Drive unit, liquid discharge unit, and drive method

Abstract

To provide a highly reliable drive unit, liquid dispensing unit, and drive method. [Solution] The drive device has a selection unit that selects one or more pulse voltages from a pulse waveform including multiple pulse voltages for at least one of the first electrode and second electrode of a piezoelectric element. A drive waveform representing the time change of the voltage of the second electrode with respect to the voltage of the first electrode is applied to each of the piezoelectric elements. The drive waveform has one or more pulse voltages selected by the selection unit, including positive and negative voltages. If the maximum voltage of the drive waveform is V1 and the minimum voltage is V2, then during the discharge period in which the liquid is discharged from the liquid discharge head, the absolute value of the first slope of the drive waveform in the first period when the voltage is 0.1 × V2 or more and 0.1 × V1 or less is smaller than at least one of the absolute value of the second slope of the drive waveform in the second period when the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the drive waveform in the third period when the voltage is 0.6 × V2 or more and 0.4 × V2 or less.

Description

Technical Field

[0001] The present invention relates to a driving device, a liquid ejection device, and a driving method.

Background Art

[0002] Conventionally, a technique for driving a liquid ejection head including a piezoelectric element has been known.

[0003] For example, Patent Document 1 discloses a technique having a selection unit such as a voltage switching unit that switches a pulse voltage applied to each of a plurality of actuators such as piezoelectric elements included in a liquid ejection head.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique of Patent Document 1, when a pulse voltage is applied to the first electrode and the second electrode provided in each of the plurality of piezoelectric elements, the application timing deviates from the desired one, so that the reliability of the driving device, the liquid ejection device, and the driving method may decrease.

[0005] An object of the present invention is to provide a highly reliable driving device, a liquid ejection device, and a driving method.

Means for Solving the Problems

[0006] A drive device according to one aspect of the present invention is a drive device for driving a liquid discharge head including a plurality of piezoelectric elements, each having a first electrode and a second electrode, and having a selection unit that selects one or more pulse voltages to be applied to at least one of the first electrode and the second electrode of each of the plurality of piezoelectric elements from a pulse waveform including a plurality of input pulse voltages, the drive device applies a drive waveform representing the time change of the voltage applied to the second electrode with reference to the voltage applied to the first electrode to each of the plurality of piezoelectric elements, the drive waveform includes positive and negative voltages, Having one or more pulse voltages selected by the selection unit, with the maximum voltage of the drive waveform being V1 and the minimum voltage of the drive waveform being V2, in the discharge period corresponding to the period during which the liquid is discharged from the liquid discharge head, the absolute value of the first slope of the drive waveform in the first period when the voltage is 0.1 × V2 or more and 0.1 × V1 or less is smaller than at least one of the absolute value of the second slope of the drive waveform in the second period when the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the drive waveform in the third period when the voltage is 0.6 × V2 or more and 0.4 × V2 or less.

[0007] A driving method according to one aspect of the present invention is a driving method by a driving device for driving a liquid discharge head including a plurality of piezoelectric elements, each having a first electrode and a second electrode, wherein the driving device, by a selection unit, selects one or more pulse voltages to be applied to at least one of the first electrode and the second electrode of each of the plurality of piezoelectric elements from a pulse waveform including a plurality of input pulse voltages, and applies a driving waveform to each of the plurality of piezoelectric elements that represents the time change of the voltage applied to the second electrode with reference to the voltage applied to the first electrode, wherein the driving waveform includes positive and negative voltages Furthermore, having one or more pulse voltages selected by the selection unit, with the maximum voltage of the drive waveform being V1 and the minimum voltage of the drive waveform being V2, in the discharge period corresponding to the period during which the liquid is discharged from the liquid discharge head, the absolute value of the first slope of the drive waveform during the period when the voltage is 0.1 × V2 or more and 0.1 × V1 or less is smaller than at least one of the absolute value of the second slope of the drive waveform during the period when the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the drive waveform during the period when the voltage is 0.6 × V2 or more and 0.4 × V2 or less. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a highly reliable drive device, liquid dispensing device, and drive method. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the configuration of a liquid dispensing device having a drive device according to the first embodiment. [Figure 2] This is a schematic top view of a liquid discharge head driven by a drive device according to the first embodiment. [Figure 3] This is a schematic cross-sectional view of the line III-III in Figure 2. [Figure 4] This is an enlarged view showing an example of area IV in Figure 3. [Figure 5] Figure 3 is a magnified view showing another example of area IV. [Figure 6]This is a schematic diagram showing the configuration of the drive unit according to the first embodiment. [Figure 7] This figure shows the relationship between the applied voltage and displacement in the piezoelectric element of the liquid discharge head driven by the drive device according to the first embodiment. [Figure 8] This figure shows an example of a drive waveform applied to the liquid discharge head from the drive device according to the first embodiment. [Figure 9] This timing chart shows a first example of how a drive waveform is applied to a piezoelectric element from a drive device according to the first embodiment. [Figure 10] This timing chart shows a second example of how a drive waveform is applied to a piezoelectric element from the drive device according to the first embodiment. [Figure 11] This timing chart shows the first example of how a drive waveform is applied to a piezoelectric element from a drive device relating to a comparative example. [Figure 12] This timing chart shows a second example of how a drive waveform is applied to a piezoelectric element from a drive device relating to a comparative example. [Figure 13] This timing chart shows a first example of how a drive waveform is applied to a piezoelectric element from the drive device according to the second embodiment. [Figure 14] This timing chart shows a second example of how a drive waveform is applied to a piezoelectric element from the drive device according to the second embodiment. [Figure 15] This is a timing chart showing how a drive waveform is applied to a piezoelectric element from the drive device according to the third embodiment. [Modes for carrying out the invention]

[0010] A driving device, a liquid ejection device, and a driving method according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the following embodiments are merely examples of the driving device, the liquid ejection device, and the driving method according to the embodiment of the present invention, and are not limited thereto. The sizes, positional relationships, etc. of the members shown in each drawing may be exaggerated for clarity of explanation. In the following description, the same names and reference numerals denote the same or similar members, and detailed descriptions thereof will be omitted as appropriate.

[0011] In the following description, for the sake of easy understanding, the arrangement and configuration of each part may be described using the XYZ orthogonal coordinate system. The three axes in the XYZ orthogonal coordinate system are perpendicular to each other. In the XYZ orthogonal coordinate system, the direction in which the X-axis extends is defined as the "X direction", the direction in which the Y-axis extends is defined as the "Y direction", and the direction in which the Z-axis extends is defined as the "Z direction". The direction in which the arrow of the X-axis points is denoted as the +X side, and the opposite side of the +X side is denoted as the -X side. The direction in which the arrow of the Y-axis points is denoted as the +Y side, and the opposite side of the +Y side is denoted as the -Y side. The direction in which the arrow of the Z-axis points is denoted as the +Z side, and the opposite side of the +Z side is denoted as the -Z side.

[0012] In this specification, as an example, the liquid ejection head driven by the driving device according to the embodiment of the present invention ejects liquid in the +Z direction. However, the above direction expressions merely describe the relationships of relative positions, orientations, directions, etc., and do not have to match the relationships during use. Also, these directions are independent of the gravitational direction.

[0013] In the terms of this specification, parallel may include an inclination of ±10 degrees or less with respect to parallel. Also, orthogonal may include an inclination of ±10 degrees or less with respect to orthogonal.

[0014] [First Embodiment] <Configuration of a Liquid Ejection Device Having a Driving Device According to the First Embodiment>[[ID=第十九]] Referring to FIGS. 1 to 5, a liquid ejection device having a driving device according to the first embodiment will be described.

[0015] (Overall Configuration) FIG. 1 is a block diagram showing the configuration of a liquid ejection device 100 having a drive device 20 according to the first embodiment. The liquid ejection device 100 includes a liquid ejection head 10 and a drive device 20 that drives the liquid ejection head 10. The liquid ejection device 100 is, for example, an inkjet printer that ejects liquid onto a recording medium such as paper to form an image on the recording medium. However, the liquid ejection device 100 is not limited to an inkjet printer. For example, the liquid ejection device 100 may be a modeling device that ejects liquid onto a modeling table or a modeled object to model a three-dimensional object, or a manufacturing device that ejects liquid to manufacture a manufacturing target object, etc.

[0016] (Configuration of the liquid ejection head 10) Referring to FIGS. 2 to 4, the configuration of the liquid ejection head 10 will be described. FIG. 2 is a schematic top view of the liquid ejection head 10 driven by the drive device 20. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is an enlarged view showing an example of the IV region in FIG. 3.

[0017] The liquid ejection head 10 driven by the drive device 20 according to the first embodiment includes a plurality of piezoelectric elements 17 each having an upper electrode 171 and a lower electrode 173. Note that the upper electrode 171 corresponds to an example of the second electrode, and the lower electrode 173 corresponds to an example of the first electrode.

[0018] In the example shown in FIGS. 2 to 4, the liquid ejection head 10 has a plurality of nozzles 11 that eject liquid, a plurality of pressure chambers 12 that communicate corresponding to the plurality of nozzles 11, and a nozzle plate 13 on which the plurality of nozzles 11 are formed. Further, the liquid ejection head 10 has a fluid resistance 14 provided on the side opposite to the side where the nozzles 11 are located in the pressure chamber 12 and that confines the pressure generated in the pressure chamber 12, and a common liquid chamber 15 that communicates with the plurality of pressure chambers 12. Furthermore, the liquid ejection head 10 has a first flow path 16-1 and a second flow path 16-2 through which liquid supplied from a liquid storage portion disposed outside the liquid ejection head 10 to the pressure chamber 12 via the common liquid chamber 15 passes.

[0019] In the examples shown in Figures 3 and 4, the pressure chamber 12 is composed of a pressure chamber substrate 120 and a fluid resistance substrate 140. The pressure chamber 12 is a space defined by at least a pressure chamber partition wall 121, a nozzle plate 13, and a fluid resistance 14. The common liquid chamber 15, the first flow path 16-1, and the second flow path 16-2 are formed in the common liquid chamber substrate 150.

[0020] The liquid discharge head 10 includes a piezoelectric element 17 composed of an upper electrode 171, a piezoelectric film 172, and a lower electrode 173, wiring 181, a protective film 182 that protects the piezoelectric element 17 and wiring 181 for electrical insulation or to reduce moisture permeability, and an interlayer insulating film 183 that covers the piezoelectric element 17.

[0021] The piezoelectric element 17, wiring 181, protective film 182, and interlayer insulating film 183 are located on the nozzle plate 13 and are arranged inside the protective film 182. The protective film 182 protects the wiring 181, interlayer insulating film 183, and piezoelectric element 17 by covering them. The lower electrode 173 is located on the nozzle plate 13. The piezoelectric film 172 is located on the lower electrode 173. The upper electrode 171 is located on the piezoelectric film 172.

[0022] The piezoelectric film 172 may contain at least one of aluminum nitride (AlN) and aluminum scandium nitride (ScAlN). However, the piezoelectric film 172 is not limited to AlN or ScAlN. The piezoelectric film 172 can be made of inter-IIb-IVb group compounds such as CdS, CdSe, ZnO, ZnTe, CdTe, or inter-IIIb-Vb group compounds such as GaAs, GaSb, InS, InSb, etc.

[0023] Many compounds of the IIb-VIb and IIIb-Vb groups have a zincblende or wurtzite crystal structure. In this embodiment, for example, a piezoelectric film 172 having a wurtzite crystal structure can be suitably used. The wurtzite crystal belongs to the hexagonal crystal system. The crystal has polarity with the c axis as the polar axis. Due to the symmetry of the wurtzite crystal, the piezoelectric constants of the wurtzite crystal are only d31, d33, and d15. By applying an electric field in the direction of the c axis of the crystal, a displacement in the direction of the c axis can be generated. At this time, strain is also generated in the direction perpendicular to the c axis. By utilizing this strain and creating a unimorph structure in which the piezoelectric film 172 and the nozzle plate 13 are stacked, deformation can be induced in the nozzle plate 13.

[0024] The nozzle plate 13, pressure chamber substrate 120, fluid resistance substrate 140, common liquid chamber substrate 150, upper electrode 171, lower electrode 173, and wiring 181 are made of metal material or the like. The protective film 182 and interlayer insulating film 183 are made of inorganic material or resin material or the like.

[0025] The upper electrode 171 and the lower electrode 173 are electrically connected to the drive unit 20 by wiring 181. When a voltage is applied from the drive unit 20 to the upper electrode 171 and the lower electrode 173 through the wiring 181, the piezoelectric element 17 performs a desired operation such as vibration. As the piezoelectric element 17 operates, the nozzle plate 13 deforms. The deformation of the nozzle plate 13 changes the pressure inside the pressure chamber 12. Due to the pressure change inside the pressure chamber 12, liquid is discharged from the nozzle 11.

[0026] Wiring 181 is independently connected to each piezoelectric element 17 located in each of the multiple pressure chambers 12. The liquid discharge head 10 can individually drive the multiple piezoelectric elements 17 by applying a drive voltage to each of the multiple piezoelectric elements 17 to which the wiring 181 is connected, and discharge liquid individually from the multiple nozzles 11.

[0027] The pressure chamber substrate 120 can be fabricated by applying a MEMS (Micro Electro Mechanical Systems) process to an SOI (Silicon on Insulator) substrate. Si can be used for the pressure chamber partition wall 121, SiO2 for the nozzle plate 13, ScAlN for the piezoelectric element, and BCB (benzocyclobutene) for the protective film.

[0028] If the area around the nozzle 11 on the nozzle plate 13 is wet with liquid, the liquid discharge from the nozzle 11 becomes unstable. Therefore, a water-repellent film may be formed on the outermost surface of the nozzle plate 13. The fluid resistance substrate 140 can be manufactured by applying a MEMS process to a silicon substrate.

[0029] Figure 5 is an enlarged view showing another example of region IV in Figure 3. In the example shown in Figure 5, the liquid discharge head 10 has a pressure chamber substrate 120 and does not have the fluid resistance substrate 140 shown in Figure 4. By not having a fluid resistance substrate, the liquid discharge head 10 can, for example, improve the ability to fill the pressure chamber 12 with liquid.

[0030] (Drive unit 20) Figure 6 is a schematic diagram showing the configuration of the drive unit 20.

[0031] The drive unit 20 has a selection unit 21 that selects one or more pulse voltages to be applied to at least one of the upper electrode 171 and lower electrode 173 of each of the multiple piezoelectric elements 17 from a pulse waveform PW that includes multiple input pulse voltages. In the example shown in Figure 6, the drive unit 20 also includes a generation unit 22 and a selection control unit 23. The generation unit 22 generates a pulse waveform PW that includes multiple pulse voltages within a predetermined period. The selection control unit 23 supplies selection information Se to the selection unit 21, which causes the selection unit 21 to select one or more pulse voltages from the multiple pulse voltages included in the pulse waveform PW generated by the generation unit 22 to be applied to at least one of the upper electrode 171 and lower electrode 173.

[0032] Based on the selection information Se supplied from the selection control unit 23, the selection unit 21 selects either a pulse voltage or 0V as the voltage to be applied to the upper electrode 171 and lower electrode 173 of the piezoelectric element 17. In this embodiment, the drive device 20 applies a drive waveform DW, which represents the time change of the voltage applied to the upper electrode 171 with the voltage applied to the lower electrode 173 as a reference, to each of the plurality of piezoelectric elements 17. The drive waveform DW includes positive and negative voltages and has one or more pulse voltages selected by the selection unit 21.

[0033] In the example shown in Figure 6, the selection unit 21 is configured to include multiple electrical circuits corresponding to multiple piezoelectric elements 17. The multiple electrical circuits are formed on the same substrate as the multiple piezoelectric elements 17. The selection unit 21 is, for example, an electrical circuit including a transistor. The selection unit 21 can switch the voltage applied to the upper electrode 171 and lower electrode 173 of the piezoelectric element 17 between a pulse voltage and 0V using the transistor.

[0034] In the example shown in Figure 6, the selection unit 21B-1 switches the voltage applied to the lower electrode 173-1 to either a pulsed voltage or 0V. The selection unit 21A-1 switches the voltage applied to the upper electrode 171-1 to either a pulsed voltage or 0V. The selection unit 21B-2 switches the voltage applied to the lower electrode 173-2 to either a pulsed voltage or 0V. The selection unit 21A-2 switches the voltage applied to the upper electrode 171-2 to either a pulsed voltage or 0V. The selection unit 21B-3 switches the voltage applied to the lower electrode 173-3 to either a pulsed voltage or 0V. The selection unit 21A-3 switches the voltage applied to the upper electrode 171-3 to either a pulsed voltage or 0V.

[0035] The selection information Se includes a pulse selection signal that selects a pulse voltage to be applied to the piezoelectric element 17 from among multiple pulse voltages included in the pulse waveform. The selection information Se also includes a polarity selection signal that selects whether to apply the pulse voltage selected by the pulse selection signal to the upper electrode 171 or to the lower electrode 173. The pulse selection signal and polarity selection signal will be described in detail with reference to Figure 9.

[0036] <Operation of the drive unit 20> Figure 7 shows an example of the relationship between the applied voltage and displacement of the piezoelectric element 17 of the liquid discharge head 10 driven by the drive unit 20. The drive unit 20 applies a potential to the upper electrode 171, with the potential of the lower electrode 173 as the reference, as the applied voltage. Regarding the displacement of the piezoelectric element 17, a displacement that causes the pressure chamber 12 to contract is defined as a positive displacement. As shown in Figure 7, the piezoelectric element 17 displaces in proportion to the applied voltage. The piezoelectric element 17 undergoes a positive displacement when a positive voltage is applied, and a negative displacement when a negative voltage is applied.

[0037] Figure 8 shows an example of the drive waveform DW applied from the drive unit 20 to the liquid discharge head 10.

[0038] In Figure 8, the discharge period P is the period during which the drive unit 20 discharges liquid from the nozzle 11 to the liquid discharge head 10. During the discharge period P, the liquid discharge head 10 discharges liquid from the nozzle 11 by changing the pressure chamber 12 from an expanded state to a contracted state.

[0039] Let V1 be the maximum voltage of the drive waveform DW, and V2 be the minimum voltage of the drive waveform DW. In this embodiment, during the discharge period P, the absolute value of the first slope a1 of the drive waveform DW in the first period T1 is smaller than at least one of the absolute value of the second slope a2 of the drive waveform DW in the second period T2, and the absolute value of the third slope a3 of the drive waveform DW in the third period T3. The first period T1 is the period during which the voltage is between 0.1 × V2 and 0.1 × V1. The second period T2 is the period during which the voltage is between 0.4 × V1 and 0.6 × V1. The third period T3 is the period during which the voltage is between 0.6 × V2 and 0.4 × V2.

[0040] In this embodiment, the absolute value of the first slope a1 may be the average, maximum, or minimum value of the absolute values ​​of the slope of the drive waveform DW during the first period T1. The absolute value of the second slope a2 may be the average, maximum, or minimum value of the absolute values ​​of the slope of the drive waveform DW during the second period T2. The absolute value of the third slope a3 may be the average, maximum, or minimum value of the absolute values ​​of the slope of the drive waveform DW during the third period T3. When the absolute value of the first slope a1 is the average value of the absolute values ​​of the slope of the drive waveform DW during the first period T1, it is preferable that the absolute value of the second slope a2 is the average value of the absolute values ​​of the slope of the drive waveform DW during the second period T2, and the absolute value of the third slope a3 is the average value of the slope of the drive waveform DW during the third period T3. In other words, it is preferable that the mean, maximum, or minimum value be consistent within the absolute values ​​of the first slope a1, the second slope a2, and the third slope a3.

[0041] The absolute value of the first slope a1 may be the slope when the voltage is 0V. The absolute value of the second slope a2 may be the absolute value of the slope when the voltage is 0.5 × V1. The absolute value of the absolute value of may be the absolute value of the slope when the voltage is 0.5 × V2. The absolute value of the first slope a1 may be less than either the absolute value of the second slope a2 or the absolute value of the third slope a3.

[0042] Figure 9 is a timing chart showing a first example of how the drive waveform DW is applied from the drive unit 20 to the piezoelectric element 17 of the liquid discharge head 10. Figure 10 is a timing chart showing a second example of how the drive waveform DW is applied from the drive unit 20 to the piezoelectric element 17 of the liquid discharge head 10.

[0043] The following describes the waveforms, signals, or applied voltages in Figure 9. The same descriptions apply to the waveforms, signals, or applied voltages in Figures 10 through 15, which are shown below.

[0044] The "pulse waveform" is the pulse waveform PW generated by the generation unit 22. In the example shown in Figure 9, the pulse waveform PW includes a pulse voltage P1 and a pulse voltage P2 that follows the pulse voltage P1.

[0045] The "pulse selection signal" is a signal that selects the pulse voltage to be applied to the piezoelectric element 17 from among multiple pulse voltages contained in the pulse waveform PW. The time domain in which the "pulse selection signal" is High is selected as the pulse voltage to be applied to the piezoelectric element 17.

[0046] The "polarity selection signal" is a signal that selects whether to apply the pulse voltage selected by the pulse selection signal to the upper electrode 171 or to the lower electrode 173. When the "polarity selection signal" is Low, the lower electrode is selected, and when the "polarity selection signal" is High, the upper electrode is selected. The "pulse selection signal" and the "polarity selection signal" are signals included in the selection information Se input from the selection control unit 23 to the selection unit 21.

[0047] "Voltage applied to the upper electrode" represents the voltage applied to the upper electrode 171 as a result of the selection made by the selection unit 21 based on the selection information Se. "Voltage applied to the upper electrode" is the voltage extracted from the pulse waveform PW only in the time domain where the "pulse selection signal" is High and the "polarity selection signal" is High.

[0048] "Voltage applied to the lower electrode" represents the voltage applied to the lower electrode 173 as a result of the selection made by the selection unit 21 based on the selection information Se. "Voltage applied to the lower electrode" is the voltage extracted from the pulse waveform PW only in the time domain when the "pulse selection signal" is High and the "polarity selection signal" is Low. "Drive waveform" is the drive waveform DW applied to the piezoelectric element 17, corresponding to the difference between "Voltage applied to the upper electrode" and "Voltage applied to the lower electrode".

[0049] In the examples shown in Figures 9 and 10, a time interval ΔT occurs between pulse voltages P1 and P2 in the pulse waveform PW. As a result, in the drive waveform DW shown in Figures 9 and 10, a time interval ΔT occurs between the voltage applied to the upper electrode 171 and the voltage applied to the lower electrode 173. From another perspective, during the discharge period P, the absolute value of the first slope a1 is smaller than the absolute value of both the second slope a2 and the third slope a3. Because of the existence of this time interval ΔT, and because the absolute value of the first slope a1 is smaller than the absolute value of both the second slope a2 and the third slope a3, even if a delay occurs in the polarity selection signal, as shown in Figure 10, the voltage applied to the piezoelectric element 17 remains the same as if there were no delay in the polarity selection signal. As a result, the voltage change in the voltage applied to the upper electrode 171 and the lower electrode 173 in the comparative example described below can be reduced, and the load on the wiring 181 or the electrical circuit such as the transistor included in the selection unit 21 can be reduced.

[0050] <Comparative Example> Figure 11 is a timing chart showing a first example of how a drive waveform is applied to a piezoelectric element from a drive device according to a comparative example. Figure 12 is a timing chart showing a second example of how a drive waveform is applied to a piezoelectric element from a drive device according to a comparative example.

[0051] In the first comparative example shown in Figure 11, and the second comparative example shown in Figure 12, the absolute values ​​of the first slope a1, the second slope a2, and the third slope a3 are all equal during the discharge period P. Furthermore, in the first comparative example shown in Figure 11, there is no delay in the "polarity selection signal," while in the second comparative example shown in Figure 12, there is a delay in the "polarity selection signal."

[0052] As in the first example of comparative examples, no particular problems arise when there is no delay in the polarity selection signal. On the other hand, as in the second example of comparative examples, when there is a delay in the polarity selection signal, the voltage value applied to the piezoelectric element 17 in the drive waveform DW deviates significantly from the target voltage value, as shown in Figure 12. In particular, at time Q in Figure 12, both the upper electrode 171 and the lower electrode 173 show large voltage changes. The current increases in proportion to the magnitude of the voltage change, and the load on the wiring 181 increases. Repeated periods of high load on the wiring 181 may affect the reliability of the wiring 181. The impact on the reliability of the wiring 181 includes a shortened lifespan of the wiring 181, damage to the wiring 181, and malfunctions of the liquid discharge head 10 due to damage to the wiring 181. The impact on the reliability of the wiring 181 is particularly pronounced when the drive device 20 drives the piezoelectric element 17 at a high voltage.

[0053] In addition to the impact on the reliability of the wiring 181, at this time Q, the transistors included in the selection unit 21 undergo high-voltage switching, which may also affect the reliability of the transistors and other electrical circuits. This is because, in order to miniaturize the liquid discharge head 10, when electrical circuits including transistors are formed on the same substrate as the nozzle plate 13 on which the piezoelectric element 17 is formed, the degree of freedom in transistor selection and the degree of freedom in electrical circuit design are reduced due to layout constraints within the substrate.

[0054] <Effects of the drive unit 20 and the liquid discharge unit 100> In this embodiment, the drive unit 20 is a drive unit that drives a liquid discharge head 10 which includes a plurality of piezoelectric elements 17, each having an upper electrode 171 (first electrode) and a lower electrode 173 (second electrode). The drive unit 20 has a selection unit 21 that selects one or more pulse voltages to be applied to at least one of the upper electrode 171 and lower electrode 173 of each of the plurality of piezoelectric elements 17 from a pulse waveform PW which includes a plurality of input pulse voltages.

[0055] The drive device 20 applies a drive waveform DW to each of the plurality of piezoelectric elements 17, which represents the time change of the voltage applied to the upper electrode 171 with reference to the voltage applied to the lower electrode 173. The drive waveform DW includes positive and negative voltages and has one or more pulse voltages selected by the selection unit 21. During the discharge period P, the absolute value of the first slope a1 of the drive waveform DW is smaller than at least one of the absolute values ​​of the second slope a2 and the third slope a3.

[0056] In the liquid discharge head 10, the drive unit 20 applies one pulse voltage in the pulse waveform PW to the upper electrode 171, and the next pulse voltage input to the lower electrode 173, causing a large voltage fluctuation across 0V in the piezoelectric element 17. This causes a large displacement of the nozzle plate 13, enabling liquid to be discharged from the nozzle 11.

[0057] Here, for example, during the discharge period P, if the absolute value of the first slope a1 of the drive waveform DW is equal to at least one of the absolute values ​​of the second slope a2 and the third slope a3, or greater than at least one of the absolute values ​​of the second slope a2 and the third slope a3, then when the timing of the pulse selection signal or polarity selection signal is deviated from the desired timing, a voltage that is significantly different from the target voltage will be applied to the piezoelectric element 17. This may affect the reliability of electrical circuits such as transistors included in the wiring 181 or selection unit 21.

[0058] In this embodiment, the absolute value of the first slope a1 of the drive waveform DW is smaller than at least one of the absolute values ​​of the second slope a2 and the third slope a3. As a result, even if a delay occurs in the pulse selection signal or polarity selection signal, the voltage applied to the piezoelectric element 17 remains the same as if there were no delay in the pulse selection signal or polarity selection signal. This reduces the voltage change in the voltage applied to the upper electrode 171 and the lower electrode 173, thereby reducing the load on the wiring 181 or electrical circuits such as transistors included in the selection unit 21. By reducing the load on the wiring 181 or electrical circuits, a highly reliable drive device 20 and liquid discharge device 100 can be provided. Furthermore, in this embodiment, the above effect is particularly pronounced when multiple electrical circuits included in the selection unit 21 are formed on the same substrate as multiple piezoelectric elements 17.

[0059] From the viewpoint of reducing the load on the electrical circuit included in the wiring 181 or the selected section 21, it is preferable that the absolute value of the first slope a1 is smaller than either the absolute value of the second slope a2 or the absolute value of the third slope a3.

[0060] In this embodiment, the selection unit 21 selects one or more pulse voltages from among the multiple pulse voltages included in the pulse waveform PW generated by the generation unit 22, according to the input selection information Se, to be applied to at least one of the upper electrode 171 and the lower electrode 173. As a result, the drive device 20 can apply the drive waveform DW obtained based on the pulse waveform PW to the liquid discharge head 10.

[0061] The piezoelectric element 17 in the liquid discharge head 10 preferably contains at least one of aluminum nitride and scandium aluminum nitride. Unlike piezoelectric materials such as lead zirconate titanate, aluminum nitride and scandium aluminum nitride have low film deposition temperatures, making it possible to deposit them on a substrate on which an electrical circuit has already been formed. Miniaturization is possible by forming the piezoelectric element and electrical circuit on the same substrate.

[0062] [Second Embodiment] Next, the drive device according to the second embodiment will be described. Note that names and reference numerals identical to those used in the previously described embodiments indicate the same or identical components or configurations, and detailed explanations will be omitted as appropriate. This also applies to the embodiments described later.

[0063] Figure 13 is a timing chart showing a first example of how the drive waveform DW is applied to the piezoelectric element 17 from the drive device according to the second embodiment. Figure 14 is a timing chart showing a second example of how the drive waveform DW is applied to the piezoelectric element 17 from the drive device according to the second embodiment.

[0064] The drive device according to this embodiment differs from the drive device 20 according to the first embodiment in that, in the drive waveform DW, a pulse waveform PW is used in which the absolute value of the slope near 0V is reduced instead of increasing the time interval between the voltage applied to the upper electrode 171 and the voltage applied to the lower electrode 173.

[0065] In this embodiment, for example, as shown in Figure 14, the voltage change applied to the piezoelectric element 17 can be reduced even if there is a delay in the polarity selection signal. In this embodiment, compared to the second example of comparative examples shown in Figure 12, the rapid voltage change at the upper electrode 171 or the lower electrode 173 at time Q can be suppressed. In this embodiment as well, the same effect as the drive device 20 according to the first embodiment can be obtained by making the absolute value of the first slope a1 smaller than at least one of the absolute values ​​of the second slope a2 and the third slope a3 during the discharge period P.

[0066] [Third Embodiment] Next, a drive device according to the third embodiment will be described.

[0067] The drive device according to this embodiment differs from the drive device 20 according to the first embodiment in that the pulse waveform PW includes three pulse voltages: pulse voltage P1, pulse voltage P2, and pulse voltage P3.

[0068] A larger number of pulse voltages in the pulse waveform PW allows for more favorable utilization of the resonance phenomenon within the pressure chamber 12, enabling discharge at lower voltages. In this embodiment as well, the absolute value of the first slope a1 during the discharge period P is smaller than at least one of the absolute values ​​of the second slope a2 and the third slope a3, thereby achieving the same effect as the drive device 20 according to the first embodiment.

[0069] Although preferred embodiments have been described in detail above, the present invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0070] The ordinal numbers, quantities, and other figures used in the description of the embodiments of the present invention are all illustrative to specifically illustrate the technology of the present invention, and the present invention is not limited to these illustrative figures. Furthermore, the connection relationships between the components are illustrative to specifically illustrate the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0071] Examples of the present invention are as follows: <1> A drive device for driving a liquid discharge head including a plurality of piezoelectric elements, each having a first electrode and a second electrode, comprising a selection unit that selects one or more pulse voltages to be applied to at least one of the first electrode and the second electrode of each of the plurality of piezoelectric elements from a pulse waveform including a plurality of input pulse voltages, wherein the drive device applies a drive waveform to each of the plurality of piezoelectric elements that represents the time change of the voltage applied to the second electrode with reference to the voltage applied to the first electrode, and the drive waveform includes positive and negative voltages and is selected by the selection unit. The drive device has one or more pulse voltages, and when the maximum voltage of the drive waveform is V1 and the minimum voltage of the drive waveform is V2, the absolute value of the first slope of the drive waveform in the first period when the voltage is 0.1 × V2 or more and 0.1 × V1 or less in the discharge period corresponding to the period during which the liquid is discharged to the liquid discharge head is smaller than at least one of the absolute value of the second slope of the drive waveform in the second period when the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the drive waveform in the third period when the voltage is 0.6 × V2 or more and 0.4 × V2 or less. <2> The absolute value of the first slope is one of the average, maximum, or minimum values ​​of the absolute value of the slope of the drive waveform during the first period; the absolute value of the second slope is one of the average, maximum, or minimum values ​​of the absolute value of the slope of the drive waveform during the second period; and the absolute value of the third slope is one of the average, maximum, or minimum values ​​of the absolute value of the slope of the drive waveform during the third period. <1> This is the drive device described in [reference]. <3> The absolute value of the first slope is the absolute value of the slope when the voltage is 0V, the absolute value of the second slope is the absolute value of the slope when the voltage is 0.5 × V1, and the absolute value of the third slope is the absolute value of the slope when the voltage is 0.5 × V2. <1> or the above <2> This is the drive device described in [reference]. <4> The device has a generation unit that generates a pulse waveform containing a plurality of pulse voltages within a predetermined period, and the selection unit selects one or more pulse voltages from the plurality of pulse voltages included in the pulse waveform generated by the generation unit to be applied to at least one of the first electrode and the second electrode, according to input selection information. <1> From the above <3> It is a drive device described in any one of the following. <5> The absolute value of the first slope is smaller than either the absolute value of the second slope or the absolute value of the third slope. <1> From the above <4> It is a drive device described in any one of the following. <6> The selection unit is configured to include a plurality of electrical circuits corresponding to a plurality of piezoelectric elements, and the plurality of electrical circuits are formed on the same substrate as the plurality of piezoelectric elements. <1> From the above <5> It is a drive device described in any one of the following. <7> The liquid discharge head includes a plurality of piezoelectric elements, each having a first electrode and a second electrode, and <1> From the above <5> A liquid dispensing device having a drive device as described in any one of the above. <8> The liquid discharge head comprises a plurality of nozzles, each discharging liquid individually, and a plurality of individual liquid chambers communicating with the plurality of nozzles, and the plurality of piezoelectric elements generate pressure to be applied to the liquid in the individual liquid chambers, corresponding to the plurality of individual liquid chambers. <7> This is the liquid dispensing device described in [reference]. <9> The piezoelectric element includes at least one of aluminum nitride and aluminum scandium nitride. <8> This is the liquid dispensing device described in [reference]. <10> A driving method by a driving device for driving a liquid discharge head including a plurality of piezoelectric elements, each having a first electrode and a second electrode, wherein the driving device, by a selection unit, selects one or more pulse voltages to be applied to at least one of the first electrode and the second electrode of each of the plurality of piezoelectric elements from a pulse waveform including a plurality of input pulse voltages, and applies a driving waveform to each of the plurality of piezoelectric elements that represents the time change of the voltage applied to the second electrode with reference to the voltage applied to the first electrode, wherein the driving waveform includes positive and negative voltages, and the selection unit A driving method having one or more selected pulse voltages, where V1 is the maximum voltage of the driving waveform and V2 is the minimum voltage of the driving waveform, wherein, during the discharge period corresponding to the period for which the liquid is discharged from the liquid discharge head, the absolute value of the first slope of the driving waveform during the period when the voltage is 0.1 × V2 or more and 0.1 × V1 or less is smaller than at least one of the absolute value of the second slope of the driving waveform during the period when the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the driving waveform during the period when the voltage is 0.6 × V2 or more and 0.4 × V2 or less. [Explanation of Symbols]

[0072] 10 Liquid dispensing heads 11 nozzles 12 Pressure Chamber 13 Nozzle Plate 14 Fluid resistance 15 Common liquid chamber 16-1 First channel 16-2 Second channel 17 Piezoelectric element 20 Drive unit 21, 21A-1, 21A-2, 21A-3, 21B-1, 21B-2, 21B-3 Selection section 22 Generation part 23 Selection Control Unit 100 Liquid dispensing device 120 Pressure chamber substrate 140 Fluid resistance substrate 171, 171-1, 171-2, 171-3 Upper electrode 172 Piezoelectric film 173, 173-1, 173-2 Lower electrode 181 Wiring 182 Protective film 183 Interlayer insulating film a1 First slope a2 Second slope a3 Third slope DW drive waveform P discharge period P1, P2, P3 pulse voltages PW pulse waveform Q time Se Selection Information T1 Period 1 T2 Second Period T3 Third Period V1 Maximum Voltage V2 Minimum Voltage ΔT time [Prior art documents] [Patent Documents]

[0073] [Patent Document 1] Patent No. 7242936

Claims

1. A drive device for driving a liquid discharge head, which includes a plurality of piezoelectric elements, each having a first electrode and a second electrode, The system includes a selection unit that selects one or more pulse voltages to be applied to at least one of the first electrode and the second electrode of each of the plurality of piezoelectric elements from a pulse waveform that includes a plurality of input pulse voltages. The drive device applies a drive waveform to each of the plurality of piezoelectric elements, which represents the time change of the voltage applied to the second electrode with respect to the voltage applied to the first electrode. The drive waveform includes positive and negative voltages and has one or more pulse voltages selected by the selection unit. Let V1 be the maximum voltage of the aforementioned drive waveform. If the minimum voltage of the aforementioned drive waveform is V2, A drive device in which, during a discharge period corresponding to the period for which liquid is discharged from the liquid discharge head, the absolute value of the first slope of the drive waveform in a first period where the voltage is 0.1 × V2 or more and 0.1 × V1 or less is smaller than at least one of the absolute value of the second slope of the drive waveform in a second period where the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the drive waveform in a third period where the voltage is 0.6 × V2 or more and 0.4 × V2 or less.

2. The absolute value of the first slope is the average, maximum, or minimum value of the absolute value of the slope of the drive waveform during the first period. The absolute value of the second slope is the average, maximum, or minimum value of the absolute value of the slope of the drive waveform during the second period. The drive device according to claim 1, wherein the absolute value of the third slope is the average, maximum, or minimum value of the absolute value of the slope of the drive waveform during the third period.

3. The absolute value of the first slope is the absolute value of the slope when the voltage is 0V. The absolute value of the second slope is the absolute value of the slope when the voltage is 0.5 × V1. The drive device according to claim 1, wherein the absolute value of the third slope is the absolute value of the slope when the voltage is 0.5 × V².

4. It has a generation unit that generates a pulse waveform including multiple pulse voltages within a predetermined period, The drive device according to claim 1, wherein the selection unit selects one or more pulse voltages from among a plurality of pulse voltages included in the pulse waveform generated by the generation unit to be applied to at least one of the first electrode and the second electrode, according to the input selection information.

5. The drive device according to claim 1, wherein the absolute value of the first slope is smaller than both the absolute value of the second slope and the absolute value of the third slope.

6. The selection unit is configured to include a plurality of electrical circuits corresponding to a plurality of piezoelectric elements, The drive device according to claim 1, wherein the plurality of electrical circuits are formed on the same substrate as the plurality of piezoelectric elements.

7. The liquid discharge head includes a plurality of piezoelectric elements, each having a first electrode and a second electrode, A liquid dispensing device having a drive device according to any one of claims 1 to 5.

8. The aforementioned liquid dispensing head is Multiple nozzles, each dispensing liquid individually, It comprises a plurality of individual liquid chambers communicating with the plurality of nozzles, The liquid dispensing device according to claim 7, wherein the plurality of piezoelectric elements generate pressure to be applied to the liquid in the plurality of individual liquid chambers, corresponding to the plurality of individual liquid chambers.

9. The liquid dispensing device according to claim 8, wherein the piezoelectric element comprises at least one of aluminum nitride and aluminum scandium nitride.

10. A driving method using a drive device for driving a liquid discharge head, which includes a plurality of piezoelectric elements, each having a first electrode and a second electrode, wherein the drive device is The selection unit selects one or more pulse voltages from a pulse waveform including multiple input pulse voltages to be applied to at least one of the first electrode and the second electrode of each of the multiple piezoelectric elements. A drive waveform representing the time change of the voltage applied to the second electrode, with the voltage applied to the first electrode as a reference, is applied to each of the plurality of piezoelectric elements. The drive waveform includes positive and negative voltages and has one or more pulse voltages selected by the selection unit. Let V1 be the maximum voltage of the aforementioned drive waveform. If the minimum voltage of the aforementioned drive waveform is V2, A driving method wherein, during a discharge period corresponding to the period for which liquid is discharged from the liquid discharge head, the absolute value of the first slope of the drive waveform during the period when the voltage is 0.1 × V2 or more and 0.1 × V1 or less is smaller than at least one of the absolute value of the second slope of the drive waveform during the period when the voltage is 0.4 × V1 or more and 0.6 × V1 or less, and the absolute value of the third slope of the drive waveform during the period when the voltage is 0.6 × V2 or more and 0.4 × V2 or less.

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