Liquid discharge device

Abstract

To provide a liquid discharge device that can suppress delay in driving.SOLUTION: A liquid discharge device comprises a liquid discharge head that has a first electrode, a second electrode and a piezoelectric body provided between the first electrode and the second electrode, and a voltage application part that applies a reference voltage that does not vary with time to the first electrode and applies a driving voltage that varies with time to the second electrode, so as to drive the piezoelectric body to discharge liquid, where when the reference voltage is applied to the first electrode and the minimum value of the drive voltage is applied to the second electrode, a specific permittivity of the piezoelectric body is equal to 6000 or lower.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a liquid ejection device.

Background Art

[0002] Liquid ejection devices including a liquid ejection head that ejects a liquid such as ink onto a medium such as printing paper have been conventionally proposed. As such a liquid ejection device, a piezoelectric inkjet printer is known. In the piezoelectric method, a piezoelectric element that vibrates a diaphragm constituting a part of the wall surface of a pressure chamber is used. By vibrating the diaphragm with the piezoelectric element, the liquid filled in the pressure chamber is ejected from the nozzle.

[0003] The piezoelectric element described in Patent Document 1 has two electrodes and a piezoelectric body sandwiched between the two electrodes. Such a piezoelectric body satisfies predetermined conditions for the saturation polarization, the remanent polarization, and the coercive field in the polarization - electric field hysteresis characteristics.

[0004] The piezoelectric element included in the liquid ejection head described in Patent Document 2 has a first electrode, a second electrode, and a piezoelectric body disposed between these electrodes. The piezoelectric body satisfies predetermined conditions for the remanent polarization and the coercive field in the relationship between the voltage and the polarization of the piezoelectric body in order to enhance the responsiveness of the deformation to the voltage.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Various studies have been conducted on the hysteresis shape of piezoelectric materials as described in Patent Documents 1 and 2. Here, generally, the drive waveform applied to the piezoelectric material is set such that the difference between the minimum value of the drive voltage and the reference voltage is near the coercive voltage. As shown in Patent Document 1, near the coercive voltage, the generated current is large and the change in displacement amount is also large, which is preferable from the viewpoint of ejection efficiency.

[0007] However, in the conventional design, a delay occurs in the response of piezoelectric material driving near the coercive voltage. In particular, when performing high-frequency driving, it has been found that this delay becomes a problem. As described above, by setting the difference between the minimum value of the drive voltage and the reference voltage near the coercive voltage, the displacement amount can be increased. However, near the coercive voltage, the generated current is large and exceeds the amount of current that can flow as a circuit. This is considered to be the cause of the delay in piezoelectric material driving.

[0008] Therefore, as a result of the inventors' intensive study of the degree of the drive delay, a liquid ejection device capable of suppressing the drive delay has been found.

Means for Solving the Problem

[0009] A liquid ejection device according to a preferred embodiment of the present invention includes a liquid ejection head having a first electrode, a second electrode, and a piezoelectric material provided between the first electrode and the second electrode, and a voltage application unit that applies a reference voltage that does not change with time to the first electrode and a drive voltage that changes with time to the second electrode to drive the piezoelectric material and eject liquid. The relative permittivity of the piezoelectric material when the reference voltage is applied to the first electrode and the minimum value of the drive voltage is applied to the second electrode is 6000 or less.

Brief Description of the Drawings

[0010]

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Best Mode for Carrying Out the Invention

[0011] Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. Note that the dimensions or scales of each part in the drawings are appropriately different from the actual ones, and there are also parts schematically shown for easy understanding. Further, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

[0012] The following description is made by appropriately using the X-axis, Y-axis, and Z-axis that intersect each other. One direction along the X-axis is referred to as the X1 direction, and the direction opposite to the X1 direction is referred to as the X2 direction. The directions opposite to each other along the Y-axis are referred to as the Y1 direction and the Y2 direction. The directions opposite to each other along the Z-axis are referred to as the Z1 direction and the Z2 direction. Looking in the direction along the Z-axis is referred to as "plan view". The Z-axis is typically a vertical axis. However, the Z-axis does not have to be a vertical axis. Also, the X-axis, Y-axis, and Z-axis typically intersect at right angles to each other, but are not limited thereto, and may intersect at an angle within the range of, for example, 80° or more and 100° or less.

[0013] 1. This Embodiment 1-1. Overall Configuration of the Liquid Discharge Device 100 FIG. 1 is a configuration diagram schematically showing a liquid discharge device 100 according to this embodiment. The liquid discharge device 100 is an inkjet printing device that discharges ink, which is an example of a liquid, as droplets onto a medium 12. The medium 12 is typically printing paper. Note that the medium 12 is not limited to printing paper, and may be a printing object of any material such as a resin film or a fabric.

[0014] As shown in FIG. 1, a liquid container 14 for storing ink is attached to the liquid discharge device 100. Specific examples of the liquid container 14 include a cartridge detachable from the liquid discharge device 100, a bag-shaped ink pack formed of a flexible film, and an ink tank that can be refilled with ink. Note that the type of ink stored in the liquid container 14 is arbitrary.

[0015] The liquid ejection device 100 includes a control unit 20, a conveyance mechanism 22, a movement mechanism 24, and a liquid ejection head 26. The control unit 20 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage circuit such as a semiconductor memory, and controls the operations of the respective elements of the liquid ejection device 100. The control unit 20 includes a voltage application unit 29 that ejects ink from the nozzles by controlling the driving of a piezoelectric element 44 described later.

[0016] The conveyance mechanism 22 conveys the medium 12 in the Y2 direction under the control of the control unit 20. The movement mechanism 24 reciprocates the liquid ejection head 26 in the X1 direction and the X2 direction under the control of the control unit 20. In the example shown in FIG. 1, the movement mechanism 24 includes a substantially box-shaped carrier 242 called a carriage that houses the liquid ejection head 26, and a conveyor belt 244 to which the carrier 242 is fixed. Note that the number of liquid ejection heads 26 mounted on the carrier 242 is not limited to one, and a plurality of them may be provided. Further, in addition to the liquid ejection head 26, a liquid container 14 may be mounted on the carrier 242.

[0017] The liquid ejection head 26 ejects ink supplied from the liquid container 14 toward the medium 12 in the Z2 direction from each of a plurality of nozzles under the control of the control unit 20. By performing this ejection in parallel with the conveyance of the medium 12 by the conveyance mechanism 22 and the reciprocating movement of the liquid ejection head 26 by the movement mechanism 24, an image formed by ink is formed on the surface of the medium 12.

[0018] 1-2. Overall Configuration of Liquid Ejection Head FIG. 2 is an exploded perspective view of the liquid ejection head 26 shown in FIG. 1. FIG. 3 is a cross-sectional view of a part of the liquid ejection head shown in FIG. 2, which is a cross-sectional view taken along line III-III in FIG. 2. As shown in FIG. 2, the liquid ejection head 26 has a plurality of nozzles N arranged in a direction along the Y-axis. In the example shown in FIG. 2, the plurality of nozzles N are divided into a first row L1 and a second row L2 that are spaced apart from each other in a direction along the X-axis. Each of the first row L1 and the second row L2 is a set of a plurality of nozzles N linearly arranged in a direction along the Y-axis. Elements related to each nozzle N in the first row L1 and elements related to each nozzle N in the second row L2 in the liquid ejection head 26 are substantially symmetric to each other in a direction along the X-axis. In the following description, elements corresponding to the first row L1 will be mainly described, and the description of elements corresponding to the second row L2 will be omitted as appropriate.

[0019] Note that the positions of the plurality of nozzles N in the first row L1 and the plurality of nozzles N in the second row L2 in the direction along the Y-axis may coincide with each other or may be different. Also, elements related to each nozzle N in one of the first row L1 and the second row L2 may be omitted.

[0020] As shown in FIGS. 2 and 3, the liquid ejection head 26 includes a nozzle plate 62, a vibration absorber 64, a flow path substrate 32, a pressure chamber substrate 34, a diaphragm 36, a wiring substrate 46, a housing portion 48, and a drive circuit 50. Each of the nozzle plate 62, the vibration absorber 64, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, the wiring substrate 46, and the housing portion 48 is a plate-shaped member that is long in a direction along the Y-axis. The nozzle plate 62, the flow path substrate 32, the pressure chamber substrate 34, the diaphragm 36, and the wiring substrate 46 are arranged in this order in the Z1 direction.

[0021] The nozzle plate 62 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 through which ink passes. The nozzle N ejects ink by the vibration of the diaphragm 36. The nozzle plate 62 is joined to the flow path substrate 32, for example, by an adhesive.

[0022] In the flow path substrate 32, flow paths for supplying ink to a plurality of nozzles N are formed. Specifically, in the flow path substrate 32, a space Ra, a plurality of supply flow paths 322, a plurality of communication flow paths 324, and a supply liquid chamber 326 are formed. The space Ra is an elongated opening extending in the direction along the Y-axis in a plan view when viewed in the direction along the Z-axis. Each of the supply flow paths 322 and the communication flow paths 324 is a through hole formed for each nozzle N. The supply liquid chamber 326 is an elongated space extending in the direction along the Y-axis across the plurality of nozzles N, and communicates the space Ra and the plurality of supply flow paths 322 with each other. Each of the plurality of communication flow paths 324 overlaps with one nozzle N corresponding to the communication flow path 324 in a plan view. The pressure chamber substrate 34 is joined to the flow path substrate 32, for example, by an adhesive.

[0023] In the pressure chamber substrate 34, a plurality of pressure chambers C are formed. The plurality of pressure chambers C are arranged in the direction along the Y-axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in the direction along the X-axis in a plan view. The pressure chamber C is a space located between the flow path substrate 32 and the diaphragm 36. The pressure chamber C communicates with the nozzle N via the communication flow path 324 and also communicates with the space Ra via the supply flow path 322 and the supply liquid chamber 326.

[0024] Each of the nozzle plate 62, the flow path substrate 32, and the pressure chamber substrate 34 is manufactured, for example, by processing a single crystal silicon substrate using dry etching, wet etching, or the like. However, other known methods may be appropriately used for manufacturing each of the nozzle plate 62, the flow path substrate 32, and the pressure chamber substrate 34.

[0025] The diaphragm 36 is disposed on the surface of the pressure chamber substrate 34 facing the Z2 direction. The diaphragm 36 is an elastically vibratable plate-like member.

[0026] On the surface of the diaphragm 36 facing the Z1 direction, a plurality of piezoelectric elements 44 corresponding to the nozzles N are arranged. Each piezoelectric element 44 has an elongated shape extending in the direction along the X-axis in plan view. The plurality of piezoelectric elements 44 correspond to the plurality of pressure chambers C and are arranged in the direction along the Y-axis. The piezoelectric element 44 deforms when a voltage is applied. When the diaphragm 36 vibrates in conjunction with the deformation, the pressure in the pressure chamber C fluctuates, causing the ink to be ejected from the nozzle N.

[0027] The housing portion 48 is a case for storing the ink supplied to the plurality of pressure chambers C. As shown in FIG. 3, a space Rb is formed in the housing portion 48. The space Rb in the housing portion 48 and the space Ra in the flow path substrate 32 communicate with each other. The space composed of the space Ra and the space Rb functions as a liquid storage chamber R, which is a reservoir for storing the ink supplied to the plurality of pressure chambers C. Ink is supplied to the liquid storage chamber R through an inlet 482 formed in the housing portion 48. The ink in the liquid storage chamber R is supplied to the pressure chamber C through the supply liquid chamber 326 and each supply flow path 322.

[0028] The vibration absorber 64 is a flexible film that constitutes the wall surface of the liquid storage chamber R. The vibration absorber 64 is a compliance substrate that absorbs pressure fluctuations of the ink in the liquid storage chamber R.

[0029] The wiring substrate 46 is a plate-like member on which wirings for electrically connecting the drive circuit 50 and the plurality of piezoelectric elements 44 are formed. The surface of the wiring substrate 46 facing the Z2 direction is joined to the diaphragm 36 via a plurality of conductive bumps B. On the other hand, the drive circuit 50 is mounted on the surface of the wiring substrate 46 facing the Z1 direction. The drive circuit 50 is an IC (Integrated Circuit) chip that outputs a drive voltage Com and a reference voltage E0 for driving each piezoelectric element 44. Note that the wiring substrate 46 is not limited to a rigid substrate, and for example, it may be an FPC (Flexible Printed Circuits) or an FFC (Flexible Flat Cable). In this case, the drive circuit 50 may be mounted on the wiring substrate 46, or the wiring substrate 46 may also serve as the external wiring 52.

[0030] As shown in FIG. 2, the end of the external wiring 52 is joined to the surface of the wiring board 46 facing the Z1 direction. The external wiring 52 is composed of connection components such as FPC (Flexible Printed Circuits) or FFC (Flexible Flat Cable), for example. The wiring board 46 is formed with a plurality of wirings 461 that electrically connect the external wiring 52 and the drive circuit 50, and a plurality of wirings 462 to which the drive voltage Com and the reference voltage E0 output from the drive circuit 50 are supplied.

[0031] 1-3. Diaphragm 36 and Piezoelectric Element 44 FIG. 4 is an enlarged cross-sectional view of a part of the liquid ejection head 26 shown in FIG. 3. The diaphragm 36 shown in FIG. 4 vibrates in response to the drive of the piezoelectric body 443 of the piezoelectric element 44 described later. The diaphragm 36 has a first layer 361 and a second layer 362. The first layer 361 and the second layer 362 are laminated in the Z1 direction in this order.

[0032] The first layer 361 is an elastic film made of, for example, silicon oxide (SiO 2 ). The elastic film is formed, for example, by thermally oxidizing one surface of a single crystal silicon substrate. The second layer 362 is an insulating film made of, for example, zirconium oxide (ZrO 2 ). The insulating film is formed, for example, by forming a layer of zirconium by sputtering and thermally oxidizing the layer. Zirconium oxide has excellent electrical insulation, mechanical strength, and toughness. Therefore, by including the second layer 362 containing zirconium oxide in the diaphragm 36, the characteristics of the diaphragm 36 can be enhanced.

[0033] Note that another layer such as a metal oxide may be interposed between the first layer 361 and the second layer 362. Also, a part or all of the diaphragm 36 may be integrally formed with the pressure chamber substrate 34. Further, the diaphragm 36 may be composed of a layer of a single material.

[0034] The pressure chamber C of the pressure chamber substrate 34 is formed, for example, by anisotropically etching a single-crystalline silicon substrate. Although not shown, the planar shape of the pressure chamber C is rectangular. However, the planar shape of the pressure chamber C is not limited to this and is arbitrary. For example, when formed by anisotropic etching on a single-crystalline silicon substrate with a plane orientation of (110), the planar shape of the pressure chamber C is a parallelogram.

[0035] The piezoelectric element 44 overlaps the pressure chamber C in plan view. The piezoelectric element 44 has a second electrode 442, a seed layer 444, a piezoelectric body 443, and a first electrode 441, which are laminated in this order in the Z1 direction. Note that other layers such as a layer for enhancing adhesion may be appropriately interposed between the layers of the piezoelectric element 44 or between the piezoelectric element 44 and the diaphragm 36.

[0036] The second electrode 442 is an individual electrode that is arranged separately from each other for each piezoelectric element 44. Specifically, a plurality of second electrodes 442 extending in the direction along the X axis are arranged at intervals in the direction along the Y axis. A drive voltage Com for discharging ink from the nozzle N is applied to the second electrode 442 of each piezoelectric element 44.

[0037] Examples of the material of the second electrode 442 include metal materials such as aluminum (Al), nickel (Ni), gold (Au), and copper (Cu), or alloys. The second electrode 442 may be a single layer or a plurality of layers. For example, the second electrode 442 has a first layer made of titanium (Ti), a second layer made of platinum (Pt), and a third layer made of iridium (Ir), which are laminated in this order in the Z1 direction. Also, the second electrode 442 is formed by, for example, known film-forming techniques such as sputtering and known processing techniques using photolithography and etching.

[0038] The first electrode 441 is a strip-shaped common electrode that extends in the direction along the Y axis so as to be continuous across a plurality of piezoelectric elements 44. A reference voltage E0 is applied to the first electrode 441.

[0039] Examples of the material of the first electrode 441 include metallic materials such as aluminum (Al), nickel (Ni), gold (Au), copper (Cu), or alloys. The first electrode 441 may be a single layer or multiple layers. For example, the first electrode 441 has, for example, a layer made of iridium, a layer made of iridium oxide (IrOx), a layer made of titanium oxide (TiOx), and a layer made of iridium, and these are laminated in this order from the piezoelectric body 443. The first electrode 441 is formed by a known film formation technique such as a sputtering method and a known processing technique using photolithography and etching.

[0040] The piezoelectric body 443 is disposed between the first electrode 441 and the second electrode 442. The piezoelectric body 443 is, for example, strip-shaped extending along the Y-axis, and is separated for each piezoelectric element 44 by forming a plurality of notches. Note that the piezoelectric body 443 may be provided individually for a plurality of piezoelectric elements 44.

[0041] The piezoelectric body 443 is composed of a piezoelectric material having a perovskite crystal structure represented by the general composition formula ABO 3 Examples of the piezoelectric material include lead titanate (PbTiO 3 ), lead zirconate titanate (PZT: Pb(Zr,Ti)O 3 ), lead zirconate (PbZrO 3 ), lead lanthanum titanate ((Pb,La),TiO 3 ), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O 3 ), lead zirconium titanate niobate (Pb(Zr,Ti,Nb)O 3 ), lead zirconium titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O 3 ), and potassium sodium niobate (KNN). Among them, lead zirconate titanate (PZT) is preferably used as the constituent material of the piezoelectric body 443. Note that the piezoelectric body 443 may contain a small amount of other elements such as impurities.

[0042] The piezoelectric body 443 is formed, for example, by forming a precursor layer of the piezoelectric body 443 by the sol-gel method or the MOD (metal organic decomposition) method and firing and crystallizing the precursor layer. The piezoelectric body 443 may be a single layer or a plurality of layers.

[0043] The seed layer 444 is disposed between the second electrode 442 and the piezoelectric body 443. The seed layer 444 is provided in the same region as the second electrode 442 and has the same shape in plan view. Note that the seed layer 444 only needs to be disposed between the second electrode 442 and the piezoelectric body 443. The seed layer 444 may be provided, for example, in the same region as the piezoelectric body 443 and have the same shape in plan view.

[0044] The seed layer 444 has a function of improving the orientation of the piezoelectric body 443 when the piezoelectric body 443 is formed. Specifically, the seed layer 444 is composed of, for example, titanium (Ti). When the seed layer 444 is composed of titanium, when the piezoelectric body 443 is formed, island-shaped Ti serves as crystal nuclei to improve the orientation of the piezoelectric body 443. The seed layer 444 containing titanium is formed by, for example, a known film formation technique such as the sputtering method and a known processing technique using photolithography and etching. Note that the seed layer 444 may be regarded as a part of the second electrode 442.

[0045] In addition, the seed layer 444 is not limited to the configuration composed of titanium, and may be composed of, for example, a complex oxide having a perovskite structure containing lead, iron, and titanium as constituent elements. In this case, when the piezoelectric body 443 is formed, the orientation of the piezoelectric body 443 is improved because the piezoelectric body 443 is affected by the crystal structure of the seed layer 444. The complex oxide is, for example, a solid solution of 3 and PbTiO 3 and is (Bi, Pb)(Fe, Ti)O 3It is represented by . When the seed layer 444 is composed of such a complex oxide, for example, a precursor layer of the complex oxide is formed by the sol-gel method or the MOD method, and the precursor layer is fired and crystallized to form the seed layer 444. Note that the seed layer 444 may be omitted.

[0046] In the piezoelectric element 44 described above, the piezoelectric body 443 deforms according to the voltage applied between the first electrode 441 and the second electrode 442. The voltage application unit 29 described above applies a reference voltage E0 that does not change with time to the first electrode 441 and a driving voltage Com that changes with time to the second electrode 442, thereby driving the piezoelectric body 443 and ejecting the ink. When a voltage difference occurs between the first electrode 441 and the second electrode 442 due to the application of the driving voltage Com and the reference voltage E0, the piezoelectric body 443 deforms.

[0047] 1-4. Driving voltage Com, reference voltage E0, and applied voltage Ea FIG. 5 is a diagram for explaining the driving voltage Com and the reference voltage E0. The horizontal axis shown in FIG. 5 is time, and the vertical axis is voltage [V].

[0048] The driving voltage Com changes with time. The driving voltage Com includes a driving waveform WCom. The driving waveform WCom is repeated in a unit period Tu. The driving waveform WCom includes an intermediate voltage Ek, a maximum voltage En, and a minimum voltage Em. The maximum voltage En is the maximum value of the driving voltage Com. The minimum voltage Em is the minimum value of the driving voltage Com. The driving waveform WCom decreases from the intermediate voltage Ek to the minimum voltage Em, maintains the minimum voltage Em, then rises from the minimum voltage Em to the maximum voltage En, maintains the maximum voltage En, and then decreases to the intermediate voltage Ek. Note that the driving waveform WCom shown in FIG. 5 is an example, and the driving voltage Com may have other waveforms.

[0049] The reference voltage E0 does not change with time and is constant. In the illustrated example, the reference voltage E0 is a voltage value higher than the minimum voltage Em of the driving voltage Com, but is not limited thereto.

[0050] As described above, the piezoelectric body 443 is provided between the first electrode 441 and the second electrode 442. The piezoelectric body 443 is driven by the voltage difference between the reference voltage E0 applied to the first electrode 441 and the drive voltage Com applied to the second electrode 442. An applied voltage Ea, which is the difference between the reference voltage E0 and the drive voltage Com, is supplied to the piezoelectric body 443.

[0051] FIG. 6 is an illustration of the applied voltage Ea, which is the voltage actually applied to the piezoelectric body 443 when the drive voltage Com shown in FIG. 5 is applied to the first electrode 441 and the reference voltage E0 is applied to the second electrode 442. That is, the applied voltage Ea shown in FIG. 6 is obtained by subtracting the reference voltage E0 from the drive voltage Com at each time.

[0052] The horizontal axis shown in FIG. 6 represents time, and the vertical axis represents voltage [V]. The applied voltage Ea includes a waveform WEa. The waveform WEa includes an intermediate voltage EK, a maximum voltage EN, and a minimum voltage EM. The maximum voltage EN is the difference between the maximum voltage En of the drive voltage Com and the reference voltage E0. The minimum voltage EM is the difference between the minimum voltage Em of the drive voltage Com and the reference voltage E0. Note that the waveform WEa shown in FIG. 6 is an example and varies depending on the drive voltage Com and the reference voltage E0.

[0053] Since the reference voltage E0 is constant, the voltage range RE of the applied voltage Ea is equal to the voltage range RE of the drive voltage Com.

[0054] As described above, the piezoelectric body 443 deforms according to the voltage applied between the first electrode 441 and the second electrode 442. First, by lowering the voltage from the intermediate voltage EK to the minimum voltage EM, that is, by discharging, the piezoelectric element 44 and the diaphragm 36 deform so as to bend in the Z1 direction. As a result, ink is taken into the pressure chamber C. Next, by raising the voltage from the minimum voltage EM to the maximum voltage EN, that is, by charging, the piezoelectric element 44 and the diaphragm 36 deform so as to bend in the Z2 direction. As a result, the ink in the pressure chamber C is ejected from the nozzle.

[0055] Incidentally, hereinafter, the operation of the piezoelectric element 44 at the minimum voltage EM may be referred to as a Pull operation. That is, the operation in which the diaphragm 36 bends in the Z1 direction and ink is taken into the pressure chamber C may be referred to as a Pull operation. Also, the operation of the piezoelectric element 44 at the maximum voltage EN may be referred to as a Push operation. That is, the operation in which the diaphragm 36 bends in the Z2 direction and the ink in the pressure chamber C is ejected from the nozzle may be referred to as a Push operation.

[0056] Here, it is required to increase the displacement amount of the diaphragm 36 in order to increase the ink ejection amount. In order to gain the displacement amount of the diaphragm 36, the minimum voltage EM is set near the coercive voltage, that is, the voltage in the coercive electric field of the piezoelectric body 443. That is, the difference between the minimum voltage Em, which is the minimum value of the drive voltage Com, and the reference voltage E0 is set to be near the coercive voltage.

[0057] However, if the minimum voltage EM is set to the coercive voltage, the reaction of the diaphragm 36 during the Pull operation will be delayed. As a result, there is a problem that the driving of the entire liquid ejection head 26 is delayed. In particular, in the case of high-frequency driving, this delay in the Pull operation becomes a problem. By setting the minimum voltage EM to the coercive voltage, the displacement amount can be increased, but the generated current becomes large. It is considered that the decrease in the responsiveness of the diaphragm 36 during the Pull operation due to the generated current exceeding the amount of current that can flow through the circuit is the cause of the driving delay.

[0058] As a result of intensive studies by the inventors, it has been found that when the relative permittivity of the piezoelectric body 443 when the minimum voltage EM is applied is 6000 or less, the responsiveness of the diaphragm 36 during the Pull operation can be improved as compared with the case where it exceeds 6000. Since the responsiveness of the diaphragm 36 during the Pull operation can be improved by the relative permittivity of the piezoelectric body 443 being 6000 or less, the delay in driving of the entire liquid ejection head 26 can be suppressed. Therefore, high-quality printing performance corresponding to high-frequency driving can be provided.

[0059] 1-5. Examples Hereinafter, with reference to the first embodiment and the second embodiment, suppression of driving delay due to the relative permittivity of the piezoelectric body 443 being 6000 or less will be described.

[0060] 1-5a. First Embodiment FIG. 7 is an illustration of a hysteresis curve showing the relationship between the voltage and polarization of the piezoelectric body 443 included in the piezoelectric element 44 of the first embodiment. FIG. 8 is a butterfly curve showing the relationship between the voltage of the piezoelectric body 443 included in the piezoelectric element 44 of the first embodiment and the displacement amount of the diaphragm. FIG. 9 is a diagram showing the voltage dependence of the relative permittivity of the piezoelectric body 443 included in the piezoelectric element 44 of the first embodiment.

[0061] In FIG. 7, the horizontal axis represents voltage [V], and the vertical axis represents polarization [μC / cm 2 . In FIG. 8, the horizontal axis represents voltage [V], and the vertical axis represents the displacement amount [nm] of the diaphragm 36. The vertical axis can also be regarded as the strain amount of the piezoelectric body 443. The displacement amount of the diaphragm 36 indicates how much it has been displaced toward the Z2 side, that is, the pressure chamber C side, with the position where the diaphragm 36 is on the most Z1 side, that is, the side opposite to the pressure chamber C, being set to 0. That is, the displacement amount of the diaphragm 36 indicates the relative position based on the position on the most Z1 side. In FIG. 9, the horizontal axis represents voltage [V], and the vertical axis represents the relative permittivity.

[0062] During the period of changing from the intermediate voltage EK to the minimum voltage EM in FIG. 6, the voltage decreases toward the anti-voltage -Ec, which is the voltage in the anti-electric field, along the path Rcv1 of the hysteresis curve shown in FIG. 7, and the polarization changes to the negative side. That is, it changes as shown by the arrow a1. At this time, in the butterfly curve shown in FIG. 8, the displacement amount changes to the negative side along the path Rsv1. When the anti-voltage -Ec is reached, the diaphragm 36 is on the most Z1 side, and the displacement amount of the diaphragm 36 becomes 0. The anti-electric field is when the polarization is 0 μC / cm 2This is the magnitude of the electric field when it is in a certain state. Also, at this time, in the curve shown in FIG. 9, as indicated by arrow a3, the dielectric constant increases and reaches the maximum value P1. The maximum value P1 in FIG. 9 corresponds to the voltage in the anti-electric field, that is, the dielectric constant at the anti-voltage -Ec. In the first embodiment, the anti-voltage is about -3.5V.

[0063] Next, in the period when the voltage changes from the minimum voltage EM to the maximum voltage EN in FIG. 6, the path of the hysteresis curve shown in FIG. 7 moves from the path Rcv1 to the path Rcv2, and the polarization changes to the positive side by the voltage range RE. At this time, in the butterfly curve shown in FIG. 8, it moves from the path Rsv1 to the path Rsv2, and the displacement amount of the diaphragm 36 changes to the positive side. And the displacement amount of the diaphragm 36 becomes the displacement amount corresponding to the maximum voltage EN. Also, at this time, in the curve shown in FIG. 9, as indicated by arrow a4, the dielectric constant decreases from the maximum value P1. During this period, as the diaphragm 36 displaces toward the Z2 side, the ink is ejected.

[0064] The material of each piezoelectric body 443 in the first embodiment is lead zirconate titanate (PZT). The piezoelectric body 443 in the first embodiment can be obtained, for example, by satisfying a molar ratio of Pb / Zr / Ti = 118 / 52 / 48.

[0065] 1-5b. Second Embodiment FIG. 10 is an illustration of a hysteresis curve showing the relationship between the voltage and polarization of the piezoelectric body 443 included in the piezoelectric element 44 of the second embodiment. FIG. 11 is a butterfly curve showing the relationship between the voltage of the piezoelectric body 443 included in the piezoelectric element 44 of the second embodiment and the displacement amount of the diaphragm. FIG. 12 is a diagram showing the voltage dependence of the relative dielectric constant of the piezoelectric body 443 included in the piezoelectric element 44 of the second embodiment.

[0066] In FIG. 10, the horizontal axis represents voltage [V], and the vertical axis represents polarization [μC / cm 2 . In FIG. 11, the horizontal axis represents voltage [V], and the vertical axis represents the displacement amount [nm] of the diaphragm 36. The vertical axis can also be regarded as the strain amount of the piezoelectric body 443. In FIG. 12, the horizontal axis represents voltage [V], and the vertical axis represents the relative dielectric constant.

[0067] In the period when the voltage changes from the intermediate voltage EK to the minimum voltage EM in FIG. 6, the voltage decreases toward the counter electric field voltage -Ec along the path Rcv3 of the hysteresis curve shown in FIG. 10, and the polarization changes to the negative side. That is, it changes as shown by the arrow a2. At this time, in the butterfly curve shown in FIG. 11, the displacement amount changes to the negative side along the path Rsv3. When the counter electric field voltage -Ec is reached, the diaphragm 36 is on the Z1 side most, and the displacement amount of the diaphragm 36 becomes 0. Also, at this time, in the curve shown in FIG. 12, the dielectric constant increases as shown by the arrow a5 and reaches near the maximum values P2 and P3. The vicinity of the maximum values P2 and P3 in FIG. 12 corresponds to the dielectric constant at the counter electric field voltage -Ec. In the second embodiment, the counter electric field voltage is about -3.5V.

[0068] Next, in the period when the voltage changes from the minimum voltage EM to the maximum voltage EN in FIG. 6, it moves from the path Rcv3 to the path Rcv4 of the hysteresis curve shown in FIG. 10, and the polarization changes to the positive side by the voltage range RE. At this time, in the butterfly curve shown in FIG. 11, it moves from the path Rsv3 to the path Rsv4, and the displacement amount of the diaphragm 36 changes to the positive side. Then, the displacement amount of the diaphragm 36 becomes the displacement amount corresponding to the maximum voltage EN. Also, at this time, in the curve shown in FIG. 12, as shown by the arrow a4, the dielectric constant decreases from the maximum value P3. During this period, as the diaphragm 36 is displaced toward the Z2 side, the ink is ejected.

[0069] The material of each piezoelectric body 443 in the second embodiment is lead zirconate titanate (PZT). The piezoelectric body 443 in the second embodiment is formed, for example, as follows. For example, when the first electrode 441 contains iridium, the state is such that the iridium is not completely oxidized. By shortening the annealing time for forming the first electrode 441 or increasing the film thickness of the first electrode 441, the degree of oxidation of iridium can be made insufficient. As a result, an amorphous state where the interface between the first electrode 441 and the piezoelectric body 443 is not uniform is created. As a result, the piezoelectric body 443 of the second embodiment is obtained. Note that the first electrode 441 is not an electrode made of iridium, but for example, strontium ruthenate (SrRuO3 ) and an oxide electrode such as lanthanum nickelate (LaNiO 3 ) etc., the piezoelectric body 443 of the second embodiment can be obtained.

[0070] Also, for example, when the piezoelectric body 443 is PZT, by satisfying the relationship of 0.55 < Zr / (Zr + Ti) for the zirconia (Zr) ratio of PZT, the piezoelectric body 443 of the second embodiment can be obtained.

[0071] Also, for example, when the piezoelectric body 443 contains an additive of any one of Mg, Al, Fe or Na, the piezoelectric body 443 of the present embodiment can be obtained. For example, in the case of B-site substitution, examples of the additive include Mg, Al or Fe. In the case of A-site substitution, examples of the additive include Na.

[0072] 1-5c. Evaluation of the embodiment FIG. 13 is a table showing the relative permittivity results of the piezoelectric body 443 in the first embodiment. FIG. 14 is a table showing the relative permittivity results of the piezoelectric body 443 in the second embodiment.

[0073] As shown in FIG. 13, in Comparative Example 1, the relative permittivity of the piezoelectric body 443 when a minimum voltage EM of -3.5V is applied is 12946. -3.5V is the breakdown voltage -Ec of the piezoelectric body 443 in the first embodiment. In Comparative Example 2, the relative permittivity when a minimum voltage EM of -3.0V is applied is 13990. In Comparative Example 3, the relative permittivity when a minimum voltage EM of -2.5V is applied is 12794. In Comparative Example 4, the relative permittivity when a minimum voltage EM of -2.0V is applied is 10995. In Comparative Example 5, the relative permittivity when a minimum voltage EM of -1.5V is applied is 8565. In Comparative Example 6, the relative permittivity when a minimum voltage EM of -1.0V is applied is 7515. The dielectric constants of Comparative Examples 1 to 6 all exceed 6000. In contrast, the relative permittivity of Example 1 is 5887. The relative permittivity of Example 2 is 5500. The relative permittivity of Example 3 is 4094. The relative permittivity of Example 4 is 3718. The dielectric constants of Comparative Examples 1 to 4 are all 6000 or less.

[0074] As shown in FIG. 13, when the dielectric constant is 6000 or less, the responsiveness during the Pull operation of the diaphragm 36 is 80% or more, which is superior to the comparative example where the dielectric constant exceeds 6000.

[0075] As shown in FIG. 14, in Comparative Example 7, the relative dielectric constant when the minimum voltage EM of -3.5V is applied is 8532. -3.5V is the breakdown voltage -Ec of the piezoelectric body 443 in the second embodiment. In Comparative Example 8, the relative dielectric constant when the minimum voltage EM of -1.0V is applied is 6182. In Comparative Example 9, the relative dielectric constant when the minimum voltage EM of -0.5V is applied is 6310. In Comparative Example 10, the relative dielectric constant when the minimum voltage EM of 0V is applied is 8021. In Comparative Example 11, the relative dielectric constant when the minimum voltage EM of 0.5V is applied is 7201. In Comparative Example 12, the relative dielectric constant when the minimum voltage EM of 1.0V is applied is 6254. The dielectric constants of Comparative Examples 7 to 12 all exceed 6000. On the other hand, in Example 5, the relative dielectric constant when the minimum voltage EM of -3.0V is applied is 5874. In Example 6, the relative dielectric constant when the minimum voltage EM of -2.5V is applied is 5241. In Example 7, the relative dielectric constant when the minimum voltage EM of -2.0V is applied is 5421. In Example 8, the relative dielectric constant when the minimum voltage EM of -1.5V is applied is 5912. The dielectric constants of Comparative Examples 5 to 8 are 6000 or less.

[0076] As shown in FIG. 14, when the dielectric constant is 6000 or less, the responsiveness during the Pull operation of the diaphragm 36 is 80% or more, which is superior to the comparative example where the dielectric constant exceeds 6000. Also, in the second embodiment, even when the minimum voltage EM is brought closer to -3.5V, the breakdown voltage -Ec, it is difficult for the relative dielectric constant to exceed 6000 compared to the first embodiment.

[0077] FIG. 15 is a diagram showing the relationship between the relative dielectric constant of the piezoelectric body 443 and the responsiveness of the diaphragm 36 in the first embodiment and the second embodiment. FIG. 15 is a diagram plotting the relationship between the relative dielectric constants and the responsiveness of the aforementioned Comparative Examples 1 to 12 and Examples 1 to 8.

[0078] As shown in FIG. 15, in both the first and second embodiments, when the relative permittivity is 6000 or less, it can be seen that the responsiveness is clearly superior compared to the case where it exceeds 6000.

[0079] In the liquid ejection device 100 of the present embodiment, when the reference voltage E0 is applied to the first electrode 441 and the minimum voltage Em, which is the minimum value of the drive voltage Com, is applied to the second electrode 442, that is, when the minimum voltage EM is applied, the relative permittivity of the piezoelectric body 443 is 6000 or less. As can also be seen from FIG. 15, since the relative permittivity of the piezoelectric body 443 when the minimum voltage EM is applied is 6000 or less, it is possible to improve the responsiveness of the diaphragm 36 during the Pull operation compared to the case where it exceeds 6000. For this reason, the delay in driving of the entire liquid ejection head 26 can be suppressed. Therefore, it is possible to provide high-quality printing performance corresponding to high-frequency driving.

[0080] Also, the relative permittivity of the piezoelectric body 443 when the minimum voltage EM is applied only needs to be 6000 or less, but it is more preferably 5500 or less. In the first embodiment of FIG. 13, in Examples 2, 3, and 4, the relative permittivity is 5500 or less, and in Example 1, the relative permittivity exceeds 5500. Examples 2 to 4 are superior in the responsiveness of the diaphragm 36 compared to Example 1. Also, in the second embodiment of FIG. 8, in Examples 6 and 7, the relative permittivity is 5500 or less, and in Examples 5 and 8, the relative permittivity exceeds 5500. Examples 6 and 7 are superior in the responsiveness of the diaphragm 36 compared to Examples 5 and 8.

[0081] Also, the relative permittivity of the piezoelectric body 443 when the minimum voltage EM is applied is preferably 3500 or more. By the relative permittivity being 3500 or more, generation of noise can be suppressed compared to the case where it is less than 3500. From this viewpoint, the relative permittivity of the piezoelectric body 443 when the minimum voltage EM is applied is more preferably 3700 or more.

[0082] FIG. 16 is an evaluation waveform of the responsiveness of the diaphragm 36. The responsiveness of the diaphragm 36 during the Pull operation was evaluated by the following method. Each of the responsivenesses shown in FIGS. 13, 14, and 15 described above is the result of evaluation by the following method.

[0083] As a measuring device, an arbitrary waveform generator AFG3022C (Tektronix), a voltage amplifier HAS4011 (NF circuit design block), an oscilloscope HDO4024 (Teiedyne Lecroy), and a laser displacement system NLV-2500 (Polytec) were used. The voltage waveform of FIG. 10 output from the arbitrary waveform generator and amplified 10 times by the voltage amplifier was applied to the piezoelectric element 44 having a planar area of 97680 μm 2 Then, the displacement amount of the piezoelectric element 44 is detected by the laser displacement meter. Then, the detected displacement amount is converted into a voltage and captured by the oscilloscope.

[0084] As shown in FIG. 16, the voltage gradually decreases from the maximum voltage EN to the minimum voltage EM, and then the voltage is gradually increased from the minimum voltage EM. Specifically, a reference voltage E0 is applied to the first electrode 441. In this state, a voltage such that the drive voltage Com gradually decreases from the maximum voltage En to the minimum voltage Em and then gradually increases from the minimum voltage Em is applied to the second electrode 442. For example, the voltage changes from the maximum voltage EN to the maximum voltage EN in 2 μs and then immediately returns to the maximum voltage EN in 2 μs. The displacement amount in this case corresponds to the first displacement amount. The displacement amount of the piezoelectric body 443 when the minimum voltage Em of the drive voltage Com is applied in this case is defined as the first displacement amount.

[0085] Next, the voltage is gradually decreased from the maximum voltage EN to the minimum voltage EM, and then a voltage that does not change from the minimum voltage EM is applied. Specifically, the reference voltage E0 is applied to the first electrode 441. In this state, the driving voltage Com is gradually decreased from the maximum voltage En to the minimum voltage Em, and then a voltage that does not change from the minimum voltage Em is applied to the second electrode 442. For example, the voltage is changed from the maximum voltage EN to the maximum voltage EN in 2 μs and held for 98 μs to sufficiently stabilize the Pull state. The displacement amount of the piezoelectric body 443 when the minimum voltage Em of the driving voltage Com in this case is applied is defined as the second displacement amount.

[0086] Then, the ratio of the first displacement amount to the second displacement amount is defined as the displacement amount of the diaphragm 36 during the Pull operation.

[0087] The ratio of the first displacement amount to the second displacement amount, that is, the displacement amount of the diaphragm 36 during the Pull operation, is preferably 80% or more. As shown in FIG. 15, when the ratio, that is, the displacement amount of the diaphragm 36, is 80% or more, the response delay of the diaphragm 36 in the Pull operation is suppressed as compared with the case where it is less than 80%. Therefore, high-quality printing performance corresponding to high-frequency driving can be provided.

[0088] Also, as described above, in the first embodiment, the maximum value P1 shown in FIG. 9 corresponds to the dielectric constant in the anti-voltage. For this reason, in the first embodiment, when the minimum voltage EM is set to -3.5 V which is the anti-voltage, the relative dielectric constant of the piezoelectric body 443 when the minimum voltage EM is applied becomes about 8000. The result of setting the minimum voltage EM to -3.5 V which is the anti-voltage is shown in Comparative Example 1 of FIG. 14. In Comparative Example 1, the responsiveness of the diaphragm 36 during the Pull operation is reduced as compared with each embodiment. Also, as shown in Comparative Examples 2 to 4, when the minimum voltage EM is set near the anti-voltage and the relative dielectric constant exceeds 6000, the responsiveness is reduced as compared with each embodiment, similar to Comparative Example 1.

[0089] Therefore, in the first embodiment, it is desirable that the difference between the minimum voltage Em of the driving voltage Com and the reference voltage E0, that is, the minimum voltage EM, is higher than the counter-voltage -Ec. By having the minimum voltage EM higher than the counter-voltage -Ec, the responsiveness of the diaphragm 36 can be enhanced.

[0090] Also, not limited to the case of the first embodiment, it is preferable that the minimum voltage EM is higher than the counter-electric field -Ecz of the piezoelectric body 443. By having the minimum voltage EM higher than the counter-electric field -Ecz, the piezoelectric element 44 can be driven using a region where polarization reversal does not occur. Thus, malfunction of the piezoelectric element 44 can be suppressed.

[0091] Also, the piezoelectric body 443 may be any piezoelectric body as long as the relative permittivity when the minimum voltage EM is applied is 6000 or less. Therefore, it is not limited to the piezoelectric body 443 of the first embodiment and the second embodiment. However, the piezoelectric body 443 is preferably the piezoelectric body 443 of the first embodiment or the second embodiment.

[0092] Specifically, the piezoelectric body 443 of the first embodiment is the piezoelectric body 443 showing the voltage dependence of the relative permittivity shown in FIG. 9. More specifically, when the reference voltage E0 is applied to the first electrode 441 and a first voltage lower than the minimum voltage Em which is the minimum value of the driving voltage Com is applied to the second electrode 442, the relative permittivity of the piezoelectric body 443 is preferably 8000 or more. The difference between the reference voltage E0 and the first voltage is, for example, the voltage at the counter-electric field -Ecz, that is, the counter-voltage.

[0093] By using such a piezoelectric body 443, compared with the case of using a piezoelectric body 443 formed of a piezoelectric material having a low relative permittivity such as KNN, the displacement amount of the diaphragm 36 can be increased. Thus, while suppressing a decrease in the discharge amount, a decrease in the responsiveness of the diaphragm 36 during the Pull operation can be suppressed.

[0094] Viewed from another perspective, as shown in FIG. 9, when the voltage difference applied between the first electrode 441 and the second electrode 442 of the piezoelectric body 443 of the first embodiment is gradually changed from the saturation positive voltage p1 to the saturation negative voltage p2, the change in relative permittivity has only one maximum value P1. By using such a piezoelectric body 443, the displacement amount of the diaphragm 36 can be increased as compared with the case of using a piezoelectric body 443 formed of a piezoelectric material having a low relative permittivity such as KNN. Further, from the viewpoint of increasing the displacement amount of the diaphragm 36, it is particularly preferable that the maximum value P1 is 8000 or more.

[0095] Also, as shown in FIG. 8, for example, when the minimum voltage EM is -3.5V of the coercive voltage and the voltage range RE = 25V, the maximum voltage EN is 21.5V. The displacement amount SXz in this case is 790nm - 0nm = 790nm. The example of setting the minimum voltage EM to the coercive voltage corresponds to Comparative Example 1.

[0096] On the other hand, when the minimum voltage EM is 0V and the voltage range RE = 25V, the maximum voltage EN is 25.0V. The displacement amount SYz in this case is 820nm - 200nm = 620nm. The example of setting the minimum voltage EM to 0V corresponds to Example 2.

[0097] The ratio of the displacement amount SXz to the displacement amount SYz is SYz / SXz = 78%. Therefore, when the minimum voltage EM is set to a voltage higher than the coercive voltage, a displacement amount of 78% of the case where the minimum voltage EM is set to the coercive voltage can be obtained. That is, Example 2 obtains a displacement amount of 78% of Comparative Example 1. However, as described above, according to Example 2, the responsiveness can be significantly improved as compared with Comparative Example 1. Viewed from another perspective, according to Example 2, the driving delay can be significantly suppressed while suppressing the displacement amount to a small decrease of about 78%. The same can be said for other examples other than Example 2 of the first embodiment.

[0098] Specifically, the piezoelectric body 443 of the second embodiment is a piezoelectric body that exhibits the voltage dependence of the relative permittivity shown in FIG. 12. More specifically, as shown in FIG. 12, the piezoelectric body 443 of the second embodiment has only two maximum values P2 and P3 in the change in relative permittivity when the voltage difference applied between the first electrode 441 and the second electrode 442 is gradually changed from the saturation positive voltage p3 to the saturation negative voltage p4. Such a second embodiment can reduce the maximum values P2 and P3 of the dielectric constant compared to the first embodiment. Therefore, in the second embodiment, even if the minimum voltage EM is made closer to the counter voltage -Ec, the relative permittivity is unlikely to exceed 6000 compared to the first embodiment. Therefore, according to the piezoelectric body 443 of the second embodiment, since the minimum voltage EM can be made closer to the counter voltage -Ec, it is easy to increase the displacement amount of the diaphragm 36. Thus, according to the piezoelectric body 443 of the second embodiment, it is possible to suppress a decrease in the discharge amount while suppressing a decrease in the responsiveness of the diaphragm 36 during the Pull operation. Further, from the viewpoint of increasing the displacement amount of the diaphragm 36, it is particularly preferable that the maximum value P1 is 7000 or more.

[0099] Also, as shown in FIG. 11, for example, when the minimum voltage EM is -3.5V of the counter voltage and the voltage range RE = 25V, the maximum voltage EN becomes 21.5V. The displacement amount SX in this case is 720 nm - 0 nm = 720 nm. The example of setting the minimum voltage EM to the counter voltage corresponds to Comparative Example 7.

[0100] On the other hand, when the minimum voltage EM is -2V and the voltage range RE = 25V, the maximum voltage EN becomes 23.0V. The displacement amount SY in this case is 745 nm - 12 nm = 733 nm. The example of setting the minimum voltage EM to -2V corresponds to Example 7.

[0101] The ratio of the displacement amount SX to the displacement amount SY is SY / SX = 102%. Therefore, when the minimum voltage EM is set to a voltage higher than the counter voltage as in Example 7, a displacement amount of about 102% of the case where the minimum voltage EM is set to the counter voltage can be obtained. According to Example 7, it is possible to suppress the drive delay while maintaining the displacement amount. The same can be said for other examples of the second embodiment other than Example 7.

[0102] 2. Other Modification Examples The embodiments illustrated above can be variously modified. Specific modification modes applicable to the foregoing embodiments are illustrated below. Two or more modes arbitrarily selected from the following illustrations can be appropriately combined within a range not conflicting with each other.

[0103] In the foregoing embodiments, the driving voltage Com has been described assuming the case where it is a positive voltage, but it may be a negative voltage. Even in this case, the applied voltage Ea is set with the same idea as the technical idea in each embodiment. In the foregoing description, the "resistant voltage" is a negative resistant voltage -Ec, but it may be a positive resistant voltage.

[0104] The "liquid ejection head" may be a circulation type head having a so-called circulation flow path. Further, the "liquid ejection head" is not limited to a serial head and may be a line head.

[0105] The "liquid ejection device" can be adopted not only in equipment dedicated to printing but also in various equipment such as facsimile devices and copying machines. The use of the liquid ejection device is not limited to printing. For example, a liquid ejection device that ejects 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 ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wirings and electrodes of a wiring board. Further, a liquid ejection device that ejects a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip.

[0106] The present invention has been described based on the preferred embodiments above, but the present invention is not limited to the foregoing embodiments. Further, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as that of the foregoing embodiments, and any configuration can be added.

Explanation of Reference Numerals

[0107] 26…Liquid ejection head, 29…Voltage application unit, 36…Diaphragm, 44…Piezoelectric element, 100…Liquid ejection device, 441…First electrode, 442…Second electrode, 443…Piezoelectric body, C…Pressure chamber, Com…Drive voltage, E0…Reference voltage, EM…Minimum voltage, EN…Maximum voltage, Em…Minimum voltage, En…Maximum voltage, N…Nozzle, P1, P2, P3…Maxima, RE…Voltage range, -Ec…Breakdown voltage, p1…Saturated positive voltage, p2…Saturated negative voltage, p3…Saturated positive voltage, p4…Saturated negative voltage.

Claims

1. a liquid ejection head having a first electrode, a second electrode, and a piezoelectric body provided between the first electrode and the second electrode; a voltage application unit that applies a reference voltage that does not change over time to the first electrode and a drive voltage that changes over time to the second electrode to drive the piezoelectric body and eject liquid, A liquid ejection device, characterized in that the relative dielectric constant of the piezoelectric body is 6000 or less when the reference voltage is applied to the first electrode and the minimum value of the drive voltage is applied to the second electrode.

2. 2. The liquid ejection device according to claim 1, wherein the relative dielectric constant of the piezoelectric body is 5500 or less when the reference voltage is applied to the first electrode and the minimum value of the drive voltage is applied to the second electrode.

3. 2. The liquid ejection device according to claim 1, wherein the relative dielectric constant of the piezoelectric body is 3500 or more when the reference voltage is applied to the first electrode and the minimum value of the drive voltage is applied to the second electrode.

4. 4. The liquid ejection device according to claim 3, wherein the relative dielectric constant of the piezoelectric body is 3700 or more when the reference voltage is applied to the first electrode and the minimum value of the drive voltage is applied to the second electrode.

5. 4. The liquid ejection device according to claim 1, wherein the difference between the minimum value of the drive voltage and the reference voltage is higher than a coercive voltage of the piezoelectric body.

6. A liquid ejection device as described in claim 1 or 3, characterized in that the relative dielectric constant of the piezoelectric body is 8000 or more when the reference voltage is applied to the first electrode and a first voltage lower than the minimum value of the driving voltage is applied to the second electrode.

7. A liquid ejection device as described in claim 1 or 3, characterized in that the change in dielectric constant of the piezoelectric body when the voltage difference applied to the first electrode and the second electrode is gradually changed from a saturated positive voltage to a saturated negative voltage has only one maximum value.

8. A liquid ejection device as described in claim 1 or 3, characterized in that the change in dielectric constant of the piezoelectric body when the voltage difference applied to the first electrode and the second electrode is gradually changed from a saturated positive voltage to a saturated negative voltage has only two maximum values.

9. a first displacement amount is a displacement amount of the piezoelectric body when the minimum value of the driving voltage is applied in a case where the reference voltage is applied to the first electrode and a voltage that gradually decreases from the maximum value of the driving voltage to the minimum value of the driving voltage and then gradually increases from the minimum value of the driving voltage is applied to the second electrode; When the reference voltage is applied to the first electrode and a voltage that gradually decreases from the maximum value of the drive voltage to the minimum value of the drive voltage and then does not change from the minimum value of the drive voltage is applied to the second electrode, the displacement amount of the piezoelectric body when the minimum value of the drive voltage is applied is defined as a second displacement amount, 2. The liquid ejection device according to claim 1, wherein a ratio of the first displacement amount to the second displacement amount is 80% or more.

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