DE69833978T2 - Droplet recorder and manufacturing method therefor - 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

The The present invention relates to a droplet depositing apparatus, in particular an ink jet printhead comprising: a channel which with a supply of droplet liquid communicates and an opening for ejecting droplet from, wherein at least one side wall of the channel depending is displaceable by electrical signals, causing an ejection of droplets the channel is effected.

1a Fig. 12 is a cross-sectional view of the channels of a prior art ink jet printhead construction according to WO 92/22429. A plate 12 piezoelectric ceramic material is in the direction 17 its thickness poled and in a surface with channels 11 formed, which on two sides parallel to the channel axis sides by channel walls 13 are limited. By means of electrodes 23 which are on both sides of each wall 13 are formed, an electric field can be applied to the piezoelectric material of the walls, causing them to shift in a shear mode in a direction transverse to the axis of the channel. As a result, pressure waves are generated in the ink, which lead to ejection of an ink droplet. These principles are known in the art, e.g. From EP-A-0 364 136.

The channels 11 are along a side parallel to the channel axis through the surface of a cover or a lid 14 closed, which conductive tracks 16 having the same pitch interval as the channels formed thereon. Between the tracks 16 and the channel wall electrodes 23 are solder joints 28 formed, whereby the cover or the cover is attached to the base or the bottom and creates an electrical connection between the electrodes and the web in a single step. To protect them from being corroded later by the ink, the electrodes and the webs are then provided with a passivating coating.

As in 1b which is a sectional view taken along the longitudinal axis A of a single channel of a printhead according to FIG 1a According to the prior art, is a nozzle plate 20 which respective nozzles 22 for ejecting ink, at the front of the plate 12 mounted while a manifold 26 for the ink at the back by a manifold assembly 21 is formed or defined. The railways 16 become the back of the cover or lid 14 for connection to a driver circuit, which is typically in a microchip 27 is formed or embodied, which in turn is driven by a signal, which by input tracks 18 is obtained.

In printheads This ink is the channel walls - and in particular the electrodes that are formed on it - often so passivated to them to protect against later to corrode by the ink. In this regard, reference is made to WO95 / 07820 Referenced.

Reference is also made to US 4,611,219 which discloses a base plate having piezoelectric or other liquid jet pressure generating elements disposed thereon, a spacer plate defining liquid chambers, and an orifice plate having - in one example - up to two openings for each liquid chamber.

This invention provides a droplet depositing apparatus comprising:
at least one elongate, open-topped droplet fluid channel defining defined longitudinal side walls facing one another and an elongated bottom surface extending between the side walls;
means for supplying droplet liquid to the channel;
a panel having elongated open-topped droplet fluid channels defined by facing elongate sidewalls and an elongated bottom surface extending between the sidewalls; wherein the channels are arranged side by side in a field direction and wherein at least one of the channels includes:
means for supplying droplet liquid to the channel;
means for applying an electric field to piezoelectric material in at least one of the sidewalls, thereby causing a displacement of the sidewall with respect to said elongate passage so as to expel a droplet from the passage; and
a cover that closes the open elongate top of the channel;
characterized in that at least one channel is formed with two openings for ejecting droplets, the openings being spaced along the length of the channel.

A Such a construction is sufficient for the arrangement of WO 98/52763 - the advantage a reduced number of components.

Corresponding methods are also claimed in the present invention and other aspects are discussed in other independent applications spelled out.

Further advantageous embodiments The invention is set forth in the description, drawings and dependent claims.

The Disclosure of all claims is hereby included as an existing clause, if not already stated above.

The Invention will now be described by way of example with reference to the following schematic Illustrations described for which is the following:

3 Fig. 10 is a sectional view taken along the channel axis of a print head;

4a and 4b show a detail of the rear part of the printhead according to 3 , in each case before and after the attachment of the cover or the cover;

5 Fig. 11 is a sectional view taken along the channel axis of another print head;

6 is a sectional view, wherein the section was performed along the channel axis of a still further printhead;

7 Fig. 10 is a sectional view taken along the channel axis of a print head according to an embodiment of the present invention;

8th is a perspective detail view of the end of the piezoelectric body of the printhead according to 7 ;

9 and 10 are respectively a sectional view and a detail sectional view showing an alternative embodiment of the in 7 represented head.

3 FIG. 12 illustrates a printhead having such properties as shown in FIG 3 are common, and the printhead of the prior art according to 1 and 2 is denoted by common reference numerals.

As in the prior art device, a body is 12 of a piezoelectric ceramic material in the thickness direction with channels 11 formed, which from each other by channel walls 13 are separated. As known from EP-A-0 364 136, referred to above, electrodes are used 23 along each wall 13 in the ink-containing channel 11 formed and also extend along a rear groove 100 to the back face 130 of the body. In addition, a cover or a lid 14 provided, whose one side 15 the open side of each of the channels 11 closes, a nozzle plate 20 with nozzles 22 for the ejection of droplets and a manifold for supplying ink to the channel in the form of a transverse recess which enters the body 12 is incorporated or cut. On the website 15 the cover or the lid 14 are tracks 16 formed (by suitable and well-known methods), which in turn with the microchip 27 (which figuratively in 3 and not drawn to scale), which in turn receives input signals from input tracks 18 receives.

A detail of the rear portion of the printhead prior to attachment of the cover is shown in FIG 4a shown; a passivation layer 140 (in 3 not shown, but by dashed hatching with solid lines in 4a shown) is over the entirety of the electrodes 23 (by hatching with solid lines both in 3 as well as in 4a ) in the channel and partially along the rear groove 100 , In contrast to the prior art construction, the passivation is carried out before the cover is attached, and preferably according to the method described in WO95 / 07820, which belongs to the present assignee, and the contents of which are incorporated herein by reference becomes.

A mechanical connection between the body and the side 15 the cover or the lid 14 is by means of an adhesive layer 160 reached, which on the end faces of the walls 13 in the area of the channels 11 is applied before the cover or the lid and the body are joined together and preferably according to the method which is discussed in WO95 / 04658. 4b represents the assembled printhead, wherein the adhesive bond at 220 is specified. Such an adhesive bond may in fact be more robust and have a higher limit fatigue life than the corresponding prior art solder joint as described above.

The electrical connection between the conductive tracks 16 on the cover or lid and that part of the electrode 23 in the rear groove 100 is by a projection 170 a stretchable, deformable, conductive material, such as one at the end 180 the train 16 attained attached lot. When assembling the cover or lid with the body, as in 4b shown is the lead 170 with the electrode 23 in contact and is deformed, where by an effective electrical contact 200 between the electrode 23 and train 16 is created.

A pearl 190 A sealing paste or adhesive of high viscosity is also applied so that when assembled an ink seal 210 between the end of the ink channel 11 and the electrical contact 200 is formed. Such a seal later protects the electrical contact from corrosion by ink. Preferably, the seal is positioned so that it has the free end 150 the passivation layer 140 spans and thereby prevents ink leakage under the passivation layer from where it could otherwise attack the electrode material.

In 5 is a ceramic piezoelectric body 290 as in the previous embodiment poled in the direction of the thickness and with channels 11 formed, which by channel walls 13 are separated, wherein on each side of the channel walls in turn an electrode 23 is trained. However, ink ejection takes place from a centrally located nozzle 320 instead, which either directly in the cover or the lid 305 is formed or, as shown here, in a nozzle plate 330 is formed, which communicates with the channel via an opening 340 , which is formed in the cover or the lid, is in communication. The body 290 is additionally with two manifolds 310 equipped for the supply of ink from both ends of the channel, as indicated by arrows 300 is specified. Another design (not shown) supplies the manifolds with ink from a reservoir.

Such a "double-ended" configuration of a printhead is disclosed in WO91 / 17051, and has advantages in terms of lower operating voltage over the "single-ended" configuration described above is. Furthermore, the configuration of the floor 290 suitable to make by molding - a technique which is potentially more attractive from the viewpoint of manufacturability than conventional sawing techniques described in the aforementioned EP-A-0 364 136.

The connection of the channel electrode 23 with conductive tracks 370 , which on the surface of the cover or the lid 350 are formed, which, however, the body 290 was already facing in relation to the 3 . 4a and 4b described, and is in on one side of the body 290 trained groove 360 arranged. Similarly, the area of the channel itself (its channel walls have been passivated prior to assembly) and at the end 380 of the body, which is not occupied by an electrical connection, the cover or the lid 350 attached to the body of piezoelectric ceramic material by a conventional adhesive bond (not shown).

To get the ink from the actual channel 11 to the outlet of the nozzle 320 To minimize the distance to be traversed - and thereby reduce pressure losses and consequently reductions in the rate of droplet ejection - the nozzle can 320 in the cover or the lid 350 be self-trained. Advantageously, the nozzle is formed or formed by laser ablation or ablation or ablation, as described for example in WO93 / 15911, and for this purpose, the cover or the cover of a easily abzudagenden or to be evaporated or to be ablated material, such as polyimide, polycarbonate, polyester or polyetheretherketone typically having a thickness of 50 microns to be made.

The Rigidity of a cover or cover plate, which consists of a formed such light abradable or evaporable material is, by applying a coating of a stiffer Materials on the inner and outer surfaces of the ablatable or evaporable or ablatable cover or cover plate elevated become. In particular, is for this purpose silicon nitride appropriate; it can also be used are used as a passivating coating in the process according to the aforementioned WO095 / 07820 and is deposited as a smooth coating suitable for the following Application of a non-wettable coating is suitable and due to their non-conducting properties, electrodes of adjacent channels do not off. Two layers of such material, which on each side of the cover or the lid are made of polyimide and each of which has a thickness of about 5% of that of Cover or lid (2.5 microns in the case of a 50 μm thick cover or such a cover) typically increase the flexural rigidity by a factor of 5-10 (based on the standard compound Beam theory (standard composite carrier theory) and by assuming a value of the Young's modulus for the stiffening material of about 100 times bigger than that of the polymer and a good adhesion between the stiff and Polymeric materials). Such a thin layer has no meaning Influence on how easily the cover or cover plate removed or can be evaporated or ablated to form a nozzle or form, in particular if the material of the layer itself in some degree abradable, evaporable or ablatierbar.

Broadly formulated, the cover plate for an ink jet printer has a layer a first easily abradable or ablatable material to which further layers are connected on its opposite sides, wherein the further layers are each made of a material having a rigidity of at least an order of magnitude greater than that of the first material and having a thickness of at least an order of magnitude less than that of the first layer.

It is now up 6 Referenced. There is shown a printhead which includes both first and second aspects of the present invention. The body 400 of piezoelectric ceramic material is with channels 11 formed, further with the channels separating walls 13 and electrodes 23 , which with actuating signals via conductive tracks 410 to be supplied, which are connected to a driver circuit (not shown). Unlike the previous embodiments, however, droplet ejection from a nozzle occurs 420 instead, which with an opening 430 communicates or communicates in the body 400 at the closed floor area 440 of the canal 11 is trained - this is in contrast to 5 where the nozzle 320 in a cover or a lid 350 is arranged, which or which the open upper side of the channel 11 closes.

The molding is again the preferred method of manufacture for the channeled body 400 , and the arrangement of 4a and 4b in turn, for the electrical connection between the electrodes 23 and conductive tracks 410 used. The connection hole 430 may also be formed during the molding or injection molding process, or may be subsequently formed by, for example, a laser. The cover or the lid 450 no longer contains a nozzle, but instead has openings 460 formed for the admission of ink. Such an arrangement has a smaller number of components than previously discussed embodiments and therefore also has advantages in the production. Alternatively, the apertures for the supply of ink could also be formed in the channeled member, for example at the ends of the channels.

7 illustrates an embodiment of the present invention.

The printhead according to 7 also has a cover or cover component 500 with inlet openings 520 . 522 and 524 for the ink, which at each end and in the middle of a channel 11 which is in a piezoelectric body 530 is formed, are arranged. The channel walls are through a gap 540 in two sections 550 . 560 divided, each through openings 520 . 522 respectively. 522 . 524 be supplied, each section independently by means of respective electrodes 570 . 580 driven by driver circuits (not shown) via conductive tracks 650 . 660 be actuated, are actuated. For each section is a respective nozzle 610 . 620 provided, which in a nozzle plate 615 is formed and with a section of the channel via communication holes 630 . 640 formed in the bottom surface of the channel at locations formed in the middle region between the respective inlet openings for this section.

A such configuration gives a printhead which is two parallel Rows of independent operable from each other Having printing elements, which thus compact or of compact design is and which a reduced operating voltage per unit of droplet ejection speed, due to the "double-ended" ink supply too each channel section.

Unlike previous embodiments, the conductive tracks are 650 . 660 which electrically connect the channel electrodes to the driving chips are formed on the piezoelectric body itself, advantageously in the same step in which the electrodes 570 . 580 deposited or deposited on the canal walls. Such an arrangement is known from EP-A-0 397 441. The connection between the train 650 . 660 and the drive chip 590 . 600 can be achieved by any conventional method including wire bonding or gold ball connection.

The piezoelectric body 530 can be injection molded: in addition to providing clear manufacturing advantages, such a process allows the ends of the channel to be formed 11 be shaped like this in 8th is shown, namely with a smooth smooth transition 700 from the upper surface 720 of the body to both the canal wall 730 and the long floor surface 710 of the canal. This in turn avoids discontinuities in the subsequently precipitated electrode material and the associated heating effects, which could have a detrimental effect on the service life of the printhead as a whole.

Alternatively, channels could be formed in the piezoelectric component by sawing using a disc cutter, as e.g. As described in EP-A-0 309 148 - and in the sectional and detailed sectional views of 9 and 10 is shown. It follows that the Tie fe of the canal 11 more gradually expires at each end, as with 800 is shown, and that the wall of the piezoelectric channel, which between adjacent sawn channels 11 is formed or defined, continuously between the two active sections 550 . 560 runs. A break 810 however, in the electrodes on the channel walls at a location between the two sections ensures that each wall in the active section can be actuated independently by signals passing through an electrical input 820 be supplied. Such an interruption can be achieved, for example, by masking during the deposition of the metal plating or by removing the plating by a laser.

The connection between the electrodes on the channel walls and the electrical input 820 although not shown in detail, may be achieved by any of the known techniques, including wire bonding between webs, in flat "run-out" grooves which are in the range 900 in the back part of the canal 11 are formed (described in the aforementioned EP-A-0 364 136) or by conductive adhesive (for example, anisotropic conductive adhesive) between conductive tracks in the area 900 are formed on the surface of the piezoelectric plate itself (which is described in EP-A-0 397 441).

As in the embodiment of 7 is every channel 11 along its two active sections 550 . 560 over suitable lengths 820 . 830 a cover or cover component 500 closed, which also with openings 520 . 522 . 540 which allows ink to be directed to each of the active sections of the channel and optionally allow ink to be circulated through each channel section for cleaning purposes, as is well known. Openings may be arranged to define the edge of an active section, as in the case of the opening 522 in which case the manufacture is simplified. In the example shown, the width of the cover or the lid opening 552 and the lid closures 820 . 803 of the same order of magnitude, typically 2 mm.

The ejection of ink from each of the active sections is in turn via apertures, which the channel with the opposite surface of the piezoelectric component (plate 860 ), to the one in which the channel is formed. In the present embodiment, these openings take the form of slots 840 . 850 which extend some distance (typically 200 microns - in the longitudinal direction of the channel), so some leeway in the arrangement of the respective nozzles 870 . 880 in the nozzle plate 890 to allow. The displacement of nozzles is generally necessary each time a simultaneous droplet ejection from adjacent channels is not possible, e.g. In common wall printheads of the type illustrated, e.g., EP-A-0 376, and will therefore not be discussed in detail.

Printheads of the present invention also be produced in a modular format, as in the aforementioned WO91 / 17051 with each module at its opposite end or end faces is formed with respective channel parts so that after the abutment of Modules to each other more channels between the respective pairs of abutting modules be formed. In such arrangements, the respective channel parts at least part of a slot in the channel bottom, and with sufficient length is formed so that even if a pair of abutting modules and their respective slot parts are not exactly aligned, an overlap between the two slot halves is present, which is sufficient to be adapted to a nozzle.

As in the previous embodiment, the nozzles are 870 . 880 in a nozzle plate 890 formed, which, as shown, over the substantially entire length of the piezoelectric plate 860 extends so as to provide a sufficiently large area for engaging a cover ("capping") and / or wiping mechanism.

The piezoelectric channel walls can to Example in opposite directions perpendicular to the plane the channel axes be polarized, as for example from the EP-A-0 277 703 is known. Alternatively, the polarization of the channel walls parallel to the plane of the channel axes, with electrodes in the canal walls themselves are formed, as for example from EP-A-0 528 647 is known.

It not every channel in a printhead needs to be able to droplet to launch: active Channels, which are able to eject droplets, can themselves in the printhead with inactive - so named dummy channels - alternate, like this is described, for example, in the aforementioned EP-A-0 277 703 is.

Claims (14)

A droplet deposition apparatus comprising: an array of elongate, open-topped droplet fluid channels ( 11 ), which by facing, elongated side walls ( 730 ) and an elongated bottom surface ( 710 ) extending between the side walls are formed; wherein the channels are juxtaposed in a field direction, and at least one of the channels includes: means ( 520 . 522 . 524 ) to supply droplet liquid to the channel; Medium ( 660 . 570 . 580 . 650 ) to apply an electric field to piezoelectric material ( 530 ) in at least one of the side walls ( 730 ), whereby a displacement of the side wall with respect to the elongated channel is effected so that a droplet is ejected from the channel; and a cover ( 500 ), which the open, elongated top ( 720 ) of the channel closes; characterized in that the elongated bottom surface ( 710 ) of the at least one channel with two openings ( 610 . 620 ) is configured for the ejection of droplets, wherein the openings are spaced along the length of the channel. Apparatus according to claim 1, wherein the means to droplet liquid supply, supply openings in the cover which is spaced along the channel are that they lie on either side of each opening. Apparatus according to claim 1 or claim 2, wherein the piezoelectric material in a Shear mode is deformed when exposed to the electric field becomes. Apparatus according to any the claims 1 to 3, wherein an electrode on a channel-facing surface of the Channel wall is formed. Apparatus according to claim 4, wherein an electrode is also formed on the channel wall is, on a surface opposite to the channel facing surface of the channel wall. Apparatus according to any the claims 1 to 5, wherein the channel wall in response to electrical signals in a direction transverse to the axes of the channels is displaceable. Apparatus according to any the claims 1 to 6, wherein the elongated bottom surface by a base or a Ground is formed, with the base or the ground and the long stretched sidewalls are integrally formed. Apparatus according to any The preceding claim further comprising a nozzle plate having nozzles, which with the openings to Droplet ejection stand. A method of making a droplet deposition apparatus, comprising the steps of: creating a body ( 530 ), which includes piezoelectric material and an array of elongate, open-topped droplet liquid channels ( 11 ), wherein the channel by facing, elongated side walls ( 730 ), and an elongated bottom surface ( 710 ) which extends between the side walls is formed; wherein the channels are juxtaposed in a field direction; and at least one of the channels, the following applies: formation of two openings ( 610 . 620 ) for the ejection of droplets, by piezoelectric material ( 530 ) in the elongate bottom surface of the channel, the openings being spaced along the length of the channel; Provision of funds ( 660 . 570 . 580 . 650 ) for applying an electric field to piezoelectric material in at least one of the side walls, whereby the displacement of the side wall with respect to the elongated channel is effected so that a droplet can be ejected from the channel; and closing the elongated open top of the channel with a cover ( 500 ). Method according to claim 9, which shows the step of closing the open, elongated top of the channel by means of a cover which contains droplet supply openings integrated, which are spaced along the channel, that they on both sides of each opening lie. Method according to claim 9 or claim 10, which is the step of forming the long stretched floor surface and the long side walls so that they are integral. Method according to claim 11, which illustrates the steps of providing a body piezoelectric material and the removal of material from this body to thereby form the channel in the body. Method according to claim 9, which comprises the following steps: Provide a body in the form of a sheet or a thin layer with first and second opposite surfaces; Remove of material from the first surface of the body and thereby forming the channel; Forming the two openings in the elongated bottom surface of the Channels, with the openings with the second surface of the sheet or the thin layer keep in touch. A method according to claim 13, including the step of polarizing the piezoelectric material of the sheet in a direction perpendicular to the first and second surfaces having.