Patent Publication Number: US-2021162744-A1

Title: Liquid ejecting apparatus and method of driving liquid ejecting head

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-216452, filed Nov. 29, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a liquid ejecting apparatus including a liquid ejecting head which ejects a liquid, and a method of driving the liquid ejecting head. 
     2. Related Art 
     A liquid ejecting head, in which a vibration plate is provided at a flow path formation substrate at which a pressure chamber is formed and a piezoelectric actuator is provided at the vibration plate, used in a liquid ejecting apparatus is known. It is known that the piezoelectric actuator is formed by stacking a first electrode, a piezoelectric layer, and a second electrode from the vibration plate side. 
     As one form of the piezoelectric actuator, a piezoelectric actuator in which an active portion of a piezoelectric actuator is provided at an edge portion of a region of a vibration plate facing a pressure chamber (hereinafter, referred to as a movable region), and the active portion is not provided at a central portion of the movable region is known (for example, see JP-A-2011-56913). That is, the piezoelectric actuator has a configuration in which the annular active portion is provided over the vibration plate so as to overlap the edge portion in plan view, and the vibration plate is exposed without the active portion being provided at the central portion. 
     In such an annular piezoelectric actuator, it is proposed that the vibration plate is in a state of being bent in a convex shape on a side opposite to the pressure chamber as initial deflection before ejection and the pressure chamber side has a concave shape by supplying a drive signal, and then the vibration plate is deformed in a convex shape toward the pressure chamber side, so that a liquid droplet such as an ink droplet is ejected from a nozzle (see, for example, JP-A-2011-56913). 
     However, in order to make the initial deflection of the vibration plate to be convex toward the pressure chamber side, it is necessary to execute one or both of that a member having compressive stress is introduced into a member constituting the vibration plate and that a member having patterned tensile stress, which is not a beam shape, is disposed in a region facing the pressure chamber as the member constituting the vibration plate. 
     As described above, even when the member having compressive stress is introduced into the member constituting the vibration plate, there is a problem that it cannot be said that the initial deflection is necessarily deformed to be convex toward the pressure chamber side and it is difficult to control the initial deflection of the vibration plate. 
     Further, even when the member having patterned tensile stress, which is not a beam shape, is disposed in the member constituting the vibration plate, the tensile stress is further increased by displacement generated when an electric field is applied to the piezoelectric actuator, so that there is a problem that the piezoelectric actuator is easily broken. 
     Further, when a width of the pressure chamber is widened so as to increase a weight of the ejected liquid droplet, there are problems that stress at the vibration plate increases and the vibration plate is more easily broken. 
     Such a problem is not limited to an ink jet recording apparatus which ejects ink, and also exists in a liquid ejecting apparatus which ejects a liquid other than ink. 
     SUMMARY 
     An advantage of some aspects of the present disclosure is that there are provided a liquid ejecting apparatus and a method of driving a liquid ejecting head capable of improving a displacement amount of a piezoelectric actuator and improving a disposition density of a pressure chamber. 
     According to an aspect of the present disclosure, there is provided a liquid ejecting apparatus including: a liquid ejecting head that includes a flow path formation substrate in which a pressure chamber communicating with a nozzle is formed, a vibration plate formed on one surface side of the flow path formation substrate, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode that are formed on a surface side of the vibration plate opposite to the flow path formation substrate; and a drive unit that supplies a drive signal for driving the piezoelectric actuator, in which the piezoelectric actuator includes an active portion in which the piezoelectric layer is interposed between the first electrode and the second electrode, in plan view from a stacking direction of the first electrode, the piezoelectric layer, and the second electrode, the active portion is extended from an edge portion, which is a region other than a central portion of a region facing the pressure chamber, to the outside of the pressure chamber, and the drive signal includes a contraction element that contracts the pressure chamber from a reference volume of the pressure chamber when no electric field is applied to the piezoelectric layer, and an expansion element that expands the pressure chamber contracted by the contraction element. 
     According to another aspect of the present disclosure, there is provided a method of driving a liquid ejecting head, the liquid ejecting head including a flow path formation substrate in which a pressure chamber communicating with a nozzle is formed, a vibration plate formed on one surface side of the flow path formation substrate, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode that are formed on a surface side of the vibration plate opposite to the flow path formation substrate, in which the piezoelectric actuator includes an active portion in which the piezoelectric layer is interposed between the first electrode and the second electrode, and in plan view from a stacking direction of the first electrode, the piezoelectric layer, and the second electrode, the active portion is extended from an edge portion, which is a region other than a central portion of a region facing the pressure chamber, to the outside of the pressure chamber, the method including: driving the piezoelectric actuator by a drive signal including a contraction element that contracts the pressure chamber from a reference volume of the pressure chamber when no electric field is applied to the piezoelectric layer, and an expansion element that expands the pressure chamber contracted by the contraction element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a schematic configuration of a recording apparatus according to Embodiment 1. 
         FIG. 2  is a plan view of a recording head according to Embodiment 1. 
         FIG. 3  is a cross-sectional view of the recording head according to Embodiment 1. 
         FIG. 4  is a plan view of a piezoelectric actuator according to Embodiment 1. 
         FIG. 5  is an enlarged cross-sectional view of a main portion of the recording head according to Embodiment 1. 
         FIG. 6  is a block diagram illustrating an electrical configuration of the recording apparatus according to Embodiment 1. 
         FIG. 7  is a drive waveform illustrating a drive signal according to Embodiment 1. 
         FIG. 8  is a cross-sectional view schematically illustrating a deformed state of a vibration plate according to Embodiment 1. 
         FIG. 9  is a graph illustrating a relationship between a displacement amount of a piezoelectric layer and an electric field according to Embodiment 1. 
         FIG. 10  is a drive waveform illustrating a drive signal according to Embodiment 2. 
         FIG. 11  is a drive waveform illustrating a modification example of the drive signal according to Embodiment 2. 
         FIG. 12  is a drive waveform illustrating another modification example of the drive signal according to Embodiment 2. 
         FIG. 13  is a drive waveform illustrating a drive signal according to Embodiment 3. 
         FIG. 14  is a drive waveform illustrating a drive signal according to another embodiment. 
         FIG. 15  is a drive waveform illustrating a drive signal according to still another embodiment. 
         FIG. 16  is a drive waveform illustrating a drive signal according to still another embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, the present disclosure will be described in detail based on embodiments. Meanwhile, the following description illustrates one aspect of the present disclosure, and can be arbitrarily modified within the scope of the present disclosure. In each drawing, the same reference numerals denote the same members, and the description thereof will be appropriately omitted. Further, in each drawing, X, Y, and Z represent three spatial axes orthogonal to each other. In this specification, directions along these axes are an X-direction, a Y-direction, and a Z-direction. In the following description, a direction of an arrow is a positive (+) direction and a direction opposite to the arrow is a negative (−) direction in each drawing. Further, the Z-direction indicates a vertical direction, and the +Z-direction indicates a vertical downward direction and the −Z-direction indicates a vertical upward direction. 
     Embodiment 1 
       FIG. 1  is a schematic diagram illustrating an example of an ink jet recording apparatus which is an example of a liquid ejecting apparatus according to Embodiment 1 of the present disclosure. 
     As illustrated in  FIG. 1 , an ink jet recording apparatus I which is an example of a liquid ejecting apparatus according to the present embodiment includes an ink jet recording head  1  (hereinafter, simply referred to as “recording head  1 ”) which ejects ink as an ink droplet, as an example of a liquid ejecting head. The recording head  1  is mounted at a carriage  3  and the carriage  3  is movably provided in the Y-direction which is an axial direction of a carriage shaft  5  attached to an apparatus main body  4 . In addition, an ink cartridge  2  constituting a liquid storage unit is detachably provided in the carriage  3 . 
     By a driving force of a driving motor  6  being transmitted to the carriage  3  via a plurality of gears (not illustrated) and a timing belt  7 , the carriage  3  at which the recording head  1  is mounted reciprocates along the carriage shaft  5  in the Y-direction. On the other hand, a transport roller  8  is provided in the apparatus main body  4  as a transport unit and a recording sheet S which is a medium to be ejected such as paper on which ink is impacted is transported by the transport roller  8  in the X-direction. 
     Further, the ink jet recording apparatus I includes a control apparatus  200  which controls the entire ink jet recording apparatus I. The control apparatus  200  will be described in detail below. 
     In the ink jet recording apparatus I, while the recording sheet S is transported in the +X-direction based on the recording head  1  and the carriage  3  is reciprocated in the Y-direction based on the recording sheet S, by ejecting an ink droplet from the recording head  1 , impact of the ink droplet, so-called printing is executed across an approximately entire surface of the recording sheet S. 
     Here, the recording head  1  according to the present embodiment mounted on such an ink jet recording apparatus I will be described with reference to  FIGS. 2 to 5 .  FIG. 2  is a plan view illustrating an ink jet recording head which is an example of the liquid ejecting head according to Embodiment 1 according to the disclosure.  FIG. 3  is a cross-sectional view taken along the line III-III in  FIG. 2 .  FIG. 4  is an enlarged plan view of a main portion of a piezoelectric actuator.  FIG. 5  is a cross-sectional view taken along the line V-V in  FIG. 4 . 
     As illustrated, the recording head  1  includes a flow path unit  100  and a piezoelectric actuator  300 . The flow path unit  100  according to the present embodiment includes a flow path formation substrate  10 , a common liquid chamber substrate  30 , a nozzle plate  20 , and a compliance substrate  40 . 
     The flow path formation substrate  10  includes a silicon substrate, a glass substrate, an SOI substrate, and various ceramic substrates. 
     In the flow path formation substrate  10 , a plurality of pressure chambers  12  are juxtaposed along the X-direction. The plurality of pressure chambers  12  are arranged on a straight line along the X-direction so that positions in the Y-direction are the same. Of course, the disposition of the pressure chambers  12  is not particularly limited to this, and for example, in the pressure chambers  12  juxtaposed in the X-direction, every other one may be arranged in a position shifted in the Y-direction, so-called staggered disposition. 
     Further, in the pressure chamber  12  according to the present embodiment, a shape viewed from the Z-direction in plan view, that is, an opening shape in the Z-direction is a so-called rounded rectangular shape in which both end portions in a longitudinal direction are semicircular, based on a rectangular shape in which the Y-direction is the longitudinal direction (also called a track shape). That is, the pressure chamber  12  has an elongated shape in which the Y-direction is the longitudinal direction and the X-direction is a lateral direction when viewed from the Z-direction in plan view. In this manner, by forming the pressure chamber  12  in an elongated shape, when the plurality of pressure chambers  12  are arranged side by side in the lateral direction, a volume of the pressure chamber  12  can be secured and a size can be reduced. 
     Of course, the shape of the pressure chamber  12  when viewed from the Z-direction in plan view is not particularly limited to this, and an example of the shape may include a square shape, a rectangular shape, a polygonal shape, a parallelogram shape, a fan shape, a circular shape, and an elongated hole shape. Incidentally, the elongated hole shape means an elliptical shape or a shape similar to the elliptical shape, for example, a rounded rectangular shape, an egg shape, an oval shape, or the like. 
     Further, the common liquid chamber substrate  30  and the nozzle plate  20  are sequentially stacked at a +Z side surface of the flow path formation substrate  10 . 
     The common liquid chamber substrate  30  is a substrate in which a common liquid chamber  35  communicating with each pressure chamber  12  is formed, and is provided at the +Z side surface of the flow path formation substrate  10 . The common liquid chamber  35  is provided so as to have a size which is continuous in the X-direction across the plurality of pressure chambers  12 . Further, the common liquid chamber  35  is arranged at a position so as to be overlapped with the end portion of the pressure chamber  12  in the Y-direction when viewed from the Z-direction in plan view. Such a common liquid chamber  35  is provided so as to open at a +Z side surface of the common liquid chamber substrate  30 . 
     In addition, a plurality of first flow paths  31  communicating with one end portion of the pressure chamber  12  in the Y-direction are formed in the common liquid chamber substrate  30 . The first flow path  31  is independently provided in each of the pressure chambers  12 . The first flow path  31  communicates the common liquid chamber  35  and the pressure chamber  12  in the Z-direction, and supplies ink in the common liquid chamber  35  to the pressure chamber  12 . 
     In addition, a plurality of second flow paths  32  which communicate the pressure chambers  12  and nozzles  21  are formed in the common liquid chamber substrate  30 . The second flow path  32  is a flow path which couples the pressure chamber  12  and the nozzle  21 , and is provided so as to penetrate the common liquid chamber substrate  30  in the Z-direction. 
     As such a common liquid chamber substrate  30 , a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless substrate, or the like can be used. The common liquid chamber substrate  30  may be made of a material having approximately an identical coefficient of thermal expansion as the flow path formation substrate  10 . In this manner, by using the materials having approximately the identical coefficient of thermal expansion for the flow path formation substrate  10  and the common liquid chamber substrate  30  as described above, it is possible to reduce occurrence of a warpage due to heat by a difference in the coefficient of thermal expansion. 
     The nozzle plate  20  is provided at a surface, which is opposite to the flow path formation substrate  10 , of the common liquid chamber substrate  30 , that is, at the +Z side surface. 
     A plurality of nozzles  21  which eject ink in the +Z-direction are formed in the nozzle plate  20 . In the present embodiment, as illustrated in  FIG. 2 , the plurality of nozzles  21  are arranged on a straight line along the X-direction. That is, the plurality of nozzles  21  are arranged so that positions in the Y-direction are the same. Of course, the disposition of the nozzle  21  is not particularly limited to this, and for example, in the nozzles  21  juxtaposed in the X-direction, every other one may be arranged in a position shifted in the Y-direction, so-called staggered disposition. 
     As such a nozzle plate  20 , a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless substrate, or an organic substance such as a polyimide resin can be used. 
     In addition, the compliance substrate  40  is provided at the +Z side surface, at which the common liquid chamber  35  opens, of the common liquid chamber substrate  30 . The compliance substrate  40  seals a +Z side opening of the common liquid chamber  35 . In the present embodiment, such a compliance substrate  40  includes a sealing film  41  made of a flexible thin film and a fixed substrate  42  made of a hard material such as metal. A region, facing the common liquid chamber  35 , in the fixed substrate  42  is an opening portion  43  which is completely removed in a thickness direction. Therefore, one surface of the common liquid chamber  35  serves as a compliance portion  49  which is a flexible portion sealed only with the sealing film  41  having flexibility. In this manner, by providing the compliance portion  49  at a part of a wall surface of the common liquid chamber  35  as described above, pressure fluctuation of the ink in the common liquid chamber  35  can be absorbed by deformation of the compliance portion  49 . 
     In the flow path unit  100  having such a configuration, an ink flow path from the common liquid chamber  35  to the nozzle  21  via the first flow path  31 , the pressure chamber  12 , and the second flow path  32  is formed. Although not particularly illustrated, the common liquid chamber  35  is configured to be supplied with ink from an external ink supply unit. The ink supplied from the external ink supply unit is supplied to the common liquid chamber  35 . The ink is supplied from the common liquid chamber  35  to each pressure chamber  12  via each first flow path  31 . The ink in the pressure chamber  12  is ejected from the nozzle  21  via the second flow path  32  by the piezoelectric actuator  300  to be described below. 
     On the other hand, a vibration plate  50  is formed at the −Z side surface of the flow path formation substrate  10  opposite to the common liquid chamber substrate  30 . The vibration plate  50  is a flexible member including a single layer or a plurality of layers selected from a silicon layer, a silicon dioxide layer, a silicon nitride layer, a zirconium oxide layer, and the like. 
     Further, a first electrode  60 , a piezoelectric layer  70 , and a second electrode  80  are sequentially stacked in the −Z-direction over the vibration plate  50  by a film formation and lithography method. The piezoelectric actuator  300  according to the present embodiment is configured to include the vibration plate  50 , the first electrode  60 , the piezoelectric layer  70 , and the second electrode  80 . In the present embodiment, the piezoelectric actuator  300  is an energy generation element which causes a pressure change in ink inside the pressure chamber  12 . Here, the piezoelectric actuator  300  is also referred to as a piezoelectric element, and is a portion including the vibration plate  50 , the first electrode  60 , the piezoelectric layer  70 , and the second electrode  80 . 
     Further, in the piezoelectric actuator  300 , a portion in which piezoelectric strain is generated in the piezoelectric layer  70  when a voltage is applied between the first electrode  60  and the second electrode  80  is referred to as an active portion  310 . In the present embodiment, as will be described below in detail, the active portion  310  is formed for each pressure chamber  12 . That is, a plurality of active portions  310  formed in the piezoelectric actuator  300 . In general, one electrode of the active portion  310  is used as a common electrode common to the plurality of active portions  310 , and the other electrode is configured as an individual electrode which is independent for each active portion  310 . In the present embodiment, the first electrode  60  is the common electrode and the second electrode  80  is the individual electrode, but this may be reversed. In the example described above, the vibration plate  50  and the first electrode  60  are operated as a vibration plate, but the example is not limited thereto and only the first electrode  60  may be operated as the vibration plate without being provided with the vibration plate  50 . In addition, the piezoelectric actuator  300  itself may practically serve also as the vibration plate. 
     Here, in the present embodiment, a region, facing the pressure chamber  12 , in the vibration plate  50  is referred to as a movable region C. Further, in the movable region C, a region which is inside a wall surface which is an end portion of the pressure chamber  12 , and does not include a central portion of the pressure chamber  12  when viewed from the Z-direction in plan view is referred to as an edge portion B. The piezoelectric actuator  300  is provided at the edge portion B. Further, a region other than the edge portion B in the movable region C is referred to as a central portion A. The active portion  310  of the piezoelectric actuator  300  is not provided in the central portion A. 
     For such a vibration plate  50 , the active portion  310  is provided at the edge portion B in the movable region C (see  FIG. 3 ) of the vibration plate  50 . Further, in the present embodiment, the active portion  310  extends outside the edge portion B, that is, outside the pressure chamber  12 . The active portion  310  is not provided in the central portion A. That is, the active portion  310  of the piezoelectric actuator  300  is provided continuously over the outer side of the pressure chamber  12  and the edge portion B and across a boundary portion of a wall surface of the pressure chamber  12 . 
     As illustrated in  FIG. 4 , a shape of the active portion  310  in plan view is approximately the same as the shape of the pressure chamber  12 , and is an annular rounded rectangular shape having the Y-direction as the longitudinal direction. 
     Specifically, the first electrode  60  is continuously provided across the plurality of pressure chambers  12  and constitutes the common electrode common to the plurality of active portions  310  of the piezoelectric actuator  300 . The first electrode  60  is continuously provided so that a width in the Y-direction is wider than a length of the pressure chamber  12  in the Y-direction and the first electrode  60  is across the plurality of pressure chambers  12  juxtaposed in the X-direction. In addition, the first electrode  60  is not provided in the central portion A of the vibration plate  50 , and an end portion at the central portion A side is covered with the piezoelectric layer  70 . Of course, the first electrode  60  may be provided in the central portion A of the vibration plate  50 . 
     The piezoelectric layer  70  is continuously provided across the X-direction so as to have a predetermined width in the Y-direction. A width of the piezoelectric layer  70  in the Y-direction is wider than the length of the pressure chamber  12  in the Y-direction. Therefore, in the Y-direction of the pressure chamber  12 , the piezoelectric layer  70  is provided up to the outside of the pressure chamber  12 . In the present embodiment, the piezoelectric layer  70  is continuously provided over the plurality of pressure chambers  12 , but the present embodiment is not particularly limited to this, and the piezoelectric layer  70  may be provided separately across a wall surface of the adjacent pressure chamber  12 , for each pressure chamber  12 . 
     The piezoelectric layer  70  is made of an oxide piezoelectric material having a polarization structure formed at the first electrode  60 , and may be made of, for example, a perovskite type oxide represented by the general formula ABO 3 . As the piezoelectric layer  70 , a lead-based piezoelectric material containing lead, a lead-free piezoelectric material containing no lead, or the like can be used. 
     In the piezoelectric layer  70 , a direction of polarization or a dipole remaining inside the piezoelectric layer  70  when no potential is applied (hereinafter, collectively referred to as a polarization direction) may be from the first electrode  60  toward the second electrode  80  in the Z-direction, or may be from the second electrode  80  toward the first electrode  60  in the +Z-direction. In the present embodiment, the polarization direction of the piezoelectric layer  70  is a direction from the first electrode  60  to the second electrode  80 , that is, the −Z-direction. 
     The second electrode  80  is divided for each pressure chamber  12  and constitutes an individual electrode independent for each active portion  310  of the piezoelectric actuator  300 . The second electrode  80  is formed in an annular shape when viewed from the Z-direction in plan view. That is, in the same manner as the pressure chamber  12 , the second electrode  80  has a rounded rectangular outer peripheral shape having the Y-direction as a major axis, and an opening portion having a shape approximately similar to the outer peripheral shape is formed in a central portion of the second electrode  80  so as to be formed in an annular shape. An end portion of the second electrode  80  defines a range of the active portion  310 . That is, the second electrode  80  is provided at the edge portion B of the movable region C (see  FIG. 3 ) of the vibration plate  50  and outside the edge portion B, that is, outside the pressure chamber  12 , and the second electrode  80  is not provided in the central portion A. Such a second electrode  80  may have a film having a thickness equal to or less than 100 nm. In this manner, by providing the second electrode  80  with the thickness equal to or less than 100 nm, it is possible to suppress the second electrode  80  from inhibiting deformation of the active portion  310  and to suppress a displacement amount of the active portion  310  from decreasing. The second electrode  80  may be made of at least one material selected from a group consisting of platinum (Pt), iridium (Ir), and gold (Au). In this manner, by using at least one material selected from the group consisting of platinum (Pt), iridium (Ir), and gold (Au) for the second electrode  80 , an electric resistance value of the second electrode  80  can be reduced and a voltage drop can be suppressed. 
     As illustrated in  FIG. 5 , the piezoelectric actuator  300  is covered with a protective film  110 . As the protective film  110 , an insulating material having moisture resistance can be used. In the present embodiment, the protective film  110  is continuously provided over the first electrode  60  so as to cover a side surface of the piezoelectric layer  70 , a side surface and an upper surface of the second electrode  80 , and the central portion A of the vibration plate  50 . Although the protective film  110  covers the central portion A of the vibration plate  50  in the present embodiment, the present embodiment is not limited to this, and the protective film  110  may be provided so as not to partially or entirely cover the central portion A of the vibration plate  50 . By providing the protective film  110  so as not to cover a part or the whole of the central portion A of the vibration plate  50  in this manner, it is possible to suppress the protective film  110  from inhibiting displacement of the vibration plate  50  and to suppress a displacement amount from decreasing. 
     In this manner, by covering the side surface of the piezoelectric layer  70  with the protective film  110 , it is possible to suppress a current from leaking between the first electrode  60  and the second electrode  80 , and to suppress damage such as burning due to a leakage current of the piezoelectric actuator  300 . Further, by providing the protective film  110 , it is possible to suppress the first electrode  60  and the second electrode  80  from being short-circuited by a lead electrode  90 , which will be described below in detail, which is a lead wiring. 
     As a material of such a protective film  110 , a material having moisture resistance may be used, and an inorganic insulating material, an organic insulating material, or the like can be used. 
     As an inorganic insulating material which can be used as the protective film  110 , at least one type selected from, for example, silicon oxide (SiO x ), zirconium oxide (ZrO x ), tantalum oxide (TaO x ), aluminum oxide (AlO x ), and titanium oxide (TiO x ) can be used. As the inorganic insulating material of the protective film  110 , aluminum oxide (AlO x ) which is an inorganic amorphous material, for example, alumina (Al 2 O 3 ) may be used. The protective film  110  made of an inorganic insulating material can be formed by, for example, an MOD method, a sol-gel method, a sputtering method, a CVD method, or the like. 
     In addition, as the organic insulating material which can be used as the protective film  110 , for example, at least one selected from an epoxy resin, a polyimide resin, a silicon resin, and a fluorine resin can be used. The protective film  110  made of an organic insulating material can be formed by, for example, a spin coating method, a spray method, or the like. 
     The lead electrode  90 , which is a lead wiring drawn from each electrode of the piezoelectric actuator  300 , is provided over the protective film  110 . The lead electrode  90  includes an individual lead electrode  91  extracted from the second electrode  80  and a common lead electrode  92  extracted from the first electrode  60 . The lead electrode  90  may be made of a material containing at least one selected from the group consisting of Pt, Ir, Au, ITO, Cu, Al, Al—Cu, and Al—Nd. Further, the lead electrode  90  may have an adhesion layer which improves adhesion to the protective film  110 . 
     Here, the individual lead electrode  91  is coupled to the second electrode  80  via a contact hole  111  provided in the protective film  110  at one end portion in the Y-direction. The other end portion of the individual lead electrode  91  is extended along the Y-direction to a region, in which the first electrode  60  is not formed, at the flow path formation substrate  10 . 
     A wiring substrate  121  at which the drive circuit  120  is mounted is electrically coupled to the individual lead electrode  91 . The drive circuit  120  includes a circuit substrate, a semiconductor integrated circuit (IC), or the like. Further, the wiring substrate  121  is a COF substrate which is a kind of a flexible wiring substrate. A drive signal from the drive circuit  120  is supplied to the second electrode  80  via the individual lead electrode  91 . 
     Further, one end of the common lead electrode  92  is coupled to the first electrode  60  via a contact hole  112  provided in the protective film  110  at an end portion in the Y-direction. The other end portion of the common lead electrode  92  is extended along the Y-direction to a region, in which the first electrode  60  is not formed, at the flow path formation substrate  10 . 
     Here, one end of the common lead electrode  92  is coupled to the first electrode  60  via the contact hole  112  provided in the protective film  110  at an end portion in the Y-direction. 
     In this manner, in the recording head  1 , after ink is filled from the common liquid chamber  35  to the nozzle  21 , pressure inside the pressure chamber  12  increases and the ink is ejected from the nozzle  21  by applying a voltage between the first electrode  60  and the second electrode  80  respectively corresponding to the pressure chamber  12  according to a drive signal from the drive circuit  120 , and bending and deforming the vibration plate  50  and the piezoelectric actuator  300 . 
     Further, as illustrated in  FIG. 1 , the ink jet recording apparatus I includes the control apparatus  200 . Here, an electrical configuration according to the present embodiment will be described with reference to  FIG. 6 .  FIG. 6  is a block diagram illustrating an electrical configuration of the ink jet recording apparatus I according to Embodiment 1 of the present disclosure. 
     As illustrated in  FIG. 6 , the ink jet recording apparatus I includes a printer controller  210  and a print engine  220 . 
     The printer controller  210  is an element which controls the overall ink jet recording apparatus I and is provided in the control apparatus  200  provided in the ink jet recording apparatus I in the present embodiment. 
     The printer controller  210  includes an external interface  211  (hereinafter, referred to as the external I/F  211 ), a RAM  212 , a ROM  213 , a control processing portion  214 , an oscillation circuit  215  which generates a clock signal, a drive signal generation circuit  216 , a power supply generation circuit  217 , and an internal interface  218  (hereinafter, referred to as the internal I/F  218 ). 
     The external I/F  211  receives print data including, for example, a character code, a graphic function, image data, and the like from an external apparatus  230  such as a host computer. Further, a busy signal (BUSY) or an acknowledge signal (ACK) is output to the external apparatus  230  through the external I/F  211 . 
     The RAM  212  temporarily stores various types of data and functions as a reception buffer  212 A, an intermediate buffer  212 B, an output buffer  212 C, and a work memory (not illustrated). The reception buffer  212 A temporarily stores the print data received by the external I/F  211 , the intermediate buffer  212 B stores intermediate code data converted by the control processing portion  214 , and the output buffer  212 C stores dot pattern data. The dot pattern data is configured with print data obtained by decoding (translating) gradation data. 
     Further, the ROM  213  stores font data, a graphic function, and the like in addition to a control program (a control routine) for performing a process on various types of data. 
     The control processing portion  214  is configured to include a CPU and the like. The control processing portion  214  reads the print data in the reception buffer  212 A and stores the intermediate code data obtained by converting the print data in the intermediate buffer  212 B. Further, the intermediate code data read from the intermediate buffer  212 B is analyzed, and the intermediate code data is expanded into dot pattern data by referring to the font data and the graphic function stored in the ROM  213 . The control processing portion  214  stores the developed dot pattern data in the output buffer  212 C after executing a necessary decoration process. 
     When dot pattern data for one line is obtained in the recording head  1 , the dot pattern data for one line is output to the recording head  1  through the internal I/F  218 . Further, when the dot pattern data for one line is output from the output buffer  212 C, the developed intermediate code data is deleted from the intermediate buffer  212 B, and the development process is performed on the next intermediate code data. That is, the internal I/F  218  transmits the dot pattern data (also referred to as bitmap data) or the like developed based on a drive signal or print data, to the print engine  220 . 
     The drive signal generation circuit  216  generates a common drive signal COM to be supplied to the recording head  1  based on power supplied from the outside. 
     Further, the power supply generation circuit  217  generates a bias potential vbs, which will be described in detail below, to be supplied to the first electrode  60  which is a common electrode of the piezoelectric actuator  300  based on the power supplied from the outside. 
     The print engine  220  is configured to include the recording head  1 , a paper feeding mechanism  221 , and a carriage mechanism  222 . The paper feeding mechanism  221  is configured to include the transport roller  8  and a motor (not illustrated) or the like which drives the transport roller  8 , and sequentially feeds the recording sheet S in conjunction with a recording operation of the recording head  1 . That is, the paper feeding mechanism  221  relatively moves the recording sheet S in the X-direction. The carriage mechanism  222  includes the carriage  3 , and a driving motor  6  or a timing belt  7  which moves the carriage  3  along the carriage shaft  5  in the Y-direction. 
     The recording head  1  includes a shift register  122 , a latch circuit  123 , a level shifter  124 , a drive circuit  120  having a switch  125 , and the piezoelectric actuator  300 . Although not particularly illustrated, the shift register  122 , the latch circuit  123 , the level shifter  124 , the switch  125 , and the piezoelectric actuator  300  are respectively provided as a shift register element, a latch element, a level shifter element, a switch element, and a piezoelectric actuator  300  provided for each nozzle  21  of the recording head  1 . The shift register  122 , the latch circuit  123 , the level shifter  124 , the switch  125 , and the piezoelectric actuator  300  are electrically coupled in this order. The shift register  122 , the latch circuit  123 , the level shifter  124 , and the switch  125  generate an application pulse to be actually applied from the common drive signal COM generated by the drive signal generation circuit  216  to the piezoelectric actuator  300 . 
     In the present embodiment, the printer controller  210  and the drive circuit  120  correspond to a drive unit in the scope of the aspects. 
     Here, a drive waveform indicating the common drive signal generated by the drive signal generation circuit  216  will be described.  FIG. 7  is a drive waveform illustrating a bias potential, a common drive signal, and a drive signal.  FIG. 8  is a diagram illustrating a deformed state of a vibration plate due to a drive signal, and is a diagram schematically illustrating a cross-section taken along the line VIII-VIII in  FIG. 4 . 
     As illustrated in  FIG. 7 , the common drive signal COM according to the present embodiment is repeatedly generated by the drive signal generation circuit  216  for each unit cycle T defined by a clock signal oscillated by the oscillation circuit  215 . The unit cycle T is also called an ejection cycle T or a recording cycle T, and corresponds to one pixel of an image or the like printed on the recording sheet S. In the present embodiment, the common drive signal COM is a signal having an ejection pulse DP which drives the piezoelectric actuator  300  so that an ink droplet is ejected from the nozzles  21  within one recording cycle T, and is repeatedly generated at each recording cycle T. 
     When a dot pattern for one line (for one raster) is formed in a recording area of the recording sheet S during printing, the ejection pulse DP of the common drive signal COM is selectively applied to the piezoelectric actuator  300  corresponding to each nozzle  21 . That is, an application pulse is generated from a head control signal and the common drive signal COM for each piezoelectric actuator  300  corresponding to each nozzle  21 , and the application pulse is supplied to the piezoelectric actuator  300 . 
     Such an application pulse is supplied to the second electrode  80  which is an individual electrode for each active portion  310  of the piezoelectric actuator  300 . Further, the bias potential vbs is supplied to the first electrode  60 , which is a common electrode of the plurality of active portions  310  of the piezoelectric actuator  300 . Therefore, a potential to be applied to the second electrode  80 , which is an individual electrode of the piezoelectric actuator  300  by the application pulse, is represented with the bias potential vbs to be applied to the first electrode  60  as a reference potential. 
     In the example illustrated in  FIG. 7 , by supplying the bias potential vbs to the first electrode  60 , the first electrode  60  is maintained at a potential of substantially 30 V. 
     The ejection pulse DP represented by a drive waveform having a minimum potential of substantially 30 V and a maximum potential of substantially 60 V is supplied to the second electrode  80 . 
     A potential difference of the second electrode  80  based on a potential of the first electrode  60 , that is, (a potential of the second electrode  80 ) −(the potential of the first electrode  60 ) becomes a drive voltage V for the piezoelectric layer  70 . A profile of the drive voltage V with time is a drive signal  250  to be supplied to the piezoelectric actuator  300 . 
     Here, the drive signal  250  to be supplied to the piezoelectric actuator  300  includes a first contraction maintaining element P 1 , an expansion element P 2 , an expansion maintaining element P 3 , a first contraction element P 4 , a reference volume maintaining element P 5 , a second contraction element P 6 , and a second contraction maintaining element P 7 . 
     The first contraction maintaining element P 1  maintains the volume of the pressure chamber  12  in a state of being contracted from a reference volume by applying a first potential V 1  (here, 10 V) to the piezoelectric actuator  300 . In the present embodiment, the first contraction maintaining element P 1  corresponds to a contraction element described in the aspects. That is, a contraction element which contracts the pressure chamber  12  below the reference volume also includes an element which maintains the pressure chamber  12  in a state of being contracted below the reference volume. 
     Specifically, when a positive (+) potential is applied to the second electrode  80  in the same manner as the first contraction maintaining element P 1 , an electric field from the second electrode  80  toward the first electrode  60  in the +Z-direction is applied to the piezoelectric layer  70 . Since the piezoelectric layer  70  has a polarization direction from the first electrode  60  to the second electrode  80  in the −Z-direction, the electric field in the +Z-direction opposite to the −Z-direction, which is the polarization direction, is applied to the piezoelectric layer  70 . Therefore, the piezoelectric layer  70  is contracted in the −Z-direction, which is the electric field direction, and is extended in an in-plane direction including the X-direction and the Y-direction, which are directions orthogonal to a polarization direction. That is, as illustrated in  FIG. 9 , by applying an electric field E so as to use the region D in the butterfly curve illustrating a relationship of S (an electric field induced strain (a displacement amount)) between E (an electric field) of the piezoelectric layer  70 , the piezoelectric layer  70  can be contracted in the −Z-direction, which is an electric field direction, and can be expanded in an in-plane direction including the X-direction and the Y-direction, which are directions orthogonal to the polarization direction. 
     Since the active portion  310  of the piezoelectric actuator  300  is provided from the outside of the pressure chamber  12  across the edge portion B, the piezoelectric layer  70  is extended in an in-plane direction including the X-direction and the Y-direction, so that the piezoelectric actuator  300  deflects and is deformed toward the pressure chamber  12  side, that is, in the +Z-direction. That is, the state in which the piezoelectric actuator  300  is deformed in a direction of the volume of the pressure chamber  12  being contracted is maintained by the first contraction maintaining element P 1 . As a result, the piezoelectric actuator  300  is maintained in a state of being deformed in the +Z-direction, which is the pressure chamber  12  side. 
     Incidentally, deformation of the piezoelectric actuator  300  in the +Z-direction which is the pressure chamber  12  side includes that a surface, on the +Z side which is the pressure chamber  12  side, of the piezoelectric actuator  300  is deformed in a state of protruding in a convex shape and that a surface, on the −Z side which is the side opposite to the  12  side, of the piezoelectric actuator  300  is in a state of protruding in a convex shape. That is, for example, when the initial deflection of the piezoelectric actuator  300  is deformed so as to protrude in a convex shape toward the −Z side opposite to the pressure chamber  12 , the piezoelectric actuator  300  is deformed by the first contraction maintaining element P 1  so as to protrude in a convex shape to the −Z side, and is deformed so that a protrusion amount to the −Z side is reduced. A posture of the piezoelectric actuator  300  by the first contraction maintaining element P 1  is determined by a characteristic of a stacked film including the vibration plate  50  which determines the initial deflection of the piezoelectric actuator  300 , that is, internal stress of each film or a position of a neutral line, and a magnitude of the first potential V 1  by the first contraction maintaining element P 1  with respect to a displacement characteristic of the piezoelectric layer  70 , that is, a displacement amount. 
     In the present embodiment, as illustrated by the dotted line in  FIG. 8 , in the initial deflection when no potential is applied to the piezoelectric actuator  300 , the piezoelectric actuator  300  has a convex shape on the −Z side, which is opposite to the pressure chamber  12 . In addition, the piezoelectric actuator  300  is deformed in a convex shape toward the pressure chamber  12  side when the first potential V 1  of the first contraction maintaining element P 1  is applied. 
     In this manner, by supplying the first contraction maintaining element P 1 , the piezoelectric actuator  300  can be maintained in a state of being reliably deformed in the +Z-direction, which is the pressure chamber  12  side, regardless of a posture when no potential is applied to the piezoelectric actuator  300 , that is, whatever posture the initial deflection is. That is, even when the initial deflection of the piezoelectric actuator  300  is in a state in which the piezoelectric actuator  300  deformed in a convex shape toward the pressure chamber  12  side and even when the piezoelectric actuator  300  is also deformed in a convex shape toward a side opposite to the pressure chamber  12 , the first contraction maintaining element P 1  is supplied, so that the piezoelectric actuator  300  can be deformed toward the pressure chamber  12  side, and particularly, can be deformed so as to be convex toward the pressure chamber  12  side. Incidentally, the piezoelectric actuator  300  may have an initial deflection having a convex shape toward the +Z side, which is the pressure chamber  12  side. Meanwhile, in the piezoelectric actuator  300 , when the initial deflection is convex toward the −Z side, which is the side opposite to the pressure chamber  12 , a member having compressive stress can be introduced as a member forming the vibration plate  50 . By making the internal stress of the vibration plate  50  the compressive stress in this manner, when tensile stress is applied to the vibration plate  50  by the expansion element P 2 , the expansion maintaining element P 3 , the first contraction element P 4 , and the like, it is possible to suppress damage of the vibration plate  50 . 
     When the electric field applied to the piezoelectric layer  70  made of a dielectric material is changed, the piezoelectric layer  70  has a curve having a hysteresis characteristic in which positive and negative polarities are inverted at a coercive electric field (a coercive electric field Ec 1  on the negative electrode side and a coercive electric field Ec 2  on the positive electrode side), that is, a so-called hysteresis curve is drawn. Therefore, the electric field applied to the piezoelectric layer  70  by the first contraction maintaining element P 1  may be larger than the coercive electric field Ec 1  on the negative electrode side and smaller than the coercive electric field Ec 2  on the positive electrode side. That is, an absolute value of the first potential V 1  which is a potential applied to the piezoelectric actuator  300  by the first contraction maintaining element P 1  may be larger than zero (0) and equal to or less than an absolute value of a potential which becomes the coercive electric fields (Ec 1  and Ec 2 ) of the piezoelectric layer  70 , that is, the so-called a coercive potential Vc (a sum of +Vc and −Vc is referred to as Vc) (0&lt;|V 1 |≤|Vc|). In the present embodiment, the first potential V 1  is a positive (+) potential, so 0&lt;V 1 +Vc may be satisfied. In this manner, the absolute value of the first potential V 1  is set to a value which does not exceed an absolute value of the coercive potential Vc of the piezoelectric layer  70 , so that the first contraction maintaining element P 1  can contract the piezoelectric layer  70  in the −Z-direction, which is a polarization direction, without reversing polarization of the piezoelectric layer  70  by the first contraction maintaining element P 1 . 
     The expansion element P 2  applies the first potential V 1  (10 V) to a second potential V 2  (here, −20 V), to the piezoelectric actuator  300  so as to expand the volume of the pressure chamber  12  from the first contraction maintaining element P 1 . In the present embodiment, the expansion element P 2  corresponds to an expansion element described in the aspects. 
     Specifically, when a negative (−) potential is applied to the second electrode  80  in the same manner as the expansion element P 2 , an electric field from the first electrode  60  to the second electrode  80  in the −Z-direction is applied to the piezoelectric layer  70 . Since the piezoelectric layer  70  has a polarization direction in the −Z-direction, an electric field direction and a polarization direction coincide with each other. As a result, the piezoelectric layer  70  is expanded in the −Z-direction which is the electric field direction and is contracted in the in-plane direction including the X-direction and the Y-direction which are directions orthogonal to the polarization direction. That is, as illustrated in  FIG. 7 , by applying the electric field E so as to use a region F in the butterfly curve illustrating a relationship of S (an electric field induced strain (a displacement amount)) between E (an electric field) of the piezoelectric layer  70 , the piezoelectric layer  70  can be expanded in the −Z-direction, which is an electric field direction, and can be contracted in an in-plane direction including the X-direction and the Y-direction, which are directions orthogonal to the polarization direction. 
     The piezoelectric layer  70  is contracted in the in-plane direction including the X-direction and the Y-direction, so that the piezoelectric actuator  300  deflects and is deformed in the −Z-direction, which is a side opposite to the pressure chamber  12 . In the present embodiment, as illustrated in  FIG. 8 , by the expansion element P 2 , the piezoelectric actuator  300  deflects and is deformed so as to have a convex shape toward the −Z side, which is a side opposite to the pressure chamber  12 . Of course, by the expansion element P 2 , the piezoelectric actuator  300  may be deformed so that only a protrusion amount is reduced while remaining in the convex shape on the +Z side which is the pressure chamber  12  side. 
     In this manner, the expansion element P 2  according to the present embodiment deforms the piezoelectric actuator  300  in a direction in which the volume of the pressure chamber  12  is expanded, so that a meniscus in the nozzle  21  is drawn into the pressure chamber  12  side and ink is supplied from the common liquid chamber  35  side to the pressure chamber  12 . 
     In the present embodiment, since the expansion element P 2  applies the drive voltage V having 30 V from the first potential V 1  (10 V) to the second potential V 2  (−20 V) to the piezoelectric actuator  300 , a volume of ink drawn from the common liquid chamber  35  into the pressure chamber  12  can be increased. That is, when the volume of the pressure chamber  12  before the expansion of the pressure chamber  12  by the expansion element P 2  is a reference volume when a voltage is not applied to the piezoelectric actuator  300 , the drive voltage V having 20 V is only applied to the piezoelectric actuator  300  by the expansion element P 2 . In the present embodiment, the volume of the pressure chamber  12  before the pressure chamber  12  is expanded by the expansion element P 2  is made smaller than the reference volume, so that the volume of the ink drawn from the common liquid chamber  35  into the pressure chamber  12  can be increased by the expansion element P 2 . Therefore, when the volume of the pressure chamber  12  is rapidly contracted by the first contraction element P 4  to eject ink droplets from the nozzles  21 , a weight of the ejected ink droplet can be increased. 
     The expansion maintaining element P 3  continues to apply the second potential V 2  (here, −20 V) to the piezoelectric actuator  300 , and maintains the volume of the pressure chamber  12  expanded by the expansion element P 2  for a certain period. 
     The first contraction element P 4  applies the second potential V 2  to the ground (GND) to the piezoelectric actuator  300  so as to contract the pressure chamber  12  expanded by the expansion maintaining element P 3  up to a reference volume when no potential is applied. 
     As illustrated in  FIG. 8 , the pressure chamber  12  is rapidly contracted from a volume expanded by the expansion maintaining element P 3  up to the reference volume by the first contraction element P 4 , ink inside the pressure chamber  12  is pressurized and the ink droplet is ejected from the nozzle  21 . Since a volume of the ink drawn into the pressure chamber  12  is large in the expansion element P 2  before the first contraction element P 4 , it is possible to increase a weight of the ink droplet ejected from the nozzle  21  by the first contraction element P 4 . That is, since a pressure change in the ink in the pressure chamber  12  caused by the expansion element P 2  is large, a larger pressure change occurs in the pressure chamber  12  when the pressure change of the ink inside the pressure chamber  12  is caused by the first contraction element P 4 , and the weight of the ejected ink droplet can be increased. 
     The reference volume maintaining element P 5  maintains a state in which no potential is applied to the piezoelectric actuator  300  for a certain period and maintains the reference volume for the certain period. 
     By the reference volume maintaining element P 5 , the state in which the pressure chamber  12  is contracted up to the reference volume is maintained for the certain period, and the ink pressure inside the pressure chamber  12  reduced by the ejection of ink droplets during this period is attenuated by repeating an increase and a decrease due to natural vibration of the ink. 
     The second contraction element P 6  applies the ground (GND) to the first potential V 1  (10 V) to the piezoelectric actuator  300  so as to contract the volume of the pressure chamber  12  from the reference volume. 
     The second contraction maintaining element P 7  maintains the volume of the pressure chamber  12  in a state of being contracted from the reference volume by applying a first potential V 1  (here, 10 V) to the piezoelectric actuator  300 . 
     In the same manner as the first contraction maintaining element P 1 , an absolute value of the first potential V 1  in the second contraction element P 6  and the second contraction maintaining element P 7  may not exceed a potential which becomes a coercive electric field of the piezoelectric layer  70 , so-called an absolute value of the coercive potential Vc (0&lt;|V 1 |≤|Vc|). 
     The second contraction element P 6  may supply ink pressure inside the pressure chamber  12  reduced by the first contraction element P 4  in accordance with a timing when the ink pressure in the pressure chamber  12  is increased again by the natural vibration period by the reference volume maintaining element P 5 . As a result, the vibration of the meniscus after the ink droplet is ejected can be attenuated in a short time. 
     With such a drive signal  250 , it can be said that the first potential V 1  is applied as an intermediate potential to the first contraction maintaining element P 1  and the second contraction maintaining element P 7  in a standby state in which ink droplets are not ejected. 
     As described above, the ink jet recording apparatus I which is a liquid ejecting apparatus according to Embodiment 1 of the present disclosure includes the ink jet recording head  1  which is a liquid ejecting head including the flow path formation substrate  10  in which the pressure chamber  12  communicating with the nozzle  21  is formed, the vibration plate  50  formed on one surface side of the flow path formation substrate  10 , and the piezoelectric actuator  300  having the first electrode  60 , the piezoelectric layer  70 , and the second electrode  80  formed on a surface side of the vibration plate  50  opposite to the flow path formation substrate  10 , and the printer controller  210  and the drive circuit  120  which are drive units which supply the drive signal  250  for driving the piezoelectric actuator  300 , in which the piezoelectric actuator  300  includes the active portion  310  in which the piezoelectric layer  70  is interposed between the first electrode  60  and the second electrode  80 , when viewed from the Z-direction, which is a stacking direction of the first electrode  60 , the piezoelectric layer  70 , and the second electrode  80 , in plan view, the active portion  310  extends from the edge portion B, which is a region other than the central portion A of a region facing the pressure chamber  12 , to the outside of the pressure chamber  12 , and the drive signal  250  includes the first contraction maintaining element P 1  which is a contraction element that contracts the pressure chamber  12  from a reference volume of the pressure chamber  12  when no electric field is applied to the piezoelectric layer  70 , and the expansion element P 2  that expands the pressure chamber  12  contracted by the first contraction maintaining element P 1 . 
     In this manner, by providing the first contraction maintaining element P 1  which contracts the pressure chamber  12  below the reference volume before the expansion element P 2  which expands the pressure chamber  12  as the drive signal  250  which drives the piezoelectric actuator  300  having the active portion  310  extending from the edge portion B other than the central portion A to the outside of the pressure chamber  12 , the expansion element P 2  can greatly deform the vibration plate  50  to increase the volume change in the pressure chamber  12 . Therefore, when the pressure chamber  12  is contracted from the expansion element P 2  and an ink droplet, which is a liquid droplet, is ejected from the nozzle  21 , it is possible to increase a weight of the ink droplet. 
     Further, by providing the first contraction maintaining element P 1  in the drive signal  250 , it is not necessary to control initial deflection of the vibration plate  50 . Therefore, since the initial deflection of the vibration plate  50  has a convex shape toward the pressure chamber  12 , it is not necessary to dispose a member having patterned tensile stress, which is not a beam shape, in a member forming the vibration plate  50  and it is possible to suppress the vibration plate  50  from being broken when the tensile stress is applied to the vibration plate  50 . 
     Further, since the weight of the ink droplet ejected from the nozzle  21  can be increased by the drive signal  250 , it is not necessary to widen a width of the pressure chamber  12  in the X-direction so as to increase the volume of the pressure chamber  12  and it is possible to suppress the vibration plate  50  from being broken by expanding the pressure chamber  12  in the X-direction. Further, since it is not necessary to widen the width of the pressure chamber  12  in the X-direction, the pressure chambers  12  can be arranged at a high density in the X-direction, and it is possible to downsize the recording head  1  in the X-direction and to realize printing with high accuracy by arranging the nozzles  21 . 
     Further, in the ink jet recording apparatus I which is a liquid ejecting apparatus according to the present embodiment, the first contraction maintaining element P 1 , which is a contraction element, may apply an electric field opposite to an electric field of the expansion element P 2  to the piezoelectric layer  70 . With this configuration, the first contraction maintaining element P 1  can easily contract the pressure chamber  12  below a reference volume only by applying the electric field in an opposite direction to the expansion element P 2  to the piezoelectric layer  70 . 
     In addition, in the ink jet recording apparatus I which is the liquid ejecting apparatus according to the present embodiment, the first potential V 1 , which is a potential of the first contraction maintaining element P 1  which is a contraction element, may be always applied in a standby state. With this configuration, the first potential V 1  can be continuously applied as an intermediate potential of the piezoelectric actuator  300 , and the drive signal  250  can be simplified. 
     Further, in the ink jet recording apparatus I which is the liquid ejecting apparatus according to the present embodiment, the absolute value of the first potential V 1  which is a potential applied to the piezoelectric actuator  300  by the first contraction maintaining element P 1  which is a contraction element may be smaller than an absolute value of a coercive potential, which is a potential which becomes a coercive electric field of the piezoelectric layer  70 . With this configuration, it is possible to suppress the inversion of the polarization of the piezoelectric layer  70  by the first contraction maintaining element P 1  and efficiently deform the piezoelectric layer  70 . 
     Further, in the ink jet recording apparatus I which is the liquid ejecting apparatus according to the present embodiment, a direction of polarization or a dipole remaining inside the piezoelectric layer when no potential is applied to the piezoelectric actuator  300  is from the first electrode  60  to the second electrode  80  in the −Z-direction, and in the first contraction maintaining element P 1  which is a contraction element, a potential of the second electrode  80  may be set to be positive, and in the expansion element P 2 , a potential of the second electrode  80  may be set to be negative. With this configuration, in the first contraction maintaining element P 1 , by applying a positive potential to the second electrode  80 , the piezoelectric actuator  300  is deformed toward the pressure chamber  12  side, and the pressure chamber  12  can contract below the reference volume. Further, in the expansion element P 2 , by applying a negative potential to the second electrode  80 , the piezoelectric actuator  300  can be deformed to a side opposite to the pressure chamber  12 , and the pressure chamber  12  can be expanded more than the reference volume. 
     Further, in the ink jet recording apparatus I which is the liquid ejecting apparatus according to the present embodiment, the drive signal  250  may further include the first contraction element P 4  which is a second contraction element that contracts the pressure chamber  12  expanded by the expansion element P 2  up to a reference volume after the expansion element P 2 , the reference volume maintaining element P 5  that maintains the pressure chamber  12  at the reference volume for a certain period after the first contraction element P 4 , and the second contraction element P 6  which is a third contraction element that contracts the pressure chamber  12  from the reference volume. With this configuration, by using the ground (GND) potential in the first contraction element P 4  and the reference volume maintaining element P 5 , it is possible to easily create a constant voltage with an appropriate waveform, and to stabilize the ejection. 
     Further, in the ink jet recording apparatus I which is the liquid ejecting apparatus according to the present embodiment, in the first contraction maintaining element P 1  which is a contraction element, the piezoelectric actuator  300  is in a state of being deformed in a convex shape toward the pressure chamber  12  side. With this configuration, a weight of an ink droplet can be increased by deforming the piezoelectric actuator  300  in the convex shape toward the pressure chamber  12  by the first contraction maintaining element P 1 . 
     Further, in a method of driving the recording head  1  which is a liquid ejecting head according to the present embodiment, the recording head  1  includes the flow path formation substrate  10  in which the pressure chamber  12  communicating with the nozzle  21  is formed, the vibration plate  50  formed on one surface side of the flow path formation substrate  10 , and the piezoelectric actuator  300  having the first electrode  60 , the piezoelectric layer  70 , and the second electrode  80  formed on a surface side of the vibration plate  50  opposite to the flow path formation substrate  10 , in which the active portion  310  in which the piezoelectric layer  70  is interposed between the first electrode  60  and the second electrode  80  is not provided in the central portion A of a region facing the pressure chamber  12  in the piezoelectric actuator  300 , and the piezoelectric actuator  300  is driven by the drive signal  250  including the first contraction maintaining element P 1  which is a contraction element that contracts the pressure chamber  12  from the reference volume of the pressure chamber  12  when no electric field is applied to the piezoelectric layer  70 , and that expansion element P 2  that expands the pressure chamber  12  contracted by the first contraction maintaining element P 1 . 
     In this manner, by providing the first contraction maintaining element P 1  which contracts the pressure chamber  12  below the reference volume before the expansion element P 2  which expands the pressure chamber  12  as the drive signal  250  which drives the piezoelectric actuator  300  having the active portion  310  extending from the edge portion B other than the central portion A to the outside of the pressure chamber  12 , the expansion element P 2  can greatly deform the vibration plate  50  to increase the volume change in the pressure chamber  12 . Therefore, when the pressure chamber  12  is contracted from the expansion element P 2  and an ink droplet, which is a liquid droplet, is ejected from the nozzle  21 , it is possible to increase a weight of the ink droplet. 
     Further, by providing the first contraction maintaining element P 1  in the drive signal  250 , it is not necessary to control initial deflection of the vibration plate  50 . Therefore, since the initial deflection of the vibration plate  50  has a convex shape toward the pressure chamber  12 , it is not necessary to dispose a member having patterned tensile stress, which is not a beam shape, in a member forming the vibration plate  50  and it is possible to suppress the vibration plate  50  from being broken when the tensile stress is applied to the vibration plate  50 . 
     Further, since the weight of the ink droplet ejected from the nozzle  21  can be increased by the drive signal  250 , it is not necessary to widen a width of the pressure chamber  12  in the X-direction so as to increase the volume of the pressure chamber  12  and it is possible to suppress the vibration plate  50  from being broken by expanding the pressure chamber  12  in the X-direction. Further, since it is not necessary to widen the width of the pressure chamber  12  in the X-direction, the pressure chambers  12  can be arranged at a high density in the X-direction, and it is possible to downsize the recording head  1  in the X-direction and to realize printing with high accuracy by arranging the nozzles  21 . 
     Embodiment 2 
       FIG. 10  is a drive waveform illustrating a bias potential, a common drive signal, and a drive signal according to Embodiment 2 of the present disclosure. The same reference numerals are given to the same members as the embodiment described above and redundant description will be omitted. 
     As illustrated in  FIG. 10 , a drive signal  251  to be supplied to the piezoelectric actuator  300  includes a first contraction maintaining element P 11 , an expansion element P 12 , an expansion maintaining element P 13 , a contraction element P 14 , and a second contraction maintaining element P 15 . 
     In the same manner as in the first contraction maintaining element P 1  of Embodiment 1, the first contraction maintaining element P 11  maintains the volume of the pressure chamber  12  to be in a state of being contracted from the reference volume by applying the first potential V 1  (here, 10 V) to the piezoelectric actuator  300 . In the present embodiment, the first contraction maintaining element P 11  corresponds to a contraction element described in the aspects. 
     In this manner, by supplying the first contraction maintaining element P 11 , the piezoelectric actuator  300  can be maintained in a state of being reliably deformed in the +Z-direction, which is the pressure chamber  12  side, regardless of a posture when no potential is applied to the piezoelectric actuator  300 , that is, whatever posture the initial deflection is. 
     Further, in the same manner as in Embodiment 1 described above, an absolute value of the first potential V 1  which is a potential applied to the piezoelectric actuator  300  by the first contraction maintaining element P 11  may have a size equal to or less than the absolute value of the coercive potential Vc of the piezoelectric layer  70  (0&lt;|V 1 |≤|Vc|). In this manner, the absolute value of the first potential V 1  is set to a value which does not exceed an absolute value of the coercive potential Vc of the piezoelectric layer  70 , so that the first contraction maintaining element P 1  can contract the piezoelectric layer  70  in the −Z-direction, which is a polarization direction, without reversing polarization of the piezoelectric layer  70  by the first contraction maintaining element P 1 . 
     In the same manner as the expansion element P 2  according to Embodiment 1 described above, the expansion element P 12  applies the first potential V 1  (10 V) to the second potential V 2  (here, −20 V), to the piezoelectric actuator  300  so as to expand the volume of the pressure chamber  12  from the first contraction maintaining element P 11 . In the present embodiment, the expansion element P 12  corresponds to an expansion element described in the aspects. 
     In this manner, the expansion element P 12  according to the present embodiment deforms the piezoelectric actuator  300  in a direction in which the volume of the pressure chamber  12  is expanded, so that a meniscus in the nozzle  21  is drawn into the pressure chamber  12  side and ink is supplied from the common liquid chamber  35  side to the pressure chamber  12 . 
     In the present embodiment, since the expansion element P 12  applies the drive voltage V having 30 V from the first potential V 1  (10 V) to the second potential V 2  (−20 V) to the piezoelectric actuator  300 , a volume of the ink drawn from the common liquid chamber  35  into the pressure chamber  12  can be increased. 
     In the same manner as the expansion maintaining element P 3  according to Embodiment 1 described above, the expansion maintaining element P 13  continues to apply the second potential V 2  (here, −20 V) to the piezoelectric actuator  300  for a certain period, and maintains the volume of the pressure chamber  12  expanded by the expansion element P 12  for a certain period. 
     The contraction element P 14  applies the second potential V 2  (−20 V) to the first potential V 1  (10 V) to the piezoelectric actuator  300  so as to rapidly contract the pressure chamber  12  and eject an ink droplet from the nozzle  21 . Since a volume of the ink drawn into the pressure chamber  12  in the expansion element P 12  before the contraction element P 14  is large, a weight of the ink droplet ejected from the nozzle  21  by the contraction element P 14  can be increased. 
     Further, in the contraction element P 14 , the piezoelectric actuator  300  is deformed from the second potential V 2  to the first potential V 1  so as to contract the pressure chamber  12 , so that the potential to be applied to the piezoelectric actuator  300  is larger than the first contraction element P 4  according to Embodiment 1 described above, and a displacement amount of the piezoelectric actuator  300  can be increased. Therefore, the contraction element P 14  can increase the weight of the ink droplet ejected from the nozzle  21 . 
     The second contraction maintaining element P 15  maintains the contracted volume of the pressure chamber  12  from the reference volume by applying the first potential V 1  (here, 10 V) to the piezoelectric actuator  300 . 
     The first potential V 1  is higher than 0 V and equal to or less than the coercive potential Vc, and when a potential within this range is applied to the piezoelectric layer  70 , an elastic modulus of the piezoelectric layer  70  is increased. Therefore, residual vibration of the ink in the second contraction maintaining element P 15  can be quickly suppressed. Therefore, a drive frequency can be increased, that is, one recording cycle T can be shortened. 
     In the same manner as the first contraction maintaining element P 11 , an absolute value of the first potential V 1  in the second contraction maintaining element P 15  may not exceed a potential which becomes a coercive electric field of the piezoelectric layer  70 , so-called an absolute value of a coercive potential. 
     With such the drive signal  251 , it can be said that the first potential V 1  is applied as an intermediate potential to the first contraction maintaining element P 11  and the second contraction maintaining element P 15  in a standby state in which ink droplets are not ejected. 
     Even in the ink jet recording apparatus I according to the present embodiment as described above, by providing the first contraction maintaining element P 1  which contracts the pressure chamber  12  below the reference volume before the expansion element P 2  which expands the pressure chamber  12  as the drive signal  250  which drives the piezoelectric actuator  300  having the active portion  310  extending from the edge portion B other than the central portion A to the outside of the pressure chamber  12 , the expansion element P 2  can greatly deform the vibration plate  50  to increase the volume change in the pressure chamber  12 . Therefore, when the pressure chamber  12  is contracted from the expansion element P 2  and an ink droplet, which is a liquid droplet, is ejected from the nozzle  21 , it is possible to increase a weight of the ink droplet. 
     Further, by providing the first contraction maintaining element P 1  in the drive signal  250 , it is not necessary to control initial deflection of the vibration plate  50 . Therefore, since the initial deflection of the vibration plate  50  has a convex shape toward the pressure chamber  12 , it is not necessary to dispose a member having patterned tensile stress, which is not a beam shape, in a member forming the vibration plate  50  and it is possible to suppress the vibration plate  50  from being broken when the tensile stress is applied to the vibration plate  50 . 
     Further, since the weight of the ink droplet ejected from the nozzle  21  can be increased by the drive signal  250 , it is not necessary to widen a width of the pressure chamber  12  in the X-direction so as to increase the volume of the pressure chamber  12  and it is possible to suppress the vibration plate  50  from being broken by expanding the pressure chamber  12  in the X-direction. Further, since it is not necessary to widen the width of the pressure chamber  12  in the X-direction, the pressure chambers  12  can be arranged at a high density in the X-direction, and it is possible to downsize the recording head  1  in the X-direction and to realize printing with high accuracy by arranging the nozzles  21 . 
     In addition, after the contraction element P 14 , the second contraction maintaining element P 15  continues to apply the first potential V 1  so as to contract the piezoelectric layer  70  in a polarization direction, it is possible to increase the elastic modulus of the piezoelectric layer  70  and to quickly suppress residual vibration of the ink. Therefore, a drive frequency can be increased, that is, one recording cycle T can be shortened. 
     The drive signal  251  according to the present embodiment is configured such that the second contraction maintaining element P 15  continuously applies the first potential V 1  after an ink droplet is ejected, but the drive signal  251  is not limited to this. Here, a modification example of the drive signal is illustrated in  FIG. 11 . 
     As illustrated in  FIG. 11 , a drive signal  252  to be supplied to the piezoelectric actuator  300  includes the first contraction maintaining element P 11 , the expansion element P 12 , an expansion maintaining element P 13 , the contraction element P 14 , the second contraction maintaining element P 15 , a damping element P 16 , a reference volume maintaining element P 17 , a second contraction element P 18 , and a third contraction maintaining element P 19 . 
     The first contraction maintaining element P 11  to the second contraction maintaining element P 15  have the same manner as in  FIG. 10  described above. 
     Further, the damping element P 16  applies the first potential V 1  to the ground (GND) to the piezoelectric actuator  300  so as to contract the pressure chamber  12  contracted by the contraction element P 14  to a reference volume when no potential is applied. At a timing of applying the damping element P 16 , that is, an application time of the second contraction maintaining element P 15 , ink pressure inside the pressure chamber  12  reduced by the contraction element P 14  is supplied by the second contraction maintaining element P 15  in accordance with a timing when the ink pressure is increased again by the natural vibration period. As a result, the vibration of the meniscus after the ink droplet is ejected can be attenuated in a short time. 
     After the damping element P 16 , the reference volume maintaining element P 17  maintains the reference volume of the pressure chamber  12  for a certain period. 
     After that, the volume of the pressure chamber  12  is contracted from the reference volume by the second contraction element P 18 , and the contracted volume of the pressure chamber  12  is maintained for a certain period by the third contraction maintaining element P 19 . 
     Further, in the present embodiment, the drive signals  251  and  252  have one ejection pulse DP within one recording cycle T, but the present embodiment is not limited to this. Here, another modification example of the drive signal according to the present embodiment is illustrated in  FIG. 12 . 
     As illustrated in  FIG. 12 , a drive signal  253  to be supplied to the piezoelectric actuator  300  includes a first ejection pulse DP 1 , a second ejection pulse DP 2 , and a third ejection pulse DP 3  within one recording cycle T. 
     Although not particularly illustrated, each of the first ejection pulse DP 1 , the second ejection pulse DP 2 , and the third ejection pulse DP 3  has a waveform shape in the same manner as the ejection pulse DP of the drive signal  251 , and has the waveform shape in which a second voltage which is a minimum voltage is different. That is, each of the first ejection pulse DP 1 , the second ejection pulse DP 2 , and the third ejection pulse DP 3  includes the first contraction maintaining element P 11 , the expansion element P 12 , the expansion maintaining element P 13 , the contraction element P 14 , and the second contraction maintaining element P 15 . 
     A minimum potential of the first ejection pulse DP 1  is the second potential V 2 . A second potential V 2A , which is a minimum potential of the second ejection pulse DP 2 , is smaller than the second potential V 2  of the first ejection pulse DP 1 . Further, a second potential V 2B , which is a minimum potential of the third ejection pulse DP 3 , is smaller than the second potential V 2A  of the second ejection pulse DP 2 . 
     When the drive signal  253  including the first ejection pulse DP 1 , the second ejection pulse DP 2 , and the third ejection pulse DP 3  is applied to the piezoelectric actuator  300  within one recording cycle T, a large dot is formed in one pixel of the recording sheet S. 
     On the other hand, with the drive signal  251  illustrated in  FIG. 10 , since one ejection pulse DP is applied to the piezoelectric actuator  300  within one recording cycle T, a small dot is formed in one pixel of the recording sheet S as compared with the drive signal  253 . 
     By selectively using the drive signal  251  and the drive signal  253 , a size of a dot formed in one pixel can be used appropriately, and high-speed and high-accuracy printing can be realized. 
     Further, in the drive signal  253  for forming a large dot, a third potential V 3  applied by the first contraction maintaining element P 11  of each of the ejection pulses DP 1 , DP 2 , and DP 3  is set to be larger than the first potential V 1  applied by the first contraction maintaining element P 11  of the drive signal  251  described above. As a result, a larger dot can be easily formed in one pixel by the drive signal  253 . 
     Incidentally, when a polarization direction of the piezoelectric layer  70  is the +Z-direction or when the first electrode  60  is an individual electrode of each active portion  310 , a potential of the drive signal  253  is inverted, so that the third potential V 3  needs to be smaller than the first potential V 1 . That is, an absolute value of the third potential V 3  of the first contraction maintaining element P 11 , which is a contraction element in the drive signal  253 , may be smaller than an absolute value of the first potential V 1  (|V 3 |&gt;|V 1 |). 
     Of course, the absolute value of the third potential V 3  may be larger than zero (0) and equal to or less than an absolute value of the coercive potential Vc of the piezoelectric layer  70  (0&lt;|V 3 |≤|Vc|). In this manner, by setting the absolute value of the third potential V 3  to a value which does not exceed the absolute value of the coercive potential Vc of the piezoelectric layer  70 , it is possible to suppress polarization of the piezoelectric layer  70  from being inverted even in the drive signal  251 . 
     Further, in the ink jet recording apparatus I, which is a liquid ejecting apparatus according to the present embodiment, in a drive waveform indicating the drive signals  251  and  253  for ejecting ink droplets which are liquid droplets on one pixel, an absolute value of the third potential V 3 , which is a potential applied to the piezoelectric actuator  300  by the contraction element when inputting a plurality of contraction elements and expansion elements, may be larger than an absolute value of the first potential V 1  which is a potential applied to the piezoelectric actuator  300  by the contraction element when inputting one contraction element and expansion element. As a result, a larger dot can be formed in one pixel by the drive signal  253  which applies the third potential V 3  to the piezoelectric actuator  300 . 
     Embodiment 3 
       FIG. 13  is a drive waveform illustrating a bias potential, a common drive signal, and a drive signal according to Embodiment 3 of the present disclosure. The same reference numerals are given to the same members as the embodiment described above and redundant description will be omitted. 
     As illustrated in  FIG. 13 , a drive signal  254  supplied to the piezoelectric actuator  300  includes a first contraction maintaining element P 21 , a first expansion element P 22 , an expansion maintaining element P 23 , a contraction element P 24 , a second contraction maintaining element P 25 , a return element P 26 , and a third contraction maintaining element P 27 . 
     Each of the first contraction maintaining element P 21 , the first expansion element P 22 , and the expansion maintaining element P 23  has the same manner as the first contraction maintaining element P 1 , the expansion element P 2 , and the expansion maintaining element P 3  according to Embodiment 1 described above, and therefore redundant description will be omitted. In the present embodiment, the first contraction maintaining element P 21  and the first expansion element P 22  respectively correspond to a contraction element and an expansion element described in the aspects. 
     The contraction element P 24  applies the second potential V 2  (−20 V) to a fourth potential V 4  (here, 15 V) larger than the first potential V 1  (10 V) according to Embodiments 1 and 2 described above to the piezoelectric actuator  300 , so that the pressure chamber  12  expanded by the expansion maintaining element P 23  is contracted up to a volume smaller than a reference volume. 
     The contraction element P 24  pressurizes ink inside the pressure chamber  12  to eject an ink droplet from the nozzle  21 . In the present embodiment, the contraction element P 24  applies the second potential V 2  (−20 V) to the fourth potential V 4  (here, 15 V) larger than the first potential V 1  (10 V) to the piezoelectric actuator  300 , so that the piezoelectric actuator  300  can be deformed more than in Embodiment 2 described above, and a weight of the ink droplet ejected from the nozzle  21  can be further increased. 
     Incidentally, when a polarization direction of the piezoelectric layer  70  is the +Z-direction or when the first electrode  60  is an individual electrode of each active portion  310 , a potential of the drive signal  254  is inverted, so that the fourth potential V 4  needs to be smaller than the first potential V 1 . That is, an absolute value of the fourth potential V 4  of the contraction element P 24  in the drive signal  254  may be larger than an absolute value of the first potential V 1  (|V 4 |&gt;|V 1 |). 
     In the same manner as in the first potential V 1 , the absolute value of the fourth potential V 4  may be larger than zero (0) and equal to or less than an absolute value of the coercive potential Vc of the piezoelectric layer  70  (0&lt;|V 4 |≤|Vc|). In this manner, the absolute value of the first potential V 1  is set to a value which does not exceed an absolute value of the coercive potential Vc of the piezoelectric layer  70 , so that the contraction element P 24  can contract the piezoelectric layer  70  in the −Z-direction, which is a polarization direction, without reversing polarization of the piezoelectric layer  70  by the contraction element P 24 . 
     The second contraction maintaining element P 25  continues to apply the fourth potential V 4  (15 V) to the piezoelectric actuator  300  for a certain period so as to maintain a volume of the pressure chamber  12  contracted by the contraction element P 24  for the certain period. 
     The return element P 26  applies the fourth potential V 4  (15 V) to the first potential V 1  (10 V) to the piezoelectric actuator  300  so as to contract the volume of the pressure chamber  12  to be larger than the volume of the pressure chamber  12  contracted by the second contraction maintaining element P 25  and smaller than a reference volume. By supplying the potential in the pressure chamber  12  in accordance with a timing when pressure in the pressure chamber  12  is increased again by the natural vibration period, the return element P 26  can damp the vibration of the meniscus after the ink droplet is ejected, in a short time. 
     The third contraction maintaining element P 27  maintains the volume of the pressure chamber  12  in a state of being contracted from the reference volume by applying the first potential V 1  (10 V) to the piezoelectric actuator  300 . 
     With such the drive signal  254 , it can be said that the first potential V 1  is applied as an intermediate potential to the first contraction maintaining element P 21  and the third contraction maintaining element P 27  in a standby state in which ink droplets are not ejected. 
     Even in the ink jet recording apparatus I according to the present embodiment as described above, by providing the first contraction maintaining element P 1  which contracts the pressure chamber  12  below the reference volume before the expansion element P 2  which expands the pressure chamber  12  as the drive signal  250  which drives the piezoelectric actuator  300  having the active portion  310  extending from the edge portion B other than the central portion A to the outside of the pressure chamber  12 , the expansion element P 2  can greatly deform the vibration plate  50  to increase the volume change in the pressure chamber  12 . Therefore, when the pressure chamber  12  is contracted from the expansion element P 2  and an ink droplet, which is a liquid droplet, is ejected from the nozzle  21 , it is possible to increase a weight of the ink droplet. 
     Further, by providing the first contraction maintaining element P 1  in the drive signal  250 , it is not necessary to control initial deflection of the vibration plate  50 . Therefore, since the initial deflection of the vibration plate  50  has a convex shape toward the pressure chamber  12 , it is not necessary to dispose a member having patterned tensile stress, which is not a beam shape, in a member forming the vibration plate  50  and it is possible to suppress the vibration plate  50  from being broken when the tensile stress is applied to the vibration plate  50 . 
     Further, since the weight of the ink droplet ejected from the nozzle  21  can be increased by the drive signal  250 , it is not necessary to widen a width of the pressure chamber  12  in the X-direction so as to increase the volume of the pressure chamber  12  and it is possible to suppress the vibration plate  50  from being broken by expanding the pressure chamber  12  in the X-direction. Further, since it is not necessary to widen the width of the pressure chamber  12  in the X-direction, the pressure chambers  12  can be arranged at a high density in the X-direction, and it is possible to downsize the recording head  1  in the X-direction and to realize printing with high accuracy by arranging the nozzles  21 . 
     In addition, after the contraction element P 24 , the second contraction maintaining element P 25  continues to apply the fourth potential V 4  so as to contract the piezoelectric layer  70  in a polarization direction, it is possible to increase the elastic modulus of the piezoelectric layer  70  and to quickly suppress residual vibration of the ink. Therefore, a drive frequency can be increased, that is, one recording cycle T can be shortened. 
     Other Embodiment 
     Each of the embodiments of the disclosure is described above, but a basic configuration of the disclosure is not limited to thereto. 
     For example, in each of the embodiments described above, the direction of the polarization or dipole of the piezoelectric layer  70  (collectively referred to as the polarization direction) is from the first electrode  60  to the second electrode  80  in the −Z-direction, but the embodiment is not limited thereto. For example, the polarization direction of the piezoelectric layer  70  may be from the second electrode  80  toward the first electrode  60  in the +Z-direction. In this manner, when the polarization direction of the piezoelectric layer  70  is the +Z-direction, the potentials of the drive signals  250  to  254  described above may be inverted. For example,  FIG. 14  illustrates a drive signal  250 A obtained by inverting the potential of the drive signal  250  in  FIG. 7 . Further,  FIG. 15  illustrates a drive signal  251 A obtained by inverting the potential of the drive signal  251  in  FIG. 10 . That is, as illustrated in  FIGS. 14 and 15 , in the drive signals  250 A and  251 A, in the first contraction maintaining elements P 1  and P 11  which are contraction elements, the first potential V 1  is applied so that the second electrode  80  becomes negative (−) based on the first electrode  60 . Further, in the expansion elements P 2  and P 12 , the second potential V 2  is applied so that the second electrode  80  becomes positive (+) based on the first electrode  60 . 
     As described above, in the ink jet recording apparatus I which is the liquid ejecting apparatus according to the present embodiment, a direction of polarization or a dipole remaining inside the piezoelectric layer  70  when no potential is applied to the piezoelectric actuator  300  is from the second electrode  80  to the first electrode  60  in the +Z-direction, and in the first contraction maintaining elements P 1  and P 11  which are contraction elements, a potential of the second electrode  80  may be set to be negative, and in the expansion element P 2 , a potential of the second electrode  80  may be set to be positive. As a result, in the first contraction maintaining elements P 1  and P 11 , by applying a negative potential to the second electrode  80 , the piezoelectric actuator  300  is deformed toward the pressure chamber  12  side, and the pressure chamber  12  can contract below the reference volume. Further, in the expansion elements P 2  and P 12 , by applying a positive potential to the second electrode  80 , the piezoelectric actuator  300  can be deformed to a side opposite to the pressure chamber  12 , and the pressure chamber  12  can be expanded more than the reference volume. 
     Further, in each of the above-described embodiments, the first electrode  60  is a common electrode of the plurality of active portions  310 , the second electrode  80  is an individual electrode of each active portion  310 , and the drive signal  250  is supplied to the second electrode  80 , but the embodiment is not limited to this. For example, the first electrode  60  may be divided into individual electrodes for each active portion  310 , and the second electrode  80  may be a common electrode which is common across the plurality of active portions  310 . When the first electrode  60  is the individual electrode, even when the polarization direction of the piezoelectric layer  70  is from the first electrode  60  toward the second electrode  80  in the −Z-direction, a drive signal obtained by inverting the potential of the drive signals  250  to  254 , for example, the drive signals  250 A and  251 A illustrated in  FIGS. 14 and 15  may be supplied to the first electrode  60 . 
     Further, in each of the above-described embodiments, the drive signals  250  to  254  for ejecting ink droplets have the contraction element and the expansion element, but the present embodiment is not particularly limited to this, and for a drive signal such as a micro-vibration drive not ejecting ink droplets, the drive signal including a contraction element and an expansion element may be used even in the same manner as in each of the above-described embodiments. 
     Further, in each of the above-described embodiments, the drive circuit  120  supplies the positive (+) common drive signal COM to the second electrode  80  which is an individual electrode, and the positive (+) bias potential vbs is applied to the first electrode  60  which is a common electrode, so that the drive signals  250  to  254  having a potential difference having positive (+) and negative (−) of the second electrode  80  based on a potential of the first electrode  60  are supplied to the piezoelectric actuator  300 , but the present embodiment is not limited to this. For example, the first electrode  60  which is a common electrode is used as a ground (GND), and the drive signals  250  to  254  having positive (+) and negative (−) may be directly supplied from the drive circuit  120  to the second electrode  80  which is an individual electrode. Meanwhile, a drive circuit which supplies a drive signal having only positive (+) is less expensive than a drive circuit configured to supply a drive signal having positive (+) and negative (−). Therefore, as in each of the above-described embodiments, by supplying the drive signals  250  to  254  having positive (+) and negative (−) to the piezoelectric actuator  300  by using the positive (+) common drive signal COM and the plus (+) bias potential vbs, it is possible to use the inexpensive drive circuit  120 , and to reduce a cost. 
     Further, in the drive signals  250  to  254  of each of the above-described embodiments, the first potential V 1  is applied as the intermediate potential in the standby state in which ink droplets are not ejected, but the present embodiment is not limited to this. Here, a modification example of the drive signal is illustrated in  FIG. 16 .  FIG. 16  is a drive waveform illustrating a drive signal according to another embodiment. 
     As illustrated in  FIG. 16 , the drive signal  255  to be supplied to the piezoelectric actuator  300  includes a first contraction element P 31 , a contraction maintaining element P 32 , an expansion element P 33 , an expansion maintaining element P 34 , and a second contraction element P 35 . 
     The first contraction element P 31  applies the ground (GND) to the first potential V 1  (here, 10 V) to the piezoelectric actuator  300  so as to contract the pressure chamber  12  below a reference volume. 
     The contraction maintaining element P 32  maintains the contracted volume of the pressure chamber  12  for a certain period. In the example illustrated in  FIG. 16 , the contraction maintaining element P 32  or the first contraction element P 31  and the contraction maintaining element P 32  correspond to a contraction element described in the aspects. 
     The expansion element P 33  applies the first potential V 1  (10 V) to the second potential V 2  (here, −20 V), to the piezoelectric actuator  300  so as to expand the volume of the pressure chamber  12  from the contraction maintaining element P 32 . In the present embodiment, the expansion element P 33  corresponds to an expansion element described in the aspects. 
     The expansion maintaining element P 34  continues to apply the second potential V 2  (here, −20 V) to the piezoelectric actuator  300 , and maintains the volume of the pressure chamber  12  expanded by the expansion element P 33  for a certain period. 
     The second contraction element P 35  applies the second potential V 2  to the ground (GND) to the piezoelectric actuator  300  so as to rapidly contract the pressure chamber  12  expanded by the expansion maintaining element P 34  up to a reference volume when no potential is applied. Pressure of ink inside the pressure chamber  12  is increased by the second contraction element P 35 , and an ink droplet is ejected from the nozzle  21 . 
     In such a drive signal  255 , an intermediate potential is the ground (GND), and the contraction maintaining element P 32  which is a contraction element for contracting the pressure chamber  12  up to a volume smaller than the reference volume may be temporarily supplied before the expansion element P 33  which expands the pressure chamber  12  below the reference volume so as to eject ink droplets. 
     In addition, in the example described above, in the ink jet recording apparatus I, the ink cartridge  2  which is a liquid storage unit is mounted on the carriage  3 , but the example is not limited thereto. For example, the liquid storage unit such as an ink tank may be fixed to the apparatus main body  4  and the liquid storage unit and the recording head  1  may be coupled via a supply pipe such as a tube. Further, the liquid storage unit may be not mounted on the ink jet recording apparatus. 
     In addition, in the above-described ink jet recording apparatus I, the recording head  1  is mounted on the carriage  3  and moved in the Y-direction which is a main scanning direction, but the present disclosure is not particularly limited to this, and for example, the present disclosure can also be applied to a so-called line type recording apparatus in which the recording head  1  is fixed and printing is performed only by moving the recording sheet S such as paper in the X-direction which is a sub-scanning direction. 
     Further, the disclosure is widely applicable to a liquid ejecting head, and can be applied to a recording head such as various ink jet recording heads used in an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter for liquid crystal display and the like, an electrode material ejecting head used for forming an electrode of organic EL displays, field emission display (FED), and the like, a bio-organic substance ejecting head used for manufacturing a biochip, and the like, for example.