Patent Description:
The present disclosure relates to a piezoelectric actuator and a manufacturing method of the piezoelectric actuator, a liquid droplet discharge head, and an ultrasonic device.

In the related art, for example, as disclosed in <CIT>, there has been known a liquid droplet discharge head that includes, on a first conductive layer (lower electrode) that is individually patterned, a piezoelectric layer covering the first conductive layer and a second conductive layer covering the piezoelectric layer.

In <CIT>, after a metal film is formed on a vibrating plate, etching is performed to form the lower electrode that is individually patterned, and then the piezoelectric layer that covers the lower electrode is formed. In such a manufacturing method, when a component of an etching solution or a resist remains on the lower electrode in patterning the lower electrode, a defect may occur in the piezoelectric layer formed on the lower electrode, which may cause a decrease in yield. In addition, orientation of a piezoelectric body crystal-growing from a top surface of the vibrating plate and orientation of a piezoelectric body crystal-growing from a top surface of the lower electrode may be different from each other, and cracks may be generated in the piezoelectric layer around an end edge portion of the lower electrode, or a portion in which the crystal orientation is disturbed may be formed.

<CIT> discloses a droplet discharge head which includes: a nozzle plate having a plurality of nozzle holes discharging a liquid; a liquid chamber formation substrate in which a pressure liquid chambers communicating with the nozzle holes are formed; a piezoelectric actuator in which a lower electrode, a piezoelectric layer for increasing pressure inside the pressure liquid chamber, and an upper electrode are sequentially formed on a diaphragm which constitutes a part of the pressure liquid chamber. The lower electrodes, divided for each pressure liquid chamber, are individual electrodes in which a driving voltage for driving the piezoelectric actuator is applied to each pressure liquid chamber, and the upper electrodes, conducting to each other, are common electrodes. A divided part of the lower electrodes are outside of a vibration area of the diaphragm.

According to a first aspect of the present invention, there is provided a piezoelectric actuator according to claim <NUM>.

According to a second aspect of the present invention, there is provided a manufacturing method according to claim <NUM>.

According to a third aspect of the present invention, there is provided a liquid droplet discharge head according to claim <NUM>.

According to a fourth aspect of the present invention, there is provided an ultrasonic device according to claim <NUM>.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The following description shows an aspect of the present disclosure, and can be freely changed within the scope of the present disclosure. In the drawings, members denoted by the same reference signs indicate the same members, and a description thereof is omitted appropriately. In the drawings, X, Y, and Z represent three spatial axes orthogonal to each other. In the present specification, directions along these axes will be described as an X-axis direction, a Y-axis direction, and a Z-axis direction, respectively. The Z-axis direction represents a thickness direction or a lamination direction of a plate, a layer, and a film. The X-axis direction and the Y-axis direction represent in-plane directions of a plate, a layer, and a film.

A liquid droplet discharge head according to the embodiment will be described with reference to the drawings.

<FIG> is an exploded perspective view schematically illustrating the liquid droplet discharge head of the embodiment. <FIG> is a partial plan view schematically illustrating a piezoelectric actuator provided in the liquid droplet discharge head of the embodiment. <FIG> is a cross-sectional view taken along a line III-III in <FIG>. <FIG> is a cross-sectional view taken along a line IV-IV in <FIG>.

As illustrated in <FIG>, a liquid droplet discharge head <NUM> includes a plurality of piezoelectric devices <NUM>, a channel substrate <NUM>, a nozzle plate <NUM>, a vibrating plate <NUM>, a protective substrate <NUM>, a circuit substrate <NUM>, and a compliance substrate <NUM>. <FIG> shows an upper surface of the vibrating plate <NUM>. In the embodiment, the plurality of piezoelectric devices <NUM> are arranged side by side along the X-axis direction. The vibrating plate <NUM> and the plurality of piezoelectric devices <NUM> constitute a piezoelectric actuator <NUM> of the embodiment, and the details will be described later.

The channel substrate <NUM> is, for example, a silicon substrate. The channel substrate <NUM> is provided with a plurality of pressure chambers <NUM>. The plurality of pressure chambers <NUM> are arranged side by side along the X-axis direction. The pressure chambers <NUM> are partitioned by a plurality of partition walls <NUM>. A volume of the pressure chamber <NUM> is changed by movement of the piezoelectric device <NUM>.

In the channel substrate <NUM>, a first communication passage <NUM> and a second communication passage <NUM> are provided at an end of each pressure chamber <NUM> in a +Y-axis direction. The first communication passage <NUM> is configured such that an opening area thereof is reduced by narrowing the end of the pressure chamber <NUM> in the +Y-axis direction from the X-axis direction. A width of the second communication passage <NUM> in the X-axis direction is, for example, the same as a width of the pressure chamber <NUM> in the X-axis direction. A third communication passage <NUM> communicating with the plurality of second communication passages <NUM> is provided in the +Y-axis direction of the second communication passage <NUM>. The third communication passage <NUM> constitutes a part of a manifold <NUM>. The manifold <NUM> serves as a common liquid chamber for the pressure chambers <NUM>. As described above, the channel substrate <NUM> is provided with a supply channel <NUM> and the pressure chambers <NUM>. The supply channel <NUM> includes the first communication passages <NUM>, the second communication passages <NUM>, and the third communication channel <NUM>. The supply channel <NUM> communicates with the pressure chamber <NUM> and supplies a liquid to the pressure chamber <NUM>.

The nozzle plate <NUM> is attached to a surface of the channel substrate <NUM> on one side. A material of the nozzle plate <NUM> is, for example, steel use stainless (SUS). The nozzle plate <NUM> is bonded to the channel substrate <NUM> by an adhesive, a thermal welding film, or the like. The nozzle plate <NUM> is provided with a plurality of nozzles <NUM> arranged side by side along the X-axis direction. The nozzle <NUM> communicates with the inside of the pressure chamber <NUM>. From the nozzle <NUM>, a liquid is discharged.

The vibrating plate <NUM> is provided at a surface of the channel substrate <NUM> on the other side. The vibrating plate <NUM> includes, for example, a silicon oxide layer <NUM> provided on the channel substrate <NUM> and a zirconium oxide layer <NUM> provided on the silicon oxide layer <NUM>. The vibrating plate <NUM> may be a single layer of the silicon oxide layer or a single layer of the zirconium oxide layer. A thickness of the vibrating plate <NUM> is, for example, <NUM> or more and <NUM> or less.

The piezoelectric device <NUM> is provided on the vibrating plate <NUM>. A plurality of piezoelectric devices <NUM> are provided. The number of piezoelectric devices <NUM> is not particularly limited. As illustrated in <FIG>, the piezoelectric device <NUM> includes a lower electrode <NUM>, a piezoelectric body <NUM>, and an upper electrode <NUM>.

The lower electrode <NUM> is provided on the vibrating plate <NUM>. The lower electrode <NUM> is provided between the vibrating plate <NUM> and the piezoelectric body <NUM>. A thickness of the lower electrode <NUM> is, for example, <NUM> or more and <NUM> or less. The lower electrode <NUM> is, for example, a metal layer such as a platinum layer, an iridium layer, a titanium layer, or a ruthenium layer, a conductive oxide layer thereof, a lanthanum nickel oxide (LaNiO<NUM>: LNO) layer, or a strontium ruthenium oxide (SrRuO<NUM>: SRO) layer. The lower electrode <NUM> may have a structure in which a plurality of layers exemplified above are laminated.

In the liquid droplet discharge head <NUM>, the lower electrode <NUM> is configured as an independent individual electrode for each pressure chamber <NUM>. As illustrated in <FIG>, a width of the lower electrode <NUM> in the X-axis direction is smaller than the width of the pressure chamber <NUM> in the X-axis direction. As illustrated in <FIG>, a length of the lower electrode <NUM> in the Y-axis direction is larger than a length of the pressure chamber <NUM> in the Y-axis direction. In the Y-axis direction, both ends of the lower electrode <NUM> are located to sandwich both ends of the pressure chamber <NUM>. A lead electrode <NUM> is coupled to an end of the lower electrode <NUM> in a -Y-axis direction.

The piezoelectric body <NUM> is provided on the lower electrode <NUM>. The piezoelectric body <NUM> is provided between the lower electrode <NUM> and the upper electrode <NUM>. In the embodiment, the piezoelectric body <NUM> is provided on the lower electrode <NUM> and the vibrating plate <NUM>. A thickness of the piezoelectric body <NUM> is, for example, <NUM> or more and <NUM> or less. The piezoelectric body <NUM> can be deformed by applying a voltage between the lower electrode <NUM> and the upper electrode <NUM>.

A width of the piezoelectric body <NUM> in the X-axis direction is smaller than the width of the lower electrode <NUM> in the X-axis direction. A length of the piezoelectric body <NUM> in the Y-axis direction is larger than the length of the pressure chamber <NUM> in the Y-axis direction and smaller than the length of the lower electrode <NUM> in the Y-axis direction. The piezoelectric body <NUM> is formed only on an upper surface of the lower electrode <NUM>. That is, the piezoelectric body <NUM> does not cover a side surface of the lower electrode <NUM>.

The piezoelectric body <NUM> is implemented by a piezoelectric material made of a complex oxide having a perovskite structure represented by a general formula ABO<NUM>. In the embodiment, lead zirconate titanate (PZT; Pb(Zr,Ti)O<NUM>) is used as the piezoelectric material. By using PZT as the piezoelectric material, the piezoelectric body <NUM> having a relatively large piezoelectric constant d31 is obtained.

In the complex oxide having a perovskite structure represented by the general formula ABO<NUM>, oxygen is <NUM>-coordinated at an A site and oxygen is <NUM>-coordinated at a B site to form an octahedron. In the embodiment, lead (Pb) is located at the A site, and zirconium (Zr) and titanium (Ti) are located at the B site.

The piezoelectric material is not limited to PZT described above. Other elements may be contained in the A site or the B site. For example, the piezoelectric material may be a perovskite material such as barium zirconate titanate (Ba(Zr,Ti)O<NUM>), lead lanthanum zirconate titanate ((Pb, La)(Zr,Ti)O<NUM>), lead zirconium titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O<NUM>), or lead zirconate titanate niobate (Pb(Zr,Ti,Nb)O<NUM>) containing silicon.

In addition, the piezoelectric material may be a material in which the content of Pb is reduced, that is, a so-called low-lead material, or a material in which Pb is not used, that is, a so-called lead-free material. When a low-lead material is used as the piezoelectric material, the amount of Pb used can be reduced. In addition, when a lead-free material is used as the piezoelectric material, Pb does not need to be used. Therefore, an impact on the environment can be reduced by using a low-lead material or a lead-free material as the piezoelectric material.

Examples of the lead-free piezoelectric material include BFO-based materials containing bismuth ferrate (BFO; BiFeO<NUM>). In BFO, Bi is located at an A site, and iron (Fe) is located at a B site. Other elements may be added to BFO. For example, at least one element selected from manganese (Mn), aluminum (Al), lanthanum (La), barium (Ba), titanium (Ti), cobalt (Co), cerium (Ce), samarium (Sm), chromium (Cr), potassium (K), lithium (Li), calcium (Ca), strontium (Sr), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), nickel (Ni), zinc (Zn), praseodymium (Pr), neodymium (Nd), and europium (Eu) may be added to KNN.

Another example of the lead-free piezoelectric material includes a KNN-based material containing potassium sodium niobate (KNN; KNaNbO<NUM>). Other elements may be added to KNN. For example, at least one element selected from manganese (Mn), lithium (Li), barium (Ba), calcium (Ca), strontium (Sr), zirconium (Zr), titanium (Ti), bismuth (Bi), tantalum (Ta), antimony (Sb), iron (Fe), cobalt (Co), argentum (Ag), magnesium (Mg), zinc (Zn), copper (Cu), vanadium (V), chromium (Cr), molybdenum (Mo), tungsten (W), nickel (Ni), aluminum (Al), silicon (Si), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu) may be added to KNN.

The piezoelectric material includes a material having a composition in which a part of an element is deficient, a material having a composition in which a part of an element is excessive, and a material having a composition in which a part of an element is substituted with another element. As long as basic characteristics of the piezoelectric body <NUM> do not change, a material deviated from the stoichiometric composition due to deficiency or excess, or a material in which a part of an element is substituted with another element also falls within the piezoelectric material according to the embodiment. Of course, the piezoelectric material that can be used in the embodiment is not limited to a material containing Pb, Bi, Na, K, or the like as described above.

The upper electrode <NUM> is provided on the piezoelectric body <NUM>. In the embodiment, the upper electrode <NUM> is formed only on an upper surface of the piezoelectric body <NUM>. That is, the upper electrode <NUM> does not cover a side surface of the piezoelectric body <NUM> or a side surface of the lower electrode <NUM>. The upper electrode <NUM> is provided as an independent individual electrode for each piezoelectric device <NUM>. A thickness of the upper electrode <NUM> is, for example, <NUM> or more and <NUM> or less. The upper electrode <NUM> is, for example, a metal layer such as an iridium layer, a platinum layer, a titanium layer, or a ruthenium layer, a conductive oxide layer thereof, a lanthanum nickel oxide layer, or a strontium ruthenium oxide layer. The upper electrode <NUM> may have a structure in which a plurality of layers exemplified above are laminated.

The piezoelectric device <NUM> may not include the upper electrode <NUM>. That is, the piezoelectric body <NUM> may be directly coupled to a common electrode <NUM> to be described later. In this case, it is preferable to select a conductive material having excellent adhesion to the piezoelectric body <NUM> as a constituent material of the common electrode <NUM>.

When the upper electrode <NUM> is provided as in the embodiment, the upper electrode <NUM> can also function as an adhesion layer between the piezoelectric body <NUM> and the common electrode <NUM>. The constituent material of the common electrode <NUM> is less limited, and a conductive material having a low resistance can be easily used.

As illustrated in <FIG> and <FIG>, an insulating layer <NUM> is formed on the vibrating plate <NUM> so as to partially cover a laminated body of the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM>. The insulating layer <NUM> is a layer made of, for example, aluminum oxide, silicon oxide, silicon nitride, or zirconium oxide. The insulating layer <NUM> may have a structure in which a plurality of layers exemplified above are laminated.

In the case of the embodiment, the insulating layer <NUM> covers side surfaces of the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM>. The insulating layer <NUM> has openings penetrating the insulating layer <NUM> in a thickness direction at a plurality of positions on the piezoelectric device <NUM>. Specifically, the insulating layer <NUM> includes a contact hole <NUM>, a contact hole <NUM>, and an opening <NUM>.

The contact hole <NUM> is opened in the insulating layer <NUM> on the lower electrode <NUM> that protrudes in the -Y-axis direction from a lower end of the piezoelectric body <NUM>. The contact hole <NUM> is opened in the insulating layer <NUM> located on an end portion of the upper electrode <NUM> in the +Y-axis direction. The opening <NUM> is opened in the insulating layer <NUM> located in a region where the upper electrode <NUM> and the pressure chamber <NUM> overlap each other in a plan view (viewed in the Z-axis direction).

The lead electrode <NUM> partially overlapping with the lower electrode <NUM> in a plan view is formed at an end portion of each piezoelectric device <NUM> in the -Y-axis direction. The lead electrode <NUM> and the lower electrode <NUM> are electrically coupled to each other via the contact hole <NUM>.

The common electrode <NUM> extending in the X-axis direction across the plurality of piezoelectric devices <NUM> is formed at end portions of the plurality of piezoelectric devices <NUM> in the +Y-axis direction. The common electrode <NUM> overlaps a region including the contact hole <NUM> of each piezoelectric device <NUM> in a plan view. The common electrode <NUM> is electrically coupled to the upper electrode <NUM> via the contact hole <NUM>.

The opening <NUM> is provided in a portion of the insulating layer <NUM> that is located on the pressure chamber <NUM>. By partially removing the insulating layer <NUM> that is harder than the constituent layers of the piezoelectric device <NUM>, it is possible to improve deformation performance of the piezoelectric device <NUM>. The insulating layer <NUM> may not include the opening <NUM>.

In the embodiment, the opening <NUM> is in a planar region of the upper electrode <NUM>, and a peripheral edge portion of the upper electrode <NUM> is covered with the insulating layer <NUM>. The insulating layer <NUM> is formed continuously from the peripheral edge portion of the upper electrode <NUM> to the side surface of the piezoelectric device <NUM>. According to this configuration, since a top surface of the piezoelectric body <NUM> is not exposed to the outside air, it is possible to prevent entry of moisture or the like into the piezoelectric body <NUM>, and it is possible to prevent deterioration of the piezoelectric device <NUM> caused by moisture or the like.

In the piezoelectric device <NUM>, by applying a voltage between the lower electrode <NUM> and the upper electrode <NUM>, it is possible to apply a voltage to the piezoelectric body <NUM> and deform the piezoelectric body <NUM>. In the embodiment, the piezoelectric device <NUM> and the vibrating plate <NUM> constitute the piezoelectric actuator <NUM> that changes the volume of the pressure chamber <NUM>. The vibrating plate <NUM> constitutes a substrate of the piezoelectric actuator <NUM>.

In the liquid droplet discharge head <NUM>, the vibrating plate <NUM> and the lower electrode <NUM> are displaced by deformation of the piezoelectric body <NUM> having electromechanical conversion characteristics. That is, in the liquid droplet discharge head <NUM>, the vibrating plate <NUM> and the lower electrode <NUM> substantially function as a vibrating plate.

In the piezoelectric actuator <NUM> of the embodiment, as illustrated in <FIG>, the plurality of piezoelectric devices <NUM> are formed as independent individual devices on the vibrating plate <NUM>. Hereinafter, a first piezoelectric device 300A and a second piezoelectric device 300B illustrated in the drawings will be specifically described. The first piezoelectric device 300A and the second piezoelectric device 300B are two piezoelectric devices <NUM> having a common configuration, and are distinguished from each other for convenience of description.

The first piezoelectric device 300A includes a first lower electrode 60A formed on the vibrating plate <NUM> (substrate), a first piezoelectric body 70A formed on the first lower electrode 60A, and a first upper electrode 80A formed on the first piezoelectric body 70A.

The second piezoelectric device 300B includes a second lower electrode 60B formed in a region different from that of the first lower electrode 60A on the vibrating plate <NUM> (substrate), a second piezoelectric body 70B formed on the second lower electrode 60B, and a second upper electrode 80B formed on the second piezoelectric body 70B.

A side surface of the first lower electrode 60A of the first piezoelectric device 300A is not covered with the first piezoelectric body 70A. A side surface of the second lower electrode 60B of the second piezoelectric device 300B is not covered with the second piezoelectric body 70B. The piezoelectric actuator <NUM> includes the common electrode <NUM> that is formed on the vibrating plate <NUM> and that is coupled to the first upper electrode 80A and the second upper electrode 80B. The piezoelectric actuator <NUM> includes the insulating layer <NUM> located between the common electrode <NUM> and the first lower electrode 60A and between the common electrode <NUM> and the second lower electrode 60B.

According to this configuration, the first piezoelectric body 70A is formed only on the first lower electrode 60A, and the second piezoelectric body 70B is formed only on the second lower electrode 60B. Therefore, it is possible to prevent the first piezoelectric body 70A and the second piezoelectric body 70B from suffering from cracks and orientation disturbances that are likely to occur on end edges of the first lower electrode 60A and the second lower electrode 60B. In this configuration, the side surface of the first lower electrode 60A is exposed between the first piezoelectric body 70A and the vibrating plate <NUM>, and the side surface of the second lower electrode 60B is exposed between the second piezoelectric body 70B and the vibrating plate <NUM>. Therefore, by providing the insulating layer <NUM> that covers the side surface of the first lower electrode 60A and the side surface of the second lower electrode 60B, the common electrode <NUM> formed on the vibrating plate <NUM> can be electrically coupled to the first upper electrode 80A and the second upper electrode 80B without causing a short circuit to the first lower electrode 60A and the second lower electrode 60B.

Although the insulating layer <NUM> covers an entire side surface of the piezoelectric body <NUM> in the embodiment, the present disclosure is not limited to this configuration. If the insulating layer <NUM> is formed at least between the side surface of the lower electrode <NUM> and the common electrode <NUM>, a short circuit between the common electrode <NUM> and the lower electrode <NUM> can be prevented. Therefore, the insulating layer <NUM> may be formed only on a part of the side surface of the lower electrode <NUM>. The insulating layer <NUM> covers the side surface of the lower electrode <NUM>, and may not cover the side surface of the piezoelectric body <NUM>.

When the insulating layer <NUM> does not cover the side surface of the piezoelectric body <NUM>, the piezoelectric actuator <NUM> may include a protective film that covers the side surface of the piezoelectric body <NUM> (the first piezoelectric body 70A and the second piezoelectric body 70B). As the protective film, for example, a nitride such as titanium nitride, silicon nitride, aluminum nitride, or TiAlN, an oxide such as aluminum oxide, titanium oxide, tantalum oxide, chromium oxide, iridium oxide, or hafnium oxide, a resin-based material such as parylene, an adhesive, or a photosensitive resist, or a carbon-based material such as diamond-like carbon can be used. By providing the protective film that covers the piezoelectric body <NUM>, it is possible to effectively prevent entry of moisture into the piezoelectric body <NUM>.

The protective substrate <NUM> is bonded to the vibrating plate <NUM> by an adhesive (not illustrated). The protective substrate <NUM> has a through hole <NUM> penetrating the protective substrate <NUM> in a thickness direction thereof (Z-axis direction). The through hole <NUM> communicates with the third communication passage <NUM> via a through hole provided in the vibrating plate <NUM>. The through hole <NUM> and the third communication passage <NUM> constitute the manifold <NUM> that serves as a common liquid chamber of the pressure chambers <NUM>. The protective substrate <NUM> has another through hole <NUM> penetrating the protective substrate <NUM> in the Z-axis direction. An end of the lead electrode <NUM> is disposed in the through hole <NUM>. The protective substrate <NUM> has an opening <NUM> that is open to the vibrating plate <NUM>. The opening <NUM> is a space for not obstructing driving of the piezoelectric device <NUM>. The opening <NUM> may be sealed or may not be sealed. The circuit substrate <NUM> is provided on the protective substrate <NUM>. The circuit substrate <NUM> includes a semiconductor integrated circuit (IC) for driving the piezoelectric device <NUM>. The circuit substrate <NUM> and the lead electrode <NUM> are electrically coupled to each other via a coupling wiring (not illustrated). The compliance substrate <NUM> is provided on the protective substrate <NUM>. The compliance substrate <NUM> includes a sealing layer <NUM> provided on the protective substrate <NUM> and a fixing plate <NUM> provided on the sealing layer <NUM>. The sealing layer <NUM> seals an upper opening of the through hole <NUM>. The sealing layer <NUM> seals the manifold <NUM>. The sealing layer <NUM> has, for example, flexibility. The fixing plate <NUM> has a through hole <NUM> penetrating the fixing plate <NUM> in the Z-axis direction. The through hole <NUM> overlaps with the manifold <NUM> as viewed from the Z-axis direction.

In the liquid droplet discharge head <NUM> of the embodiment, ink is taken in from an ink introduction port continuous to an external ink supply device (not illustrated), an inside of the liquid droplet discharge head <NUM> is filled with ink from the manifold <NUM> to the nozzle <NUM>, and then a voltage is applied between the lower electrode <NUM> and the upper electrode <NUM> that are corresponding to each pressure chamber <NUM> in accordance with a recording signal from a drive circuit. Accordingly, the vibrating plate <NUM> is bent and deformed together with the piezoelectric device <NUM>, a pressure in each pressure chamber <NUM> is increased, and ink droplets are ejected from the nozzles <NUM>.

In the embodiment, the common electrode <NUM> overlaps only the end portion of the piezoelectric device <NUM>. That is, the common electrode <NUM> is disposed in a region that does not overlap the pressure chamber <NUM> in a plan view. With such a configuration, since the common electrode <NUM> is not disposed in a region where the vibrating plate <NUM> is displaced by the piezoelectric device <NUM>, deformation of the piezoelectric device <NUM> is not obstructed by the common electrode <NUM>, and a large displacement amount can be obtained.

The configuration of the common electrode <NUM> according to the invention is different from this example, and is shown on <FIG>. As illustrated in <FIG>, the common electrode <NUM> covers the piezoelectric body <NUM>. In the configuration illustrated in <FIG>, the common electrode <NUM> is also formed on the opening <NUM> of the insulating layer <NUM>. In this example, the common electrode <NUM> and the upper electrode <NUM> are electrically coupled to each other at two positions, that is, the contact hole <NUM> and the opening <NUM>. Any one of the contact hole <NUM> and the opening <NUM> may not be provided.

As illustrated in <FIG>, since the common electrode <NUM> covers the piezoelectric body <NUM>, it is possible to further prevent entry of moisture or the like into the piezoelectric body <NUM>. In particular, in a configuration in which the side surface of the piezoelectric body <NUM> is not covered with the insulating layer <NUM>, the common electrode <NUM> can also function as a protective film, and reliability of the piezoelectric actuator <NUM> can be improved.

The configuration illustrated in <FIG> is suitable for a case where the piezoelectric device <NUM> is not provided with the upper electrode <NUM>. In a configuration in which the upper electrode <NUM> is not provided, when the common electrode <NUM> covering the piezoelectric body <NUM> is formed, the common electrode <NUM> functions as the upper electrode of each piezoelectric device <NUM>.

The lead electrode <NUM> and the common electrode <NUM> need to be insulated from each other. Therefore, the common electrode <NUM> may not cover the piezoelectric body <NUM> in the vicinity of the lead electrode <NUM>. In the example illustrated in <FIG>, of the side surfaces of the piezoelectric body <NUM>, a side surface facing a lead electrode <NUM> side (-Y-axis direction) is not covered with the common electrode <NUM>. However, since an end portion of the piezoelectric body <NUM> located in the vicinity of the lead electrode <NUM> is a portion that does not overlap the pressure chamber <NUM> in a plan view, the end portion hardly contributes to a vibration operation of the vibrating plate <NUM>. Therefore, even if some moisture enters the piezoelectric body <NUM> in the vicinity of the lead electrode <NUM>, the performance of the piezoelectric device <NUM> is not affected. That is, the common electrode <NUM> may cover at least a portion of the piezoelectric body <NUM> overlapping the pressure chamber <NUM> in a plan view.

In the embodiment, the lead electrode <NUM> and the lower electrode <NUM> are coupled to each other via the contact hole <NUM>, but the present disclosure is not limited to this configuration. For example, a configuration illustrated in <FIG> may be employed. In the example illustrated in <FIG>, the lower electrode <NUM> includes a wiring portion 60a that extends to greatly protrude in the -Y-axis direction with respect to the piezoelectric body <NUM>. The wiring portion 60a of the lower electrode <NUM> is not covered with the insulating layer <NUM>. The lead electrode <NUM> is formed in contact with an upper surface of the wiring portion 60a of the lower electrode <NUM>. With such a configuration, a contact area between the lower electrode <NUM> and the lead electrode <NUM> can be increased. Accordingly, reliability of electrical coupling between the lead electrode <NUM> and the lower electrode <NUM> can be improved, and an electrical resistance of a wiring coupled to the piezoelectric device <NUM> can be reduced.

<FIG> are cross-sectional views illustrating a manufacturing method of the liquid droplet discharge head of the above embodiment. Cross sections shown in the drawings are cross sections at a position along a line XI-XI in <FIG>.

First, a silicon substrate W1 illustrated in <FIG> is prepared.

Next, the vibrating plate <NUM> is formed on a top surface of the silicon substrate W1. In forming the vibrating plate <NUM>, first, the silicon substrate W1 is thermally oxidized to form the silicon oxide layer <NUM> made of silicon dioxide.

Next, the zirconium oxide layer <NUM> made of zirconium oxide (ZrOx) is formed on the silicon oxide layer <NUM> by a liquid phase method. In forming the zirconium oxide layer <NUM>, first, a metal alkoxide or a metal carboxylate and a thickener are added to a carboxylic acid, then water (H<NUM>O) is added thereto, and the mixture is heated and stirred at about <NUM> for about <NUM> hours to obtain a uniform and transparent precursor solution. The precursor solution is coated on the silicon substrate W1 by a spin coating method (coating step). Next, the solution coated on the silicon substrate W1 is heated to a temperature in a range from <NUM> to <NUM> and dried for about <NUM> minutes to obtain a dried film (drying step). Then, the dried film is heated to a temperature in a range from <NUM> to <NUM> and held for about <NUM> minutes at this temperature to be degreased (degreasing step). When a thicker zirconium oxide layer <NUM> is desired to be obtained, after the degreasing step, the process may return to the first coating step, and then the drying step and the degreasing step may be repeatedly performed. After the degreasing step, the dried film is heated to a temperature in a range from <NUM> to <NUM> and held for about <NUM> seconds to <NUM> minutes at this temperature to be crystallized (preliminary sintering step). When a further thicker zirconium oxide layer <NUM> is desired to be obtained, after the preliminary sintering step, the process may return to the first coating step, and then the drying step, the degreasing step, and the preliminary sintering step may be repeatedly performed. Then, after the preliminary sintering step, the dried film is heated to a temperature in a range from <NUM> to <NUM> and held for about <NUM> hour at this temperature, thereby forming the zirconium oxide layer <NUM> (final sintering step). Examples of a heating device used in the drying step, the degreasing step, the preliminary sintering step, and the final sintering step include a rapid thermal annealing (RTA) device that performs heating by irradiation with infrared from an infrared lamp, and a hot plate.

Next, as illustrated in <FIG>, the lower electrode <NUM> is formed on an entire surface of the vibrating plate <NUM>. Although a material of the lower electrode <NUM> is not particularly limited, it is necessary that the lower electrode <NUM> is a material whose conductivity does not disappear due to oxidation at the time of heat treatment (generally, <NUM> or higher) in forming the piezoelectric body <NUM>, diffusion of a material contained in the piezoelectric body <NUM>, or the like. For this reason, as the material of the lower electrode <NUM>, a metal such as platinum or iridium, a conductive oxide such as iridium oxide or lanthanum nickel oxide, or a laminated material of these materials, which does not lose conductivity even at a high temperature, is preferably used. The lower electrode <NUM> can be formed by, for example, vapor phase deposition such as a sputtering method, a physical vapor deposition method (PVD method), or a laser ablation method, or liquid phase deposition such as a spin coating method. An adhesion layer for securing an adhesive force may be used between the above-described conductive material and the vibrating plate <NUM>. In the embodiment, although not particularly illustrated, titanium is used as the adhesion layer. As the adhesion layer, zirconium, titanium, titanium oxide, or the like can be used. A deposition method of the adhesion layer is the same as that of the electrode material. In addition, a control layer for controlling crystal growth of the piezoelectric body <NUM> may be formed at an electrode top surface (deposition side of the piezoelectric body <NUM>). In the embodiment, titanium is used for crystal control of the piezoelectric body <NUM> (PZT). Titanium is taken into the piezoelectric body <NUM> at the time of deposition of the piezoelectric body <NUM>, and thus is not provided as a film after the piezoelectric body <NUM> is formed. As the crystal control layer, a conductive oxide having a perovskite crystal structure such as lanthanum nickel oxide may be used. A deposition method of the crystal control layer is the same as that of the electrode material. It is desirable that an insulating crystal control layer does not exist between the piezoelectric body <NUM> and the lower electrode <NUM> after the piezoelectric body <NUM> is formed. This is because the crystal control layer and a capacitor of the piezoelectric body <NUM> are coupled in series, and thus an electric field applied to the piezoelectric body <NUM> decreases. As in the embodiment, since titanium is used as an orientation control layer, although the orientation control layer is subjected to heat treatment by which the orientation control layer would originally turn into an oxide (insulator), the orientation control layer is not provided as a film because the orientation control layer is taken into the piezoelectric body <NUM>.

Next, in the embodiment, the piezoelectric body <NUM> made of lead zirconate titanate (PZT) is formed. Here, in the embodiment, the piezoelectric body <NUM> is formed using a so-called sol-gel method. In the sol-gel method, a so-called sol in which a metal complex is dissolved and dispersed in a solvent is applied and dried to be gelled, and further sintered at a high temperature to obtain the piezoelectric body <NUM> made of a metal oxide. A manufacturing method of the piezoelectric body <NUM> is not limited to the sol-gel method, and for example, a metal-organic decomposition (MOD) method or a physical vapor deposition (PVD) method such as a sputtering method and a laser ablation method may be used. That is, the piezoelectric body <NUM> may be formed by either a liquid phase method or a vapor phase method. Alternatively, the piezoelectric body <NUM> may be formed by laminating a plurality of thin piezoelectric films.

The piezoelectric body <NUM> is formed on the lower electrode <NUM> that is not patterned. When the piezoelectric body <NUM> is to be formed after patterning the lower electrode <NUM>, since the lower electrode <NUM> is patterned by a photo process, ion milling, and ashing, a top surface of the lower electrode <NUM>, a seed crystal layer such as titanium (not illustrated) provided at the top surface, or the like may deteriorate. As a result, even if the piezoelectric body <NUM> is formed on the deteriorated surface, it is less likely to obtain the piezoelectric body <NUM> having good crystallinity. In contrast, when the piezoelectric body <NUM> is formed without patterning the lower electrode <NUM>, the top surface of the lower electrode <NUM> does not deteriorate, and thus the piezoelectric body <NUM> having good crystallinity over the entire surface can be formed. In addition, since the piezoelectric body <NUM> and the vibrating plate <NUM> are not in contact with each other, diffusion of a component contained in the piezoelectric body <NUM> such as lead (Pb) or bismuth (Bi) into the vibrating plate <NUM> is also prevented.

Next, the upper electrode <NUM> is formed on the piezoelectric body <NUM>. As a material of the upper electrode <NUM>, a metal such as platinum or iridium, a conductive oxide such as iridium oxide or lanthanum nickel oxide, or a laminated material of these materials, which does not lose conductivity even at a high temperature, is preferably used. As a deposition method of the upper electrode <NUM>, the same deposition method as that of the lower electrode <NUM> can be used.

The upper electrode <NUM> is formed on the piezoelectric body <NUM> that is not patterned. Since deterioration of a top surface of the piezoelectric body <NUM> due to a patterning step does not occur, the upper electrode <NUM> having good crystallinity over the entire surface can be formed on the piezoelectric body <NUM>.

By the above-described steps, a laminated film LF in which the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM> are laminated in this order is formed on the vibrating plate <NUM>.

Next, as illustrated in <FIG>, the laminated film LF including the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM> is collectively patterned. The patterning of the laminated film LF can be performed by dry etching such as reactive ion etching (RIE) or ion milling, for example. The patterning of the laminated film LF may be performed by photolithography or wet etching using an etching solution, if possible. At a portion where the lower electrode <NUM> protrudes further in the -Y-axis direction than the piezoelectric body <NUM> illustrated in <FIG>, the piezoelectric body <NUM> and the upper electrode <NUM> on the lower electrode <NUM> are selectively removed by etching or ion milling. By this patterning step, a plurality of piezoelectric devices <NUM> arranged apart from each other are formed on the vibrating plate <NUM>.

The piezoelectric device <NUM> formed by the manufacturing method of the embodiment is manufactured by collectively patterning the laminated film LF. Therefore, the side surfaces of the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM> are exposed as side surfaces of the piezoelectric device <NUM>. That is, the side surface of the lower electrode <NUM> is not covered with the piezoelectric body <NUM>. The side surface of the piezoelectric body <NUM> is not covered with the upper electrode <NUM>.

Next, as illustrated in <FIG>, the insulating layer <NUM> is formed over one surface side (a surface side on which the laminated film LF is formed) of the silicon substrate W1. The insulating layer <NUM> covers top surfaces of the plurality of piezoelectric devices <NUM> and a top surface of the vibrating plate <NUM> where the piezoelectric devices <NUM> are not formed. As a deposition method of the insulating layer <NUM>, a vapor phase deposition method including a PVD method such as a sputtering method or a laser ablation method and a CVD method, or a liquid phase deposition method such as a sol-gel method can be used.

Next, as illustrated in <FIG>, the insulating layer <NUM> is partially removed to form the contact holes <NUM> and <NUM> and the opening <NUM> illustrated in <FIG>. The patterning of the insulating layer <NUM> can be performed by a photolithography method.

Next, the common electrode <NUM> coupled to the upper electrode <NUM> via the contact hole <NUM> and the lead electrode <NUM> (see <FIG>) coupled to the lower electrode <NUM> via the contact hole <NUM> are patterned on the vibrating plate <NUM>.

Next, as illustrated in <FIG>, the silicon substrate W1 is patterned. Specifically, a mask film (not illustrated) is formed on a surface of the silicon substrate W1 opposite from the vibrating plate <NUM>, and then anisotropic etching (wet etching) using an alkaline solution of KOH or the like is performed through the mask film to form the pressure chambers <NUM> corresponding to the piezoelectric devices <NUM>, thereby forming the channel substrate <NUM>. By the above steps, the piezoelectric actuator <NUM> of the embodiment is manufactured.

Thereafter, the nozzle plate <NUM> having the nozzles <NUM> is bonded to a surface of the channel substrate <NUM> opposite from the vibrating plate <NUM>. In addition, when the protective substrate <NUM> and the compliance substrate <NUM> that are separately manufactured are bonded, the liquid droplet discharge head of the embodiment is formed.

According to the manufacturing method of the embodiment described above, since the piezoelectric body <NUM> is formed on the lower electrode <NUM> that is not patterned, the top surface of the lower electrode <NUM> does not deteriorate in the patterning step, and the piezoelectric body <NUM> having good crystallinity over the entire surface can be formed. Then, by collectively patterning the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM>, all of the piezoelectric bodies <NUM> of the plurality of piezoelectric devices <NUM> become piezoelectric bodies having good crystallinity. It is possible to manufacture the piezoelectric actuator <NUM> including the piezoelectric device <NUM> having excellent displacement characteristics.

In addition, when the piezoelectric body <NUM> is formed on the lower electrode <NUM> that is patterned, the crystallinity of the piezoelectric body <NUM> formed on the lower electrode <NUM> and the crystallinity of the piezoelectric body <NUM> formed on the vibrating plate <NUM> are different from each other, and cracks may be generated in the piezoelectric body <NUM> on an end edge of the lower electrode <NUM>, or a region in which the crystallinity is disturbed may be formed. According to the manufacturing method of the embodiment, it is possible to prevent cracks and disturbance in crystallinity of the piezoelectric body <NUM>.

When the liquid droplet discharge head <NUM> of the embodiment is not provided with the upper electrode <NUM>, a depositing step of the upper electrode <NUM> is omitted in the manufacturing method described above. In the patterning step, the laminated film LF including the lower electrode <NUM> and the piezoelectric body <NUM> is patterned, and thereafter the common electrode <NUM> is formed on the piezoelectric body <NUM>. In the configuration in which the upper electrode <NUM> is not provided, as illustrated in <FIG>, it is preferable to form the common electrode <NUM> that covers the piezoelectric body <NUM>.

Next, a printer according to the embodiment will be described with reference to the drawings. <FIG> is a perspective view schematically illustrating a printer <NUM> according to the embodiment.

The printer <NUM> is an inkjet printer. As illustrated in <FIG>, the printer <NUM> includes a head unit <NUM>. The head unit <NUM> includes, for example, the liquid droplet discharge head <NUM>. The number of the liquid droplet discharge heads <NUM> is not particularly limited. The head unit <NUM> is detachably provided with cartridges <NUM> and <NUM> that constitute a supply unit. A carriage <NUM> on which the head unit <NUM> is mounted is movable in an axial direction on a carriage shaft <NUM> attached to a device main body <NUM>, and discharges a liquid supplied from a liquid supply unit.

Here, the liquid may be a material in a state where a substance is in a liquid phase, and the liquid also includes a material in a liquid state such as a sol or a gel. In addition, the liquid includes not only a liquid as one state of a substance, but also a composition that is obtained by dissolving, dispersing or mixing particles of a functional material formed of a solid such as a pigment or a metal particle in a solvent. Typical examples of the liquid include an ink and a liquid crystal emulsifier. The ink includes various liquid compositions such as a general water-based ink, an oil-based ink, a gel ink, and a hot melt ink.

In the printer <NUM>, a driving force of a drive motor <NUM> is transmitted to the carriage <NUM> via a plurality of gears (not illustrated) and a timing belt <NUM>, whereby the carriage <NUM> on which the head unit <NUM> is mounted is moved along the carriage shaft <NUM>. On the other hand, the device main body <NUM> is provided with a conveying roller <NUM> as a conveyance mechanism that moves a sheet S, which is a recording medium such as paper, relative to the liquid droplet discharge head <NUM>. The conveyance mechanism for conveying the sheet S is not limited to the conveying roller, and may be a belt, a drum, or the like.

The printer <NUM> includes a printer controller <NUM> as a control unit that controls the liquid droplet discharge head <NUM> and the conveying roller <NUM>. The printer controller <NUM> is electrically coupled to the circuit substrate <NUM> of the liquid droplet discharge head <NUM>. The printer controller <NUM> includes, for example, a random access memory (RAM) that temporarily stores various types of data, a read only memory (ROM) that stores a control program and the like, a central processing unit (CPU), and a drive signal generation circuit that generates a drive signal to be supplied to the liquid droplet discharge head <NUM>.

<FIG> is a plan view of an ultrasonic device in which the piezoelectric device of the above embodiment is mounted as an ultrasonic transducer. <FIG> is a partial cross-sectional view taken along a line XIV-XIV in <FIG>. In the embodiment, transmission and reception of ultrasonic waves are performed by using an electroacoustic transducer that uses a piezoelectric effect. The electroacoustic transducer is the piezoelectric device <NUM>. At the time of transmission of ultrasonic waves, the electroacoustic transducer converts electric energy into mechanical energy (uses an inverse piezoelectric effect), and changes due to contraction and extension of the piezoelectric layer excite the vibrating plate to vibrate, thereby transmitting ultrasonic waves. Therefore, in this case, the piezoelectric device <NUM> is a transmission ultrasonic transducer <NUM>.

Further, in order to receive ultrasonic waves reflected from an object to be detected, mechanical energy is converted into electric energy (positive piezoelectric effect is used), and the electric energy is generated by deformation of the piezoelectric body, and a signal of the electric energy is detected. Therefore, in this case, the piezoelectric device <NUM> is a reception ultrasonic transducer <NUM>.

As illustrated in <FIG> and <FIG>, a plurality of transmission ultrasonic transducers <NUM> and a plurality of reception ultrasonic transducers <NUM> are provided in an array on an opening substrate <NUM> having a plurality of openings <NUM>, and constitute an ultrasonic device <NUM> (array sensor). Columns of the plurality of transmission ultrasonic transducers <NUM> and columns of the plurality of reception ultrasonic transducers <NUM> are alternately arranged, and energization is switched for each column of the transducers. Line scanning and sector scanning are implemented according to the switching of the energization. Further, levels of output and input of ultrasonic waves are determined according to the number of the transducers to be energized and the number of the columns. In the drawing, <NUM> rows × <NUM> columns are drawn without being illustrated. The number of rows and the number of columns of the array are determined according to spread of a scan range.

As transducers, the transmission ultrasonic transducer <NUM> and the reception ultrasonic transducer <NUM> can be arranged alternately one by one. In this case, by using an ultrasonic wave transmission and reception source in which central axes of the transmission side and the reception side are aligned with each other, it is easy to align directional angles of transmission and reception.

In <FIG>, the vibrating plate <NUM> is formed on an upper surface of the opening substrate <NUM> (on a piezoelectric body <NUM> side). The plurality of openings <NUM> are formed in the opening substrate <NUM>. The opening <NUM> can be formed by a processing method such as etching, polishing, or laser processing depending on a substrate material. Since the lower electrode <NUM>, the piezoelectric body <NUM>, and the upper electrode <NUM> are the same as those of the above-described embodiment, a description of configurations thereof will be omitted. Although not illustrated in the drawing, the common electrode <NUM> is coupled to the upper electrode <NUM> in the same manner as in the above-described embodiment. The common electrode <NUM> is preferably disposed in a region that does not overlap the opening <NUM> in a plan view. With this configuration, the deformation of the piezoelectric device <NUM> is not obstructed, and the ultrasonic device including the ultrasonic transducer having excellent deformation characteristics is obtained.

In contrast to the previous embodiment, since the ultrasonic device needs to be driven in a higher frequency region than the liquid droplet discharge head <NUM>, configurations and physical property values such as thickness and the Young's modulus of the piezoelectric body <NUM>, the vibrating plate <NUM>, the electrode materials, and the opening substrate <NUM> may be adjusted.

Further, wirings (not illustrated) are coupled to the transmission ultrasonic transducer <NUM> and the reception ultrasonic transducer <NUM>, and each wiring is coupled to a terminal portion (not illustrated) of a control board (not illustrated) via a flexible printed wiring board (not illustrated). The control board is provided with a control unit (not illustrated) that includes a calculation unit, a storage unit, and the like. The control unit controls an input signal input to the transmission ultrasonic transducer <NUM> and processes an output signal output from the reception ultrasonic transducer <NUM>.

Claim 1:
A piezoelectric actuator (<NUM>) comprising:
a substrate (<NUM>);
a first piezoelectric device (300A) and a second piezoelectric device (300B) formed at the substrate so as to be arranged side by side along a first direction in the plane of the substrate, the first piezoelectric device including a first lower electrode (60A) formed at the substrate, a first piezoelectric body (70A) formed at the first lower electrode, and a first upper electrode (80A) formed at the first piezoelectric body, the second piezoelectric device including a second lower electrode (60B) formed at the substrate in a region different from the first lower electrode, a second piezoelectric body (70B) formed at the second lower electrode, and a second upper electrode (80B) formed at the second piezoelectric body;
a common electrode (<NUM>) formed at the substrate and coupled to the first upper electrode and the second upper electrode; and
an insulating layer (<NUM>) located between the common electrode and the first lower electrode and between the common electrode and the second lower electrode, wherein
a side surface of the first lower electrode is not covered with the first piezoelectric body, and
a side surface of the second lower electrode is not covered with the second piezoelectric body, wherein
a first lead electrode (<NUM>) is coupled to an end of the first lower electrode (60A) in a second direction in the plane of the substrate perpendicular to the first direction,
a second lead electrode (<NUM>) is coupled to an end of the second lower electrode (60A) in the second direction in the plane of the substrate perpendicular to the first direction,
and the common electrode covers each of the first piezoelectric body and the second piezoelectric body on all side surfaces of the first piezoelectric body and the second piezoelectric body other than the side surface of the first piezoelectric body facing the first lead electrode and the side surface of the second piezoelectric body facing the second lead electrode.