JP7533162B2 - Piezoelectric actuator and method for manufacturing liquid ejection head having piezoelectric actuator and flow path unit - Google Patents

Description

The present invention relates to a piezoelectric actuator having at least three piezoelectric layers and three electrode layers, and a method for manufacturing a liquid ejection head having a piezoelectric actuator and a flow path unit.

Patent document 1 shows an inkjet head (liquid ejection head) that includes a piezoelectric actuator having three piezoelectric layers (first to third piezoelectric layers) and three electrode layers (a drive electrode, a high potential electrode, and a low potential electrode), and a flow path unit in which a flow path including multiple nozzles and multiple pressure chambers is formed.

JP 2018-034474 A

When adhering the piezoelectric actuator to the flow path unit, in order to position the piezoelectric actuator and the flow path unit, it is possible to form a first through hole in one of the first and third electrode layers in advance, and form a second through hole in the second electrode layer that overlaps with the first through hole. In this case, light is irradiated from one of the first and third electrode layers to the other of the piezoelectric actuator. The light passes through the piezoelectric layers but does not pass through the electrode layers, passes through the first and second through holes, and then passes through the other of the first and third piezoelectric layers. The second through hole is detected from the image obtained by this irradiation, and the piezoelectric actuator and the flow path unit are positioned based on the second through hole.

However, the periphery of the first through hole is prone to bleeding on the upstream side of the printing direction of the screen printing, especially when the electrode layer is formed by screen printing. In this case, the bleeding on the periphery of the first through hole prevents light from passing through, so the second through hole cannot be detected accurately, which can cause a problem in that the piezoelectric actuator and the flow path unit cannot be properly positioned.

The object of the present invention is to provide a piezoelectric actuator and a method for manufacturing a liquid ejection head that allows proper positioning of the piezoelectric actuator and the flow path unit.

According to a first aspect of the present invention, a piezoelectric element includes a first piezoelectric layer, a second piezoelectric layer stacked on the first piezoelectric layer in a first direction along the thickness direction of the first piezoelectric layer, a third piezoelectric layer stacked on the first piezoelectric layer and the second piezoelectric layer in the first direction and sandwiching the second piezoelectric layer between the first piezoelectric layer, a first electrode layer arranged on a surface of the first piezoelectric layer opposite the second piezoelectric layer in the first direction, a second electrode layer arranged between the first piezoelectric layer and the second piezoelectric layer in the first direction, and a third electrode layer arranged between the second piezoelectric layer and the third piezoelectric layer in the first direction, and the first electrode layer is provided with a plurality of driving electrodes to which either a first potential or a second potential different from the first potential is selectively applied. The piezoelectric actuator includes a first electrode, the second electrode layer includes a first potential electrode held at the first potential, the third electrode layer includes a second potential electrode held at the second potential, one of the first electrode layer and the third electrode layer has a first through hole, a first thick portion defining the first through hole, and a first thin portion connected to the first thick portion and having a thickness in the first direction smaller than that of the first thick portion, the first thin portion being disposed upstream in the first through hole in a second direction perpendicular to the first direction, the second electrode layer has a second through hole overlapping the first through hole in the first direction, and the center of the second through hole is located downstream in the second direction relative to the center of the first through hole.

According to a second aspect of the present invention, there is provided a piezoelectric element including a first piezoelectric layer, a second piezoelectric layer stacked on the first piezoelectric layer in a first direction along the thickness direction of the first piezoelectric layer, a third piezoelectric layer stacked on the first piezoelectric layer and the second piezoelectric layer in the first direction and sandwiching the second piezoelectric layer between the first piezoelectric layer and the third piezoelectric layer, a first electrode layer arranged on the surface of the first piezoelectric layer opposite the second piezoelectric layer in the first direction, a second electrode layer arranged between the first piezoelectric layer and the second piezoelectric layer in the first direction, and a third electrode layer arranged between the second piezoelectric layer and the third piezoelectric layer in the first direction. The piezoelectric actuator is provided, in which the first electrode layer includes a plurality of drive electrodes to which either a first potential or a second potential different from the first potential is selectively applied, the second electrode layer includes a first potential electrode held at the first potential, the third electrode layer includes a second potential electrode held at the second potential, one of the first electrode layer and the third electrode layer has a first through hole that opens in a notch shape at one end of the electrode layer in a fourth direction perpendicular to the first direction, and the second electrode layer has a second through hole that overlaps with the first through hole in the first direction.

According to a third aspect of the present invention, a method for manufacturing a piezoelectric actuator includes an actuator fabrication process for fabricating a piezoelectric actuator in which a first piezoelectric layer, a second piezoelectric layer, and a third piezoelectric layer are stacked in a first direction along the thickness direction of the first piezoelectric layer, and an adhesion process for adhering the piezoelectric actuator to a flow path unit in which a flow path including a plurality of nozzles and a plurality of pressure chambers each communicating with the plurality of nozzles is formed. The actuator fabrication process includes forming, by screen printing, a first electrode layer including a plurality of driving electrodes to which either a first potential or a second potential different from the first potential is selectively applied on the surface of the first piezoelectric layer. a first electrode layer forming step of forming a first electrode layer including a first potential electrode held at the first potential on a surface of the second piezoelectric layer by screen printing; a third electrode layer forming step of forming a third electrode layer including a second potential electrode held at the second potential on a surface of the third piezoelectric layer by screen printing; and after the first electrode layer forming step, the second electrode layer forming step, and the third electrode layer forming step, the first electrode layer is disposed on a surface of the first piezoelectric layer opposite to the second piezoelectric layer in the first direction, and the second electrode layer is disposed on a surface of the third piezoelectric layer opposite to the first potential electrode on the surface of the third piezoelectric layer by screen printing. and a laminating step of laminating the first piezoelectric layer, the second piezoelectric layer, and the third piezoelectric layer in the first direction such that the first piezoelectric layer, the second piezoelectric layer, and the third electrode layer are disposed between the first piezoelectric layer and the second piezoelectric layer in the first direction, wherein in one of the first electrode layer forming step and the third electrode layer forming step, a first through hole is formed in the electrode layer, and in the second electrode layer forming step, a second through hole is formed in the second electrode layer, the second through hole overlapping with the first through hole in the first direction, the center of which is in the first direction with respect to the center of the first through hole. A second through hole is formed downstream in a second direction perpendicular to the first electrode layer forming step and downstream in the printing direction of the screen printing in one of the first electrode layer forming step and the third electrode layer forming step, and the bonding process includes an imaging step of irradiating the piezoelectric actuator with light from one of the first electrode layer and the third electrode layer in which the first through hole is formed to the other, thereby obtaining an imaging result, and a positioning step of positioning the piezoelectric actuator and the flow path unit based on the imaging result.

1 is a diagram showing the overall configuration of a printer 1 including a piezoelectric actuator according to a first embodiment of the present invention. FIG. FIG. 3 is an enlarged view of region III in FIG. 2 . FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 4 is a cross-sectional view taken along line VV in FIG. 3. 6A to 6C are diagrams illustrating the operation of the actuator section 90 in the cross section of FIG. 5. 3 is a plan view showing the top surface of the uppermost piezoelectric layer 41 of the three piezoelectric layers 41 to 43 that constitute the piezoelectric actuator 22 in FIG. 2. 3 is a plan view showing the upper surface of the middle piezoelectric layer 42 of the three piezoelectric layers 41 to 43 that constitute the piezoelectric actuator 22 in FIG. 2. 3 is a plan view showing the upper surface of the lowermost piezoelectric layer 43 of the three piezoelectric layers 41 to 43 that constitute the piezoelectric actuator 22 in FIG. 2. FIG. 9 is an enlarged view of region X in FIG. 8 . 11 is a cross-sectional view taken along line XI-XI of FIG. 12 is a diagram showing a step of forming a high-potential connecting electrode portion 57 on the upper surface of the piezoelectric layer 43 by screen printing, and corresponds to region XII in FIG. 11 . 4 is a flow diagram showing a manufacturing method of the head 3. FIG. 9 is a view corresponding to FIG. 8 and showing a piezoelectric actuator 222 according to a second embodiment of the present invention. 10 is a view corresponding to FIG. 9 and showing a piezoelectric actuator 222 according to a second embodiment of the present invention. FIG. 15 is an enlarged view of region XVI of FIG. 14. 17 is a cross-sectional view taken along line XVII-XVII in FIG. 16.

In the following description, the Z direction is the vertical direction, and the X and Y directions are the horizontal directions. Both the X and Y directions are perpendicular to the Z direction. The X direction is perpendicular to the Y direction.

<Overall printer configuration>
First, with reference to FIG. 1, the overall configuration of a printer 1 including a piezoelectric actuator according to a first embodiment of the present invention will be described.

The printer 1 has a head 3, a carriage 2, and two pairs of transport rollers 4.

The carriage 2 is supported by two guide rails 5 extending in the Y direction and can move in the Y direction along the guide rails 5.

The head 3 is of a serial type, is mounted on the carriage 2, and is movable in the Y direction together with the carriage 2. A number of nozzles 15 are formed on the underside of the head 3.

The two transport roller pairs 4 are arranged in the X direction, sandwiching the carriage 2 between them. When the transport roller pairs 4 rotate while holding the paper P, the paper P is transported in the transport direction along the X direction.

The control unit (not shown) of the printer 1 alternates between an ejection operation in which ink is ejected from the nozzles 15 while moving the head 3 in the Y direction together with the carriage 2, and a transport operation in which the transport roller pair 4 transports the paper P a predetermined distance in the transport direction. This causes an image to be recorded on the paper P.

<Head configuration>
2, the head 3 has a flow passage unit 21 and a piezoelectric actuator 22 according to the first embodiment of the present invention. The flow passage unit 21 and the piezoelectric actuator 22 are both rectangular in shape, with the length in the X direction being longer than the length in the Y direction, in a plane perpendicular to the Z direction.

<Configuration of Flow Path Unit>
As shown in FIG. 4, the flow passage unit 21 is composed of four metal plates 31 to 34 stacked in the Z direction.

A plurality of pressure chambers 10 are formed in the plate 31. A communication passage 12, 13 is formed in the plate 32 for each pressure chamber 10. The communication passages 12, 13 overlap one end and the other end of the corresponding pressure chamber 10 in the Y direction in the Z direction. A communication passage 14 is formed in the plate 33 for each communication passage 13. The communication passage 14 overlaps the corresponding communication passage 13 in the Z direction. The plate 33 further has 12 manifold channels 11. The manifold channels 11 are provided for each row 10R (see FIG. 2) of pressure chambers 10 arranged in the X direction. Each manifold channel 11 extends in the X direction and communicates with the plurality of pressure chambers 10 belonging to the corresponding row 10R via the communication passage 12. A plurality of nozzles 15 are formed in the plate 34. Each nozzle 15 overlaps with the communication passage 14 in the Z direction.

Four ink supply ports 8 are formed on the upper surface of the plate 31 in an area where the piezoelectric actuators 22 are not arranged (see FIG. 2). Each ink supply port 8 communicates with an ink cartridge (not shown) and also communicates with three manifold channels 11. Ink supplied from the ink cartridge to each ink supply port 8 is supplied to the three manifold channels 11. Ink is supplied from each manifold channel 11 to a plurality of pressure chambers 10 belonging to each row 10R via a communication channel 12. Then, as described below, when the piezoelectric actuator 22 is driven, pressure is applied to the ink in the pressure chamber 10, and ink is ejected from the nozzle 15 through the communication channels 13 and 14.

<Configuration of Piezoelectric Actuator>
4, the piezoelectric actuator 22 is disposed on the upper surface of the flow path unit 21. The piezoelectric actuator 22 has three piezoelectric layers 41 to 43, a plurality of driving electrodes 51, a high potential electrode 52, and a low potential electrode 53.

The three piezoelectric layers 41 to 43 are stacked in the Z direction, with the Z direction being the thickness direction. Piezoelectric layer 42 is stacked in the Z direction on piezoelectric layer 41. Piezoelectric layer 43 is stacked in the Z direction on piezoelectric layers 41 and 42, with piezoelectric layer 42 sandwiched between piezoelectric layer 41 and piezoelectric layer 43. The Z direction corresponds to the "first direction" of the present invention. Piezoelectric layer 41 corresponds to the "first piezoelectric layer" of the present invention, piezoelectric layer 42 corresponds to the "second piezoelectric layer" of the present invention, and piezoelectric layer 43 corresponds to the "third piezoelectric layer" of the present invention.

The thickness of each piezoelectric layer 41-43 is the same (approximately 10-15 μm), and the total thickness of the piezoelectric layers 41-43 is approximately 30-45 μm. The central plane M in the Z direction of the three piezoelectric layers 41-43 is within the piezoelectric layer 42 (see FIG. 11).

Each piezoelectric layer 41 to 43 is made of a piezoelectric material whose main component is lead zirconate titanate or the like.

The piezoelectric layer 43 is disposed on the upper surface of the plate 31 and covers all of the pressure chambers 10 formed in the plate 31. The piezoelectric actuator 22 and the flow path unit 21 are bonded to each other by an adhesive (not shown) disposed between the piezoelectric layer 43 and the plate 31.

As shown in FIG. 3, the driving electrodes 51 are arranged on the upper surface of the piezoelectric layer 41 in correspondence with the pressure chambers 10. Each driving electrode 51 has a main portion 51a and a protruding portion 51b. The main portion 51a overlaps with substantially the entire area of the corresponding pressure chamber 10 in the Z direction. The protruding portion 51b protrudes from the main portion 51a in the Y direction and does not overlap with the corresponding pressure chamber 10 in the Z direction. The protruding portion 51b is provided with a contact that is electrically connected to a COF (Chip On Film) (not shown). A driver IC (not shown) mounted on the COF selectively applies either a high potential (VDD potential) or a low potential (GND potential) to each driving electrode 51 individually via the wiring of the COF under the control of the control unit.

As shown in FIG. 7, the multiple drive electrodes 51 are arranged in the X direction in the central region of the top surface of the piezoelectric layer 41 (region excluding both ends of the piezoelectric layer 41 in the X direction and both ends of the piezoelectric layer 41 in the Y direction), forming multiple drive electrode rows 51R corresponding to the rows 10R of the pressure chambers 10 (see FIG. 2). The multiple drive electrode rows 51R are aligned in the Y direction.

Dummy electrodes 59 are provided on one side (upper side in FIG. 7) and the other side (lower side in FIG. 7) of each drive electrode row 51R in the X direction. The dummy electrodes 59 have the same size and shape in a plane perpendicular to the Z direction as the drive electrodes 51 belonging to the corresponding drive electrode row 51R, and are arranged at equal intervals in the X direction together with the drive electrodes 51. The dummy electrodes 59 are not electrically connected to the COF, and no potential is applied to them. By providing the dummy electrodes 59, the difference in the amount of shrinkage due to electrode formation between the drive electrodes 51 at the center in the X direction and the drive electrodes 51 at the ends in the X direction in each drive electrode row 51R can be suppressed, and thus the variation in the amount of ejection from the multiple nozzles 15 corresponding to each drive electrode row 51R can be suppressed.

In addition to the drive electrode 51 and the dummy electrode 59, two high potential connection electrode parts 54 and two low potential connection electrode parts 55 are provided on the upper surface of the piezoelectric layer 41.

The two high potential connection electrodes 54 are arranged on one side of the piezoelectric layer 41 in the X direction (upper side in FIG. 7) at one end (left end in FIG. 7) and the other end (right end in FIG. 7) of the piezoelectric layer 41 in the Y direction. The two low potential connection electrodes 55 are arranged on the other side of the piezoelectric layer 41 in the X direction (lower side in FIG. 7) at one end (left end in FIG. 7) and the other end (right end in FIG. 7) of the piezoelectric layer 41 in the Y direction.

The two high potential connection electrode sections 54 are each composed of eight end electrodes 54a spaced apart from each other in the X direction. The two low potential connection electrode sections 55 are each composed of eight end electrodes 55a spaced apart from each other in the X direction. The end electrodes 54a, 55a have approximately the same size and shape in a plane perpendicular to the Z direction. Under the control of the control section, the driver IC applies a high potential (VDD potential) to the end electrodes 54a and a low potential (GND potential) to the end electrodes 55a via the COF wiring.

Of the eight end electrodes 54a constituting each high potential connection electrode portion 54, seven end electrodes 54a are arranged at equal intervals in the X direction, excluding the end electrode 54a located at one end in the X direction (the upper end in FIG. 7). The end electrode 54a located at one end in the X direction (the upper end in FIG. 7) is arranged in the X direction at an interval A that is larger than the intervals between the seven end electrodes 54a.

Of the eight end electrodes 55a constituting each low potential connection electrode portion 55, seven end electrodes 55a are arranged at equal intervals in the X direction, excluding the end electrode 55a located at the other end in the X direction (the lower end of FIG. 7). The end electrode 55a located at the other end in the X direction (the lower end of FIG. 7) is arranged in the X direction at an interval A that is larger than the intervals between the seven end electrodes 55a.

As shown in FIG. 8, the high potential electrode 52 is disposed on the upper surface of the piezoelectric layer 42 and includes a trunk 521, a number of branches 523 extending from the trunk 521, a number of individual parts 52a connected to each branch 523, and two overlapping parts 524.

The trunk 521 extends in the Y direction from one end of the piezoelectric layer 42 in the X direction (the upper end in FIG. 8). The multiple branch portions 523 are aligned in the Y direction and each extends from the trunk 521 to the other side in the X direction (the lower side in FIG. 8). Each individual portion 52a overlaps in the Z direction with the central portion of each pressure chamber 10 in the X direction (see FIG. 5).

One of the two overlapping portions 524 is connected to one end of the trunk 521 in the Y direction (left end in FIG. 8) and to a branch 523 located at one end in the Y direction (left end in FIG. 8) of the multiple branch portions 523. The other of the two overlapping portions 524 is connected to the other end of the trunk 521 in the Y direction (right end in FIG. 8) and to a branch 523 located at the other end in the Y direction (right end in FIG. 8) of the multiple branch portions 523. The two overlapping portions 524 extend in the X direction at one end (left end in FIG. 8) and the other end (right end in FIG. 8) of the piezoelectric layer 42 in the Y direction, respectively.

The two overlapping portions 524 each overlap in the Z direction with the three end electrodes 54a (the three end electrodes 54a arranged on one end side in the X direction (upper side in Figure 7)) of the high-potential connection electrode portion 54 and the portion corresponding to the interval A, and are electrically connected to the three end electrodes 54a via through holes formed in the piezoelectric layer 41.

In addition to the high potential electrode 52, two low potential connection electrode parts 56, two floating electrode parts 64, and a floating electrode part 65 are provided on the upper surface of the piezoelectric layer 42.

The two low potential connection electrode parts 56 are respectively arranged on the other side in the X direction (lower side in FIG. 8) of the piezoelectric layer 42 at one end (left end in FIG. 8) and the other end (right end in FIG. 8) of the piezoelectric layer 42 in the Y direction. Each of the two low potential connection electrode parts 56 is composed of two end electrodes 56a and one end electrode 56b arranged at a distance from each other in the X direction.

The two floating electrode sections 64 are disposed at one end (left end in FIG. 8) and the other end (right end in FIG. 8) of the piezoelectric layer 42 in the Y direction, between the overlapping section 524 and the low potential connection electrode section 56 in the X direction. Each of the two floating electrode sections 64 is composed of ten end electrodes 64a disposed at a distance from each other in the X direction.

The floating electrode section 65 is disposed at the other end of the piezoelectric layer 42 in the X direction (the lower end in FIG. 8). The floating electrode section 65 is composed of multiple end electrodes 65a disposed at a distance from each other in the Y direction. The end electrodes 65a have approximately the same size and shape in a plane perpendicular to the Z direction, and are disposed at equal intervals in the Y direction.

The end electrode 56a of the low potential connection electrode 56 and the end electrode 64a of the floating electrode 64 have approximately the same size and shape in a plane perpendicular to the Z direction, and are disposed at equal intervals in the X direction at each of one end (left end in FIG. 8) and the other end (right end in FIG. 8) of the piezoelectric layer 42 in the Y direction. On the other hand, the end electrode 56b of the low potential connection electrode 56 is longer in the X direction than the end electrode 56a.

The two end electrodes 56a overlap in the Z direction with the two end electrodes 55a of the low potential connection electrode section 55 (the two end electrodes 55a arranged second and third from the other end side in the X direction (the lower side in FIG. 7)) and are electrically connected to the two end electrodes 55a via through holes formed in the piezoelectric layer 41.

The end electrode 56b overlaps in the Z direction with one end electrode 55a (one end electrode 55a arranged at the other end in the X direction (the lower end of Figure 7)) of the low potential connection electrode part 55 and the part corresponding to the interval A, and is electrically connected to the one end electrode 55a via a through hole formed in the piezoelectric layer 41.

The end electrodes 64a, 65a of the floating electrode sections 64, 65 are not electrically connected to any of the electrodes and are not applied with a potential.

As shown in FIG. 9, the low potential electrode 53 is disposed on the upper surface of the piezoelectric layer 43 and includes a trunk 531, a number of branch portions 533 extending from the trunk 531, a number of individual portions 53a connected to each branch portion 533, and two overlapping portions 534.

The trunk 531 extends in the Y direction at the other end of the piezoelectric layer 43 in the X direction (the lower end in Figure 9). The multiple branch portions 533 are lined up in the Y direction, and each extends from the trunk 531 to one side in the X direction (the upper side in Figure 9). Of the multiple individual portions 53a, except for the individual portions 53a located at one and the other ends in the X direction, each individual portion 53a spans two pressure chambers 10 adjacent to each other in the X direction and has a portion that overlaps with the two pressure chambers 10 in the Z direction (see Figure 5). The individual portions 53a located at one and the other ends in the X direction have a portion that overlaps with one pressure chamber 10 in the Z direction.

One of the two overlapping portions 534 is connected to one end of the stem 531 in the Y direction (the left end in FIG. 9). The other of the two overlapping portions 524 is connected to the other end of the stem 531 in the Y direction (the right end in FIG. 9). The two overlapping portions 534 extend in the X direction at one end (the left end in FIG. 9) and the other end (the right end in FIG. 9) of the piezoelectric layer 43 in the Y direction, respectively.

The two overlapping portions 534 overlap in the Z direction with the three end electrodes 55a (the three end electrodes 55a arranged on the other end side in the X direction (the lower side of FIG. 7)) of the low potential connection electrode portion 55 and the portion corresponding to the interval A, as well as the three end electrodes 56a, 56b of the low potential connection electrode portion 56 (see FIG. 8). Each overlapping portion 534 is electrically connected to the three end electrodes 56a, 56b of the low potential connection electrode portion 56 through a through hole formed in the piezoelectric layer 42. The three end electrodes 56a, 56b are each electrically connected to the three end electrodes 55a of the low potential connection electrode portion 55 as described above. Therefore, each overlapping portion 534 is electrically connected to the low potential connection electrode portion 55 (see FIG. 7) through the low potential connection electrode portion 56 (see FIG. 8).

In addition to the low potential electrode 53, a high potential connection electrode portion 57 and two floating electrode portions 66 are provided on the upper surface of the piezoelectric layer 43.

The high potential connection electrode portion 57 has a portion 57a extending in the Y direction and two portions 57b extending in the X direction. The portion 57a extends in the Y direction at one end of the piezoelectric layer 43 in the X direction (the upper end in FIG. 9). One of the two portions 57b is connected to one end of the portion 57a in the Y direction (the left end in FIG. 9). The other of the two portions 57b is connected to the other end of the portion 57a in the Y direction (the right end in FIG. 9).

The two portions 57b overlap in the Z direction with the three end electrodes 54a (the three end electrodes 54a arranged on one end side in the X direction (upper side in FIG. 7)) of the high potential connection electrode portion 54 and the portion corresponding to the interval A, as well as with each overlapping portion 524 (see FIG. 8) of the high potential electrode 52. Each portion 57b is electrically connected to each overlapping portion 524 via a through hole formed in the piezoelectric layer 42. As described above, each overlapping portion 524 is electrically connected to the three end electrodes 54a of the high potential connection electrode portion 54. Therefore, the portion 57b is electrically connected to the high potential connection electrode portion 54 (see FIG. 7) via the overlapping portion 524 (see FIG. 8).

The two floating electrode sections 66 are respectively arranged at one end (left end in FIG. 9) and the other end (right end in FIG. 9) of the piezoelectric layer 43 in the Y direction, between the portion 57b and the overlapping portion 534 in the X direction. Each of the two floating electrode sections 66 is composed of ten end electrodes 66a arranged at a distance from each other in the X direction. The end electrodes 66a have approximately the same size and shape in a plane perpendicular to the Z direction, and are arranged at equal intervals in the X direction.

Each end electrode 66a of the floating electrode section 66 is not electrically connected to any electrode and is not applied with a potential.

<Actuator section>
5, a portion of the piezoelectric layer 41 sandwiched in the Z direction between the driving electrode 51 and the individual portion 52a of the high potential electrode 52 is referred to as a first active portion 91. A portion of the piezoelectric layers 42, 43 sandwiched in the Z direction between the driving electrode 51 and the individual portion 53a of the low potential electrode 53 is referred to as a second active portion 92. The first active portion 91 is mainly polarized upward, and the second active portion 92 is mainly polarized downward. The piezoelectric actuator 22 has an actuator portion 90 for each pressure chamber 10, which is composed of one first active portion 91 and two second active portions 92 sandwiching the first active portion 91 in the X direction.

Now, referring to Figure 6, we will explain the operation of the actuator unit 90 corresponding to a nozzle 15 when ink is ejected from that nozzle 15.

Before the printer 1 starts a recording operation, as shown in FIG. 6(a), a low potential (GND potential) is applied to each drive electrode 51. At this time, due to the potential difference between the drive electrode 51 and the high potential electrode 52, an upward electric field equal to the polarization direction is generated in the first active section 91, causing the first active section 91 to contract in the planar direction (directions along the X and Y directions). As a result, the portion of the laminate consisting of the piezoelectric layers 41 to 43 that overlaps with the pressure chamber 10 in the Z direction is bent so as to be convex (downward) toward the pressure chamber 10. At this time, the volume of the pressure chamber 10 is smaller than when the laminate is flat.

When the printer 1 starts a recording operation and ink is ejected from a certain nozzle 15, first, as shown in FIG. 6B, the potential of the drive electrode 51 corresponding to the nozzle 15 is switched from a low potential (GND potential) to a high potential (VDD potential). At this time, the potential difference between the drive electrode 51 and the high potential electrode 52 disappears, and the contraction of the first active section 91 is eliminated. On the other hand, the potential difference between the drive electrode 51 and the low potential electrode 53 occurs, and a downward electric field equal to the polarization direction is generated in the second active section 92, and the second active section 92 contracts in the planar direction. However, the second active section 92 has a function of suppressing crosstalk (a phenomenon in which pressure fluctuations accompanying deformation of the actuator section 90 in a certain pressure chamber 10 are transmitted to another pressure chamber 10 adjacent to the pressure chamber 10 in the X direction), and does not contribute much to the deformation of the actuator section 90. In other words, at this time, the laminate is in a flat state, with the portion that overlaps with the pressure chamber 10 in the Z direction not bending so as to be convex (upward) away from the pressure chamber 10. As a result, the volume of the pressure chamber 10 becomes larger than that in FIG. 6(a).

6A, the potential of the drive electrode 51 corresponding to the nozzle 15 is switched from high potential (VDD potential) to low potential (GND potential). At this time, the potential difference between the drive electrode 51 and the low potential electrode 53 disappears, and the contraction of the second active portion 92 is eliminated. On the other hand, the potential difference between the drive electrode 51 and the high potential electrode 52 occurs, and an upward electric field equal to the polarization direction is generated in the first active portion 91, and the first active portion 91 contracts in the planar direction. As a result, the portion of the laminate that overlaps with the pressure chamber 10 in the Z direction is bent so as to be convex (downward) toward the pressure chamber 10. At this time, the volume of the pressure chamber 10 is greatly reduced, and a large pressure is applied to the ink in the pressure chamber 10, and ink is ejected from the nozzle 15.

Description of the Invention
The driving electrode 51, the dummy electrode 59, the high potential connection electrode portion 54, and the low potential connection electrode portion 55 arranged on the upper surface of the piezoelectric layer 41 (the surface of the piezoelectric layer 41 opposite to the piezoelectric layer 42 in the Z direction) constitute the first electrode layer 71 (see FIG. 7). The high potential electrode 52, the low potential connection electrode portion 56, and the floating electrode portions 64 and 65 arranged on the upper surface of the piezoelectric layer 42 (between the piezoelectric layer 41 and the piezoelectric layer 42 in the Z direction) constitute the second electrode layer 72 (see FIG. 8). The low potential electrode 53, the high potential connection electrode portion 57, and the floating electrode portion 66 arranged on the upper surface of the piezoelectric layer 43 (between the piezoelectric layer 42 and the piezoelectric layer 43 in the Z direction) constitute the third electrode layer 73 (see FIG. 9). The thickness of the first electrode layer 71, the second electrode layer 72, and the third electrode layer 73 in the Z direction is 0.5 to 1.5 μm. The first electrode layer 71 and the second electrode layer 72 have the same thickness, and the third electrode layer 73 has a thickness greater than the thicknesses of the first electrode layer 71 and the second electrode layer 72 (see FIGS. 4 to 6 and 11).

The high potential corresponds to the "first potential" of the present invention, and the high potential electrode 52 corresponds to the "first potential electrode" of the present invention. The low potential corresponds to the "second potential" of the present invention, and the low potential electrode 53 corresponds to the "second potential electrode" of the present invention.

As shown in FIG. 9, a through hole 81 is formed in each of the two portions 57b of the high potential connection electrode portion 57 and the two overlapping portions 534 of the low potential electrode 53. The through hole 81 corresponds to the "first through hole" of the present invention.

As shown in FIG. 8, a through hole 82 is formed in each of the two overlapping portions 524 of the high potential electrode 52 and the two end electrodes 56b of the low potential connection electrode portion 56. The through holes 82 correspond to the "second through holes" of the present invention. Each through hole 82 overlaps with each through hole 81 shown in FIG. 9 in the Z direction. An internal electrode 83 is provided inside each through hole 82.

In this manner, in this embodiment, a set of through holes 81, through holes 82, and internal electrodes 83 that overlap each other in the Z direction (first direction D1) is provided at the four corners of the piezoelectric actuator 22.

Through hole 81, through hole 82 and internal electrode 83 are all circular, but as shown in FIG. 10, they are different in size (diameter), and centers O1, O2, O3 are at different positions in the Y direction. In detail, through hole 81 is larger in size (diameter) than through hole 82 and internal electrode 83, and through hole 82 is larger in size (diameter) than internal electrode 83. In each set of through hole 81, through hole 82 and internal electrode 83 that overlap in the Z direction (first direction D1), centers O1, O2, O3 are at the same position in the X direction but at different positions in the Y direction.

When one side of the Y direction is the "second direction D2" and the other side of the Y direction is the "third direction D3", the center O2 of the through hole 82 is located downstream of the center O1 of the through hole 81 in the second direction D2. The center O3 of the internal electrode 83 is located downstream of the center O2 of the through hole 82 in the third direction Y3.

The distance (first distance) L1 in the Y direction between the center O1 of the through hole 81 and the center O2 of the through hole 82 is greater than the distance (second distance) L2 in the Y direction between the center O3 of the internal electrode 83 and the center of the through hole 82.

9 and 10, each portion 57b of the high-potential connection electrode portion 57 in which the through hole 81 is formed has a thick portion (first thick portion) T1 that defines the through hole 81, and a thin portion (first thin portion) S1 that is connected to the thick portion T1 and has a smaller thickness in the Z direction than the thick portion T1, as shown in FIG. 11. The thin portion S1 protrudes from the lower end of the thick portion T1 in the second direction D2, and is disposed upstream of the through hole 81 in the second direction D2.

Each overlapping portion 534 of the low potential electrode 53 in which the through hole 81 is formed similarly has a thick portion (first thick portion) T1 and a thin portion (first thin portion) S1.

8 and 10, each overlapping portion 524 of the high potential electrode 52 in which the through hole 82 is formed has a thick portion (second thick portion) T2 that defines the through hole 82, and a thin portion (second thin portion) S2 that is connected to the thick portion T2 and has a smaller thickness in the Z direction than the thick portion T2, as shown in FIG. 11. The thin portion S2 protrudes from the lower end of the thick portion T2 in the third direction D3 and is disposed upstream of the through hole 82 in the third direction D3.

Each end electrode 56b of the low potential connection electrode portion 56 in which the through hole 82 is formed similarly has a thick portion (second thick portion) T2 and a thin portion (second thin portion) S2.

The above-described configuration of the thick portions T1, T2 and the thin portions S1, S2 results from the fact that each electrode layer 71 to 73 is formed by screen printing using a squeegee.

For example, when forming the high-potential connection electrode portion 57, as shown in FIG. 12, a mask 101 having holes 101x formed therein corresponding to the high-potential connection electrode portion 57 is placed on the upper surface of the piezoelectric layer 43, and the squeegee 100 is moved to form the high-potential connection electrode portion 57 by screen printing. At this time, the squeegee 100 moves while holding the electrode material (e.g., silver, nickel, gold, etc.) 110 on the downstream side of its movement direction (screen printing printing direction: second direction D2). The material 110 enters the holes 101x to form the thick portion T1. Furthermore, at this time, the material 110 flows into the thick portion T1 downstream of the movement direction, causing oozing A. This oozing A is formed as the thin portion S1.

The thickness of the thick portions T1 and T2 in the Z direction is approximately 0.5 to 1.5 μm, and the thickness of the thin portions S1 and S2 in the Z direction is 0.1 μm or less. The length of the thin portions S1 and S2 in the Y direction is, for example, 10 to 100 μm.

In this embodiment, the positions of the centers O1 to O3 of the through holes 81, 82 and the internal electrodes 83 are set so that the thin-walled portion S1 formed in the through hole 81 does not overlap with the through hole 82 in the Z direction, and so that the thin-walled portion S2 formed in the through hole 82 does not connect to the internal electrode 83.

<Head Manufacturing Method>
Next, a method of manufacturing the head 3 will be described with reference to FIG.

First, the piezoelectric actuator 22 is fabricated (S1: actuator fabrication step). In S1, the electrode layers 71-73 are formed on the upper surfaces (front surfaces) of the piezoelectric layers 41-43 by screen printing (S11: first to third electrode layer formation step), and then the piezoelectric layers 41-43 are stacked and bonded to each other (S12: stacking step).

In the third electrode layer formation step S11 (step of forming the third electrode layer 73), through holes 81 are formed in each of the two portions 57b of the high potential connection electrode portion 57 in the third electrode layer 73 and the two overlapping portions 534 of the low potential electrode 53 (see FIG. 9).

In the second electrode layer formation step S11 (step of forming the second electrode layer 72), through holes 82 are formed in each of the two overlapping portions 524 of the high potential electrode 52 in the second electrode layer 72 and the two end electrodes 56b of the low potential connection electrode portion 56, and an internal electrode 83 is formed inside each through hole 82 (see FIG. 8).

Here, the printing direction of the screen printing in the third electrode layer formation step is the second direction D2, whereas the printing direction of the screen printing in the second electrode layer formation step is the third direction D3 (the opposite direction to the second direction D2). In the second electrode layer formation step, the through hole 82 is formed so that its center O2 is located downstream of the center O1 of the through hole 81 in the second direction D2 (the printing direction of the screen printing in the third electrode layer formation step), and the internal electrode 83 is formed so that its center O3 is located downstream of the center O2 of the through hole 82 in the third direction D3 (the printing direction of the screen printing in the second electrode layer formation step).

After S1, the piezoelectric actuator 22 produced in S1 is bonded to the flow path unit 21 (S2: bonding step). In S2, a light source (e.g., an LED light source) is used to irradiate the piezoelectric actuator 22 with light from the third electrode layer 73 toward the first electrode layer 71 (from bottom to top in the Z direction (first direction D1) in FIG. 11) to obtain an image (S21: imaging step), and then the piezoelectric actuator 22 and the flow path unit 21 are positioned based on the image obtained in S21 (S22: positioning step).

In S21, light is transmitted through the piezoelectric layers 41-43 but not through the electrode layers 71-73. Light irradiated toward the through hole 81 passes through the portion of the through hole 81 excluding the thin portion S1, passes through the portion of the through hole 82 excluding the thin portion S2 and the internal electrode 83, and then passes through region A of the piezoelectric layer 41 before being received by the imaging element.

In S22, the positions of the four through holes 82 and the four internal electrodes 83 provided at the four corners of the piezoelectric actuator 22 are detected based on the imaging results obtained in S21, and the position of the center of gravity of the piezoelectric actuator 22 is determined from the positions of the through holes 82 and the internal electrodes 83.

After S2, the COF is attached to the piezoelectric actuator 22 (S3), completing the head 3. In S3, the wiring of the COF is connected to the drive electrode 51 provided on the upper surface of the piezoelectric layer 41 of the piezoelectric actuator 22, the end electrode 54a of the high potential connection electrode part 54, and the end electrode 55a of the low potential connection electrode part 55.

<Configuration and Effects of This Embodiment>
As described above, according to this embodiment, the center O2 of the through hole 82 is located downstream of the center O1 of the through hole 81 in the second direction D2 (the printing direction of the screen printing of the third electrode layer 73) (see FIGS. 10 and 11). In this case, as shown in FIG. 12, even if a smear A (thin portion S1) occurs on the periphery of the through hole 81 (upstream side in the second direction D2, upstream side in the printing direction of the screen printing of the third electrode layer 73) and the transmission of light is hindered by the smear A (thin portion S1), the through hole 82 is unlikely to overlap with the smear A (thin portion S1) in the Z direction (first direction D1), so that the through hole 82 can be detected with high accuracy. This allows the piezoelectric actuator 22 and the flow path unit 21 to be appropriately positioned.

The through-hole 82 is provided in the second electrode layer 72 including the high-potential electrode 52 (see FIG. 8). The position of the first active section 91 is determined by the position of the high-potential electrode 52 (see FIG. 5 and FIG. 6). The position of the first active section 91 significantly affects the deformation characteristics of the actuator section 90, so positioning of the high-potential electrode 52 is important. In this regard, in the present configuration, the position of the first active section 91 is accurately determined by performing positioning based on the through-hole 82 provided in the electrode layer 72 including the high-potential electrode 52, and the desired deformation characteristics of the actuator section 90 can be obtained.

The through hole 81 is provided in the low potential electrode 53 (see FIG. 9). When the through hole 81 is formed in the low potential electrode 53, if the size of the through hole 81 is increased, the electrical resistance increases (and thus a shortage of charge supply occurs), which may hinder the deformation of the actuator section 90. In this regard, in the present embodiment, the problem is solved by positioning the center O2 of the through hole 82 downstream in the second direction D2 from the center O1 of the through hole 81, so there is no need to make the through hole 81 excessively large. Therefore, the problem of the above-mentioned deformation hindering of the actuator section 90 can be suppressed.

The thickness of the third electrode layer 73 is greater than the thickness of the second electrode layer 72 (see Figures 4 to 6 and 11). If the central plane M of the piezoelectric layers 41 to 43 in the Z direction is within the piezoelectric layer 42 (see Figure 11), the amount of electrode on the upper side (the side where the first electrode layer 71 and the second electrode layer 72 are arranged) relative to the central plane M will be greater, and warping due to thermal contraction during electrode firing may occur. In this regard, in this configuration, by increasing the thickness of the third electrode layer 73, the volume ratio of the electrodes on the upper and lower sides relative to the central plane M can be balanced, and warping can be suppressed. In addition, when the thickness of the electrode layer is increased, bleeding A (see Figure 12) is more likely to occur, but in this embodiment, the center O2 of the through hole 82 is positioned downstream in the second direction D2 relative to the center O1 of the through hole 81, thereby solving the problem that the through hole 82 cannot be detected accurately due to bleeding A, so that even if the thickness of the third electrode layer 73 is increased to suppress warping, problems due to bleeding A are less likely to occur.

The second electrode layer 72 further has an internal electrode 83 disposed inside the through hole 82 (see Figures 8 and 10). In this case, by detecting the internal electrode 83 instead of the through hole 82, which is prone to bleeding, the detection accuracy is improved and the positioning of the piezoelectric actuator 22 and the flow path unit 21 can be more appropriately performed.

The center O3 of the internal electrode 83 is located downstream of the center O2 of the through hole 82 in the third direction D3 (the printing direction of the screen printing of the second electrode layer 72) (see FIGS. 10 and 11). The possibility that the internal electrode 83 will connect with the bleed (thin portion S2) of the periphery of the through hole 82 is reduced. Therefore, the detection accuracy can be maintained and the positioning of the piezoelectric actuator 22 and the flow path unit 21 can be more appropriately performed. In addition, when the center O3 of the internal electrode 83 and the center O2 of the through hole 82 are in the same position, in order to avoid the connection between the internal electrode 83 and the bleed (thin portion S2) of the periphery of the through hole 82 as described above, it is necessary to enlarge the through hole 82 in order to ensure the distance between the periphery of the through hole 82 and the internal electrode 83. If the through hole 82 is enlarged, the electrical resistance increases (and thus a shortage of charge supply occurs), which may hinder the deformation of the actuator part 90. In this regard, in this configuration, by positioning the center O3 of the internal electrode 83 downstream in the third direction D3 from the center O2 of the through hole 82, the distance between the periphery of the through hole 82 and the internal electrode 83 can be ensured without enlarging the through hole 82. Therefore, there is no need to enlarge the through hole 82 excessively, and the problem of deformation inhibition of the actuator section 90 as described above can be suppressed.

The printing direction (third direction D3) of the screen printing in the formation step of the second electrode layer 72 is the opposite direction to the printing direction (second direction D2) of the screen printing in the formation step of the third electrode layer 73 (see Figures 10 and 11). In the formation step of the second electrode layer 72, the internal electrode 83 arranged inside the through hole 82 is formed so that its center O3 is located downstream of the center O2 of the through hole 82 in the third direction D3. In this case, the internal electrode 83 can be arranged between the peripheral bleeding (thin portion S1) of the through hole 81 and the peripheral bleeding (thin portion S2) of the through hole 82, and near the center O1 of the through hole 81. Furthermore, when screen printing is performed twice in the step of forming the second electrode layer 72, the printing direction of the first screen printing is set to the opposite direction to the printing direction of the screen printing in the step of forming the third electrode layer 73, and the printing direction of the second screen printing is set to the same direction as the printing direction of the screen printing in the step of forming the third electrode layer 73, thereby simplifying the lamination work of the piezoelectric layers 41 to 43. In this case, the first time is generally more accurate than the second time, so the internal electrode 83 is formed in the first time.

The distance (first distance) L1 in the Y direction between the center O1 of the through hole 81 and the center O2 of the through hole 82 is greater than the distance (second distance) L2 in the Y direction between the center O3 of the internal electrode 83 and the center of the through hole 82 (see Figures 10 and 11). Because the third electrode layer 73 in which the through hole 81 is formed is relatively thick, a bleed A (see Figure 12) is likely to occur around the edge of the through hole 81. However, in this configuration, by increasing the first distance L1, the possibility that the through hole 82 will overlap the bleed A (thin portion S1) in the Z direction (first direction D1) is reduced, and the through hole 82 can be detected with high accuracy.

The internal electrode 83 has a circular shape (see FIG. 10). If the internal electrode 83 were rectangular, it would be difficult to detect the center of gravity of the internal electrode 83 from the imaging results. In contrast, in this configuration, the internal electrode 83 has a circular shape, so it is easy to detect the center of gravity of the internal electrode 83 from the imaging results.

The through hole 82 is circular (see FIG. 10). If the through hole 82 is rectangular, it is difficult to detect the center of gravity of the through hole 82 from the imaging results. In contrast, in this configuration, since the through hole 82 is circular, it is easy to detect the center of gravity of the through hole 82 from the imaging results.

Second Embodiment
Next, a piezoelectric actuator 222 according to a second embodiment of the present invention will be described with reference to Figures 14 to 17. The main difference between this embodiment and the first embodiment is the configuration of the through holes 81, 82.

In this embodiment, as shown in FIG. 15, the through holes 81 are notched at one end in the fourth direction D4 along the Y direction in each of the two parts 57b of the high potential connection electrode portion and the two overlapping parts 534 of the low potential electrode. As shown in FIG. 14, the through holes 82 are notched at one end in the fourth direction D4 along the Y direction in each of the two overlapping parts 524 of the high potential electrode and the two end electrodes 56b of the low potential connection electrode portion. Each through hole 82 overlaps with each through hole 81 shown in FIG. 15 in the Z direction. An internal electrode 83 is provided inside each through hole 82.

In addition, in this embodiment, of the multiple branch portions 523 in the first embodiment (Figure 8), the two branch portions 523 at both ends in the Y direction are omitted.

In this embodiment, the printing direction (second direction D2) of the screen printing in the step of forming the third electrode layer including the portion 57b and the overlapping portion 534 is the same as the printing direction (third direction D3) of the screen printing in the step of forming the second electrode layer including the overlapping portion 524 and the end electrode 56b. The second direction D2 and the third direction D3 are opposite to the fourth direction D4 and are directions from one end of the Y direction where the through holes 81 and 82 open to the other end.

As described above, according to this embodiment, the through hole 81 is opened in a notch shape at one end of the portion 57b and the overlapping portion 534 in the fourth direction D4 (see FIG. 15). In this case, by making the printing direction (second direction D2) of the screen printing when forming the through hole 81 the opposite direction to the fourth direction D4, no bleeding occurs on the periphery of the through hole 81 (upstream side of the second direction D2, upstream side of the printing direction of the screen printing) (see FIG. 17). In other words, the portion 57b and the overlapping portion 534 in which the through hole 81 is provided do not have a thin portion S1 (see FIG. 11) formed therein, and are composed only of the thick portion T1. As a result, even if the center O2 of the through hole 82 is not positioned downstream of the center O1 of the through hole 81 in the second direction D2 as in the first embodiment (see FIG. 10), the through hole 82 does not overlap with the bleeding A (thin portion S1) in the Z direction (first direction D1), and the through hole 82 can be detected with high accuracy. Therefore, the piezoelectric actuator 22 and the flow passage unit 21 can be properly positioned.

The through hole 82 is opened in a notch shape at one end of the overlapping portion 524 and the end electrode 56b in the fourth direction D4 (see FIG. 14). In this case, by making the printing direction (third direction D3) of the screen printing when forming the through hole 82 the opposite direction to the fourth direction D4, no bleeding occurs around the periphery of the through hole 82 (upstream side of the third direction D3, upstream side of the printing direction of the screen printing) (see FIG. 17). In other words, the overlapping portion 524 and the end electrode 56b in which the through hole 82 is provided are not formed with the thin part S2 (see FIG. 11), and are composed only of the thick part T2. As a result, there is no obstruction of light transmission due to bleeding of the through holes 81 and 82, and the through hole 82 can be detected with even greater accuracy. In addition, since there is no problem with the internal electrode 83 connecting with the bleeding around the periphery of the through hole 82, there is no need to position the center O3 of the internal electrode 83 downstream in the third direction D3 from the center O2 of the through hole 82 as in the first embodiment (see FIG. 10), and there is no need to make the through hole 82 excessively large to ensure a distance between the periphery of the through hole 82 and the internal electrode 83.

<Modification>
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various design modifications are possible within the scope of the claims.

The shapes of the through holes 81, 82 and the internal electrode 83 are circular in the above-described embodiment (see Figures 11 and 16), but may be any shape (e.g., rectangular, etc.). The shapes of the through holes 81, 82 and the internal electrode 83 may be different from each other (e.g., the through hole 81 may be rectangular, and the through hole 82 and the internal electrode 83 may be circular).

In the first embodiment (see Figures 10 and 11), the printing direction (third direction D3) of the screen printing in the step of forming the second electrode layer 72 is opposite to the printing direction (second direction D2) of the screen printing in the step of forming the third electrode layer 73, but may be the same direction as the printing direction (second direction D2) of the screen printing in the step of forming the third electrode layer 73.

Each electrode layer 71-73 may be formed by a method other than screen printing.

It is not necessary to provide an internal electrode 83 inside the through hole 82.

The thickness of the third electrode layer 73 may be the same as the thickness of the first electrode layer 71 and the second electrode layer 72.

The through-hole 81 is not limited to being provided in the low potential electrode 53, but may be provided, for example, in the end electrode 66a (see FIG. 9).

The second electrode layer 72 in which the through hole 82 is provided is a layer including a high potential electrode 52, but is not limited to this and may be, for example, a layer including a low potential electrode 53 or a driving electrode 51.

The first potential is not limited to being a high potential and the second potential is a low potential, and the opposite may also be true (i.e., the first potential is a low potential and the second potential is a high potential). In this case, the high potential electrode 52 may be located in the bottom layer, and the low potential electrode 53 may be located in the middle layer.

In the embodiment described above (see FIG. 9), the through-hole 81 is provided in the third electrode layer 73, but the through-hole 81 may be provided in the first electrode layer 71. In this case, in the method for manufacturing the head 3 (see FIG. 13), in S21 (imaging step), light is irradiated from the first electrode layer 71 toward the third electrode layer 73 on the piezoelectric actuator 22 to obtain an imaging result.

The number of piezoelectric layers constituting the piezoelectric actuator is three in the above-described embodiment, but may be four or more. For example, in the above-described embodiment (see FIG. 4, etc.), another piezoelectric layer may be disposed between the piezoelectric layer 43 of the piezoelectric actuator 22 and the plate 31 of the flow channel unit 21.

The present invention is not limited to printers, but can also be applied to facsimiles, copiers, multifunction machines, etc. The present invention can also be applied to liquid ejection devices used for purposes other than image recording (for example, liquid ejection devices that eject conductive liquid onto a substrate to form a conductive pattern). Furthermore, the piezoelectric actuator according to the present invention can be applied to any device other than a liquid ejection device.

10 Pressure chamber 15 Nozzle 21 Flow passage unit 22; 222 Piezoelectric actuator 41 Piezoelectric layer (first piezoelectric layer)
42 Piezoelectric layer (second piezoelectric layer)
43 Piezoelectric layer (third piezoelectric layer)
51 Drive electrode 52 High potential electrode (first potential electrode)
53 Low potential electrode (second potential electrode)
71 First electrode layer 72 Second electrode layer 73 Third electrode layer 81 Through hole (first through hole)
82 Through hole (second through hole)
83 Internal electrode T1 Thick part (first thick part)
T2 Thick part (second thick part)
S1 Thin wall part (first thin wall part)
S2 Thin-walled section (second thin-walled section)
O1, O2, O3 center L1 distance (first distance)
L2 Distance (second distance)
D1 First direction D2 Second direction D3 Third direction

Claims (14)

a first piezoelectric layer; a second piezoelectric layer stacked on the first piezoelectric layer in a first direction along a thickness direction of the first piezoelectric layer; a third piezoelectric layer stacked on the first piezoelectric layer and the second piezoelectric layer in the first direction and sandwiching the second piezoelectric layer between the first piezoelectric layer and the third piezoelectric layer; a first electrode layer arranged on a surface of the first piezoelectric layer opposite to the second piezoelectric layer in the first direction; a second electrode layer arranged between the first piezoelectric layer and the second piezoelectric layer in the first direction; and a third electrode layer arranged between the second piezoelectric layer and the third piezoelectric layer in the first direction,
the first electrode layer includes a plurality of drive electrodes to which either a first potential or a second potential different from the first potential is selectively applied;
the second electrode layer includes a first potential electrode held at the first potential;
the third electrode layer includes a second potential electrode held at the second potential;
one of the first electrode layer and the third electrode layer has a first through hole, a first thick portion defining the first through hole, and a first thin portion connected to the first thick portion and having a thickness in the first direction smaller than that of the first thick portion, the first thin portion being disposed on the upstream side in a second direction perpendicular to the first direction within the first through hole;
the second electrode layer has a second through hole overlapping the first through hole in the first direction;
A piezoelectric actuator, wherein a center of the second through hole is located downstream in the second direction with respect to a center of the first through hole. the first potential is a high potential,
2. The piezoelectric actuator according to claim 1, wherein the second potential is a low potential that is lower than the high potential. The piezoelectric actuator according to claim 2, characterized in that the first through-hole is formed in the second potential electrode of the third electrode layer. The piezoelectric actuator of claim 3, characterized in that the thickness of the third electrode layer is greater than the thickness of the second electrode layer. The piezoelectric actuator according to any one of claims 1 to 3, characterized in that the second electrode layer further has an internal electrode disposed inside the second through hole. the second electrode layer has a second thick portion that defines the second through hole, and a second thin portion that is connected to the second thick portion and has a thickness in the first direction smaller than that of the second thick portion, the second thin portion being disposed upstream in the second through hole in a third direction perpendicular to the first direction,
The piezoelectric actuator according to claim 5 , wherein a center of the internal electrode is located downstream in the third direction with respect to a center of the second through hole. The piezoelectric actuator according to claim 6, characterized in that the thickness of one of the first electrode layer and the third electrode layer is greater than the thickness of the second electrode layer. The piezoelectric actuator according to claim 7, characterized in that the first distance in the second direction between the center of the first through hole and the center of the second through hole is greater than the second distance in the second direction between the center of the internal electrode and the center of the second through hole. The piezoelectric actuator according to any one of claims 5 to 8, characterized in that the internal electrode is circular. a first piezoelectric layer; a second piezoelectric layer stacked on the first piezoelectric layer in a first direction along a thickness direction of the first piezoelectric layer; a third piezoelectric layer stacked on the first piezoelectric layer and the second piezoelectric layer in the first direction and sandwiching the second piezoelectric layer between the first piezoelectric layer and the third piezoelectric layer; a first electrode layer arranged on a surface of the first piezoelectric layer opposite to the second piezoelectric layer in the first direction; a second electrode layer arranged between the first piezoelectric layer and the second piezoelectric layer in the first direction; and a third electrode layer arranged between the second piezoelectric layer and the third piezoelectric layer in the first direction,
the first electrode layer includes a plurality of drive electrodes to which either a first potential or a second potential different from the first potential is selectively applied;
the second electrode layer includes a first potential electrode held at the first potential;
the third electrode layer includes a second potential electrode held at the second potential;
one of the first electrode layer and the third electrode layer has a first through hole that opens in a notch shape at one end of the electrode layer in a fourth direction perpendicular to the first direction,
The second electrode layer has a second through hole overlapping the first through hole in the first direction. The piezoelectric actuator according to claim 10, characterized in that the second through hole opens in a notch shape at one end of the second electrode layer in the fourth direction. The piezoelectric actuator according to any one of claims 1 to 11, characterized in that the second through hole is circular. an actuator fabrication step of fabricating a piezoelectric actuator in which a first piezoelectric layer, a second piezoelectric layer, and a third piezoelectric layer are stacked in a first direction along a thickness direction of the first piezoelectric layer;
a bonding step of bonding the piezoelectric actuator to a flow path unit in which a flow path including a plurality of nozzles and a plurality of pressure chambers respectively communicating with the plurality of nozzles is formed,
The actuator fabrication process includes:
a first electrode layer forming step of forming, by screen printing, a first electrode layer including a plurality of driving electrodes to which either a first potential or a second potential different from the first potential is selectively applied, on a surface of the first piezoelectric layer;
a second electrode layer forming step of forming a second electrode layer including a first potential electrode held at the first potential on a surface of the second piezoelectric layer by screen printing;
a third electrode layer forming step of forming a third electrode layer including a second potential electrode held at the second potential on a surface of the third piezoelectric layer by screen printing;
a lamination step of laminating the first piezoelectric layer, the second piezoelectric layer, and the third piezoelectric layer in the first direction such that, after the first electrode layer forming step, the second electrode layer forming step, and the third electrode layer forming step, the first electrode layer is disposed on a surface of the first piezoelectric layer opposite to the second piezoelectric layer in the first direction, the second electrode layer is disposed between the first piezoelectric layer and the second piezoelectric layer in the first direction, and the third electrode layer is disposed between the second piezoelectric layer and the third piezoelectric layer in the first direction,
forming a first through hole in the electrode layer in one of the first electrode layer forming step and the third electrode layer forming step;
In the second electrode layer forming step, a second through hole is formed in the second electrode layer, the second through hole overlapping with the first through hole in the first direction, the center of the second through hole being located downstream of a center of the first through hole in a second direction perpendicular to the first direction and downstream of a printing direction of the screen printing in one of the first electrode layer forming step and the third electrode layer forming step;
The bonding step includes:
an imaging step of irradiating the piezoelectric actuator with light from one of the first electrode layer and the third electrode layer, in which the first through hole is formed, to the other, and acquiring an imaging result;
and a positioning step of positioning the piezoelectric actuator and the flow path unit based on the imaging result. a printing direction of the screen printing in the second electrode layer forming step is a third direction that is perpendicular to the first direction and opposite to the second direction;
14. A method for manufacturing a liquid ejection head as described in claim 13, characterized in that, in the second electrode layer formation step, an internal electrode to be placed inside the second through hole is formed so that its center is located downstream in the third direction with respect to the center of the second through hole.

Images