KR100567262B1 - Droplet Deposition Apparatus and Methods of Manufacture thereof - Google Patents

Abstract

A piezoelectric printhead or other droplet deposition apparatus has parallel liquid containing channels defined by a base and displaceable walls, and covered by a cover number. The channels each have at least one nozzle for ejecting droplets. Each nozzle may be disposed in the base, the cover then having two ink supply parts spaced lengthwise of each channel on opposite sides of the nozzle. Alternatively two longitudinally spaced nozzles may be provided in the base of each channel. The cover may have a conductive track corrected to wall-displacing electrodes, the points of connection being outside the channels. <IMAGE>

Description

Ink printing apparatus and its manufacturing method {Droplet Deposition Apparatus and Methods of Manufacture

TECHNICAL FIELD The present invention relates to an ink printing apparatus, in particular an inkjet printhead, wherein the ink printing apparatus includes a channel communicating with an ink source and a hole for ejecting ink droplets, wherein at least one channel sidewall is displaced in response to electrical signals. It is possible to eject ink droplets from the channel.

1A is a cross-sectional view of channels of a prior art inkjet printhead configuration according to WO92 / 22429, filed by Applicant and incorporated herein by reference. The piezoelectric ceramic sheet 12 is polarized in the thickness direction 17 and has channels 11 on one surface that contact the channel walls 13 on both sides parallel to the channel axis. By means of electrodes 23 formed on both sides of each wall 13, an electric field can be applied to the piezoelectric material of the walls to cause the piezoelectric material to bend in the direction crossing the channel axis in shear mode. Thereby, pressure waves are generated in the ink causing the ejection of the ink droplets. These principles are known in the art, for example from EP-A-0 364 136, filed by the applicant and incorporated herein by reference.

By the surface of the cover 14 having conductive tracks 16 of the same pitch spacing as the ink channels formed thereon, the channels 11 are closed along one side located parallel to the channel axis. Solder bonds 28 are formed between the tracks 16 and the channel wall electrodes 23 to secure the cover to the base in one step and to make electrical connections between the electrodes and the tracks. The electrodes and tracks are then coated with a protective film to prevent corrosion later by the ink.

As shown in FIG. 1B, which is a sectional view taken along the longitudinal axis A of a single channel in the conventional print head shown in FIG. 1A, the nozzle plates 20 each having an ink jet nozzle 22 are formed of the sheet 12. While mounted at the front, the ink manifold 26 is defined at the rear by the manifold structure 21. The tracks 16 are led to the rear of the cover 14 for connection with a drive circuit typically included in the microchip 27 which is in turn driven by a signal received via the input tracks 18.

In printheads of this kind, the channel walls-and in particular the electrodes formed thereon-are often coated with a protective film to prevent corrosion accompanied by ink. See WO95 / 07820 which is hereby incorporated by reference.

However, in the apparatus described above, such a conventional protective coating made prior to the attachment of the cover can suppress the formation of solder joints between the electrodes and the tracks. On the other hand, the protective coating after the cover is applied can only be applied from the end of the channel, lowering the coating quality of the electrodes and tracks, especially in the center of the channel away from the channel end.

The present invention aims at a printhead configuration which is easy to coat with a protective coating while retaining the connection advantages associated with conductive tracks formed in a cover of conventional construction.

Accordingly, the present invention is, in one aspect, constituted by an ink printing apparatus comprising means for communicating with an ink source and at least one channel having holes for ejection of ink droplets;

The channel abuts a channel wall coupled with the actuating means on at least one side lying parallel to the channel axis; The actuating means displaces the channel wall in response to electrical signals to eject ink drops from the channel;

The channel abuts the cover surface on the other side parallel to the channel axis, the cover surface having at least one conductive track formed thereon for transmitting electrical signals to the actuation means, the electrical connection between the track and the actuation means being located outside the channel. do.

According to the invention the protective coating at this point is no longer necessary, since the only electrical connection point between the track and the actuator is located outside of the channel and therefore is not in contact with the ink (potentially corrosive). The channel may itself be protective coated through the open top of the channels. Thereafter, the cover can be attached and an electrical contact is made between the conductive tracks of the cover and the actuating means associated with the channel walls. Even for printheads that do not require a protective coating-intended for firing because of the type of ink, the electrical connection points located outside the channel in accordance with the present invention are more suitable for solder joints formed in the longitudinal direction of the channel of the conventional device of FIGS. Less prone to failure due to fatigue.

The method according to the first aspect of the present invention comprises a manufacturing method of an ink printing apparatus, which method comprises:

An operation for ejecting ink droplets from the channel by forming a base element comprising at least one channel with an open top and displacing the channel in response to electrical signals on at least one side positioned parallel to the channel axis Contacting a channel wall associated with the means;

Closing the channel with a cover surface formed thereon at least one conductive track for transmitting electrical signals to said actuating means, on the other side parallel to the channel axis; And

Electrically connecting the conductive track and the actuating means at a point located outside the channel.

Preferably, closing the channel results in electrical connection of the conductive track and the actuation means, simplifying the manufacturing process.

The first aspect of the invention also provides:

A bottom sheet of piezoelectric material, polarized in a direction perpendicular to the sheet, spaced apart from each other in an array direction perpendicular to the longitudinal direction of the channels, each defined by opposing sidewalls and a bottom surface extending between the sidewalls A bottom sheet having a plurality of parallel channels open at an upper side thereof;

A top sheet facing the bottom surface of the channels and bonded to the sidewalls to close the channels on top of the channels;

Respective nozzles in communication with the channels for ejecting ink droplets;

Connecting means for connecting said channels with a printing ink source;

Each channel having a front portion provided with electrodes on opposite sides of at least one side wall defining the channel to form a shear mode actuator for ejecting ink droplets from the channel; A rear having an electrically-conductive coating in electrical contact with at least one electrode on the channel-facing side of the front sidewalls; Separating means for separating the front part and the rear part; And

And conductive tracks formed on the surface of the top sheet bonded to the side walls, wherein the conductive tracks are composed of an ink printing apparatus in electrical contact with an electro-conductive coating of the rear portion.

The manufacturing method of the matching ink printing device is:

Forming a bottom sheet of piezoelectric material layer, the piezoelectric material layer being polarized in a direction perpendicular to the sheet;

A plurality of parallel channels spaced apart from each other in an array direction perpendicular to the longitudinal direction of the channels and defined by opposing sidewalls and a bottom surface extending between the sidewalls, further having a front portion and a rear portion, and having an upper side open. Forming;

Forming electrodes on opposite sides of at least one sidewall defining a front portion of each channel to form a shear mode actuator for ejecting ink droplets from the channel; And

Forming an electrically-conductive coating in the rear of each channel in electrical contact with each electrode;

Providing a top sheet having a surface with conductive tracks formed thereon; And

Bonding a surface of a top sheet having conductive tracks to the sidewalls to close the channels on top of the channels;

Making electrical contact between the tracks and each electro-conductive coating of each channel; And

Providing sealing means for separating the front and rear portions of each channel.

A second aspect of the invention is:

At least one longitudinal ink channel defined by opposing longitudinal sidewalls and a longitudinal bottom surface extending between the sidewalls, the upper side being open;

Means for applying an electric field to the piezoelectric material in at least one sidewalls to displace the wall associated with the channel such that ink droplets are ejected from the longitudinal channel; And

A cover closing the open top side of the longitudinal channel;

The bottom surface of the longitudinal channel is formed with a hole for ink droplet ejection;

The cover incorporates two ports for the supply of ink droplets, and the ports consist of ink printing devices spaced apart along the channel on both sides of the aperture.

This configuration also makes known printheads, in particular the manufacture of printheads of the same kind as the "top shooter" discussed in WO91 / 17051 (filed by the applicant and incorporated herein by reference). Simplify FIG. 2 shows a cross-sectional view taken along the channels of such a conventional printhead, in which a configuration consistent with FIG. 1 is indicated by a corresponding reference numeral. Ink ejection is generated from a nozzle formed in the channel cover element 60 while ink is supplied to the channel through the ports 33, the ports being formed in the channel base, a base separate from the channeled piezoelectric element 12. An ink supply tube (not shown) formed in the element 35 is typically connected in their turn.

According to the invention, holes communicating with the ink ejection orifices are formed in the bottom surface of the channel, allowing the cover element to integrate a port for supplying ink to the channel. As a result, an additional separate base element is no longer needed.

According to a third aspect of the present invention,

At least one longitudinal ink drop channel defined by opposing longitudinal sidewalls and a longitudinal bottom surface extending between the sidewalls, the upper side being open;

Means for supplying ink droplets to the channel;

Means for applying an electric field to the piezoelectric material at at least one sidewall to displace the wall associated with the channel such that ink droplets are ejected from the longitudinal channel; And

A cover for closing the open upper side of the longitudinal channel,

The bottom surface of the longitudinal channel is formed with two holes for ink droplet ejection, and the holes include ink printing devices spaced apart along the channel.

This configuration gives the device of PCT Application No. PCT / GB98 / 01495-filed by the applicant and incorporated herein by reference-with the advantage that the number of components as described above is reduced.

Corresponding method claims are also included in the present invention, other aspects being as described in the other dependent claims.

Other preferred embodiments of the invention are described in the detailed description, drawings and independent claims.

All disclosed claims are considered to be incorporated herein in accordance with the provisions of the law.

The invention is now described by way of example with reference to the following figures. here:

3 is a cross-sectional view taken along the channel axis of the printhead according to the first embodiment of the first aspect of the present invention;

4A and 4B show details of the rear portion of the printhead shown in FIG. 3 before and after being attached to the cover, respectively;

5 is a cross-sectional view taken along the channel axis of the printhead according to the second embodiment of the first aspect of the present invention;

6 is a cross sectional view along the channel axis of the printhead incorporating the first and second aspects of the invention;

7 is a sectional view taken along the channel axis of the printhead according to the second embodiment of the second aspect of the present invention;

FIG. 8 is a perspective view showing in detail the end of the piezoelectric body of the printhead shown in FIG. 7; FIG.

9 and 10 are cross-sectional and detailed cross-sectional views showing another embodiment of the printhead shown in FIG. 7, respectively.

3 shows a printhead according to the first embodiment of the first aspect of the present invention. Components common to that of the prior art printhead shown in FIGS. 1 and 2 and in FIG. 3 are indicated by common reference numerals.

As in the conventional apparatus, the piezoelectric ceramic body 12 polarized in the thickness direction has channels 11 separated by channel walls 13. As known from the above-mentioned EP-A-0 364 136, the electrodes 23 are formed along each wall 13 of the ink-receiving channel 11 and along the rear groove 100 of the back of the body ( 130). In addition, the surface 15 intersects the body 12 with the cover 14 closing the open surface of the respective channels 11, the nozzle plate 20 having the nozzles 22 for ink ejection, and the body 12. A manifold is provided for supplying engraved form of ink to the channel. Surface 15 of cover 14 has tracks 16 formed thereon (appropriate processes are well known), which tracks microchip 27 (shown figuratively in FIG. 3 and not sized). In turn, the microchip receives input signals from the input tracks 18 in turn.

The rear portion of the printhead before the cover is attached is shown in detail in FIG. 4A. The protective layer 140 (not shown in FIG. 3 but indicated by dashed hatching in FIG. 4A) is in part along the back and grooves of the electrode 23 (indicated by solid hatching in FIGS. 3 and 4A) of the channel. Is applied. In contrast to the conventional construction, the protective coating is carried out prior to the attachment of the cover, preferably according to the method described in WO95 / 07820, filed by the applicant and incorporated herein by reference.

Mechanical bonding between the body and the surface 15 of the cover 14 is, prior to assembly of the cover and the body, preferably in accordance with the method discussed in WO95 / 04658, filed by the applicant and incorporated herein by reference, This is achieved by an adhesive layer 160 applied to the end surfaces of the walls 13 in the region of the channels 11. 4B shows the assembled printhead, which has an adhesive joint, indicated at 220. Such a joint is indeed stronger than the matching solder joint of the conventional structure described above, and has a longer fatigue life.

The electrical connection between the conductive tracks 16 of the cover and the electrode 23 of the portion corresponding to the track of the backward groove 100 is malleable, variable, such as solder, attached to the end 180 of the track 16. And projections 170 of conductive material. As shown in FIG. 4B, on the assembly of the cover and the body, the protrusion 170 contacts and deforms the electrode 23 to provide an effective electrical contact 200 between the electrode 23 and the track 16. .

 Also, beads 190 of sealing paste or high viscosity glue are applied to form an ink seal 210 in the assembly between the end of the ink channel 11 and the electrical contact 200. This seal protects the electrical contacts from subsequent corrosion due to the ink. Preferably the seal is positioned to open the free end 150 of the protective layer 140 to prevent ink leakage from where it might otherwise strike the electrode material 23.                 

5 shows a second embodiment of the first aspect of the present invention. As in the previous embodiment, the ceramic piezoelectric body 290 is polarized in the thickness direction and has channels 11 separated by channel walls 13 which in turn have electrodes 23 formed on each side. . However, ink jetting is generated directly from the nozzle 320, which is formed directly on the cover, or formed in the nozzle plate 330 in communication with the channel through the hole 340 formed in the cover, as shown. do. Additionally body 290 has two manifolds 310 for supplying ink from both ends of the channel, as indicated by arrows 300. Another structure (not shown) supplies ink to the manifold from the ink bottle.

Such "dual-end" printhead configurations are disclosed in WO91 / 17051, filed by the applicant and incorporated herein by reference, in terms of lower operating voltages compared to the "single-end" configuration described above. It is advantageous. Moreover, the construction of the base 290 is suitable for manufacturing with molding-which is perhaps more attractive than the conventional sawing technique described in EP-A-0 364 136 described above.

However, the connection of the conductive tracks 370 formed on the surface of the cover 350 opposite the channel electrode 23 and the body 290 is as already described with reference to FIGS. 3, 4A and 4B and the body It is located in the groove 360 formed on one side of the (290). Similarly, in the area of the channel itself (applied with a shield before the channel walls are assembled) and at the end 380 of the body not occupied by the electrical connection, the cover 350 is a conventional adhesive binder (not shown). Is attached to the piezoelectric ceramic body.

In order to minimize the distance traveled by the ink from the appropriate channel 11 to the outlet of the nozzle 320, the nozzle 320 itself may cover the cover 350 itself in order to reduce pressure loss and thus a reduction in the ink ejection speed. It may be formed in. Preferably the nozzle is formed by laser ablation, as described, for example, in WO93 / 15911, incorporated by reference,

To this end the cover is made of a material that is easily excised, a polymer such as polyimid, ploycarbonate, polyester or polyetheretherketone, which typically has a thickness of typically 50 μm. It can also be made.

The stiffness of the cover plate formed of such an easily cut material may be increased by applying a coating of harder material to the inner and outer surfaces of the releasable cover plate. Particularly suitable for this purpose is silicon nitride. It can also be used as a protective coating in the process of WO95 / 07820 described above, deposited as a soft coating suitable for the resulting application of the non-wetting coating, and does not short the electrodes of adjacent channels because of its non-conductivity. Two layers of these materials, located on both sides of the polyimide cover, each having a thickness of approximately 5% of the cover thickness (2.5 μm for a 50 μm thick cover) (based on standard composite beam theory and strengthening the material) The Young's modulus value is typically 100 times greater than the value of the good joint between the coalesced and rigid material and the polymer material), typically increasing the flexural stiffness to a factor of 5-10. This thin layer does not have any significant effect on the ease with which the cover plate can be cut, especially if the layering material itself can be cut to some extent.

In broad terms, the cover plate for an inkjet printer includes a first material that can be easily abbreviated with other layers bonded to opposite sides thereof, each of the other layers having a size greater than at least the rigidity of the first material ( It is made of a material having an order of magnitude stiffness and has a thickness of at least an order of magnitude less than the thickness of the first layer.

Referring to Fig. 6, a printhead incorporating the first and second aspects of the present invention is shown. The piezoelectric ceramic body 400 has electrodes 23 through which operating signals are supplied via channels 11, channel-separation walls 13 and conductive tracks 410 connected to a drive circuit (not shown). However, unlike the previous embodiments, the ink printing is generated from the nozzle 420 in communication with the hole 430 formed in the closed bottom surface 440 of the channel 11 in the body 400-this is the nozzle Contrast with FIG. 5 where 320 is located in cover 350 which closes the open top of channel 11.

In addition, molding is the preferred method of manufacturing the channeled body 400, and the apparatus of FIGS. 4A and 4B is also adapted for electrical connection between the electrodes 23 and the conductive tracks 410. In addition, the communication hole 430 may be formed during the molding process, for example, may be formed subsequent to the molding process by a laser. Cover 450 no longer incorporates a nozzle but instead has ink inlet ports 460. Such devices have fewer component counts than the embodiments discussed above and consequently have manufacturing advantages. Alternatively, the ink supply ports may be formed at the channeled element, for example at the channel ends.

In addition, the printhead of FIG. 7 employs a cover element 500 having ink inlet ports 520, 522, 524 located at both ends and in the middle of the channel 11 formed in the piezoelectric body 530. The channel walls are separated into two zones 550, 560, which are fed to the ports 520, 522 and 522, 524, respectively, by a gap 540, each zone through conductive tracks 650, 660. Independently operable by respective electrodes 570, 580 driven by a drive circuit (not shown). Zone of channel 11 through communication holes 630 and 640 formed in the bottom surface of the channel at a point located midway between each inlet port for the zone, for each zone Respective nozzles 610 and 620 are provided, which are in communication with each other.

This configuration is described in co-pending UK patent application 0710530.8, filed by the applicant and incorporated herein by reference, which application has two parallel rows of independently operable printing elements. Initiating a printhead, the printing elements are compact and the operating voltage per unit ink drop printing is reduced because of the "double-end" ink supply to each channel region.

Unlike the previous embodiments, the conductive tracks 650, 660 that electrically connect the channel electrodes to the drive chips are preferably piezoelectric bodies in the same step in which the electrodes 570, 580 are deposited on the channel walls. It is formed on itself.

Such a device is known from EP-A-0 397 441, filed by the Applicant and incorporated herein by reference, and is therefore not described in further detail here. The connection between the tracks 650, 660 and the drive chips 590, 600 may be accomplished by any conventional method, including wire bonding or gold ball connection.

The piezoelectric body 530 may be molded. In addition to the obvious manufacturing advantages, this process allows the end of the channel 11 to be formed as shown in FIG. 8. That is, the end of the channel is formed with a smooth, continuous transition 700 from the upper surface 720 of the body to the channel wall 730 and the bottom surface 710 of the longitudinal channel. This in turn eliminates discontinuities in the subsequently deposited electrode material and combined heating effects that may have a detrimental effect on the operating life of the entire printhead.

Alternatively, the channels may be formed in the piezoelectric element by cutting with a disk cutter-as described, for example, in EP-A-0 309 148, which is shown in cross section and in detail in FIGS. 9 and 10. have. The depth of channel 11 runs out at each end, as shown at 800, A piezoelectric channel wall defined between adjacent cutting channels 11 runs out between two operating zones 550, 560. However, the break 810 of the electrode on the channel walls located between the two zones ensures that each wall of the operating zone can be operated independently by a signal supplied through the electrical input 820. Such gaps may be achieved, for example, by masking during the deposition of metal plating or by removing the plating with a laser.

Although not shown in detail, the connection between the electrodes of the channel walls and the electrical input 820 can be accomplished by any known technique, which is a shallow " "formed in the area 900 behind the channel 11. Wire bonds between tracks formed in run-out &quot; grooves (as described in EP-A-0 364 136 above) or conductive adhesives between conductive tracks formed in regions 900 on the surface of the piezoelectric sheet itself (e.g. Anisotropic conductive adhesive) (as described in EP-A-0 397 441).

As in the embodiment of FIG. 7, each channel 11 is closed along two operating zones 550, 560 by a cover element 500 of suitable lengths 820, 830, the cover element being each channel. It has ports 520, 522, 524 that allow ink to be supplied to the operating zone and, optionally, generally allow ink to circulate through each channel zone for cleaning purposes. As in the case of port 522, the ports may be positioned to define the edge of the operating zone, which simplifies manufacturing. In the example shown, the width of the cover port 552 and the cover closure lengths 820, 803 are the same size, which is typically 2 mm in size.

Ink ejection from each operating zone passes through holes that communicate the channel with the surface opposite the surface on which the channel of the piezoelectric element (sheet 860) is formed. In this embodiment, these holes take the form of slots 840 and 850, and the slots are provided in the channel to allow some margin in the placement of the respective nozzles 870 and 880 in the nozzle plate 890. Extend a predetermined distance in the longitudinal direction, typically 20 μm. In general, the offsetting of the nozzle is necessary whenever simultaneous spraying of ink from adjacent channels is not possible, for example in the "shared wall" printheads of the kind shown, and in general, for example, EP-. It is known from A-0 396. Therefore, no further discussion is made here.                 

The printheads according to the invention may be made in the form of modules as described in WO91 / 17051 described above, each module having a respective channel such that different channels are formed between each adjacent pair of modules by adjoining the modules together. With a portion formed on opposite end surfaces. In such an apparatus, each channel portion may comprise at least a portion of a slot, wherein a slot is formed in each channel base and the two slots, although a pair of adjacent modules and their respective slots are not perfectly aligned. It is of sufficient length to maintain sufficient overlap to accommodate the nozzle between the two slot halves.

As in the previous embodiment, the nozzles 870, 880 are formed in the nozzle plate 890, which, for example, is shown, for example, with a capping and / or wiping mechanism. It may generally extend beyond the entire length of the piezoelectric sheet 860 to provide an adequately large area for engagement.

Although the invention has been described in terms of the embodiments only, it can be seen that a wide range of modifications are possible without departing from the scope of the invention. Features shown in connection with the first aspect of the invention may equally apply to the second aspect and vice versa.

For example, piezoelectric channel walls can be polarized in opposite directions perpendicular to the plane of the channel axis, for example as known from EP-A-0 277 703, incorporated by reference. Alternatively, the polarization of the channel walls can be parallel to the plane of the channel axis with electrodes formed on the channel walls themselves, for example as known from EP-A-0 528 647.

Also, not all channels of the printhead need to be able to eject ink droplets. That is, the actuation channels capable of ejecting ink droplets may be alternated with non acting channels-also referred to as "dummy" channels-as described, for example, in EP-A-0 277 703 described above. have.

Claims (63)

At least one longitudinal ink channel defined by opposing longitudinal sidewalls and a longitudinal bottom surface extending between the sidewalls, the upper side being open; Electrode means for applying an electric field to the piezoelectric material in at least one sidewalls to displace the wall associated with the channel such that ink droplets are ejected from the longitudinal channel; And A cover closing the open top side of the longitudinal channel; The bottom surface of the longitudinal channel is formed with a hole for ink droplet ejection; The cover incorporates two ports for supply of ink droplets, the ports being spaced apart along the channel on either side of the aperture. 2. The apparatus of claim 1 wherein the supply ports are spaced apart by the same amount on both sides of the aperture. The device of claim 1 or 2, wherein the bottom surface of the longitudinal channel is formed with at least two holes, the holes spaced apart along the channel. 4. The apparatus of claim 3, wherein the cover incorporates ink drop supply ports spaced along the channel so as to lie on either side of each aperture. delete delete delete delete delete delete At least one longitudinal ink drop channel defined by opposing longitudinal sidewalls and a longitudinal bottom surface extending between the sidewalls, the upper side being open; Means for supplying ink droplets to the channel; Electrode means for applying an electric field to the piezoelectric material at at least one sidewall to displace the wall associated with the channel such that ink droplets are ejected from the longitudinal channel; And A cover for closing the open upper side of the longitudinal channel, The bottom surface of the longitudinal channel is formed with two holes for ink droplet ejection, the holes are spaced apart along the channel. 12. The apparatus of claim 11, wherein the means for supplying ink droplets comprises supply ports spaced along the channel in the cover so as to be located on both sides of each channel. 12. The apparatus of claim 1 or 11, wherein the piezoelectric material deforms in shear mode when subjected to an electric field. delete delete 12. The apparatus of claim 1 or 11, wherein the channel wall is displaceable in a direction crossing the axis of the channels in response to an electrical signal. 12. The apparatus of claim 1 or 11, wherein the longitudinal bottom surface is defined by a base and the base and the longitudinal sidewalls are integral. delete Providing a body comprising a piezoelectric material, the body having at least one longitudinal channel open at an upper side, the channel being defined by opposing longitudinal sidewalls and a longitudinal bottom surface extending between the sidewalls; Forming a hole in the longitudinal bottom surface for ejection of ink droplets; Providing means for displacing a wall associated with the channel to apply an electric field to the piezoelectric material at at least one sidewall to eject ink from the longitudinal channel; And Closing the open top side of the longitudinal channel by a cover having two ink supply ports arranged to be spaced apart along the channel on both sides of the aperture. delete delete The method of claim 19, Providing a body in the form of a sheet having first and second surfaces on opposite sides; Removing material from the first surface of the body to form a channel; Forming a hole in the bottom surface of the longitudinal channel in communication with the second surface of the sheet. 23. The method of claim 22 including polarizing the piezoelectric material of the sheet in a direction perpendicular to the first and second surfaces. Providing a body comprising a piezoelectric material, the body having opposing longitudinal sidewalls and at least one longitudinal ink drop channel open at an upper side and defined by a longitudinal bottom surface extending between the sidewalls; Forming two holes spaced along the channel at the longitudinal bottom surface of the channel and for ink droplet ejection; Providing means for displacing a wall associated with the channel to apply an electric field to the piezoelectric material at at least one sidewall to eject ink from the longitudinal channel; And closing the open longitudinal upper side of the channel with a cover. 25. The method of claim 24 including closing the open top side of the longitudinal channel with a cover incorporating ink supply ports spaced along the channel so as to lie on either side of each aperture. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete 12. The apparatus according to claim 1 or 11, wherein the cover comprises a surface formed on at least one conductive track for transmitting electrical signals to the electrode means. 60. The apparatus of claim 59, wherein an electrical connection point between the tracks and the electrode means is located outside of the channel. Device according to claim 1 or 11, wherein the protective coating extends over the electrode means. 62. The apparatus of claim 61, wherein the protective coating extends below the boundary of the channel. 12. The apparatus according to claim 1 or 11, wherein a plurality of channels are formed in a line, the channels being located parallel to each other to define a channel wall therebetween.

Images