JP5665478B2 - Liquid discharge head and recording apparatus using the same - Google Patents

Description

  The present invention relates to a liquid discharge head that discharges droplets and a recording apparatus using the same.

  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 liquid discharge holes for discharging the droplets formed in the liquid discharge head must be increased. There is a need to.

  Accordingly, the liquid discharge head is connected to the manifold and the flow path member having the liquid discharge holes connecting the manifold via the plurality of liquid pressurization chambers, and the plurality of individual electrodes provided so as to cover the liquid pressurization chambers, respectively. And a piezoelectric actuator unit having a plurality of displacement elements including a common electrode facing a plurality of individual electrodes and a piezoelectric ceramic layer sandwiched between them are known (for example, (See Patent Document 1). In this liquid ejection head, the liquid pressurizing chambers connected to the plurality of liquid ejection holes are arranged in a matrix, and the displacement element of the actuator unit provided so as to cover it is displaced by deformation of the piezoelectric body, Ink is ejected from each liquid ejection hole, and printing is possible at a resolution of 600 dpi in the main scanning direction.

JP 2003-305852 A

However, when the displacement element is driven in the liquid ejection head described in Patent Document 1 to drive the liquid, stress is applied to the piezoelectric body around the displacement element, and when ejection is repeated, the piezoelectric body around the displacement element The shape will be different from the initial shape, and as a result,
There has been a problem in that a driving deterioration is caused when a pressure different from the initial state is applied to the displacement element to reduce the displacement.

  Accordingly, it is an object of the present invention to provide a liquid discharge head and a recording apparatus that are unlikely to cause drive deterioration.

The liquid discharge head of the present invention covers the plurality of liquid pressurization chambers on the flow path member having the plurality of liquid pressurization chambers and the plurality of liquid discharge holes respectively connected to the plurality of liquid pressurization chambers. The piezoelectric actuator unit is a liquid discharge head in which the piezoelectric actuator unit is laminated in the order of a diaphragm, a common electrode, a piezoelectric body, and a plurality of individual electrodes from the flow path member side. When viewed, the plurality of individual electrodes are arranged so as to overlap with the plurality of liquid pressurizing chambers, respectively, and the individual electrodes and the common electrodes are located in the center of the plurality of liquid pressurizing chambers. The central region of the piezoelectric body sandwiched between the electrodes is polarized in the stacking direction, and the peripheral region around the central region of the piezoelectric body sandwiched between the individual electrodes and the common electrode is Is polarized in the central area and the opposite direction, the individual electrodes, and the individual electrode body is led from the individual by the electrode body, it includes a lead electrode that is external wiring electrically connected, the lead A central region located in the center of the piezoelectric body sandwiched between the electrode and the common electrode is polarized in the same direction as the central region of the piezoelectric body sandwiched between the individual electrode and the common electrode And the area around the piezoelectric body sandwiched between the extraction electrode and the common electrode is the same direction as the surrounding area of the piezoelectric body sandwiched between the individual electrode and the common electrode It is characterized by being polarized .

In plan view, the area of the central region of the piezoelectric body sandwiched between the individual electrodes and the common electrode is preferably 0.45 to 1 times the area of the liquid pressurizing chamber.

When viewed in plan, the central region of the piezoelectric body sandwiched between the individual electrode and the common electrode and the peripheral region of the piezoelectric body sandwiched between the individual electrode and the common electrode are combined. The region preferably has a shape that is substantially similar to the shape of the liquid pressurizing chamber and an area that is not more than 1.44 times the area of the liquid pressurizing chamber.

  The recording apparatus of the 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 liquid discharge head and the transport unit. It is characterized by.

  According to the liquid discharge head of the present invention, when viewed in plan, the stress at the time of displacement of the piezoelectric body positioned around the liquid pressurizing chamber is reduced, so that drive deterioration is unlikely to occur in the liquid discharge head.

  Further, according to the recording apparatus of the present invention, the initial recording accuracy can be maintained even when used for a long time.

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. 2. 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 the principal part of the longitudinal cross-section of the direction orthogonal to (a). (A) and (b) are the top views which showed the shape of the separate electrode which concerns on one embodiment of this invention. (A) (b) (c) is the top view which showed the shape of the separate electrode which concerns on one embodiment of this invention. (A)-(e) is a schematic diagram explaining a drive deterioration. (A)-(e) is a figure which shows the preparation methods of the liquid discharge head which concerns on one embodiment of this invention.

  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, there are a nip roller 138 and a nip receiving roller 139.
It arrange | positions so that the conveyance belt 111 may be pinched | interposed. 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 liquid discharge head main body 13 at the lower end. A large number of liquid ejection holes 8 for ejecting liquid are provided on the lower surface of the liquid ejection head body 13 (see FIG. 3).

  Liquid droplets (ink) of the same color are ejected from the liquid ejection holes 8 provided in one liquid ejection head 2. Since the liquid 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), Printing can be performed without gaps in one 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 discharge head 2 is arranged with a slight gap between the lower surface of the liquid discharge head main 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 liquid ejection head 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 liquid discharge head main body 13 constituting the liquid discharge head of the present invention will be described. FIG. 2 is a top view showing the liquid discharge head main body 13 shown in FIG. FIG. 3 is an enlarged top view of a region surrounded by the alternate long and short dash line in FIG. 2 and is a part of the liquid discharge head main body 13. FIG. 4 is an enlarged perspective view of the same position as in FIG. 3, in which some of the flow paths are omitted so that the position of the liquid discharge holes 8 can be easily understood. 3 and 4, in order to make the drawings easy to understand, the liquid pressurizing chamber 10 (liquid pressurizing chamber group 9), the squeezing 12, and the liquid discharge holes which are to be drawn by broken lines below the piezoelectric actuator unit 21. 8 is drawn with a solid line. 5A is a longitudinal sectional view taken along the line VV in FIG. 3, and FIG. 5B is a partial longitudinal sectional view in a direction orthogonal to FIG. 5A, and an enlarged main part. FIG. FIG. 6A is an enlarged plan view of the individual electrode 35 of the liquid discharge head body 13 shown in FIG.

  The liquid discharge head body 13 has a flat plate-like flow path member 4 and a piezoelectric actuator unit 21 that is an actuator unit on the flow path member 4. The piezoelectric actuator unit 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. Further, two piezoelectric actuator units 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator units 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 unit 21, the droplets ejected by the two piezoelectric actuator units 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 units 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 unit 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In a region sandwiched between two piezoelectric actuator units 21, one manifold 5 is shared by adjacent piezoelectric actuator units 21, and the sub-manifold 5 a branches off from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the liquid discharge head main body 13 adjacent to each other in regions facing the piezoelectric actuator units 21 inside the flow path member 4.

  The flow path member 4 has four liquid pressurizing chamber groups 9 in which a plurality of liquid pressurizing chambers 10 are formed in a matrix (that is, two-dimensionally and regularly). The liquid pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The liquid pressurizing chamber 10 is formed so as to open on the upper surface of the flow path member 4. These liquid pressurizing chambers 10 are arranged over almost the entire surface of the upper surface of the flow path member 4 facing the piezoelectric actuator unit 21. Accordingly, each liquid pressurizing chamber group 9 formed by these liquid pressurizing chambers 10 occupies a region having almost the same size and shape as the piezoelectric actuator unit 21. Further, the opening of each liquid pressurizing chamber 10 is closed by adhering the piezoelectric actuator unit 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 liquid pressurizing chambers 10 connected to 5a constitute a row of liquid 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 short direction. Yes. Two rows of liquid pressurizing chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

  As a whole, the liquid pressurizing chambers 10 connected from the manifold 5 constitute rows of the liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are 16 rows parallel to each other in the short direction. It is arranged. The number of liquid pressurizing chambers 10 included in each liquid 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. ing. The liquid 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 the individual flow paths 32 connected to the sub-manifolds 5a are not necessarily connected at equal intervals when the liquid ejection holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a. This means that 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 extending direction of 5a, that is, the main scanning direction.

  Individual electrodes 35 to be described later are formed at positions facing the liquid pressurizing chambers 10 on the upper surface of the piezoelectric actuator unit 21. The individual electrode 35 is slightly smaller than the liquid pressurizing chamber 10, has a shape substantially similar to the liquid pressurizing chamber 10, and fits in a region facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. Is arranged.

  A large number of liquid ejection holes 8 are formed on the lower surface of the flow path member 4. These liquid discharge holes 8 are arranged at a position avoiding a region facing the sub-manifold 5 a arranged on the lower surface side of the flow path member 4. Further, these liquid discharge holes 8 are arranged in a region facing the piezoelectric actuator unit 21 on the lower surface side of the flow path member 4. These liquid discharge hole groups 7 occupy an area having almost the same size and shape as the piezoelectric actuator unit 21, and the liquid discharge holes 8 are made to drop liquid by displacing the displacement element 50 of the corresponding piezoelectric actuator unit 21. Can be discharged. The arrangement of the liquid discharge holes 8 will be described in detail later. The liquid 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 liquid discharge 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. 5, the liquid discharge head main body 13 has a liquid pressurizing chamber 10 on the upper surface of the flow path member 4, the sub manifold 5 a on the inner lower surface side, and the liquid discharge holes 8 on the lower surface. Each part constituting the individual flow path 32 is disposed close to each other at different positions, and the sub-manifold 5 a and the liquid discharge hole 8 are connected via the liquid pressurizing chamber 10.

  The holes formed in each plate will be described. These holes include the following. First, the liquid pressurizing chamber 10 formed in the cavity plate 22. Second, there is a communication hole that forms a flow path that connects from one end of the liquid 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 liquid 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 that constitutes a flow channel that communicates from the other end of the liquid pressurizing chamber 10 to the liquid discharge hole 8, and this communication hole is referred to as a descender (partial flow channel) in the following description. . The descender is formed on each plate from the base plate 23 (specifically, the outlet of the liquid pressurizing chamber 10) to the nozzle plate 31 (specifically, the liquid 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 from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the liquid discharge hole 8. The liquid supplied to the sub manifold 5a is discharged from the liquid 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 liquid pressurizing chamber 10 upward. Further, the liquid pressurizing chamber 10 proceeds horizontally along the extending direction of the liquid pressurizing chamber 10 and reaches the other end of the liquid pressurizing chamber 10. While moving little by little in the horizontal direction from there, it proceeds mainly downward and proceeds to the liquid discharge hole 8 opened on the lower surface.

  As shown in FIG. 5, the piezoelectric actuator unit 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 unit 21 is about 40 μm, and the displacement amount can be increased by being 100 μm or less. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of liquid pressurizing chambers 10 (see FIG. 3). The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  The piezoelectric actuator unit 21 includes a common electrode 34 made of a metal material such as Ag—Pd and an individual electrode 35 made of a metal material such as Au. As described above, the individual electrode 35 is disposed at a position facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. One end of the individual electrode 35 is drawn out of a region facing the liquid pressurizing chamber 10 to be a lead electrode 35b, and a connection electrode 36 is formed on the lead electrode 35b. 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 from the control unit 100 to the individual electrode 35 through an FPC (Flexible Printed Circuit) that is the external wiring 60. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P. The connection with the external wiring 60 is performed as follows, for example. A bump 46 is further formed on the connection electrode 36 on the individual electrode 35, and the bump 46 breaks through the cover film 60c of the external wiring 60 and comes into contact with the wiring 60b to be electrically connected and sandwiched by the cover film 60c. It is held by being.

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 liquid pressurizing chambers 10 in the region facing the piezoelectric actuator unit 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 individual electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the individual 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, like the large number of individual electrodes 35, is connected to another electrode in the external wiring 60. It is connected.

  As will be described later, when a predetermined drive signal is selectively supplied to the individual electrode 35, pressure is applied to the liquid in the liquid pressurizing chamber 10 corresponding to the individual electrode 35. As a result, droplets are discharged from the corresponding liquid discharge ports 8 through the individual flow paths 32. That is, the portion of the piezoelectric actuator unit 21 that faces each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator) corresponding to each liquid pressurizing chamber 10 and the liquid discharge port 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 provided immediately above the liquid pressurizing chamber 10 for each liquid pressurizing chamber 10. Are formed by a diaphragm 21a, a common electrode 34, a piezoelectric ceramic layer 21b, and individual electrodes 35, and the piezoelectric actuator unit 21 includes a plurality of displacement elements 50. In the present embodiment, the amount of liquid ejected from the liquid ejection port 8 by one ejection operation is about 5 to 7 pL (picoliter).

  When viewed in a plan view, the individual electrode 35 is disposed so as to overlap the liquid pressurizing chamber 10, and is sandwiched between the individual electrode 35 and the common electrode 24, which is located at the center of the liquid pressurizing chamber 10. The piezoelectric ceramic layer 21 b is a central region 55 that is polarized in the stacking direction of the piezoelectric actuator units 21. The direction of polarization may be either upward or downward, and driving can be performed by giving a drive signal corresponding to the direction. A peripheral region 56 around the central region 55 of the piezoelectric ceramic layer 21b sandwiched between the separate electrode 35 and the common electrode 24 is polarized in a direction opposite to that of the central region 55. The outer side of the surrounding region 55 may or may not be polarized. Although details will be described later, with such a configuration, when driving, an area above the portion of the piezoelectric ceramic layer 21b joined to the flow path member 4 outside the liquid pressurizing chamber 10 (described later). Since the tensile stress applied to the restraining portion 952) can be reduced, drive deterioration hardly occurs.

  The individual electrode 35 is overlapped with the liquid pressurizing chamber 10, or is composed of an individual electrode 35a substantially similar to the liquid pressurizing chamber 10 and a lead electrode 35b drawn from the individual electrode main body 35a. Here, “substantially similar” means that the curvature of the corner is slightly changed from the similar shape, and means that the deviation of the outer shape from the similar shape is within about 10% of the size, which is the explanation of the present invention. The same applies to the other parts. The surrounding region 56 may extend to the outside of the liquid pressurizing chamber 10 or may be accommodated inside the liquid pressurizing chamber 10. FIG. 5B is an example in which the surrounding area 256 is accommodated inside the liquid pressurizing chamber 10, which is preferable in that the distance between the surrounding area 256 and the adjacent displacement element can be increased. Moreover, the center area | region 55 and the surrounding area | region 56 do not need to touch, and the area | region which is not polarized may be pinched | interposed between them. The piezoelectric ceramic layer 21b outside the peripheral region 56 may be polarized or not polarized. In the manufacturing method described later, it is preferable to polarize portions other than the central region 55 of the piezoelectric ceramic layer 21b in the same direction as the surrounding region 56, because the influence of the displacement of the surrounding region 56 is reduced.

One of the actual driving procedures in the present embodiment is called striking, and the individual electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as a high potential) in advance, and the individual electrode 35 is provided every time there is a discharge request. Is once set to the same potential as the common electrode 34 (hereinafter referred to as a low potential), and then set to a high potential again at a predetermined timing. As a result, the piezoelectric ceramic layers 21a and 21b return to the original shape at the timing when the individual electrode 35 becomes low potential, and the volume of the liquid pressurizing chamber 10 is compared with the initial state (the state where the potentials of both electrodes are different). To increase. At this time, a negative pressure is applied to the liquid pressurizing chamber 10 and the liquid is sucked into the liquid pressurizing chamber 10 from the manifold 5 side. Thereafter, at the timing when the individual electrode 35 is set to a high potential again, the piezoelectric ceramic layers 21a and 21b are deformed so as to protrude toward the liquid pressurizing chamber 10, and the volume of the liquid pressurizing chamber 10 is reduced so that the inside of the liquid pressurizing chamber 10 Becomes a positive pressure, the pressure on the liquid rises, and droplets are ejected. In other words, in order to eject droplets,
A drive signal including a pulse based on a high potential is supplied to the individual electrode 35. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the end 5 on the liquid pressurizing chamber 10 side of the squeezing 12 to the liquid discharge hole 8 in the individual flow path 32. According to this, when the inside of the liquid pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplet can be ejected with a stronger pressure.

  On the contrary, a driving method called pushing can be used. In the pushing, the individual electrode 35 is set to the same potential (low potential) as the common electrode 34, and the individual electrode 35 is set to a higher potential (high potential) than the common electrode 34 every time there is a discharge request. Thereby, the liquid column pushed out from the liquid discharge hole 8 due to the increase in the volume of the liquid pressurizing chamber 10 causes the liquid pressurization when the inside of the liquid pressurizing chamber 10 is reversed from the positive pressure state to the negative pressure state. The volume of the chamber 10 is increased, the root of the liquid column is cut, and the separated droplets are discharged.

  In gradation printing, gradation expression is performed by the number of droplets ejected continuously from the liquid ejection holes 8, that is, the droplet amount (volume) adjusted by the number of droplet ejections. For this reason, the number of droplet discharges corresponding to the specified gradation expression is continuously performed from the liquid discharge hole 8 corresponding to the specified dot region. In general, when liquid ejection is performed continuously, it is preferable that the interval between pulses supplied to eject liquid droplets is AL. As a result, the period of the residual pressure wave of the pressure generated when discharging the previously discharged liquid droplet coincides with the pressure wave of the pressure generated when discharging the liquid droplet discharged later, and these are superimposed. Thus, the pressure for discharging the droplet can be amplified.

  The reason why the drive deterioration occurs in the basic operation as described above will be described with reference to FIGS. FIG. 8A is a longitudinal section of the piezoelectric ceramic layer 921b, the common electrode 934, the individual electrode 935, and the auxiliary electrode 41 in a state where no voltage is applied, of the displacement element 950. In this displacement element 950, the piezoelectric ceramic layer 921b sandwiched between the individual electrode 935 and the common electrode 934 is polarized in the stacking direction, but there is no portion polarized in the direction opposite to this polarization. It is out of the range. A portion of the piezoelectric ceramic layer 921b sandwiched between the common electrode 934 and the individual electrode 935 is referred to as a drive unit 951, and a piezoelectric ceramic layer 921b located above the portion joined to the plate 922 is referred to as a restraint unit 952.

  Even in a liquid ejection element using such a displacement element 950, ejection can be performed by the above-described general stroke. As shown in FIG. 8B, the stand-by is performed in a state where a voltage is applied to the individual electrode 935 (hereinafter, the state before discharge is referred to as a stand-by state), and as shown in FIG. (Hereinafter, a state in which a driving voltage different from the standby state is applied is referred to as a driving state), and then a series of operations of returning to the standby state in FIG. Is discharged. In the standby state of FIG. 8B, the drive unit 951 is contracted in the planar direction, and a tensile stress is applied to the restraint unit 952. Since this stress is repeatedly applied for a very long time, strong elastic domain switching occurs in the constraining portion 952, and it gradually extends to a plane. FIG. 8D shows the displacement element 950 in a state where the restraining portion 952 is deformed and stretched, and is in a state where no voltage is applied. Although the voltage is not applied, the restraint portion 952 is deformed and extended, so that the displacement element 950 is deformed downward. In such a state, even when no voltage is applied, the displacement as shown in FIG. 8B does not become zero, and the amount of displacement when a drive signal is given becomes small. As a result, even when the same drive signal is applied, the ejection speed of the droplets is slowed down or the appropriate amount of liquid is reduced. This is drive deterioration.

In the displacement element 50, as shown in FIG. 8E, when a voltage is applied to the individual electrode 35, the central region 55 contracts and the surrounding region 56 expands. Thereby, the restraining part above the part joined to the plate 22 is not easily stretched. In other words, if the restraining portion is the surrounding region 55, the surrounding region 55 is stretched itself by application of a voltage, and thus is not easily stretched even if a tensile stress is applied. If the restraining portion is an area further outside the surrounding area 55, the surrounding area 55 is extended, and hence the tensile stress is reduced accordingly, so that it is difficult to be extended. Further, when the surrounding area 56 extends to the outside of the liquid pressurizing chamber 10, even if the outside of the surrounding area 56 is extended, the position of the portion is separated from the liquid pressurizing chamber 10. The degree of drive deterioration that occurs as shown in FIG. 8D can be further reduced.

The central region 55 is disposed at a position having the center of area C of the liquid pressurizing chamber 10 as a substantially similar center, so that the displacement can be increased. Further, the region including the central region 55 and the surrounding region 56 is also disposed at a position having the area center of gravity C of the liquid pressurizing chamber 10 as a substantially similar center, so that the displacement can be increased. Assuming that the area of the central region 55 in a plan view is So [mm ² ] and the area of the liquid pressurizing chamber 10 is Sc [mm ² ], the displacement element 50 is obtained when So is 0.45 times or more of Sc. The displacement of can be increased. That is, when a voltage is applied to the individual electrode 35 so that the central region 55 contracts in the plane direction at the center of the liquid pressurizing chamber 10, the displacement element 50 is displaced toward the liquid pressurizing chamber 10, and the surrounding region 56 is Since it expands with the voltage and pushes the center part of the displacement element 50 toward the liquid pressurizing chamber 10, the displacement of the displacement element 50 becomes larger. Since So is 0.45 times or more of Sc, even if the area of the surrounding region 56 becomes large, the displacement can be made larger than when the surrounding region 56 does not exist. Further, even if So is larger than 1 time of Sc, the displacement is not improved and crosstalk is increased. Therefore, it is preferable that So is 1 time or less of Sc.

  When viewed in plan, the region including the central region 55 and the peripheral region 56 is substantially similar in shape to the shape of the liquid pressurizing chamber 10, and the area So of the central region 55 and the area Si of the peripheral region 56 are liquid. By being 1.44 times or less the area Sc of the pressurizing chamber 10, it is possible to reduce crosstalk generated between adjacent liquid ejection elements. That is, when a voltage is applied to the displacement element 50 in order to eject a droplet from one liquid ejection element, the piezoelectric deformation of the displacement element 50 that occurs at that time is transmitted to the adjacent displacement element 50, and is caused by the displacement element 50. Variations in the ejection characteristics of the liquid ejection elements that are ejected can be reduced. This is because even if the area of So + Si is 1.44 times or more of Sc, the displacement of the displacement element 50 is not improved, and the distance between the displacement elements 50 can be increased so that piezoelectric deformation is not transmitted.

  When the displacement state of the displacement element 950 shown in FIGS. 8A to 8D was analyzed by simulation, the following was found. When the outside of the driving unit 951 is located at a position overlapping the liquid pressurizing chamber, when displaced, the portion locally protrudes on the opposite side of the liquid pressurizing chamber as shown in FIG. . In the displacement element 950, the portion joined to the flow path member or the piezoelectric actuator unit close to the portion is in a state where it is difficult to be deformed upward, but in the displacement element 50, the surrounding region 56 is piezoelectrically deformed, When the region 56 is directly above the liquid pressurizing chamber 10, the upward convex deformation can be reduced, and the bending deformation can be increased toward the liquid pressurizing chamber. Even when the surrounding region 56 is outside the liquid pressurizing chamber 10, the peripheral region 56 extends and acts to push the central region 55 toward the center of the liquid pressurizing chamber 10. The same effect as when convexly deforming upward can be produced.

At this time, when the flow path member is made of stainless steel, the Young's modulus is about 200 GPa and the thickness is 1 to 3 mm. When the piezoelectric ceramic is made of lead zirconate titanate, the Young's modulus is about 80 GPa and the thickness is 20 to 100 μm. For this reason, the flow path member hardly deforms, and deformation almost occurs in the piezoelectric ceramic. Providing a peripheral region direction 56 polarized in the opposite direction to the central region 55 around the central region 55 suppresses upward convex deformation in bending deformation, or extends in the plane direction, thereby increasing the amount of displacement. be able to. Even if the piezoelectric properties, Young's modulus and thickness of the piezoelectric ceramic, and Young's modulus and thickness of the diaphragm change, these physical properties are almost constant in the plane direction. Since the displacement caused by the deformation and the displacement caused by the contribution of piezoelectric deformation in the outer region are in a proportional relationship, it is considered that the region where the displacement increasing effect is generated does not change. For example, when the piezoelectric characteristics are large, when the area of So + Si is larger than 1.44 times Sc, the amount of piezoelectric deformation in the outer portion of the area of 1.44 times becomes large, and the displacement element due to the contribution of the piezoelectric deformation However, if the piezoelectric characteristics are large, the displacement of the displacement element is also large. Therefore, the rate of increase in the displacement is small, and an effect larger than 1.44 times cannot be obtained. it is conceivable that. Note that 1.44 is a value obtained by an experiment described later.

  7A to 7C show the structure of individual electrodes of a liquid discharge head according to another embodiment of the present invention. Since the basic structure of these liquid discharge heads is the same as that of the liquid discharge head 2 described above, a description thereof will be omitted, and differences in the structure of the individual electrodes will be described.

  7A and 7B, when viewed in plan, the individual electrodes 335 and 435 are drawn out from the individual electrode main bodies 335a and 435a and the individual electrode main bodies 335a and 435a, and are electrically connected to the external wiring. The lead electrodes 335b and 435b are connected. The connection electrodes 336 and 436 are formed on the extraction electrodes 335b and 435b and are electrically connected to external wiring.

  In FIG. 7A, the individual electrode 335 includes an individual electrode body 335 a that overlaps the liquid pressurizing chamber 310 and an extraction electrode 335 b that is led out of the liquid pressurizing chamber 310. Since the individual electrode main body 335a is accommodated in the liquid pressurizing chamber 310, crosstalk between adjacent liquid ejection elements can be reduced. The central region 357 of the piezoelectric ceramic layer 321b sandwiched between the extraction electrode 335b and the common electrode is polarized in the stacking direction, and this direction is the piezoelectric ceramic layer 321b sandwiched between the individual electrode body 335a and the common electrode. The central region 355 has the same polarization direction as the central region 355. In FIG. 7A, the shapes of the connection electrode 436 and the central region 357 are the same, but it is not necessary to do so. In the piezoelectric ceramic layer 321b sandwiched between the extraction electrode 335b and the common electrode, the surrounding region 356 around the central region 357 is polarized in the opposite direction. By having such a configuration, when a voltage is applied to the extraction electrode 335b, the central region 357 and the surrounding region 356 of the piezoelectric ceramic layer 321a immediately below the same extend and contract in the planar direction, and piezoelectric elements opposite to each other. Since the deformation occurs, the deformation is canceled out, and crosstalk caused by the piezoelectric deformation of the piezoelectric ceramic layer 321a immediately below the extraction electrode 335b can be suppressed. In FIG. 7A, the surrounding area of the piezoelectric ceramic layer 321b sandwiched between the individual electrode body 335a and the common electrode, and the surrounding area of the piezoelectric ceramic layer 321b sandwiched between the extraction electrode 335b and the common electrode. There is no boundary between them and they are connected, but there may be a portion that is not polarized between them.

In FIG. 7B, the individual electrode 435 includes an individual electrode body 435a having a shape substantially similar to that of the liquid pressurizing chamber 410, and an extraction electrode 435b drawn from the individual electrode body 435a. The central region of the piezoelectric ceramic layer 421b sandwiched between the extraction electrode 435b and the common electrode is polarized in the stacking direction, and the direction of the piezoelectric ceramic layer 321b sandwiched between the individual electrode body 335a and the common electrode is The direction of polarization of the central region of the central region 355 is the same. In FIG. 7B, these two central regions are connected to form one central region 455. In the piezoelectric ceramic layer 321b sandwiched between the extraction electrode 435b and the common electrode, the surrounding region 456 around the central region 455 is polarized in the opposite direction. With such a configuration, when a voltage is applied to the extraction electrode 435b, the central region 455 and the surrounding region 456 of the piezoelectric ceramic layer 421a immediately below the electrode extend and contract in the plane direction, and piezoelectrics opposite to each other are obtained. Since the deformation occurs, the deformation is canceled out, and crosstalk caused by the piezoelectric deformation of the piezoelectric ceramic layer 421a immediately below the extraction electrode 435b can be suppressed. In FIG. 7B, the surrounding area of the piezoelectric ceramic layer 421b sandwiched between the individual electrode body 435a and the common electrode, and the surrounding area of the piezoelectric ceramic layer 421b sandwiched between the extraction electrode 435b and the common electrode. There is no boundary between them and they are connected, but there may be a portion that is not polarized between them.

  In the liquid ejection head shown in FIG. 7C, when viewed in plan, the region including the central region 555 and the surrounding region 556 is substantially similar in shape to the shape of the liquid pressurizing chamber 510 and has the area of the liquid. The connection electrode 536 is formed at a position that is at least one times the area of the pressurization chamber and does not overlap the liquid pressurization chamber 510 of the individual electrode 535, and the connection electrode 536 and the external wiring are electrically connected. Since the connection with the external wiring is made at a position where it does not overlap with the liquid pressurizing chamber 510, this connection portion is preferable because it does not hinder the displacement of the displacement element. Further, since the symmetry of the structure in the planar direction is not broken for connection with the external wiring and there is no protruding portion, crosstalk due to such a portion does not occur, which is preferable.

  The liquid discharge head 2 as described above is manufactured as follows, for example. First, lead zirconate titanate (PZT) is used as the piezoelectric material for the piezoelectric ceramic layer, and a slurry is prepared by mixing PZT powder, a binder, and a solvent. From this slurry, a roll coater method is adopted as a forming method. A green sheet is produced.

  Next, a through hole serving as a via hole is formed in one green sheet by punching with a mold. A conductive paste to be the common electrode 34 is applied to another green sheet and dried. These two green sheets are laminated to produce a laminated molded body having a common electrode 34 and a via hole inside. The laminated compact is fired at a temperature of 1020 ° C. to produce a piezoelectric sintered body.

  Next, the flow path member 4 is produced by laminating plates 22 to 31 obtained by a rolling method or the like. Holes to be the manifold 5, the individual supply flow path 6, the liquid pressurizing chamber 10, the descender, and the like are processed in the plates 22 to 31 into a predetermined shape by etching.

  These plates 22 to 31 are preferably formed of at least one metal selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, particularly when ink is used as a liquid. Since it is desired to be made of a material having excellent corrosion resistance against ink, Fe-Cr is more preferable.

  The piezoelectric sintered body and the flow path member 4 can be laminated and bonded through, for example, an adhesive layer. As the adhesive layer, a well-known layer can be used, but in order not to affect the piezoelectric sintered body and the flow path member 4, an epoxy resin, phenol resin, polyphenylene having a thermosetting temperature of 100 to 150 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of ether resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric sintered body and the flow path member 4 can be heated and joined.

  The subsequent steps of polarization of the piezoelectric sintered body and formation of the individual electrodes 35 will be described using FIGS. 9A to 9E shown in the order of the steps. In addition, by performing polarization after stacking, the piezoelectric ceramic layer is not deformed by polarization and is not easily stacked.

FIG. 9A is a partial longitudinal sectional view of a state in which a piezoelectric sintered body composed of the piezoelectric ceramic layer 21 b, the vibration plate 21 a and the common electrode 34 is joined to the flow path member 4. The flow path member 4 is omitted except for the plate 22 which is a part thereof. In FIG. 9B, a polarization electrode 35-1 is formed, and the piezoelectric ceramic layer 21b sandwiched between the polarization electrode 35-1 and the common electrode 34 is polarized in the stacking direction. Here, a part of the polarized portion becomes the surrounding region 56 later. The arrow in the figure is the polarization direction. For example, the polarization electrode 35-1 is made of silver as a main component. The polarization electrode 35-1 may be formed on almost the entire surface of the piezoelectric ceramic layer 21b so as to polarize almost the whole. Such a configuration is preferable because a positional shift hardly occurs between the polarized region and the individual electrode 35 to be formed later. In FIG. 9C, the polarization electrode 35-1 is removed. The polarization electrode 35-1 is removed by cleaning with an organic solvent, ultrasonic cleaning, or the like. If the porcelain is thin, it may be damaged by ultrasonic cleaning, so it is preferable to remove it with a cleaning solution such as organic solvent cleaning.

  Subsequently, in FIG. 9D, a polarization electrode 35-2 is formed, and the piezoelectric ceramic layer 21b sandwiched between the polarization electrode 35-2 and the common electrode 34 is polarized in FIG. 9B. Is polarized in the opposite stacking direction. Here, the polarized portion becomes the central region 55. In FIG. 9E, the individual electrode 35 is formed. The individual electrode 35 may be newly formed after removing the polarization electrode 35-2 and the polarization electrode 35-2, or may be formed so as to partially overlap the polarization electrode 35-2. If the electrode 35-2 is formed after the polarization electrode 35-2 is removed, the thickness of the individual electrode 35 can be reduced by the amount of the polarization electrode 35-2, so that the displacement can be increased. At that time, the polarization electrode 35-2 is removed in the same manner as the polarization electrode 35-1. If it is formed so as to partially overlap the polarization electrode 35-2, the process can be simplified. In that case, the electrode 35-2 for polarization masks, for example, forms an Au electrode by sputtering or vapor deposition. In this way, the liquid discharge head 2 can be manufactured.

A liquid discharge head having the structure shown in FIGS. 1 to 6 was produced and evaluated. However, since it is clear in principle that there is an effect of suppressing drive deterioration and crosstalk, the liquid discharge head is used for evaluation in which the flow path member below the liquid pressurizing chamber opens to the bottom. Was manufactured, and the displacement was measured with a laser displacement meter and evaluated. The manufactured liquid discharge head has the liquid pressurizing chamber area Sc [mm ² ], the central area area So [mm ² ], and the surrounding area area Si [mm ² ] shown in Table 1, and So + Si> Sc. For example, the structure shown in FIG. 6A is obtained. If So + Si <Sc, the structure shown in FIG. 6B is obtained.

  Sample No. Reference numeral 1 denotes a sample outside the scope of the present invention, in which no surrounding area is provided. In the case where no surrounding region is provided, it is known that there is a point where the displacement amount becomes maximum with respect to the increase in the area ratio So / Sc. 1 of So / Sc = 0.562 corresponds to this point, and in the structure in which no surrounding region is provided, the sample No. A mutation greater than 1 cannot be obtained. Further, the displacement amount itself varies depending on the thickness of the displacement element, but there is almost no difference in the maximum point.

As shown in Table 1, sample no. 12 is So / Sc = 0.450, and the area ratio of So is Sample No. Although it is lower than 1, the peripheral region is formed, so that the sample No. in which the displacement is maximum when the peripheral region is not formed. The displacement was larger than 1. This means that sample no. 12 is that the displacement is larger than that in the case where So / Sc = 0.450 and no surrounding area is formed. Thus, by setting So / Sc to be 0.45 or more, the direction of displacement can be made the same as when the surrounding region is not formed, and the amount of displacement can be made larger than when the surrounding region is not formed.

  Sample No. 2 to 7 change only the surrounding area Si. It can be seen that the displacement increases as the peripheral region area Si increases. The increase in displacement continues even if the surrounding region extends outside the liquid pressurizing chamber and So + Si> Sc, but virtually disappears at (So + Si) /Sc=1.440. This is because, as the distance between the outer peripheral portion of the surrounding region and the liquid pressurizing chamber increases, the influence of the piezoelectric deformation of the outer peripheral portion has little effect on the displacement of the displacement element directly above the liquid pressurizing chamber. It is thought to be due to becoming. Therefore, the increase in displacement continues because (So + Si) / Sc is in the range of 1.440 or less, so in order to reduce the crosstalk while increasing the displacement. (So + Si) / Sc may be set to 1.440 or less.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 5 ... Manifold 5a ... Sub manifold 5b ... Opening 6 ... Individual supply flow path 8 ... Liquid discharge hole 9 ... Liquid pressurization chamber group 10, 210, 310, 410, 510 ... Liquid pressurization chamber 11a, b, c, d ... Liquid pressurization chamber row 12 ... Squeeze 15a, b, c , D: liquid discharge hole array 21: piezoelectric actuator unit 21a: piezoelectric ceramic layer (vibrating plate)
21b, 221b, 321b, 421b, 521b ... piezoelectric ceramic layers 22-31 ... plate 32 ... individual flow path 34 ... common electrode 35,235,335,435,535 ... individual electrode 35a 235a, 335a, 435a ... individual electrode body 35b, 235b, 335b, 435b ... extraction electrode 36, 236, 336, 436, 536 ... connection electrode 50 ... displacement element 55, 255, 355, 455, 555 ... (the piezoelectric ceramic layer sandwiched between the individual electrode body and the common electrode) Central region 56, 256, 356, 456, 556 ... (piezoelectric sandwiched between the individual electrode body and the common electrode) Peripheral region 357 ... (the ceramic layer) Central region (of the piezoelectric ceramic layer sandwiched between the extraction electrode and the common electrode) 60 External wiring

Claims (4)

A piezoelectric actuator unit is laminated on the flow path member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes connected to the plurality of liquid pressurizing chambers so as to cover the plurality of liquid pressurizing chambers. The piezoelectric actuator unit is formed by laminating a diaphragm, a common electrode, a piezoelectric body, and a plurality of individual electrodes in this order from the flow path member side. Each of the electrodes is disposed so as to overlap the plurality of liquid pressurizing chambers, and is located in the center of the plurality of liquid pressurizing chambers, and is sandwiched between the individual electrode and the common electrode. The central region of the piezoelectric body is polarized in the stacking direction, and the peripheral region around the central region of the piezoelectric body sandwiched between the individual electrodes and the common electrode is polarized in a direction opposite to the central region. And, wherein the individual electrodes, and the individual electrode body is led from the individual by the electrode body, includes a lead electrode that is external wiring electrically connected, sandwiched between the common electrode and the extraction electrode The central region located at the center of the piezoelectric body is polarized in the same direction as the central region of the piezoelectric body sandwiched between the individual electrode and the common electrode, and the extraction electrode The region around the piezoelectric body sandwiched between the common electrode and the common electrode is polarized in the same direction as the surrounding region of the piezoelectric body sandwiched between the individual electrode and the common electrode. Liquid discharge head. When viewed in plan, the area of the central region of the piezoelectric body sandwiched between the individual electrode and the common electrode is 0.45 to 1 times the area of the liquid pressurizing chamber. The liquid discharge head according to claim 1. When viewed in plan, the central region of the piezoelectric body sandwiched between the individual electrode and the common electrode and the peripheral region of the piezoelectric body sandwiched between the individual electrode and the common electrode are combined. 3. The liquid according to claim 1, wherein the region has a shape substantially similar to the shape of the liquid pressurizing chamber and has an area of 1.44 times or less the area of the liquid pressurizing chamber. Discharge head. Includes a liquid discharge head according to any one of claims 1 to 3, the conveyance unit that conveys the recording medium to the liquid ejecting head, and a control unit for controlling the liquid discharge head and the conveying unit A recording apparatus.

Images