Patent ID: 12187036

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present disclosure will be described in detail below based on embodiments. However, the following description shows one aspect of the present disclosure, and can be arbitrarily changed within the scope of the present disclosure. In each drawing, the same reference numerals denote the same members, and the description thereof is omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes orthogonal to each other. In the present specification, directions along these axes will be referred to as X, Y, and Z directions. A direction in which the arrow points in each drawing is defined as a positive (+) direction, and a direction opposite to the arrow is defined as a negative (−) direction. The three spatial axes X, Y, and Z, which are not limited to positive and negative directions, will be described as the X axis, Y axis, and Z axis. In each of the following embodiments, as an example, a “first direction” is the +X direction, and a “second direction” is the +Y direction. A “stacking direction” is the −Z direction. However, a description of a configuration in the stacking direction is made with reference to a drawing viewed in the +Z direction.

Embodiment 1

FIG.1is a diagram schematically illustrating an ink jet recording apparatus1as an example of a liquid ejecting apparatus according to Embodiment 1 of the present disclosure.

As illustrated inFIG.1, the ink jet recording apparatus1that is an example of a liquid ejecting apparatus is a printing apparatus that ejects ink, which is a type of liquid, as ink droplets onto a medium S such as printing paper and lands the ink on the medium S, and thus prints an image or the like by arranging dots formed on the medium S. As the medium S, any material may be used.

In the following description, among the three spatial axes of X, Y, and Z, a movement direction of a recording head2that will be described later is defined as an X axis, a transport direction of the medium S orthogonal to the movement direction is defined as a Y axis, a plane parallel to a nozzle surface on which nozzles21of the recording head2are formed is defined as an XY plane, and a direction intersecting the nozzle surface, that is, the XY plane, which is a direction orthogonal to the XY plane in the present embodiment, is defined as a Z axis, and it is assumed that ink droplets are ejected in the +Z direction along the Z axis.

The ink jet recording apparatus1includes a liquid container3, a transport mechanism4that transports the medium S, a control device5, a moving mechanism6, and a recording head2.

The liquid container3individually stores a plurality of types of ink ejected from the recording head2. Examples of the liquid container3include a cartridge attachable to and detachable from the ink jet recording apparatus1, a bag-like ink pack made of a flexible film, and an ink tank capable of replenishing ink.

The control device5, which will be described later in detail, includes, for example, a control processing section such as a central processing unit (CPU) or a field programmable gate array (FPGA), and a storage device such as a semiconductor memory, and comprehensively controls the transport mechanism4, the moving mechanism6, the recording head2, and the like.

The transport mechanism4is controlled by the control device5to transport the medium S along the Y axis, and has, for example, transport rollers4a.

The moving mechanism6is controlled by the control device5to reciprocate the recording head2along the X axis in the +X direction and the −X direction. Specifically, the moving mechanism6of the present embodiment includes a transport body7and a transport belt8. The transport body7is a substantially box-shaped structure that accommodates the recording head2, a so-called carriage, and is fixed to the transport belt8. The transport belt8is an endless belt stretched along the X axis. When the transport belt8is rotated under the control of the control device5, the recording head2is reciprocated together with the transport body7in the +X direction and the −X direction along guide rails (not illustrated). The liquid container3may also be mounted on the transport body7together with the recording head2.

Under the control of the control device5, the recording head2ejects the ink supplied from the liquid container3from each of the plurality of nozzles21as ink droplets onto the medium S in the +Z direction. The ejection of ink droplets from the recording head2is performed in parallel with the transport of the medium S by the transport mechanism4and the reciprocating movement of the recording head2by the moving mechanism6, so that an ink image is formed on the surface of the medium S, that is, so-called printing is performed.

FIG.2is an exploded perspective view of the recording head2that is an example of a liquid ejecting head of the present embodiment.FIG.3is a plan view in which the channel forming substrate10of the recording head2is viewed in the +Z direction.FIG.4is an enlarged plan view of a main portion of the channel forming substrate10of the recording head2.FIG.5is a sectional view of the recording head2taken along line V-V inFIG.3.FIG.6is a sectional view of the recording head2taken along line VI-VI inFIG.4.

As illustrated, the recording head2of the present embodiment includes a channel forming substrate10as an example of a “substrate”. The channel forming substrate10is made of a silicon substrate.

A plurality of pressure chambers12are arranged in the +X direction, which is the first direction, in the channel forming substrate10. The pressure chamber12is formed such that when viewed in the −Z direction, the +X direction is a lateral direction and the +Y direction is a longitudinal direction. In the present embodiment, the pressure chamber12has a rectangular shape when viewed in the −Z direction, but is not particularly limited to this, and may have a parallelogram shape, have a so-called corner-rounded oblong shape (also called a track shape) in which both ends are semicircular based on an oblong shape, or may have a polygonal shape. The plurality of pressure chambers12are arranged on a straight line in the +X direction such that positions thereof in the +Y direction are the same. The pressure chambers12adjacent to each other in the +X direction are partitioned by partition walls11. Of course, the arrangement of the pressure chambers12is not particularly limited to the example inFIG.3.

A shape of the pressure chamber12of the present embodiment when viewed in the +Z direction may be a so-called corner-rounded oblong shape in which both ends in a longitudinal direction are semicircular based on a rectangular shape, a parallelogram shape, or an oblong shape, may be an oval shape such as an elliptical shape or an egg shape, or may be a circular shape, a polygonal shape, or the like. In the present embodiment, the pressure chamber12has a lateral direction in the +X direction and a longitudinal direction in the +Y direction. By arranging the pressure chambers12in the +X direction, which is the lateral direction, the pressure chambers12can be arranged at high density. This pressure chamber12corresponds to a “recess” provided in the “substrate”.

A communication plate15and a nozzle plate20are sequentially stacked on the +Z direction side of the channel forming substrate10. Here, the concept that “A and B are stacked” includes other layers interposed between A and B.

The communication plate15is provided with a nozzle communication passage16that communicates the pressure chamber12and the nozzle21.

The communication plate15is provided with a first manifold portion17and a second manifold portion18that configure a part of a manifold100serving as a common liquid chamber with which the plurality of pressure chambers12commonly communicate. The first manifold portion17is provided to penetrate the communication plate15in the +Z direction. The second manifold portion18is provided to be open on a surface of the communication plate15on the +Z direction side without penetrating the communication plate15in the +Z direction.

The communication plate15is provided with a supply communication passage19that communicates with one end of the pressure chamber12in the direction along the Y axis, independently for each pressure chamber12. The supply communication passage19communicates between the second manifold portion18and the pressure chambers12to supply the ink in the manifold100to the pressure chambers12.

The nozzle plate20is provided on the side of the communication plate15opposite to the channel forming substrate10, that is, on the surface on the +Z direction side.

The nozzle plate20is provided with nozzles21communicating with the respective pressure chambers12via the nozzle communication passages16. In the present embodiment, the plurality of nozzles21are provided in two rows of nozzle rows that are arranged in a row in the +X direction and are spaced apart in the +Y direction. As such a nozzle plate20, a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless steel substrate, an organic material such as a polyimide resin, or the like may be used. A surface of the nozzle plate20in the −Z direction where the nozzles21are open is a liquid ejecting surface20a.

A vibration plate50and a piezoelectric actuator300are sequentially stacked on the surface of the channel forming substrate10on the −Z direction side. That is, the channel forming substrate10, the vibration plate50, and the piezoelectric actuator300are stacked in this order in the −Z direction. Details of the vibration plate50and the piezoelectric actuator300will be described later.

As illustrated inFIGS.2and5, a protective substrate30having approximately the same size as the channel forming substrate10is bonded to the surface of the channel forming substrate10in the −Z direction. The protective substrate30has a holding portion31that is a space that protects the piezoelectric actuator300. The protective substrate30is provided with a through-hole32penetrating in the +Z direction between two holding portions31arranged in the +Y direction. The ends of a first individual lead electrode91, a first common lead electrode92, and a second common lead electrode93drawn out from electrodes of the piezoelectric actuator300extend to be exposed in the through-hole32, and the first individual lead electrode91, the first common lead electrode92, and the second common lead electrode93, and a wiring substrate120coupled to the control device5are electrically coupled to each other within the through-hole32.

As illustrated inFIG.5, a case member40is fixed on the protective substrate30to define, together with the channel forming substrate10, the manifold100communicating with the plurality of pressure chambers12. The case member40has substantially the same shape as that of the communication plate15described above in a plan view in the +Z direction, and is bonded to the protective substrate30and also to the communication plate15described above. In the present embodiment, the case member40is bonded to the communication plate15.

The case member40is provided with a third manifold portion42communicating with the first manifold portion17. The third manifold portion42has a recessed shape that is open on a surface thereof in the +Z direction. The first manifold portion17and the second manifold portion18provided in the communication plate15and the third manifold portion42provided in the case member40configure the manifold100of the present embodiment. The manifold100is provided continuously over the +X direction in which the pressure chambers12are arranged. The case member40is provided with an inlet44that communicates with the manifolds100to supply ink to each of the manifolds100. The case member40is provided with a coupling port43that communicates with the through-hole32of the protective substrate30, which will be described later in detail, and into which the wiring substrate120is inserted.

A compliance substrate45is provided on the surface of the communication plate15on the +Z direction side where the first manifold portion17and the second manifold portion18are open. The compliance substrate45seals the openings of the first manifold portion17and the second manifold portion18on the liquid ejecting surface20aside. Such a compliance substrate45includes a sealing film46made of a flexible thin film and a fixed substrate47made of a hard material such as metal in the present embodiment. Since a region of the fixed substrate47facing the manifold100is an opening48that is completely removed in the thickness direction, one surface of the manifold100is a compliance portion49which is a flexible portion sealed only by the flexible sealing film46.

The vibration plate50and the piezoelectric actuator300of the present embodiment will be described.

As illustrated inFIGS.5and6, the vibration plate50is provided on the channel forming substrate10in the −Z direction, and includes an elastic film51made of silicon oxide provided on the channel forming substrate10side with, and an insulator film52made of zirconium oxide provided on the −Z direction side of the elastic film51. The elastic film51may be formed of a substrate integrated with the channel forming substrate10, and such a structure may also be expressed as “stacked”. Channels such as the pressure chambers12are formed by anisotropically etching the channel forming substrate10, and the surfaces of the pressure chambers12in the −Z direction are defined by the elastic film51. In the present embodiment, the elastic film51and the insulator film52are stacked as the vibration plate50, but the present disclosure is not particularly limited to this.

As illustrated inFIGS.4to6, the piezoelectric actuator300is also referred to as a piezoelectric element, and serves as pressure generating means for causing pressure changes in the ink within the pressure chamber12. The piezoelectric actuator300includes a first electrode61, a second electrode62and a third electrode63, a fourth electrode80and a piezoelectric layer70.

The first electrode61, the second electrode62and the third electrode63are located in the +Z direction relative to the fourth electrode80. That is, the fourth electrode80is located in the −Z direction relative to the first electrode61, the second electrode62and the third electrode63. In other words, the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80are stacked in this order in the −Z direction. Here, the stacking of the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80means that the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80are stacked with other layers interposed therebetween in the direction along the Z axis. In the present embodiment, the piezoelectric actuator300has the piezoelectric layer70between the first electrode61and the fourth electrode80in the direction along the Z axis. The piezoelectric actuator300has a piezoelectric layer70between the second electrode62and the fourth electrode80. The piezoelectric actuator300has the piezoelectric layer70between the third electrode63and the fourth electrode80. The first electrode61does not have the piezoelectric layer70in the +Z direction, which is the pressure chamber12side.

The first electrode61, the second electrode62, and the third electrode63are provided on the surface of the vibration plate50in the −Z direction. That is, the first electrode61, the second electrode62, and the third electrode63are provided at the same position in the direction along the Z axis.

The second electrode62and the third electrode63are provided from the end of the region facing the pressure chamber12to the outside of the pressure chamber12at both ends of the pressure chamber12in the +X direction, that is, the end in the +X direction and the end in the −X direction when viewed in the −Z direction that is a stacking direction. In the present embodiment, the second electrode62is provided from the edge of the region facing the pressure chamber12to the top of the partition wall11outside the pressure chamber12in the −X direction when viewed in the −Z direction at the end of the pressure chamber12in the −X direction. The third electrode63is provided from the edge of the region facing the pressure chamber12to the top of the partition wall11outside the pressure chamber12in the +X direction when viewed in the −Z direction at the end of the pressure chamber12in the +X direction.

The second electrode62and the third electrode63provided for one pressure chamber12are provided to be electrically coupled to each other on the channel forming substrate10. Specifically, the second electrode62and the third electrode63are coupled to a common communication portion64that is continuously provided in the +X direction on one of the outer sides of the pressure chamber12in the direction along the Y axis, and thus are electrically coupled to each other via the common communication portion64. In the present embodiment, the second electrode62, the third electrode63, and the common communication portion64are continuously provided by patterning the same metal layer. Of course, the second electrode62, the third electrode63and the common communication portion64may be formed of different layers. In other words, the fact that the second electrode62and the third electrode63are electrically coupled on the channel forming substrate10also includes the fact that the second electrode62and the third electrode63are electrically coupled via another member. The fact that the second electrode62and the third electrode63are continuous on the channel forming substrate10includes the fact that the second electrode62and the third electrode63are directly continuous on the channel forming substrate10and also includes that the second electrode62and the third electrode63are continuous on the vibration plate50provided on the channel forming substrate10. In other words, the term “on the substrate” includes both “directly on the substrate” and “above” which indicates a state in which another member is interposed.

The second electrode62and the third electrode63are continuously provided without being divided on the partition wall11between the pressure chambers12adjacent to each other in the +X direction. That is, of the two pressure chambers12arranged in the +X direction, the third electrode63provided for one pressure chamber12and the second electrode62provided for the other pressure chamber12are continuously provided on the partition wall11between the two pressure chambers12without interruption. In the present embodiment, the second electrode62and the third electrode63of the two pressure chambers12arranged in the +X direction are separated at the center of the partition wall11in the +X direction and have the names.

The first electrode61is provided between the second electrode62and the third electrode63in the +X direction. Here, the fact that the first electrode61is formed between the second electrode62and the third electrode63in the +X direction means that the center of the first electrode61in the +X direction is located between the respective centers of the second electrode62and the third electrode63in the +X direction. In the present embodiment, the first electrode61, the second electrode62, and the third electrode63are disposed on the same position in the −Z direction by being provided on the flat surface of the vibration plate50in the −Z direction. Therefore, the first electrode61, the second electrode62, and the third electrode63are disposed at positions that do not overlap each other when viewed in the −Z direction. That is, the first electrode61is disposed with a gap between the first electrode61and the second electrode62in the +X direction of the second electrode62, and is disposed with a gap between the first electrode61and the third electrode63in the −X direction of the third electrode63. Of course, when the first electrode61, the second electrode62, and the third electrode63are disposed at different positions in the −Z direction, the first electrode61, and the second electrode62and the third electrode63may be disposed at positions that partially overlap each other when viewed in the −Z direction.

The piezoelectric layer70is continuously provided in the +X direction to have a predetermined width in the +Y direction. That is, the piezoelectric layer70is continuously provided over the first electrode61, the second electrode62, and the third electrode63in the +X direction. The piezoelectric layer70is continuously provided in the +X direction for the plurality of pressure chambers12without interruption. The piezoelectric layer70is provided to have substantially the same thickness in the +X direction. The piezoelectric layer70may have a recess corresponding to each partition wall11. A width of the recess in the +X direction may be smaller than a width of the partition wall11. The recess may be provided to penetrate through the piezoelectric layer70in the +Z direction that is a thickness direction, or may be provided halfway through the thickness of the piezoelectric layer70. That is, the piezoelectric layer70may be completely removed or a part of the piezoelectric layer70may remain on a bottom surface of the recess in the +Z direction.

The piezoelectric layer70on the nozzle21side in the Y axis is formed to be shorter than the end of the first electrode61outside the pressure chamber12, and the end of the first electrode61on the nozzle21side is not covered with the piezoelectric layer70.

The piezoelectric layer70on the opposite side to the nozzle21in the Y axis is formed to be shorter than the ends of the second electrode62and the third electrode63outside the pressure chamber12, and the ends of the second electrode62and the third electrode63opposite to the nozzle21, that is, the portions communicating with the common communication portion64are not covered with the piezoelectric layer70.

Such a piezoelectric layer70is configured by using a piezoelectric material made of a perovskite structure composite oxide represented by the general formula ABO3. As the perovskite structure composite oxide used for the piezoelectric layer70, for example, a lead-based piezoelectric material containing lead or a lead-free piezoelectric material not containing lead may be used. In the present embodiment, lead zirconate titanate (PZT) is used for the piezoelectric layer70.

The fourth electrode80is provided on the surface of the piezoelectric layer70on the −Z direction side. The fourth electrode80covers the pressure chamber12in the +X direction when viewed in the +Z direction. That is, the fourth electrode80is disposed at a position overlapping the pressure chamber12in the +X direction when viewed in the +Z direction. In the present embodiment, the fourth electrode80is provided continuously over the surface of the piezoelectric layer70on the −Z direction side. That is, the fourth electrode80is continuously provided to include positions overlapping the first electrode61, the second electrode62, and the third electrode63when viewed in the +Z direction. In other words, the piezoelectric layer70is formed between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, between the third electrode63and the fourth electrode80. In the present embodiment, since the first electrode61, the second electrode62, and the third electrode63are disposed at the same position in the +Z direction, a distance between the first electrode61and the fourth electrode80is the same as a distance between the second electrode62and the third electrode and the fourth electrode80in the +Z direction.

In such a piezoelectric actuator300, when a voltage is applied between two electrodes facing each other, a portion interposed between the two electrodes and causing piezoelectric strain in the piezoelectric layer70will be referred to as an active portion. In the present embodiment, the portion interposed between the first electrode61and the fourth electrode80will be referred to as a first active portion311, and the portion interposed between the second electrode62and the fourth electrode80will be referred to as a second active portion312, and the portion interposed between the third electrode63and the fourth electrode80will be referred to as a third active portion313. That is, a total of three active portions, that is, one first active portion311, one second active portion312, and one third active portion313are provided for one pressure chamber12. In two pressure chambers12adjacent in the +X direction, the second electrode62provided for one pressure chamber12and the third electrode63provided for the other pressure chamber12are continuous. Therefore, the second active portion312provided for one pressure chamber12and the third active portion313provided for the other pressure chamber12are continuous. In the present embodiment, the second active portion312and the third active portion313of the two pressure chambers12arranged in the +X direction are located at the position separating the second electrode62and the third electrode63, that is, the center of the partition wall11in the +X direction and have the names.

The first electrode61is individually cut for each pressure chamber12to configure an individual electrode provided independently for each active portion. Here, the fact that the first electrode61is an individual electrode of each active portion means that the plurality of first electrodes61provided in the plurality of first active portions311on the channel forming substrate10are not electrically coupled to each other and are provided independently. The term “on the channel forming substrate10” includes both “directly on the channel forming substrate10” as described above and “above” which indicates a state in which another member such as the vibration plate50is interposed.

The second electrode62and the third electrode63configure a common electrode for a plurality of active portions. Here, the fact that the second electrode62is a common electrode for the plurality of active portions means that the plurality of second electrodes62provided in the plurality of second active portions312are electrically coupled to each other on the channel forming substrate10. The fact that the third electrode63is a common electrode for the plurality of active portions means that the plurality of third electrodes63provided in the plurality of third active portions313are electrically coupled to each other on the channel forming substrate10. In the present embodiment, the second electrode62and the third electrode63are electrodes common to the second active portion312and the third active portion313corresponding to one pressure chamber12. Therefore, the second electrode62and the third electrode63are common electrodes that are common to the plurality of second active portions312and the plurality of third active portions313that both correspond to the plurality of pressure chambers12.

By using the second electrode62and the third electrode63as common electrodes for the plurality of second active portions312and the plurality of third active portions313as described above, a space for isolating the second electrode62and the third electrode63on the partition wall11is not necessary, and thus the pressure chambers12can be densely disposed in the +X direction. Since it is not necessary to draw out a wiring individually from the second electrode62and the third electrode63on the channel forming substrate10, a space for drawing out the wiring becomes unnecessary, and thus a size of the recording head2can be reduced.

The fourth electrode80configures a common electrode common to a plurality of active portions. Here, that the fourth electrode80is a common electrode for a plurality of active portions means that the fourth electrode80is commonly provided for all the active portions, that is, the plurality of first active portions311, the plurality of second active portions312, and the plurality of third active portion313.

A portion of the piezoelectric actuator300facing the pressure chamber12in the direction along the Z axis is a flexible portion, and a portion outside the pressure chamber12is a non-flexible portion.

As illustrated inFIG.4, each first electrode61is coupled to a first individual lead electrode91which is a lead wiring. The first individual lead electrode91has one end coupled to one end of the first electrode61and the other end drawn out onto the channel forming substrate10to be disposed between the two rows of pressure chambers12on the Y axis. The first individual lead electrodes91are respectively provided independently for the first electrodes61such that the first electrodes61are not electrically coupled to each other.

As illustrated inFIGS.3and4, the second electrode62and the third electrode63are coupled to a first common lead electrode92which is a lead wiring. The first common lead electrode92has one end coupled to one electrode serving as one end of the second electrode62and the third electrode63disposed in parallel along the X axis, and the other end drawn out to be disposed between two rows of pressure chambers12on the Y axis. Since the second electrode62and the third electrode63are continuously provided, the first common lead electrode92may be coupled to either the second electrode62or the third electrode63.

As illustrated inFIG.3, the fourth electrode80is coupled to a second common lead electrode93which is a lead wiring. The second common lead electrode93has one end coupled to one end of the fourth electrode80in the X axis direction and the other end drawn out to be disposed between the two rows of pressure chambers12on the Y axis.

A wiring substrate120having flexibility is coupled to the ends of the first individual lead electrode91, the first common lead electrode92, and the second common lead electrode93opposite to the ends coupled to the piezoelectric actuator300. A drive circuit121having switching elements for driving the piezoelectric actuator300is mounted on the wiring substrate120. The end of the wiring substrate120opposite to the end coupled to the first individual lead electrode91, the first common lead electrode92, and the second common lead electrode93is coupled to the control device5, and a control signal from the control device5is supplied to the recording head2via the wiring substrate120.

Here, the control device5of the present embodiment will be described with reference toFIG.7.FIG.7is a block diagram illustrating a control configuration of the ink jet recording apparatus1.

As illustrated inFIG.7, the ink jet recording apparatus1includes a printer controller210which is a control section of the present embodiment and a print engine220. The printer controller210is an element that controls the entire ink jet recording apparatus1, and is provided in the control device5provided in the ink jet recording apparatus1in the present embodiment.

The printer controller210includes an external interface211(hereinafter referred to as an external I/F211), a RAM212that temporarily stores various pieces of data, a ROM213that stores control programs and the like, and a control processing section214that includes a CPU and the like. The printer controller210also includes an oscillation circuit215that generates a clock signal, a drive signal generator216that generates a drive signal to be supplied to the recording head2, and an internal interface217(hereinafter referred to as internal I/F217) that transmits dot pattern data (bitmap data) or the like developed based on a drive signal or print data to the print engine220.

The external I/F211receives print data including, for example, character codes, graphic functions, and image data from an external device230such as a host computer. A busy signal (BUSY) and an acknowledge signal (ACK) are output to the external device230via the external I/F211.

The RAM212functions as a reception buffer212A, an intermediate buffer212B, an output buffer212C, and a work memory (not illustrated). The reception buffer212A temporarily stores print data received by the external I/F211, the intermediate buffer212B stores intermediate code data converted by the control processing section214, and the output buffer212C stores dot pattern data. The dot pattern data includes print data obtained by decoding (translating) gradation data.

The ROM213also stores font data, graphic functions, and the like in addition to control programs (control routines) for performing various types of data processing.

The control processing section214reads the print data in the reception buffer212A and stores the intermediate code data obtained by converting the print data in the intermediate buffer212B. The intermediate code data read from the intermediate buffer212B is analyzed, and the intermediate code data is developed into dot pattern data by referring to font data and graphic functions stored in the ROM213. The control processing section214stores the developed dot pattern data in the output buffer212C after applying necessary decoration processing.

When dot pattern data for one line is obtained for the recording head2, this dot pattern data for one line is output to the recording head2via the internal I/F217.

The print engine220includes a recording head2, a transport mechanism4and a moving mechanism6. Since the transport mechanism4and the moving mechanism6have been described above, duplicate descriptions will be omitted.

The recording head2includes a shift register122, a latch circuit123, a level shifter124, and a drive circuit121having a switch125, and the piezoelectric actuator300. These shift register122, latch circuit123, level shifter124, and switch125generate an application pulse from the drive signal generated by the drive signal generator216. Here, the application pulse is actually applied to the piezoelectric actuator300.

Here, a drive waveform representing a drive signal generated by the drive signal generator216will be described.FIG.8illustrates drive waveforms representing a bias potential vbs, a first drive signal201, and a second drive signal202.FIGS.9to13are sectional views taken along the line B-B illustrating a state in which the piezoelectric actuator300and the vibration plate50are deformed by drive signals.

As illustrated inFIG.8, the drive signal generator216generates the first drive signal201and the second drive signal202as drive signals. The first drive signal201is supplied to the first electrode61and the second drive signal202is supplied to the second electrode62and the third electrode63.

The first drive signal201and the second drive signal202are repeatedly generated by the drive signal generator216every unit cycle T defined by a clock signal oscillated from the oscillation circuit215. The unit cycle T is also referred to as an ejection cycle T or a recording cycle T, and corresponds to one pixel of an image or the like printed on a medium S. In the present embodiment, the unit cycle T is divided into two cycles such as a first period T1 and a second period T2.

The first drive signal201is a signal having an ejection pulse DP for driving the first active portion311of the piezoelectric actuator300such that ink droplets are ejected from the nozzle21in the first period T1 within one recording cycle T, and is repeatedly generated every recording cycle T. When a dot pattern for one line (one raster) is formed in a recording region of the medium S during printing, the ejection pulse DP of the first drive signal201is selectively supplied to the first active portion311of the piezoelectric actuator300corresponding to each nozzle21. That is, the control section generates an application pulse from the head control signal and the first drive signal201for each first active portion311corresponding to the nozzle21and supplies the application pulse to the piezoelectric actuator300.

The application pulse generated from the first drive signal201is supplied to the first electrode61that is each individual electrode of the first active portion311. The bias potential vbs is supplied to the fourth electrode80that is a common electrode for the plurality of first active portions311. Therefore, a potential applied to the first electrode61by the application pulse has the bias potential vbs applied to the fourth electrode80as a reference potential. The bias potential vbs supplied to the fourth electrode80corresponds to a “second potential” disclosed in the claims. In the present embodiment, the application pulse supplied to the first electrode61is described by using the first drive signal201. Each potential of the first drive signal201is described as a potential supplied to the first electrode61. However, as described above, the voltage actually applied between the first electrode61and the fourth electrode80is a potential difference between the potential of the first drive signal201supplied to the first electrode61and the bias potential vbs supplied to the fourth electrode80.

The ejection pulse DP includes a first expansion element P1, a first expansion maintaining element P2, a first contraction element P3, a first contraction maintaining element P4, and a first return element P5. The application pulse generated from the first drive signal201always supplies a first potential V1that is an intermediate potential to the first electrode61when the ejection pulse DP is not supplied. Therefore, the unit cycle T of the first drive signal201includes a first reference element B1 and a second reference element B2 that supply the first potential V1before and after the ejection pulse DP. That is, in the first drive signal201, the first reference element B1, the ejection pulse DP, and the second reference element B2 are generated in this order within the unit cycle T. The second reference element B2 is generated in a period including the second period T2.

Such first reference element B1 and second reference element B2 continue to apply the first potential V1larger than the bias potential vbs to the first electrode61, and thus a state in which the piezoelectric actuator300and the vibration plate50are flexurally deformed in the +Z direction on the pressure chamber12side is maintained. Consequently, a volume of the pressure chamber12is maintained as a first volume that is smaller than a reference volume. In the present embodiment, the fact that the piezoelectric actuator300and the vibration plate50are deformed in the +Z direction on the pressure chamber12side means that, as illustrated inFIG.9, the surface of the piezoelectric actuator300in the +Z direction on the pressure chamber12side is deformed into a protruding state in a projection shape. However, when the initial deflection of the piezoelectric actuator300is deformed to protrude in a projection shape toward the −Z side that is the opposite side to the pressure chamber12, a case where the piezoelectric actuator300is deformed in a small amount of protrusion in the −Z direction in a state of being deformed to protrude in a projection shape in the −Z direction by the first reference element B1 and the second reference element B2 is also included. In other words, the fact that the piezoelectric actuator300and the vibration plate are deformed in the +Z direction toward the pressure chamber12side includes a state in which the surface on the −Z side that is the opposite side to the pressure chamber12protrudes in a projection shape. In other words, an attitude of the piezoelectric actuator300by the first reference element B1 and the second reference element B2 is determined depending on the characteristics of the stacked film including the vibration plate50that determine the initial deflection of the piezoelectric actuator300, that is, the internal stress or a position of a neutral line of each film, and a magnitude of the first potential V1by the first reference element B1 and the second reference element B2 with respect to a displacement characteristic of the piezoelectric layer70, that is, an amount of displacement. The reference volume is a volume of the pressure chamber12in a state in which no voltage is applied to the piezoelectric actuator300, that is, a state in which the first active portion311, the second active portion312, and the third active portion313are not driven.

The first expansion element P1 applies the first potential V1to a second potential V2to the first electrode61to deform the piezoelectric actuator300and vibration plate50in the −Z direction, as illustrated inFIG.10. Consequently, the volume of the pressure chamber12is increased from a first volume to a second volume, the meniscus of the ink in the nozzle21is drawn toward the pressure chamber12, and the ink is supplied to the pressure chamber12from the manifold100side.

The first expansion maintaining element P2 continues to apply the second potential V2to the first electrode61to maintain the volume of the pressure chamber12expanded by the first expansion element P1 at the second volume for a certain period of time.

The first contraction element P3 applies the second potential V2to a third potential V3to the first electrode61to deform the piezoelectric actuator300and the vibration plate50in the +Z direction as illustrated inFIG.11. Consequently, the volume of the pressure chamber12is rapidly reduced from the second volume to a third volume, and the ink in the pressure chamber12is pressurized to be ejected as ink droplets from the nozzle21.

The first contraction maintaining element P4 continues to apply the third potential V3to the first electrode61to maintain the volume of the pressure chamber12as a third volume for a certain period of time. While the first contraction maintaining element P4 is being supplied, the ink pressure in the pressure chamber12, which has decreased due to ejection of the ink droplets, attenuates while repeatedly rising and falling due to its natural vibration.

The first return element P5 applies a fourth potential V4to the first potential V1to the first electrode61to deform the piezoelectric actuator300and vibration plate50in the −Z direction as illustrated inFIG.12. Consequently, the volume of the pressure chamber12is increased from the third volume to the first volume and returns.

Thereafter, the second reference element B2 continues to apply the first potential V1to the first active portion311, and thus the volume of the pressure chamber12is maintained as the first volume contracted from the reference volume.

In such a first drive signal201, the ejection pulse DP is not supplied to the first electrode61of the first active portion311of the piezoelectric actuator300that does not eject ink droplets, and the first potential V1of the first reference element B1 and the second reference element B2 is applied as an intermediate potential.

As illustrated inFIG.8, the second drive signal202is repeatedly generated by the drive signal generator216every unit cycle T defined by the clock signal oscillated from the oscillation circuit215. In the present embodiment, the second drive signal is a signal having a damping pulse SVP for driving the second active portion312and the third active portion313of the piezoelectric actuator300such that ink droplets are not ejected from the nozzles21in the second period T2 within one recording cycle T, and is repeatedly generated every recording cycle T. When a dot pattern for one line (for one raster) is formed in the recording region of the medium S during printing, the damping pulse SVP of the second drive signal202is selectively applied to the second active portion312and the third active portion313of the piezoelectric actuator300corresponding to each nozzle21. That is, the control section generates application pulses for the second active portion312and the third active portion313corresponding to each nozzle21from the head control signal and the second drive signal202, and supplies the application pulses to the piezoelectric actuator300.

The application pulse generated from the second drive signal202is supplied to the second electrode62and the third electrode63that are common electrodes for the plurality of second active portions312and the plurality of third active portions313. The bias potential vbs is supplied to the fourth electrode80that is a common electrode for the plurality of second active portions312and the plurality of third active portions313, as described above. Therefore, a potential applied to the second electrode62and the third electrode63due to the application pulse has the bias potential vbs applied to the fourth electrode80as a reference potential. In the present embodiment, the application pulse supplied to the second electrode62and the third electrode63is described by using the second drive signal202. Each potential of the second drive signal202is described as a potential supplied to the second electrode62and the third electrode63. However, as described above, a voltage actually applied between the second electrode62and the third electrode63and the fourth electrode80is a potential difference between a potential of the second drive signal202supplied to the second electrode62and the third electrode63and the bias potential vbs supplied to the fourth electrode80.

Here, the damping pulse SVP supplied to the second electrode62and the third electrode63includes a second expansion element P10, a second expansion maintaining element P11, and a second return element P12. The application pulse generated from the second drive signal202always supplies a fourth potential V4that is an intermediate potential to the second electrode62and the third electrode63when the damping pulse SVP is not supplied. Therefore, the unit cycle T of the second drive signal202includes a third reference element B3 and a fourth reference element B4 that supply the fourth potential V4before and after the damping pulse SVP. That is, in the second drive signal202, the third reference element B3, the damping pulse SVP, and the fourth reference element B4 are generated in this order within the unit cycle T. The third reference element B3 is generated in a period including the first period T1.

Such third reference element B3 and fourth reference element B4 supply the fourth potential V4that is the same as the bias potential vbs to the second electrode62and the third electrode63such that a state in which the second active portion312and the third active portion313is not driven is maintained. The third reference element B3 is supplied during the first period T1 during which the piezoelectric actuator300is driven by the ejection pulse DP. Therefore, when the first active portion311is driven by the ejection pulse DP and ink droplets are ejected from the nozzle21, the second active portion312and the third active portion313are not driven, and thus the damping pulse SVP does not influence the ejection of ink droplets using the ejection pulse DP. Since the third reference element B3 does not drive the second active portion312and the third active portion313, after the first period T1 of the third reference element B3, the volume of the pressure chamber12is same as after the ejection pulse DP, that is, the first volume by the second reference element B2.

The second expansion element P10, the second expansion maintaining element P11, and the second return element P12 are supplied to the second electrode62and the third electrode63during the second period T2, that is, while the second reference element B2 of the first drive signal201is being supplied.

The second expansion element P10 applies a fifth potential V5to the second electrode62and the third electrode63to deform the piezoelectric actuator300and vibration plate50in the −Z direction that is an opposite side to the pressure chamber12as illustrated inFIG.13. Consequently, the volume of the pressure chamber12is increased from the first volume to the fourth volume.

The second active portion312and the third active portion313are provided to straddle the wall of the pressure chamber12from the region overlapping the pressure chamber12to the region overlapping the partition wall11when viewed in the +Z direction. Therefore, when the second active portion312and the third active portion313are driven, the piezoelectric actuator300and the vibration plate50are deformed in the −Z direction on the opposite side to the pressure chamber12. The fact that the piezoelectric actuator300and the vibration plate50are deformed in the −Z direction on the opposite side to the pressure chamber12means that, in the present embodiment, the surface of the piezoelectric actuator300in the −Z direction on the opposite side to the pressure chamber12is deformed into a protruding state in a projection shape as illustrated inFIG.13. However, when the initial deflection of the piezoelectric actuator300and the vibration plate50, that is, in the present embodiment, a state in which the piezoelectric actuator300and the vibration plate50are deformed by the second reference element B2 is deformed such that the surface in the +Z direction protrudes in a projection shape, a case where the piezoelectric actuator300and the vibration plate50are deformed in a small amount of protrusion in the +Z direction in a state of being deformed to protrude in a projection shape in the +Z direction by the second expansion element P10. In other words, the fact that the piezoelectric actuator300and the vibration plate50are deformed in the −Z direction on the opposite side to the pressure chamber12also includes a state in which the surface in the +Z direction on the pressure chamber12side protrudes in a projection shape. The attitude of the piezoelectric actuator300and the vibration plate50by the second expansion element P10 is determined depending on an attitude of the piezoelectric actuator300at the second reference element B2 and a magnitude of a fifth potential V5, that is, an amount of displacement.

The fifth potential V5of the second expansion element P10 is preferably the same potential as the first potential V1of the first reference element B1 or the third potential V3of the first contraction element P3 of the first drive signal201. By setting the fifth potential V5of the second expansion element P10 to the same potential as the first potential V1of the first reference element B1 of the first drive signal201or the third potential V3of the first contraction element P3, a circuit of the drive signal generator216can be simplified compared with a case of generating different potentials.

The second expansion maintaining element P11 continues to apply the fifth potential V5to the second electrode62and the third electrode63to maintain the volume of the pressure chamber12expanded by the second expansion element P10 as the fourth volume for a certain period of time.

The second return element P12 applies the fifth potential V5to fourth potential V4to the second electrode62and the third electrode63to deform the piezoelectric actuator300and vibration plate50in the +Z direction. Consequently, the volume of the pressure chamber12is reduced from the fourth volume and returned to the first volume.

By inserting the second expansion element P10, the second expansion maintaining element P11, and the second return element P12 of the damping pulse SVP after the ejection pulse DP as described above, residual vibration of the ink in the pressure chamber12after the ink is ejected from the nozzle21can be converged in a short time. In other words, when the second active portion312and the third active portion313of the piezoelectric actuator300are driven by the damping pulse SVP, the second active portion312and the third active portion313contract along the Z axis as illustrated inFIG.13, and the piezoelectric actuator300and the vibration plate50are deformed to protrude in a projection shape in the −Z direction on the opposite side to the pressure chamber12. In this case, a tensile stress is applied to the portion including the first active portion311interposed between the second active portion312and the third active portion313, and thus the apparent Young's modulus increases. Since the apparent Young's modulus of the piezoelectric actuator300increases, the residual vibration of the ink in the pressure chamber12after the ink is ejected can be converged in a short time.

The second active portion312and the third active portion313of the piezoelectric actuator300are driven by the damping pulse SVP such that the piezoelectric actuator300is deformed to protrude in a projection shape in the −Z direction on the opposite side to the pressure chamber12, and thus the residual strain of the piezoelectric layer70can be eliminated. In other words, by repeatedly driving the piezoelectric actuator300with the ejection pulse DP, the piezoelectric actuator300is repeatedly deformed to protrude in a projection shape only in one direction, in the present embodiment, in the +Z direction on the pressure chamber12side. Thus, the residual strain is generated in the piezoelectric layer70, and the original state cannot be restored even when the piezoelectric actuator300is not driven. When the residual strain of the piezoelectric actuator300is large, an amount of displacement of the piezoelectric actuator300is reduced when the piezoelectric actuator300is driven, and ejection characteristics such as a weight and a flight speed of ink droplets deteriorate. In the present embodiment, by driving the piezoelectric actuator300with the damping pulse SVP, the piezoelectric actuator300can be deformed to protrude in a projection shape in a direction different from the ejection pulse DP, that is, in the −Z direction. Therefore, it is possible to eliminate the residual strain of the piezoelectric layer70and curb the decrease in an amount of displacement of the piezoelectric actuator300even when the piezoelectric actuator300is repeatedly driven. Therefore, it is possible to curb deterioration in the ejection characteristics of the ink droplets ejected from the nozzles21.

Since the second electrode62and the third electrode63are common electrodes for the plurality of second active portions312and the plurality of third active portions313, the second active portion312and the third active portion313corresponding to the pressure chambers12communicating with the nozzles21that do not eject ink droplets are simultaneously driven by the damping pulse SVP. However, since the piezoelectric actuator300is driven by the damping pulse SVP not to eject ink droplets, there is no particular problem even when the second active portion312and the third active portion313corresponding to the nozzles21that do not eject ink droplets are driven by the damping pulse SVP. Since the damping pulse SVP also functions as a so-called micro-vibration pulse, by driving the second active portion312and the third active portion313corresponding to the nozzles21that do not eject ink droplets with the damping pulse SVP, the ink in the vicinity of the nozzle21can be slightly vibrated. Therefore, it is possible to curb sedimentation of components contained in the ink in the vicinity of the pressure chamber12and the nozzle21or to curb accumulation of thickened ink, and thus to curb ejection failure of ink droplets due to the thickened ink. That is, it is preferable to supply the damping pulse SVP to the second electrode62and the third electrode63corresponding to the pressure chamber12communicating with the nozzle21to which the ejection pulse is not supplied.

In the configuration described above, the bias potential vbs is supplied to the fourth electrode80, and the fifth potential V5that is the same as the bias potential vbs is supplied to the second electrode62and the third electrode63by the third reference element B3 and the fourth reference element B4. However, it is not particularly limited to this. For example, the bias potential vbs may not be supplied to the fourth electrode80, but may be ground (GND), and the fifth potential V5of the third reference element B3 and the fourth reference element B4 may be ground (GND).

Here, a modification example of the control section of the present embodiment will be described with reference toFIG.14.FIG.14illustrates drive waveforms representing the bias potential vbs, the first drive signal201, and the third drive signal203.

As illustrated inFIG.14, the third drive signal203is supplied to the second electrode62and the third electrode63. The damping pulse SVP is not provided in the third drive signal203. The third drive signal203always supplies a sixth potential V6that is an intermediate potential to the second electrode62and the third electrode63. In other words, it can be said that the third drive signal203includes a fifth reference element B5 that supplies the sixth potential V6.

Here, the sixth potential V6supplied to the second electrode62and the third electrode63is a potential different from supplied to the fourth electrode80, that is, the bias potential vbs in the present embodiment. The sixth potential V6in the present embodiment is preferably higher than the bias potential vbs. That is, it is preferable to satisfy the relationship of the sixth potential V6>the bias potential vbs. By setting the sixth potential V6to a potential higher than the bias potential vbs as described above, it is possible to suppress application of an electric field reverse to the ejection pulse DP to the piezoelectric actuator300. Therefore, it is possible to curb the piezoelectric actuator300from being cracked or destroyed. This sixth potential V6corresponds to a “first potential” in Embodiment 1. That is, in the configuration illustrated inFIG.8, the fourth potential V4is the same potential as the bias potential vbs supplied to the fourth electrode80, and in the configuration illustrated inFIG.14, the sixth potential V6is higher than the bias potential vbs that is a “second potential”. As a condition for satisfying both of the configurations inFIGS.8and14, a potential supplied to the second electrode62and the third electrode63the bias potential vbs.

By constantly supplying the sixth potential V6to the second electrode62and the third electrode63while the ejection pulse DP is being supplied to the first electrode61, it is possible to eliminate an increase in residual strain that occurs when the piezoelectric actuator300is repeatedly driven by the ejection pulse DP even when the damping pulse SVP is not supplied and to curb a decrease in displacement due to repeated driving. By maintaining a state in which the sixth potential V6is supplied to the second electrode62and the third electrode63, a natural vibration cycle Tc of the pressure chamber12can be adjusted. Here, the magnitude of the sixth potential V6supplied to the second electrode62and the third electrode63and the magnitude of the natural vibration cycle Tc of the pressure chamber12have an inversely proportional relationship. Therefore, by supplying the sixth potential V6to the second electrode62and the third electrode63, the natural vibration cycle Tc of the pressure chamber12can be reduced, and ink droplets can be continuously ejected at a high speed. In a head unit in which a plurality of recording heads2are unitized or in the ink jet recording apparatus1having a plurality of recording heads2, even when there is a variation in the natural vibration cycle Tc among the plurality of recording heads2, by changing the sixth potential V6for each recording head2, the variation in the natural vibration cycle Tc among the plurality of recording heads2can be reduced. Therefore, it is possible to curb variations in ejection characteristics such as ink weight and ejection speed of ink droplets ejected from a plurality of recording heads2.

The configuration in which the sixth potential V6is constantly supplied to the second electrode62and the third electrode63while the ejection pulse DP is being supplied to the first electrode61may be applied to the second drive signal202having the damping pulse SVP. Here,FIG.15illustrates a configuration in which the sixth potential V6is applied to the second drive signal202.FIG.15illustrates drive waveforms showing modification examples of the bias potential vbs, the first drive signal201, and the second drive signal202.

As illustrated inFIG.15, the second drive signal202always supplies the sixth potential V6that is an intermediate potential to the second electrode62and the third electrode63when the damping pulse SVP is not supplied. That is, the second drive signal202has the third reference element B3, the damping pulse SVP, and the fourth reference element B4, and supplies the sixth potential V6to the second electrode62and the third electrode63in the third reference element B3 and the fourth reference element B4.

The third reference element B3 and the fourth reference element B4 supply the sixth potential V6higher than the bias potential vbs to the second electrode62and the third electrode63. In other words, the third reference element B3 supplies the sixth potential V6to the second electrode62and the third electrode63during the first period T1 during which the ejection pulse DP is supplied to the first electrode61. Therefore, the natural vibration cycle Tc of the pressure chamber12can be reduced while the ejection pulse DP is being supplied, and the natural vibration cycle Tc can be adjusted. Since the second drive signal202has the damping pulse SVP, the same effects as those described above due to the damping pulse SVP can be achieved.

In the example illustrated inFIG.15, the waveform of the damping pulse SVP is the same as that inFIG.8such that the fourth potential V4is a potential higher than the third potential V3, but the present disclosure is not particularly limited to this, and the fourth potential V4may be the same potential as the third potential V3. Consequently, it is possible to simplify a circuit of the drive signal generator216compared with a case where different potentials such as the fourth potential V4and the third potential V3are generated.

As described above, the recording head2that is an example of a piezoelectric device of the present disclosure includes the channel forming substrate10that is a substrate on which the pressure chambers12which are recesses communicating with the nozzles21for ejecting a liquid are arranged in the +X direction that is the first direction, the vibration plate50, and the piezoelectric actuator300. The piezoelectric actuator300has the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80in this order. The piezoelectric actuator300has the piezoelectric layers70between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, and between the third electrode63and the fourth electrode80. The plurality of first active portions311, the plurality of second active portions312and the plurality of third active portions313, which are active portions in which the piezoelectric layer70is interposed between the first electrode61, the second electrode62, and the third electrode63, and the fourth electrode80, are provided. The second electrode62and the third electrode63are provided at both ends of the pressure chamber12in the +X direction from the edge of the region facing the pressure chamber12to the outside of the pressure chamber12when viewed in the −Z direction that is a stacking direction. The first electrode61is formed between the second electrode62and the third electrode63in the +X direction, and the fourth electrode80configures a common electrode for the plurality of first active portions311, second active portions312, and third active portions313.

As described above, the first electrode61that drives the piezoelectric actuator300to be deformed toward the pressure chamber12side, and the second electrode62and the third electrode63that drive the piezoelectric actuator300to be deformed toward the opposite side to the pressure chamber12are provided. Therefore, compared with a case where the piezoelectric actuator300is deformed only in one direction along the Z axis, the residual strain in the piezoelectric layer70is less likely to occur even when the piezoelectric actuator300is repeatedly driven. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to curb a decrease in an amount of displacement. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to prevent deterioration in the ejection characteristics such as the ink weight of ink droplets ejected from the nozzles21and to continue high-quality printing. An amount of displacement can be improved compared with a case where the piezoelectric actuator300is driven only in one direction along the Z axis. Therefore, the weight of ink droplets ejected from the nozzles21can be increased.

The recording head2that is an example of a piezoelectric device of the present disclosure includes the channel forming substrate10that is a substrate on which the pressure chambers12which are recesses communicating with the nozzles21for ejecting a liquid are arranged in the +X direction that is the first direction, the vibration plate50, and the piezoelectric actuator300. The piezoelectric actuator300has the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80in this order. The piezoelectric actuator300has the piezoelectric layers70between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, and between the third electrode63and the fourth electrode80. The plurality of first active portions311, the plurality of second active portions312and the plurality of third active portions313, which are active portions in which the piezoelectric layer70is interposed between the first electrode61, the second electrode62, and the third electrode63, and the fourth electrode80, are provided. The second electrode62and the third electrode63are provided at both ends of the pressure chamber12in the +X direction from the edge of the region facing the pressure chamber12to the outside of the pressure chamber12when viewed in the −Z direction that is a stacking direction. The first electrode61is formed between the second electrode62and the third electrode63in the +X direction, and the second electrode62, the third electrode63, and the fourth electrode80configure common electrodes for the plurality of first active portions311, second active portions312, and third active portions313, and the first electrode61configures an individual electrode provided independently for each of the first active portions311.

As described above, the first electrode61that drives the piezoelectric actuator300to be deformed toward the pressure chamber12side, and the second electrode62and the third electrode63that drive the piezoelectric actuator300to be deformed toward the opposite side to the pressure chamber12are provided. Therefore, the residual strain of the piezoelectric layer70when the piezoelectric actuator300is repeatedly driven can be reduced, and a decrease in displacement due to repeated driving can be curbed. Therefore, when the piezoelectric actuator300is repeatedly driven, it is possible to curb the deterioration in the ejection characteristics such as a weight and a flight speed of ink droplets ejected from the nozzles21.

The second electrode62configures a common electrode for the plurality of second active portions312, and the third electrode63configures a common electrode for the plurality of third active portions313. Therefore, it is possible to reduce the number of second common lead electrodes93, which are lead wirings drawn out from the second electrode62and the third electrode63. Therefore, it is possible to reduce a size of the recording head2by reducing a space in which a wiring is routed and reducing an area of the channel forming substrate10in the XY plane.

The piezoelectric layer70and the fourth electrode80do not need to be patterned in accordance with the first electrode61. That is, the piezoelectric layer70and the fourth electrode80can be formed with substantially uniform thickness over the first electrode61, the second electrode62and the third electrode63. Therefore, it is possible to prevent the piezoelectric layer70from being degraded due to patterning, and it is possible to prevent the piezoelectric characteristics from partially deteriorating.

In the recording head2of the present embodiment, a gap between the first electrode61and the fourth electrode80and a gap between the second electrode62and the third electrode63and the fourth electrode80in the −Z direction that is a stacking direction are preferably the same. According to this, a structure can be simplified, the number of manufacturing steps can be reduced, and cost can be reduced. Since the gaps are the same, variations in residual strain in the piezoelectric layer70are less likely to occur that is preferable.

In the recording head2of the present embodiment, it is preferable that the piezoelectric layer70is not provided on the pressure chamber12side that is a recess of the first electrode61. According to this, the piezoelectric layer70that increases the dielectric loss tangent tan 6 is not present on the pressure chamber12side of the first electrode61, and heat generation due to dielectric loss is less likely to occur when the piezoelectric actuator300is driven, and thus the temperature of the ink in the pressure chamber12is less likely to increase.

In the recording head2of the present embodiment, it is preferable that the first electrode61, and the second electrode62and the third electrode63do not overlap each other in the +X direction that is the first direction when viewed in a stacking direction. The first electrode61, and the second electrode62and the third electrode63can be prevented from being electrically coupled. The first electrode61, and the second electrode62and the third electrode63do not overlap in the +X direction, and can thus be formed at the same position in the −Z direction. Therefore, the first electrode61, and the second electrode62, and the third electrode63can be simultaneously formed at the same layer, and the number of manufacturing steps can be reduced, and thus cost can be reduced.

In the recording head2of the present embodiment, the fourth electrode80preferably covers the pressure chamber12that is a recess in the +X direction that is the first direction when viewed in the −Z direction that is a stacking direction. Since the first electrode61and the piezoelectric layer70provided in the −Z direction of the pressure chamber12are covered with the fourth electrode80, the piezoelectric layer70is prevented from being damaged by moisture, and thus shortening of the life of the piezoelectric layer70can be curbed.

In the recording head2of the present embodiment, it is preferable that the pressure chamber12that is a recess has, as a longitudinal direction, the +Y direction that is the second direction perpendicular to the +X direction that is the first direction, when viewed in the −Z direction that is a stacking direction. According to this, the pressure chambers12can be densely disposed in the +X direction while ensuring the volume of the pressure chambers12.

In the recording head2of the present embodiment, the vibration plate50preferably contains zirconium oxide. When a material containing lead is used for the piezoelectric layer70, it is possible to suppress diffusion of lead into the vibration plate50.

The ink jet recording apparatus1that is an example of a liquid ejecting apparatus of the present disclosure includes the recording head2described above. It is possible to implement a highly reliable ink jet recording apparatus1in which printing quality does not easily deteriorate even after repeated printing.

The ink jet recording apparatus1that is an example of the liquid ejecting apparatus of the present embodiment includes the channel forming substrate10that is a substrate on which the pressure chambers12which are recesses communicating with the nozzles21for ejecting a liquid are arranged in the +X direction that is the first direction, the vibration plate50, the piezoelectric actuator300, and the control section that drives the piezoelectric actuator300. The piezoelectric actuator300has the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80in this order. The piezoelectric actuator300has the piezoelectric layers70between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, and between the third electrode63and the fourth electrode80. The plurality of first active portions311, the plurality of second active portions312and the plurality of third active portions313, which are active portions in which the piezoelectric layer70is interposed between the first electrode61, the second electrode62, and the third electrode63, and the fourth electrode80, are provided. The second electrode62and the third electrode63are provided at both ends of the pressure chamber12in the +X direction from the edge of the region facing the pressure chamber12to the outside of the pressure chamber12when viewed in the −Z direction that is a stacking direction. The first electrode61is formed between the second electrode62and the third electrode63in the +X direction, and the second electrode62, the third electrode63, and the fourth electrode80configure common electrodes for the plurality of first active portions311, second active portions312, and third active portions313, and the first electrode61configures an individual electrode provided independently for each of the first active portions311. The control section supplies the first electrode61with the ejection pulse DP for ejecting a liquid from the nozzle21. The control section supplies the second electrode62and the third electrode63with the damping pulse SVP for driving the piezoelectric actuator300such that the liquid is not ejected from the nozzle21at least after the ejection pulse DP.

As described above, the control section supplies the ejection pulse DP to the first electrode61to deform the piezoelectric actuator300toward the pressure chamber12when ink droplets are ejected. By supplying the damping pulse SVP after the ejection pulse DP, the piezoelectric actuator300is deformed toward the opposite side to the pressure chamber12. Therefore, even when ink droplets are repeatedly ejected with the ejection pulse DP, by supplying the damping pulse SVP, an increase in the residual strain of the piezoelectric layer70can be curbed, and a reduction in an amount of displacement due to repeated driving of the piezoelectric actuator300can be curbed. By inserting the damping pulse SVP after the ejection pulse DP, the apparent Young's modulus of the piezoelectric layer70can be increased, and the residual vibration after the ejection pulse DP can be converged in a short time. Therefore, ejection of ink droplets can be repeated in a short time, and high-speed continuous ejection can be realized. By supplying the damping pulse SVP to the second electrode62and the third electrode63corresponding to the pressure chamber12that does not eject ink droplets, the ink in the vicinity of the pressure chambers12and the nozzles21is slightly vibrated. Therefore, it is possible to curb sedimentation of components contained in the ink or to curb accumulation of thickened ink, and thus to curb ejection failure of ink droplets due to the thickened ink.

In the ink jet recording apparatus1of the present embodiment, the control section preferably deforms the vibration plate50to project on the opposite side to the pressure chamber12with the damping pulse SVP. As described above, the vibration plate50is deformed to project in the −Z direction on the opposite side to the pressure chamber12with the damping pulse SVP such that it is possible to reduce the residual strain of the piezoelectric layer70due to repeated driving using the ejection pulse DP.

In the ink jet recording apparatus1of the present embodiment, the control section preferably deforms the vibration plate50to project toward the pressure chamber12side with the ejection pulse DP. According to this, the driving efficiency of the piezoelectric actuator300becomes favorable, and the ejection characteristics of ink droplets can be improved.

In the ink jet recording apparatus1of the present embodiment, it is preferable that the control section supplies the first drive signal201including the ejection pulse DP to the first electrode61, and supplies the sixth potential V6that is a first potential different from a potential supplied to the fourth electrode80to the second electrode62and the third electrode63while the first drive signal201is being supplied to the first electrode61. According to this, while the first drive signal201is being supplied to the first electrode61, by maintaining the state in which the sixth potential V6is supplied to the second electrode62and the third electrode63, the natural vibration cycle Tc of the pressure chamber12can be adjusted. Therefore, it is possible to reduce the natural vibration cycle Tc of the pressure chamber12and continuously eject ink droplets at a high speed. In a head unit in which a plurality of recording heads2are unitized or in the ink jet recording apparatus1having a plurality of recording heads2, even when there is a variation in the natural vibration cycle Tc among the plurality of recording heads2, by changing the sixth potential V6for each recording head2, the variation in the natural vibration cycle Tc among the plurality of recording heads2can be reduced. Therefore, it is possible to curb variations in ejection characteristics such as ink weight and ejection speed of ink droplets ejected from a plurality of recording heads2. In the example described above, the bias potential vbs is supplied to the fourth electrode80, but the present disclosure is not particularly limited to this, and the fourth electrode80may be ground (GND).

The ink jet recording apparatus1that is an example of the liquid ejecting apparatus of the present embodiment includes the channel forming substrate10that is a substrate on which the pressure chambers12which are recesses communicating with the nozzles21for ejecting a liquid are arranged in the +X direction that is the first direction, the vibration plate50, the piezoelectric actuator300, and the control section that drives the piezoelectric actuator300. The piezoelectric actuator300has the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80in this order. The piezoelectric actuator300has the piezoelectric layers70between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, and between the third electrode63and the fourth electrode80. The plurality of first active portions311, the plurality of second active portions312and the plurality of third active portions313, which are active portions in which the piezoelectric layer70is interposed between the first electrode61, the second electrode62, and the third electrode63, and the fourth electrode80, are provided. The second electrode62and the third electrode63are provided at both ends of the pressure chamber12in the +X direction from the edge of the region facing the pressure chamber12to the outside of the pressure chamber12when viewed in the −Z direction that is a stacking direction. The first electrode61is formed between the second electrode62and the third electrode63in the +X direction, and the second electrode62, the third electrode63, and the fourth electrode80configure common electrodes for the plurality of first active portions311, second active portions312, and third active portions313, and the first electrode61configures an individual electrode provided independently for each of the first active portions311. The control section supplies the first drive signal201including the ejection pulse DP for ejecting a liquid from the nozzle21to the first electrode61. The control section supplies the sixth potential V6that is a first potential different from the potential supplied to the fourth electrode80to the second electrode62and the third electrode63while the first drive signal201is being supplied to the first electrode61.

According to this, while the first drive signal201is being supplied to the first electrode61, by maintaining the state in which the sixth potential V6is supplied to the second electrode62and the third electrode63, the natural vibration cycle Tc of the pressure chamber12can be adjusted. Therefore, it is possible to reduce the natural vibration cycle Tc of the pressure chamber12and continuously eject ink droplets at a high speed. In a head unit in which a plurality of recording heads2are unitized or in the ink jet recording apparatus1having a plurality of recording heads2, even when there is a variation in the natural vibration cycle Tc among the plurality of recording heads2, by changing the sixth potential V6for each recording head2, the variation in the natural vibration cycle Tc among the plurality of recording heads2can be reduced. Therefore, it is possible to curb variations in ejection characteristics such as ink weight and ejection speed of ink droplets ejected from a plurality of recording heads2. In the example described above, the bias potential vbs is supplied to the fourth electrode80, but the present disclosure is not particularly limited to this, and the fourth electrode80may be ground (GND).

In the ink jet recording apparatus1of the present embodiment, it is preferable that while the first drive signal201is being supplied, the control section supplies the bias potential vbs that is a second potential to the fourth electrode80, and the sixth potential V6that is a first potential is equal to or higher than the bias potential vbs. By setting the sixth potential V6to a potential higher than the bias potential vbs as described above, it is possible to suppress application of an electric field reverse to the ejection pulse DP to the piezoelectric actuator300. Therefore, it is possible to curb the piezoelectric actuator300from being cracked or destroyed.

Embodiment 2

FIG.16is an enlarged plan view of a main portion of a channel forming substrate10of a recording head2that is an example of a liquid ejecting head according to Embodiment 2 of the present disclosure when viewed in the +Z direction.FIG.17is a sectional view taken along the line XVII-XVII inFIG.16. The same reference numeral is given to a member similar to that of the above embodiment, and the redundant description will be omitted.

As illustrated, a piezoelectric actuator300includes a first electrode61, a second electrode62, a third electrode63, a piezoelectric layer70, and a fourth electrode80for one pressure chamber12.

The first electrode61, the second electrode62and the third electrode63are located in the +Z direction relative to the fourth electrode80. That is, the fourth electrode80is located in the −Z direction relative to the first electrode61, the second electrode62and the third electrode63. In other words, the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80are stacked in this order in the −Z direction. Here, the stacking of the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80means that the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80are stacked with other layers interposed therebetween in the direction along the Z axis. In the present embodiment, the piezoelectric actuator300has the piezoelectric layer70between the first electrode61and the fourth electrode80in the direction along the Z axis. The piezoelectric actuator300has a piezoelectric layer70between the second electrode62and the fourth electrode80. The piezoelectric actuator300has the piezoelectric layer70between the third electrode63and the fourth electrode80.

The first electrode61, the second electrode62, and the third electrode63are provided on the surface of the vibration plate50in the −Z direction. That is, the first electrode61, the second electrode62, and the third electrode63are provided at the same position in the direction along the Z axis.

The second electrode62and the third electrode63are provided from the end of the region facing the pressure chamber12to the outside of the pressure chamber12at both ends of the pressure chamber12in the +X direction, that is, the end in the +X direction and the end in the −X direction when viewed in the −Z direction that is a stacking direction. In the present embodiment, the second electrode62is provided from the edge of the region facing the pressure chamber12to the top of the partition wall11outside the pressure chamber12in the −X direction when viewed in the −Z direction at the end of the pressure chamber12in the −X direction. The third electrode63is provided from the edge of the region facing the pressure chamber12to the top of the partition wall11outside the pressure chamber12in the +X direction when viewed in the −Z direction at the end of the pressure chamber12in the +X direction.

The second electrode62and the third electrode63are separated for each pressure chamber12to form individual electrodes provided independently for each active portion. Here, the fact that the second electrode62and the third electrode63are individual electrodes for the active portions means that, in the present embodiment, a plurality of second electrodes62provided for the plurality of second active portions312on the channel forming substrate10are not electrically coupled to each other and are provided independently. The term “on the channel forming substrate10” includes a state directly on the channel forming substrate10as described above and a state in which another member such as the vibration plate50is interposed, that is, the so-called “above”. In the two pressure chambers12arranged in the +X direction, the second electrode62of one pressure chamber12and the third electrode63of the other pressure chamber12are disposed with a gap so as not to communicate with each other on the partition wall11that separates the two pressure chambers12in the +X direction.

In the present embodiment, the second electrode62and the third electrode63provided for one pressure chamber12are electrically coupled to each other on the channel forming substrate10. Specifically, the second electrode62and the third electrode63are coupled to an individual communication portion64A that is separated and independently provided for each pressure chamber12on one of the outer sides of the pressure chambers12in the direction along the Y axis, and are electrically coupled to each other via the individual communication portion64A. In the present embodiment, the second electrode62, the third electrode63, and the individual communication portion64A are continuously provided by patterning the same metal layer. Of course, the second electrode62, the third electrode63, and the individual communication portion64A may be formed of different layers. In other words, the fact that the second electrode62and the third electrode63are electrically coupled on the channel forming substrate10also includes the fact that the second electrode62and the third electrode63are electrically coupled via another member. The fact that the second electrode62and the third electrode63provided to correspond to one pressure chamber12are continuous on the channel forming substrate10includes that the second electrode62and the third electrode63are directly on and above the channel forming substrate10. By electrically coupling the second electrode62and the third electrode63provided to correspond to one pressure chamber12as described above, it is not necessary to provide a lead wiring for each of the second electrode62and the third electrode63or to couple terminals of the wiring substrate120. Therefore, a space for routing wiring and a space for coupling the wiring substrate120on the channel forming substrate10are not required, and thus an area of the channel forming substrate10along the XY plane can be reduced. However, by electrically coupling the second electrode62and the third electrode63provided to correspond to one pressure chamber12, the second active portion312and the third active portion313cannot be driven individually and are driven at the same time. A second individual lead electrode94that is a lead wiring is coupled to the individual communication portion64A. The second individual lead electrode94is provided along the Y axis such that one end is coupled to the individual communication portion64A and the other end is disposed outside the two rows of pressure chambers on the Y axis. Thus, a wiring substrate different from the wiring substrate120is coupled to the second individual lead electrode94although not illustrated. Of course, a second individual lead electrode94may be drawn out in the same direction as the first individual lead electrode91from either the second electrode62or the third electrode63provided for one pressure chamber12. The first individual lead electrode91and the second individual lead electrode94are drawn out in the same direction as described above, and can thus be coupled to one wiring substrate120. However, by drawing out the first individual lead electrode91and the second individual lead electrode94in the same direction, there is concern that the pressure chambers12cannot be densely disposed in the +X direction in order to secure a space for wiring, or the channel forming substrate10may become large in the +X direction.

The piezoelectric layer70and the fourth electrode80are the same as those of Embodiment 1 described above, and redundant description will be omitted. That is, the fourth electrode80serves as a common electrode for the plurality of active portions, that is, here, the plurality of first active portions311, the plurality of second active portions312, and the plurality of third active portions313.

A drive signal for driving the recording head2having such a piezoelectric actuator300will be described with reference toFIG.18.FIG.18illustrates drive waveforms representing a bias potential, a fourth drive signal204, and a fifth drive signal205.FIGS.19to21are sectional views taken along line C-C illustrating a state in which the piezoelectric actuator300and the vibration plate50are deformed by drive signals.

As illustrated inFIG.18, the drive signal generator216generates the fourth drive signal204and the fifth drive signal205as drive signals. The fourth drive signal204corresponds to a “first drive signal” of Embodiment 2 and is supplied to the first electrode61. The fifth drive signal205is supplied to the second electrode62and the third electrode63.

The fourth drive signal204and the fifth drive signal205are repeatedly generated by the drive signal generator216every unit cycle T defined by a clock signal oscillated from the oscillation circuit215. The unit cycle T is also referred to as an ejection cycle T or a recording cycle T, and corresponds to one pixel of an image or the like printed on a medium S. In the present embodiment, the unit cycle T is divided into two cycles such as a first period T1 and a second period T2.

The fourth drive signal204is a signal having a first ejection pulse DP1 for driving the first active portion311in the second period T2 of one recording cycle T, and is repeatedly generated every recording cycle T. The first ejection pulse DP1 is selectively supplied to the first active portion311corresponding to the pressure chamber12communicating with the nozzle21that ejects a liquid. That is, the control section generates an application pulse from the head control signal and the fourth drive signal204for each first active portion311corresponding to the nozzle21and supplies the application pulse to the piezoelectric actuator300. The application pulse generated from the fourth drive signal204is supplied to the first electrode61of the first active portion311. The bias potential vbs is supplied to the fourth electrode80that is a common electrode for the plurality of first active portions311. Therefore, a potential applied to the first electrode61by the application pulse has the bias potential vbs applied to the fourth electrode80as a reference potential. The bias potential vbs applied to the fourth electrode80corresponds to a “second potential” disclosed in the claims.

The first ejection pulse DP1 includes a third contraction element P20, a third contraction maintaining element P21, and a third return element P22. The application pulse generated from the fourth drive signal204always supplies a tenth potential V10that is an intermediate potential to the first electrode61when the ejection pulse DP is not supplied. Therefore, the unit cycle T of the fourth drive signal204includes a sixth reference element B6 and a seventh reference element B7 that supply the tenth potential V10before and after the first ejection pulse DP1. That is, in the fourth drive signal204, the sixth reference element B6, the first ejection pulse DP1, and the seventh reference element B7 are generated in this order within the unit cycle T. The sixth reference element B6 is generated in a period including the first period T1.

The sixth reference element B6 and the seventh reference element B7 continuously apply the tenth potential V10lower than the bias potential vbs to the first electrode61, and thus, as illustrated inFIG.19, a state in which the piezoelectric actuator300and the vibration plate50are flexurally deformed in the +Z direction on the pressure chamber12side is maintained. Consequently, the volume of the pressure chamber12is maintained as a tenth volume that is smaller than a reference volume.

The third contraction element P20 of the first ejection pulse DP1 applies the tenth potential V10to an eleventh potential V11to the first electrode61to deform the piezoelectric actuator300and the vibration plate50in the +Z direction as illustrated inFIG.21. Consequently, the volume of the pressure chamber12is reduced from the tenth volume to an eleventh volume.

The third contraction maintaining element P21 continues to apply the eleventh potential V11to the first electrode61, and maintains the volume of the pressure chamber12expanded by the third contraction element P20 as the eleventh volume for a certain period of time.

The third return element P22 applies the eleventh potential V11to the tenth potential V10to the first electrode61to deform the piezoelectric actuator300and the vibration plate50in the +Z direction. Consequently, the volume of the pressure chamber12is reduced from the eleventh volume and returned to the tenth volume.

The fifth drive signal205is a signal having a second ejection pulse DP2 for driving the second active portion312and the third active portion313in the first period T1 of one recording cycle T, and is repeatedly generated every recording cycle T. The second ejection pulse DP2 is selectively supplied to the second active portion312and the third active portion313corresponding to the pressure chamber12communicating with the nozzle21that ejects the liquid. That is, the control section generates an application pulse from the head control signal and the fifth drive signal205for each set of the second active portion312and the third active portion313corresponding to the nozzle21, and supplies the application pulse to the piezoelectric actuator300. The application pulse generated from the fifth drive signal205is supplied to the second electrode62and the third electrode63of the second active portion312and the third active portion313. In the present embodiment, the application pulse is simultaneously supplied to a set of the second electrode62and the third electrode63via the individual communication portion64A. The bias potential vbs is supplied to the fourth electrode80that is a common electrode for the plurality of second active portions312and the plurality of third active portions313. Therefore, a potential applied to the second electrode62and the third electrode63by the application pulse has the bias potential vbs applied to the fourth electrode80as a reference potential. The second ejection pulse DP2 is generated during the first period T1 during which the first ejection pulse DP1 of the fourth drive signal204is not generated. That is, the first ejection pulse DP1 and the second ejection pulse DP2 are not input at the same time.

The second ejection pulse DP2 includes a fourth expansion element P30, a fourth expansion maintaining element P31, and a fourth return element P32. The application pulse generated from the fifth drive signal205always supplies a twelfth potential V12that is an intermediate potential to the second electrode62and the third electrode63when the second ejection pulse DP2 is not supplied. Therefore, the unit cycle T of the fifth drive signal205includes an eighth reference element B8 and a ninth reference element B9 that supply a twelfth potential V12before and after the second ejection pulse DP2. That is, in the fifth drive signal205, the eighth reference element B8, the second ejection pulse DP2, and the ninth reference element B9 are generated in this order within the unit cycle T. The ninth reference element B9 is generated during a period including the second period T2 during which the first ejection pulse DP1 of the fourth drive signal204is generated.

The eighth reference element B8 and the ninth reference element B9 supply the twelfth potential V12that is the same as the bias potential vbs to the second electrode62and the third electrode63such that a state in which the second active portion312and the third active portion313are not driven is maintained. The ninth reference element B9 is supplied during the second period T2 during which the piezoelectric actuator300is driven by the first ejection pulse DP1. Therefore, driving of the first active portion311is not influenced since the second active portion312and the third active portion313are not driven while the first active portion311is being driven by the first ejection pulse DP1. Since the eighth reference element B8 and the ninth reference element B9 do not drive the second active portion312and the third active portion313, the volume of the pressure chamber12at the eighth reference element B8 and the ninth reference element B9 is determined by a state of the fourth drive signal204, that is, a drive state of the first active portion311.

The fourth expansion element P30 of the second ejection pulse DP2 applies the twelfth potential V12to a thirteenth potential V13to the second electrode62and the third electrode63to deform the piezoelectric actuator300and the vibration plate50in the −Z direction as illustrated inFIG.20. Consequently, the volume of the pressure chamber12is increased from the original volume to a twelfth volume. As described above, at the eighth reference element B8, as illustrated inFIG.19, the volume of the pressure chamber12is the tenth volume smaller than the reference volume that is the volume of the pressure chamber12when nothing is driven by supplying the tenth potential V10to the first electrode61of the first active portion311with the sixth reference element B6 of the fourth drive signal204. Therefore, the fourth expansion element P30 expands the pressure chamber12from the tenth volume that is smaller than the reference volume to the twelfth volume, and thus it is possible to achieve the expansion larger than the expansion from the reference volume to the twelfth volume. The thirteenth potential V13is preferably the same potential as the eleventh potential V11of the first ejection pulse DP1. The thirteenth potential V13is the maximum potential of the second ejection pulse DP2, and the eleventh potential V11is the maximum potential of the first ejection pulse DP1. Therefore, it is preferable to set the maximum potentials of the first ejection pulse DP1 and the second ejection pulse DP2 to be the same potential. By setting the maximum potentials of the first ejection pulse DP1 and the second ejection pulse DP2 to be the same potential, a circuit of the drive signal generator216can be simplified compared with a case of generating different potentials.

The fourth expansion maintaining element P31 continues to apply the thirteenth potential V13to the second electrode62and the third electrode63to maintain the volume of the pressure chamber12expanded by the fourth expansion element P30 as the twelfth volume for a certain period of time.

The fourth return element P32 applies the thirteenth potential V13to the twelfth potential V12to the second electrode62and the third electrode63to deform the piezoelectric actuator300and vibration plate50in the +Z direction. Consequently, the volume of the pressure chamber12is reduced from the twelfth volume to the tenth volume.

A timing at which the second ejection pulse DP2 ends is the same as a timing at which the first ejection pulse DP1 starts. That is, a timing at which the fourth return element P32 of the second ejection pulse DP2 ends is the same as a timing at which the third contraction element P20 of the first ejection pulse DP1 starts. When the first ejection pulse DP1 and the second ejection pulse DP2 are not supplied at the same time, the timing at which the fourth return element P32 of the second ejection pulse DP2 ends and the timing at which the third contraction element P20 of the first ejection pulse DP1 starts may be different. For example, it is preferable that an interval between the timing at which the fourth return element P32 of the second ejection pulse DP2 ends and the timing at which the third contraction element P20 of the first ejection pulse DP1 starts is ½ of the natural vibration cycle Tc of the pressure chamber12. Consequently, when the meniscus in the nozzle21is directed in the +Z direction due to the residual vibration caused by the first ejection pulse DP1, the second ejection pulse DP2 can be supplied, and it is possible to suppress movement of the ink meniscus generated by driving the first ejection pulse DP1 from being blocked due to driving of the second ejection pulse DP2 and thus to eject ink droplets.

By supplying the first ejection pulse DP1 and the second ejection pulse DP2 to the first electrode61, and the second electrode62and the third electrode63, respectively, ink droplets are ejected from the corresponding nozzle21.

Specifically, first, in a state in which the volume of the pressure chamber12is the tenth volume illustrated inFIG.19, the piezoelectric actuator300and the vibration plate50are moved in the −Z direction by the fourth expansion element P30 of the second ejection pulse DP2 as illustrated inFIG.20, and thus the volume of the pressure chamber12is increased from the tenth volume to the twelfth volume. Consequently, the meniscus of the ink in the nozzle21is drawn toward the pressure chamber12and ink is supplied to the pressure chamber12from the manifold100side.

Next, after the increased twelfth volume is maintained by the fourth expansion maintaining element P31 for a certain period of time, the piezoelectric actuator300and the vibration plate50are moved in the +Z direction by the fourth return element P32, and thus the volume of the pressure chamber12is reduced from the twelfth volume to the tenth volume.

Following the fourth return element P32, the piezoelectric actuator300and vibration plate50are further moved in the +Z direction as illustrated inFIG.21by the third contraction element P20 of the supplied first ejection pulse DP1, and thus the volume of the pressure chamber12is reduced from the tenth volume to the eleventh volume. In other words, by continuously supplying the fourth return element P32 of the second ejection pulse DP2 and the third contraction element P20 of the first ejection pulse DP1, the piezoelectric actuator300and the vibration plate50rapidly reduce the volume of the pressure chamber12from the twelfth volume to the eleventh volume. Consequently, the ink in the pressure chamber12is pressurized and ink droplets are ejected from the nozzle21.

After ejection of the ink droplets, the eleventh volume is maintained for a certain period of time by the third contraction maintaining element P21 of the first ejection pulse DP1. While the third contraction maintaining element P21 is being supplied, the ink pressure in the pressure chamber12, which has decreased due to the ejection of the ink droplets, is attenuated while repeating increase and decrease by the natural vibration of the pressure chamber12, and the volume of the pressure chamber12is increased and returned to the original tenth volume by the third return element P22.

As described above, by driving the first active portion311with the first ejection pulse DP1 and driving the second active portion312and the third active portion313with the second ejection pulse DP2 to eject ink droplets, an excluded volume when the twelfth volume is reduced to the eleventh volume can be increased. Therefore, ink droplets having a large ink weight can be ejected.

The ink droplets are ejected by the first ejection pulse DP1 for deforming the piezoelectric actuator300and the vibration plate50to protrude in a projection shape in the +Z direction on the pressure chamber12side, and the second ejection pulse DP2 for deforming the piezoelectric actuator300and the vibration plate50to protrude in a projection shape in the −Z direction on the opposite side to the pressure chamber12. Therefore, even when the piezoelectric actuator300is repeatedly driven, residual strain is less likely to occur in the piezoelectric layer70compared with a case where the piezoelectric actuator300is deformed in only one direction to eject ink droplets. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to curb a decrease in an amount of displacement.

Since a trapezoidal wave with a relatively simple shape can be used as the first ejection pulse DP1 and the second ejection pulse DP2, there is no need to generate a waveform with a complicated shape as the ejection pulse, a circuit configuration of the drive signal generator216can be simplified and control can be easily performed.

As described above, the recording head2that is an example of a piezoelectric device of the present disclosure includes the channel forming substrate10that is a substrate on which the pressure chambers12which are recesses communicating with the nozzles21for ejecting a liquid are arranged in the +X direction that is the first direction, the vibration plate50, and the piezoelectric actuator300. The piezoelectric actuator300has the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80in this order. The piezoelectric actuator300has the piezoelectric layers70between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, and between the third electrode63and the fourth electrode80. The plurality of first active portions311, the plurality of second active portions312and the plurality of third active portions313, which are active portions in which the piezoelectric layer70is interposed between the first electrode61, the second electrode62, and the third electrode63, and the fourth electrode80, are provided. The second electrode62and the third electrode63are provided at both ends of the pressure chamber12in the +X direction from the edge of the region facing the pressure chamber12to the outside of the pressure chamber12when viewed in the −Z direction that is a stacking direction. The first electrode61is formed between the second electrode62and the third electrode63in the +X direction, and the fourth electrode80configures a common electrode for the plurality of first active portions311, second active portions312, and third active portions313.

As described above, the first electrode61that drives the piezoelectric actuator300to be deformed toward the pressure chamber12side, and the second electrode62and the third electrode63that drive the piezoelectric actuator300to be deformed toward the opposite side to the pressure chamber12are provided. Therefore, compared with a case where the piezoelectric actuator300is deformed only in one direction along the Z axis, the residual strain in the piezoelectric layer70is less likely to occur even when the piezoelectric actuator300is repeatedly driven. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to curb a decrease in an amount of displacement. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to prevent deterioration in the ejection characteristics such as the ink weight of ink droplets ejected from the nozzles21and to continue high-quality printing. An amount of displacement can be improved compared with a case where the piezoelectric actuator300is driven only in one direction along the Z axis. Therefore, the weight of ink droplets ejected from the nozzles21can be increased.

In the recording head2of the present embodiment, it is preferable that the second electrode62and the third electrode63configure individual electrodes provided independently in each of the second active portion312and the third active portion313that are active portions. That is, the second electrode62serves as an individual electrode for each second active portion312with respect to the plurality of second active portions312, and the third electrode63serves as an individual electrode for each third active portion313with respect to the plurality of third active portions313. As described above, by using the second electrode62and the third electrode63as individual electrodes for the second active portion312and the third active portion313, respectively, the second active portion312and the third active portion313can be selectively driven for the plurality of pressure chambers12.

In the recording head2of the present embodiment, it is preferable that the second electrode62and the third electrode63provided for the pressure chamber12that is one recess are electrically coupled on the channel forming substrate10that is a substrate. By electrically coupling the second electrode62and the third electrode63provided for one pressure chamber12on the channel forming substrate10, it is not necessary to independently provide the second individual lead electrode94for each of the second electrode62and the third electrode63, and a space for routing the second individual lead electrodes94on the channel forming substrate10and a space for coupling to the wiring substrate120are not required. Therefore, the number of the second individual lead electrodes94can be reduced, and thus a size of the channel forming substrate10can be reduced.

The ink jet recording apparatus1that is an example of the liquid ejecting apparatus of the present embodiment includes the channel forming substrate10that is a substrate on which the pressure chambers12which are recesses communicating with the nozzles21for ejecting a liquid are arranged in the +X direction that is the first direction, the vibration plate50, the piezoelectric actuator300, and the control section that drives the piezoelectric actuator300. The piezoelectric actuator300has the first electrode61, the second electrode62, the third electrode63, and the fourth electrode80in this order. The piezoelectric actuator300has the piezoelectric layers70between the first electrode61and the fourth electrode80, between the second electrode62and the fourth electrode80, and between the third electrode63and the fourth electrode80. The plurality of first active portions311, the plurality of second active portions312and the plurality of third active portions313, which are active portions in which the piezoelectric layer70is interposed between the first electrode61, the second electrode62, and the third electrode63, and the fourth electrode80, are provided. The second electrode62and the third electrode63are provided at both ends of the pressure chamber12in the +X direction from the edge of the region facing the pressure chamber12to the outside of the pressure chamber12when viewed in the −Z direction that is a stacking direction. The first electrode61is formed between the second electrode62and the third electrode63in the +X direction, and the fourth electrode80configures a common electrode for the plurality of first active portions311, second active portions312, and third active portions313. The control section supplies the first ejection pulse DP1 to the first electrode61to drive the piezoelectric actuator300when the piezoelectric actuator300is deformed toward the pressure chamber12side. When the piezoelectric actuator300is deformed toward the opposite side to the pressure chamber12, the control section supplies the second ejection pulse DP2 to the second electrode62and the third electrode63to drive the piezoelectric actuator300. The control section causes the nozzle21to eject a liquid with the first ejection pulse DP1 and the second ejection pulse DP2.

The control section drives the piezoelectric actuator300with the first ejection pulse DP1 and the second ejection pulse DP2, and thus the residual strain is less likely to occur in the piezoelectric layer70even when the piezoelectric actuator300is repeatedly driven compared with a case where the piezoelectric actuator300is deformed in only one direction along the Z axis. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to curb a decrease in an amount of displacement. Therefore, even when the piezoelectric actuator300is repeatedly driven, it is possible to prevent deterioration in the ejection characteristics such as the ink weight of ink droplets ejected from the nozzles21and to continue high-quality printing. An amount of displacement can be improved compared with a case where the piezoelectric actuator300is driven only in one direction along the Z axis. Therefore, the weight of ink droplets ejected from the nozzles21can be increased.

In the ink jet recording apparatus1of the present embodiment, it is preferable that the control section does not supply the first ejection pulse DP1 and the second ejection pulse DP2 at the same time. Consequently, it is possible to curb the piezoelectric actuator300from being deformed excessively and thus to curb damage such as cracks from occurring in the piezoelectric actuator300.

In the ink jet recording apparatus1of the present embodiment, it is preferable that the first ejection pulse DP1 and the second ejection pulse DP2 have the same maximum potential. That is, the thirteenth potential V13that is the maximum potential of the second ejection pulse DP2 and the eleventh potential V11that is the maximum potential of the first ejection pulse DP1 are set to the same potential, and thus a circuit of the drive signal generator216can be simplified compared with a case of generating different potentials.

In the above-described example, the second electrode62and the third electrode63provided to correspond to one pressure chamber12are electrically coupled on the channel forming substrate10, but the present disclosure is not particularly limited to this.FIG.22illustrates a modification example of the recording head2of the present embodiment.FIG.22is a plan view in which the channel forming substrate10illustrating a modification example of the recording head2according to Embodiment 2 is viewed in the +Z direction.

As illustrated inFIG.22, the second electrode62and the third electrode63provided to correspond to one pressure chamber12are separated from each other on the channel forming substrate10so as not to be electrically coupled. The second individual lead electrodes94is provided independently for each of the second electrode62and the third electrode63.

As described above, by not electrically coupling the second electrode62and the third electrode63for one pressure chamber12on the channel forming substrate10, different waveforms, that is, different potentials can be supplied to the second electrode62and the third electrode63. For example, by varying the thirteenth potential V13of the second ejection pulse DP2 supplied to each of the second electrode62and the third electrode63, a flight direction of the ink droplets ejected from the nozzle21is bent in a direction along the X axis. Therefore, when the ink droplets do not fly in the +Z direction perpendicular to the liquid ejecting surface20a, the thirteenth potential V13of the second ejection pulse DP2 to be supplied to each of the second electrode62and the third electrode63may be adjusted such that the ink droplets fly in the +Z direction. In other words, by adjusting the thirteenth potential V13supplied to each of the second electrode62and the third electrode63, the flight direction of the ink droplets can be adjusted, and it is possible to curb deviation in a landing position of the ink droplets on the medium S and thus to improve printing quality.

That is, in the recording head2illustrated inFIG.22, it is preferable that the second electrode62and the third electrode63are not electrically coupled on the channel forming substrate10that is a substrate. According to this, the second electrode62and the third electrode63can be driven by being supplied with different potentials. Therefore, the second electrode62and the third electrode63are driven by being supplied with different potentials, and thus an angle of ejection direction of the ink droplets, that is, a tilt angle in the +X direction with respect to the +Z direction can be adjusted.

Here, a modification example of the fifth drive signal205of the present embodiment will be described with reference toFIG.23.FIG.23illustrates drive waveforms representing modification examples of the bias potential vbs, the fourth drive signal204, and the fifth drive signal205.

As illustrated inFIG.23, the fifth drive signal205has an eighth reference element B8, a second ejection pulse DP2, and a ninth reference element B9.

The eighth reference element B8 and the ninth reference element B9 supply a potential supplied to the fourth electrode80to the second electrode62and the third electrode63, that is, in the present embodiment, a fourteenth potential V14different from the bias potential vbs. Here, the fourteenth potential V14corresponds to a “first potential” in Embodiment 2. The fourteenth potential V14is a potential lower than the bias potential vbs in the present embodiment. That is, the fourteenth potential V14<the bias potential vbs. The fourteenth potential V14is preferably the same potential as the tenth potential V10of the sixth reference element B6 and the seventh reference element B7 of the first ejection pulse DP1. By setting the fourteenth potential V14and the tenth potential V10to the same potential, a circuit of the drive signal generator216can be simplified compared with a case of generating different potentials.

The fourth expansion element P30 of the second ejection pulse DP2 applies the fourteenth potential V14to the thirteenth potential V13to the second electrode62and the third electrode63. The fourth return element P32 applies the thirteenth potential V13to the fourteenth potential V14to the second electrode62and the third electrode63. The thirteenth potential V13is preferably the same potential as the tenth potential V10of the first ejection pulse DP1. Consequently, the first ejection pulse DP1 and the second ejection pulse DP2 are allowed to have the same waveform shape. Here, the fact that the first ejection pulse DP1 and the second ejection pulse DP2 have the same waveform shape means that the first ejection pulse DP1 and the second ejection pulse DP2 have the same lowest potential, highest potential, and slope. By setting the first ejection pulse DP1 and the second ejection pulse DP2 to have the same waveform shape as described above, the drive signal generator216can be easily controlled.

By maintaining a state in which the fourteenth potential V14is supplied to the second electrode62and the third electrode63by the eighth reference element B8 and the ninth reference element B9, the natural vibration cycle Tc of the pressure chamber12can be adjusted. Here, the magnitude of the fourteenth potential V14supplied to the second electrode62and the third electrode63and the magnitude of the natural vibration cycle Tc of the pressure chamber12have an inversely proportional relationship. Therefore, by supplying the fourteenth potential V14to the second electrode62and the third electrode63, the natural vibration cycle Tc of the pressure chamber12can be reduced, and ink droplets can be continuously ejected at a high speed.

In a head unit in which a plurality of recording heads2are unitized, even when there is a variation in the natural vibration cycle Tc among the plurality of recording heads2, it is possible to reduce the variation the natural vibration cycle Tc among the plurality of recording heads2by changing the fourteenth potential V14of each recording head2. Therefore, it is possible to curb variations in ejection characteristics such as ink weight and ejection speed of ink droplets ejected from a plurality of recording heads2.

As illustrated inFIG.23, in the ink jet recording apparatus1, it is preferable that the control section supplies the fourth drive signal204that is a first drive signal including the first ejection pulse DP1 to the first electrode61, and the control section supplies the fourteenth potential V14that is a first potential different from a potential supplied to the fourth electrode80to the second electrode62and the third electrode63while the fourth drive signal204is being supplied to the first electrode61. According to this, while the fourth drive signal204is being supplied to the first electrode61, by maintaining the state in which the fourteenth potential V14is supplied to the second electrode62and the third electrode63, natural vibration cycle Tc of the pressure chamber12can be adjusted. Therefore, it is possible to reduce the natural vibration cycle Tc of the pressure chamber12and continuously eject ink droplets at a high speed. In a head unit in which a plurality of recording heads2are unitized or in the ink jet recording apparatus1having a plurality of recording heads2, even when there is a variation in the natural vibration cycle Tc among the plurality of recording heads2, by changing the fourteenth potential V14for each recording head2, the variation in the natural vibration cycle Tc among the plurality of recording heads2can be reduced. Therefore, it is possible to curb variations in ejection characteristics such as ink weight and ejection speed of ink droplets ejected from a plurality of recording heads2. In the example described above, the bias potential vbs is supplied to the fourth electrode80, but the present disclosure is not particularly limited to this, and the fourth electrode80may be ground (GND).

In the ink jet recording apparatus1of the present embodiment, it is preferable that the control section supplies the bias potential vbs that is a second potential to the fourth electrode80while supplying the fourth drive signal204that is a first drive signal, and the fourteenth potential V14that is a first potential is equal to or higher than the bias potential vbs. By setting the fourteenth potential V14to a potential higher than the bias potential vbs as described above, it is possible to suppress the application of an electric field reverse to the ejection pulse DP to the piezoelectric actuator300. Therefore, it is possible to curb the piezoelectric actuator300from being cracked or destroyed.

As illustrated inFIG.23, in the ink jet recording apparatus1, it is preferable that the first ejection pulse DP1 and the second ejection pulse DP2 have the same waveform shape. According to this, the control of the drive signal generator216can be simplified.

In addition to the second ejection pulse DP2, the fifth drive signal205may have the damping pulse SVP of Embodiment 1 described above.FIG.24illustrates a modification example of such fifth drive signal205.FIG.24illustrates drive waveforms of the bias potential vbs, the fourth drive signal204and the fifth drive signal205.

As illustrated inFIG.24, the unit cycle T of the fourth drive signal204and the fifth drive signal205is separated into three periods such as a first period T1, a second period T2 and a third period T3.

The first ejection pulse DP1 of the fourth drive signal204is generated during the second period T2. The second ejection pulse DP2 of the fifth drive signal205is generated during the first period T1.

The damping pulse SVP is generated during the third period T3 of the fifth drive signal205. The fifth drive signal205has the eighth reference element B8, the second ejection pulse DP2, the ninth reference element B9, the damping pulse SVP, and the tenth reference element B10 in this order. The tenth reference element B10 supplies the second electrode62and the third electrode63with the same twelfth potential V12as the eighth reference element B8 and the ninth reference element B9. The twelfth potential V12is the same potential as the bias potential vbs as described above.

The damping pulse SVP includes a fifth expansion element P40, a fifth expansion maintaining element P41, and a fifth return element P42.

The fifth expansion element P40 supplies the twelfth potential V12to the fifteenth potential V15to the second electrode62and the third electrode63to deform the piezoelectric actuator300and the vibration plate50in the −Z direction on the opposite side to the pressure chamber12. Consequently, the volume of the pressure chamber12is increased from the tenth volume to the thirteenth volume.

The fifteenth potential V15of the fifth expansion element P40 is preferably the same potential as the thirteenth potential V13of the second ejection pulse DP2. By setting the fifteenth potential V15and the thirteenth potential V13to the same potential, a circuit of the drive signal generator216can be simplified compared with a case of generating different potentials.

The fifth expansion maintaining element P41 continues to apply the fifteenth potential V15to the second electrode62and the third electrode63to maintain the volume of the pressure chamber12expanded by the fifth expansion element P40 as the thirteenth volume for a certain period of time.

The fifth return element P42 applies the fifteenth potential V15to the twelfth potential V12to the second electrode62and the third electrode63to deform the piezoelectric actuator300and vibration plate50in the +Z direction. Consequently, the volume of the pressure chamber12is reduced from the thirteenth volume and returned to the tenth volume.

By inserting the damping pulse SVP after the second ejection pulse DP2 and the first ejection pulse DP1 as described above, the residual vibration of the ink in the pressure chamber12after the ink is ejected from the nozzle21can be converged in a short time. That is, when the second active portion312and the third active portion313of the piezoelectric actuator300are driven by the damping pulse SVP, the second active portion312and the third active portion313are contracted along the Z axis as inFIG.20, and the piezoelectric actuator300and the vibration plate50are deformed to protrude in a projection shape in the −Z direction on the opposite side to the pressure chamber12. In this case, a tensile stress is applied to the portion including the first active portion311interposed between the second active portion312and the third active portion313, and thus the apparent Young's modulus increases. By increasing the apparent Young's modulus of the piezoelectric actuator300, the residual vibration of the ink in the pressure chamber12after ink droplets are ejected can be converged in a short time.

Of course, for the fifth drive signal205having the damping pulse SVP, as inFIG.23, by setting the potential supplied to the second electrode62and the third electrode63by the eighth reference element B8, the ninth reference element B9, and the tenth reference element B10 to a potential different from the bias potential vbs, the natural vibration cycle Tc of the pressure chamber12can be adjusted.

As illustrated inFIG.24, in the ink jet recording apparatus1, it is preferable that the control section supplies the second electrode62and the third electrode63with the damping pulse SVP for driving the piezoelectric actuator such that a liquid is not ejected from the nozzle21after supplying the first ejection pulse DP1 and the second ejection pulse DP2. According to this, by inserting the damping pulse SVP after the ejection pulse DP, the apparent Young's modulus of the piezoelectric layer70can be increased, and thus the residual vibration after the first ejection pulse DP1 and the second ejection pulse DP2 can be converged in a short time. Therefore, ejection of ink droplets can be repeated in a short time, and high-speed continuous ejection can be realized.

The damping pulse SVP may be supplied to the second electrode62and the third electrode63corresponding to the pressure chamber12that does not eject ink droplets. Consequently, the ink in the vicinity of the pressure chamber12and the nozzle21is slightly vibrated to curb sedimentation of components contained in the ink or to curb accumulation of thickened ink, and thus to curb ejection failure of ink droplets due to the thickened ink.

The driving of the recording head2using the drive signals illustrated inFIGS.18,23, and24of the present embodiment is applicable to the configuration of the above Embodiment 1, that is, the configuration in which the second electrode62configures a common electrode for the plurality of second active portions312and the third electrode63configures a common electrode for the plurality of third active portions313. That is, the control section may supply the fourth drive signal204to the first electrode61that configures an individual electrode, and supply the fifth drive signal205to the second electrode62and the third electrode63that configure common electrodes. The second ejection pulse DP2 is also supplied to the second active portion312and the third active portion313corresponding to the nozzles21that do not eject ink droplets. However, ink droplets can be selectively ejected from the nozzles21by not ejecting the ink droplets only with the second ejection pulse DP2, in other words, by ejecting the ink droplets only when combined with the first ejection pulse DP1. By supplying only the second ejection pulse DP2, the second ejection pulse DP2 also functions as a micro-vibration pulse. Thus, the ink in the vicinity of the nozzle21can be slightly vibrated by driving the second active portion312and the third active portion313corresponding to the nozzles21that do not eject ink droplets with the second ejection pulse DP2. Therefore, it is possible to curb sedimentation of components contained in the ink in the vicinity of the pressure chamber12and the nozzle21or to curb accumulation of thickened ink, and thus to curb ejection failure of ink droplets due to the thickened ink. Of course, the second ejection pulse DP2 may also be supplied as a micro-vibration pulse to the second active portion312and the third active portion313that configure individual electrodes of the present embodiment.

OTHER EMBODIMENTS

Although each embodiment of the present disclosure has been described above, a basic configuration of the present disclosure is not limited to the above description.

Here, the piezoelectric actuator300and vibration plate50are not limited to those described above. Modification examples of the piezoelectric actuator300and vibration plate50are illustrated inFIGS.25to30.FIGS.25to29are sectional views of main portions of the recording head2according to other embodiments of the present disclosure.FIG.30is a plan view in which the channel forming substrate10according to another embodiment of the present disclosure is viewed in the +Z direction. The same reference numeral is given to a member similar to that of each of the above embodiments, and the redundant description will be omitted.

As illustrated inFIG.25, on the surface of the fourth electrode80in the −Z direction on the opposite side to the piezoelectric layer70, recessed grooves81are formed between the first electrode61and the second electrode62and between the first electrode61and the third electrode63in the +X direction. For example, a recess71may be formed on the surface of the piezoelectric layer70in the −Z direction by forming the piezoelectric layer70on the first electrode61, the second electrode62, and the third electrode63according to a liquid phase deposition method such as a sol-gel method or a MOD method, and the groove81may be formed by forming a film of the fourth electrode80on the surface of the piezoelectric layer70in the −Z direction on which the recess71is formed. Of course, the groove81may be formed also in Embodiments 1 and 2 described above. The surface of the piezoelectric layer70in the −Z direction may be planarized through chemical mechanical polishing (CMP) such that the groove81is not formed in the fourth electrode80. When the surface of the piezoelectric layer70in the −Z direction is flat, the surface of the piezoelectric layer70in the −Z direction may be partially etched via a mask to simultaneously form the recess71and the groove81.

In the recording head2illustrated inFIG.25, on the surface of the fourth electrode80on the opposite side to the piezoelectric layer70, it is preferable that the recessed grooves81are formed between the first electrode61and the second electrode62, and between the first electrode61and the third electrode63in the +X direction that is a first direction because deformation is facilitated.

The vibration plate50preferably has a Young's modulus lower than that of the piezoelectric layer70. For example, in each of the above-described embodiments, the insulator film52of zirconium oxide (ZrOX) is included, and lead zirconate titanate (PZT) is used for the piezoelectric layer70, and thus the vibration plate50has a Young's modulus lower than that of the piezoelectric layer70. Therefore, as illustrated inFIG.26, both ends of the vibration plate50in the +X direction are thinner than the center thereof in the +Z direction in the region corresponding to the pressure chamber12when viewed in the +Z direction. That is, when viewed in the −Z direction, the vibration plate50includes a first vibration portion50ahaving a thickness d1 provided in a region overlapping the first electrode61, and a second vibration portion50bhaving a thickness d2 provided in a region overlapping the second electrode62and the third electrode63, where d1>d2.

The first vibration portion50aand the second vibration portion50bare formed such that the surfaces thereof in the +Z direction are planarized, and the first vibration portion50afurther protrudes in the −Z direction on the opposite side to the pressure chamber12than the second vibration portion50bto have a larger film thickness. Therefore, in the +Z direction, a distance t1 between the first electrode61and the fourth electrode80is smaller than a distance t2 between the second electrode62and the third electrode63, and the fourth electrode80. That is, t1<t2. Each of the distance t1 between the first electrode61and the fourth electrode80and the distance t2 between the second electrode62and the third electrode63and the fourth electrode80may be replaced with a thickness of the piezoelectric layer70in the −Z direction.

In the first vibration portion50aand the second vibration portion50bof the vibration plate50inFIG.26, the overall thicknesses d1 and d2 of the vibration plate50may be adjusted by changing the thickness of the elastic film51, for example.

As illustrated inFIG.26, the second electrode62, the third electrode63, the first electrode61, and the fourth electrode80are disposed in the −Z direction that is a stacking direction. It is preferable that the distance t1 between the first electrode61and the fourth electrode80in the −Z direction is smaller than the distance t2 between the second electrode62and the third electrode63, and the fourth electrode80. As described above, by making the distance t1 between the first electrode61and the fourth electrode80smaller than the distance t2, the electric field intensity of the first active portion311can be increased. An electric field is applied to the piezoelectric layer70in a direction inclined with respect to the +Z direction between the first electrode61and the fourth electrode80in an XZ plane defined by the X axis and the Z axis. Therefore, the driving efficiency can be improved.

As illustrated inFIG.27, the first vibration portion50aand the second vibration portion50bmay be formed such that the surfaces thereof in the −Z direction are planarized, and the first vibration portion50afurther protrudes in the +Z direction on the pressure chamber12side than the second vibration portion50bto have a larger film thickness. In the first vibration portion50aand the second vibration portion50bof the vibration plate50inFIG.27, the overall thicknesses d1 and d2 of the vibration plate50may be adjusted by changing the thickness of the elastic film51, for example.

That is, as illustrated inFIGS.26and27, it is preferable that the vibration plate50has a Young's modulus larger than that of the piezoelectric layer70, and the second vibration portion50bcorresponding to both ends in the +X direction that is a first direction is thinner than the first vibration portion50acorresponding to the center in the region facing the pressure chamber12that is a recess in the +Z direction, when viewed in the +Z direction that is a stacking direction. By providing the second vibration portion50bthinner than the first vibration portion50aat both ends of the vibration plate50in the +X direction as described above, the vibration plate50is easily deformed along the Z axis, and it is possible to improve the so-called displacement efficiency in which a large displacement amount can be obtained with a relatively low voltage.

By making the thickness d1 of the first vibration portion50aof the vibration plate50larger than the thickness d2 of the second vibration portion50b, the first active portion311can be separated from a position of the neutral axis of the vibration plate50. Therefore, the displacement efficiency of the first active portion311can be improved.

As illustrated inFIG.28, the thickness d2 of the second vibration portion50bof the vibration plate50may be larger than the thickness d1 of the first vibration portion50a, that is, d1<d2. Even with such a configuration, the same effect as inFIG.27can be achieved.

As illustrated inFIG.26, it is preferable that both ends of the piezoelectric layer70in the +X direction that is a first direction is thicker than the center thereof in the region facing the pressure chamber12that is a recess in the −Z direction, when viewed in the −Z direction that is a stacking direction. That is, the thickness t2 of both ends of the piezoelectric layer70is preferably larger than the thickness t1 of the center. As described above, the thickness t1 of the piezoelectric layer70between the first electrode61and the fourth electrode80is smaller than the thickness t2 of the piezoelectric layer70between the second electrode62and the third electrode63, and the fourth electrode80, and thus the electric field intensity of the first active portion311can be increased. An electric field is applied to the piezoelectric layer70in a direction inclined with respect to the +Z direction between the first electrode61and the fourth electrode80in an XZ plane defined by the X axis and the Z axis. Therefore, the driving efficiency can be improved.

As illustrated inFIG.28, the thickness d1 of the first vibration portion50aof the vibration plate50may be smaller than the thickness d2 of the second vibration portion50b. That is, d1<d2. As described above, by setting the thickness d1 of the first vibration portion50ato be smaller than the thickness of the second vibration portion50b, the driving efficiency of the first active portion311can be improved. By setting the thickness d2 of the second vibration portion50bthat is a region where the vibration plate50bends most to be larger than the thickness d1 of the first vibration portion50a, it is possible to curb destruction of the second vibration portion50bwhen the piezoelectric actuator300is driven.

As illustrated inFIG.29, the piezoelectric layer70of the piezoelectric actuator300includes a first piezoelectric layer70a, a second piezoelectric layer70b, and a third piezoelectric layer70cin the −Z direction from the vibration plate50. The first electrode61is provided between the second piezoelectric layer70band the third piezoelectric layer70c. The second electrode62and the third electrode63are provided between the first piezoelectric layer70aand the second piezoelectric layer70b. That is, the second electrode62and the third electrode63, the first electrode61, and the fourth electrode80are disposed in the −Z direction. That is, the first electrode61, and the second electrode62and the third electrode63are disposed at different positions in the −Z direction. A distance t3 between the first electrode61and the fourth electrode80is smaller than a distance t4 between the second electrode62and the third electrode63and the fourth electrode80. That is, t3<t4. The first piezoelectric layer70aand the second piezoelectric layer70bof the piezoelectric layers70are provided on the pressure chamber12side of the first electrode61.

The first electrode61, and the second electrode62and the third electrode63are disposed at positions that do not overlap each other when viewed in the −Z direction. In the example illustrated inFIG.29, the first electrode61, and the second electrode62and the third electrode63are disposed at different positions in the −Z direction. Therefore, the first electrode61, and the second electrode62and the third electrode63may be disposed at positions partially overlapping each other in the −Z direction.

In the configuration illustrated inFIG.29, the second electrode62and the third electrode63, the first electrode61, and the fourth electrode80are disposed in the −Z direction that is a stacking direction. It is preferable that the distance d3 between the first electrode61and the fourth electrode80in the −Z direction is smaller than the distance d4 between the second electrode62and the third electrode63, and the fourth electrode80. As described above, by making the distance d3 between the first electrode61and the fourth electrode80smaller than the distance d4, the electric field intensity of the first active portion311can be increased. An electric field is applied to the piezoelectric layer70in a direction inclined with respect to the +Z direction between the first electrode61and the fourth electrode80in an XZ plane defined by the X axis and the Z axis. Therefore, the driving efficiency can be improved.

In the configuration illustrated inFIG.29, it is preferable that the piezoelectric layer70has the first piezoelectric layer70aand the second piezoelectric layer70bon the pressure chamber12side that is a recess of the first electrode61. As described above, since the first piezoelectric layer70aand the second piezoelectric layer70bare provided on the pressure chamber12side of the first electrode61, the distance t3 between the first electrode61and the fourth electrode80can be made smaller than the distance t4, and the electric field intensity of the first active portion311can be increased. An electric field can be applied to the piezoelectric layer70in a direction inclined with respect to the +Z direction between the first electrode61and the fourth electrode80in the XZ plane defined by the X axis and the Z axis. Therefore, driving efficiency can be improved. An electric field in a direction inclined with respect to the +Z direction can be applied to the second piezoelectric layer70bto be driven between the first electrode61, and the second electrode62and the third electrode63in the XZ plane. Therefore, the driving efficiency can be improved.

As illustrated inFIG.30, the first electrode61has a first central portion61aat the center and first end portions61bat both ends in a direction along the Y axis at positions overlapping the pressure chamber12when viewed in the −Z direction. A width w1 of the first central portion61ain the +X direction is larger than a width w2 of the first end portion61b. That is, w1>w2. That is, the width of the first electrode61in the +X direction is larger at the center side of the pressure chamber12in the +Y direction than at both ends thereof when viewed in the −Z direction.

The second electrode62has a second central portion62aat the center and second end portions62bat both ends in the direction along the Y axis at positions overlapping the pressure chamber12when viewed in the −Z direction. A width w3 of the second central portion62ain the +X direction is larger than a width w4 of the second end portion62b. That is, w3>w4.

The third electrode63has a third central portion63aat the center and third end portions63bat both ends in the direction along the Y axis at positions overlapping the pressure chamber12when viewed in the −Z direction. A width w5 of the third central portion63ain the +X direction is larger than a width w6 of the third end portion63b. That is, w5>w6. That is, the width of the second electrode62and the third electrode63in the +X direction is larger at the center side of the pressure chamber12in the +Y direction than at both ends when viewed in the −Z direction.

In the example illustrated inFIG.30, the width in the +X direction of both the first electrode61, and the second electrode62and the third electrode63is larger at the center side of the pressure chamber12in the +Y direction than both ends thereof when viewed in the −Z direction. However, the present disclosure is not particularly limited to this, and any one of the first electrode61, and the second electrode62and the third electrode63may have a width in the +X direction that satisfies the above configuration.

As illustrated inFIG.30, it is preferable that the width of the first electrode61in the +X direction that is a first direction is larger than at the center side of the pressure chamber12that is a recess in the +Y direction that is a second direction orthogonal to the +X direction than at both ends thereof when viewed in the −Z direction that is a stacking direction. By making the width w1 of the first central portion61aat the center of the first electrode61larger than the width w2 of the first end portions61bat both ends as described above, an area of the first electrode61in the XY plane can be increased, and the driving efficiency can be improved. Since the first end portion61bhas the smaller width w2 than the first central portion61a, electric field concentration at the end of the first active portion311can be curbed. Therefore, it is possible to curb destruction such as burning and cracking of the piezoelectric layer70.

As illustrated inFIG.30, it is preferable that the width of the second electrode62and the third electrode63in the +X direction that is a first direction is larger than at the center side of the pressure chamber12that is a recess in the +Y direction that is a second direction orthogonal to the +X direction than at both ends thereof when viewed in the −Z direction that is a stacking direction. As described above, the width w3 of the second central portion62aand the width w5 of the third central portion63aat the centers of the second electrode62and the third electrode63are respectively larger than the width w4 of the second end portion62bat both ends and the width w6 of the third end portion63bat both ends. Thus, an area of the XY plane of the second electrode62and the third electrode63can be increased, and the driving efficiency can be improved.

In the ink jet recording apparatus1described above, a case where the recording head2is mounted on the transport body7and moved in the direction along the Y axis has been exemplified, but the present disclosure is not particularly limited to this and can also be applied to a so-called line-type recording apparatus in which the recording head2is fixed and printing is performed simply by moving the medium S such as paper in the direction along the X axis that is a sub-scanning direction.

In each of the above embodiments, the bias potential vbs is supplied to the fourth electrode80, but the present disclosure is not particularly limited to this, and the fourth electrode80may be ground (GND).

In the above embodiments, the ink jet recording head has been described as an example of a liquid ejecting head, and the ink jet recording apparatus has been described as an example of a liquid ejecting apparatus. The present disclosure is intended for being applied to general liquid ejecting heads and liquid ejecting apparatuses, and can of course be applied to liquid ejecting heads and liquid ejecting apparatuses that eject liquids other than ink. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, coloring material ejecting heads used in manufacturing color filters such as liquid crystal displays, electrode material ejecting heads used for electrode formation such as organic EL displays and field emission displays (FEDs), and bioorganic material ejecting heads used for bio-chip manufacturing, and the present disclosure can also be applied to liquid ejecting apparatuses having such liquid ejecting heads.