JP2019202432A - Liquid jet head, liquid jet device and piezoelectric device - Google Patents

Abstract

To provide a liquid jet head that can reduce the possibilities that crack may occur in a vibration plate, a liquid jet device and a piezoelectric device.SOLUTION: The liquid jet head comprises a pressure chamber for storing liquid, a vibration plate constituting a wall surface of the pressure chamber, a piezoelectric element formed in the vibration plate, and a driving circuit that applies voltages to the piezoelectric element. The piezoelectric element includes a first part and a second part formed at positions different from each other in a planar view, and the driving circuit applies to the first part a voltage that varies in a range between a second voltage V2 between an anti-voltage Vc (-) with a first polarity of the piezoelectric element and a first voltage V1 with a second polarity opposite to the first polarity and the first voltage; and applies to the second part a voltage that varies in a range between a fourth voltage V4 between the anti-voltage and a third voltage V3 with the second polarity and the third voltage, where the second voltage is closer to the anti-voltage than the fourth voltage.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a structure and driving of a piezoelectric element that is preferably used in a liquid ejecting head.

  2. Description of the Related Art Conventionally, a liquid ejecting head that ejects liquid in a pressure chamber from a nozzle by vibrating a diaphragm constituting a wall surface of the pressure chamber with a piezoelectric element has been proposed. For example, Patent Document 1 discloses a piezoelectric element having a configuration in which a first upper electrode and a second upper electrode are formed on a surface of a piezoelectric layer. The voltage applied to the first upper electrode is lower than the voltage applied to the second upper electrode.

JP 2011-29305 A

  There is a possibility that a crack (crack) may occur in a region of the diaphragm corresponding to the interval between the piezoelectric elements due to repeated vibration. From the viewpoint of reducing the possibility of cracks occurring in the diaphragm, there is room for further improvement in the technique of Patent Document 1.

  In order to solve the above-described problems, a liquid jet head according to a preferred aspect of the present invention includes a pressure chamber that contains a liquid, a diaphragm that forms a wall surface of the pressure chamber, and a piezoelectric element that is formed on the diaphragm. A liquid ejecting head including an element and a drive circuit for applying a voltage to the piezoelectric element, wherein the piezoelectric element includes a first portion and a second portion formed at different positions in plan view; The drive circuit is in a range between a second voltage between the first voltage coercive voltage of the piezoelectric element and a first voltage having a second polarity opposite to the first polarity, and the first voltage. Is applied to the first portion, and a voltage that varies within a range between the fourth voltage between the coercive voltage and the third voltage of the second polarity and the third voltage is applied. , Applied to the second portion, the second voltage being closer to the coercive voltage than the fourth voltage.

  A piezoelectric device according to a preferred aspect of the present invention is a piezoelectric device comprising a diaphragm, a piezoelectric element formed on the diaphragm, and a drive circuit for applying a voltage to the piezoelectric element, wherein the piezoelectric element Includes a first portion and a second portion formed at different positions in plan view, and the drive circuit has a second polarity opposite to the first polarity coercive voltage and the first polarity of the piezoelectric element. A second voltage between the first voltage and a voltage varying within a range between the first voltage is applied to the first portion, the coercive voltage and the third voltage having the second polarity, A voltage that fluctuates within a range between the fourth voltage and the third voltage is applied to the second portion, and the second voltage is closer to the coercive voltage than the fourth voltage.

1 is a configuration diagram of a liquid ejecting apparatus according to a first embodiment. 3 is a block diagram illustrating a functional configuration of a liquid ejecting head. FIG. It is a wave form diagram of a drive signal. FIG. 3 is an exploded perspective view of a liquid ejecting head. FIG. 5 is a cross-sectional view of the liquid jet head (a cross-sectional view taken along line VV in FIG. 2). It is a top view of a plurality of piezoelectric elements. It is sectional drawing of the VII-VII line in FIG. It is sectional drawing of the VIII-VIII line in FIG. It is a wave form diagram of the voltage applied to the 1st part and 2nd part of a piezoelectric element. It is a graph which shows the relationship between the applied voltage of a piezoelectric element, and the amount of distortion. It is explanatory drawing of the displacement amount of a diaphragm. It is a graph which shows the relationship between the applied voltage and distortion amount of the piezoelectric element in 2nd Embodiment. It is a block diagram of the piezoelectric element in a modification.

<First Embodiment>
FIG. 1 is a configuration diagram illustrating a liquid ejecting apparatus 100 according to the first embodiment of the invention. The liquid ejecting apparatus 100 according to the first embodiment is an ink jet printing apparatus that ejects ink, which is an example of a liquid, onto a medium (ejection target) 12. The medium 12 is typically printing paper, but a printing target of an arbitrary material such as a resin film or a fabric is used as the medium 12. As illustrated in FIG. 1, the liquid ejecting apparatus 100 is provided with a liquid container 14 that stores ink. For example, a cartridge that can be attached to and detached from the liquid ejecting apparatus 100, a bag-shaped ink pack formed 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 ejecting apparatus 100 includes a control unit 20, a transport mechanism 22, a moving mechanism 24, and a liquid ejecting 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 comprehensively controls each element of the liquid ejecting apparatus 100. The transport mechanism 22 transports the medium 12 in the Y direction under the control of the control unit 20.

  The moving mechanism 24 reciprocates the liquid jet head 26 in the X direction under the control of the control unit 20. The X direction is a direction that intersects (typically orthogonal) the Y direction in which the medium 12 is conveyed. The moving mechanism 24 of the first embodiment includes a substantially box-shaped transport body 242 (carriage) that houses the liquid ejecting head 26 and a transport belt 244 to which the transport body 242 is fixed. A configuration in which a plurality of liquid ejecting 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 ejecting head 26 may be employed.

  The liquid ejecting head 26 ejects ink supplied from the liquid container 14 to the medium 12 from a plurality of nozzles (ejection holes) under the control of the control unit 20. In parallel with the transport of the medium 12 by the transport mechanism 22 and the reciprocating reciprocation of the transport body 242, each liquid ejecting head 26 ejects ink onto the medium 12, thereby forming a desired image on the surface of the medium 12. .

  FIG. 2 is a configuration diagram that focuses on the function of the liquid ejecting apparatus 100. Illustration of the transport mechanism 22 and the moving mechanism 24 is omitted for convenience. As illustrated in FIG. 2, the control unit 20 of the first embodiment functions as a control processing unit 201 and a signal generation unit 202. The control processing unit 201 controls the operation of the liquid ejecting head 26 ejecting ink from each of the plurality of nozzles N. For example, the control processing unit 201 generates a control signal S instructing whether or not ink is ejected (ejection / non-ejection) for each nozzle N and supplies the control signal S to the liquid ejecting head 26. The control signal S is generated according to image data supplied from an external device (for example, a host computer). 2 generates the drive signal D, the reference voltage Vbs1 (example of the first reference voltage), and the reference voltage Vbs2 (example of the second reference voltage). The drive signal D, the reference voltage Vbs1, and the reference voltage Vbs2 are used for ejecting ink by the liquid ejecting head 26.

  FIG. 3 is a waveform diagram of the drive signal D. As illustrated in FIG. 3, the drive signal D of the first embodiment is a voltage signal that varies with time in a predetermined cycle. The drive signal D for one cycle is composed of a plurality of sections Q (Q1 to Q5). The section Q1 is a section where the voltage level decreases with time from the predetermined reference voltage V0 to the lower voltage VL, and the section Q2 is a section where the voltage level is maintained at the voltage VL. The section Q3 is a section in which the voltage level rises with time from the voltage VL to the voltage VH exceeding the reference voltage V0, and the section Q4 is a section in which the voltage level is maintained at the voltage VH. The section Q5 is a section in which the voltage level decreases with time from the voltage VH to the reference voltage V0. The waveform of the drive signal D is not limited to the waveform illustrated in FIG.

  As illustrated in FIG. 3, the reference voltage Vbs1 and the reference voltage Vbs2 are predetermined DC voltages. The reference voltage Vbs1 exceeds the reference voltage Vbs2 (Vbs1> Vbs2). The reference voltage Vbs1 of the first embodiment is the same voltage as the reference voltage V0.

  As illustrated in FIG. 2, the liquid ejecting head 26 according to the first embodiment includes a plurality of ejecting units 261 corresponding to different nozzles, and a drive circuit 262 that drives each of the plurality of ejecting units 261. Each of the plurality of ejection units 261 ejects ink according to the drive signal D supplied from the drive circuit 262. Note that the drive circuit 262 can also be installed outside the liquid jet head 26.

  As illustrated in FIG. 2, the control signal S generated by the control processing unit 201 and the drive signal D generated by the signal generation unit 202 are supplied to the drive circuit 262. The drive circuit 262 of the first embodiment drives each of the plurality of ejection units 261 by supplying a drive signal D in accordance with an instruction from the control processing unit 201 (that is, the control signal S). Specifically, the drive circuit 262 supplies the drive signal D to the ejection unit 261 in which the control signal S instructs ink ejection, and the control signal S drives the ejection unit 261 instructing non-ejection of ink. The signal D is not supplied.

  4 is an exploded perspective view of the liquid jet head 26, and FIG. 5 is a cross-sectional view taken along the line VV in FIG. 4 (a cross section parallel to the XZ plane). As illustrated in FIG. 4, a direction perpendicular to the XY plane (for example, a plane parallel to the surface of the medium 12) is hereinafter referred to as a Z direction. The ink ejection direction (typically the vertical direction) by each liquid ejection head 26 corresponds to the Z direction.

  As illustrated in FIGS. 4 and 5, the liquid ejecting head 26 includes a substantially rectangular channel substrate 32 that is long in the Y direction. On the negative surface of the flow path substrate 32 in the Z direction, a pressure chamber substrate 34, a diaphragm 36, a plurality of piezoelectric elements 38, a housing portion 42, and a sealing body 44 are installed. On the other hand, a nozzle plate 46 and a vibration absorber 48 are installed on the positive side surface in the Z direction of the flow path substrate 32. Each element of the liquid jet head 26 is generally a plate-like member that is long in the Y direction, similarly to the flow path substrate 32, and is bonded to each other using, for example, an adhesive.

  As illustrated in FIG. 4, the nozzle plate 46 is a plate-like member on which a plurality of nozzles N arranged in the Y direction are formed. Each nozzle N is a through hole through which ink passes. The flow path substrate 32, the pressure chamber substrate 34, and the nozzle plate 46 are formed, for example, by processing a silicon (Si) single crystal substrate by a semiconductor manufacturing technique such as etching. However, the material and manufacturing method of each element of the liquid jet head 26 are arbitrary. The Y direction can be rephrased as the direction in which the plurality of nozzles N are arranged.

  The flow path substrate 32 is a plate-like member for forming an ink flow path. As illustrated in FIGS. 4 and 5, an opening 322, a supply channel 324, and a communication channel 326 are formed in the channel substrate 32. The opening 322 is a through hole formed in a long shape along the Y direction in a plan view (that is, viewed from the Z direction) so as to be continuous over the plurality of nozzles N. On the other hand, the supply flow path 324 and the communication flow path 326 are through holes formed individually for each nozzle N. In addition, as illustrated in FIG. 5, a relay flow path 328 that extends across the plurality of supply flow paths 324 is formed on the positive surface of the flow path substrate 32 in the Z direction. The relay channel 328 is a channel that connects the opening 322 and the plurality of supply channels 324.

  The housing part 42 is a structure manufactured by injection molding of a resin material, for example, and is fixed to the negative surface of the flow path substrate 32 in the Z direction. As illustrated in FIG. 5, the housing portion 42 is formed with a housing portion 422 and an introduction port 424. The accommodating portion 422 is a concave portion having an outer shape corresponding to the opening portion 322 of the flow path substrate 32, and the introduction port 424 is a through hole communicating with the accommodating portion 422. As understood from FIG. 5, a space in which the opening 322 of the flow path substrate 32 and the accommodating portion 422 of the housing portion 42 communicate with each other functions as a liquid storage chamber (reservoir) R. The ink supplied from the liquid container 14 and passing through the inlet 424 is stored in the liquid storage chamber R.

  The vibration absorber 48 is an element for absorbing pressure fluctuation in the liquid storage chamber R, and includes, for example, a flexible sheet member (compliance substrate) that can be elastically deformed. Specifically, the Z direction of the flow path substrate 32 is configured such that the opening 322, the relay flow path 328, and the plurality of supply flow paths 324 of the flow path substrate 32 are closed to form the bottom surface of the liquid storage chamber R. A vibration absorber 48 is installed on the positive surface of the.

  As illustrated in FIGS. 4 and 5, the pressure chamber substrate 34 is a plate-like member in which a plurality of pressure chambers C corresponding to different nozzles N are formed. The plurality of pressure chambers C are arranged along the Y direction. Each pressure chamber C (cavity) is a long opening along the X direction in plan view. The end of the pressure chamber C on the positive side in the X direction overlaps with one supply channel 324 of the flow path substrate 32 in a plan view, and the end of the pressure chamber C on the negative side in the X direction is in the plan view It overlaps with one communication channel 326 of 32.

A diaphragm 36 is installed on the surface of the pressure chamber substrate 34 opposite to the flow path substrate 32. The diaphragm 36 is a plate-like member that can be elastically deformed. As illustrated in FIG. 5, the diaphragm 36 according to the first embodiment is configured by stacking a first layer 361 and a second layer 362. The second layer 362 is located on the side opposite to the pressure chamber substrate 34 when viewed from the first layer 361. The first layer 361 is an elastic film formed of an elastic material such as silicon oxide (SiO ₂ ), and the second layer 362 is an insulating film formed of an insulating material such as zirconium oxide (ZrO ₂ ). In addition, by selectively removing a part of the plate-like member having a predetermined plate thickness in the plate thickness direction from the region corresponding to the pressure chamber C, the pressure chamber substrate 34 and a part or all of the diaphragm 36 are removed. It is also possible to form it integrally.

  As understood from FIG. 5, the flow path substrate 32 and the vibration plate 36 face each other with an interval inside each pressure chamber C. The pressure chamber C is a space that is located between the flow path substrate 32 and the vibration plate 36 and applies pressure to the ink filled in the pressure chamber C. The ink stored in the liquid storage chamber R branches from the relay flow path 328 to each supply flow path 324 and is supplied and filled in the plurality of pressure chambers C in parallel. As understood from the above description, the diaphragm 36 constitutes the wall surface of the pressure chamber C (specifically, the upper surface which is one surface of the pressure chamber C).

  As illustrated in FIGS. 4 and 5, the surface of the diaphragm 36 opposite to the pressure chamber C (that is, the surface of the second layer 362) corresponds to a different nozzle N (or pressure chamber C). A plurality of piezoelectric elements 38 are installed. Each piezoelectric element 38 is an actuator that is deformed by the supply of the drive signal D, and is formed in a long shape along the X direction in plan view. The longitudinal direction of the piezoelectric element 38 may be defined as the X direction. The plurality of piezoelectric elements 38 are arranged in the Y direction so as to correspond to the plurality of pressure chambers C. When the vibration plate 36 vibrates in conjunction with the deformation of the piezoelectric element 38, the pressure in the pressure chamber C fluctuates, so that the ink filled in the pressure chamber C is ejected through the communication channel 326 and the nozzle N. Is done. One injection unit 261 illustrated in FIG. 4 is a part including the piezoelectric element 38, the diaphragm 36, and a flow path from the pressure chamber C to the nozzle N.

  4 and 5 is a structure that protects the plurality of piezoelectric elements 38 and reinforces the mechanical strength of the pressure chamber substrate 34 and the diaphragm 36. For example, the sealing body 44 is bonded to the surface of the diaphragm 36. It is fixed with an agent. A plurality of piezoelectric elements 38 are accommodated inside a concave portion formed on the surface of the sealing body 44 facing the diaphragm 36.

  As illustrated in FIG. 5, for example, a wiring substrate 50 is bonded to the surface of the vibration plate 36 (or the surface of the pressure chamber substrate 34). The wiring board 50 is a mounting component on which a plurality of wirings (not shown) for electrically connecting the control unit 20 or the power supply circuit (not shown) and the liquid jet head 26 are formed. For example, a flexible wiring board 50 such as FPC (Flexible Printed Circuit) or FFC (Flexible Flat Cable) is preferably employed. A drive signal D for driving the piezoelectric elements 38 is supplied from the wiring board 50 to each piezoelectric element 38.

  A specific configuration of each piezoelectric element 38 will be described in detail below. FIG. 6 is a plan view of the plurality of piezoelectric elements 38. In FIG. 6, the outline of an element located on the back side of any one element (originally a part hidden by the element on the near side) is also shown by a solid line for convenience. 7 is a sectional view taken along line VII-VII in FIG. 6 (cross section along the longitudinal direction of the piezoelectric element 38), and FIG. 8 is a sectional view taken along line VIII-VIII in FIG. Cross section along hand direction).

  As illustrated in FIG. 6 to FIG. 8, the piezoelectric element 38 is generally configured by stacking a first electrode 51, a piezoelectric layer 52, and a second electrode 53. The piezoelectric layer 52 is deformed according to the voltage applied between the first electrode 51 and the second electrode 53. That is, the portion where the first electrode 51 and the second electrode 53 face each other with the piezoelectric layer 52 interposed therebetween functions as the piezoelectric element 38. Piezoelectric elements 38 are individually formed for each pressure chamber C (or for each nozzle N). Specifically, a plurality of piezoelectric elements 38 formed in a long shape in the X direction are arranged in the Y direction at intervals.

  In the present specification, the expression “element A and element B are stacked” is not intended to limit the configuration in which element A and element B are in direct contact with each other. That is, a configuration in which another element C is interposed between the element A and the element B is also included in the concept that “the element A and the element B are stacked”. Similarly, the expression “element B is formed on the surface of element A” is not limited to a configuration in which element A and element B are in direct contact with each other. That is, even in a configuration in which the element C is formed on the surface of the element A and the element B is formed on the surface of the element C, if “at least part of the element A and the element B overlap in a plan view” The element B is formed on the surface of “

  The first electrode 51 is formed on the surface of the diaphragm 36 (specifically, the surface of the second layer 362). The first electrode 51 is an individual electrode formed so as to be separated from each other for each piezoelectric element 38. Specifically, a plurality of first electrodes 51 extending in the X direction are arranged in the Y direction at intervals. The material or manufacturing method of the first electrode 51 is arbitrary. For example, the first electrode 51 can be formed by forming a thin film of various conductive materials by a known film formation technique such as sputtering and selectively removing the thin film by a known processing technique such as photolithography. Is possible. A drive signal D for controlling ejection of ink from the nozzle N corresponding to the piezoelectric element 38 is applied to the first electrode 51 of each piezoelectric element 38 via the wiring board 50.

  The piezoelectric layer 52 is formed on the surface of the first electrode 51. The piezoelectric layer 52 is a strip-shaped dielectric film extending in the Y direction so as to be continuous over the plurality of piezoelectric elements 38. The material or manufacturing method of the piezoelectric layer 52 is arbitrary. For example, a piezoelectric material layer 52 is formed by forming a thin film of a piezoelectric material such as lead zirconate titanate by a known film forming technique such as sputtering and selectively removing the thin film by a known processing technique such as photolithography. Can be formed. As illustrated in FIG. 6, a notch 521 (slit) elongated in the X direction is formed in a region corresponding to the gap between the pressure chambers C adjacent to each other in the piezoelectric layer 52 in plan view. According to the above configuration, each piezoelectric element 38 is individually deformed for each pressure chamber C, and the propagation of vibration between the piezoelectric elements 38 is suppressed. Therefore, it is possible to control the ejection characteristics (for example, ejection amount, ejection direction, or ejection speed) of the ink by each nozzle N with high accuracy.

  As illustrated in FIG. 8, when attention is paid to a cross section (YZ plane) orthogonal to the longitudinal direction of the piezoelectric element 38, the vibration plate 36 does not overlap the piezoelectric layer 52 (hereinafter referred to as “support portion”) 364. Is included on both sides of the piezoelectric layer 52. The piezoelectric element 38 is supported on the pressure chamber substrate 34 by the support portion 364.

  The second electrode 53 is formed on the surface of the piezoelectric layer 52. The material or manufacturing method of the second electrode 53 is arbitrary. For example, the second electrode 53 can be formed by forming a thin film of various conductive materials by a known film formation technique such as sputtering and selectively removing the thin film by a known processing technique such as photolithography. Is possible.

  As illustrated in FIGS. 6 and 7, the second electrode 53 includes two first divided electrodes 61 and one second divided electrode 62. Each of the plurality of first divided electrodes 61 is a strip-like electrode extending in the Y direction with a space between each other. The electrode widths (dimensions in the X direction) of the two first divided electrodes 61 are common. The second divided electrode 62 is a belt-like electrode extending in the Y direction within the interval between the two first divided electrodes 61. Each of the first divided electrode 61 and the second divided electrode 62 is a common electrode that is continuous over a plurality of piezoelectric elements 38 (or a plurality of pressure chambers C). Each first divided electrode 61 and second divided electrode 62 are formed to be separated from each other and electrically insulated. The second divided electrode 62 is narrower than the first divided electrode 61.

  A first conductor 55 and a second conductor 56 are formed on the surface of the second electrode 53. The first conductor 55 is a strip-like conductive film extending in the Y direction along the edge of the first divided electrode 61 on the negative side in the X direction. The second conductor 56 is a strip-like conductive film extending in the Y direction along the edge of the first divided electrode 61 on the positive side in the X direction. The first conductor 55 and the second conductor 56 are formed from the same layer using a low-resistance conductive material such as gold (Au). By forming the first conductor 55 and the second conductor 56, a voltage drop in each first divided electrode 61 is suppressed. The first conductor 55 and the second conductor 56 also function as weights for suppressing deformation of the diaphragm 36 and the piezoelectric element 38.

  6 and 7, the piezoelectric element 38 is divided into two first portions P1 and one second portion P2 in a plan view. Each of the two first portions P1 is a portion of the piezoelectric element 38 that overlaps the first divided electrode 61 in plan view. In other words, each first portion P 1 is formed by stacking the first electrode 51, the piezoelectric layer 52, and the first divided electrode 61. On the other hand, the second portion P2 is a portion of the piezoelectric element 38 that overlaps the second divided electrode 62 in plan view. That is, the second portion P 2 is configured by a stack of the first electrode 51, the piezoelectric layer 52, and the second divided electrode 62. As described above, the second divided electrode 62 is located within the interval between the two first divided electrodes 61. Accordingly, the second portion P2 is located within the interval between the two first portions P1 arranged in the X direction. That is, each first portion P1 is formed on both sides in the X direction when viewed from the second portion P2. As understood from FIGS. 6 and 7, the second portion P2 is located closer to the center of the piezoelectric element 38 than the first portion P1 in the X direction. Specifically, a predetermined length section including the midpoint between both ends in the X direction of the piezoelectric element 38 corresponds to the second portion P2.

  The reference voltage Vbs1 generated by the signal generator 202 is supplied to each first divided electrode 61. A drive signal D is supplied to the first electrode 51. Therefore, a voltage corresponding to the difference between the reference voltage Vbs1 and the drive signal D is applied to each first portion P1 of the piezoelectric element 38. On the other hand, the reference voltage Vbs <b> 2 generated by the signal generation unit 202 is supplied to the second divided electrode 62. Therefore, a voltage corresponding to the difference between the reference voltage Vbs2 and the drive signal D is applied to the second portion P2 of the piezoelectric element 38. As described above, different voltages are applied to the first portion P1 and the second portion P2 of the piezoelectric element 38, respectively.

  As illustrated in FIG. 2, the signal generation unit 202 and the drive circuit 262 function as the element drive unit 28 that applies a voltage to the piezoelectric element 38. The diaphragm 36, the piezoelectric element 38, and the element driving unit 28 function as a piezoelectric device. The liquid ejecting head 26 includes a pressure chamber C that stores ink, and a piezoelectric device that ejects ink from the pressure chamber C.

  FIG. 9 is a waveform diagram of voltages applied to the first portion P1 and the second portion P2 of the piezoelectric element 38. As shown in FIG. That is, the voltage applied to the first portion P 1 is a voltage between the first electrode 51 and the first divided electrode 61. The voltage applied to the second portion P <b> 2 is a voltage between the first electrode 51 and the second divided electrode 62. A state in which the voltage of the first electrode 51 is higher than the voltage of the second electrode 53 (the first divided electrode 61 and the second divided electrode 62) is assumed to be positive.

  As illustrated in FIG. 9, the voltage applied to the first portion P1 of the piezoelectric element 38 varies between the voltage V1 and the voltage V2. The voltage V1 exceeds the voltage V2 (V1> V2). The voltage V1 (example of the first voltage) corresponds to the voltage VH of the drive signal D, and the voltage V2 (example of the second voltage) corresponds to the voltage VL of the drive signal D. On the other hand, the voltage applied to the second portion P2 of the piezoelectric element 38 varies between the voltage V3 and the voltage V4. The voltage V3 exceeds the voltage V4 (V3> V4). The voltage V3 (example of the third voltage) corresponds to a voltage higher than the voltage VH of the drive signal D by the absolute value of the reference voltage Vbs2, and the voltage V4 (example of the fourth voltage) is the voltage VL of the drive signal D. This corresponds to a voltage that is higher than the absolute value of the reference voltage Vbs2.

  FIG. 10 is a graph showing the relationship between the applied voltage in the piezoelectric element 38 and the strain amount of the piezoelectric element 38. The coercive voltage Vc (−) in FIG. 10 is a negative voltage at which the distortion amount of the piezoelectric element 38 is minimized (zero). Further, the maximum voltage Vmax in FIG. 10 is a positive voltage that maximizes the amount of distortion of the piezoelectric element 38. As illustrated in FIG. 10, the voltage range (V1 to V2) applied to the first portion P1 of the piezoelectric element 38 and the voltage range (V3 to V4) applied to the second portion P2 are equal to each other. It is included in a range between the voltage Vc (−) and the maximum voltage Vmax.

  Specifically, the voltage V1 and the voltage V3 are positive voltages opposite to the coercive voltage Vc (−) within the range of the maximum voltage Vmax or less. The voltage V1 is lower than the voltage V3. The voltage V2 is a voltage between the coercive voltage Vc (−) and the voltage V1, and the voltage V4 is a voltage between the coercive voltage Vc (−) and the voltage V3. As understood from the above description, the voltage applied to the first portion P1 of the piezoelectric element 38 includes the voltage V2 between the negative coercive voltage Vc (-) and the positive voltage V1, and the voltage V1. Fluctuates between. Similarly, the voltage applied to the second portion P2 of the piezoelectric element 38 varies between the voltage V4 between the negative coercive voltage Vc (−) and the positive voltage V3 and the voltage V3. . As illustrated above, the drive circuit 262 of the first embodiment applies a voltage that fluctuates between the voltage V1 and the voltage V2 to the first portion P1 of each piezoelectric element 38, and between the voltage V3 and the voltage V4. Is applied to the second portion P 2 of each piezoelectric element 38.

As understood from FIG. 10, the voltage V2 is closer to the coercive voltage Vc (−) than the voltage V4. Since the coercive voltage Vc (−) is a negative voltage as described above, the voltage V2 is lower than the voltage V4. That is, the following equation (1) is established among the voltage V2, the voltage V4, and the coercive voltage Vc (−). The voltages V1 and V3 are opposite in polarity (ie, positive polarity) to the coercive voltage Vc (−), but the polarities of the voltages V2 and V4 are arbitrary.
| Vc (−) − V2 | ≦ | Vc (−) − V4 | (1)

  FIG. 11 is an explanatory diagram of the amount of displacement of the diaphragm 36 in accordance with the voltage applied to the piezoelectric element 38. In the first embodiment, it is assumed that the amount of displacement of the diaphragm 36 toward the pressure chamber C is larger as the voltage applied to the piezoelectric element 38 is higher. The region of the diaphragm 36 corresponding to the first portion P1 includes a displacement amount Dmax1 when the voltage V1 is applied to the first portion P1, and a displacement amount Dmin1 when the voltage V2 is applied to the first portion P1. Vibrate between. Similarly, the region of the diaphragm 36 corresponding to the second portion P2 has a displacement amount Dmax2 when the voltage V3 is applied to the second portion P2, and a displacement when the voltage V4 is applied to the second portion P2. It oscillates between the quantity Dmin2.

  As described above, since the voltage V1 is lower than the voltage V3, the displacement amount Dmax2 is larger than the displacement amount Dmax1. Further, since the voltage V2 is lower than the voltage V4, the displacement amount Dmin2 is larger than the displacement amount Dmin1. That is, the range (Dmin1 to Dmax1) in which the region corresponding to the first portion P1 of the diaphragm 36 is displaced is larger than the range (Dmin2 to Dmax2) in which the region corresponding to the second portion P2 is displaced. It is located on the C side (that is, the side opposite to the piezoelectric element 38).

  As described above, in the first embodiment, a voltage that varies between the voltage V1 and the voltage V2 is applied to the first portion P1 of the piezoelectric element 38, and the second portion P2 of the piezoelectric element 38 is applied to the second portion P2. A voltage that varies between the voltage V3 and the voltage V4 is applied. The voltage V2 is closer to the coercive voltage Vc (-) than the voltage V4. Accordingly, as described in detail below, there is an advantage that the possibility of cracks occurring in the diaphragm 36 can be reduced.

  In the configuration in which a voltage equivalent to that of each first portion P1 is applied to the second portion P2 of the piezoelectric element 38 (hereinafter referred to as “proportional”), the region corresponding to the second portion P2 of the diaphragm 36 is shown in FIG. The vibration is performed with the displacement amount Dmin1 exemplified in the above as an end point. Therefore, there is a problem that the pressure acting on the vibration plate 36 from the ink in the pressure chamber C is large, and cracks of the vibration plate 36 due to the pressure are likely to occur. In contrast to the proportionality, in the first embodiment, a voltage that varies between the voltage V3 and the voltage V4 is applied to the second portion P2. Accordingly, the region of the diaphragm 36 corresponding to the second portion P2 vibrates with the displacement amount Dmin2 corresponding to the voltage V4 (that is, the position closer to the pressure chamber C than the region corresponding to the first portion P1) as an end point. According to the above configuration, the pressure applied from the ink in the pressure chamber C to the region corresponding to the second portion P2 of the diaphragm 36 is suppressed as compared with the comparative example. Therefore, according to the first embodiment, it is possible to reduce the possibility that a crack is generated in the vibration plate 36 due to the pressure from the ink in the pressure chamber C as compared with the comparative example.

  There is a tendency that cracks of the diaphragm 36 are likely to occur near the center in the longitudinal direction of the piezoelectric element 38. In the first embodiment, since the second portion P2 of the piezoelectric element 38 is located closer to the center side of the piezoelectric element 38 than the first portion P1, the portion of the diaphragm 36 that is particularly susceptible to cracking is effectively protected. There is an advantage that you can.

  In the first embodiment, the drive signal D is supplied to the first electrode 51 extending over both the first portion P1 and the second portion P2, the reference voltage Vbs1 is applied to the first divided electrode 61, and the second divided electrode is applied. A reference voltage Vbs2 is applied to 62. That is, the drive signal D is shared by the first part P1 and the second part P2 of the piezoelectric element 38. Therefore, there is an advantage that the configuration and operation of the element driving unit 28 are simplified as compared with the configuration in which separate driving signals are used in the first portion P1 and the second portion P2. However, the first part P1 and the second part P2 may be driven by separate drive signals.

Second Embodiment
FIG. 12 is a graph showing the relationship between the voltage applied to the piezoelectric element 38 and the amount of strain in the second embodiment. The coercive voltage Vc (+) in FIG. 12 is a positive voltage at which the distortion amount of the piezoelectric element 38 is minimized (zero). Further, the minimum voltage Vmin in FIG. 12 is a negative voltage that maximizes the amount of distortion of the piezoelectric element 38. As illustrated in FIG. 12, in the second embodiment, the voltage range (V1 to V2) applied to the first portion P1 of the piezoelectric element 38 and the voltage range (V3 to V4) applied to the second portion P2. ) Is included in a range between the coercive voltage Vc (+) and the minimum voltage Vmin.

  Specifically, the voltage V1 and the voltage V3 are negative voltages opposite to the coercive voltage Vc (+) within the range of the minimum voltage Vmin or more. The voltage V1 is higher than the voltage V3. The voltage V2 is a voltage between the coercive voltage Vc (+) and the voltage V1, and the voltage V4 is a voltage between the coercive voltage Vc (+) and the voltage V3. As understood from the above description, the voltage applied to the first portion P1 of the piezoelectric element 38 includes the voltage V2 between the positive coercive voltage Vc (+) and the negative voltage V1, and the voltage V1. Fluctuates between. Similarly, the voltage applied to the second portion P2 of the piezoelectric element 38 varies between the voltage V4 between the positive coercive voltage Vc (+) and the negative voltage V3 and the voltage V3. . As illustrated above, the drive circuit 262 of the second embodiment applies a voltage that varies between the voltage V1 and the voltage V2 to the first portion P1 of each piezoelectric element 38, and between the voltage V3 and the voltage V4. Is applied to the second portion P 2 of each piezoelectric element 38.

As understood from FIG. 12, the voltage V2 is closer to the coercive voltage Vc (+) than the voltage V4. Since the coercive voltage Vc (+) is a positive voltage as described above, the voltage V2 is higher than the voltage V4. That is, the following equation (2) is established among the voltage V2, the voltage V4, and the coercive voltage Vc (+). The voltages V1 and V3 are opposite in polarity (ie, negative polarity) to the coercive voltage Vc (+), but the polarities of the voltages V2 and V4 are arbitrary.
| Vc (+) − V2 | ≦ | Vc (+) − V4 | (2)

  As described above, in the second embodiment, a voltage that varies between the voltage V1 and the voltage V2 is applied to the first portion P1 of the piezoelectric element 38, and the second portion P2 of the piezoelectric element 38 is applied to the second portion P2. A voltage that varies between the voltage V3 and the voltage V4 is applied. The voltage V2 is closer to the coercive voltage Vc (+) than the voltage V4. Therefore, as in the first embodiment, there is an advantage that the possibility of cracks occurring in the vicinity of the second portion P2 of the diaphragm 36 can be reduced.

  As will be understood from the illustrations of the first embodiment and the second embodiment, the drive circuit 262 determines whether the first polarity coercive voltage Vc (Vc (−), Vc (+)) and the first polarity of the piezoelectric element 38 are the same. A voltage V2 between the opposite second polarity voltage V1 and a voltage varying within the range between the voltage V1 are applied to the first portion P1, and the coercive voltage Vc and the second polarity voltage V3 are And a voltage that varies within a range between the voltage V3 and the voltage V3 are comprehensively expressed as elements that are applied to the second portion P2.

<Modification>
Each form illustrated above can be variously modified. Specific modes of modifications that can be applied to the above-described embodiments are exemplified below. Note that two or more aspects arbitrarily selected from the following examples can be appropriately combined as long as they do not contradict each other.

(1) In each of the embodiments described above, the piezoelectric element 38 is divided into three parts (two first parts P1 and one second part P2) in the longitudinal direction. It is not limited to the illustration. For example, as illustrated in FIG. 13, the piezoelectric element 38 may be divided into four or more portions P. FIG. 13 illustrates a configuration in which the piezoelectric element 38 is divided into five portions P. Regardless of the total number of sections of the piezoelectric element 38, the applied voltage at which the amount of distortion becomes the minimum in the portion P closer to the end of the piezoelectric element 38 is set to a voltage close to the coercive voltage Vc. For example, in a configuration in which a voltage between the negative coercive voltage Vc (−) and the positive maximum voltage Vmax is applied to the piezoelectric element 38, the voltage range applied to each portion P of the piezoelectric element 38 is X The portion P closer to the end in the direction becomes a range closer to the coercive voltage Vc (−). On the other hand, in the configuration in which a voltage between the positive coercive voltage Vc (+) and the negative minimum voltage Vmin is applied to the piezoelectric element 38, the voltage range applied to each portion P of the piezoelectric element 38 is X The portion P closer to the end in the direction becomes a range closer to the coercive voltage Vc (+).

(2) In each of the above embodiments, the first electrode 51 is an individual electrode, and the second electrode 53 (the first divided electrode 61 and the second divided electrode 62) is a common electrode. May be a common electrode continuous across a plurality of piezoelectric elements 38, and the second electrode 53 may be an individual electrode for each piezoelectric element 38. Further, both the first electrode 51 and the second electrode 53 may be individual electrodes. According to the configuration in which the second electrode 53 (the first divided electrode 61 and the second divided electrode 62) is a common electrode, compared to the configuration in which the second electrode 53 is individually formed for each piezoelectric element 38, There is an advantage that the configuration of the liquid jet head 26 is simplified.

(3) In the above-described embodiments, the voltage V1 applied to the first portion P1 and the voltage V3 applied to the second portion P2 of the piezoelectric element 38 are different from each other, but the voltage V1 and the voltage V3 are the same. You may let them. For example, both the voltage V1 and the voltage V3 may be set to the maximum voltage Vmax or the minimum voltage Vmin. In each of the above-described embodiments, the voltage V2 and the coercive voltage Vc are made different from each other, but the voltage V2 may be made to coincide with the coercive voltage Vc.

(4) In each of the above-described embodiments, the serial-type liquid ejecting apparatus 100 that reciprocates the transport body 242 on which the liquid ejecting head 26 is mounted has been exemplified. The present invention can also be applied to an injection device.

(5) The liquid ejecting apparatus 100 exemplified in each of the above-described embodiments can be employed in various apparatuses such as a facsimile apparatus and a copying machine in addition to an apparatus dedicated to printing. However, the use of the liquid ejecting apparatus of the present invention is not limited to printing. For example, a liquid ejecting apparatus that ejects a solution of a coloring material is used as a manufacturing apparatus that forms a color filter of a liquid crystal display device. Further, a liquid ejecting apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus that forms wiring and electrodes of a wiring board.

(6) The piezoelectric device including the diaphragm 36, the piezoelectric element 38, and the element driving unit 28 is not limited to the liquid ejecting head 26, but may be applied to other devices such as an ultrasonic sensor, an ultrasonic transducer, or an ultrasonic motor. Can be applied.

DESCRIPTION OF SYMBOLS 100 ... Liquid ejecting apparatus, 12 ... Medium, 14 ... Liquid container, 20 ... Control unit, 22 ... Conveyance mechanism, 24 ... Transfer mechanism, 26 ... Liquid ejecting head, 32 ... Flow path substrate, 34 ... Pressure chamber substrate, 342 ... Removal part, 36 ... vibration plate, 38 ... piezoelectric element, 42 ... housing part, 44 ... sealing body, 46 ... nozzle plate, N ... nozzle, 48 ... vibration absorber, 50 ... wiring board, 51 ... first electrode, 52 ... piezoelectric layer, 53 ... second electrode, 61 ... first divided electrode, 62 ... second divided electrode, C ... pressure chamber, R ... liquid storage chamber, P1 ... first portion, P2 ... second portion.

Claims (7)

A pressure chamber containing liquid;
A diaphragm constituting a wall surface of the pressure chamber;
A piezoelectric element formed on the diaphragm;
A liquid ejecting head comprising a drive circuit for applying a voltage to the piezoelectric element,
The piezoelectric element includes a first portion and a second portion formed at different positions in plan view,
The drive circuit is
A voltage that fluctuates within a range between the second voltage between the coercive voltage of the first polarity of the piezoelectric element and the first voltage of the second polarity opposite to the first polarity, and the first voltage. Applying to the first part,
Applying a fourth voltage between the coercive voltage and the third voltage of the second polarity and a voltage varying within a range between the third voltage to the second portion;
The liquid ejection head, wherein the second voltage is closer to the coercive voltage than the fourth voltage. The piezoelectric element is formed in an elongated shape in plan view,
The liquid ejecting head according to claim 1, wherein the second portion is positioned closer to the center of the piezoelectric element than the first portion in the longitudinal direction of the piezoelectric element. The liquid ejecting head according to claim 2, wherein the first portion is formed on both sides in the longitudinal direction of the piezoelectric element when viewed from the second portion. The piezoelectric element is
A first electrode and a second electrode;
A piezoelectric layer interposed between the first electrode and the second electrode,
The second electrode includes a first divided electrode and a second divided electrode,
The first portion is a portion in which the first electrode, the piezoelectric layer, and the first divided electrode are stacked, and the second portion is the first electrode, the piezoelectric layer, and the second divided portion. It is the part where the electrode is laminated,
The drive circuit is
Supplying a time-varying drive signal to the first electrode;
Supplying a first reference voltage to the first split electrode;
4. The liquid jet head according to claim 1, wherein a second reference voltage lower than the first reference voltage is supplied to the second divided electrode. 5. The liquid ejecting head according to claim 4, wherein the second electrode is a common electrode continuous across a plurality of piezoelectric elements.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1. A diaphragm,
A piezoelectric element formed on the diaphragm;
A piezoelectric device comprising a drive circuit for applying a voltage to the piezoelectric element,
The piezoelectric element includes a first portion and a second portion formed at different positions in plan view,
The drive circuit is
A voltage that fluctuates within a range between the second voltage between the coercive voltage of the first polarity of the piezoelectric element and the first voltage of the second polarity opposite to the first polarity, and the first voltage. Applying to the first part,
Applying a fourth voltage between the coercive voltage and the third voltage of the second polarity and a voltage varying within a range between the third voltage to the second portion;
The piezoelectric device, wherein the second voltage is closer to the coercive voltage than the fourth voltage.

Images