Liquid dispensing head

Abstract

To provide a liquid discharge head which allows repolarization processing to be performed after mounting a control component.SOLUTION: A liquid discharge head comprises an actuator, a diaphragm and an electronic component. The actuator includes piezoelectric layers and electrodes that are alternately laminated. The diaphragm is arranged opposite to the actuator. The electronic component is connected to the actuator. The liquid discharge head satisfies B / A≥C, in which A [mm] denotes the thickness of one piezoelectric layer of the actuator, B [V] denotes an upper limit voltage of the electronic component, and C [V / mm] denotes a polarization electric field of a piezoelectric material forming the piezoelectric layer under a condition of a heat-resistant temperature of the electronic component.SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] Embodiments of the present invention relate to a liquid discharge head. [[Background Art]]

[0002] As one type of inkjet head system, a system that ejects ink using deformation of a piezoelectric material such as PZT is used. Factors that cause variations in the piezoelectric properties of piezoelectric members, which affect printing quality, include variations in the piezoelectric properties of raw material lots and deterioration during processing in the manufacturing stage, and aging degradation in the operation stage after mounting on an actual device and distribution to the market. As a countermeasure against variations in piezoelectric properties, repolarization treatment of piezoelectric materials has been proposed. It has also been proposed to improve product yield by, as adjustment of the polarization amount, once eliminating the polarization of each piezoelectric element and then performing repolarization treatment. However, after mounting control components such as substrates and electronic components, the direction and magnitude of applicable voltage are limited, so maintenance by repolarization treatment is difficult. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. Hei 9-141859 [[Patent Document 2]] Japanese Unexamined Patent Publication No. Hei 10-193601 [[Patent Document 3]] Japanese Unexamined Patent Publication No. Hei 11-147312 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] The problem to be solved by the present invention is to provide a liquid discharge head that can be subjected to repolarization treatment after mounting of control components. [[Means for Solving the Problem]]

[0005] A liquid discharge head according to one embodiment includes alternately stacked3 or more layers An actuator having a piezoelectric layer and electrodes, a diaphragm positioned opposite the actuator, and a connection to the actuator. Driver IC It is equipped with the following. With the drive IC mounted, the actuator is configured to allow repolarization by applying a voltage to the piezoelectric layer via the drive IC, and when the thickness of one layer of the piezoelectric layer of the actuator is A [mm], the upper limit voltage of the drive IC is B [V], and the polarization electric field required to polarize the piezoelectric material constituting the piezoelectric layer under the conditions of 80°C, which is the heat resistance temperature of the drive IC, is C [V / mm], then B / A ≥ C is satisfied. [Brief explanation of the drawing]

[0006] [Figure 1] A cross-sectional view showing the configuration of an inkjet head according to the first embodiment. [Figure 2] A cross-sectional view showing the configuration of the inkjet head. [Figure 3] An explanatory diagram showing the schematic configuration of an inkjet recording apparatus according to the first embodiment. [Figure 4] A cross-sectional view showing the configuration of an inkjet head according to another embodiment. [Modes for carrying out the invention]

[0007] The inkjet head 1, which is a liquid ejection head, and the inkjet recording device 100, which is a liquid ejection device, according to the first embodiment will be described below with reference to Figures 1 to 3. Figures 1 and 2 are cross-sectional views showing the schematic configuration of the inkjet head 1, and Figure 3 is an explanatory diagram showing the schematic configuration of the inkjet recording device 100. In the figures, arrows X, Y, and Z indicate three mutually orthogonal directions, respectively. For explanatory purposes, the configuration in each figure is enlarged, reduced, or omitted as appropriate.

[0008] As shown in Figures 1 and 2, the inkjet head 1 comprises a base 10, a plurality of actuator units 20, a flow channel member 40, a nozzle plate 50 having a plurality of nozzles 51, a frame unit 60 as a structural part, and a drive circuit 70. As an example, the inkjet head 1 has two actuator units 20, and has two rows each of nozzle rows in which a plurality of nozzles 51 are arranged in the row direction (X direction), pressure chamber rows in which a plurality of pressure chambers 31 are arranged in the row direction, and element rows in which a plurality of piezoelectric elements 21, 22 are arranged in the row direction. In this embodiment, an example is shown in which the stacking direction of the piezoelectric body layer 211, the vibration direction of the piezoelectric element 21, and the vibration direction of the diaphragm 30 are all along the Z direction.

[0009] The base 10 is formed, for example, in the shape of a rectangular plate.

[0010] The actuator unit 20 is joined to one side of the base 10. Multiple actuator units 20 are provided in parallel on the base 10, for example.

[0011] Each actuator unit 20 comprises, for example, a plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22, which are made of piezoelectric material and arranged alternately along the row direction as actuators, and a piezoelectric structure 26 that integrally connects these plurality of piezoelectric elements 21 and 22 on the base 10 side.

[0012] In each actuator section 20, the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22 are arranged in one direction at regular intervals.

[0013] As an example, the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22 are all configured as rectangular columnar shapes with the same external shape. The actuator section 20 is divided into multiple sections by multiple grooves 23, and the multiple driving piezoelectric elements 21 and non-driving piezoelectric elements 22 are all arranged in rows at the same pitch by grooves 23 of the same width.

[0014] For example, when forming the groove 23 from one side in the Z-direction of the laminated piezoelectric member, by setting the depth of the groove 23 to be shorter than the total length of the laminated piezoelectric member in the Z-direction and leaving the piezoelectric structure portion 26, a shape in which one end side is divided into a plurality of parts and the other end side is connected can be obtained.

[0015] For example, the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are each configured in a rectangular shape in a plan view viewed from the Z-direction, wherein the short-side direction follows the column direction of the element row, and the long-side direction follows an extending direction orthogonal to the column direction and the Z-direction.

[0016] The driving piezoelectric elements 21 are arranged at positions respectively facing the plurality of pressure chambers 31 formed in the flow path member 40 in the Z-direction. As an example, the center positions of the driving piezoelectric element 21 in the column direction and the extending direction, and the center positions of the pressure chamber 31 in the column direction and the extending direction are arranged side by side in the Z-direction.

[0017] The non-driving piezoelectric elements 22 are arranged at positions respectively facing the plurality of partition wall portions 42 formed in the flow path member 40 in the Z-direction. As an example, the center positions of the driving piezoelectric element 21 in the column direction and the extending direction, and the center positions of the partition wall portion 42 in the column direction and the extending direction are arranged side by side in the Z-direction.

[0018] For example, the actuator portion 20 forms the groove 23 by dicing a laminated piezoelectric member bonded to the base 10 in advance from an end surface opposite to the base 10 side, thereby forming a plurality of piezoelectric elements formed in a rectangular column shape at predetermined intervals. Then, electrodes and the like are provided on the plurality of formed columnar elements, thereby forming the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 which are alternately arranged. The plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are alternately arranged in parallel with the groove 23 interposed therebetween in the column direction.

[0019] For example, the laminated piezoelectric member constituting the actuator portion 20 is formed by laminating sheet-shaped piezoelectric materials and sintering the laminate.

[0020] The piezoelectric member constituting the driving piezoelectric element 21 and the non-driving piezoelectric element 22 is, for example, a multilayer piezoelectric body. The driving piezoelectric element 21 and the non-driving piezoelectric element 22 include a plurality of stacked piezoelectric layers 211 and internal electrodes 221, 222 formed on the main surface of each piezoelectric layer 211. As an example, the driving piezoelectric element 21 and the non-driving piezoelectric element 22 have the same laminated structure. The driving piezoelectric element 21 and the non-driving piezoelectric element 22 include external electrodes 223 and 224 formed on the surfaces thereof.

[0021] The piezoelectric layer 211 is formed into a thin plate shape from a piezoelectric material such as PZT (lead zirconate titanate) based or lead-free KNN (potassium sodium niobate) based, for example. The plurality of piezoelectric layers 211 are stacked such that their thickness direction coincides with the stacking direction, and are bonded to each other. For example, in the present embodiment, the thickness direction and the stacking direction of the piezoelectric layers 211 are arranged along the vibration direction (Z direction).

[0022] The internal electrodes 221 and 222 are conductive films formed into a predetermined shape from a calcinable conductive material such as silver-palladium. The internal electrodes 221 and 222 are formed in predetermined regions on the main surface of each piezoelectric layer 211. The internal electrodes 221 and 222 have different polarities from each other. For example, one internal electrode 221 extends in the extending direction (Y direction) which is orthogonal to both the column direction (X direction), which is the arrangement direction of the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22, and the vibration direction (Z direction), it is formed in a region reaching one end of the piezoelectric layer 211 but not reaching the other end of the piezoelectric layer 211. The other internal electrode 222 is formed in a region that does not reach one end of the piezoelectric layer 211 but reaches the other end of the piezoelectric layer 211 in the extending direction. The internal electrodes 221 and 222 are respectively connected to the external electrodes 223 and 224 formed on the side surfaces of the piezoelectric elements 21 and 22.

[0023] Furthermore, the laminated piezoelectric members constituting the driving piezoelectric element 21 and the non-driving piezoelectric element 22 are further provided with a dummy layer 212 at either or both of the ends on the base 10 side and the nozzle plate 50 side. The dummy layer 212 is made of the same material as the piezoelectric layer 211, has electrodes on only one side, and does not deform because no electric field is applied to it. For example, the dummy layer 212 does not function as a piezoelectric body, but serves as a base for fixing the actuator part 20 to the base 10, or as a polishing surface for polishing to achieve accuracy during or after assembly.

[0024] The external electrodes 223 and 224 are formed on the surfaces of the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22, and are formed by gathering the ends of the internal electrodes 221 and 222. For example, the external electrodes 223 and 224 are formed on one end face and the other end face in the extending direction of the piezoelectric layer 211, respectively. The external electrodes 223 and 224 are deposited using known methods such as plating or sputtering, using materials such as Ni, Cr, and Au. The external electrodes 223 and 224 are different electrodes. The external electrodes 223 and 224 are arranged on different side surfaces of the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22, respectively. Note that the external electrodes 223 and 224 may be routed to different regions within the same side surface of the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22.

[0025] In this embodiment, as an example, the external electrode 223 is an individual electrode and the external electrode 224 is a common electrode. The external electrode 223, which serves as an individual electrode for the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22, has an electrode layer divided by grooves 23 and is arranged independently of each other. The external electrode 224, which serves as a common electrode, has an electrode layer that is connected to each other, for example, on the side surface of the piezoelectric structure 26, and is grounded, for example. The external electrodes 223 and 224 are connected to the drive circuit 70 via, for example, a wiring film 71. For example, each external electrode 223 and 224 is connected to the control unit 116, which acts as a drive unit, via the drive IC 72 of the drive circuit 70 through the wiring film 71, and is configured to be controllable by control of the control circuit 1161. Note that the arrangement of the common electrode and individual electrodes may be reversed.

[0026] Furthermore, the vibration direction of each piezoelectric element 21 and 22 is aligned with the stacking direction, and when an electric field is applied, they are displaced in the d33 direction.

[0027] Each piezoelectric element 21 and 22 has three or more layers of piezoelectric body layers 211 and internal electrodes 221 and 222. As an example, each piezoelectric element 21 and 22 has three to 50 layers, with each layer having a thickness of 10 μm to 40 μm, and the product of the thickness and total number of layers being less than 1000 μm.

[0028] Each piezoelectric element 21, 22 is configured such that B / A ≥ C, where A [mm] is the thickness of each piezoelectric layer 211 in the stacking direction, B [V] is the upper limit voltage of the electronic component, and C [V / mm] is the polarization electric field required to polarize the piezoelectric material constituting the piezoelectric layer 211 at the heat resistance temperature of the electronic component. The thickness A [mm] of each piezoelectric layer 211 in the stacking direction is, in other words, the thickness of one layer of piezoelectric layer 211.

[0029] Here, the upper limit voltage (maximum input allowable voltage) is the maximum voltage that can be applied to the components to which voltage is applied during the repolarization process among the various electronic components used in discharge control. As an example, the upper limit voltage of the drive IC72 is used.

[0030] For example, if the piezoelectric layer 211 is made of PZT, the upper limit voltage of the mounted electronic component is set to 60V as defined by the drive IC 72, and the heat resistance temperature of the electronic component is 80°C, then the electric field required to polarize the piezoelectric material used in the piezoelectric layer 211 under 80°C conditions will be 3.5kV / mm, and the thickness of each layer of the piezoelectric layer 211 will be 17.1μm or less.

[0031] Due to its structure, the inkjet head 1 can undergo repolarization after assembly using a control system. In other words, by controlling the repolarization process and the resulting piezoelectric constant using a control circuit for ejection control, maintenance can be performed to improve yield during the manufacturing stage and improve print quality during the operation stage.

[0032] The driving piezoelectric element 21 vibrates when a voltage is applied to the internal electrodes 221 and 222 via the external electrodes 223 and 224. In this embodiment, the driving piezoelectric element 21 vibrates longitudinally along the stacking direction of the piezoelectric body layer 211. Here, longitudinal vibration refers to, for example, "vibration in the thickness direction defined by the piezoelectric constant d33". The driving piezoelectric element 21 displaces the diaphragm 30 and deforms the pressure chamber 31 due to the longitudinal vibration.

[0033] The flow path member 40 comprises a diaphragm 30 positioned opposite to one side of the actuator unit 20 in the deformation direction, and a manifold 405 stacked on one side of the diaphragm 30.

[0034] The diaphragm 30 is positioned between the manifold 405 and the actuator 20 in the direction of vibration. Together with the manifold 405, the diaphragm 30 constitutes the flow path member 40.

[0035] The diaphragm 30 extends along a plane perpendicular to the Z-direction, which is the vibration direction, and is joined to one side of the piezoelectric layer 211 of the plurality of piezoelectric elements 21, 22 in the direction of vibration, i.e., the side facing the nozzle plate 50. The diaphragm 30 is configured to be deformable, for example. The diaphragm 30 is joined to the driving piezoelectric element 21 and the non-driving piezoelectric element 22 of the actuator section 20 and to the frame section 60. For example, the diaphragm 30 has a vibration region 301 facing the piezoelectric elements 21, 22 and a support region 302 facing the frame section 60.

[0036] The vibration region 301 is, for example, a flat plate shaped such that its thickness direction is the vibration direction of the piezoelectric layer 211. The diaphragm 30 has a surface direction that extends in the direction of the arrangement of the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22. The diaphragm 30 is, for example, a metal plate. The diaphragm 30 has a plurality of vibrating parts that face each pressure chamber 31 and are individually displaceable. The diaphragm 30 is formed by a plurality of vibrating parts being integrally connected.

[0037] For example, the diaphragm 30 is made of a SUS plate, and its thickness along the vibration direction is set to approximately 5 μm to 15 μm. In addition, the vibration region 301 may have folds or steps formed between vibration parts and adjacent parts, or between mutually adjacent vibration parts, so that multiple vibration parts can be easily displaced. The vibration region 301 is deformed by the displacement of the part positioned opposite the driving piezoelectric element 21 due to the extension and compression of the driving piezoelectric element 21. For example, since the diaphragm 30 requires a very thin and complex shape, it is formed by electroforming or the like. The diaphragm 30 is joined to the upper end surface of the actuator part 20 by adhesive or the like.

[0038] The support region 302 is a plate-shaped member positioned between the frame portion 60 and the manifold 405. The support region 302 has a communication portion 33 with a through hole that communicates with the common chamber 32.

[0039] For example, the communication section 33 includes a filter member having numerous pores through which liquid can pass, acting as a through-hole.

[0040] The manifold 405 is positioned between the nozzle plate 50 and the diaphragm 30 in the direction of vibration. The manifold is joined to one side of the diaphragm 30 in the direction of vibration.

[0041] The manifold 405 comprises a peripheral wall portion 41 joined to the outer edge of the diaphragm 30, a plurality of partition wall portions 42 separating a plurality of ink flow paths 35, and a guide wall 43 forming a guide flow path 34. The manifold 405 forms a predetermined ink flow path 35 having a plurality of pressure chambers 31 separated by the partition wall portions 42, and a guide flow path 34 extending in a second direction from the plurality of pressure chambers 31 toward the communication portion 33 and separated by the partition wall portions 42.

[0042] Within the manifold 405, the multiple pressure chambers 31, which are arranged in parallel in a third direction, are separated by partition walls 42. That is, both sides of the pressure chamber 31 in the third direction are formed by partition walls 42. Each pressure chamber 31 communicates with a nozzle 51 formed on a nozzle plate 50 located on one side. In addition, the pressure chamber 31 is closed off on the opposite side of the nozzle plate 50 by a diaphragm 30.

[0043] The multiple pressure chambers 31 are spaces formed on one side of the vibration region 301 of the diaphragm 30 and communicate with a common chamber 32 via a guide channel 34 and a communication section 33. The multiple pressure chambers 31 communicate with nozzles 51 formed on the nozzle plate 50. The pressure chambers 31 are also blocked on the opposite side of the nozzle plate 50 by the diaphragm 30.

[0044] Multiple pressure chambers 31 hold liquid supplied from a common chamber 32 via a guide channel 34, and the liquid is discharged from the nozzle 51 by deforming due to the vibration of a vibrating plate 30 that forms part of the pressure chamber 31.

[0045] The partition wall 42 separates the multiple pressure chambers 31 arranged in parallel and the multiple guide channels 34 arranged in parallel, and is a wall member that constitutes both sides of the pressure chambers 31 and the guide channels 34. The partition wall 42 is positioned opposite the non-driven piezoelectric element 22 via the diaphragm 30 and is supported by the non-driven piezoelectric element 22. Multiple partition wall sections 42 are provided at the same pitch as the arrangement of the multiple pressure chambers 31.

[0046] The nozzle plate 50 is constructed as a rectangular plate with a thickness of approximately 10 μm to 100 μm, made of a metal such as SUS or Ni, or a resin material such as polyimide. The nozzle plate 50 is positioned on one side of the manifold 405 so as to cover one side of the opening of the pressure chamber 31.

[0047] Multiple nozzles 51 are arranged in the same first direction as the direction in which the pressure chambers 31 are arranged, forming a nozzle row. For example, two rows of nozzles 51 are provided, and each nozzle 51 is positioned to correspond to a plurality of pressure chambers 31 arranged in two rows. In this embodiment, the nozzles 51 are each provided at the end positions in the extension direction of the pressure chambers 31.

[0048] The frame portion 60 is a structure that is joined to the diaphragm 30 together with the piezoelectric elements 21 and 22. The frame portion 60 is provided on the side opposite to the piezoelectric elements 21 and 22, the diaphragm 30, and the manifold 405, and in this embodiment, for example, it is positioned adjacent to the actuator portion 20. The frame portion 60 constitutes the outer casing of the inkjet head 1. The frame portion 60 may also have a liquid flow path formed inside. In this embodiment, the frame portion 60 is joined to the other side of the diaphragm 30 and forms a common chamber 32 between it and the diaphragm 30.

[0049] The common chamber 32 is formed inside the frame portion 60 and communicates with the pressure chamber 31 through a communication portion 33 and a guide channel 34 provided on the diaphragm 30.

[0050] The drive circuit 70 includes a wiring film 71 with one end connected to external electrodes 223 and 224, a drive IC 72 mounted on the wiring film 71, and a printed circuit board 73 mounted on the other end of the wiring film 71.

[0051] The drive circuit 70 drives the drive piezoelectric element 21 by applying a drive voltage to the external electrodes 223 and 224 via the drive IC 72, thereby increasing or decreasing the volume of the pressure chamber 31 and causing droplets to be ejected from the nozzle 51.

[0052] The wiring film 71 is connected to multiple external electrodes 223 and 224. For example, the wiring film 71 is an ACF (anisotropic conductive film) fixed to the connection points of the external electrodes 223 and 224 by thermocompression or the like. The wiring film 71 is, for example, a COF (Chip on Film) on which a drive IC 72 is mounted as an electronic component.

[0053] The drive IC 72 is connected to the external electrodes 223 and 224 via the wiring film 71. The drive IC 72 is an electronic component used for ejection control. Alternatively, the drive IC 72 may be connected to the external electrodes 223 and 224 by means other than the wiring film 71, such as ACP (anisotropic conductive paste), NCF (non-conductive film), and NCP (non-conductive paste).

[0054] The drive IC 72 generates control signals and drive signals to operate each drive piezoelectric element 21. The drive IC 72 generates control signals for control purposes, such as selecting the timing for ejecting ink and which drive piezoelectric element 21 to eject ink, according to the image signal input from the control unit 116 of the inkjet recording device 100 on which the inkjet head 1 is mounted. The drive IC 72 also generates a voltage to be applied to the drive piezoelectric element 21, i.e., a drive signal (electrical signal), according to the control signals from the control unit 116. When the drive IC 72 applies a drive signal to the drive piezoelectric element 21, the drive piezoelectric element 21 is driven to displace the diaphragm 30 and change the volume of the pressure chamber 31. As a result, the ink filled in the pressure chamber 31 generates pressure vibrations. Due to the pressure vibrations, ink is ejected from the nozzle 51 provided in the pressure chamber 31. The inkjet head 1 may be configured to achieve gradation expression by changing the amount of ink droplets that land on one pixel. Alternatively, the inkjet head 1 may be configured to change the amount of ink droplets that land on one pixel by changing the number of times the ink is ejected. Thus, the drive IC 72 is an example of an application unit that applies a drive signal to the drive piezoelectric element 21.

[0055] For example, the drive IC 72 includes a data buffer, a decoder, and a driver. The data buffer stores print data for each drive piezoelectric element 21 in chronological order. The decoder controls the driver for each drive piezoelectric element 21 based on the print data stored in the data buffer. Based on the decoder's control, the driver outputs a drive signal to operate each drive piezoelectric element 21. The drive signal is, for example, a voltage applied to each drive piezoelectric element 21.

[0056] The printed circuit board 73 is a Printing Wiring Assembly (PWA) on which various electronic components and connectors are mounted, and it has a head control circuit 731. The printed circuit board 73 is connected to the control unit 116 of the inkjet recording device 100.

[0057] In the inkjet head 1 configured as described above, the nozzle plate 50, frame portion 60, manifold 405, and diaphragm 30 form an ink flow path having a plurality of pressure chambers 31 communicating with the nozzle 51, a plurality of guide channels 34 communicating with each of the plurality of pressure chambers 31, and a common chamber 32 communicating with the plurality of guide channels 34. For example, the common chamber 32 communicates with the cartridge, and ink is supplied to each pressure chamber 31 through the common chamber 32. All drive piezoelectric elements 21 are connected by wiring so that a voltage can be applied. In the inkjet head 1, for example, when the control unit 116 of the inkjet recording device 100 applies a drive voltage to the electrodes 221 and 222 by the drive IC 72, the drive piezoelectric elements 21 to be driven vibrate, for example, in the stacking direction, that is, in the thickness direction of each piezoelectric body layer 211. In other words, the drive piezoelectric elements 21 vibrate longitudinally.

[0058] Specifically, the control unit 116 applies a drive voltage to the internal electrodes 221 and 222 of the drive piezoelectric element 21 to be driven, thereby selectively driving the drive piezoelectric element 21. By combining the tensile and compressive deformations of the drive piezoelectric element 21, the control unit deforms the diaphragm 30 and changes the volume of the pressure chamber 31, thereby drawing liquid from the common chamber 32 and discharging it from the nozzle 51.

[0059] An example of a manufacturing method for the inkjet head 1 according to this embodiment will be described. First, internal electrodes 221 and 222 are formed on a sheet-shaped piezoelectric material by printing. Then, a plurality of piezoelectric layers 211 having internal electrodes 221 and 222 are stacked, and a firing process and a polarization process are performed to construct a laminated piezoelectric member. At this time, the number of stacked piezoelectric layers 211 is 3 or more, and the thickness of each piezoelectric layer 211 is such that B / A ≥ C is satisfied when the thickness of each piezoelectric layer 211 is A [mm], the upper limit voltage of electronic components such as the drive IC 72 is B [V], and the polarization electric field required at the heat resistance temperature of the electronic components, which is 80°C, is C [V / mm], and the thickness is 10 μm or more. For example, if the piezoelectric layer 211 is made of PZT, the upper limit voltage of the electronic components mounted on the head is 60V as specified by the drive IC 72, the heat resistance temperature is 80°C, and the electric field required when polarization treatment of the piezoelectric material used under 80°C conditions is 3.5kV / mm, then the thickness of each layer of the piezoelectric layer 211 should be 17.1μm or less.

[0060] Then, a laminated piezoelectric member with pre-formed internal electrodes 221 and 222 is placed on the base 10. For example, the laminated piezoelectric member constituting the two actuator sections 20 may be joined to the base 10 as a single unit and then divided into two by groove processing or the like, or the two laminated piezoelectric members constituting the two actuator sections 20 may be prepared separately.

[0061] Next, external electrodes 224 are formed on the two laminated piezoelectric members by printing. Furthermore, multiple grooves 23 are simultaneously formed at a predetermined pitch by dicing or the like, dividing the laminated piezoelectric member into multiple parts to form multiple columnar elements that will become multiple piezoelectric elements 21 and 22 arranged at the same pitch. As a result, multiple driving piezoelectric elements 21 and non-driving piezoelectric elements 22 arranged at the same pitch are formed.

[0062] A wiring film 71, on which electronic components such as a drive IC 72, which serve as control components, are mounted, is connected to the external electrodes 223 and 224, for example, by soldering. Furthermore, a wiring board 73 having a head control circuit 731 is connected to the wiring film 71.

[0063] Then, the diaphragm 30, manifold 405, and nozzle plate 50 are stacked on the actuator unit 20 with a bonding material in between to position them, and the frame unit 60 is placed on the outer circumference of the actuator unit 20, and these multiple members are joined together.

[0064] In the inkjet head 1 configured in this way, if repolarization is required after assembly, the repolarization is performed by applying a voltage to each piezoelectric layer 211 via the internal electrodes 221 and 222 of the piezoelectric elements 21 and 22, using a drive control circuit used for ejection control, while the electronic components are mounted. For example, the conditions for repolarization can be adjusted from an external terminal via the head control circuit 731 and drive IC 72 on the wiring board 73. For example, in the repolarization process, an external power supply is used to control whether or not a voltage is applied to the target electrode and the magnitude of the applied voltage as conditions for the polarization process, thereby controlling the piezoelectric constant.

[0065] An example of an inkjet recording device 100 equipped with an inkjet head 1 will be described below with reference to Figure 3. The inkjet recording device 100 comprises a housing 111, a media supply unit 112, an image forming unit 113, a media discharge unit 114, a transport device 115, and a control unit 116.

[0066] The inkjet recording device 100 is a liquid ejection device that performs image formation processing on paper P by ejecting a liquid such as ink while transporting paper P, for example, as a printing medium, along a predetermined transport path R from the media supply unit 112 through the image forming unit 113 to the media discharge unit 114.

[0067] The housing 111 constitutes the outer casing of the inkjet recording device 100. The housing 111 is provided with an outlet at a predetermined location for ejecting the paper P to the outside.

[0068] The media supply unit 112 is equipped with multiple paper feed cassettes and is configured to hold multiple sheets of paper P of various sizes stacked on top of each other.

[0069] The media discharge unit 114 includes a paper output tray configured to hold the paper P discharged from the discharge port.

[0070] The image forming unit 113 includes a support unit 117 that supports the paper P, and a plurality of head units 130 that are positioned opposite each other above the support unit 117.

[0071] The support unit 117 includes a conveyor belt 118 provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the back, and a plurality of belt rollers 120 provided on the back of the conveyor belt 118.

[0072] During image formation, the support unit 117 supports the paper P on the holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by moving the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0073] The head unit 130 comprises multiple (four-color) inkjet heads 1, ink tanks 132 acting as liquid tanks mounted on each inkjet head 1, a connecting channel 133 connecting the inkjet heads 1 and the ink tanks 132, and a supply pump 134.

[0074] In this embodiment, the system includes four inkjet heads 1 for cyan, magenta, yellow, and black, and ink tanks 132 each containing ink for one of these colors. The ink tanks 132 are connected to the inkjet heads 1 by a connecting channel 133.

[0075] Furthermore, a negative pressure control device, such as a pump (not shown), is connected to the ink tank 132. The negative pressure control device controls the negative pressure inside the ink tank 132 in accordance with the head value between the inkjet head 1 and the ink tank 132, thereby forming the ink supplied to each nozzle 51 of the inkjet head 1 into a predetermined meniscus shape.

[0076] The supply pump 134 is a liquid transfer pump, for example, a piezoelectric pump. The supply pump 134 is installed in the supply channel. The supply pump 134 is connected by wiring to the control circuit 1161 of the control unit 116 and is configured to be controllable by the control unit 116. The supply pump 134 supplies liquid to the inkjet head 1.

[0077] The transport device 115 transports the paper P along a transport path R from the media supply unit 112 through the image forming unit 113 to the media discharge unit 114. The transport device 115 comprises a plurality of guide plate pairs 121 and a plurality of transport rollers 122 arranged along the transport path R.

[0078] Each of the multiple guide plate pairs 121 comprises a pair of plate members positioned opposite each other with the paper being transported P in between, and guides the paper P along the transport path R.

[0079] The transport roller 122 is driven and rotated by the control unit 116 to feed the paper P downstream along the transport path R. Sensors for detecting the paper transport status are placed at various points along the transport path R.

[0080] The control unit 116 includes a control circuit 1161 such as a CPU (Central Processing Unit) which is a controller, a ROM (Read Only Memory) for storing various programs, a RAM (Random Access Memory) for temporarily storing various variable data and image data, and an interface unit for inputting data from the outside and outputting data to the outside.

[0081] In the inkjet recording device 100 configured as described above, when the control unit 116 detects a print command from a user operating the operation input unit in the interface, for example, it drives the transport device 115 to transport the paper P and drives the inkjet head 1 by outputting a print signal to the head unit 130 at a predetermined timing. In its ejection operation, the inkjet head 1 sends a drive signal to the drive IC 72 using an image signal corresponding to the image data, applies a drive voltage to the internal electrodes 221 and 222 to selectively drive the drive piezoelectric element 21 to be ejected, causing it to vibrate vertically, for example, in the stacking direction, thereby changing the volume of the pressure chamber 31 and ejecting ink from the nozzle 51 to form an image on the paper P held on the transport belt 118. In addition, in its liquid ejection operation, the control unit 116 drives the supply pump 134 to supply ink from the ink tank 132 to the common chamber 32 of the inkjet head 1.

[0082] Here, the driving operation for driving the inkjet head 1 will be described. The inkjet head 1 according to this embodiment is equipped with drive piezoelectric elements 21 arranged opposite to the pressure chamber 31, and these drive piezoelectric elements 21 are connected by wiring so that a voltage can be applied. The control unit 116 sends a drive signal to the drive IC 72 using an image signal corresponding to the image data, and applies a drive voltage to the internal electrodes 221 and 222 of the drive piezoelectric element 21 to be driven, thereby selectively deforming the drive piezoelectric element 21. Then, by combining the deformation of the diaphragm 30 in the tensile direction and the deformation in the compressive direction, the volume of the pressure chamber 31 is changed, and liquid is discharged.

[0083] For example, the control unit 116 alternately performs pulling and compressing operations. In the inkjet head 1, when pulling to increase the internal volume of the target pressure chamber 31, the driven piezoelectric element 21 that is being driven is contracted, while the non-driven piezoelectric elements 21 are not deformed. Also, in the inkjet head 1, when compressing to decrease the internal volume of the target pressure chamber 31, the driven piezoelectric element 21 that is being driven is extended. The non-driven piezoelectric elements 22 are not deformed.

[0084] According to the inkjet head 1 and inkjet recording device 100 of the above-described embodiment, in the stacked drive piezoelectric element 21, if the thickness of one layer is A [mm], the upper limit voltage of electronic components such as the drive IC 72 is B [V], and the polarization electric field required at the heat resistance temperature of the electronic components, which is 80°C, is C [V / mm], then the structure is such that B / A ≥ C, and the thickness of each piezoelectric layer 211 in the stacked portion is set to a thickness that allows for repolarization, thereby making it possible to apply a large electric field to the applied voltage.

[0085] In other words, as in the above embodiment, since the ink is ejected by each driving piezoelectric element 21 acting as an actuator pressurizing the pressure chamber 31, variations in the displacement between the driving piezoelectric elements 21 directly affect the print quality. Generally, before mounting control components such as circuit boards and electronic components, depolarization and repolarization can be performed by applying a reverse voltage, but after mounting control components, the direction and magnitude of the voltage that can be applied are limited. Therefore, repolarization cannot be performed with a normal electrical circuit, and a special circuit design must be prepared separately.

[0086] In contrast, the inkjet head 1 according to the above embodiment can obtain a large electric field even with a relatively small voltage that can be applied in a normal electrical circuit, by defining the thickness of the piezoelectric layer 211 based on the heat resistance temperature and upper voltage limit of the electronic components to which voltage is applied during the repolarization process. This allows the polarization process to be performed using a drive control circuit after the assembly of control components such as the substrate and electronic components. Therefore, after assembly, it is possible to apply a sufficient electric field for repolarization using the head control circuit 731 and drive IC 72 on the wiring board 73 of the inkjet head 1, and the control circuit 1161 of the control unit 116 of the inkjet recording device 100 as an external power source. For example, by controlling the repolarization process and the piezoelectric constant using the head control circuit 731, drive IC 72, and control circuit 1161, it is possible to improve yield during the manufacturing stage and improve print quality during the operation stage.

[0087] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention.

[0088] The specific materials and configurations of the piezoelectric elements 21 and 22 in the above embodiment are not limited to those described above. Furthermore, the heat resistance temperature and upper voltage limit of the electronic components may be appropriately changed depending on the materials and performance of the components.

[0089] Furthermore, in the above embodiment, multiple piezoelectric layers are stacked and the driving piezoelectric element 21 is driven using longitudinal vibration (d33) in the stacking direction, but the embodiment is not limited to this. For example, it can also be applied to a configuration in which the driving piezoelectric element 21 is composed of a single-layer piezoelectric member, and as shown in Figure 4, it can also be applied to a configuration in which it is driven by transverse vibration displaced in the d31 direction.

[0090] For example, in another embodiment, the inkjet head 1001 shown in Figure 4 has a piezoelectric member in which the stacking direction of the multiple piezoelectric layers, that is, the thickness direction of each piezoelectric layer, is aligned in a direction perpendicular to the Z direction, for example, the extension direction (Y direction). In this inkjet head 1001, each piezoelectric element 21 is displaced in the direction defined by the piezoelectric constant d31 and vibrates laterally, causing it to be displaced in the vibration direction which is the depth direction of the groove 23, and the diaphragm 30 is displaced in the vibration direction (Z direction) as in the above embodiment.

[0091] For example, in another embodiment, the inkjet head 1001 shown in Figure 4 is configured such that the stacking direction of each piezoelectric layer 211 is along a direction perpendicular to the thickness direction of the diaphragm 30, and it is driven using transverse vibration, which is a vibration perpendicular to the thickness direction of the diaphragm 30. Similar to the inkjet head 1, the inkjet head 1001 comprises a base 10, an actuator unit 20 having a plurality of piezoelectric elements 21, 22, a diaphragm 30 positioned opposite the actuator unit 20, a manifold 405 that constitutes a plurality of pressure chambers 31 and guide channels 34, a nozzle plate 50 having a plurality of nozzles 51, and a frame unit 60. In the inkjet head 1001, the piezoelectric layers 211 that constitute the plurality of piezoelectric elements 21, 22 are stacked in multiple layers in the extension direction (Y direction), which is perpendicular to the vibration direction (Z direction), which is the thickness direction of the diaphragm 30, and the arrangement direction (X direction) of the pressure chambers 31 and nozzles 51.

[0092] In the inkjet head 1001, external electrodes 223 and 224 are formed on both end faces of the actuator section 20, one on one side in the vibration direction and the other on the other side, respectively, and are connected to internal electrodes 221 and 222. The external electrodes 223 and 224 on both sides are routed along one side in the extension direction and connected to the wiring film 71. The piezoelectric layer 211 shall consist of three or more layers, and the thickness of each piezoelectric layer 211 shall be such that B / A ≥ C, where A [mm] is the thickness of the individual piezoelectric layer 211, B [V] is the upper limit voltage of the electronic component such as the drive IC 72, and C [V / mm] is the polarization electric field required at the heat resistance temperature of the electronic component, which is 80°C, and the thickness shall be 10 μm or more. For example, if the piezoelectric layer 211 is made of PZT, the upper limit voltage of the electronic component mounted on the head is 60V as defined by the drive IC 72, the heat resistance temperature is 80°C, and the electric field required when polarization processing of the piezoelectric material used under 80°C conditions is 3.5 kV / mm, then the thickness of each piezoelectric layer 211 shall be 17.1 μm or less. Even in this configuration, by specifying the thickness of the piezoelectric layer 211 to a thickness where B / A ≥ C, repolarization processing after mounting becomes possible.

[0093] The arrangement of the nozzles 51 and pressure chambers 31 is not limited to the above embodiment. For example, two or more rows of nozzles 51 may be arranged. Also, air chambers that serve as dummy chambers may be formed between multiple pressure chambers 31. The invention is not limited to circulating inkjet heads but can also be non-circulating inkjet heads, and is not limited to end-shooter type inkjet heads but can also be applied to side-shooter type inkjet heads.

[0094] Furthermore, although an example has been shown in which the piezoelectric elements 21 and 22 have dummy layers 212 at both ends in the stacking direction, the invention is not limited to this, and the piezoelectric elements 21 and 22 may have dummy layers 212 on only one side, or the piezoelectric elements 21 and 22 may be configured without dummy layers 212. In addition, the configuration and positional relationships of various components, including the flow path member 40, nozzle plate 50, and frame portion 60, are not limited to the example described above and can be changed as appropriate.

[0095] Furthermore, the liquid to be dispensed is not limited to printing ink; for example, it could be a device that dispenses a liquid containing conductive particles for forming wiring patterns on a printed circuit board.

[0096] Furthermore, although the above embodiment shows an example of the inkjet head 1 being used in a liquid ejection device such as an inkjet recording device, it is not limited to this, and can also be used in 3D printers, industrial manufacturing machinery, and medical applications, enabling miniaturization, weight reduction, and cost reduction.

[0097] According to at least one embodiment described above, the desired flow path shape can be easily set.

[0098] In addition, several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. The following is an appended description equivalent to the invention described in the claims of the original application. (1) An actuator having alternatingly stacked piezoelectric layers and electrodes, A diaphragm positioned opposite the actuator, The actuator comprises an electronic component connected to the actuator, A liquid dispensing head that satisfies B / A ≥ C, where A [mm] is the thickness of one layer of the piezoelectric material of the actuator, B [V] is the upper limit voltage of the electronic component, and C [V / mm] is the polarization electric field of the piezoelectric material constituting the piezoelectric material under the heat resistance temperature conditions of the electronic component. (2) The actuator is a liquid dispensing head according to (1), comprising three or more piezoelectric layers. (3) The liquid dispensing head according to (1), wherein the thickness of one layer of the piezoelectric material is 10 μm or more. (4) The liquid dispensing head according to (1), wherein the lamination direction of the piezoelectric layer is aligned with the vibration direction of the diaphragm. (5) A flow channel member having a pressure chamber whose volume changes due to the vibration of the actuator, A nozzle plate having a nozzle that communicates with the pressure chamber, Equipped with, The liquid dispensing head according to (1), wherein the electronic component is a drive IC used for drive control of the actuator. [Explanation of Symbols]

[0099] 1...Inkjet head, 10...Base, 20...Actuator unit, 21...Drive piezoelectric element, 22...Non-drive piezoelectric element, 23...Groove, 26...Piezoelectric structure unit, 30...Diaphragm, 31...Pressure chamber, 32...Common chamber, 33...Communication unit, 34...Guide channel, 35...Ink channel, 40...Channel member, 41...Peripheral wall unit, 42...Partition wall unit, 43...Guide wall, 50...Nozzle plate, 51...Nozzle, 60...Frame unit, 70...Drive circuit, 71...Wiring film, 72...Drive IC, 73...Printed wiring board, 731...Head control circuit, 100...Inkjet recording device, 111...Housing, 1 12...Media supply unit, 113...Image forming unit, 114...Media discharge unit, 115...Transportation device, 117...Support unit, 118...Transport belt, 119...Support plate, 120...Belt roller, 121...Guide plate pair, 122...Transport roller, 130...Head unit, 132...Ink tank, 133...Connecting channel, 134...Supply pump, 116...Control unit, 1161...Control circuit, 211...Piezoelectric layer, 212...Dummy layer, 221...Internal electrode, 222...Internal electrode, 223...External electrode, 224...External electrode, 301...Vibration region, 302...Support region, 405...Manifold.

Claims

1. An actuator having three or more piezoelectric layers and electrodes stacked alternately, A diaphragm positioned opposite the actuator, The actuator comprises a drive IC connected to the actuator, With the aforementioned drive IC mounted, the system is configured to enable repolarization by applying a voltage to the piezoelectric layer via the drive IC. A liquid dispensing head that satisfies B / A ≥ C, where A [mm] is the thickness of one layer of the piezoelectric material of the actuator, B [V] is the upper limit voltage of the drive IC, and C [V / mm] is the polarization electric field required to polarize the piezoelectric material constituting the piezoelectric material under the condition of 80°C, which is the heat resistance temperature of the drive IC.

2. The liquid dispensing head according to claim 1, wherein the thickness of one layer of the piezoelectric material is 10 μm or more.

3. The liquid dispensing head according to claim 1, wherein the lamination direction of the piezoelectric layer is aligned with the vibration direction of the diaphragm.

4. A flow channel member having a pressure chamber whose volume changes due to the vibration of the actuator, A nozzle plate having a nozzle that communicates with the pressure chamber, A liquid dispensing head according to claim 1, comprising:

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