JP2015009370A - Piezoelectric actuator and liquid discharge head and recording device using piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator that hardly causes a decline in displacement amount even when driven repeatedly and a liquid discharge head and a recording device that use the piezoelectric actuator.SOLUTION: A piezoelectric actuator includes: a fixation member 22 having an opening portion 10; a diaphragm 21a; a piezoelectric layer 21b; and a pair of electrodes 34, 35a. A portion of the piezoelectric layer 21b that is superposed on the opening portion 10 includes a driving portion 51 sandwiched between the pair of electrodes 34, 35a and a non-driving portion 52 that is not sandwiched. A main component of the piezoelectric layer 21b is potassium sodium niobate. A ratio of Mn to 100 pts.mass of the main component in the driving portion 51 is larger than that in the non-driving portion 52.

Description

  The present invention relates to a piezoelectric actuator, a liquid discharge head using the same, and a recording apparatus.

  In recent years, printing apparatuses using inkjet recording methods such as inkjet printers and inkjet plotters are not only printers for general consumers, but also, for example, formation of electronic circuits, manufacture of color filters for liquid crystal displays, manufacture of organic EL displays It is also widely used for industrial applications.

  In such an ink jet printing apparatus, a liquid discharge head for discharging liquid is mounted as a print head. This type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, heats and boiles the ink with the heater, pressurizes the ink with bubbles generated in the ink flow path, A thermal head system that ejects ink as droplets from the ink ejection holes, and a part of the wall of the ink channel filled with ink is bent and displaced by a displacement element, and the ink in the ink channel is mechanically pressurized, and the ink A piezoelectric method for discharging liquid droplets from discharge holes is generally known.

  In addition, in such a liquid discharge head, a serial type that performs recording while moving the liquid discharge head in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium, and main scanning from the recording medium There is a line type in which recording is performed on a recording medium conveyed in the sub-scanning direction with a liquid discharge head that is long in the direction fixed. The line type has the advantage that high-speed recording is possible because there is no need to move the liquid discharge head as in the serial type.

  In order to print droplets at a high density in any of the serial type and line type liquid discharge heads, the density of the discharge holes for discharging the droplets formed in the liquid discharge head is increased. There is a need.

  Therefore, a piezoelectric actuator substrate having a fluid discharge head, a flow path member having discharge holes connecting the manifold and the manifold via a plurality of pressurization chambers, and a plurality of displacement elements provided so as to cover the pressurization chambers, respectively. Is known (see, for example, Patent Document 1). In this liquid ejection head, the pressurizing chambers connected to the plurality of ejection holes are arranged in a matrix, and the displacement elements of the piezoelectric actuator substrate provided so as to cover the chambers are displaced by deformation of the piezoelectric body. Ink is ejected from the ejection holes, and printing is possible at a resolution of 600 dpi in the main scanning direction.

  Moreover, potassium sodium niobate is known as a composition of the piezoelectric body (see, for example, Patent Document 2).

JP 2003-305852 A JP 2011-155272 A

However, when potassium sodium niobate is used as the piezoelectric body of the piezoelectric actuator used in the liquid discharge head described in Patent Document 2, the amount of displacement after many driving operations is less than the initial amount of displacement. There was a problem of becoming low.

  Accordingly, an object of the present invention is to provide a piezoelectric actuator that is unlikely to cause a decrease in displacement even when repeatedly driven, and a liquid discharge head and a recording apparatus using the piezoelectric actuator.

  The piezoelectric actuator of the present invention includes a fixing member having an opening, a diaphragm laminated on the fixing member so as to cover the opening, and a laminate on the diaphragm so as to cover the opening. A piezoelectric actuator, and a pair of electrodes disposed so as to sandwich the piezoelectric layer located on the opening, and the piezoelectric actuator when viewed in plan In the part of the body layer that overlaps the opening, there is a drive part that is sandwiched between the pair of electrodes and a non-drive part that is not sandwiched between the pair of electrodes. The piezoelectric element layer is mainly composed of potassium sodium niobate, and at least the driving part contains Mn, and the piezoelectric layer is disposed along the outer periphery of the opening. To 100 parts by mass of the main component When the ratio of Mn converted to MnO is MN1 [parts by mass], and the ratio of Mn to MnO with respect to 100 parts by mass of the main component in the non-driving part on the outer periphery of the opening is MN2 [parts by mass], 2 .5 ≦ MN1-MN2 ≦ 25.

  In addition, the piezoelectric actuator of the present invention includes a fixing member having an opening, a diaphragm laminated on the fixing member so as to cover the opening, and an upper surface of the diaphragm so as to cover the opening. And a pair of electrodes arranged so as to sandwich the piezoelectric layer located on the opening, when viewed in plan view, In the portion of the piezoelectric layer that overlaps with the opening, there is a drive unit that is sandwiched between the pair of electrodes and a non-drive unit that is not sandwiched between the pair of electrodes, The non-driving part is disposed along the outer periphery of the opening, and the piezoelectric layer is mainly composed of potassium sodium niobate, and at least the driving part contains Cu, and the driving 100 masses of the main component in parts The ratio of Cu to CuO equivalent to CU1 [parts by mass] and the ratio of Cu to CuO equivalent to 100 parts by mass of the main component in the non-driving part on the outer periphery of the opening is CU2 [parts by mass]. .5 ≦ CU1-CU2 ≦ 25.

In addition, the piezoelectric actuator of the present invention includes a fixing member having an opening, a diaphragm laminated on the fixing member so as to cover the opening, and an upper surface of the diaphragm so as to cover the opening. And a pair of electrodes arranged so as to sandwich the piezoelectric layer located on the opening, when viewed in plan view, In the portion of the piezoelectric layer that overlaps with the opening, there is a drive unit that is sandwiched between the pair of electrodes and a non-drive unit that is not sandwiched between the pair of electrodes, The non-driving part is disposed along the outer periphery of the opening, and the piezoelectric layer is mainly composed of potassium sodium niobate, and at least the driving part contains Cu, and the driving 100 masses of the main component in parts Cr of _Cr 2 _{O 3} ratio of converting the CR1 [parts by weight], a proportion of the terms _{of Cr} 2 _{O 3} and Cr relative to the main component as 100 parts by weight of the non-driving portion on the periphery of the opening CR2 for [parts by ], 1.25 ≦ CR1−CR2 ≦ 15.

  Furthermore, the liquid discharge head of the present invention includes a plurality of the piezoelectric actuators, and includes a plurality of discharge holes respectively connected to the plurality of openings.

Furthermore, the recording apparatus of the present invention includes the liquid discharge head, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the plurality of piezoelectric actuators. And

  According to the piezoelectric actuator of the present invention, it is difficult for the displacement amount to decrease even if the driving is repeated.

1 is a schematic configuration diagram of a printer that is a recording apparatus according to an embodiment of the present invention. FIG. 2 is a plan view showing a head body that constitutes the liquid ejection head of FIG. 1. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. (A) is a longitudinal cross-sectional view along the VV line of FIG. 3, (b) is a top view. (A)-(d) is a fragmentary sectional view which shows operation | movement of a displacement element. (A) is a longitudinal cross-sectional view of the other piezoelectric actuator of this invention, (b) is a top view.

  FIG. 1 is a schematic configuration diagram of a color inkjet printer which is a recording apparatus according to an embodiment of the present invention. This color inkjet printer 1 (hereinafter referred to as printer 1) has four liquid ejection heads 2. These liquid discharge heads 2 are arranged along the conveyance direction of the printing paper P and are fixed to the printer 1. The liquid discharge head 2 has an elongated shape in a direction from the front to the back in FIG.

  In the printer 1, a paper feed unit 114, a transport unit 120, and a paper receiver 116 are sequentially provided along the transport path of the printing paper P. In addition, the printer 1 is provided with a control unit 100 for controlling the operation of each unit of the printer 1 such as the liquid discharge head 2 and the paper feeding unit 114.

  The paper supply unit 114 includes a paper storage case 115 that can store a plurality of printing papers P, and a paper supply roller 145. The paper feed roller 145 can send out the uppermost print paper P among the print papers P stacked and stored in the paper storage case 115 one by one.

  Between the paper feed unit 114 and the transport unit 120, two pairs of feed rollers 118a and 118b and 119a and 119b are arranged along the transport path of the printing paper P. The printing paper P sent out from the paper supply unit 114 is guided by these feed rollers and further sent out to the transport unit 120.

  The transport unit 120 includes an endless transport belt 111 and two belt rollers 106 and 107. The conveyor belt 111 is wound around belt rollers 106 and 107. The conveyor belt 111 is adjusted to such a length that it is stretched with a predetermined tension when it is wound around two belt rollers. Thus, the conveyor belt 111 is stretched without slack along two parallel planes each including a common tangent line of the two belt rollers. Of these two planes, the plane closer to the liquid ejection head 2 is a transport surface 127 that transports the printing paper P.

  As shown in FIG. 1, a conveyance motor 174 is connected to the belt roller 106. The transport motor 174 can rotate the belt roller 106 in the direction of arrow A. The belt roller 107 can rotate in conjunction with the transport belt 111. Therefore, the conveyance belt 111 moves along the direction of arrow A by driving the conveyance motor 174 and rotating the belt roller 106.

  In the vicinity of the belt roller 107, a nip roller 138 and a nip receiving roller 139 are arranged so as to sandwich the conveyance belt 111. The nip roller 138 is urged downward by a spring (not shown). A nip receiving roller 139 below the nip roller 138 receives the nip roller 138 biased downward via the conveying belt 111. The two nip rollers are rotatably installed and rotate in conjunction with the conveyance belt 111.

  The printing paper P sent out from the paper supply unit 114 to the transport unit 120 is sandwiched between the nip roller 138 and the transport belt 111. As a result, the printing paper P is pressed against the transport surface 127 of the transport belt 111 and is fixed on the transport surface 127. The printing paper P is transported in the direction in which the liquid ejection head 2 is installed according to the rotation of the transport belt 111. The outer peripheral surface 113 of the conveyor belt 111 may be treated with adhesive silicon rubber. Thereby, the printing paper P can be securely fixed to the transport surface 127.

  The four liquid discharge heads 2 are arranged close to each other along the conveyance direction by the conveyance belt 111. Each liquid discharge head 2 has a head body 13 at the lower end. A large number of ejection holes 8 for ejecting liquid are provided on the lower surface of the head body 13 (see FIG. 3).

  Liquid droplets (ink) of the same color are ejected from the ejection holes 8 provided in one liquid ejection head 2. The ejection holes 8 of each liquid ejection head 2 are arranged at equal intervals in one direction (a direction parallel to the printing paper P and perpendicular to the conveyance direction of the printing paper P, and the longitudinal direction of the liquid ejection head 2). Can print without gaps in the direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. Each liquid ejection head 2 is disposed with a slight gap between the lower surface of the head body 13 and the transport surface 127 of the transport belt 111.

  The printing paper P transported by the transport belt 111 passes through the gap between the liquid ejection head 2 and the transport belt 111. At that time, droplets are ejected from the head main body 13 constituting the liquid ejection head 2 toward the upper surface of the printing paper P. As a result, a color image based on the image data stored by the control unit 100 is formed on the upper surface of the printing paper P.

  A separation plate 140 and two pairs of feed rollers 121a and 121b and 122a and 122b are arranged between the transport unit 120 and the paper receiver 116. The printing paper P on which the color image is printed is conveyed to the peeling plate 140 by the conveying belt 111. At this time, the printing paper P is peeled from the transport surface 127 by the right end of the peeling plate 140. Then, the printing paper P is sent out to the paper receiving unit 116 by the feed rollers 121a to 122b. In this way, the printed printing paper P is sequentially sent to the paper receiving unit 116 and stacked on the paper receiving unit 116.

Note that a paper surface sensor 133 is installed between the liquid ejection head 2 and the nip roller 138 that are the most upstream in the transport direction of the printing paper P. The paper surface sensor 133 includes a light emitting element and a light receiving element, and can detect the leading end position of the printing paper P on the transport path. The detection result by the paper surface sensor 133 is sent to the control unit 100. The control unit 100 can control the liquid ejection head 2, the conveyance motor 174, and the like so that the conveyance of the printing paper P and the printing of the image are synchronized based on the detection result sent from the paper surface sensor 133.

  Next, the head main body 13 constituting the liquid discharge head of the present invention will be described. FIG. 2 is a plan view showing the head main body 13 shown in FIG. FIG. 3 is an enlarged plan view of a region surrounded by a one-dot chain line in FIG. 2 and is a part of the head main body 13. In FIG. 3, for the sake of explanation, some of the flow paths are omitted. FIG. 4 is an enlarged plan view at the same position as FIG. 3, and a part of the flow path different from FIG. 3 is omitted. 3 and 4, in order to make the drawings easy to understand, the pressurizing chamber 10 (pressurizing chamber group 9), the squeezing chamber 12, the discharge hole 8, and the like that are to be drawn by broken lines below the piezoelectric actuator substrate 21 are illustrated. It is drawn with solid lines. FIG. 5A is a longitudinal sectional view taken along line VV in FIG. 3, and FIG. 5B is a plan view of the same part.

  The head body 13 has a flat plate-like flow path member (fixing member) 4 and a piezoelectric actuator substrate 21 on the flow path member 4. The piezoelectric actuator substrate 21 has a trapezoidal shape, and is disposed on the upper surface of the flow path member 4 so that a pair of parallel opposing sides of the trapezoid is parallel to the longitudinal direction of the flow path member 4. In addition, two piezoelectric actuator substrates 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of the two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator substrates 21 adjacent to each other on the flow path member 4 partially overlap in the short direction of the flow path member 4. In the area printed by driving the overlapping piezoelectric actuator substrate 21, the droplets ejected by the two piezoelectric actuator substrates 21 are mixed and landed.

  A manifold 5 that is a part of the liquid flow path is formed inside the flow path member 4. The manifold 5 has an elongated shape extending along the longitudinal direction of the flow path member 4, and an opening 5 b of the manifold 5 is formed on the upper surface of the flow path member 4. A total of ten openings 5 b are formed along each of two straight lines (imaginary lines) parallel to the longitudinal direction of the flow path member 4. The opening 5b is formed at a position that avoids a region where the four piezoelectric actuator substrates 21 are disposed. The manifold 5 is supplied with liquid from a liquid tank (not shown) through the opening 5b.

  The manifold 5 formed in the flow path member 4 is branched into a plurality of branches (the manifold 5 at the branched portion may be referred to as a sub-manifold 5a). The manifold 5 connected to the opening 5 b extends along the oblique side of the piezoelectric actuator substrate 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In the region sandwiched between the two piezoelectric actuator substrates 21, one manifold 5 is shared by the adjacent piezoelectric actuator substrates 21, and the sub-manifold 5 a is branched from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the head main body 13 adjacent to each other in regions facing the piezoelectric actuator substrates 21 inside the flow path member 4.

  The flow path member 4 has four pressure chamber groups 9 in which a plurality of pressure chambers 10 are formed in a matrix (that is, two-dimensionally and regularly). The pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The pressurizing chamber 10 is formed so as to open on the upper surface of the flow path member 4. These pressurizing chambers 10 are arranged over almost the entire surface of the upper surface of the flow path member 4 facing the piezoelectric actuator substrate 21. Accordingly, each pressurizing chamber group 9 formed by these pressurizing chambers 10 occupies a region having substantially the same shape as the piezoelectric actuator substrate 21. Further, the opening of each pressurizing chamber 10 is closed by adhering the piezoelectric actuator substrate 21 to the upper surface of the flow path member 4.

In the present embodiment, as shown in FIG. 3, the manifold 5 branches into four rows of E1-E4 sub-manifolds 5a arranged in parallel with each other in the short direction of the flow path member 4, and each sub-manifold The pressurizing chambers 10 connected to 5a constitute a row of the pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the four rows are arranged in parallel to each other in the lateral direction. Two rows of the pressure chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

  As a whole, the pressurizing chambers 10 connected from the manifold 5 constitute rows of the pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are arranged in 16 rows parallel to each other in the short side direction. ing. The number of pressurizing chambers 10 included in each pressurizing chamber row is arranged so as to gradually decrease from the long side toward the short side corresponding to the outer shape of the displacement element 50 that is an actuator. . The discharge holes 8 are also arranged in the same manner. As a result, it is possible to form an image with a resolution of 600 dpi in the longitudinal direction as a whole. That is, the individual flow paths 32 are connected to each sub-manifold 5a at intervals corresponding to 150 dpi on average. This is because when the discharge holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a, the individual flow paths 32 connected to the sub-manifolds 5a are not always connected at equal intervals. In other words, the individual flow paths 32 are formed at intervals of an average of 170 μm (25.4 mm / 150 = 169 μm intervals if 150 dpi) in the main scanning direction.

  Drive electrodes 35 to be described later are formed at positions facing the pressurizing chambers 10 on the upper surface of the piezoelectric actuator substrate 21. The drive electrode 35 is slightly smaller than the pressurizing chamber 10, has a shape substantially similar to the pressurizing chamber 10, and is disposed so as to be within a region facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21. ing.

  A large number of discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These discharge holes 8 are arranged at positions avoiding the area facing the sub-manifold 5a arranged on the lower surface side of the flow path member 4. Further, these discharge holes 8 are arranged in a region facing the piezoelectric actuator substrate 21 on the lower surface side of the flow path member 4. These discharge hole groups 7 occupy regions having substantially the same shape as the piezoelectric actuator substrate 21, and droplets can be discharged from the discharge holes 8 by displacing the corresponding displacement elements 50 of the piezoelectric actuator substrate 21. The arrangement of the discharge holes 8 will be described in detail later. The discharge holes 8 in each region are arranged at equal intervals along a plurality of straight lines parallel to the longitudinal direction of the flow path member 4.

  The flow path member 4 included in the head body 13 has a stacked structure in which a plurality of plates are stacked. These plates are a cavity plate 22, a base plate 23, an aperture (squeezing) plate 24, supply plates 25 and 26, manifold plates 27, 28 and 29, a cover plate 30 and a nozzle plate 31 in order from the upper surface of the flow path member 4. is there. A number of holes are formed in these plates. Each plate is aligned and laminated so that these holes communicate with each other to form the individual flow path 32 and the sub-manifold 5a. As shown in FIG. 5A, the head main body 13 is individually provided with the pressurizing chamber 10 on the upper surface of the flow path member 4, the sub-manifold 5a on the inner lower surface side, and the discharge holes 8 on the lower surface. Each part constituting the flow path 32 is disposed close to each other at different positions, and the sub-manifold 5 a and the discharge hole 8 are connected via the pressurizing chamber 10.

  The holes formed in each plate will be described. These holes include the following. First, the pressurizing chamber 10 formed in the cavity plate 22. Secondly, there is a communication hole that constitutes a flow path that connects from one end of the pressurizing chamber 10 to the sub-manifold 5a. This communication hole is formed in each plate from the base plate 23 (specifically, the inlet of the pressurizing chamber 10) to the supply plate 25 (specifically, the outlet of the sub-manifold 5a). The communication hole includes the aperture 12 formed in the aperture plate 24 and the individual supply flow path 6 formed in the supply plates 25 and 26.

  Third, there is a communication hole constituting a flow path communicating from the other end of the pressurizing chamber 10 to the discharge hole 8, and this communication hole is referred to as a descender (partial flow path) in the following description. The descender is formed on each plate from the base plate 23 (specifically, the outlet of the pressurizing chamber 10) to the nozzle plate 31 (specifically, the discharge hole 8). Fourthly, there is a communication hole constituting the sub-manifold 5a. The communication holes are formed in the manifold plates 27-30.

  Such communication holes are connected to each other to form an individual flow path 32 extending from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the discharge hole 8. The liquid supplied to the sub-manifold 5a is discharged from the discharge hole 8 through the following path. First, from the sub-manifold 5a, it passes through the individual supply flow path 6 and reaches one end of the aperture 12. Next, it proceeds horizontally along the extending direction of the aperture 12 and reaches the other end of the aperture 12. From there, it reaches one end of the pressurizing chamber 10 upward. Furthermore, it progresses horizontally along the extending direction of the pressurizing chamber 10 and reaches the other end of the pressurizing chamber 10. While moving little by little in the horizontal direction from there, it proceeds mainly downward and proceeds to the discharge hole 8 opened in the lower surface.

  As shown in FIG. 5, the piezoelectric actuator substrate 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The total thickness of the piezoelectric actuator substrate 21 is about 40 μm. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of pressure chambers 10 (see FIG. 3). These piezoelectric ceramic layers 21a and 21b are made of a potassium sodium niobate (KNN) ceramic material having ferroelectricity. In the piezoelectric ceramic layer 21b, the drive portion 51, which is a portion immediately below the individual electrode main body 35a, has a slightly different composition. This will be described in detail later.

  The piezoelectric actuator substrate 21 has a common electrode 34 made of a metal material such as Ag—Pd and a drive electrode 35 made of a metal material such as Au. The drive electrode 35 is disposed at a position facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21 as described above. One end of the drive electrode 35 is drawn out of a region facing the pressurizing chamber 10 to form a connection electrode 36. The connection electrode 36 is made of, for example, gold containing glass frit, and has a convex shape with a thickness of about 15 μm. The connection electrode 36 is electrically joined to an electrode provided in an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive signal (drive voltage) is supplied to the drive electrode 35 from the control unit 100 through the FPC. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P.

  The common electrode 34 is formed over almost the entire surface in the area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the pressurizing chambers 10 in the region facing the piezoelectric actuator substrate 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the drive electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the drive electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through hole formed in the piezoelectric ceramic layer 21b, and is connected to another electrode on the FPC, like the many drive electrodes 35. ing.

As shown in FIG. 5A, the common electrode 34 and the drive electrode 35 are disposed so as to sandwich only the uppermost piezoelectric ceramic layer 21b. A region sandwiched between the drive electrode 35 and the common electrode 34 in the piezoelectric ceramic layer 21b is called an active portion, and the piezoelectric ceramic in that portion is polarized in the thickness direction. In the piezoelectric actuator substrate 21 of the present embodiment, only the uppermost piezoelectric ceramic layer 21b includes an active portion, and the piezoelectric ceramic 21
a does not include an active part and functions as a diaphragm. The piezoelectric actuator substrate 21 has a so-called unimorph type configuration.

  As will be described later, when a predetermined drive signal is selectively supplied to the drive electrode 35, pressure is applied to the liquid in the pressurizing chamber 10 corresponding to the drive electrode 35. As a result, droplets are discharged from the corresponding discharge holes 8 through the individual flow paths 32. That is, the portion of the piezoelectric actuator substrate 21 that faces each pressure chamber 10 corresponds to the individual displacement element 50 corresponding to each pressure chamber 10 and the discharge hole 8. That is, in the laminate composed of two piezoelectric ceramic layers, the displacement element 50 having a unit structure as shown in FIG. 5 is positioned immediately above the pressurizing chamber 10 for each pressurizing chamber 10. The diaphragm 21a, the common electrode 34, the piezoelectric ceramic layer 21b, and the drive electrode 35 are formed. The piezoelectric actuator substrate 21 includes a plurality of displacement elements 50. In the present embodiment, the amount of liquid discharged from the discharge hole 8 by one discharge operation is about 5 to 7 pL (picoliter).

  The multiple drive electrodes 35 are individually electrically connected to the actuator control means via contacts and wirings on the FPC so that the potentials can be individually controlled.

  An example of a driving method at the time of liquid ejection of the piezoelectric actuator substrate 21 in the present embodiment will be described with respect to a driving voltage (driving signal) supplied to the driving electrode 35. When the drive electrode 35 is set to a potential different from that of the common electrode 34 and an electric field is applied to the piezoelectric ceramic layer 21b in the polarization direction, the portion to which the electric field is applied functions as an active portion that is distorted by the piezoelectric effect. At this time, the piezoelectric ceramic layer 21b expands or contracts in the thickness direction, that is, the stacking direction, and tends to contract or extend in the direction perpendicular to the stacking direction, that is, the plane direction due to the piezoelectric lateral effect. On the other hand, since the remaining piezoelectric ceramic layer 21a is an inactive layer that does not have a region sandwiched between the drive electrode 35 and the common electrode 34, it does not spontaneously deform. That is, the piezoelectric actuator substrate 21 has the piezoelectric ceramic layer 21b on the upper side (that is, the side away from the pressurizing chamber 10) as a layer including the active portion and the lower side (that is, the side close to the pressurizing chamber 10). This piezoceramic layer 21a is a so-called unimorph type structure having an inactive layer.

  In this configuration, when the drive electrode 35 is set to a predetermined positive or negative potential with respect to the common electrode 34 by the actuator controller so that the electric field and the polarization are in the same direction, a portion sandwiched between the electrodes of the piezoelectric ceramic layer 21b. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21a, which is an inactive layer, is not affected by an electric field, so that it does not spontaneously shrink and tries to restrict deformation of the active portion. As a result, there is a difference in strain in the polarization direction between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a, and the piezoelectric ceramic layer 21b is deformed so as to protrude toward the pressurizing chamber 10 (unimorph deformation).

  The driving at the time of liquid ejection (displacement) in this embodiment is called “strike”, and the driving will be described with reference to FIG. FIG. 6A is a partial cross-sectional view of the main part of FIG. 5A, which is an embodiment of the piezoelectric actuator of the present invention configured with fewer elements. Although FIG. 6 is a cross-sectional view, for easy understanding of the drawing, hatching indicating the cross-section is attached to only a part of FIG. This piezoelectric actuator has a diaphragm (piezoelectric ceramic layer 21a) laminated on a fixed member (plate 22) which is a part of the flow path member 4 and has an opening 10 serving as a pressurizing chamber, and a diaphragm. And a pair of electrodes (individual electrode main body 35a and common electrode 34) disposed so as to sandwich the piezoelectric layer (piezoelectric ceramic layer 21b) laminated on the piezoelectric layer and the piezoelectric layer located in the opening 10. ) Is included.

Since the piezoelectric ceramic layers 21a and 21b located on the opening 10 are not fixed to the fixing member (flow path member 4), they can be displaced relatively freely. The piezoelectric ceramic layer 21b located on the opening 10 (that is, overlapped in plan view) includes a driving unit 51 sandwiched between the individual electrode body 35a and the common electrode 34, and the individual electrode body 35a. And a non-driving unit 52 that is not sandwiched between the common electrodes 34 exists.

  The drive unit 51 is a part that undergoes piezoelectric deformation directly by a voltage applied between the common electrode 34 and the drive electrode 35. The non-driving unit 52 is not directly piezoelectrically deformed by voltage, but is deformed by the influence of the piezoelectric deformation of the driving unit 51.

  When no voltage is applied, there is no deformation as shown in FIG. In the strike, first, as shown in FIG. 6C, a standby is performed in a state where a drive voltage is applied in advance. The drive unit 51 contracts in the planar direction of the piezoelectric actuator substrate 21 and becomes shorter than the laminated piezoelectric ceramic layer 21a, so that the displacement element 50 is deformed in a convex manner downward. Next, when the application of voltage is stopped (or a lower voltage is applied), the state of no displacement (or smaller displacement) shown in FIG. 6B is obtained. Thereby, a pressure wave in a direction from the discharge hole 8 toward the pressurizing chamber 10 is generated in the liquid in the flow path. Next, a drive voltage is applied so as to match the timing when the pressure wave is reflected by the aperture 12 and returns toward the ejection hole 8. As a result, the displacement element 50 is again deformed downward to be in the state of FIG. The pressure wave generated by this deformation is combined with the reflected pressure wave, and the liquid droplet is discharged toward the discharge hole 8.

  In the state of FIG. 6C, the displacement element 50 is displaced, so that the piezoelectric ceramic layer 21 b near the boundary between the drive unit 51 and the non-drive unit 52 is in a direction orthogonal to the stacking direction, and the shape of the displacement element 50 A tensile stress as indicated by an arrow in the figure is applied in a direction perpendicular to the outer periphery of the sheet. If the drive waveform as described above is continuously applied, the states of FIG. 6B and FIG. 6C are repeated, and the piezoelectric ceramic layer 21b near the boundary between the drive unit 51 and the non-drive unit 52 repeats. Due to the applied tensile stress, it gradually transforms into a state stretched in the plane direction.

  FIG. 6D shows the displacement element 50 in which the piezoelectric ceramic layer 21b near the boundary between the drive unit 51 and the non-drive unit 52 is deformed and stretched, and is in a state where no voltage is applied. Although the voltage is not applied, the displacement element 50 is deformed downward because it is deformed into an elongated shape. Hereinafter, such deformation may be referred to as residual deformation.

  The initial displacement amount of the piezoelectric actuator is an amount that changes from the state of FIG. 6B to the state of FIG. On the other hand, the displacement amount of the piezoelectric actuator after a very large number of drivings and after the piezoelectric ceramic layer 21b near the boundary between the driving unit 51 and the non-driving unit 52 is deformed and stretched is shown in FIG. The amount changes from the state of (d) to the state of FIG. 6 (c). That is, the amount of displacement after repeated driving becomes smaller than the initial amount. This is drive deterioration. When drive deterioration occurs, when the piezoelectric actuator is used for ejecting droplets, even if the same drive waveform is applied, the droplet ejection speed is reduced or the appropriate amount of liquid is reduced.

  In order to reduce the rate of drive deterioration, the composition of the piezoelectric body is made different between the drive unit 51 and the non-drive unit 52 (more specifically, the portion on the outer periphery of the opening 10 of the non-drive unit 52). Specifically, the basic composition of the piezoelectric ceramic layer 21 b is KNN, and the drive unit 51 contains any of Mn, Cu, and Cr, and the ratio of these elements is determined by the drive unit 51 from the non-drive 52. To be more. The non-driving unit 52 may not include those elements, or may include a smaller amount than the driving unit 51.

Specific composition ratios are as follows. When adding Mn, the ratio of Mn to MnO in terms of potassium sodium niobate in the drive unit 51 is MN1 [parts by mass], and Mn in terms of Mn to potassium sodium niobate in the non-drive unit 52 on the outer periphery of the opening 10 is calculated. When the ratio is MN2 [parts by mass], the range is 2.5 ≦ MN1-MN2 ≦ 25. In the case of adding Cu, the CuO equivalent ratio of Cu with respect to potassium sodium niobate in the drive unit 51 is CU1 [parts by mass], and Cu is CuO equivalent to potassium sodium niobate in the non-drive part 52 on the outer periphery of the opening 10. When the ratio is CU2 [parts by mass], the range is 2.5 ≦ CU1-CU2 ≦ 25. When adding Cr, the Cr ₂ O ₃ equivalent ratio of Cr to potassium sodium niobate in the drive unit 51 is CR1 [parts by mass], and Cr in the non-drive unit 52 on the outer periphery of the opening 10 is Cr with respect to potassium sodium niobate. When the ratio in terms of Cr ₂ O ₃ is CR2 [parts by mass], the range is 1.25 ≦ CR1−CR2 ≦ 15. Here, the composition ratio in the non-driving part 52 was compared with the part on the outer periphery of the opening 10 because the composition ratio of Mn, Cu, Cr in the part close to the driving part 51 inside the non-driving part 52. This is because, as in the case of the drive unit 51, it may be higher. Such an embodiment will be described later.

Here, potassium sodium niobate is represented by a composition formula (K _1-x Na _x ) NbO ₃ and exhibits piezoelectric characteristics. Specifically, in the composition formula, 0.3 ≦ x ≦ 0. It is within the range of 7. Furthermore, lithium sodium potassium niobate containing lithium having the composition formula ((K _1−x Na _x ) _1−y Li _y ) NbO ₃ , 0.3 ≦ x ≦ 0.7, 0.03 ≦ y It may be within the range of ≦ 0.1. The piezoelectric ceramic layer 21b is basically composed of the above-mentioned potassium sodium niobate and oxides of Mn, Cu, and Cr, but may contain other components. The ratio of the total amount of potassium sodium niobate and the oxides of Mn, Cu, and Cr in the piezoelectric ceramic layer 21b is preferably 80% by mass or more, more preferably 90% by mass or more, particularly 95% by mass or more. Is good. Moreover, that potassium sodium niobate is a main component means that the component of the above composition formula is 60% by mass or more, particularly 75% by mass or more of the piezoelectric ceramic layer 21b.

  If the drive unit 51 contains Mn, Cu, and Cr, even if it is repeatedly deformed, residual deformation as shown in FIG. Here, the difference between residual deformation and piezoelectric deformation when a voltage is applied will be described again. Deformation when voltage is applied is almost elastic deformation. Therefore, if the compliance of the piezoelectric ceramic layer 21b is large, the displacement becomes large, and if the compliance is small, the displacement becomes small. When drive deterioration occurs, that is, residual deformation occurs, the deformation when a voltage is applied is almost elastic deformation, but it is considered that the deformation is slightly inelastically deformed. That is, a very small amount of inelastic deformation is caused by one piezoelectric deformation, and the piezoelectric ceramic layer 21b is stretched by that amount. It is considered that this very slight inelastic deformation gradually accumulates and can be observed as residual deformation after piezoelectric deformation as many as 100 million times. Such residual deformation is likely to occur when the piezoelectric ceramic layer 21b is larger than the opening 10, and the present invention is more effective for such a piezoelectric actuator. In particular, when a plurality of piezoelectric actuators are provided side by side and the piezoelectric ceramic layer 21b exists across the plurality of piezoelectric actuators, inelastic deformation is likely to occur due to being pulled from both sides. It is further effective for such a piezoelectric actuator.

  The relationship between the tendency of inelastic deformation and the material properties or material composition is not known in detail. However, in terms of the inelastic deformation, the deformed and distorted lattice differs from the original (quasi-stable) at the crystal lattice level. This is considered to be caused by the deformation to the state and not returning to the original lattice state. Therefore, the ease of occurrence of inelastic deformation is determined by factors different from the compliance indicating the ease of occurrence of elastic deformation, and is considered to exhibit a tendency different from the trend of numerical values of compliance.

By including any of Mn, Cu, and Cr in the drive unit 51, inelastic deformation hardly occurs in the drive unit 51, and drive deterioration can hardly occur. On the other hand, since these elements lower the compliance in the KNN-based composition, the initial displacement amount is reduced due to the lower compliance in the non-driving unit 52. On the other hand, the amount of initial displacement can be increased by reducing the contents of Mn, Cu, and Cr in the non-driving part 52 (outer peripheral part) from the contents in the driving part 51. .

  That is, the initial displacement amount can be increased by setting the difference in the contents of Mn, Cu, and Cr between the driving unit 51 and the non-driving unit 52 to be equal to or greater than the lower limit value of the above range. Further, by setting the difference in the contents of Mn, Cu, and Cr to be equal to or less than the upper limit of the above range, the piezoelectric constant of the drive unit 51 becomes too low, and the displacement amount can hardly be reduced. The non-driving portion 52 (the outer peripheral portion thereof) is preferably one having a smaller ratio of Mn, Cu, and Cr oxides. Specifically, the ratio is preferably 1 part by mass or less of potassium sodium niobate, and more preferably an impurity level.

  In addition, since the influence of the physical properties on the displacement amount and the like of the portion outside the opening 10 of the piezoelectric ceramic layer 21b is relatively lower than that of the driving unit 51 and the non-driving unit 52, Mn, Any content of Cu and Cr may be used. However, since it is considered that the amount of displacement is slightly larger when elastic deformation is likely to occur, the composition is preferably the same as that of the non-driving unit 52 with little or no content of Mn, Cu, and Cr.

  Here, a piezoelectric actuator according to another embodiment of the present invention will be described with reference to FIG. The basic configuration of the piezoelectric actuator of FIG. 7 is the same as that shown in FIG. 5B and FIG. 6A, and the description thereof is omitted by using the same reference numerals for each part.

  In the piezoelectric actuator of FIG. 7, an additive region 53 with a large content of Mn, Cu, and Cr extends around the drive unit 51 to the outside of the drive unit 51. The addition region 53 does not extend over the entire non-driving portion 52, and the portion located on the outer periphery of the opening 10 of the non-driving portion 52 is not added with an additive (or has a small addition amount). It has become. The non-driving part 52 near the boundary between the driving part 51 and the non-driving part 52 causes drive deterioration due to inelastic deformation similarly to the driving part 51, so that it contains Mn, Cu, Cr as in the driving part 51. It is preferable to increase the amount. On the other hand, since the compliance of the portion becomes high, the initial displacement is slightly reduced, but the drive deterioration can be further reduced.

  When the ratio of the added region 53 in the non-driving unit 52 increases, the initial displacement amount also decreases. Therefore, the ratio is preferably 20% or more and 55% or less. The contents of Mn, Cu, and Cr in the addition region 53 may be set in the same range as the content in the drive unit 51.

  The piezoelectric actuator as described above is manufactured as follows, for example. A tape composed of a piezoelectric ceramic powder and an organic composition is formed by a general tape forming method such as a roll coater method or a slit coater method, and a plurality of green sheets that become piezoelectric ceramic layers 21a and 21b after firing are produced. . An electrode paste to be the common electrode 34 is formed on a part of the green sheet by printing or the like.

  Then, each green sheet is laminated | stacked, a laminated body is produced, it bakes, and a piezoelectric actuator element | base_body is produced. Thereafter, a paste containing oxides of Mn, Cu, and Cr is printed at the position of the addition region 53. The amount of printing is adjusted so that the added amount of Mn, Cu, and Cr in the piezoelectric ceramic layer 21b is within a predetermined range after Mn, Cu, and Cr are diffused in the piezoelectric ceramic layer 21b immediately below the added region 53. . By printing and firing, Mn, Cu, and Cr diffuse into the piezoelectric ceramic layer 21b.

  Subsequently, the individual electrode 35 was printed on the surface of the piezoelectric actuator element body using Ag paste, and then fired to produce the piezoelectric actuator substrate 21. Instead of printing and baking oxide pastes of Mn, Cu, and Cr, oxides of Mn, Cu, and Cr are added to the Ag paste that becomes the individual electrode 35, and these elements are transferred from the Ag paste to the piezoelectric ceramic layer 21b. It may be diffused.

  Furthermore, a piezoelectric actuator can be manufactured by bonding and laminating a metal plate 22 having an opening 10 as a fixing member and a piezoelectric actuator substrate 21.

  First, a piezoelectric actuator for evaluation was produced. The basic structure of the piezoelectric actuator for evaluation is the same as that shown in FIGS. 2 to 5, but the pressurizing chamber 10 is open to the plate 31 and cannot discharge liquid. The displacement of the displacement element 50 can be measured from the side by a laser Doppler displacement meter.

The piezoelectric material used piezoelectric ceramic layers 21a, and 21b, as will become a composition formula as _{(K 0.47 Na 0.47 Li 0.06)} NbO 3, Na 2 CO 3, K 2 CO 3, Li 2 CO 3 , Nb ₂ O ₅ powders were prepared. The prepared raw materials were mixed in a pot together with water or isopropanol and zirconia balls. The mixed raw material was once dried and then calcined at 900 ° C. The calcined raw material was crushed by putting it in a pot together with water or isopropanol and zirconia balls. A slurry was prepared using the powder, and a green sheet was prepared from the slurry by employing a roll coater method as a forming method.

  Next, an electrode pattern to be the common electrode 34 was formed on the surface of the green sheet by a screen printing method using a conductive paste containing an Ag—Pd alloy. Next, green sheets that were not printed were laminated on the green sheets and then fired at a temperature of 1050 ° C. to obtain a piezoelectric actuator element body. The thickness of the piezoelectric ceramic layers 21a and 21b of the obtained piezoelectric actuator body was about 20 μm per layer.

For the sample in which any of Mn, Cu, and Cr was added to the piezoelectric ceramic layer 21b, a paste containing MnO, CuO, and Cr ₂ O ₃ powder was printed in a predetermined pattern. Moreover, the addition amount with respect to the piezoelectric ceramic layer 21b was changed by producing the sample which changed printing amount (printing thickness). After printing, firing was performed at 1000 ° C. to diffuse these elements into the piezoelectric ceramic layer 21b. It is considered that the printed pattern was not visible after firing, and the entire amount was diffused into the piezoelectric ceramic layer 21b.

  Next, a conductor paste containing Au to be the individual electrodes 35 was printed on the surface of the piezoelectric actuator element body in a matrix pattern by screen printing. In addition, about the sample which diffused Mn, Cu, and Cr, the conductor paste was printed in the same position as the position where those oxide pastes were printed. The printed piezoelectric actuator body was baked at 700 ° C., and the individual electrodes 35 were baked to produce the piezoelectric actuator substrate 21.

  Next, the position of the individual electrode 35 was aligned and laminated to the opening 10 of the flow path member 4 (fixing member) produced by bonding and laminating metallic plates. Thereafter, a direct-current voltage was applied between the individual electrode 35 and the common electrode 35 to polarize the piezoelectric ceramic layer 21b of the drive unit 51, thereby producing a piezoelectric actuator.

For each sample, after measuring the initial amount of displacement, a pulse waveform of 2 kHz was added to cause drive deterioration, and the amount of displacement was measured after driving for a predetermined cycle. In addition, it is thought that drive deterioration has arisen by the cycle number of about 1/10 with respect to the drive waveform of about 20-40 kHz used for printing by setting the frequency to 2 kHz. The obtained results are shown in Table 1. The deterioration rate is a ratio of the displacement amount after 10 billion cycles to the initial displacement amount.

  Details of the contents of the table are as follows. The “addition amount of the driving portion” and “addition amount of the non-driving portion (on the outer periphery)” are the potassium sodium niobate when the total amount of each printed oxide diffuses into the piezoelectric ceramic layer 21b immediately below the printed pattern. It is a ratio with respect to 100 parts by mass of the (lithium) component. Actually, since the concentration on the individual electrode 35 side is considered to be high, the value shown here is an average value thereof.

  The “(additive) added region area” is an area of a region (added region 53) in which each oxide is added and its concentration is increased. This area is an area with a boundary where the concentration of each oxide content is halved on the surface of the piezoelectric actuator substrate 21.

The “area ratio of the additive region in the non-driving part” is a ratio of the area of the additive region 53 existing in the non-driving part 52. It can be calculated by (area of added region 53−area of driving unit 51) / area of non-driving unit 52. The area of the drive unit 51 is 0.104 mm ² , and the area of the non-drive unit 52 is 0.056 mm ² .

Sample No. which is a piezoelectric actuator within the scope of the present invention. 3 to 11, 13 to 18, and 20 to 25 are piezoelectric actuators outside the scope of the present invention, sample Nos. To which no oxide was added. 1 and sample N in which each oxide is added to the driving unit 51 and the non-driving unit 52 in the same ratio
o. The deterioration rate was small with respect to 2, 12, and 19, and the driving deterioration was difficult.

  Further, Sample No. in which the difference in Mn content (MN1-MN2) is 2.5 parts by mass or more and 20 parts by mass or less. In samples 3-6 and 8-12, sample no. The initial displacement amount was larger than 1. Sample No. in which the difference in Cu content (CU1-CU2) is 2.5 parts by mass or more and 20 parts by mass or less. In samples 14, 15, 17 and 18, sample no. The initial displacement amount was larger than 1. Sample No. whose Cr content difference (CR1-CR2) is 2.5 parts by mass or more and 10 parts by mass or less. 21, 24 and 25, sample no. The initial displacement amount was larger than 1.

  Further, when comparing Sample Nos. 5 and 8 to 11 in which the difference in Mn content (MN1 to MN2) is 10 parts by mass, the sample No. In Nos. 5, 9, and 10, sample Nos. With an area ratio of 0% Drive deterioration is less likely than in 8. Also in the sample to which Cu and Cr were added, the sample within the range of the area ratio described above was less likely to be driven and deteriorated than the sample having the area ratio of 0%.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Channel member (fixing member)
DESCRIPTION OF SYMBOLS 5 ... Manifold 5a ... Sub manifold 5b ... Opening 6 ... Individual supply flow path 8 ... Discharge hole 9 ... Pressurizing chamber group 10 ... Pressurizing chamber (opening part)
11a, b, c, d ... pressurization chamber row 12 ... squeezing 15a, b, c, d ... discharge hole row 21 ... piezoelectric actuator substrate 21a ... piezoelectric ceramic layer (vibrating plate)
21b ... Piezoelectric ceramic layer 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Drive electrode 36 ... Connection electrode 50 ... Displacement element 51 ... Drive Part 52... Non-driving part 53... (Additive) added region 54... (Additive) non-added region

Claims (6)

A fixing member having an opening;
A diaphragm laminated on the fixing member so as to cover the opening;
A piezoelectric layer laminated on the diaphragm so as to cover the opening;
A pair of electrodes disposed so as to sandwich the piezoelectric layer located on the opening,
When viewed in plan,
In the portion of the piezoelectric layer that overlaps with the opening, there is a drive unit that is sandwiched between the pair of electrodes and a non-drive unit that is not sandwiched between the pair of electrodes,
The non-driving part is disposed along the outer periphery of the opening,
The piezoelectric layer is mainly composed of potassium sodium niobate, and at least the driving unit contains Mn.
The ratio of Mn converted to MnO with respect to 100 parts by mass of the main component in the driving unit is MN1 [parts by mass], and the ratio of Mn to MnO with respect to 100 parts by mass of the main component in the non-driving unit on the outer periphery of the opening. A piezoelectric actuator characterized by satisfying 2.5 ≦ MN1-MN2 ≦ 25 when MN2 [part by mass]. A fixing member having an opening;
A diaphragm laminated on the fixing member so as to cover the opening;
A piezoelectric layer laminated on the diaphragm so as to cover the opening;
A pair of electrodes disposed so as to sandwich the piezoelectric layer located on the opening,
When viewed in plan,
In the portion of the piezoelectric layer that overlaps with the opening, there is a drive unit that is sandwiched between the pair of electrodes and a non-drive unit that is not sandwiched between the pair of electrodes,
The non-driving part is disposed along the outer periphery of the opening,
The piezoelectric layer is mainly composed of potassium sodium niobate, and at least the driving unit includes Cu.
The ratio of Cu to CuO equivalent to 100 parts by mass of the main component in the driving part is CU1 [parts by mass], and the ratio of Cu to CuO equivalent to 100 parts by mass of the main ingredient in the non-driving part on the outer periphery of the opening. A piezoelectric actuator characterized by satisfying 2.5 ≦ CU1-CU2 ≦ 25 when CU2 [parts by mass]. A fixing member having an opening;
A diaphragm laminated on the fixing member so as to cover the opening;
A piezoelectric layer laminated on the diaphragm so as to cover the opening;
A pair of electrodes disposed so as to sandwich the piezoelectric layer located on the opening,
When viewed in plan,
In the portion of the piezoelectric layer that overlaps with the opening, there is a drive unit that is sandwiched between the pair of electrodes and a non-drive unit that is not sandwiched between the pair of electrodes,
The non-driving part is disposed along the outer periphery of the opening,
The piezoelectric layer is mainly composed of potassium sodium niobate, and at least the driving portion includes Cr.
The ratio of Cr in terms of Cr ₂ O _{3 with} respect to 100 parts by mass of the main component in the drive unit is CR1 [parts by mass], and Cr ₂ of Cr with respect to 100 parts by mass of the main component in the non-drive unit on the outer periphery of the opening. A piezoelectric actuator characterized by satisfying 1.25 ≦ CR1−CR2 ≦ 15 when the ratio in terms of O ₃ is CR2 [parts by mass].   When viewed in a plan view, a region of the non-driving portion that surrounds the driving portion and that is 20% to 55% of the area of the non-driving portion has the same composition as the driving portion. The piezoelectric actuator according to claim 1.   5. A liquid discharge head comprising a plurality of piezoelectric actuators according to claim 1, comprising a plurality of discharge holes respectively connected to the plurality of openings. 6. 6. A recording apparatus comprising: the liquid discharge head according to claim 5; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the plurality of piezoelectric actuators.

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