Liquid discharge head

A liquid discharge head includes: a first substrate having pressure chambers, the first substrate having a first surface in which nozzles communicating with the pressure chambers are open and a second surface in which first holes and second holes communicating with the pressure chambers are open; a piezoelectric actuator arranged on the second surface of the first substrate and configured to apply discharge energy to liquid inside the pressure chambers; a second substrate joined to the second surface of the first substrate and having first channels and second channels, the first channels communicating with the pressure chambers via the first holes, the second channels communicating with the pressure chambers via the second holes; first ring-shaped traces connected to the piezoelectric actuator and each surrounding one of the first holes; and second ring-shaped traces connected to the piezoelectric actuator and each surrounding one of the second holes.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2019-141967, filed on Aug. 1, 2019, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

Field of the Invention

The present disclosure relates to a liquid discharge head which discharges liquid from a nozzle.

Description of the Related Art

There is a known ink-jet recording head (see Japanese Patent Application Laid-open No. 2018-158552) as a liquid discharge head which is provided with a nozzle, a pressure chamber communicating with the nozzle, an ink supply channel connected to one end of the pressure chamber, and an ink exhaust channel connected to the other end of the pressure chamber. In the ink-jet recording head, the ink is circulated via the ink supply channel, the pressure chamber, and the ink exhaust channel. With this, it is possible to prevent any sedimentation of an ink component inside an ink channel and any drying of the ink in the vicinity of the nozzle. Further, it is also possible to exhaust an air bubble entering into and mixed with the ink inside the ink channel.

SUMMARY

In the above-described ink-jet recording head, the ink supply channel and the ink exhaust channel are formed in a substrate which is different from another substrate in which the pressure chamber is formed. Further, the substrate in which the ink supply channel and the ink exhaust channel are formed is joined to the upper surface of the another substrate in which the pressure chamber is formed, thereby allowing the ink supply channel and the ink exhaust channel to communicate with the pressure chamber. Here, a piezoelectric element applying discharge energy to the ink inside the pressure chamber is arranged on the upper surface of the another substrate in which the pressure chamber is formed such that the piezoelectric element faces the pressure chamber. Accordingly, in such a case that any unsatisfactory joining (joining failure) is occurred between the substrate in which the ink supply channel and the ink exhaust channel are formed and the another substrate in which the pressure chamber is formed, there is such a possibility that the ink might flow out from a connection part at which the ink supply channel and the pressure chamber are connected to each other and/or a connection part at which the ink exhaust channel and the pressure chamber are connected to each other, and that the ink might reach the piezoelectric element.

An object of the present disclosure is to provide a liquid discharge head in which it is possible to reduce such a possibility that the outflowed ink might reach the piezoelectric element, even in a case that the ink flows out from the connection part at which the ink supply channel and the pressure chamber are connected to each other and/or the connection part at which the ink discharge channel and the pressure chamber are connected to each other.

According to an aspect of the present disclosure, there is provided a liquid discharge head including: a first substrate having a plurality of pressure chambers formed therein, the first substrate having: a first surface in which a plurality of nozzles communicating with the pressure chambers respectively are open; and a second surface which is on a side opposite to the first surface and in which a plurality of first holes communicating with the pressure chambers respectively and a plurality of second holes communicating with the pressure chambers respectively are open; a piezoelectric actuator which is arranged on the second surface of the first substrate, and which is configured to apply discharge energy to liquid inside the pressure chambers; a second substrate which is joined to the second surface of the first substrate, and in which a plurality of first channels and a plurality of second channels are formed, the first channels communicating with the pressure chambers via the first holes respectively, the second channels communicating with the pressure chambers via the second holes respectively; a plurality of first ring-shaped traces which are connected to the piezoelectric actuator, and each of which surrounds one of the first holes on the second surface of the first substrate; and a plurality of second ring-shaped traces which are connected to the piezoelectric actuator, and each of which surrounds one of the second holes on the second surface of the first substrate.

In the liquid discharge head according to the aspect of the present disclosure, each of the pressure chambers communicates with one of the first channels and one of the second channels which correspond thereto and which are formed in the second substrate, via one of the first holes and one of the second holes formed in the second surface of the first substrate. Each of the first holes is surrounded by one of the first ring-shaped traces, and each of the second holes is surrounded by one of the second ring-shaped traces. Accordingly, even in such a case that the liquid flows out from the connection part at which each of the pressure chambers and one of the first channels are connected to each other and/or the connection part at which each of the pressure chambers and one of the second channels are connected to each other, such outflowed liquid can be interrupted by the first ring-shaped trace and/or the second ring-shaped trace. As a result, it is possible to reduce such a possibility that the liquid, outflowed from the connection parts might reach the piezoelectric actuator.

DESCRIPTION OF THE EMBODIMENTS

The overall configuration of a printer100, provided with a head1according to an embodiment of the present disclosure, will be explained with reference toFIG. 1.

The printer100is provided with a head unit1xincluding four heads1(each of which is an example of a liquid discharge head), a platen3, a conveying mechanism4and a controller5.

A sheet (paper)9is placed on the upper surface of the platen3.

The conveying mechanism4is provided with two roller pairs4aand4b. In a case that a conveyance motor4mis driven by control of the controller5, the roller pairs4aand4brotate in a state that the sheet9is sandwiched or pinched therebetween, thereby conveying the sheet9in a conveyance direction (an example of a first direction). The two roller pairs4aand4bare arranged so as to sandwich the platen3therebetween in the conveyance direction.

The head unit1xis elongated in a sheet width direction (an example of a second direction), and the head unit1xis of a line system wherein ink is discharged with respect to the sheet9from nozzles11n(seeFIGS. 2 and 4) in a state that the head unit1xis fixed to the printer100. The four heads1are arranged in a staggered manner in the sheet width direction.

Here, in the present embodiment, the sheet width direction is orthogonal to the conveyance direction. The sheet width direction and the conveyance direction are both orthogonal to the vertical direction.

The controller5has a Read Only Memory (ROM), a Random Access Memory (RAM) and an Application Specific Integrated Circuit (ASIC). The ASIC performs a recording processing, etc., in accordance with a program stored in the ROM. In the recording processing, the controller5controls a driver IC19(seeFIG. 4) of each of the heads1and the conveyance motor4m, based on a recording instruction (including image data) inputted from an external apparatus such as a PC, and performs recording of an image, etc., on the sheet9. Specifically, the controller5alternately executes a discharging processing of causing ink droplets from the nozzles11nand a conveying processing of conveying, by the roller pairs4aand4b, the sheet9in the conveyance direction at a predetermined conveyance amount.

Next, the configuration of each of the heads1will be explained, with reference toFIGS. 2 to 6.

As depicted inFIGS. 2 and 4, the head1has a channel substrate11, a piezoelectric actuator12and a COF18(an example of a wiring member).

As depicted inFIG. 4, the channel substrate11has a reservoir member11a, a pressure chamber plate11band a nozzle plate11c. Note that inFIG. 2, the illustration of the reservoir member11ais omitted.

The pressure chamber plate11bis formed with a plurality of pressure chambers11m. The nozzle plate11cis formed with a plurality of nozzles11ncommunicating with the plurality of pressure chambers11m, respectively. The reservoir member11ais formed with a plurality of common supply channels11s1and a plurality of common return channels11s2. Each of the common supply channels11s1and each of the common return channels11s2are common channels with respect to the pressure chambers11m. Each of the common supply channels11s1and each of the common return channels11s2communicate with a tank (not depicted) which stores the ink.

As depicted inFIG. 2, the plurality of pressure chambers11mare aligned in the sheet width direction, and construct four pressure chamber rows11m1to11m4arranged side by side in the conveyance direction. In each of the pressure chamber rows11m1to11m4, the pressure chambers11mare arranged in the sheet width direction at equal spacing distances therebetween. Pressure chambers11mwhich construct the pressure chamber rows11m1and11m2are arranged in the staggered manner such that the positions in the sheet width direction of the pressure chambers11mare different from one another. Pressure chambers11mwhich construct the pressure chamber rows11m3and11m4are arranged in the staggered manner such that the positions in the sheet width direction of the pressure chambers11mare different from one another.

As depicted inFIG. 2, the nozzles11nare aligned in the sheet width direction, and construct four nozzle rows which are arranged side by side in the conveyance direction, similarly to the pressure chambers11m. In each of the nozzle rows, the nozzles11nare arranged at equal spacing distances therebetween in the sheet width direction. Nozzles11nconstructing two nozzle rows on the right side inFIG. 2are arranged in the staggered manner such that the positions in the sheet width direction of the nozzles11nare different from one another. Nozzles11nconstructing two nozzle rows on the left side inFIG. 2are arranged in the staggered manner such that the positions in the sheet width direction of the nozzles11nare different from one another.

As depicted inFIG. 4, the nozzle plate11cis adhered to the lower surface of the pressure chamber plate11b. Namely, the nozzle plate11cis arranged on a side opposite to the piezoelectric actuator12with respect to the pressure chamber plate11b. The lower surface of the nozzle plate11cis an example of a first surface of the present disclosure.

The reservoir member11ais adhered to the upper surface of the pressure chamber plate11b, via the piezoelectric actuator12.

In addition to the common supply channels11s1and the common return channels11s2, the reservoir member11ais formed with: a plurality of supply channels11t1each of which communicates one of the pressure chambers11mwith one of the common supply channels11s1, and a plurality of return channels11t2each of which communicates one of the pressure chambers11mwith one of the common return channels11s2. Further, four recessed parts11axeach of which extends in the sheet width direction are formed in the reservoir member11a. The four recessed parts11axare formed in the lower surface of the reservoir member11a, and face the pressure chamber rows11m1to11m4, respectively, in the vertical direction. The supply channels11t1are examples of first channels of the present disclosure, and the return channels11t2are examples of second channels of the present disclosure.

A vibration plate17is provided on the upper surface of the pressure chamber plate11b. The vibration plate17is an insulating layer formed, for example, by oxidizing or nitriding a surface of a silicon single crystal substrate constructing the pressure chamber plate11b, and is arranged on substantially the entirety of the upper surface of the pressure chamber plate11b. The vibration plate17is arranged between the piezoelectric actuator12and the pressure chamber plate11b, and covers the pressure chambers11m. The upper surface of the vibration plate17is an example of a second surface of the present disclosure. Further, the nozzle plate11c, the pressure chamber11band the vibration plate17are combined so as to collectively correspond to an example of a first substrate of the present disclosure.

In the vibration plate17, through holes17x1(examples of first holes) are formed at portions, of the vibration plate17, facing the supply channels11t1in the vertical direction. Further, in the vibration plate17, through holes17x2(examples of second holes) are formed at portions, of the vibration plate17, facing the return channels11t2in the vertical direction. In a case that a pump (not depicted) is driven, the ink inside the tank is supplied to the common supply channel11s1, the ink passes through each of the supply channels11t1and one of the through holes17x1corresponding thereto, and the ink is supplied to one of the pressure chambers11mcorresponding thereto. Further, in the case that the pump is driven, the ink inside each of the pressure chambers11mflows into one of the through holes17x2and one of the return channels11t2corresponding thereto, and then flows into the common return channel11s2, and is recovered by the tank.

As depicted inFIG. 4, the piezoelectric actuator12is arranged on the upper surface of the pressure chamber plate11bvia the vibration plate17, and covers all the pressure chambers11mformed in the pressure chamber plate11b.

The piezoelectric actuator12includes, in an order from the lower side thereof, a common electrode12b, four piezoelectric bodies12cand a plurality of individual electrodes12d.

The common electrode12bis arranged on the upper surface of the vibration plate17.

As depicted inFIGS. 2 and 3, the common electrode12bincludes a first common electrode12b1, a second common electrode12b2, a third common electrode12b3and a fourth common electrode12b4which are separate and away from one another in the conveyance direction. Each of the first to fourth common electrodes12b1to12b4is a common electrode common to pressure chambers11mwhich are included in the pressure chambers11mand which construct one of the pressure chamber rows11m1to11m4, and is arranged to face, in the vertical direction, the pressure chambers11mconstructing one of the pressure chamber rows11m1to11m4. In other words, the common electrode12is divided into four corresponding to the pressure chamber rows11m1to11m4. Each of the common electrodes12b1to12b4is formed, for example, of platinum (Pt).

As depicted inFIGS. 2 and 3, the four piezoelectric bodies12cextend in the sheet width direction on the upper surfaces of the common electrodes12b1to12b4, respectively, and cover all the pressure chambers11mconstructing the pressure chamber rows11m1to11m4, respectively. Each of the piezoelectric bodies12cis formed, for example, of lead zirconate titanate (PZT).

The individual electrodes12dare arranged as individual electrodes12don each of the piezoelectric bodies12c, and face the pressure chambers11m, respectively, in the vertical direction.

As depicted inFIGS. 2 and 3, the individual electrodes12dare aligned in the sheet width direction, and construct four individual electrode rows12d1to12d4which are arranged side by side in the conveyance direction, similarly to the pressure chambers11m. Individual electrodes12dwhich construct each of the four individual electrode rows12d1to12d4face one of the common electrodes12b1to12b4in the vertical direction. In each of the individual electrode rows12d1to12d4, the individual electrodes12dare arranged in the sheet width direction at equal spacing distances therebetween. Individual electrodes12dconstructing the individual electrode rows12d1and12d2which are on the right side inFIG. 3are arranged in a staggered manner such that the positions in the sheet width direction of the individual electrodes12dare different from one another. Individual electrodes12dconstructing the individual electrode rows12d3and12d4which are on the left side inFIG. 3are arranged in a staggered manner such that the positions in the sheet width direction of the individual electrodes12dare different from one another.

Each of the individual electrodes12d, the common electrode12b, and a portion in one of the piezoelectric bodies12cwhich is sandwiched between each of the individual electrodes12dand the common electrode12bfunctions as a piezoelectric element12xwhich is deformable in accordance with application of the voltage to each of the individual electrodes12d. Namely, the piezoelectric actuator12has a plurality of piezoelectric elements12xfacing the pressure chambers11m, respectively. In a case that each of the piezoelectric elements12xis driven in accordance with application of the voltage to each of the individual electrodes12d(for example, in a case that each of the piezoelectric elements12xis deformed to project toward one of the pressure chambers11m), this changes the volume of one of the pressure chambers11m, thereby applying pressure to the ink inside the one of the pressure chambers11m, and thus causing the ink to be discharged form one of the nozzles11ncorresponding thereto.

The piezoelectric actuator12further has a plurality of individual traces12e, a plurality of individual contact points12f, two common contact points12g, a plurality of ring-shaped traces13, a common trace14and a plurality of coupling traces15. These traces12e,13to15and the contact points12f,12gare formed of a same material (for example, aluminum (Al)).

Each of the individual traces12eis provided on one of the individual electrodes12d, and connects one of the individual electrodes12dand one of plurality of individual contact points12fcorresponding thereto. Each of the ring-shaped traces13is connected to any one of the first to fourth common electrodes12b1to12b4. The common trace14is connected to the first to fourth common electrodes12b1to12b4via the coupling traces15. Further, the common trace14is connected to the two common contact points12g.

As depicted inFIG. 4, the individual contact points12fare disposed in an area of the pressure chamber plate11bnot covered with the reservoir member11a. Similarly, the two common contact points12gare also disposed in the area of the pressure chamber plate11bnot covered with the reservoir member11a.

The individual contact points12fand the two common contact points12gare aligned in one row in the sheet width direction on one side in the conveyance direction (the right side inFIG. 3) with respect to a group constructed of all of the individual electrodes12dprovided on the piezoelectric actuator12. The plurality of individual contact points12fare arranged at equal spacing distances therebetween in the sheet width direction. The two common contact points12gsandwich the individual contact points12ftherebetween in the sheet width direction.

The common trace14includes a facing part14a(an example of a first part) and two connecting parts14b(examples of two second parts). The facing part14ais arranged on an upstream side in the conveyance direction (the left side inFIG. 3) with respect to the group constructed of all of the individual electrodes12dprovided on the piezoelectric actuator12. The two connecting parts14bextend from the both sides, respectively, in the conveyance direction of the facing part14a(in the present embodiment, both ends in the sheet width direction of the facing part14a) toward a downstream side in the conveyance direction (the right side inFIG. 3) and are connected to the two common contact points12g, respectively. The facing part14aand the two connecting parts14bare formed integrally. The group of the individual electrodes12dare surrounded by the common trace14and the row of the individual contact points12f.

The facing part14ais a rectangular part which is elongated in the sheet width direction. Each of the two connecting parts14bis a rectangular part which is elongated in the conveyance direction. An end at the upstream side in the conveyance direction (left side inFIG. 3) of each connecting part14bis connected to the facing part14a. An end at the downstream side in the conveyance direction (right side inFIG. 3) of each connecting part14bis electrically connected to each common contact points12gvia a part (contact part14bx) that enters into a through hole of an insulating film12idescribed below. Each of the two connecting parts14bis coupled to the respective common electrodes12b1to12b4via the coupling traces15, respectively.

Each of the common trace14and the coupling traces15has a width greater than that of the other traces12eand13. The plurality of individual traces12eand the ring-shaped traces13have widths which are substantially same to each other. The plurality of individual traces12e, the ring-shaped traces13and the coupling traces15have thicknesses which are substantially same to one another.

Each of the individual traces12eextends in the conveyance direction. Each of the individual traces12ehas a contact point part12ex(seeFIG. 4) with respect to one of the individual electrodes12dcorresponding thereto, at one end in the conveyance direction of each of plurality of individual traces12e, and has an individual contact point12fat the other end in the conveyance direction of each of plurality of individual traces12e.

The individual traces12ethat are connected to individual electrodes12d(included in the individual electrodes12dforming the individual electrode row12d4, and except for the individual electrodes12dpositioned at the both ends in the sheet width direction) extend in the conveyance direction while passing through between the two individual electrodes12dincluded in each of the individual electrode rows12d1to12d3and adjacent to each other in the sheet width direction. The individual traces12ethat are connected to individual electrodes12d(included in the individual electrodes12dforming the individual electrode row12d3, and except for an individual electrode12dpositioned on one side in the sheet width direction (the lower side inFIG. 2)) extend in the conveyance direction while passing through between the two individual electrodes12dincluded in each of the individual electrode rows12d1and12d2and adjacent to each other in the sheet width direction. The individual traces12ethat are connected to individual electrodes12d(included in the individual electrodes12dforming the individual electrode row12d2, and except for an individual electrode12dpositioned on the other side in the sheet width direction (the upper side inFIG. 2)) extend in the conveyance direction while passing through between the two individual electrodes12dincluded in the individual electrode rows12d1and adjacent to each other in the sheet width direction.

As depicted inFIGS. 5 and 6, the ring-shaped traces13have ring-shaped parts13aand extending parts13b, respectively. Each of the extending parts13bextends from one of the ring-shaped parts13ain the conveyance direction. Each of the ring-shaped parts13ais formed to surround one of the through holes17x1or one of the through holes17x2. Each of the extending parts13bhas one end linked to one of the ring-shaped parts13a, and the other end connected to the common electrode12b. In the present embodiment, each of the ring-shaped traces13are arranged so as not to overlap with a partition wall between any two of the pressure chambers11mwhich are adjacent to each other in the sheet width direction. Ring-shaped traces13which have the ring-shaped parts13asurrounding the through holes17x1are examples of first ring-shaped traces. Ring-shaped traces13which have the ring-shaped parts13asurrounding the through holes17x2are examples of second ring-shaped traces.

Note that in the present embodiment, in order to enhance the insulating property between each of the individual traces12eand the common electrode12b, an insulating film12i(omitted inFIG. 2; seeFIGS. 4 and 6) is provided. The insulating film12iis arranged substantially on the entirety of the upper surface of the vibration plate17, and covers the first to fourth common electrodes12b1to12b4, the four piezoelectric bodies12c, the common trace14and the coupling traces15. Note, however, that the insulating film12icovers only the outer peripheral part of each of the individual electrodes12d, so as not to inhibit the driving of the piezoelectric elements12x, and that a central part of each of the individual electrodes12dis exposed from the insulating film12i. The insulating film12iis formed, for example, of silicon dioxide (SiO2).

The individual traces12e, the ring-shaped traces13, the individual contact points12fand the two common contact points12gare arranged on the upper surface of the insulating film12i.

The common trace14and the coupling traces15are arranged on the upper surface of the vibration plate7and arranged on the lower side relative to the insulating film12i, similarly to the common electrode12b.

Each of the individual traces12eis electrically connected to one of the individual electrodes12dcorresponding thereto, via a part, of each of the individual traces12e(contact point part12ex) which enters into a through hole of the insulating film12i. The extending parts13bof the ring-shaped traces13, respectively, are electrically connected to one of the first to fourth common electrodes12b1to12b4, via parts (contact point parts13x), of the extending parts13bof the ring-shaped trace13, respectively, each of which enters into a through hole of the insulating film12i.

Each of the contact point parts12exis provided on an end part on one side in the conveyance direction (the right side inFIGS. 2 to 5) of one of the individual electrodes12dcorresponding thereto. Each of the contact point parts13xis arranged at an end part on the one side in the conveyance direction (the right side inFIG. 5) or on the other side in the conveyance direction (the left side inFIG. 5) of one of the first to fourth common electrodes12b1to12b1corresponding thereto, respectively.

As depicted inFIG. 4, the COF18has an insulating sheet18bformed, for example, polyimide, etc., a plurality of individual trace18felectrically connected to the individual contact points12f, respectively, and two common traces (not depicted) electrically connected to the two common contact points12g, respectively.

One end of the COF18is adhered to the channel substrate11, via an adhesive A, in a state that the individual traces18fand the two common traces face the individual contact points12fand two common contact point12g, respectively. The other end of the COF18is electrically connected to the controller5(seeFIG. 1).

A driver IC19is mounted on a location between the one end and the other end of the COF18. The driver IC19generates a driving signal for driving the piezoelectric element12x, based on a signal from the controller5, and the driver IC19supplies the driving signal to each of the individual electrodes12d. The potential of the common electrode12bis maintained at the ground potential. In a case that the driving signal is supplied to each of the individual electrodes12d, the potential of each of the individual electrodes12dis changed between a predetermined driving potential and the ground potential.

In a case that the potential of a certain individual electrode12dis changed from the ground potential to the driving potential, there is generated difference in the potential between the certain individual electrode12dand the common electrode12b. With this, an electric field parallel to a thickness direction of a certain piezoelectric body12ccorresponding to the certain individual electrode12dacts on a portion which is sandwiched between the certain individual electrode12dand the common electrode12b(hereinafter referred to as an active part). In this situation, a polarization direction of the active part (thickness direction of the certain piezoelectric body12c) is coincident with the direction of the electric field, which in turn causes the active part expands in the thickness direction of the certain piezoelectric body12c, and to contract in a planar direction of the certain piezoelectric body12c. Accompanying with the contracting deformation of the active part, parts in the vibration plate17and the piezoelectric actuator12xrespectively which face a certain pressure chamber11mcorresponding to the certain individual electrode12dare deformed so as to project toward the certain pressure chamber11m. With this, the volume of the certain pressure chamber11mis reduced, which in turn applies energy to the ink inside the certain pressure chamber11m, thereby causing an ink droplet to be discharged from a certain nozzle11ncorresponding to the certain pressure chamber11m.

In the present embodiment, each of the pressure chambers11mis communicated with one of the supply channels11t1and one of the return channels11t2corresponding thereto and formed in the reservoir member11a, via one of the through holes17x1and one of the through holes17x2formed in the vibration plate17. Further, each of the through holes17x1and each of the through holes17x2are surrounded by one of the ring-shaped traces13. Owing to this configuration, even in such a case that the ink outflows from a connection part at which each of the pressure chambers11mis connected to one of the supply channels11t1and/or from a connection part at which each of the pressure chambers11mis connected to one of the return channels11t2, the ink is intercepted by the ring-shaped part13aof one of the ring-shaped traces13. As a result, it is possible to lower such a possibility that the ink outflowed from the connection parts might reach the piezoelectric actuator12x.

The extending parts13bof the ring-shaped traces13are electrically connected to one of the first to fourth common electrodes12b1to12b4, via the parts (contact point parts13x), of the extending parts13b, entering into the through holes of the insulating film12i. Further, the first to fourth common electrodes12b1to12b4are maintained at the ground potential. Accordingly, any difference in the potential is hardly generated between the ring-shaped traces13and the ink flowing in the supply channels11t1and the return channels11t2. Therefore, it is possible to lower such a possibility that the ink flowing in the supply channels11t1and the return channels11t2is conducted with the ring-shaped traces13.

Further, as depicted inFIG. 5, the shape of the ring-shaped trace13surrounding one of the through holes17x1is symmetric to the shape of the ring-shaped traces13surrounding one of the through holes17x2, relative to the individual electrodes12d, and the positions in the sheet width direction of the contact point parts13are substantially same to one another. Accordingly, it is possible to maintain the deformation of each of the piezoelectric elements12xto be uniform in the conveyance direction. Furthermore, the contact point part12exof each of the individual traces12eis provided on the central part in the sheet width direction of one of the individual electrodes12dcorresponding thereto, whereas the contact point part13xof each of the ring-shaped traces13is shifted from the central part in the sheet width direction of one of the individual electrodes12dcorresponding thereto. With this it is possible to form the individual traces12epreferentially.

Each of the ring-shaped traces13is arranged so as not to overlap with the partition wall between any two of the pressure chambers11mwhich are adjacent to each other in the sheet width direction. In other words, only the individual traces12eare arranged on the partition wall between any two of the pressure chambers11mwhich are adjacent to each other in the sheet width direction. Accordingly, there is no need to increase the thickness of the partition wall between any two of the pressure chambers11mwhich are adjacent to each other in the sheet width direction, for the arrangement of the ring-shaped traces13, and it is possible to secure a sufficient width in the sheet width direction of each of the pressure chambers11m.

The individual traces12eand the ring-shaped traces13are formed of the mutually same material (for example, aluminum (Al)), and are both formed on the upper surface of the insulating film12i(seeFIGS. 4 and 6). Accordingly, it is possible to easily form the individual traces12eand the ring-shaped traces13by one step, and it is possible to suppress any increase in the number of producing steps of the piezoelectric actuator12.

Next, a modification of the above-described embodiment will be explained. In the above-described embodiment, each of the ring-shaped traces13is electrically connected to any one of the first to four common electrodes12b1to12b4via the contact point part13x. The present disclosure, however, is not limited to this configuration. For example, as depicted inFIG. 7, it is allowable that each of the ring-shaped traces13is further electrically connected to other ring-shaped traces13via a connecting trace16extending in the conveyance direction.

Specifically, except for the ring-shaped traces13formed to construct a first row from the downstream-most side in the conveyance direction (the rightmost side inFIG. 7), each of ring-shaped traces13may be connected to at least one ring-shaped trace13, which is adjacent thereto in the conveyance direction, via the connecting trace16. Namely, it is allowable that the ring-shaped traces13formed on the downstream-most side in the conveyance direction are connected only to the common electrode12b, and that these ring-shaped traces13are not connected to other ring-shaped traces13. Further, the ring-shaped traces13which are arranged on the downstream-most side in the conveyance direction are arranged so as not to overlap with the partition wall between any two of the pressure chambers11mwhich are adjacent to each other in the sheet width direction.

In contrast, ring-shaped traces13formed to construct a second row from the downstream-most side in the conveyance direction are connected to ring-shaped traces13formed to construct a fifth row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively. Ring-shaped traces13formed to construct a third row from the downstream-most side in the conveyance direction are connected to ring-shaped traces13formed to construct a fourth row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively. The ring-shaped traces13formed to construct the fourth row from the downstream-most side in the conveyance direction are connected to the ring-shaped traces13formed to construct the third row and to ring-shaped traces13formed to construct a seventh row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively. The ring-shaped traces13formed to construct the fifth row from the downstream-most side in the conveyance direction are connected to the ring-shaped traces13formed to construct the second row and to ring-shaped traces13formed to construct a sixth row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively. The ring-shaped traces13formed to construct the sixth row from the downstream-most side in the conveyance direction are connected to the ring-shaped traces13formed to construct the fifth row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively. The ring-shaped traces13formed to construct the seventh row from the downstream-most side in the conveyance direction are connected to the ring-shaped traces13formed to construct the fourth row from the downstream-most side in the conveyance direction and to ring-shaped traces13formed to construct an eighth row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively. Further, the ring-shaped traces13formed to construct the eighth row from the downstream-most side in the conveyance direction are connected to the ring-shaped traces13formed to construct the seventh row from the downstream-most side in the conveyance direction, via a plurality of pieces of the connecting trace16, respectively.

Furthermore, each of the ring-shaped traces13formed to construct the sixth and eighth rows on the downstream-most side in the conveyance direction (the ring-shaped traces13on the third and first rows from the left inFIG. 7) is connected to the facing part14aof the common electrode14via one of the connecting traces16. Note that in this modification, the connecting traces are formed on the insulating film12i, similarly to each of the ring-shaped traces13. Further, the width in the conveyance direction of the facing part14aand the width in the sheet width direction of each of the two connecting parts14bare wider than the width in the sheet width direction of each of the connecting traces16.

According to the above-described modification, except for the ring-shaped traces13formed to construct the first row from the downstream-most side in the conveyance direction, each of the ring-shaped traces13is connected not only to any one of the second to fourth common electrodes12b2to12b4, but is connected, via the connecting trace16, also to the facing part14aof the common trace14. Namely, since the second to fourth common electrodes12b2to12b4, the ring-shaped traces13and the connecting traces16are parallel-connected, it is possible to lower the ground resistance.

In the above-described modification, each of the individual traces12eextends from the end part on the downstream side in the conveyance direction of one of the individual electrodes12dcorresponding thereto, toward the downstream side of the conveyance direction, and is connected to one of the individual contact points12fformed in the end part on the downstream side in the conveyance direction of the pressure chamber plate11b, and corresponding thereto, in a similar manner to the above-descried embodiment. Accordingly, the number of the individual trace12passing on the partition wall between the two pressure chambers11mwhich are adjacent to each other in the sheet width direction is increased, as the pressure chamber row is located further on the downstream side in the conveyance direction. In view of this situation, in the above-described modification, the ring-shaped traces13formed to construct the first row from the downstream-most side in the conveyance direction are not connected to the other ring-shaped traces13, and also are arranged so as not to overlap with the partition wall between any of the two pressure chambers which are adjacent to each other in the sheet width direction. Namely, since the ring-shaped traces13formed to construct the first row from the downstream-most side in the conveyance direction are not connected to the connecting traces16, it is possible to arrange only the individual trace12eon the partition wall of the two pressure chambers11mwhich are included in the pressure chamber row11m1on the downstream-most side in the conveyance direction and which are adjacent to each other in the sheet width direction.

Further, in the above-described modification, the ring-shaped traces13are serially-connected in the conveyance direction via the connecting traces16, and are connected to the facing part14aof the common electrode14. Accordingly, as compared with such a case that each of the ring-shaped traces13is connected to the facing part14aof the common trace14, without being connected to other ring-shaped trace(s)13, it is possible to reduce the number of traces for connecting the respective ring-shaped traces13to the facing part14aof the common chamber14. As a result, it is possible to suppress any increase in the width in the sheet width direction of the partition wall between the two pressure chambers11madjacent to each other in the sheet width direction.

Further, in the above-described modification, the width in the conveyance direction of the facing part14aand the width in the sheet width direction of each of the two connecting parts14bare wider than the width in the sheet width direction of each of the connecting traces16. Owing to this configuration, it is possible to further reduce the ground resistance.

It is allowable that, regarding the area in the horizontal direction of the contact point parts13xof the above-described embodiment, the area in the horizontal direction is made to be greater as in a contact point part13x, among the contact point parts13x, which is arranged further on the upstream side in the conveyance direction and in which more electric current flows.

In the above-described embodiment, it is allowable to further form an insulating film configured to cover the individual traces12e, the ring-shaped traces13, and the connecting traces16, in order to avoid any short circuit therebetween.

In the above-described embodiment and modification, the printer100performs printing on the recording sheet9in a so-called line head system in which the ink is discharged from the head unit1xelongated in the width direction of the sheet and fixed with respect to the printer100. It is allowable, however, that the printer100performs the printing on the recording sheet9in a so-called serial head system in which an ink-jet head is moved in the width direction of the sheet by a carriage.

In the above-described embodiment and modification, an explanation was made regarding the case wherein the present disclosure is applied to the ink-jet head which is configured to discharge the ink from the nozzles. The present disclosure, however, is not limited to this. The present disclosure is also applicable to a liquid discharging apparatus which is different from the ink-jet head and which is configured to discharge a liquid, different from the ink, from the nozzles.