of the modified example 2 shown in FIGS. A substrate 25 and a holding substrate 26 were produced. Other conditions are the same as in the first embodiment.

Example 4
In Example 4, Al was formed on the upper surface of the holding substrate 26 by 1 [μm] by sputtering, a gold bump 171b was formed on the Al film, and then the common electrode pad 19 and the holding substrate 26 were bonded by gold wire bonding. Then, the actuator substrate 25 and the holding substrate 26 shown in FIGS. 14 and 15 were manufactured. Other conditions are the same as in the first embodiment.

[Evaluation experiment]
Regarding Examples 1 to 4 described above, electrical characteristics (polarization rate) and displacement characteristics (piezoelectric constant) were evaluated. For the evaluation of the displacement characteristics, excavation was performed from the back side of the substrate, the amount of deformation due to electric field application (150 [kV / cm]) was measured with a laser Doppler vibrometer, and the piezoelectric constant was calculated from fitting by simulation. Moreover, after evaluating the initial characteristics, durability (characteristics immediately after applying the applied voltage 1 × 10 ¹⁰ times) was evaluated. The evaluation results are as shown in Table 1 below.

About Examples 1-3, it had the characteristic equivalent to a general ceramic sintered compact also about the result after an initial stage characteristic and a durability test. Specifically, the initial characteristic of the piezoelectric constant was 120 to 160 [pm / V], and there was little change from the initial characteristic even after the durability test, and good electromechanical conversion ability was shown.

On the other hand, Example 4 also had an initial characteristic of the piezoelectric constant of 120 to 160 [pm / V], which was equivalent to that of a general ceramic sintered body. Some change from the characteristics was observed. This is because an Al film (conductive film 27b) is formed on the periphery of the individual pad opening 26d exposing the individual electrode pad 21, so that cations due to discharge during the polarization process are individually generated in the individual pad opening 26d. This is considered to be because the potential difference between the common electrode 161 and the individual electrode 163 was insufficient because it was difficult to be supplied to the electrode pad 21.

In addition, droplet ejection evaluation was performed using a droplet ejection head manufactured using the actuator substrate 25 and the holding substrate 26 of Examples 1 to 4. Using an ink whose viscosity is adjusted to 5 [cp], and confirming the discharge situation when a voltage of −10 [V] to −30 [V] is applied by a simple push waveform, the ink liquid is discharged from all the nozzles 11. It was confirmed that droplets could be discharged.

In the above-described embodiment, the case where the polarization process is performed using the charge generated by the corona discharge has been described, but the case where the polarization process is performed using the charge generated by the glow discharge has the same configuration. Similar effects can be obtained.

Next, an ink jet recording apparatus that is an image forming apparatus provided with the droplet discharge head according to the present embodiment will be described.
FIG. 18 is a perspective view showing a configuration example of an ink jet recording apparatus equipped with a droplet discharge head, and FIG. 19 is a side view showing a configuration example of a mechanism section of the recording apparatus.
The ink jet recording apparatus 100 houses a printing mechanism 103 and the like inside the apparatus main body, and may be a paper feed cassette (or a paper feed tray) on which a large number of recording sheets 130 can be stacked from the front side in the lower part of the apparatus main body. ) 104 is removably mounted. Further, it has a manual feed tray 105 that is opened to manually feed the recording paper 130. The recording paper 130 fed from the paper feed cassette 104 or the manual feed tray 105 is taken in, a required image is recorded by the printing mechanism unit 103, and then discharged to the paper discharge tray 106 mounted on the rear side.

The printing mechanism 103 includes a carriage 101 that can move in the main scanning direction, a droplet discharge head mounted on the carriage 101, an ink cartridge 102 that supplies ink to the droplet discharge head, and the like. Further, the printing mechanism 103 holds the carriage 101 slidably in the main scanning direction with a main guide rod 107 and a sub guide rod 108 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 101 includes a droplet discharge head that discharges yellow (Y), cyan (C), magenta (M), and black (Bk) ink droplets, and a plurality of ink discharge ports (nozzles) in the main scanning direction. They are arranged in the intersecting direction and mounted with the ink droplet ejection direction facing downward. In addition, each ink cartridge 102 for supplying ink of each color to the droplet discharge head is replaceably mounted on the carriage 101.

The ink cartridge 102 is provided with an atmosphere port communicating with the atmosphere upward and a supply port for supplying ink to the droplet discharge head below. The ink cartridge 102 has a porous body filled with ink, and the ink supplied to the droplet discharge head is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the droplet discharge heads of the respective colors are used as the droplet discharge heads, one droplet discharge head having nozzles for discharging the ink droplets of the respective colors may be used.

Here, the carriage 101 is slidably fitted to the main guide rod 107 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 108 on the front side (upstream side in the paper conveyance direction). ing. In order to move and scan the carriage 101 in the main scanning direction, a timing belt 112 is stretched between a driving pulley 110 and a driven pulley 111 that are rotationally driven by a main scanning motor 109, and the timing belt 112 is attached to the carriage 101. It is fixed to. As a result, the carriage 101 is driven to reciprocate by forward / reverse rotation of the main scanning motor 109.

On the other hand, in order to convey the recording paper 130 set in the paper feeding cassette 104 to the lower side of the droplet discharge head, a paper feeding roller 113 and a friction pad 114 for separating and feeding the recording paper 130 from the paper feeding cassette 104, and recording And a guide member 115 for guiding the paper 130. Further, a conveyance roller 116 that reverses and conveys the fed recording paper 130, a conveyance roller 117 that is pressed against the peripheral surface of the conveyance roller 116, and a leading roller that defines the feeding angle of the recording paper 130 from the conveyance roller 116. 118. The transport roller 116 is rotationally driven through a gear train by a sub-scanning motor.

In addition, a printing receiving member 119 that is a paper guide member is provided to guide the recording paper 130 fed from the transport roller 116 corresponding to the range of movement of the carriage 101 in the main scanning direction on the lower side of the droplet discharge head. Yes. On the downstream side of the printing receiving member 119 in the paper conveyance direction, a conveyance roller 120 and a spur 121 that are rotationally driven to send the recording paper 130 in the paper discharge direction are provided. Further, a discharge roller 123 and a spur 124 for feeding the recording paper 130 to the discharge tray 106, and guide members 125 and 126 for forming a discharge path are provided.

When recording with the inkjet recording apparatus 100 having the above-described configuration, the droplet discharge head is driven in accordance with the image signal while moving the carriage 101 to discharge ink onto the stopped recording paper 130 to record one line. Thereafter, after the recording paper 130 is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the recording paper 130 reaches the recording area, the recording operation is terminated and the recording paper 130 is discharged.

Further, a recovery device 127 for recovering the ejection failure of the droplet ejection head is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 101. The recovery device 127 includes a cap unit, a suction unit, and a cleaning unit. During printing standby, the carriage 101 is moved to the recovery device 127 side, and the droplet ejection head is capped by the capping unit to keep the ejection port portion in a wet state, thereby preventing ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

When a discharge failure occurs, the discharge port (nozzle) of the droplet discharge head 1 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with the suction unit through the tube. In this way, ink or dust adhering to the ejection port surface is removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir. As described above, since the inkjet recording apparatus 100 of the present embodiment includes the recovery device 127, the ejection failure of the droplet ejection head is recovered, stable ink droplet ejection characteristics are obtained, and the image quality is improved. be able to.

In this embodiment, the case where a droplet discharge head is used in the inkjet recording apparatus 100 has been described. However, the droplet discharge head 1 is applied to a device that discharges droplets other than ink, for example, a liquid resist for patterning. May be.

Moreover, it is preferable that the electrical resistance value measured by connecting an electrical resistance measuring device between the electrodes of the piezoelectric element 16 in the present embodiment is 5.0 × 10 ¹⁰ [Ω] or more. With such an electric resistance value, it is possible to stably prevent the charge supplied from the charge supply opening to the charge supply terminal electrode from escaping to other members such as the holding substrate, and more stably. Thus, an appropriate polarization process can be realized.
The amount of leakage current when a voltage of 50 [V] is applied between the electrodes of the piezoelectric element 16 is preferably 1.0 × 10 ⁻⁸ [A] or less. If it is less than this leakage current amount, it becomes possible to generate a high electric field necessary for obtaining a desired polarization amount difference (Pr-Pini) between the electrodes of the electromechanical conversion element, and electromechanical conversion after continuous driving Sufficient characteristics can be obtained for the displacement deterioration of the element.

As described above, the ink jet recording apparatus (image forming apparatus) 100 according to the present embodiment includes the liquid discharge head according to the present invention as a recording head, so that high-quality images can be stably formed. In the ink jet recording apparatus, an image is formed by adhering ink droplets to a sheet by a droplet discharge head while conveying a medium. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by ejecting liquid droplets on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramic. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes a droplet when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Used as

Further, the image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
An electromechanical transducer such as a piezoelectric element 16 provided on the substrate 14 and a first electrode such as a common electrode pad 19 connected to a first drive electrode (common electrode 161 or the like) on the substrate side of the electromechanical transducer. 1 terminal electrode, a second terminal electrode such as an individual electrode pad 21 connected to a second drive electrode (individual electrode 163 or the like) on the opposite side of the substrate of the electromechanical transducer, and the electric machine An electromechanical conversion member comprising a holding substrate provided on the substrate so as to cover the conversion element so as to be displaceable, wherein the electromechanical conversion element is one of the first terminal electrode and the second terminal electrode. On the other hand, after the holding substrate 26 is connected to a certain grounding terminal electrode (such as the common electrode pad 19), or a charge transfer portion such as a conductive film 27b connected to the grounding terminal electrode is formed on the holding substrate. After A charge is supplied to a charge supply terminal electrode (individual electrode pad 21 or the like) which is the other of the first terminal electrode and the second terminal electrode in a state where the substrate or the charge transfer portion is connected to the ground, An electric field is formed between the first drive electrode and the second drive electrode, and polarization treatment is performed.
In the polarization processing of the electromechanical conversion element in this aspect, the ground terminal electrode that is one of the first terminal electrode and the second terminal electrode is grounded, and the charge supply terminal electrode that is the other is grounded. Supply charge. As a result, an electric field is formed between the first drive electrode and the second drive electrode of the electromechanical conversion element, and polarization processing is performed.
As a method of grounding the ground terminal electrode, a method of bringing a contact member such as a probe card connected to the ground into contact with the ground terminal electrode is conceivable. However, in order to avoid the influence of depolarization due to thermal history, when the polarization treatment is to be performed after a process such as holding substrate bonding, the electrode surface (exposed surface) for making electrical connection with the ground terminal electrode is very Get smaller. Therefore, the operation of bringing the contact member into contact with the exposed surface of the ground terminal electrode becomes complicated. It is also difficult to maintain the contact state stably throughout the polarization process after the contact member is brought into contact with the exposed surface of the ground terminal electrode. Therefore, with this method, it is difficult to stably ground the grounding terminal electrode.
In this embodiment, a charge transfer portion is formed on the holding substrate, the charge transfer portion and the ground terminal electrode are connected, and then the charge transfer portion on the holding substrate is connected to the ground, thereby Ground the terminal electrode. Since the size of the holding substrate is larger than that of the ground terminal electrode, it is easy to connect the charge transfer part on the holding substrate to the ground, and the contact state must be stably maintained during the polarization process. Is also easy. Therefore, even when the polarization process is performed after the holding substrate bonding process or the like, the ground terminal electrode can be stably grounded, and an appropriate polarization process can be realized.
Moreover, in this aspect, the polarization treatment can be performed at a stage close to the final process after the holding substrate is joined to the substrate on which the electromechanical conversion element, the first terminal electrode, and the second terminal electrode are formed. It is possible to avoid depolarization due to the influence of the thermal history in the subsequent process, and to obtain a good electromechanical conversion element.

(Aspect B)
In the aspect A, the charge transfer unit is a conductive film 27b formed on a surface (upper surface) of the holding substrate 26 opposite to the substrate, and the electromechanical conversion element includes the charge transfer unit and the charge transfer unit. The polarization processing is performed in a state where the grounding terminal electrode is connected by wire bonding.
According to this, since the grounding wiring is formed by the conductive film 27b different from the holding substrate 26, the electrical resistance between the grounding terminal electrode and the ground can be reduced regardless of the nature of the holding substrate 26. Can do. As a result, one electrode (electrode connected to the ground terminal electrode) of the electromechanical conversion element can be stably and sufficiently dropped to the ground, and an appropriate polarization process can be easily realized.

(Aspect C)
In the aspect A or B, the holding substrate 26 has a charge supply opening such as an individual pad opening 26d for exposing at least a part of the charge supply terminal electrode, and the electromechanical conversion element. Are arranged so as to face the holding substrate after an insulating portion such as an insulating film 27a is formed around the charge supply opening on the surface (upper surface) of the holding substrate 26 opposite to the substrate. By applying the discharge charge generated by the discharge electrode such as the corona electrode 71 to the charge supply terminal electrode from the charge supply opening, the charge supply terminal electrode is supplied with the charge, and the polarization treatment is performed. It has been made.
According to this aspect, the charge generated in the discharge electrode is applied to the charge supply terminal electrode from the charge supply opening, and is interposed between the first drive electrode and the second drive electrode of the electromechanical conversion element. A necessary electric field is formed to perform polarization processing. Such a polarization process by discharge does not require a contact member such as a probe card that is brought into direct contact with the terminal electrode, and can also be polarized at once for a plurality of electromechanical transducer elements with a simple configuration. Cost can be reduced.
In addition, since the insulating portion is formed around the charge supply opening in the holding substrate 26 during the polarization process, the charge generated in the discharge electrode moves from the charge supply opening to the charge supply terminal electrode. It's easy to do. Therefore, since charges can be applied to the charge supply terminal electrode more stably, it is easy to realize an appropriate polarization process.

(Aspect D)
In any one of the aspects A to C, the holding substrate includes a grounding opening such as a common pad opening 26c for exposing at least a part of the grounding terminal electrode, and the charge supply terminal. A charge supply opening such as an individual pad opening 26d for exposing at least a part of the electrode, and the electromechanical conversion element has a surface (upper surface) opposite to the substrate of the holding substrate. After an insulating portion such as an insulating film 27a is formed on the entire surface of the substrate, a conductive film 27b is formed as the charge transfer portion around the ground opening on the insulating portion, and is disposed so as to face the holding substrate. The electric charge generated by the discharge electrode is applied to the charge supply terminal electrode from the charge supply opening to supply the charge supply terminal electrode, and the polarization treatment is performed. about And features.
According to this aspect, the charge generated in the discharge electrode is applied to the charge supply terminal electrode from the charge supply opening, and is interposed between the first drive electrode and the second drive electrode of the electromechanical conversion element. A necessary electric field is formed to perform polarization processing. Such a polarization process by discharge does not require a contact member such as a probe card that is brought into direct contact with the terminal electrode, and can also be polarized at once for a plurality of electromechanical transducer elements with a simple configuration. Cost can be reduced.
In addition, since an insulating portion is formed around the charge supply opening in the holding substrate 26 during the polarization process, the charge generated in the discharge electrode moves from the charge supply opening to the charge supply terminal electrode. Cheap. Therefore, since charges can be applied to the charge supply terminal electrode more stably, it is easy to realize an appropriate polarization process.
Here, in this aspect, the electric charge generated at the discharge electrode is also applied to the ground terminal electrode from the ground opening. Therefore, in order to generate an appropriate potential difference between the electrodes of the electromechanical conversion element, the charge applied to the grounding terminal electrode is stably released to the ground, and one electrode (grounding terminal) of the electromechanical conversion element is released. It is important to drop the electrode connected to the electrode to the ground stably and sufficiently.
In this embodiment, since the grounding wiring is formed by the conductive film 27b different from the holding substrate 26, the electrical resistance between the grounding terminal electrode and the ground is reduced regardless of the nature of the holding substrate 26. Can do. Therefore, one electrode (electrode connected to the ground terminal electrode) of the electromechanical conversion element can be stably and sufficiently dropped to the ground, and an appropriate polarization process can be easily realized.

(Aspect E)
In any one of the aspects A to D, the holding substrate includes a grounding opening such as a common pad opening 26c for exposing at least a part of the grounding terminal electrode, and the charge supply terminal. A charge supply opening such as an individual pad opening 26d for exposing at least a part of the electrode, and the first terminal electrode and the second terminal electrode include an insulating protective film (second An insulating protective film 23) is covered, and the insulating protective film has an opening so that the first terminal electrode and the second terminal electrode are exposed from the charge supply opening and the ground opening. A portion 23a is provided.
According to this, the insulating protective film can suppress the charge supplied from the charge supply opening to the charge supply terminal electrode from escaping to other members such as the holding substrate, and is more stable. Appropriate polarization treatment.

(Aspect F)
Electromechanical conversion of a liquid chamber 13 that communicates with a nozzle 11 that discharges droplets, and a piezoelectric element 16 that is provided on a substrate 14 that forms the liquid chamber so that a liquid such as ink in the liquid chamber can be pressurized. In a liquid droplet ejection head having an electromechanical conversion member provided with an element, the electromechanical conversion member according to any one of the aspects A to E is used as the electromechanical conversion member.
According to this, stable ink ejection characteristics can be obtained using an electromechanical conversion element having good polarization characteristics.

(Aspect G)
In an image forming apparatus such as the inkjet recording apparatus 100 that discharges droplets from a droplet discharge head to form an image, the droplet discharge head according to the aspect F is used as the droplet discharge head. .
According to this, it is possible to form an image with stable ink ejection characteristics using an electromechanical conversion element having good polarization characteristics.

(Aspect H)
An electromechanical conversion element provided on the substrate; a first terminal electrode connected to the first drive electrode on the substrate side of the electromechanical conversion element; and the opposite side of the electromechanical conversion element from the substrate An electromechanical conversion element in an electromechanical conversion member comprising: a second terminal electrode connected to the second drive electrode; and a holding substrate provided on the substrate so as to displaceably cover the electromechanical conversion element. In the polarization processing method, a charge transfer portion connected to the ground terminal electrode which is one of the first terminal electrode and the second terminal electrode is formed on the holding substrate, and then the charge transfer The charge is supplied to the charge supply terminal electrode, which is the other of the first terminal electrode and the second terminal electrode, with the portion connected to the ground, and the first drive electrode and the second drive Forming an electric field with the electrode, Characterized by polarized gas transducer.
In the polarization processing of the electromechanical conversion element in this aspect, the ground terminal electrode that is one of the first terminal electrode and the second terminal electrode is grounded, and the charge supply terminal electrode that is the other is grounded. Supply charge. As a result, an electric field is formed between the first drive electrode and the second drive electrode of the electromechanical conversion element, and polarization processing is performed.
As a method of grounding the ground terminal electrode, a method of bringing a contact member such as a probe card connected to the ground into contact with the ground terminal electrode is conceivable. However, in order to avoid the influence of depolarization due to thermal history, when the polarization treatment is to be performed after a process such as holding substrate bonding, the electrode surface (exposed surface) for making electrical connection with the ground terminal electrode is very Get smaller. Therefore, the operation of bringing the contact member into contact with the exposed surface of the ground terminal electrode becomes complicated. It is also difficult to maintain the contact state stably throughout the polarization process after the contact member is brought into contact with the exposed surface of the ground terminal electrode. Therefore, with this method, it is difficult to stably ground the grounding terminal electrode.
In this embodiment, a charge transfer portion is formed on the holding substrate, the charge transfer portion and the ground terminal electrode are connected, and then the charge transfer portion on the holding substrate is connected to the ground, thereby Ground the terminal electrode. Since the size of the holding substrate is larger than that of the ground terminal electrode, it is easy to connect the charge transfer part on the holding substrate to the ground, and the contact state must be stably maintained during the polarization process. Is also easy. Therefore, even when the polarization process is performed after the holding substrate bonding process or the like, the ground terminal electrode can be stably grounded, and an appropriate polarization process can be realized.
Moreover, in this aspect, the polarization treatment can be performed at a stage close to the final process after the holding substrate is joined to the substrate on which the electromechanical conversion element, the first terminal electrode, and the second terminal electrode are formed. It is possible to avoid depolarization due to the influence of the thermal history in the subsequent process, and to obtain a good electromechanical conversion element.

DESCRIPTION OF SYMBOLS 1 Droplet discharge head 10 Droplet discharge part 11 Nozzle 12 Nozzle plate 13 Liquid chamber 14 Substrate 15 Vibrating plate 16 Piezoelectric element 18 First insulating protective film 19 Common electrode pad 20 Common electrode lead-out wiring 21 Individual electrode pad 22 Individual electrode lead-out Wiring 23 Second insulating protective film 25 Actuator substrate 26 Holding substrate 26a Recess 26c Common pad opening 26d Individual pad opening 27a Insulating film 27b Conductive film 161 Common electrode 162 Piezoelectric film 163 Individual electrode 171a Bonding wire 171b Gold bump

JP 2012-166393 A JP 2004-202849 A JP 2010-034154 A JP 2006-203190 A

Claims

An electromechanical transducer provided on the substrate;
A first terminal electrode connected to a first drive electrode on the substrate side of the electromechanical transducer;
A second terminal electrode connected to a second drive electrode opposite to the substrate of the electromechanical transducer;
In an electromechanical conversion member provided with a holding substrate provided on the substrate so as to cover the electromechanical conversion element in a displaceable manner,
The electromechanical conversion element is connected to the grounding terminal electrode after connecting the holding substrate to the grounding terminal electrode which is one of the first terminal electrode and the second terminal electrode. After the charge transfer portion is formed on the holding substrate, the charge supply portion which is the other of the first terminal electrode and the second terminal electrode in a state where the holding substrate or the charge transfer portion is connected to the ground supplying charge to the terminal electrode state, and are those polarized by an electric field between said first driving electrode and the second driving electrode,
The charge transfer part is a conductive film formed on a surface of the holding substrate opposite to the substrate,
The electromechanical conversion element, and said ground terminal electrode and the charge transfer portion in a state connected by wire bonding, electro-mechanical conversion member, characterized in der Rukoto which the polarization processing has been performed.
The electromechanical conversion member according to claim 1 ,
The holding substrate has a charge supply opening for exposing at least a part of the charge supply terminal electrode;
The electromechanical conversion element is a discharge electrode disposed so as to face the holding substrate after an insulating portion is formed around the charge supply opening on the surface of the holding substrate opposite to the substrate. The generated discharge charge is applied to the charge supply terminal electrode from the charge supply opening to supply the charge supply terminal electrode, and the polarization treatment is performed. An electromechanical conversion member.
  An electromechanical transducer provided on the substrate;
  A first terminal electrode connected to a first drive electrode on the substrate side of the electromechanical transducer;
  A second terminal electrode connected to a second drive electrode opposite to the substrate of the electromechanical transducer;
  In an electromechanical conversion member provided with a holding substrate provided on the substrate so as to cover the electromechanical conversion element in a displaceable manner,
  The electromechanical conversion element is connected to the grounding terminal electrode after connecting the holding substrate to the grounding terminal electrode which is one of the first terminal electrode and the second terminal electrode. After the charge transfer portion is formed on the holding substrate, the charge supply portion which is the other of the first terminal electrode and the second terminal electrode in a state where the holding substrate or the charge transfer portion is connected to the ground A charge is supplied to the terminal electrode, and an electric field is formed between the first drive electrode and the second drive electrode, and polarization treatment is performed.
  The holding substrate has a charge supply opening for exposing at least a part of the charge supply terminal electrode;
  The electromechanical conversion element is a discharge electrode disposed so as to face the holding substrate after an insulating portion is formed around the charge supply opening on the surface of the holding substrate opposite to the substrate. The generated discharge charge is applied to the charge supply terminal electrode from the charge supply opening to supply the charge supply terminal electrode, and the polarization treatment is performed. An electromechanical conversion member.
The electromechanical conversion member according to any one of claims 1 to 3,
The holding substrate has a grounding opening for exposing at least a part of the grounding terminal electrode, and a charge supply opening for exposing at least a part of the charge supply terminal electrode,
In the electromechanical conversion element, an insulating portion is formed on the entire surface of the holding substrate opposite to the substrate, and then a conductive film is formed as the charge transfer portion around the ground opening on the insulating portion. The charge supply terminal electrode is formed by applying a discharge charge generated by the discharge electrode disposed so as to face the holding substrate to the charge supply terminal electrode from the charge supply opening. An electromechanical conversion member supplied and subjected to the polarization treatment.
  An electromechanical transducer provided on the substrate;
  A first terminal electrode connected to a first drive electrode on the substrate side of the electromechanical transducer;
  A second terminal electrode connected to a second drive electrode opposite to the substrate of the electromechanical transducer;
  In an electromechanical conversion member provided with a holding substrate provided on the substrate so as to cover the electromechanical conversion element in a displaceable manner,
  The electromechanical conversion element is connected to the grounding terminal electrode after connecting the holding substrate to the grounding terminal electrode which is one of the first terminal electrode and the second terminal electrode. After the charge transfer portion is formed on the holding substrate, the charge supply portion which is the other of the first terminal electrode and the second terminal electrode in a state where the holding substrate or the charge transfer portion is connected to the ground A charge is supplied to the terminal electrode, and an electric field is formed between the first drive electrode and the second drive electrode, and polarization treatment is performed.
  The holding substrate has a grounding opening for exposing at least a part of the grounding terminal electrode, and a charge supply opening for exposing at least a part of the charge supply terminal electrode,
  In the electromechanical conversion element, an insulating portion is formed on the entire surface of the holding substrate opposite to the substrate, and then a conductive film is formed as the charge transfer portion around the ground opening on the insulating portion. The charge supply terminal electrode is formed by applying a discharge charge generated by the discharge electrode disposed so as to face the holding substrate to the charge supply terminal electrode from the charge supply opening. An electromechanical conversion member supplied and subjected to the polarization treatment.
The electromechanical conversion member according to any one of claims 1 to 5 ,
The holding substrate has a grounding opening for exposing at least a part of the grounding terminal electrode, and a charge supply opening for exposing at least a part of the charge supply terminal electrode,
The first terminal electrode and the second terminal electrode are covered with an insulating protective film,
The insulating protective film is provided with an opening so that the first terminal electrode and the second terminal electrode are exposed from the charge supply opening and the ground opening. Electromechanical conversion member.
A liquid chamber communicating with a nozzle for discharging droplets;
In a liquid droplet ejection head having an electromechanical conversion member provided with an electromechanical conversion element provided on a substrate forming the liquid chamber so that the liquid in the liquid chamber can be pressurized,
A droplet discharge head using the electromechanical conversion member according to any one of claims 1 to 6 as the electromechanical conversion member.
In an image forming apparatus that forms an image by discharging droplets from an electromechanical conversion member,
An image forming apparatus using the electromechanical conversion member according to claim 7 as the electromechanical conversion member.
An electromechanical conversion element provided on the substrate; a first terminal electrode connected to the first drive electrode on the substrate side of the electromechanical conversion element; and the opposite side of the electromechanical conversion element from the substrate An electromechanical conversion element in an electromechanical conversion member comprising: a second terminal electrode connected to the second drive electrode; and a holding substrate provided on the substrate so as to displaceably cover the electromechanical conversion element. A polarization processing method comprising:
After the holding substrate is connected to the grounding terminal electrode which is one of the first terminal electrode and the second terminal electrode, or the charge transfer portion connected to the grounding terminal electrode is connected to the holding substrate. After being formed thereon, the charge is supplied to the charge supply terminal electrode which is the other of the first terminal electrode and the second terminal electrode with the holding substrate or the charge transfer portion connected to the ground. Forming an electric field between the first drive electrode and the second drive electrode to polarize the electromechanical transducer ,
The polarization treatment is performed in a state where the charge transfer portion, which is a conductive film formed on a surface of the holding substrate opposite to the substrate, and the ground terminal electrode are connected by wire bonding. A polarization processing method for an electromechanical transducer.