JP2016004869A - Electromechanical conversion member, droplet discharge head, image forming apparatus, method of poling process of electromechanical conversion element, and method of manufacturing electromechanical conversion member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromechanical conversion member that can perform poling processing of a plurality of electromechanical conversion elements in a collective and uniform manner through discharge, and can avoid depolarization of the electromechanical conversion elements after the poling processing.SOLUTION: On the same surface side of an actuator substrate where a plurality of individual electrode pads 21, which are electrically connected to respective upper electrodes 163 of a plurality of piezoelectric elements 16, are formed to be exposed, a plurality of dummy individual electrode pads 24, which are electrically connected to the upper electrodes 163, are formed. In performing poling processing of the piezoelectric elements by supplying electrical charge to the piezoelectric elements 16 via the individual electrode pads 21 through discharge generated by a discharge electrode arranged to face the above surface, electrical charge is supplied to the upper electrodes 163 via the dummy individual electrode pads 24 so that the electrical charge to be supplied is made uniform.

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 an electromechanical conversion element used for the electromechanical conversion member And a method for manufacturing an electromechanical conversion member.

  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, the piezoelectric element 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 deformed by the deformation of the diaphragm. Is pressurized, and 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 is configured by sandwiching a piezoelectric film that is an electromechanical conversion film between a pair of drive electrodes. A diaphragm and a piezoelectric element are laminated on a substrate forming a liquid chamber, and further, an insulating protective film, wiring for electrically connecting the drive electrode to the outside, and a terminal electrode are formed on the piezoelectric element.

  The crystal of the piezoelectric film constituting the piezoelectric element has a random polarization direction as shown in FIG. 16A immediately after the piezoelectric element is manufactured. Thereafter, by repeating the voltage application, as shown in FIG. 16B, 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 Document 1, a discharge electrode that generates corona discharge is disposed on the surface of a plurality of piezoelectric films so as to face each other through a gap, and electric charges are supplied to the surface of the piezoelectric film by the corona discharge. A method is disclosed in which an electric field is generated in a film and the polarization treatment is performed in a lump.

  However, in the method disclosed in Patent Document 1, it is necessary to perform the polarization process with the surface of the piezoelectric film exposed, and after the piezoelectric film is formed, the polarization process is performed before the subsequent post-process is performed. I do. Heat treatment is performed in the subsequent steps, ie, the formation of an insulating protective film and the formation of wiring / terminal electrodes. For this reason, the piezoelectric film is depolarized due to the influence of the thermal history or the like in the subsequent process, and the electromechanical conversion characteristics return to the state before the polarization process as shown in the PE hysteresis characteristics of FIG. There is a risk that. For this reason, it is preferable that the polarization treatment by the discharge is performed after the formation of the insulating protective film and the wiring / terminal electrode formation with the high-temperature heat treatment.

  Further, according to the inventor's investigation, in the collective polarization process of the plurality of piezoelectric films by the discharge, the amount of charge supplied to the plurality of piezoelectric films is likely to be non-uniform. It has been found that there is a possibility that the polarization treatment may become insufficient without sufficient charge being supplied to the piezoelectric film.

  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.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to uniformly polarize a plurality of electromechanical transducer elements by discharge, and to provide an electromechanical transducer element after the polarization treatment. An electromechanical conversion member capable of avoiding depolarization is provided.

In order to achieve the above-mentioned object, the invention of claim 1 includes a plurality of electromechanical conversion elements comprising an electromechanical conversion film sandwiched between a pair of drive electrodes, and the plurality of electromechanical conversion films among the drive electrodes. A plurality of individual terminal electrodes electrically connected to individual drive electrodes respectively formed on one surface side; and the plurality of electromechanical transducer elements formed so that the plurality of individual terminal electrodes are exposed. In an electromechanical conversion member provided with an insulating protective film to protect,
A plurality of dummy individual terminal electrodes respectively electrically connected to the plurality of individual drive electrodes are formed on the surface side where the plurality of individual terminal electrodes are formed so as to be exposed from the insulating protective film, respectively. To do.

  According to the present invention, it is possible to provide an electromechanical conversion member that can uniformly polarize a plurality of piezoelectric elements by discharge and can avoid depolarization of the piezoelectric elements after the polarization treatment. effective.

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. Sectional drawing of the row | line | column which arranged in multiple numbers the droplet discharge part of FIG. Sectional drawing which shows an example of the layer structure of the diaphragm and piezoelectric element on a board | substrate. FIG. 5 is a more detailed top view of the periphery of the piezoelectric element of the droplet discharge head according to the embodiment. FIG. 4 is a more detailed cross-sectional view around the piezoelectric element of the droplet discharge head according to the embodiment. Explanatory drawing which shows an example of schematic structure of a corona discharge apparatus. (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. FIG. 10 is a more detailed top view of the periphery of a piezoelectric element of a droplet discharge head according to Modification Example 1. SrRuO characteristic diagram showing the ₃ film X-ray diffraction measurement results of the formed samples. Explanatory drawing which shows an example of arrangement | positioning of the electromechanical conversion member formed on a wafer. FIG. 5 is a more detailed top view of the periphery of the piezoelectric element of the droplet discharge head according to Comparative Example 1. The graph which shows the polarizability of the piezoelectric element of the edge part and center part in the electromechanical conversion member of Examples 1-3 and Comparative Examples 1-3. The graph which shows the crack incidence rate of the piezoelectric element of the edge part in the electromechanical conversion member of Examples 1-3 and Comparative Examples 1-3. FIG. 3 is a perspective view illustrating a configuration example of an ink jet recording apparatus including the droplet discharge head according to the embodiment. FIG. 3 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. The graph which shows the PE hysteresis loop characteristic of a piezoelectric element before polarization processing, after polarization processing, and after thermal history, respectively.

Hereinafter, with reference to the drawings, an electromechanical conversion member according to an embodiment of the present invention, a droplet discharge head that discharges droplets using the electromechanical conversion member, an image forming apparatus including the droplet discharge head, An example of a polarization processing method for an electromechanical transducer and a method for producing an electromechanical transducer will be described. Note that the present invention is not limited to these embodiments.
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 is a lower electrode 161 serving as a drive electrode on the substrate 14 side, a piezoelectric film 162 such as PZT described later as an electromechanical conversion film, and a drive electrode on the opposite side of the piezoelectric film 162 from the substrate 14 side. The upper electrode 163 is laminated. The lower electrode 161 is connected to a common electrode pad (19 in FIG. 4) as a terminal electrode for external connection described later. The upper electrode 163 is connected to an individual electrode pad (21 in FIG. 4) as a terminal electrode for external connection described later. In the droplet discharge unit 10, when a driving voltage is applied to the lower electrode 161 and the upper electrode 163 of the piezoelectric element 16 via the common electrode pad and the individual electrode pad, the piezoelectric film 162 is changed to the substrate 14 and the piezoelectric element 16. It vibrates so as to deform the diaphragm 15 between them. 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, an actual droplet discharge head has a configuration in which a plurality of droplet discharge units 10 are arranged in a row as shown in FIG. 2. Have.

  FIG. 3 is a cross-sectional view schematically showing the layer structure of the diaphragm and the piezoelectric element on the substrate. A diaphragm 15 is formed on the substrate 14, and layers of a lower electrode 161, a piezoelectric film 162, and an upper electrode 163 are formed so as to be in contact with the diaphragm 15. After the upper electrode 163 is formed, the piezoelectric film 162 and the upper electrode 163 are separated by etching to form a plurality of piezoelectric elements 16 as shown in FIG. That is, the upper electrode 163 functions as an individual driving electrode, and the lower electrode 161 functions as a common driving electrode for the individualized piezoelectric film 162 and upper electrode 163.

  4 is a more detailed top view around the piezoelectric element 16, and FIG. 5 is a more detailed cross-sectional view around the piezoelectric element 16. In FIG. 4, a part of the first insulating protective film 18 and the second insulating protective film 23 is not shown and is seen through so as to understand the configuration of the piezoelectric element.

  A first insulating protective film 18 is provided on the lower electrode 161 and the upper electrode 163. The first insulating protective film 18 has contact holes 18a and 18b for electrically connecting the lower electrode 161 and the upper electrode 163 to a first wiring 20 and a second wiring 22 described later, respectively. ing. A first wiring 20 and a second wiring 22 are provided on the first insulating protective film 18, and contact holes 18a and 18b provided in the first insulating protective film 18 are provided. These are electrically connected to the lower electrode 161 and the upper electrode 163, respectively. A part of the first wiring 20 is formed as a common electrode pad 19 which is a common terminal electrode for external connection electrically connected to the lower electrode 161 which is a common drive electrode. A part of the second wiring 22 is formed as an individual electrode pad 21 that is an individual terminal electrode for external connection that is electrically connected to the upper electrode 163 that is an individual drive electrode.

  Further, the lower electrode 161 and the first wiring 20 conducting to the upper electrode 163 and the second insulating protective film 23 protecting the upper electrode 163 and the second wiring 22 conducting to the first electrode 20, the second wiring It is formed on the wiring 22 (and on the first insulating protective film 18). The second insulating protective film 23 has a plurality of openings 23a and 23b, and the common electrode pad 19 and the individual electrode pad 21 are exposed. The individual electrode pads 21 are formed in a line as shown in FIG. A common electrode pad 19 is formed outside the end of the row of the individual electrode pads 21.

  Further, in the present embodiment, a plurality of dummy individual electrode pads 24 are formed in a row as dummy individual terminal electrodes so as to face the individual electrode pads 21 with the plurality of piezoelectric elements 16 interposed therebetween. The dummy individual electrode pad 24 will be described in detail later.

  The composite laminated substrate shown in FIGS. 4 and 5 including the substrate 14, the piezoelectric element 16, and various electrodes after the second insulating protective film 23 is formed is an electromechanical conversion member called an actuator substrate 30. .

  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 formed on the actuator substrate 30 will be described.
In the polarization processing of the present embodiment, corona discharge or glow discharge is performed on the actuator substrate 30 from which the common electrode pad 19, the individual electrode pad 21 and the like are exposed. The electric charge generated by the discharge process is supplied to the piezoelectric element 16 through the exposed common electrode pad 19, individual electrode pad 21, etc., so that the piezoelectric film 162 in the piezoelectric element 16 is polarized.

  FIG. 6 is a schematic configuration explanatory diagram of an example of a corona discharge device as a polarization processing device that performs polarization processing on the piezoelectric element 16. In FIG. 6, when corona discharge is performed using a corona wire electrode 52 as a discharge electrode, molecules in the atmosphere are ionized to generate cations and anions. Among the generated ions, positive ions flow into the piezoelectric element 16 through a pad (not shown) of the piezoelectric element 16 placed on the stage 53 disposed opposite to the corona wire electrode 52, and positive charges are accumulated. The polarization process of the piezoelectric film 162 is performed.

  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. 7A and 7B 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. 7, the 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 the polarizability. From this polarizability (Pr-Pini), it can be judged whether the polarization state is good or bad.

For example, the polarizability (Pr-Pini) is preferably 10 [μC / cm ² ] or less, and as shown in FIG. 7B, it is further 5 [μC / cm ² ] or less. preferable. On the other hand, when the value of the polarization difference (Pr−Pini) is larger than 10 [μC / cm ² ] as shown in FIG. 7A, the displacement deterioration after continuous driving as a piezoelectric actuator composed of a piezoelectric element. However, sufficient characteristics cannot be obtained.

  Here, problems in the polarization process when the conventional actuator substrate 30 is used will be described. In the conventional actuator substrate 30, a plurality of individual electrode pads 21 connected to the plurality of piezoelectric elements 16 are exposed from the openings 23 b provided in the second insulating protective film 23 and formed in a line. The actuator substrate 30 is subjected to corona discharge on the corona wire electrodes 52 disposed so as to supply charges to the plurality of individual electrode pads 21 to collectively polarize the plurality of piezoelectric elements 16.

  However, in such a polarization process, the charge supply to the upper electrodes 163 of the plurality of piezoelectric elements 16 tends to be uneven. Specifically, out of the plurality of individual electrode pads 21, charges are likely to concentrate on the individual electrode pads 21 at the end, and cracks may occur in the piezoelectric element 16 at the end. Therefore, if the discharge conditions are such that the amount of charge generated by corona discharge is suppressed so as to suppress cracking of the piezoelectric element 16 at the end, sufficient charge is supplied in a region other than the end (hereinafter referred to as the center). Therefore, the polarization process of the piezoelectric element 16 at the center portion becomes insufficient. That is, in the configuration in which the charges generated by the corona discharge are supplied to the upper electrodes 163 of the plurality of piezoelectric elements 16 only through the plurality of individual electrode pads 21, the polarization process is performed uniformly. It becomes difficult to process.

  Therefore, in the present embodiment, as shown in FIG. 4, dummy individual electrode pads 24 are formed in a row so as to face the individual electrode pads 21 with the plurality of piezoelectric elements 16 interposed therebetween. The dummy individual electrode pad 24 is electrically connected to the upper electrode 163 through a contact hole 18 c by a third wiring 25 provided on the first insulating protective film 18. Further, the dummy individual electrode pad 24 is exposed from the opening 23 c provided in the second insulating protective film 23 on the same surface side as the individual electrode pad 21 of the actuator substrate 30.

  When the corona wire electrode 52 arranged opposite to the actuator substrate 30 is subjected to corona discharge, electric charges can be supplied to the upper electrode 163 via the individual electrode pad 21 and the dummy individual electrode pad 24. At this time, among the plurality of individual electrode pads 21, the charge supplied via the individual electrode pad 21 at the end is larger than the charge supplied via the individual electrode pad 21 at the center. For this reason, the charge supplied through the plurality of dummy individual electrode pads 24 corrects the difference in the amount of charge supplied through the individual electrode pads 21 to make the charge amount supplied to the plurality of upper electrodes 163 uniform. A plurality of dummy individual electrode pads 24 are formed so as to be formed.

  Specifically, the electric charge supplied via the individual electrode pad 21 at the end is larger than the electric charge supplied via the individual electrode pad 21 at the center. Therefore, in order to correct this, the area of the dummy individual electrode pad 24b at the end is made smaller than the area of the dummy individual electrode pad 24a at the center. As a result, the electric charge supplied through the dummy individual electrode pad 24b at the end is smaller than the electric charge supplied through the dummy individual electrode pad 24a at the center, and as a result, the plurality of upper electrodes 163 The amount of charge supplied is made uniform.

  That is, the dummy individual electrode pad 24 is a charge supplying individual that supplies charges to the upper electrode 163 so as to suppress unevenness in the amount of charge supplied to the upper electrode 163 of the piezoelectric element 16 via the individual electrode pad 21. It functions as a terminal electrode. It is possible to uniformly polarize a plurality of piezoelectric elements 16 by performing a polarization process on the piezoelectric elements 16 using the charges supplied via the individual electrode pads 21 and the dummy individual electrode pads 24. It becomes.

  In this actuator substrate 30, even in a collective polarization process of the plurality of piezoelectric elements 16 by discharge, excessive charges are supplied to the piezoelectric elements 16 at the end portions to cause cracks, or sufficient for the piezoelectric elements 16 at the central portion. There is no possibility that the polarization process becomes insufficient without charge being supplied.

  In FIG. 4, although the area of the dummy individual electrode pad 24b located at the extreme end in the column direction is smaller than that of the dummy individual electrode pad 24a at the center, the present invention is not limited to this. The area of the dummy individual electrode pad 24 is adjusted so as to equalize the amount of charge supplied to the plurality of upper electrodes 163 in accordance with the arrangement of the individual electrode pads 21, the discharge conditions of the corona wire electrode 52, and the like. Specifically, a configuration in which the area of the plurality of dummy individual electrode pads 24 located at the end portion is reduced, a configuration in which the area of the dummy individual electrode pad 24 is gradually reduced toward the end portion, and the like are exemplified. .

  Note that it is considered that the amount of charge supplied to the plurality of upper electrodes 163 can be made uniform even in a configuration in which the area of the individual electrode pad 21 itself located at the end is reduced without providing the dummy individual electrode pad 24. However, if the area of the individual electrode pad 21 located at the end is different from the area of the individual electrode pad 21 at other positions, the value of the current that flows when the actual droplet discharge head is driven becomes different from that of the end. There are concerns that change with position. In the configuration in which the dummy individual electrode pad 24 of the present embodiment is provided and the amount of charge supplied to the plurality of upper electrodes 163 is uniform, the area of the individual electrode pad 21 can be the same. There is no.

[Modification 1]
Next, a modified example of the actuator substrate 30 used in the droplet discharge head in the present embodiment (hereinafter, this modified example is referred to as “modified example 1”) will be described.
In the above-described embodiment, the area of the dummy individual electrode pad 24 positioned at the end in the column direction is smaller than that of the center, but the first modification is a dummy individual electrode pad positioned at the end. In this example, 24b is covered with the second insulating protective film 23 so as not to be exposed.

  FIG. 8 is a more detailed top view of the periphery of the piezoelectric element of the droplet discharge head according to the first modification. Dummy individual electrode pads 24 are formed in a row so as to face the individual electrode pads 21 with the plurality of piezoelectric elements 16 interposed therebetween. The dummy individual electrode pad 24 is electrically connected to the upper electrode 163 through a contact hole 18 c by a third wiring 25 provided on the first insulating protective film 18. Among the plurality of dummy individual electrode pads 24 formed in a row, the dummy individual electrode pad 24b located at the end is covered with the second insulating protective film 23, and the individual electrode pad 21 of the actuator substrate 30 is covered. Not exposed on the same side as The other dummy individual electrode pad 24 a in the center is exposed from the opening 23 c provided in the second insulating protective film 23 on the same surface side as the individual electrode pad 21 of the actuator substrate 30.

  When the corona wire electrode 52 arranged opposite to the actuator substrate 30 is subjected to corona discharge, electric charges are supplied to the upper electrode 163 via the individual electrode pad 21 and the dummy individual electrode pad 24a excluding the end. can do. The charge supplied through the individual electrode pad 21 at the end is larger than the charge supplied through the individual electrode pad 21 at the center. In order to correct this, the charge is supplied through the dummy individual electrode pad 24a at the center while preventing the charge from being supplied through the dummy individual electrode pad 24b at the end. As a result, the amount of charge supplied to the plurality of upper electrodes 163 is made uniform.

  8 illustrates a configuration in which the dummy individual electrode pad 24b positioned at the extreme end in the column direction is covered with the second insulating protective film 23 so as not to be exposed, but is not limited thereto. The number of dummy individual electrode pads 24b that are not exposed is adjusted so as to equalize the amount of charge supplied to the plurality of upper electrodes 163 in accordance with the arrangement of the individual electrode pads 21, the discharge conditions of the corona wire electrode 52, and the like.

[Modification 2]
In the first modification described above, the same number of dummy individual electrode pads 24 as the individual electrode pads 21 are formed and covered with the second insulating protective film 23 so that the dummy individual electrode pads 24b at the ends are not exposed. However, the present invention is not limited to this, and when the dummy individual electrode pad 24 is patterned by a method described later, it is possible not to form a portion itself that becomes the dummy individual electrode pad 24b located at the end. This also provides the same effect as that of the first modification.

  In this way, the charge supplied through the plurality of dummy individual electrode pads 24 corrects the difference in the amount of charge supplied through the individual electrode pads 21 to obtain the amount of charge supplied to the plurality of upper electrodes 163. A plurality of dummy individual electrode pads 24 are formed so as to be uniform. Thereby, the amount of charge supplied to the plurality of upper electrodes 163 is made uniform, and the plurality of piezoelectric elements 16 can be uniformly polarized.

  Here, in the polarization processing method described in Patent Document 1, it is necessary to perform the polarization processing with the surface of the piezoelectric film 162 exposed. Therefore, a process of forming the first insulating protective film 18, the first wiring 20, the second wiring 22, the second insulating protective film 23, etc., accompanied by a high-temperature heat treatment on the piezoelectric element subjected to the polarization treatment. Will be implemented. 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 30 is formed through a process of forming the first insulating protective film 18, the first wiring 20, the second wiring 22, the third wiring 25, the second insulating protective film 23, and the like. After that, polarization treatment is performed. Thereby, depolarization by the influence of the thermal history by a post process can be prevented.

  Next, an example of the corona discharge device 50 that performs polarization processing that performs polarization processing shown in FIG. 6 will be described in detail. The corona discharge device 50 fixes a processing object such as a corona wire electrode 52 as a main discharge electrode, a corona electrode power supply 51, a grid electrode and power supply for grid electrodes (not shown), and a wafer on which a plurality of piezoelectric elements are formed. A stage 53 as a holding member to be placed is provided. The corona wire electrode 52 and the grid electrode (not shown) are connected to a corona electrode power source 51 and a grid electrode power source (not shown), respectively, and a predetermined voltage is applied thereto. Moreover, it is preferable that the stage 53 is grounded via a ground wire so that an electric charge can be easily applied to the processing object disposed on the stage 53.

  Further, the magnitude of the voltage applied to the corona wire electrode 52 and the grid electrode (not shown) and the distance between the stage 53 and each electrode are not particularly limited, so that sufficient polarization treatment can be performed. These can be adjusted to increase or decrease corona discharge. In addition, the configuration of the corona wire electrode 52 is not particularly limited. For example, the corona wire electrode 52 may have a wire shape, and may be formed of various conductive materials.

The grid electrode (not shown) is a conductive member having a large number of openings through which discharge charges generated by corona discharge can pass, and is disposed between the corona wire electrode 52 and the stage 53. The configuration of the grid electrode is not particularly limited, but it is preferable to devise the shape and mesh processing. By applying a high voltage to the corona wire electrode 52 by means of such a contrivance of the shape of the grid electrode or mesh processing, ions and charges generated by corona discharge are efficiently and uniformly poured onto the lower stage 53. can do. Thereby, an electric charge can be uniformly given with respect to the surface of a process target object.

  Further, a heating mechanism (not shown) is added to the stage 53 so that the processing object can be heated. This is because when the polarization process is performed while heating the piezoelectric element, the process can be performed while relaxing the stress of the piezoelectric element, so that even if a large amount of charge is supplied in order to obtain a desired polarization state, no cracks are generated. It is. The specific means of the heating mechanism for heating the piezoelectric element is not particularly limited, and can be configured to heat using various heaters, lamps and the like.

  The heating mechanism can be installed in the stage 53 or can be installed so as to heat from the outside of the stage 53. In particular, it is preferably installed in the stage 53 in order to avoid interference with electrodes and the like. 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 object to be manufactured, for example, the Curie temperature of the piezoelectric film constituting the piezoelectric element. . In particular, it is preferably configured to be able to heat up to a maximum of 350 [° C.] so as to be compatible with various piezoelectric elements. Although the heating temperature at the time of actually performing a polarization process is not specifically limited, It is preferable to heat below Curie temperature. This is because, for example, as shown in the PE hysteresis characteristic of FIG. 17, if the heating is performed at a temperature exceeding the Curie temperature, depolarization occurs again even if the polarization process is performed, and the effect of the polarization process is lost. Further, in order to more reliably prevent the temperature of the piezoelectric film from exceeding the Curie temperature, the heating temperature is preferably heated to a temperature that is half or less of the Curie temperature, and more preferably to a temperature that is 1/3 or less. preferable. For example, when a PZT (lead zirconate titanate having a perovskite crystal structure) film is used as the piezoelectric film, it is preferably heated to 180 [° C.] or less, more preferably 120 [° C.] or less.

  Further, the stage 53 has a moving mechanism capable of moving the processing object so that the entire processing object can be processed because the area to which the processing object is irradiated (supplied) when corona discharge is performed is limited. It has been added. By this moving mechanism, the entire processing object can be processed efficiently, and productivity can be improved. The moving mechanism of the stage 53 is not particularly limited. For example, the stage table may be held by a linear guide, and the movement of the table may be driven and controlled by a stepping motor via a feed mechanism such as a ball screw. .

In addition, the amount of charge Q required for performing the polarization process is not particularly limited, but a charge amount of 1.0 × 10 ⁻⁸ [C] or more is supplied (stored) to the piezoelectric element 16. Is preferred. Further, it is more preferable that a charge amount of 4.0 × 10 ⁻⁸ [C] or more is supplied (accumulated) to the piezoelectric element 16. By supplying the amount of charge in such a range to the piezoelectric element 16, the polarization process can be performed more reliably so as to have a polarizability described later.

  Further, the electric charge generated by corona discharge and moving to the stage side is charged positively or negatively according to the polarity of the driving voltage of the piezoelectric element in use. For example, Pini (polarization P at 0 [kV] of the PE hysteresis loop) after polarization processing of the PE hysteresis loop shown in FIG. 7B described later is the charge supplied to the piezoelectric element in the polarization process. When is positively charged, it is positioned on the positive side. Conversely, when the charge supplied to the piezoelectric element in the polarization step is negatively charged, Pini is positioned on the negative side. When applying a positive voltage when actually driving the piezoelectric element, Pini is preferably located on the positive side, and when applying a negative voltage, it is preferably located on the negative side. . For this reason, the electric charge supplied in a polarization process according to the use environment of a piezoelectric element can be charged positively or negatively.

  Next, the actuator substrate 30 constituting the liquid droplet ejection head of this embodiment will be specifically described.

The actuator substrate 30 can be manufactured, for example, by performing the following steps (1) to (7).
(1) A step of forming the lower electrode 161 on the substrate 14 or the diaphragm 15. Here, the lower electrode 161 may include an adhesion layer as described later.
(2) A step of forming the piezoelectric film 162 on the lower electrode 161.
(3) A step of forming the upper electrode 163 on the piezoelectric film 162.
(4) A step of individualizing the piezoelectric film 162 and the upper electrode 163 by etching. By performing this process, the upper electrode 163 serves as an individual drive electrode, and the lower electrode 161 functions as a common drive electrode for the individualized piezoelectric film 162 and upper electrode 163.
(5) A step of forming the first insulating protective film 18 on the lower electrode 161 and the upper electrode 163. In this step, a contact hole is formed in the first insulating protective film 18 in order to electrically connect the lower electrode 161 and the first wiring 20 and the upper electrode 163 to the second wiring 22 and the third wiring 25, respectively. 18a, 18b and 18c are formed.
(6) A step of forming the first wiring 20, the second wiring 22, and the third wiring 25 electrically connected to the lower electrode 161 and the upper electrode 163 on the first insulating protective film 18. During this process, the common electrode pad 19, the individual electrode pad 21, and the dummy individual electrode pad 24 are formed.
(7) A step of forming a second insulating protective film 23 on the first wiring 20, the second wiring 22, and the third wiring 25. During this step, openings 23a, 23b, and 23c that expose the common electrode pad 19, the individual electrode pad 21, and the dummy individual electrode pad 24 are formed.

Hereinafter, materials and construction methods that constitute the actuator substrate 30 will be described in detail.
[substrate]
The material of the substrate 14 is not particularly limited, but it is preferable to use a silicon single crystal substrate. The thickness is preferably 100 to 600 [μm].

  There are three types of plane orientation of the silicon single crystal substrate, (100), (110), and (111), but (100) and (111) are generally widely used in the semiconductor industry. In this configuration, a silicon single crystal substrate having a (100) plane orientation can be preferably used. In the piezoelectric element 16 in the present embodiment, a single crystal substrate having a (110) plane orientation can also be preferably used.

  When the liquid chamber 13 shown in FIG. 1 is produced on the substrate 14, the silicon single crystal substrate is generally processed using etching. In this case, anisotropic etching is used as an etching method. Is common.

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. Accordingly, a structure having an inclination of about 54 [°] can be produced in the plane orientation (100), whereas a deep groove can be dug in the plane orientation (110), so that the arrangement density can be maintained while maintaining rigidity. Can be high. For this reason, when producing a pressure chamber etc. using anisotropic etching, it is also possible to use a silicon single crystal substrate having a (110) plane orientation. However, in this case, SiO ₂ which is a mask material may be etched, so that it is desirable to use this in consideration.

[Vibration plate (undercoat film)]
As shown in FIG. 1, the vibration plate 15 is deformed and displaced by the force generated by the piezoelectric film 162, and the ink droplets in the liquid chamber 13 are ejected. Therefore, it is preferable that the diaphragm 15 has a predetermined strength.

The material constituting the vibration plate 15 may be any material that can be deformed and displaced to discharge the ink droplets in the liquid chamber 13 and can be arbitrarily selected according to required durability. SiO ₂ and Si ₃ N ₄ can be used. When these materials are used, they can be manufactured by a CVD (Chemical Vapor Deposition) method.

Moreover, it is preferable to select a material close to the linear expansion coefficient of the lower electrode 161 and the piezoelectric film 162 for the diaphragm 15. In particular, as the piezoelectric film 162, since PZT is generally used as a material, a material having a linear expansion coefficient close to 8 × 10 ⁻⁶ (1 / K) of PZT is preferable. Specifically, the material preferably has a linear expansion coefficient in the range of 5 × 10 ⁻⁶ (1 / K) to 10 × 10 ⁻⁶ (1 / K), and more preferably 7 × 10 ^−6. A material having a linear expansion coefficient in the range of (1 / K) to 9 × 10 ⁻⁶ (1 / K) is more preferable.

  In this case, specific materials 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 manufactured by a spin coater using a sputtering method or a sol-gel method.

  The film thickness is not particularly limited, but 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 may be difficult to process the liquid chamber 13 as shown in FIG. 1, and if it is larger than this range, the vibration plate 15 will not be easily deformed and displaced, and ink droplet ejection may become unstable. It is.

[Lower electrode (common drive electrode)]
For example, the lower electrode 161 shown in FIG. 1 is not particularly limited, but is preferably composed of a metal or a metal and an oxide. Specifically, the lower electrode 161 can be composed of, for example, a metal electrode film. Moreover, it can also be comprised from a metal electrode film and an oxide electrode film.

  Regardless of the material used for the lower electrode 161, it is preferable to devise an adhesive layer between the diaphragm 15 and the metal film so as to suppress peeling and the like. Details of the metal electrode film and oxide electrode film including the adhesion layer are described below.

The adhesion layer can be obtained, for example, by forming a metal film and then oxidizing (thermally oxidizing) it by an RTA method using an RTA (Rapid Thermal Annealing) apparatus to form an oxide film. Conditions for the oxidation (thermal oxidation) are not particularly limited, and can be selected depending on the material of the metal film to be used. For example, it can be formed by thermally oxidizing a metal film at 650 to 800 [° C.] for 1 to 30 minutes in an O ₂ atmosphere.

  The metal film can be formed by sputtering, for example. As a material for the metal film, materials such as Ti, Ta, Ir, and Ru can be preferably used, and among these, Ti can be preferably used.

  The metal oxide film may be formed by reactive sputtering, but a thermal oxidation method at a high temperature of the metal film is desirable. This is because, when manufacturing by reactive sputtering, for example, a substrate such as a silicon substrate needs to be heated together at a high temperature, so that a special sputtering chamber configuration is required, which is not preferable in terms of cost. In addition, the crystallinity of the metal oxide film is improved by the oxidation by the RTA apparatus than by the oxidation by a general furnace. This is explained by taking a titanium film as an example. According to oxidation by a normal heating furnace, a titanium film that is easily oxidized forms a number of crystal structures at a low temperature, so that it is necessary to break it once. On the other hand, in the oxidation by the RTA method having a high temperature rising rate, it is not necessary to go through such a process, and it becomes possible to form a good crystal.

  The thickness of the adhesion layer is not particularly limited, but is preferably in the range of 10 [nm] to 50 [nm], and more preferably in the range of 15 [nm] to 30 [nm]. When the film thickness is thinner than the above range, the adhesion with the diaphragm and the lower electrode may be deteriorated. Further, if the film thickness is larger than the above range, the crystal quality of the lower electrode film formed thereon may be affected. For this reason, it is preferable to select the said range.

  Conventionally, platinum having high heat resistance and low reactivity can be used as the metal material of the metal electrode film. In addition, since platinum may not have sufficient barrier properties with respect to lead, platinum group elements such as iridium and platinum-rhodium, and alloys thereof can also be used.

In addition, when platinum is used as the metal material of the metal electrode film, it is preferable that the adhesion layer is laminated first because adhesion to the base (particularly SiO ₂ ) is poor.

  The method for producing the metal electrode film is not particularly limited, but vacuum film formation such as sputtering or vacuum deposition can be used.

  The thickness of the metal electrode film may be selected according to the required performance, and is not limited, but is preferably 80 [nm] to 200 [nm], and is preferably 100 [nm] to 150 [150]. nm] is more preferable. When the thickness is smaller than the above range, it may not be possible to supply a sufficient current as the common drive electrode, which may cause problems when ink is ejected. In addition, when the thickness is larger than the above range, particularly when an expensive material of a platinum group element is used as the metal material of the metal electrode film, there is a problem in terms of cost. In particular, when platinum is used as the metal material, the surface roughness increases as the film thickness increases. This may affect the surface roughness and crystal orientation of a film (eg, an oxide electrode film or a piezoelectric film) formed thereon, and may cause a problem that sufficient displacement for ink ejection cannot be obtained. .

As a material for the oxide electrode film, it is preferable to use strontium ruthenate (SrRuO ₃ , hereinafter also simply referred to as “SRO”). Further, a material in which a part of strontium ruthenate is substituted, specifically, Sr _x A _(1-x) Ru _y B _(1-y) O ₃ (wherein A is Ba, Ca, B is Co, A material represented by Ni, x, y = 0 to 0.5) can also be preferably used.

  The oxide electrode film can be formed by sputtering, for example. Although the sputtering conditions are not limited, the film quality of the oxide film changes depending on the sputtering conditions, and can be selected according to the required crystal orientation.

  For example, the piezoelectric film 162 to be described later is preferably oriented in the (111) plane orientation as its crystallinity in order to suppress deterioration of displacement characteristics when continuously operated. In order to obtain such a piezoelectric film 162, it is preferable that the oxide electrode film disposed in the lower layer is also oriented in the (111) plane direction. For this reason, the oxide electrode film is preferably preferentially oriented in the (111) plane orientation.

  Then, in order to obtain a film preferentially oriented in the (111) plane orientation with respect to the oxide electrode film, it is preferable to heat the substrate to 500 [° C.] or higher, and form the oxide electrode film thereon by sputtering.

  Moreover, when providing a metal electrode film in the lower layer of an oxide electrode film, it is preferable that a metal electrode film consists of a platinum film. Moreover, it is preferable that it is oriented in the (111) plane orientation as the plane orientation. This is because it is easy to obtain an oxide electrode film formed thereon that is preferentially oriented in the (111) plane orientation.

  For example, as an SRO film forming condition, it is known that after SRO is formed at room temperature, it is thermally oxidized 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 a specific resistance as an electrode. However, as the crystal orientation of the film, (110) is likely to be preferentially oriented. When a PZT film is formed, this PZT film is also easily (110) oriented. For this reason, when forming the SRO film in the present embodiment, it is preferable to form the film under the above film forming conditions.

Here, for example, when a platinum film oriented in the (111) plane direction is used as a metal electrode film, and an SrRuO ₃ film as an oxide electrode film is formed thereon, the crystallinity of the oxide electrode is measured by X-ray diffraction measurement. The method of evaluation will be described.

Since Pt and SrRuO ₃ have close lattice constants, in the θ-2θ measurement in the normal X-ray diffraction measurement, the 2θ positions of the (111) plane of the SRO film and the (111) plane of Pt overlap and are difficult to discriminate. However, when Pt is tilted to Psi = 35 [°] due to the extinction law, the diffraction lines cancel each other at a position where 2θ is about 32 [°], and the diffraction intensity of Pt cannot be seen. Therefore, it is possible to confirm whether the SRO is preferentially oriented in the (111) plane orientation by inclining the Psi direction by about 35 [°] and judging from the peak intensity where 2θ is about 32 [°].

In FIG. 9, after forming a titanium oxide film as an adhesion layer on a silicon substrate, a platinum film oriented in the (111) plane orientation is formed, and the substrate is heated to, for example, 550 [° C.]. The X-ray diffraction measurement result of the sample on which the SrRuO ₃ film is formed by sputtering is shown.

  FIG. 9 shows data when 2θ = 32 [°] is fixed and Psi is changed. When Psi = 0 [°], almost no diffraction intensity is observed in the diffraction line on the (110) plane of SRO, and the diffraction intensity is observed in the vicinity of Psi = 35 [°]. ) It can be confirmed that the preferred orientation is in the plane orientation. In addition, from this result, it was confirmed that SRO was preferentially oriented in the (111) plane direction for those produced under the present film forming conditions.

  Further, when the SRO film prepared by performing the RTA process after forming the SRO film described above at room temperature was evaluated in the same manner, the diffraction intensity of SRO (110) was found when Psi = 0 [°]. It was seen.

  When it was estimated how much the displacement after driving was degraded compared to the initial displacement when continuously operating as a piezoelectric actuator, the orientation of the piezoelectric film (for example, PZT film) 162 had a great influence. , (110) may be insufficient in suppressing displacement deterioration. For this reason, as described above, the oxide electrode film is preferably oriented in the (111) plane orientation.

The surface roughness of the SrRuO ₃ film used for the oxide electrode is preferably 4 [nm] or more and 15 [nm] or less, and more preferably 6 [nm] or more and 10 [nm] or less. In addition, about the surface roughness here, the surface roughness (average roughness) measured by AFM is meant.

The surface roughness of the SrRuO ₃ film affects the film formation temperature, and when the substrate is heated from room temperature to 300 [° C.], the surface roughness is very small and becomes 2 [nm] or less. In this case, the surface roughness is very small and flat, but the crystallinity of the SrRuO ₃ film may not be sufficient. When the crystallinity of the SrRuO ₃ film is not sufficient as described above, a piezoelectric actuator having a piezoelectric film (for example, PZT film) 162 to be formed thereafter cannot obtain sufficient characteristics with respect to initial displacement and displacement deterioration after continuous driving.

Thus, considering the film formation conditions, the surface roughness obtained without deteriorating the crystallinity of the SrRuO ₃ film is considered to be within the above range. Therefore, the above range is preferable.

When it deviates from the above-mentioned range, the crystallinity of the SrRuO ₃ film may be deteriorated, and the insulation breakdown voltage of the piezoelectric film to be formed thereafter is deteriorated and may easily leak, which is not preferable.

In order to obtain the SrRuO ₃ film having the crystallinity and the surface roughness as described above, the film formation condition (temperature) is 500 [° C.] to 700 [° C.], preferably 520 [° C.] to 600 It is preferable to heat the substrate in the range of [° C.] and form a film by sputtering.

  The composition ratio of Sr and Ru after film formation is not particularly limited and is selected depending on required conductivity, etc., but Sr / Ru is preferably 0.82 or more and 1.22 or less. . This is because if it is out of the above range, the specific resistance increases, and sufficient conductivity as an electrode may not be obtained.

  Furthermore, the thickness of the SRO film as the oxide electrode is preferably 40 [nm] or more and 150 [nm] or less, and more preferably 50 [nm] or more and 80 [nm] or less. If the thickness is less than the above range, sufficient characteristics may not be obtained for initial displacement and displacement deterioration after continuous driving. In addition, it is difficult to obtain a function as a stop etching layer for suppressing overetching of the piezoelectric film. Further, if the film thickness exceeds the above-mentioned film thickness range, the dielectric strength voltage of the PZT formed thereafter is deteriorated and it may be likely to leak.

The specific resistance of the oxide electrode is preferably 5 × 10 ⁻³ [Ω · cm] or less, and more preferably 1 × 10 ⁻³ [Ω · cm] or less. If it is larger than this range, sufficient contact resistance cannot be obtained at the interface with the first wiring, and sufficient current cannot be supplied as a common drive electrode, which may cause problems when ink is ejected. Because.

[Piezoelectric film (electromechanical conversion film)]
As the piezoelectric film 162, any material having piezoelectricity can be used and is not particularly limited. For example, PZT that is widely used can be preferably used. PZT is a solid solution of lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ), and the characteristics differ depending on the ratio, but the ratio is not limited, and the required piezoelectric performance, etc. Can be selected. Among them, the ratio (molar ratio) between PbZrO ₃ and PbTiO ₃ is 53:47, and PzT (PZT (53/47) represented by Pb (Zr _0.53 , Ti _0.47 ) O ₃ in the chemical formula. Also show particularly good piezoelectric properties. Therefore, this PZT (53/47) can be preferably used.

  Barium titanate can also be used as a material other than PZT. In this case, it is possible to prepare a barium titanate precursor solution by using barium alkoxide and a titanium alkoxide compound as starting materials and dissolving them in a common solvent.

The PZT and barium titanate are represented by the general formula ABO ₃ . In addition to PZT and barium titanate, a composite oxide mainly composed of a composite oxide represented by ABO ₃ (A = Pb, Ba, Sr, B = Ti, Zr, Sn, Ni, Zn, Mg, Nb) is used. Can be used.

Further, as in (Pb _1-x , Ba _x ) (Zr, Ti) O ₃ , (Pb _1-x , Sr _x ) (Zr, Ti) O ₃ , part of Pb at the A site is replaced with Ba or Sr. It is also possible to use the composite oxide. The element used for substitution can be a divalent element. When heat treatment is performed when a piezoelectric film is formed by substituting a part of Pb with a divalent element, it is caused by evaporation of lead. There is an effect of reducing characteristic deterioration.

  A method for manufacturing the piezoelectric film 162 is not particularly limited, but for example, it can be manufactured by a spin coater using a sputtering method or a sol-gel method. Then, after the film formation, a desired pattern can be obtained by patterning by a pattern formation method using a photolithography technique and an etching technique (hereinafter referred to as “lithoetch method”).

A case where the piezoelectric film 162 made of PZT is manufactured by a sol-gel method will be described as an example.
PZT precursor solution is prepared by using lead acetate, zirconium alkoxide, and titanium alkoxide compound as starting materials, using methoxyethanol as a common solvent, and dissolving the above starting materials in a common solution so as to have a predetermined ratio to obtain a uniform solution. To do. 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 can be added to the precursor solution as a stabilizer. In addition, since the lead component may evaporate during heat treatment in the film forming process, it can be added in a larger amount than the stoichiometric ratio.

  When a PZT film is obtained on the entire surface of the base substrate, the PZT film can be 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 transformation from a coating film to a crystallized film involves volume shrinkage, the precursor concentration should be adjusted so that a film thickness of 100 [nm] or less can be obtained in one step in order to obtain a crack-free film. Preferably, a PZT film having a desired film thickness can be obtained by repeatedly performing the film forming process.

  The film thickness of the piezoelectric film 162 is not limited and may be selected according to the required piezoelectric characteristics, but is preferably 0.5 [μm] or more and 5 [μm] or less. [mu] m] or more and 2 [[mu] m] or less is more preferable. This is because if the thickness is smaller than the above range, sufficient displacement may not be generated when used as a piezoelectric actuator. On the other hand, if the thickness is larger than the above range, a number of layers are deposited in the manufacturing process, so that the number of processes increases and the process time becomes longer.

  The relative dielectric constant of the piezoelectric film 162 is preferably 600 or more and 2000 or less, and more preferably 1200 or more and 1600 or less. If the relative permittivity is smaller than the range, sufficient displacement characteristics may not be obtained when used as a piezoelectric actuator. Further, when the relative permittivity is larger than the range, there may be a problem in that the polarization process is not sufficiently performed and sufficient characteristics cannot be obtained for the displacement degradation after continuous driving.

[Upper electrode (individual drive electrode)]
Although it does not specifically limit as the upper electrode 163, For example, it can comprise from a metal electrode film. Moreover, it can also comprise from a metal electrode film and an oxide electrode film.

Details of the oxide electrode film and the metal electrode film are described below.
The material or the like of the oxide electrode film is the same as that described for the oxide electrode film of the lower electrode. The thickness of the oxide electrode film is preferably 20 [nm] or more and 80 [nm] or less, and more preferably 40 [nm] or more and 60 [nm] or less. If the film thickness is smaller than this range, sufficient characteristics may not be obtained for the initial displacement and displacement deterioration characteristics. If this range is exceeded, the dielectric strength of the piezoelectric film will be very poor, and leakage will easily occur. This is because there may be cases.

  The material of the metal electrode film is the same as that described for the metal electrode film of the lower electrode. The film thickness of the metal electrode film is preferably 30 [nm] to 200 [nm], and more preferably 50 [nm] to 120 [nm]. This is because if the thickness is smaller than this range, a sufficient current cannot be supplied as the individual drive electrodes, and problems may occur when ink is ejected. When the thickness is larger than this range, there is a problem in that the cost increases when an expensive platinum group element material is used as the material of the metal electrode film. Further, in the case of using platinum as a material, the surface roughness increases as the film thickness increases, and when the second wiring is formed through the first insulating protective film, film peeling, etc. This is because there is a case where the above-mentioned trouble is likely to occur.

[First insulating protective film]
The first insulating protective film 18 preferably has a function of preventing damage to the piezoelectric element 16 due to the film forming / etching process and preventing moisture in the air from permeating. Therefore, the material is preferably a dense inorganic material. In the case of organic materials, it is necessary to increase the film thickness in order to obtain sufficient protection performance. However, if the insulating film is made thick, the vibration displacement of the diaphragm is hindered and the liquid droplet ejection head has a low ejection performance. This is because there is a case of becoming.

In order to obtain high protection performance with a thin film, it is preferable to use a thin film of oxide, nitride, or carbide. However, a material having high adhesion to the electrode material, piezoelectric film material, and diaphragm material that is the base of the insulating film is used. It is preferable to select. Specifically, the first insulating protective film 18 is preferably made of at least one inorganic film selected from, for example, an alumina film, a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. More _{specifically, Al 2 O 3, ZrO 2} , Y 2 O 3, Ta 2 O 3, an oxide film used in the ceramic material, such as TiO ₂ can be cited as examples. These films have good adhesion, hard films, and excellent wear resistance and cost performance.

  The film formation method of the first insulating protective film 18 is also preferably a film formation method with a low possibility of damaging the piezoelectric element. For example, an evaporation method, an atomic layer deposition (ALD) method, or the like can be preferably used, and an ALD method with a wide range of usable materials can be more preferably used. In particular, by using the ALD method, a thin film having a very high film density can be manufactured, and damage during the process can be suppressed.

  The plasma CVD method in which a reactive gas is turned into plasma and deposited on the substrate, and the sputtering method in which the film is formed by causing the plasma to collide with the target material and flying may cause damage to the piezoelectric element, compared with the vapor deposition method and the ALD method. It is not preferable because it is expensive.

  The film thickness of the first insulating protective film 18 may be a thin film having a sufficient thickness for protecting the piezoelectric element and may be as thin as possible so as not to hinder the displacement of the diaphragm. It is not limited. For example, the thickness of the first insulating protective film is preferably in the range of 20 [nm] to 100 [nm]. If the thickness is greater than 100 [nm], the displacement of the diaphragm is reduced, which may result in a droplet ejection head with low ejection efficiency. On the other hand, when the thickness is less than 20 [nm], the function as a protective layer of the piezoelectric element may not be sufficient, and the performance of the piezoelectric element may be deteriorated.

  Further, a configuration in which another layer is provided as the first insulating protective film 18 to form two layers is also conceivable. In this case, for example, the second insulating film may be thickened so that the second insulating film is opened in the vicinity of the upper electrode so as not to inhibit the vibration displacement of the diaphragm.

Arbitrary oxides, nitrides, carbides, or composite compounds thereof can be used for the second insulating protective film. For example, SiO ₂ that is generally used in semiconductor devices can be used.

  Arbitrary methods can be used as a method for forming the second insulating protective film, 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 thickness of the second insulating protective film is preferably selected so as not to be broken down by a voltage applied between the lower electrode 161 and the second wiring 22. That is, it is preferable to set the electric field strength applied to the insulating film within a range not causing dielectric breakdown. Furthermore, in consideration of the surface property of the base of the second insulating film, pinholes, etc., the film thickness is preferably 200 [nm] or more, and more preferably 500 [nm] or more.

[Wiring, pad]
The first wiring 20 is electrically connected to the lower electrode 161, and the first wiring 22 and the third wiring 25 are electrically connected to the upper electrode 163, and are formed on the first insulating protective film 18.

  The material of the first wiring 20, the second wiring 22, and the third wiring 25 is not particularly limited, and may be selected according to required performance. For example, Ag alloy, Cu, Al It is preferably made of at least one metal selected from Al alloy, Au, Pt, and Ir. These metals can form a low-resistance and durable electrode on the substrate.

  As a method of manufacturing the first wiring 20, the second wiring 22, and the third wiring 25, for example, a sputtering method or a spin coating method is used, and then a desired pattern is obtained by the above-described lithoetching method or the like. The method can be preferably used.

  The film thicknesses of the first wiring 20, the second wiring 22, and the third wiring 25 are preferably 0.1 [μm] to 20 [μm], and more preferably 0.2 [μm] to 10 [μm]. preferable. If the film thickness is smaller than the above range, the resistance increases, and a sufficient current cannot flow through the electrode, and the droplet discharge head may become unstable when the droplet discharge head is used. On the other hand, if the film thickness is larger than the above range, the process time becomes long, which may cause a problem in productivity.

  Further, the portion of the first wiring 20 exposed from the opening 23 a of the second insulating protective film 23 becomes the common electrode pad 19. Further, the portion of the second wiring 22 exposed from the opening 23 b of the second insulating protective film 23 becomes the individual electrode pad 21. Further, a portion of the third wiring 25 exposed from the opening 23 c of the second insulating protective film 23 becomes a dummy individual electrode pad 24. The method for forming the portions to be the common electrode pad 19, the individual electrode pad 21, and the dummy individual electrode pad 24 is not particularly limited. it can.

  The contact resistance at the opening 23a of the common electrode pad 19 is preferably 10 [Ω] or less, and the contact resistance of the individual electrode pad 21 is preferably 1 [Ω] or less. Furthermore, the contact resistance of the common electrode pad 19 is more preferably 5 [Ω] or less, and the contact resistance of the individual electrode pad 21 is more preferably 0.5 [Ω] or less. This is because when the contact resistance at the openings 23a and 23b of the pads 19 and 22 exceeds the above range, a sufficient current cannot be supplied. This is because a problem may occur when the operation is performed.

[Second insulating protective film]
The second insulating protective film 23 functions as a passivation layer having a function of a protective layer for the first wiring 20 and the second wiring 22.

  The second insulating protective film 23 is except for an opening 23a for exposing the common electrode pad 19, an opening 23b for exposing the individual electrode pad 21, and an opening 23c for exposing the dummy individual electrode pad 24. The first wiring 20, the second wiring 22, and the third wiring 25 are covered (see FIG. 5). By providing the second insulating protective film 23 in this way, 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 can be obtained.

  As the material of the second insulating protective film 23, any inorganic material or organic material can be used, but it is preferable to use a material having low moisture permeability.

  As the inorganic material, for example, an oxide, nitride, carbide, or the like can be used, and as the organic material, polyimide, an acrylic resin, a urethane resin, or the like can be used. However, in the case of an organic material, it is necessary to form a thick film, which is not suitable for patterning described later. Therefore, it is more preferable to use an inorganic material that can exhibit a wiring protection function with a thin film.

Therefore, the second insulating protective film 23 is preferably at least one inorganic film selected from an alumina film, a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. In particular, the use of Si ₃ N ₄ as the second insulating protective film on the Al wiring is a technology that has a proven record in semiconductor devices. Therefore, it is preferable to adopt the same configuration also in this embodiment.

  The thickness of the second insulating protective film 23 is preferably 200 [nm] or more, and more preferably 500 [nm] or more. This is because, when the film thickness is small, a sufficient passivation function cannot be exhibited, and thus disconnection due to corrosion of the wiring material may occur, which may reduce the reliability of the piezoelectric element.

  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 near the upper electrode 163 of the first insulating protective film 18 is thinned. Thereby, it can be set as a highly efficient and highly reliable piezoelectric element. Further, for example, a highly efficient and highly reliable droplet discharge head using the piezoelectric element 16 can be obtained.

  In addition, since the piezoelectric element is protected by the first insulating protective film 18 and the second insulating protective film 23, a photolithography method and dry etching are used to form the opening of the second insulating protective film 23. be able to.

  By using the actuator substrate 30 of the present embodiment described above, polarization processing can be performed on the plurality of piezoelectric elements 16 at once. As a result, as in the embodiments to be described later, it is possible to perform polarization processing collectively at the wafer level.

  In the droplet discharge head, a holding substrate (not shown) 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 30. Join with agent. The holding substrate is provided with a recess for covering the piezoelectric element 16 through a gap at a portion where the piezoelectric element 16 is located. The holding substrate has an opening in which a piezoelectric element driving IC (not shown) 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. doing. The individual electrode pad 21 is exposed in the opening, and the piezoelectric element driving IC is electrically connected to the individual electrode pad 21 via a bump electrode or the like.

  The dummy individual electrode pad 24 is preferably bonded to the holding substrate by bonding the opening 23c with an adhesive when the holding substrate is bonded to the actuator substrate 30 after the polarization treatment. This is to avoid the possibility that the actuator substrate 30 is not stable in terms of potential when the dummy individual electrode pad 24 is exposed when the droplet discharge head is driven.

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

  According to this droplet discharge head, since the actuator substrate 30 including the piezoelectric element 16 described above is used, a stable amount of displacement is exhibited with respect to a predetermined drive voltage, and the droplet discharge characteristics can be maintained well and stable. The droplet discharge characteristics can be obtained.

  Next, more specific examples of the polarization treatment of the electromechanical conversion member provided with the dummy individual electrode pads 24 and the results of evaluation experiments on these examples will be described. However, the present invention is not limited to these examples.

[Example 1]
In Example 1, a thermal oxide film (film thickness: 1 [μm]) serving as the vibration plate 15 was formed on a 6-inch silicon wafer serving as the substrate 14.

Next, a lower electrode (common drive electrode) 161 was formed. Specifically, a titanium film (thickness 30 [nm]) was first formed as an adhesion film with a sputtering apparatus, and then thermally oxidized at 750 [° C.] using RTA. Subsequently, a platinum film (film thickness 100 [nm]) was formed as a metal film, and an SrRuO ₃ film (film thickness 60 [nm]) was formed as an oxide film by sputtering. Film formation was performed at a substrate heating temperature of 550 [° C.] during the sputtering film formation.

  Next, a piezoelectric film (electromechanical conversion film) 162 was formed. Specifically, a solution having a molar ratio of Pb: Zr: Ti = 114: 53: 47 was prepared, and a film was formed by spin coating.

  For the synthesis of a specific precursor coating solution, lead acetate trihydrate, isopropoxide titanium, and normal propoxide 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 normal propoxide 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 in the synthesized PZT precursor solution was 0.5 [mol / L].

  Using the precursor solution, a plurality of operations are performed by forming a film on the substrate on which the lower electrode is formed by spin coating, performing 120 [° C.] drying after the film formation, and then further performing thermal decomposition at 500 [° C.]. The piezoelectric film was laminated repeatedly.

  When the piezoelectric film was laminated by repeating the above procedure, crystallization heat treatment (temperature 750 [° C.]) was performed by RTA (rapid heat treatment) after the thermal decomposition treatment of the third layer. After the thermal decomposition treatment of the third layer, the film thickness of the piezoelectric film (PZT film) 162 subjected to RTA treatment was 240 [nm].

  The above process was performed a total of 8 times (24 layers) to obtain a piezoelectric film 162 having a PZT portion thickness of about 2 [μm].

Next, an SrRuO ₃ film (film thickness 40 [nm]) was formed by sputtering as an oxide film of the upper electrode, and a Pt film (film thickness 125 [nm]) was formed by sputtering as a metal film.

  Thereafter, a photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed by spin coating, and a resist pattern was formed by ordinary photolithography. Thereafter, the piezoelectric film and the upper electrode were individually separated by etching using an inductively coupled plasma (ICP) etching apparatus (manufactured by Samco) to produce a pattern as shown in FIG. Accordingly, the upper electrode functions as an individual drive electrode, and the lower electrode functions as a common drive electrode for the individual piezoelectric film and the upper electrode.

Next, as the first insulating protective film, an Al ₂ O ₃ film having a thickness of 50 nm was formed by the ALD method.

As raw materials, trimethylaluminum (TMA) (manufactured by Sigma-Aldrich) was used as the Al source, and O ₃ generated by an ozone generator was used as the O source. Then, an Al source and an O source were alternately supplied onto the substrate and laminated to form a film.

  Thereafter, as shown in FIGS. 4 and 5, contact hole portions were formed by etching.

  Then, Al was sputtered as the first wiring, the second wiring, and the third wiring, and was patterned by etching.

After that, Si ₃ N ₄ was formed as a second insulating protective film to a thickness of 500 [nm] by plasma CVD. Thereafter, by etching, the common electrode pad 19, the individual electrode pad 21, and the dummy individual electrode pad 24 are formed to be exposed, and an electromechanical conversion member having a plurality of piezoelectric elements 16 as shown in FIG. 4 is produced. .

  As shown in FIG. 4, the individual electrode pads 21 were formed in a line in the same array in a straight line. At this time, the openings 23c were formed in the second insulating protective film 23 so that the areas of the individual electrode pads 21 were all 50 [μm] × 50 [μm]. On the other hand, in the dummy individual electrode pad 24, the area of the dummy individual electrode pad 24a at the center is 50 [μm] × 50 [μm], and the area of the dummy individual electrode pad 24b at the end is 40 [μm] × 40 [μm]. An opening 23c was formed in the second insulating protective film 23 so that

  In addition, as shown in FIG. 10, 22 areas [chips] of 40 [mm] × 20 [mm] serving as the actuator substrate 30 were arranged in 22 places in a 6-inch wafer. In the chip of the actuator substrate 30, 1200 (300 × 4 rows (A to D)) individual electrode pads 21 and eight common electrode pads 19 were formed. Further, although not shown, 1200 (300 × 4 rows (A to D)) dummy individual electrode pads 24 are formed so as to face the individual electrode pads 21 with the piezoelectric element 16 interposed therebetween.

  As the corona wire electrode 52 of the corona discharge device 50, a φ50 [μm] tungsten wire is used. The vertical distance between the corona wire electrode 52 and the wafer is 10 [mm], the vertical distance between the center of the grid electrode and the wafer is 5 [mm], 8 [kV] with respect to the corona wire electrode 52, and 0 with the grid electrode. A voltage of .8 [kV] was applied. At this time, as shown in FIG. 11, the corona wire electrode 52 was set at the center of the B and C rows, and corona polarization treatment was performed on a total of 8 rows for 20 seconds per row. The temperature of the stage 53 was 80 [° C.].

[Example 2]
In the second embodiment, an electromechanical transducer having a plurality of piezoelectric elements arranged in the same manner as in the first embodiment except that the area of the dummy individual electrode pad 24b at the end is 30 [μm] × 30 [μm]. Fabricated on a wafer and subjected to polarization treatment.

Example 3
In Example 3, as shown in FIG. 10, an electromechanical conversion element in which a plurality of piezoelectric elements are arranged on a wafer is produced in the same manner as in Example 1 except that the dummy individual electrode pad 24b at the end is not exposed. Then, polarization treatment was performed.
[Comparative Example 1]
In Comparative Example 1, as shown in FIG. 11, the area of the dummy individual electrode pad 24b at the end is set to 50 [μm] × 50 [μm] similarly to the area of the dummy individual electrode pad 24a at the center. . Other than that, an electromechanical transducer having a plurality of piezoelectric elements arranged thereon was produced on the wafer in the same manner as in Example 1 and subjected to polarization treatment.

[Comparative Example 2]
In Comparative Example 2, an electromechanical transducer having a plurality of piezoelectric elements arranged thereon was produced on the wafer in the same manner as in Example 1 except that the dummy individual electrode pad 24 was not provided, and polarization treatment was performed.

[Comparative Example 3]
In Comparative Example 3, a dummy individual electrode pad 24 similar to that in Comparative Example 2 was used except that the polarization treatment conditions were such that a voltage of 9 [kV] was applied to the corona wire electrode 52 and a voltage of 1.5 [kV] was applied to the grid electrode. An electromechanical conversion member not provided was prepared and subjected to polarization treatment.

[Evaluation experiment]
Regarding the electromechanical conversion members manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 described above, the rate of occurrence of cracks in the 176 piezoelectric elements at the end (2 bits × 4 rows × 22 chips) and The polarizability Pr-Pini of the piezoelectric elements at the end and the center was evaluated.
FIG. 12 is a graph showing the polarizability Pr-Pini of the end and center piezoelectric elements in the electromechanical conversion members of Examples 1 to 3 and Comparative Examples 1 to 3. In addition, the polarizability of a center part is an average value of the polarizability of the piezoelectric element located other than an edge part. Moreover, FIG. 13 is a graph which shows the crack generation rate of the piezoelectric element of the edge part in the electromechanical conversion member of Examples 1-3 and Comparative Examples 1-3.

In the electromechanical conversion member of Example 1 or 2 where the area of the dummy individual electrode pad 24b at the end is smaller than the area of the dummy individual electrode pad 24a at the center, as shown in FIG. 12, the polarizability Pr of the piezoelectric element 16 -Pini is 5.0 [[mu] C / cm < ² >] or less for both the end and the center. From this, it can be said that the piezoelectric element 16 has been subjected to favorable polarization processing regardless of the position in the column direction. Further, as shown in FIG. 13, no crack is generated in the piezoelectric element 16 at the end (0 [%]).

Even in the electromechanical conversion member that does not expose the dummy individual electrode pad 24b at the end of the dummy individual electrode pad 24b at the end of Example 3, the polarizability Pr-Pini of the piezoelectric element 16 is as shown in FIG. Both the central part and the central part are 5.0 [μC / cm ² ] or less. From this, it can be said that the piezoelectric element 16 has been subjected to favorable polarization processing regardless of the position in the column direction. Further, as shown in FIG. 13, no crack is generated in the piezoelectric element 16 at the end (0 [%]).

In the electromechanical conversion member of Comparative Example 1 in which the area of the dummy individual electrode pad 24b at the end is the same as the area of the dummy individual electrode pad 24a at the center, as shown in FIG. 12, the polarizability of the piezoelectric element 16 Pr-Pini is 5.0 [μC / cm ² ] or less for both the end and the center. However, as shown in FIG. 13, cracks occurred in the piezoelectric element 16 at the end, although a slight 2.3%. From this, it can be said that although the piezoelectric element 16 is subjected to favorable polarization processing regardless of the position in the column direction, excessive charge is supplied to the end portion to cause cracks.

Comparative Example 2 is an electromechanical conversion member that has been subjected to polarization treatment under the same polarization treatment conditions as in Examples 1 to 3 and Comparative Example 1 without forming dummy individual electrode pads 24b. In this electromechanical conversion member, as shown in FIG. 12, the polarizability Pr-Pini of the piezoelectric element 16 is 5.0 [μC / cm ² ] at the end, but 11.4 [μC / cm2] at the center. cm ² ]. In other words, it can be said that the central piezoelectric element 16 is not subjected to good polarization treatment. Further, as shown in FIG. 13, no cracks are generated in the piezoelectric element 16 at the end (0 [%]).

Comparative Example 3 is an electromechanical conversion member that has been subjected to polarization treatment under the polarization treatment conditions in which a larger amount of charge is generated than in Examples 1 to 3 and Comparative Examples 1 and 2 without forming dummy individual electrode pads 24b. . In this electromechanical conversion member, as shown in FIG. 12, the polarizability Pr-Pini of the piezoelectric element 16 is 1.2 [μC / cm ² ] at the end, but 2.2 [μC / cm ² at the center. cm ² ]. That is, as compared with the comparative example 2 in which the dummy individual electrode pad 24b is not formed, a favorable polarization process can be performed on both the end part and the center part by performing the process under the polarization process condition that generates a large amount of charge. However, as shown in FIG. 13, cracks occurred in 50% of the piezoelectric element 16 at the end.

As described above, in the first to third embodiments, the dummy individual electrode pad 24 is provided, and the upper electrode is corrected so as to correct nonuniformity in the amount of charge supplied via the dummy individual electrode pad 24 via the individual electrode pad 21. Charge is supplied to 163. Thus, the piezoelectric element 16 is subjected to a favorable polarization process in which the polarizability Pr-Pini is 5.0 [μC / cm ² ] or less at both the end and the center. Further, it can be said that the polarities of the end portion and the central portion become uniform as the exposed area of the dummy individual electrode pad 24b at the end portion is smaller than that of the dummy individual electrode pad 24b at the center portion.

  On the other hand, the comparative example 1 has a configuration in which the dummy individual electrode pad 24 is provided. If the dummy individual electrode pad 24b at the end has the same area as the dummy individual electrode pad 24a at the center, the upper electrode at the end is formed. This shows that the charge supply to 163 becomes excessive and cracks occur. Therefore, by providing the dummy individual electrode pad 24, and making the area of the dummy individual electrode pad 24b at the end smaller than the dummy individual electrode pad 24b at the center, a desired polarizability can be obtained, and It is possible to prevent cracks from occurring.

  In addition, droplet ejection evaluation was performed using a droplet ejection head manufactured using an actuator substrate 30 formed from an electromechanical conversion member having a configuration in which dummy individual electrode pads 24 were provided. 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. However, 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.

  In the above-described embodiment, the configuration in which the individual electrode pads 21 are arranged in a row has been described. However, the present invention is not limited to this. Even if the electric charge supplied through the individual electrode pad 21 is non-uniform, the dummy individual electrode pad 24 is formed so as to supply the electric charge for correcting the non-uniformity through the dummy individual electrode pad 24. The conversion film can be uniformly polarized at once.

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. 14 is a perspective view illustrating a configuration example of an ink jet recording apparatus equipped with a droplet discharge head, and FIG. 15 is a side view illustrating a configuration example of a mechanism unit 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 1 mounted on the carriage 101, an ink cartridge 102 that supplies ink to the droplet discharge head 1, 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 has a droplet discharge head 1 for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), and a plurality of ink discharge ports (nozzles) in the main scanning direction. And are 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 1 is replaceably mounted on the carriage 101.

  The ink cartridge 102 is provided with an atmosphere port communicating with the atmosphere above, and a supply port for supplying ink to the droplet discharge head 1 below. The ink cartridge 102 has a porous body filled with ink, and the ink supplied to the droplet discharge head 1 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 1, 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 a guide member 115 for guiding the recording 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 movement range of the carriage 101 in the main scanning direction on the lower side of the droplet discharge head 1. ing. 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 1 is driven in accordance with an image signal while moving the carriage 101, thereby ejecting ink onto the stopped recording paper 130 to form one line. Record. Thereafter, the recording paper 130 is conveyed by a predetermined amount, and then 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.

  A recovery device 127 for recovering the ejection failure of the droplet ejection head 1 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 discharge head 1 is capped by the capping unit to keep the discharge port portion in a wet state, thereby preventing discharge 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 according to the present embodiment includes the recovery device 127, the ejection failure of the droplet ejection head 1 is recovered, stable ink droplet ejection characteristics are obtained, and image quality is improved. can do.

  In this embodiment, the case where the droplet discharge head 1 is used in the ink jet recording apparatus 100 has been described. However, the droplet discharge head 1 is used in a device that discharges droplets other than ink, for example, a liquid resist for patterning. You may apply.

  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 a high-quality image 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 plurality of piezoelectric elements 16 composed of an electromechanical transducer such as a piezoelectric film 162 sandwiched between a pair of drive electrodes such as a lower electrode 161 and an upper electrode 163, and the plurality of electric A plurality of individual terminal electrodes such as individual electrode pads 21 electrically connected to individual drive electrodes such as the upper electrode 163 respectively formed on one surface side of the mechanical conversion film, and the plurality of individual terminal electrodes respectively In an electromechanical conversion member such as an actuator substrate 30 provided with an insulating protective film such as a second insulating protective film 23 that protects the plurality of electromechanical conversion elements formed to be exposed,
Dummy individual terminal electrodes such as a plurality of dummy individual electrode pads 24 electrically connected to the plurality of individual driving electrodes are exposed from the insulating protective film on the surface side on which the plurality of individual terminal electrodes are formed. To form.

In (Aspect A), when discharging the discharge electrodes disposed opposite to the surface side where the plurality of individual terminal electrodes and the plurality of dummy individual terminal electrodes of the electromechanical conversion member are exposed, the individual terminal electrodes and the dummy individual terminal electrodes Electric charges are supplied to the individual drive electrodes via the. At this time, even if the amount of charge supplied via the plurality of individual terminal electrodes is non-uniform, the individual drive electrodes are provided via the dummy individual terminal electrodes so that the charges supplied to the plurality of individual drive electrodes are uniform. Charge is supplied to the plurality of electromechanical conversion elements to perform polarization processing.
For example, when the polarization process is performed by the discharge of the discharge electrodes facing a plurality of individual terminal electrodes arranged in a row, the charge is concentrated at the end of the row and the charge supplied to the individual terminal electrode becomes excessive. In other regions, the charge supplied to the individual terminal electrode is insufficient. Therefore, the plurality of dummy individual terminal electrodes are formed by adjusting the size, arrangement, and the like so that less charge is supplied at the end of the column and more charge is supplied in other regions.
That is, when a plurality of electromechanical conversion films are collectively polarized by discharging the discharge electrodes, the charge supplied to the individual drive electrodes only through the individual terminal electrodes is in a non-uniform state. . However, in this aspect, even if the charge supplied through the individual terminal electrode is non-uniform, by supplying the charge for correcting the non-uniformity through the dummy individual terminal electrode to the individual drive electrode, The charge supplied to the drive electrode can be made uniform.
A plurality of electromechanical conversion films are collectively formed by the electric field generated in the electromechanical conversion film sandwiched between the individual drive electrode supplied with the uniform charge and the drive electrode opposite to the individual drive electrode. Uniform polarization treatment is possible.
In addition, since this polarization treatment is performed after the formation of the insulating protective film and the wiring / terminal electrodes with high-temperature heat treatment, it is possible to prevent depolarization due to the influence of the thermal history in the subsequent process, enabling stable polarization treatment. Become.

(Aspect B)
In the above (Aspect A), the plurality of individual terminal electrodes such as the individual electrode pad 21 and the plurality of dummy individual terminal electrodes such as the dummy individual electrode pad 24 are arranged side by side in the same predetermined direction, and end in the predetermined direction The area of the dummy individual terminal electrode (such as dummy individual electrode pad 24b) located in the portion is smaller than the area of the other dummy individual terminal electrode (such as dummy individual electrode pad 24a).
As described in the above embodiment, the charge supplied to the individual drive electrodes via the individual terminal electrodes arranged in a predetermined direction increases at the end portions. Therefore, the area of the dummy individual terminal electrode arranged side by side in the same predetermined direction as the individual terminal electrode is made smaller than the other area at the end. By forming the dummy individual terminal electrode in this way, the electric charge supplied to the individual drive electrode located at the end via the dummy individual terminal electrode located at the end passes through the other dummy individual terminal electrode. This is less than the charge supplied to the other individual drive electrodes. As a result, non-uniformity in the amount of charge supplied to the drive electrode via the individual terminal electrode is corrected, and the charge supplied to the individual drive electrode can be made uniform.

(Aspect C)
In the above (Aspect A), the plurality of individual terminal electrodes such as the individual electrode pad 21 and the plurality of dummy individual terminal electrodes such as the dummy individual electrode pad 24 are arranged side by side in the same predetermined direction, and end in the predetermined direction A dummy individual terminal electrode (such as a dummy individual electrode pad 24 b) located in the portion is formed so as not to be exposed from the insulating protective film such as the second insulating protective film 23.
According to this, as described in the first modification, charges are supplied to the individual drive electrodes via the dummy individual terminal electrodes except for the end portions. On the other hand, since the dummy individual terminal electrode is not exposed from the insulating protective film at the end portion, no charge is supplied to the individual drive electrode via the dummy individual terminal electrode. As a result, non-uniformity in the amount of charge supplied to the drive electrode via the individual terminal electrode is corrected, and the charge supplied to the individual drive electrode can be made uniform.

(Aspect D)
In the above (Aspect A), the individual drive electrodes such as the upper electrode 163 that are arranged in a predetermined direction and in which the plurality of individual terminal electrodes such as the individual electrode pads 21 are connected to the individual terminal electrodes located at the end portions in the predetermined direction. The dummy individual terminal electrodes such as the dummy individual electrode pads 24 are not formed.
According to this, as described in the second modification, electric charges are supplied to the individual drive electrodes via the dummy individual terminal electrodes except for the end portions. On the other hand, since the dummy individual terminal electrode is not formed at the end portion, no charge is supplied to the individual drive electrode via the dummy individual terminal electrode. As a result, non-uniformity in the amount of charge supplied to the drive electrode via the individual terminal electrode is corrected, and the charge supplied to the individual drive electrode can be made uniform.

(Aspect E)
In any one of the above (Aspect A) to (Aspect D), the drive electrode is connected to a common drive electrode such as the lower electrode 161 formed to be common to the other surface side of the plurality of electromechanical conversion films. A common terminal electrode such as the common electrode pad 19 is formed so as to be exposed from the insulating protective film on the surface side on which the individual terminal electrode is formed.
According to this, each common drive electrode is supplied with electric charges to each of the common drive electrodes of the plurality of electromechanical transducer elements via the common terminal electrode by the discharge of the discharge electrode facing the surface side on which the individual terminal electrodes are formed. Can be made common to each other. Thereby, it is possible to stabilize and equalize the polarization treatment of the plurality of electromechanical transducer elements.

(Aspect F)
An electric machine such as an actuator substrate 30 such as a piezoelectric element 16 provided on a substrate forming the liquid chamber so as to be able to pressurize the liquid in the liquid chamber 13 and a liquid chamber 13 communicating with a nozzle 11 for discharging droplets. In the droplet discharge head 1 having an electromechanical conversion member provided with a conversion element, the electromechanical conversion member according to any one of (Aspect A) to (Aspect E) is used as the electromechanical conversion member.
According to this, stable droplet discharge characteristics can be obtained using an electromechanical transducer 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 above (Aspect F) is used as the droplet discharge head.
According to this, it is possible to perform image formation with stable droplet discharge characteristics using a droplet discharge head including an electromechanical conversion element having good polarization characteristics.

(Aspect H)
Connected to a plurality of electromechanical conversion elements made of an electromechanical conversion film sandwiched between a pair of drive electrodes and an individual drive electrode on the opposite side of the plurality of electromechanical conversion elements provided on the substrate. An electromechanical conversion element in an electromechanical conversion member comprising: a plurality of individual terminal electrodes; and an insulating protective film that protects the plurality of electromechanical conversion elements formed to expose the plurality of individual terminal electrodes. A polarization processing method comprising:
The plurality of individual drive electrodes are electrically connected to each of the plurality of individual drive electrodes on the surface side on which the plurality of individual terminal electrodes are formed so that the charges supplied to the plurality of individual drive electrodes are uniform. A plurality of dummy individual terminal electrodes for supplying the discharge are formed so as to be exposed from the insulating protective film, and the discharge is generated by the discharge electrodes arranged to face the surface on which the plurality of individual terminal electrodes are formed. Thus, electric charges are supplied to the individual terminal electrode and the dummy individual terminal electrode to polarize the electromechanical conversion film.
According to this, as described in the above embodiment, the charges supplied to the individual drive electrodes can be made uniform by supplying the charges to the individual drive electrodes via the individual terminal electrodes and the dummy individual terminal electrodes. Thereby, an electric field of uniform polarization processing is generated in the electromechanical conversion film, and a plurality of piezoelectric elements can be uniformly polarized at once.
In addition, since this polarization treatment is performed after the formation of the insulating protective film and the wiring / terminal electrodes with high-temperature heat treatment, it is possible to prevent depolarization due to the influence of the thermal history in the subsequent process, enabling stable polarization treatment. Become.

(Aspect I)
In (Aspect H), the discharge by the discharge electrode is corona discharge or glow discharge.
According to this, as described in the above embodiment, a discharge for polarization treatment can be generated in the atmosphere with a simple device configuration. In addition, by changing the voltage and frequency, the charge injection amount by discharge can be easily controlled.

(Aspect J)
In (Aspect H) or (Aspect I), the charge generated by the discharge is a positive charge.
According to this, as described in the above embodiment, positively charged cations can be easily generated by ionizing molecules in the atmosphere by discharge. This cation flows into the electromechanical conversion film through the common terminal electrode, the individual terminal electrode, and the dummy individual terminal electrode, so that the positively charged charge can be easily accumulated in the electromechanical conversion film. Therefore, the polarization treatment of the electromechanical conversion film can be performed stably.

(Aspect K)
A manufacturing method for manufacturing the electromechanical conversion member according to any one of (Aspect A) to (Aspect E),
Forming a common drive electrode on a substrate or on a base film formed on the substrate;
Forming a plurality of independent electromechanical conversion films on the common drive electrode;
Forming a plurality of individual drive electrodes positioned on each of the plurality of electromechanical conversion films;
Forming a first insulating protective film on the common drive electrode and the plurality of individual drive electrodes;
A common terminal electrode connected to the common drive electrode via a first wiring, and a plurality of individual terminals connected to each of the plurality of individual drive electrodes via a second wiring and arranged in a predetermined direction A terminal electrode and a plurality of dummy individual terminal electrodes connected to each of the plurality of individual drive electrodes via a third wiring and arranged in a predetermined direction are formed on the first insulating protective film. And a process of
Second insulation protection on the first wiring, the second wiring, and the third wiring with the common terminal electrode, the plurality of individual terminal electrodes, and the plurality of dummy individual terminal electrodes exposed. Forming a film;
Supplying the electric charge generated by the discharge to the common terminal electrode, the plurality of individual terminal electrodes, and the plurality of dummy individual terminal electrodes to collectively polarize the plurality of electromechanical conversion films; Including.
According to this, as described in the above embodiment, an electromechanical conversion member including an electromechanical conversion element having good polarization characteristics can be obtained.

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 161 Lower electrode (common drive electrode)
162 Piezoelectric film (electromechanical conversion film)
163 Upper electrode (individual drive electrode)
18 1st insulating protective film 18a, 18b, 18c Contact hole 19 Common electrode pad (common terminal electrode)
20 First wiring 21 Individual electrode pad (individual terminal electrode)
22 Second wiring 23 Second insulating protective film 23a Opening (for common electrode pad)
23a Opening (for individual electrode pads)
23a Opening (for dummy individual electrode pad)
24 Dummy individual electrode pad (Dummy individual terminal electrode)
24a Dummy individual electrode pad 24b at the center portion Dummy individual electrode pad 25 at the end portion Third wiring 30 Actuator substrate 50 Corona discharge device 52 Corona wire electrode 53 Stage 100 Inkjet recording device

JP 2006-203190 A

Claims (11)

A plurality of electromechanical conversion elements each made of an electromechanical conversion film sandwiched between a pair of drive electrodes, and an individual drive electrode formed on one surface side of the plurality of electromechanical conversion films among the drive electrodes, respectively. Electromechanical conversion member comprising a plurality of individual terminal electrodes connected to each other and an insulating protective film that protects the plurality of electromechanical conversion elements formed so that the plurality of individual terminal electrodes are exposed, respectively.
A plurality of dummy individual terminal electrodes respectively electrically connected to the plurality of individual drive electrodes are formed on the surface side on which the plurality of individual terminal electrodes are formed so as to be exposed from the insulating protective film. An electromechanical conversion member.   The electromechanical conversion member according to claim 1, wherein the plurality of individual terminal electrodes and the plurality of dummy individual terminal electrodes are arranged side by side in the same predetermined direction, and are located at the end in the predetermined direction. An electromechanical conversion member characterized in that the area of is smaller than the area of other dummy individual terminal electrodes.   The electromechanical conversion member according to claim 1, wherein the plurality of individual terminal electrodes and the plurality of dummy individual terminal electrodes are arranged side by side in the same predetermined direction, and are located at the end in the predetermined direction. However, the electromechanical conversion member is formed so as not to be exposed from the insulating protective film.   2. The electromechanical conversion member according to claim 1, wherein the plurality of individual terminal electrodes are arranged in a predetermined direction, and the individual driving electrode connected to the individual terminal electrode located at an end portion in the predetermined direction has the dummy individual terminal. An electromechanical conversion member characterized in that no electrode is formed.   5. The electromechanical conversion member according to claim 1, wherein the drive electrode is connected to a common drive electrode formed to be common to the other surface side of the plurality of electromechanical conversion films. The electromechanical conversion member, wherein the common terminal electrode is formed so as to be exposed from the insulating protective film on a surface side on which the individual terminal electrode is formed. A liquid chamber that communicates with a nozzle that discharges droplets; and an electromechanical conversion member that includes an electromechanical conversion element provided on a substrate that forms the liquid chamber so that the liquid in the liquid chamber can be pressurized. In the droplet discharge head,
6. A liquid droplet ejection head using the electromechanical conversion member according to claim 1 as the electromechanical conversion member. In an image forming apparatus that forms an image by discharging droplets from a droplet discharge head,
An image forming apparatus using the droplet discharge head according to claim 6 as the droplet discharge head. Connected to a plurality of electromechanical conversion elements made of an electromechanical conversion film sandwiched between a pair of drive electrodes and an individual drive electrode on the opposite side of the plurality of electromechanical conversion elements provided on the substrate. An electromechanical conversion element in an electromechanical conversion member comprising: a plurality of individual terminal electrodes; and an insulating protective film that protects the plurality of electromechanical conversion elements formed to expose the plurality of individual terminal electrodes. A polarization processing method comprising:
The plurality of individual drive electrodes are electrically connected to each of the plurality of individual drive electrodes on the surface side on which the plurality of individual terminal electrodes are formed so that the charges supplied to the plurality of individual drive electrodes are uniform. A plurality of dummy individual terminal electrodes for supplying the discharge are formed so as to be exposed from the insulating protective film, and the discharge is generated by the discharge electrodes arranged to face the surface on which the plurality of individual terminal electrodes are formed. The method for polarizing an electromechanical transducer element, comprising: supplying charges to the individual terminal electrode and the dummy individual terminal electrode to polarize the electromechanical conversion film.   9. The method for polarizing an electromechanical transducer according to claim 8, wherein the discharge by the discharge electrode is corona discharge or glow discharge.   10. The method for polarizing an electromechanical transducer according to claim 8, wherein the electric charge generated by the discharge is a positive charge. A manufacturing method for manufacturing the electromechanical conversion member according to any one of claims 1 to 5,
Forming a common drive electrode on a substrate or on a base film formed on the substrate;
Forming a plurality of independent electromechanical conversion films on the common drive electrode;
Forming a plurality of individual drive electrodes positioned on each of the plurality of electromechanical conversion films;
Forming a first insulating protective film on the common drive electrode and the plurality of individual drive electrodes;
A common terminal electrode connected to the common drive electrode via a first wiring, and a plurality of individual terminals connected to each of the plurality of individual drive electrodes via a second wiring and arranged in a predetermined direction A terminal electrode and a plurality of dummy individual terminal electrodes connected to each of the plurality of individual drive electrodes via a third wiring and arranged in a predetermined direction are formed on the first insulating protective film. And a process of
Second insulation protection on the first wiring, the second wiring, and the third wiring with the common terminal electrode, the plurality of individual terminal electrodes, and the plurality of dummy individual terminal electrodes exposed. Forming a film;
Supplying the electric charge generated by the discharge to the common terminal electrode, the plurality of individual terminal electrodes, and the plurality of dummy individual terminal electrodes to collectively polarize the plurality of electromechanical conversion films; An electromechanical conversion member manufacturing method comprising:

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