JP2021053853A - Liquid discharge head, liquid discharge device, and piezoelectric device - Google Patents

Abstract

To suppress crack at the position of an end of a second electrode in a piezoelectric element.SOLUTION: A liquid discharge head includes: a pressure chamber which is communicated with a nozzle for discharging liquid; a diaphragm which constitutes a part of a wall surface of the pressure chamber; a first electrode which is provided on a surface in a first direction in the diaphragm when a direction from the pressure chamber to the diaphragm is defined as the first direction; a piezoelectric layer which is provided on the surface in the first direction in the first electrode and includes a first region and a second region adjacent to the first region in plan view; a second electrode which is provided in the first region; a first layer which is provided in the second region and comes into contact with a side face of the second electrode; and a second layer which covers the first layer and overlaps the first region and the second region in plan view. A relative dielectric constant of the first layer is larger than that of the second layer. Young modulus of the second layer is smaller than that of the first layer.SELECTED DRAWING: Figure 8

Description

The present invention relates to a liquid discharge head, a liquid discharge device and a piezoelectric device.

For example, a liquid ejection head that ejects a liquid such as ink from a nozzle has been conventionally proposed. Patent Document 1 discloses a liquid discharge head including a piezoelectric element that fluctuates the pressure in a pressure chamber communicating with a nozzle. The piezoelectric element is composed of a laminate of a lower electrode, a piezoelectric layer, and an upper electrode.

JP-A-2017-74798

In the configuration of Patent Document 1, the electric field is concentrated at the position of the end of the upper electrode in the piezoelectric layer, and the stress of the piezoelectric layer is locally increased. When the stress of the piezoelectric layer increases locally, the occurrence of cracks becomes a problem.

In order to solve the above problems, the liquid discharge head according to a preferred embodiment of the present invention includes a pressure chamber communicating with a nozzle for discharging liquid, a vibrating plate forming a part of a wall surface of the pressure chamber, and the above. When the direction from the pressure chamber to the vibrating plate is the first direction, the first electrode provided on the surface of the vibrating plate in the first direction and the surface of the first electrode in the first direction A piezoelectric layer provided and including a first region and a second region adjacent to the first region in a plan view, a second electrode provided in the first region, and a second region provided in the second region. A first layer that contacts the side surfaces of the two electrodes and a second layer that covers the first layer and overlaps the first region and the second region in the plan view are provided, and the relative permittivity of the first layer is provided. The ratio is larger than the relative permittivity of the second layer, and the Young ratio of the second layer is smaller than the Young ratio of the first layer. Further, the present invention can be conceived as a liquid discharge device including the liquid discharge head and a control unit for controlling the liquid discharge head.

The piezoelectric device according to a preferred embodiment of the present invention is provided with an elastically deformable vibrating plate, a first electrode provided on the surface of the vibrating plate, and a first region and the said one provided on the surface of the first electrode. A first region provided in the second region, which is in contact with a piezoelectric layer whose surface includes a second region adjacent to the first region, a second electrode provided in the first region, and a side surface of the second electrode. A layer and a second layer that covers the first layer and overlaps the first region and the second region in a plan view are provided, and the relative permittivity of the second layer is the relative dielectric constant of the first layer. It is larger than the rate, and the young rate of the second layer is smaller than the young rate of the first layer.

It is a block diagram which illustrates the structure of the liquid discharge device which concerns on 1st Embodiment. It is an exploded perspective view of the liquid discharge head. It is sectional drawing of the liquid discharge head. It is a top view of the piezoelectric element and its vicinity. It is sectional drawing of the VV line in FIG. It is sectional drawing of the VI-VI line in FIG. It is a top view of the piezoelectric layer. It is an enlarged cross-sectional view of a part of a piezoelectric element. It is an enlarged sectional view of a part of the piezoelectric element which concerns on 2nd Embodiment. It is an enlarged cross-sectional view of a part of the piezoelectric element which concerns on a modification. It is an enlarged cross-sectional view of a part of the piezoelectric element which concerns on a modification. It is an enlarged cross-sectional view of a part of the piezoelectric element which concerns on a modification. It is an enlarged cross-sectional view of a part of the piezoelectric element which concerns on a modification.

A. 1st Embodiment FIG. 1 is a block diagram which illustrates the liquid discharge device 100 which concerns on 1st Embodiment. The liquid ejection device 100 is an inkjet printing apparatus that ejects ink, which is an example of a liquid, onto the medium 12. The medium 12 is typically printing paper, but a printing target of any material such as a resin film or cloth is used as the medium 12. As illustrated in FIG. 1, a liquid container 14 for storing ink is installed in the liquid ejection device 100. For example, a cartridge that can be attached to and detached from the liquid ejection device 100, a bag-shaped ink pack made of a flexible film, or an ink tank that can be refilled with ink is used as the liquid container 14.

As illustrated in FIG. 1, the liquid discharge device 100 includes a control unit 20, a transfer mechanism 22, a moving mechanism 24, and a liquid discharge head 26. The control unit 20 includes one or a plurality of processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and one or a plurality of storage circuits such as a semiconductor memory, and each element of the liquid discharge device 100. Is controlled comprehensively. The control unit 20 is an example of a “control unit”. The transport mechanism 22 transports the medium 12 in the Y-axis direction under the control of the control unit 20.

The moving mechanism 24 reciprocates the liquid discharge head 26 along the X axis under the control of the control unit 20. The X-axis intersects the Y-axis along the direction in which the medium 12 is conveyed. Typically, the X and Y axes are orthogonal. The moving mechanism 24 of the first embodiment includes a substantially box-shaped transport body 242 that accommodates the liquid discharge head 26, and a transport belt 244 to which the transport body 242 is fixed. A configuration in which a plurality of liquid discharge heads 26 are mounted on the transport body 242, or a configuration in which the liquid container 14 is mounted on the transport body 242 together with the liquid discharge head 26 can also be adopted.

The liquid ejection head 26 ejects the ink supplied from the liquid container 14 from a plurality of nozzles to the medium 12 under the control of the control unit 20. The ink is ejected along the Z axis. The axis perpendicular to the XY plane is the Z axis. That is, the X-axis and the Y-axis are orthogonal to the Z-axis. An image is formed on the surface of the medium 12 by each liquid ejection head 26 ejecting ink to the medium 12 in parallel with the conveying of the medium 12 by the conveying mechanism 22 and the repetitive reciprocation of the conveying body 242.

FIG. 2 is an exploded perspective view of the liquid discharge head 26. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 3 is a cross-sectional view of a cross section parallel to the XZ plane. As illustrated in FIG. 2, the liquid discharge head 26 includes a plurality of nozzles N arranged along the Y axis. The plurality of nozzles N of the first embodiment are divided into a first row La and a second row Lb arranged side by side at intervals along the X axis. Each of the first row La and the second row Lb is a set of a plurality of nozzles N linearly arranged along the Y axis. As can be understood from FIG. 3, in the liquid discharge head 26 of the first embodiment, the elements related to each nozzle N in the first row La and the elements related to each nozzle N in the second row Lb are substantially plane-symmetrical. It is an arranged structure. In the following description, the elements corresponding to the first column La will be mainly described, and the description of the elements corresponding to the second column Lb will be omitted as appropriate.

As illustrated in FIGS. 2 and 3, the liquid discharge head 26 includes a flow path structure 30, a plurality of piezoelectric elements 34, a sealing body 35, a housing portion 36, and a wiring board 51. The flow path structure 30 is a structure in which a flow path for supplying ink to each of the plurality of nozzles N is formed inside. The flow path structure 30 is composed of a flow path substrate 31, a pressure chamber substrate 32, a diaphragm 33, a nozzle plate 41, and a vibration absorbing body 42, and is laminated along the Z-axis direction. Each member constituting the flow path structure 30 is a long plate-shaped member along the Y axis. The pressure chamber substrate 32 and the housing portion 36 are installed on the surface of the flow path substrate 31 in the positive direction of the Z axis. On the other hand, the nozzle plate 41 and the vibration absorbing body 42 are installed on the surface of the flow path substrate 31 in the negative direction of the Z axis. For example, each member is fixed by an adhesive.

The nozzle plate 41 is a plate-shaped member in which a plurality of nozzles N are formed. Each of the plurality of nozzles N is a circular through hole for ejecting ink. For example, the nozzle plate 41 is manufactured by processing a silicon (Si) single crystal substrate using semiconductor manufacturing techniques such as photolithography and etching. However, a known material or manufacturing method can be arbitrarily adopted for manufacturing the nozzle plate 41.

As illustrated in FIGS. 2 and 3, the flow path substrate 31 is formed with a space Ra, a plurality of supply flow paths 312, a plurality of communication flow paths 314, and a relay liquid chamber 316. The space Ra is an opening formed in a long shape along the Y axis. Each of the supply flow path 312 and the communication flow path 314 is a through hole formed for each nozzle N. The relay liquid chamber 316 is a space formed in a long shape along the Y axis over a plurality of nozzles N, and allows the space Ra and the plurality of supply flow paths 312 to communicate with each other. In a plan view from the Z-axis direction, the communication flow path 314 and the nozzle N overlap.

As illustrated in FIGS. 2 and 3, a plurality of pressure chambers C are formed on the pressure chamber substrate 32. The pressure chamber C is located between the nozzle plate 41 and the diaphragm 33, and is a space formed by the wall surface 320 of the pressure chamber substrate 32. The pressure chamber C and the diaphragm 33 are arranged along the Z-axis direction. The diaphragm 33 is arranged in the positive direction of the Z axis when viewed from the pressure chamber C. The positive direction of the Z axis is an example of the "first direction". The direction from the pressure chamber C to the diaphragm 33 can be paraphrased as the first direction. The pressure chamber C is formed for each nozzle N. The pressure chamber C is a long space along the X axis in a plan view. The plurality of pressure chambers C are arranged along the Y axis. The flow path substrate 31 and the pressure chamber substrate 32 are manufactured by processing a single crystal substrate of silicon by using, for example, a semiconductor manufacturing technique, similarly to the nozzle plate 41 described above. However, known materials and manufacturing methods can be arbitrarily adopted for manufacturing the flow path substrate 31 and the pressure chamber substrate 32.

As illustrated in FIG. 3, an elastically deformable diaphragm 33 is arranged on the surface of the pressure chamber C. The diaphragm 33 comes into contact with the surface of the pressure chamber substrate 32 opposite to the flow path substrate 31. The diaphragm 33 is a plate-shaped member formed in a long rectangular shape along the Y-axis in a plan view. The upper surface of the pressure chamber C is composed of the diaphragm 33. The thickness direction of the diaphragm 33 is parallel to the Z axis. As illustrated in FIGS. 2 and 3, the pressure chamber C communicates with the communication flow path 314 and the supply flow path 312. Therefore, the pressure chamber C communicates with the nozzle N via the communication flow path 314 and communicates with the space Ra via the supply flow path 312 and the relay liquid chamber 316.

As illustrated in FIG. 3, a piezoelectric element 34 is formed for each pressure chamber C on the surface of the diaphragm 33 opposite to the pressure chamber C. The piezoelectric element 34 is a long passive element along the X axis in a plan view. The piezoelectric element 34 is also a drive element that is driven by applying a drive signal.

The housing portion 36 of FIG. 3 is a case for storing ink supplied to a plurality of pressure chambers C, and is formed by, for example, injection molding of a resin material. A space Rb and a supply port 361 are formed in the housing portion 36. The supply port 361 is a conduit for ink to be supplied from the liquid container 14, and communicates with the space Rb. The space Rb of the housing portion 36 and the space Ra of the flow path substrate 31 communicate with each other. The space composed of the space Ra and the space Rb functions as a liquid storage chamber R for storing ink supplied to the plurality of pressure chambers C. The ink supplied from the liquid container 14 and passing through the supply port 361 is stored in the liquid storage chamber R. The ink stored in the liquid storage chamber R branches from the relay liquid chamber 316 to each supply flow path 312, and is supplied and filled in parallel to the plurality of pressure chambers C. The vibration absorber 42 is a flexible film that constitutes the wall surface of the liquid storage chamber R, and absorbs pressure fluctuations of ink in the liquid storage chamber R.

The sealing body 35 is a structure that protects a plurality of piezoelectric elements 34 and reinforces the mechanical strength of the pressure chamber substrate 32 and the diaphragm 33, and is fixed to the surface of the diaphragm 33 with, for example, an adhesive. A plurality of piezoelectric elements 34 are housed inside a recess formed in the sealing body 35 on a surface facing the diaphragm 33. Further, a wiring board 51 is joined to the surface of the diaphragm 33. The wiring board 51 is a mounting component on which a plurality of wirings for electrically connecting the control unit 20 and the liquid discharge head 26 are formed. For example, a flexible wiring board 51 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably adopted. A drive signal and a reference voltage for driving the piezoelectric element 34 are supplied from the wiring board 51 to each piezoelectric element 34.

FIG. 4 is a plan view of the piezoelectric element 34 and its vicinity. In FIG. 4, dots are added to the second electrode 342, which will be described later, for convenience. Further, FIG. 5 is a cross-sectional view taken along the line VV in FIG. FIG. 5 is a cross-sectional view of a cross section parallel to the XZ plane. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. FIG. 6 is a cross-sectional view of a cross section parallel to the YY plane.

The diaphragm 33 illustrated in FIGS. 4 to 6 vibrates by driving the piezoelectric element 34 as described above. As illustrated in FIGS. 5 and 6, the diaphragm 33 is composed of a laminated body including the first vibrating layer 331 and the second vibrating layer 332. The first vibrating layer 331 comes into contact with the pressure chamber substrate 32. The second vibrating layer 332 is located opposite to the pressure chamber substrate 32 with respect to the first vibrating layer 331. The first vibrating layer 331 is an elastic film formed of an elastic material such as _{silicon dioxide (SiO 2).} The second vibrating layer 332 is an insulating film formed of an insulating material such as _{zirconium dioxide (ZrO 2).} Each of the first vibrating layer 331 and the second vibrating layer 332 is formed by a known film forming technique such as thermal oxidation or sputtering. By selectively removing a part of the plate-shaped member having a predetermined plate thickness in the plate thickness direction in the region corresponding to the pressure chamber C, the pressure chamber substrate 32 and a part or all of the diaphragm 33 can be removed. It is also possible to form them integrally.

As illustrated in FIGS. 5 and 6, the piezoelectric element 34 is roughly a structure in which the first electrode 341, the piezoelectric layer 343, and the second electrode 342 are laminated in the above order from the diaphragm 33 side. Is. The first electrode 341 and the second electrode 342 are insulated from each other. The potentials of the first electrode 341 and the second electrode 342 are different. The direction of the Z axis corresponds to the direction in which the first electrode 341, the piezoelectric layer 343, and the second electrode 342 are laminated.

The first electrode 341 is provided on the surface of the diaphragm 33 in the positive direction of the Z axis. The first electrode 341 is an individual electrode formed so as to be separated from each other for each piezoelectric element 34. A drive signal whose voltage fluctuates is applied to the first electrode 341. The first electrode 341 has a long shape along the X axis. The plurality of first electrodes 341 are arranged along the Y axis at intervals from each other. The first electrode 341 is formed of a conductive material such as platinum (Pt) or iridium (Ir). The expression "element B is provided on the surface of element A" means that element B is provided directly on the surface of element A and that another element is interposed between element A and element B. It includes both that the element B is indirectly provided on the surface of the element A in the state of being in the state.

As illustrated in FIG. 5, the piezoelectric layer 343 is provided on the surface of the first electrode 341 in the positive direction of the Z axis and comes into contact with the first electrode 341. The piezoelectric layer 343 has a first surface 301 in contact with the first electrode 341 and a second surface 302 opposite to the first surface 301. As illustrated in FIG. 4, the piezoelectric layer 343 is a strip-shaped dielectric film continuous along the Y axis across a plurality of piezoelectric elements 34. Further, the piezoelectric layer 343 is formed of a known piezoelectric material such as lead zirconate titanate (Pb (Zr, Ti) O _{3) or ceramic.} As illustrated in FIG. 4, a notch G along the X axis is formed in the region of the piezoelectric layer 343 corresponding to the gap between the pressure chambers C adjacent to each other. The notch G is an opening that penetrates the piezoelectric layer 343. By forming the notch G, each piezoelectric element 34 is individually deformed for each pressure chamber C, and the propagation of vibration between the piezoelectric elements 34 is suppressed. A bottomed hole in which a part of the piezoelectric layer 343 in the thickness direction is removed may be formed as a notch G.

As illustrated in FIGS. 5 and 6, the second electrode 342 is provided on the surface of the piezoelectric layer 343 and comes into contact with the second surface 302 of the piezoelectric layer 343. As illustrated in FIG. 4, the second electrode 342 is a band-shaped common electrode extending along the Y axis so as to be continuous over the plurality of piezoelectric elements 34. A predetermined reference voltage is applied to the second electrode 342. The reference voltage is a constant voltage, for example set to a voltage higher than the ground voltage. That is, for example, a holding signal having a constant voltage is applied to the second electrode 342. A voltage corresponding to the difference between the reference voltage applied to the second electrode 342 and the drive signal supplied to the first electrode 341 is applied to the piezoelectric layer 343. The drive signal corresponds to the discharge amount. The holding signal is constant regardless of the discharge amount and does not fluctuate. A ground voltage may be applied to the second electrode 342. Further, the second electrode 342 is formed of a low resistance conductive material such as platinum (Pt) or iridium (Ir).

When a voltage is applied between the first electrode 341 and the second electrode 342, the piezoelectric layer 343 is deformed, so that the piezoelectric element 34 generates energy for bending and deforming the vibrating plate 33. The pressure in the pressure chamber C changes as the diaphragm 33 vibrates due to the energy generated by the piezoelectric element 34, and the ink in the pressure chamber C is ejected from the nozzle N shown in FIG.

As illustrated in FIGS. 4 and 5, the first wiring 37 is electrically connected to the first electrode 341. One first wiring 37 is electrically connected to one first electrode 341. The first wiring 37 is a lead wiring to which a drive signal is supplied from a drive circuit (not shown) mounted on the wiring board 51 shown in FIG. The first wiring 37 applies a drive signal to the first electrode 341. As illustrated in FIG. 4, the plan-view shape of the first wiring 37 is a longitudinal shape extending along the X-axis. Further, as illustrated in FIG. 5, a part of the first wiring 37 is located on the surface of the piezoelectric layer 343 and comes into contact with the second surface 302 of the piezoelectric layer 343. That is, the first wiring 37 has a portion arranged on the second surface 302.

As illustrated in FIG. 5, the first wiring 37 includes a first adhesion layer 373 and a first wiring layer 374. The first adhesion layer 373 comes into contact with the first electrode 341. The first adhesion layer 373 enhances the adhesion of the first wiring 37 to the first electrode 341. The first adhesion layer 373 is formed of a conductive material having a lower resistance than that of the first electrode 341. For example, the first adhesion layer 373 is formed of a conductive material such as nichrome (NiCr). The first wiring layer 374 covers the first adhesion layer 373. The first wiring layer 374 enhances the conductivity of the first wiring 37. The first wiring layer 374 is formed of a conductive material having a lower resistance than that of the first electrode 341. For example, the first wiring layer 374 is formed of a conductive material such as gold (Au). An electrode layer 370 is arranged between the first adhesion layer 373 and the first electrode 341. The electrode layer 370 is formed in the same process as the second electrode 342 described later. The electrode layer 370 is made of the same material as the second electrode 342. The electrode layer 370 may be regarded as a part of the first wiring 37.

As illustrated in FIGS. 4 and 5, a second wiring 38 electrically connected to the second electrode 342 is formed on the surface of the second electrode 342. A reference voltage is supplied to the second wiring 38 from the control unit 20 shown in FIG. 1 via the wiring board 51 shown in FIG. The second wiring 38 applies a reference voltage to the second electrode 342. As illustrated in FIG. 5, the second wiring 38 is located on the surface of the piezoelectric layer 343 and comes into contact with the surface of the second electrode 342 opposite to the piezoelectric layer 343.

As illustrated in FIG. 4, the second wiring 38 has a strip-shaped first conductive layer 381 extending along the Y-axis and a strip-shaped second conductive layer 382 extending along the Y-axis. The first conductive layer 381 and the second conductive layer 382 are arranged at predetermined intervals along the X axis. The first conductive layer 381 is located between the first wiring 37 and the second conductive layer 382 in a plan view. By providing the first conductive layer 381 and the second conductive layer 382, the voltage drop of the reference voltage in the second electrode 342 is suppressed. Further, the first conductive layer 381 and the second conductive layer 382 also function as weights for suppressing the vibration of the diaphragm 33.

As illustrated in FIG. 5, the second wiring 38 includes a second adhesion layer 383 and a second wiring layer 384. The second adhesion layer 383 comes into contact with the second electrode 342. The second adhesion layer 383 enhances the adhesion of the second wiring 38 to the second electrode 342. The second adhesion layer 383 is formed of a conductive material having a lower resistance than the second electrode 342. For example, the second adhesion layer 383 is formed of a conductive material such as nichrome (NiCr). The second wiring layer 384 covers the second adhesion layer 383. The second wiring layer 384 enhances the conductivity of the second wiring 38. The second wiring layer 384 is formed of a conductive material having a lower resistance than the second electrode 342. For example, the second wiring layer 384 is formed of a conductive material such as gold (Au).

The first wiring 37 and the second wiring 38 described above may be formed of different materials, but are preferably formed of the same material. By being formed of the same material, the first wiring 37 and the second wiring 38 can be formed in the same process.

FIG. 7 is a plan view of the piezoelectric layer 343. FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG. As illustrated in FIGS. 7 and 8, the second surface 302 of the piezoelectric layer 343 includes a first region E1 and a second region E2. The first region E1 and the second region E2 are adjacent to each other. The first region E1 is a region of the second surface 302 where the second electrode 342 is provided. That is, the first region E1 and the second electrode 342 overlap in a plan view. On the other hand, the second region E2 is a region of the second surface 302 in which the second electrode 342 is not formed. Specifically, the second region E2 is a region between the first region E1 and a region in which a plurality of first wirings 37 are formed. The region between the peripheral edge of the first region E1 and the straight line M passing through the end on the second electrode 342 side in each first wiring 37 corresponds to the second region E2.

As illustrated in FIGS. 7 and 8, the liquid discharge head 26 includes a protective layer 70. The protective layer 70 functions as an adhesive for joining the sealing bodies 35. Further, the protective layer 70 suppresses excessive displacement at the position of the end portion of the second electrode 342 of the diaphragm 33, thereby suppressing peeling of the second electrode 342 and cracks generated in the piezoelectric layer 343. .. A protective layer 70 is formed so as to cover the second surface 302, the second electrode 342, the first wiring 37, and the second wiring 38.

Specifically, the protective layer 70 includes a first layer 71 and a second layer 72. The first layer 71 covers the end portion of the second electrode 342. Specifically, the first layer 71 is provided in the second region E2 and comes into contact with the second electrode 342. The first layer 71 comes into contact with the side surface W of the second electrode 342. In the first embodiment, the first layer 71 is formed over the entire second region E2. For example, the film thickness of the first layer 71 and the film thickness of the second electrode 342 are substantially the same. The film thickness is the length in the Z-axis direction. The first layer 71 is formed so as to fill the gap between the second electrode 342 and the first wiring 37.

The second layer 72 is provided on the surface of the first layer 71. Specifically, the second layer 72 covers the first layer 71 and overlaps the first region E1 and the second region E2 in a plan view. The second layer 72 does not have to overlap the entire first region E1 and the entire second region E2, and may at least overlap a part of the first region E1 and a part of the second region E2. .. In the first embodiment, the second layer 72 is formed so as to cover the first layer 71, the second electrode 342, the first wiring 37, and the second wiring 38.

FIG. 8 shows the film thickness H1 of the first layer 71 and the film thickness H2 of the second layer 72. The film thickness H1 of the first layer 71 is, for example, the maximum value in the film thickness of the first layer 71 on the second region E2. The film thickness H2 of the second layer 72 is, for example, the maximum value in the film thickness of the portion of the second layer 72 that is laminated on the first layer 71. The film thickness H2 of the second layer 72 is larger than the film thickness H1 of the first layer 71. However, the film thickness H2 of the second layer 72 may be smaller than the film thickness H1 of the first layer 71.

The relative permittivity of the first layer 71 is larger than the relative permittivity of the second layer 72. Further, the Young's modulus of the second layer 72 is smaller than the Young's modulus of the first layer 71. The coefficient of linear expansion of the first layer 71 is larger than the coefficient of linear expansion of the second layer 72. However, the coefficient of linear expansion of the first layer 71 may be smaller than the coefficient of linear expansion of the second layer 72.

The first layer 71 and the second layer 72 are made of different materials. The first layer 71 is formed of the material A, and the second layer 72 is formed of the material B. Material A is, for example, an insulating material such as tantalum oxide (TaOx), silicon oxide (SiOx), silicon nitride (SiNx), aluminum oxide (AlOx), hafnium oxide (HfOx), or silicon carbide (SiCx). In the first embodiment, tantalum oxide is exemplified as the material A. The relative permittivity of tantalum oxide is about 20 to 30. The second layer 72 is formed of, for example, an insulating resin material. For example, an adhesive such as an epoxy resin is exemplified as the material B. The sealing body 35 is bonded to the surface of the second layer 72.

For example, in the configuration in which the liquid discharge head 26 does not include the protective layer 70, the electric field is concentrated at the position of the end portion of the second electrode 342 in the piezoelectric layer 343, and the stress is locally increased. When the stress locally increases in the piezoelectric layer 343, cracks occur in the piezoelectric layer 343. When a crack occurs, the first electrode 341 and the second electrode 342 become electrically conductive with each other due to the moisture entering the crack, and a current may flow between the two electrodes to cause burnout. On the other hand, according to the configuration of the first embodiment, since the first layer 71 formed of the material A is provided so as to be in contact with the side surface W of the second electrode 342, the second electrode 342 in the piezoelectric layer 343 is provided. The electric field generated at the end of the first layer 71 is also dispersed. Therefore, it is possible to suppress the concentration of the electric field at the position of the end portion of the second electrode 342 in the piezoelectric layer 343. That is, it is possible to suppress the occurrence of cracks in the piezoelectric layer 343.

Further, in the configuration in which the entire protective layer 70 is formed only of the material A, the electric field generated at the position of the end of the second electrode 342 is dispersed in the protective layer 70, but the Young's modulus of the material A is that of the material B. Since it is larger than Young's modulus, there is a problem that the displacement of the diaphragm 33 cannot be excessively suppressed and the discharge amount cannot be secured. On the other hand, in the configuration in which the entire protective layer 70 is formed only of the material B, the displacement of the diaphragm 33 is not excessively suppressed, but the relative permittivity of the material B is higher than the relative permittivity of the material A. Since it is small, there is a problem that the electric field generated at the end of the second electrode 342 is difficult to be dispersed in the protective layer 70. On the other hand, in the first embodiment, since the first layer 71 formed of the material A, the second layer 72 formed of the material B, and the protective layer 70 are included, the displacement of the diaphragm 33 is excessively suppressed. Instead, the electric field generated at the position of the end of the second electrode 342 can be dispersed.

Since the film thickness H2 of the second layer 72 is larger than the film thickness H1 of the first layer 71, excessive displacement of the diaphragm 33 can be efficiently suppressed. Since the coefficient of linear expansion of the first layer 71 is smaller than the coefficient of linear expansion of the second layer 72, even when the piezoelectric layer 343 is formed of a material having a small coefficient of linear expansion, the piezoelectric layer 343 and the first layer 71 The thermal stress between can be reduced. Therefore, it is possible to prevent the piezoelectric layer 343 and the first layer 71 from peeling off. In the first embodiment, since the first layer 71 is formed of tantalum oxide, the relative permittivity of the first layer 71 can be increased as compared with the case where the first layer 71 is formed of another material.

B. Second Embodiment The second embodiment will be described. For the elements having the same functions as those of the first embodiment in each of the following examples, the reference numerals used in the description of the first embodiment will be diverted and detailed description of each will be omitted as appropriate.

FIG. 9 is a cross-sectional view of the piezoelectric layer 343 according to the second embodiment. As illustrated in FIG. 9, in the liquid discharge head 26 of the second embodiment, the position of the first region E1 and the position of the second region E2 are different in the direction of the Z axis. The direction of the Z axis corresponds to the direction in which the first electrode 341, the piezoelectric layer 343, and the second electrode 342 are laminated. FIG. 9 shows the distance D1 between the first region E1 and the first electrode 341 and the distance D2 between the second region E2 and the first electrode 341. The distance D1 is, for example, the shortest distance from the surface of the first electrode 341 to the first region E1. The distance D2 is, for example, the shortest distance from the surface of the first electrode 341 to the second region E2. In the second embodiment, the distance D2 is smaller than the distance D1 in the Z-axis direction. That is, it can be said that a depression is formed in the portion of the second region E2 of the piezoelectric layer 343. The film thickness at the position in the second region E2 of the piezoelectric layer 343 is smaller than the film thickness at the position in the first region E1 of the piezoelectric layer 343.

The first layer 71 is provided in the second region E2 and comes into contact with the side surface W of the second electrode 342, as in the first embodiment. Specifically, the first layer 71 is formed so as to come into contact with the side surface W of the second electrode 342 and fill the recess formed in the piezoelectric layer 343. Therefore, as compared with the configuration in which the position of the first region E1 and the position of the second region E2 are the same, the piezoelectric layer 343 and the piezoelectric layer 343 are located at the position of the end portion of the second electrode 342 of the piezoelectric layer 343. The area in contact with the 1st layer 71 becomes large. The second layer 72 covers the first layer 71 and overlaps the first region E1 and the second region E2 in a plan view, as in the first embodiment. Similar to the first embodiment, the first layer 71 is formed of the material A and the second layer 72 is formed of the material B.

The same effect as that of the first embodiment is realized in the second embodiment. In the second embodiment, since the distance D2 between the second region E2 and the first electrode 341 is shorter than the distance D1 between the first region E1 and the first electrode 341 in the Z-axis direction, the piezoelectric material At the position of the end portion of the second electrode 342 of the layer 343, the region where the piezoelectric layer 343 and the first layer 71 come into contact with each other becomes large. Therefore, the effect that the electric field generated at the end of the second electrode 342 in the piezoelectric layer 343 can be dispersed in the first layer 71 is remarkable.

C. Modifications The embodiments illustrated above can be variously modified. Specific embodiments that can be applied to the above-described embodiments are illustrated below. Two or more embodiments arbitrarily selected from the following examples can be appropriately merged to the extent that they do not contradict each other.

(1) In each of the above-mentioned forms, for example, the protective layer 70 may include a layer different from the first layer 71 and the second layer 72. For example, another layer may be located between the first layer 71 and the second layer 72.

(2) In each of the above-mentioned forms, the region forming the second layer 72 is arbitrary. As illustrated in FIG. 10, it is not essential that the protective layer 70 covers the second wiring 38. Further, as illustrated in FIG. 11, the entire first layer 71 may not be covered with the second layer 72. As long as at least the second layer 72 overlaps a part of the first region E1 and a part of the second region E2 in a plan view, the region where the second layer 72 is formed is arbitrary.

(3) In each of the above-described modes, as illustrated in FIG. 12, the first layer 71 may be formed so as to overlap the first region E1 in a plan view. Specifically, the first layer 71 is formed so as to cover the surface of the second electrode 342 in the first region E1 and the surface of the second region E2. Further, as illustrated in FIG. 13, the first layer 71 may not be formed on the entire second region E2. As understood from the above description, if the first layer 71 is formed so as to come into contact with the side surface W of the second electrode 342 and the second region E2, the region where the first layer 71 is formed is arbitrary. is there.

(4) In each of the above-described embodiments, a conductive layer having a higher conductivity than the piezoelectric layer 343 may be provided on the surface of the second region E2. That is, the first layer 71 is provided on the surface of the conductive layer. For example, when the second electrode 342 is formed on the surface of the piezoelectric layer 343 by dry etching, a conductive layer is formed on the surface of the second region E2 of the piezoelectric layer 343. According to the above configuration, the effect that the electric field generated at the position of the end of the second electrode 342 in the piezoelectric layer 343 can be dispersed in the first layer 71 is remarkable.

(5) In each of the above-described embodiments, all of the second wiring 38 is located on the surface of the piezoelectric layer 343, but if at least a part of the second wiring 38 is located on the surface of the piezoelectric layer 343. Good. In each embodiment, a part of the first wiring 37 is located on the surface of the piezoelectric layer 343, but all of the second wiring 38 may be located on the surface of the piezoelectric layer 343.

(6) In each of the above-described embodiments, the insulating protective layer 70 is arranged between the first wiring 37 and the second wiring 38, but the insulating protective layer 70 is arranged between the first wiring 37 and the second wiring 38. , The protective layer 70 may not be arranged. For example, there may be a space between the first wiring 37 and the second wiring 38.

(7) In each of the above-described embodiments, the diaphragm 33 includes a first vibrating layer 331 and a second vibrating layer 332, but the vibrating plate 33 may omit, for example, the second vibrating layer 332.

(8) In each of the above-described embodiments, the first electrode 341 of the piezoelectric element 34 is used as an individual electrode and the second electrode 342 is used as a common electrode. However, the first electrode 341 may be used as a common electrode and the second electrode 342 may be used as an individual electrode. .. Further, both the first electrode 341 and the second electrode 342 may be used as individual electrodes. Further, in each embodiment, the first electrode 341 is located below the piezoelectric layer 343, the second electrode 342 is located on the surface of the piezoelectric layer 343, but the second electrode 342 is located below the piezoelectric layer 343. The first electrode 341 may be located on the surface of the piezoelectric layer 343.

(9) In each of the above-described embodiments, the piezoelectric element 34 is a structure in which the first electrode 341, the piezoelectric layer 343, and the second electrode 342 are laminated, but between the first electrode 341 and the piezoelectric layer 343. May be intervened with other elements to the extent that the function as the piezoelectric element 34 is not impaired. Similarly, another element may be interposed between the second electrode 342 and the piezoelectric layer 343.

(10) In each of the above-described embodiments, the diaphragm 33, the first electrode 341, the second electrode 342, and the piezoelectric layer 343 correspond to a piezoelectric device.

(11) In each of the above-described embodiments, the serial type liquid discharge device 100 for reciprocating the transport body 242 on which the liquid discharge head 26 is mounted is illustrated, but the line type liquid in which a plurality of nozzles N are distributed over the entire width of the medium 12 is illustrated. The present invention can also be applied to a discharge device.

(12) The liquid discharge device 100 of each form described above can be adopted in various devices such as a facsimile machine and a copier, in addition to a device dedicated to printing. However, the application of the liquid discharge device of the present invention is not limited to printing. For example, a liquid discharge device that discharges a solution of a coloring material is used as a manufacturing device for forming a color filter of a display device such as a liquid crystal display panel. Further, a liquid discharge device that discharges a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Further, a liquid discharge device that discharges a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip.

(13) The present invention is intended for a piezoelectric device, and can be applied to a piezoelectric device other than a liquid discharge head. Examples of electronic devices include ultrasonic devices, motors, pressure sensors, pyroelectric elements and the like. In addition, finished products using these electronic devices, for example, a liquid discharge device using the head, an ultrasonic sensor using the ultrasonic device, a gyro sensor using the piezoelectric sensor, a pressure sensor, and the like are also piezoelectric. Included in the device.

100 ... liquid discharge device, 12 ... medium, 14 ... liquid container, 20 ... control unit, 22 ... transfer mechanism, 24 ... movement mechanism, 242 ... transfer body, 244 ... transfer belt, 26 ... liquid discharge head, 30 ... flow path Structure, 301 ... 1st surface, 302 ... 2nd surface, 31 ... Flow path substrate, 312 ... Supply flow path, 314 ... Communication flow path, 316 ... Relay liquid chamber, 32 ... Pressure chamber substrate, 320 ... Wall surface, 33 ... Vibrating plate, 331 ... 1st vibrating layer, 332 ... 2nd vibrating layer, 34 ... piezoelectric element, 341 ... 1st electrode, 342 ... 2nd electrode, 343 ... piezoelectric layer, 35 ... encapsulant, 36 ... Body, 361 ... Supply port, 37 ... 1st wiring, 370 ... Electrode layer, 373 ... 1st adhesion layer, 374 ... 1st wiring layer, 38 ... 2nd wiring, 381 ... 1st conductive layer, 382 ... 2nd Conductive layer, 383 ... Second adhesion layer, 384 ... Second wiring layer, 41 ... Nozzle plate, 42 ... Vibration absorber, 51 ... Wiring substrate, 70 ... Protective layer, 71 ... First layer, 72 ... Second layer, C ... Pressure chamber, E1 ... 1st region, E2 ... 2nd region, G ... Notch, La ... 1st row, Lb ... 2nd row, N ... Nozzle, R ... Liquid storage chamber, Ra ... Space, Rb ... Space.

Claims (8)

A pressure chamber that communicates with the nozzle that discharges the liquid,
The diaphragm forming a part of the wall surface of the pressure chamber and
When the direction from the pressure chamber to the diaphragm is the first direction,
A first electrode provided on the surface of the diaphragm in the first direction and
A piezoelectric layer provided on the surface of the first electrode in the first direction and including a first region and a second region adjacent to the first region in a plan view.
The second electrode provided in the first region and
A first layer provided in the second region and in contact with the side surface of the second electrode, and
It covers the first layer and includes a second layer that overlaps the first region and the second region in the plan view.
The relative permittivity of the first layer is larger than the relative permittivity of the second layer.
A liquid discharge head in which the Young's modulus of the second layer is smaller than the Young's modulus of the first layer. The liquid discharge head according to claim 1, wherein the film thickness of the second layer is larger than the film thickness of the first layer. The liquid discharge head according to claim 1 or 2, wherein the coefficient of linear expansion of the first layer is smaller than the coefficient of linear expansion of the second layer. The first layer is a liquid discharge head according to any one of claims 1 to 3, which is formed of tantalum oxide. In the direction in which the first electrode, the piezoelectric layer, and the second electrode are laminated, the distance between the second region and the first electrode is between the first region and the first electrode. The liquid discharge head according to any one of claims 1 to 4, which is smaller than the distance of. The liquid discharge head according to any one of claims 1 to 5, wherein a conductive layer having a higher conductivity than the piezoelectric layer is provided on the surface of the second region. With the liquid discharge head according to any one of claims 1 to 6.
A liquid discharge device including a control unit that controls the liquid discharge head. Elastically deformable diaphragm and
The first electrode provided on the surface of the diaphragm and
A piezoelectric layer provided on the surface of the first electrode and including a first region and a second region adjacent to the first region in a plan view,
The second electrode provided in the first region and
A first layer that comes into contact with the side surface of the second electrode and is provided in the second region,
It covers the first layer and includes a second layer that overlaps the first region and the second region in a plan view.
The relative permittivity of the second layer is larger than the relative permittivity of the first layer.
A piezoelectric device in which the Young's modulus of the second layer is smaller than the Young's modulus of the first layer.

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