CN104718081B - Droplet deposition apparatus and method for depositing droplets of a fluid - Google Patents

Abstract

An apparatus for ejecting droplets, such as an inkjet printhead, with improved productivity, comprising: an array (2) of elongate fluid chambers, wherein each chamber is in communication with a nozzle (6), the array extending in an array direction; a common fluid inlet manifold (4); a common fluid outlet manifold (5); and a fluid supply that produces a through-flow of fluid from a common fluid inlet manifold through each chamber in the array and into a common fluid outlet manifold; two walls defining each chamber are formed of a piezoelectric material so as to produce droplet ejection from the nozzle; this injection flow takes place simultaneously with the throughflow, which may have a value greater than the maximum injection flow; each nozzle may be elongate in the length of the chamber parallel thereto and/or may have an outlet with an area that confers advantages in terms of productivity and temperature control.

Description

Droplet deposition apparatus and method for depositing droplets of a fluid

technical field

The present invention relates to a droplet deposition apparatus and method for depositing droplets of a fluid. Particularly beneficial application may be found in droplet deposition apparatus comprising: an array of elongate fluid chambers, a common fluid inlet manifold and a common fluid outlet manifold and for generating Tubes, means of flow through each chamber in the array and into the outlet manifold, each chamber communicating with an orifice for droplet ejection.

Background technique

An example of such a droplet deposition apparatus is provided in WO 00/38928, from which Figures 1, 2, 3 and 4 are taken. Figure 1, for example, illustrates a "page wide" printhead 10 with two rows of nozzles 20, 30 (each nozzle having a circular profile) extending (in the direction indicated by arrow 100) The width of a sheet of paper and it allows ink to be deposited across the entire width of the page in a single pass. Ejection of ink from a nozzle is effected by applying an electrical signal to the drive means associated with the fluid chamber (the fluid chamber communicates with the nozzle), as for example from EP-A-0 277 703, EP-A-0 278 590 and, more particularly are known from WO 98/52763 and WO 99/19147. To simplify manufacturing and increase yield, a "page-wide" row of nozzles may be composed of multiple modules, one of which is shown at 40, each module having an associated fluid chamber and actuation device and utilizing, for example, a flexible Circuitry 60 is connected to associated driver circuitry (integrated circuit ("chip") 50 ). Ink is supplied to and from the printheads through corresponding holes (not shown) in the end cap 90 .

Figure 2 is a perspective view from the rear of the printhead of Figure 1 with the end cap 90 removed to show the printhead support structure 200 containing ink flow passages 210, 220, 230 extending the width of the printhead . Through an aperture (omitted from view in FIGS. 1 and 2 ) in one of the end caps 90 , ink enters the printhead and ink supply passage 220 , as shown at 215 in FIG. 2 . As the ink flows along the passages, it is drawn into the corresponding ink chambers, as shown in Figure 3, which is a cross-sectional view of the printhead taken perpendicular to the direction of extension of the nozzle rows. From passage 220, ink flows into first and second parallel rows of ink chambers (indicated at 300 and 310, respectively) via holes 320 (shown shaded) formed in structure 200 . Having flowed through the first and second rows of ink chambers, ink exits via holes 330 and 340 to join the ink flow along the respective first and second ink outlet passages 210, 230, as at 235 express. These inks meet at a common ink outlet (not shown) formed in the end cap and which may be positioned at the opposite or the same end of the printhead as the end in which the inlet aperture is formed.

Additional details of the chambers and nozzles of the particular printhead shown in FIGS. 1-3 are given in FIG. 4 , which is a cross-sectional view taken along the fluid chamber of module 40 . The fluid chamber takes the form of a channel 11 machined or otherwise formed in the base member 860 of piezoelectric material so as to define piezoelectric channel walls which are subsequently coated with electrodes to form the channel wall actuator, As known for example from EP-A-0 277 703 . Each channel half is closed along the lengths 600, 610 by respective segments 820, 830 of the cover member 620, which is also formed with ports 630, 630, 230 in communication with the fluid manifolds 210, 220, 230, respectively. 640, 650. The break in the electrodes at 810 allows independent operation in the channel walls in either half of the channel by means of electrical signals applied through the electrical input (flex circuit 60). Ink ejection from each channel half passes through openings 840, 850 which communicate the channel with the surface of the piezoelectric base member opposite the surface in which the channel is formed. Nozzles 870, 880 for ink ejection are then formed in a nozzle plate 890 which is attached to the piezoelectric component.

Those skilled in the art will appreciate that a variety of alternative fluids can be deposited by the droplet deposition apparatus: droplets of ink can travel onto, for example, paper or other substrates, such as ceramic tiles, to form an image, as in inkjet This is the case in printing applications; alternatively, droplets of fluids can be used to build structures, for example electroactive fluids can be deposited onto substrates such as circuit boards to enable prototyping of electrical devices, or fluids containing polymers or Molten polymer can be deposited in successive layers to produce a prototype model of an object (as in 3D printing). A module similar in construction to a standard inkjet printhead may be used to provide a droplet deposition device suitable for such alternative fluids with some adaptations to enable treatment of the particular fluid in question.

Figures 5 and 6 are exploded perspective views of a printhead employing a double-ended side-firing configuration similar to that of Figures 1-4, but taken from WO 01/12442. As can be seen, two rows of channels spaced relative to each other in the media feed direction are used, with each row extending the width of the page in a direction transverse to the media feed direction.

The two rows of channels are formed in respective strips 110 a , 110 b of piezoelectric material that are bonded to the planar surface 120 of the substrate 86 . Electrodes are disposed on the walls of the channel such that electrical signals can be selectively applied to the walls. The channel walls thus act as actuator members and can cause droplet ejection. Substrate 86 is formed with conductive tracks 192 that are electrically connected to respective channel wall electrodes (eg, by solder joints) and extend to the edge of the substrate, the respective driver circuits (integrated circuits 84a, 84b) for each row of channels. Position at that edge.

As can also be seen from Figures 5 and 6, the cover member 130 is bonded to the top of the channel walls, creating a closed "active" channel length that can accommodate the pressure waves that allow droplet ejection. Nozzle holes each having a circular outline are formed in the cover member 130 , and the nozzle holes communicate with the passage to enable ejection of liquid droplets.

The base plate 86 is also provided with ports 88, 90 and 92 which communicate to the inlet and outlet manifolds. As in the structure described with reference to Figures 1 to 4, an inlet manifold may be disposed between two outlet manifolds, wherein the inlet manifold thus supplies ink to the channels via port 90, and ink from the two rows of channels via ports 88 and 92. until the corresponding outlet manifold is removed. As shown in FIG. 6 , conductive track 192 may be turned around ports 88 , 90 and 92 .

The printheads disclosed in WO 00/38928 and WO 01/12442 may thus be considered examples of drop deposition devices comprising an array of elongate fluid chambers, each chamber communicating with an orifice for drop ejection, the The devices have a common fluid inlet manifold and have a common fluid outlet manifold, and means for generating fluid flow into the inlet manifold, through each chamber in the array, and into the outlet manifold.

Contents of the invention

The present invention relates to improvements in such droplet deposition apparatus.

Increasing process productivity is a key driver in droplet deposition processes such as printing applications and industrial deposition in many industrial sectors. This need for increased productivity can often be met by increasing the frequency at which droplets are ejected from the nozzles or alternatively by increasing the size of each fluid droplet.

An additional method for increasing productivity is to increase the total number of nozzles or orifices (more nozzles deliver more ink), either by producing a printhead with a higher density of nozzles in the array direction or by using multiple suitably Aligned droplet deposition modules (eg, printheads) direct the substrate to achieve this.

Depending on the application, these approaches can be combined to further increase productivity. However, while each of these approaches may be used to increase productivity depending on the situation, there may be practical trade-offs to consider in each case. For a particular method, there may also be existing physical limitations to increase productivity.

For example, increasing the orifice density would be limited by the smallest size the actuation element or fluid chamber can be fabricated from. In printheads such as those shown in Figures 1 to 5, there will be limitations in terms of the density with which channels can be sawed in the piezoelectric material. Furthermore, increasing the aperture density will affect the size of the actuation elements (especially if the packaging of the device remains the same) and thus the actuation elements will be less powerful and thus compromise the performance of the device to some extent.

As noted above, multiple drop ejection modules (eg, printheads) can also be used to increase throughput. A droplet deposition apparatus comprising multiple modules may reduce the impact on constraining the minimum size of the actuation element, but the cost of the apparatus may be prohibitive considering it comprises multiple high cost droplet deposition modules.

Also, in some cases it may be appropriate to use a droplet deposition module with a larger package to increase throughput. This can significantly alleviate some of the constraints on the size of the actuation element; however, a larger package may come at the expense of reduced clarity. Depending on the particular application, such a reduction in sharpness may not be acceptable.

The present invention can improve some of these problems. In some specific embodiments, it may increase the productivity of the droplet deposition apparatus, while in other embodiments may additionally or alternatively undergo various improvements.

Thus, according to a first aspect of the present invention there is provided a droplet ejection apparatus comprising: an array of elongated fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common a fluid inlet manifold; a common fluid outlet manifold; and for creating a through-flow of fluid from the common fluid inlet manifold through each chamber in the array and into the common fluid outlet manifold The device of ( _QTF ); wherein each of said fluid chambers communicates with said common fluid inlet manifold at one longitudinal end and communicates with said common fluid outlet manifold at an opposite longitudinal end; wherein Each chamber is associated with at least one piezoelectric actuator for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting from the chamber and from the orifice, the jet flow being consistent with The through-flows occur simultaneously, the jet flow has a maximum value Q _E ; wherein each of the orifices is elongated in a direction parallel to the longitudinal axis of a respective one of the fluid chambers.

The elongation of the orifices parallel to the longitudinal axis of the respective fluid chambers may enable an increase in orifice size without unduly affecting the orifice density in the array direction. Additionally, or otherwise, increasing the orifice size by elongation of the orifice parallel to the longitudinal axis may enable spacing of the nozzle inlet from the wall of the fluid chamber. This may enable the device to be manufactured more easily as it provides more margin for error in positioning the orifice relative to the chamber. Furthermore, the spacing may avoid or reduce damage to the walls during formation of the aperture, particularly if the aperture is formed by ablation. The increased size of the orifice may allow the orifice to eject fluid droplets having an increased volume, thereby increasing the productivity of the device.

This particular orientation of the orifices may have additional advantages. For example, since the fluid chambers communicate at one longitudinal end with the common fluid inlet manifold and at the opposite longitudinal end with the common fluid outlet manifold, through-flow may be directed along the longitudinal length of the fluid chambers. . Thus, the direction of elongation of the throughflow and orifice can be aligned. This can lead to a particularly efficient removal of debris, such as air bubbles and dust particles, from the vicinity of the orifice during use of the device. Such removal of debris can reduce the incidence of orifice plugging during use, thereby increasing the reliability of the device.

Furthermore, this orientation of the aperture may cause sound waves (which may be generated by the piezoelectric actuator during use of the device) to persist near the aperture for a longer period of time than with a circular aperture. Typically, such sound waves will be generated at each of the longitudinal ends of the chamber after actuation of the piezoelectric actuator and travel inwardly towards the orifice. Since the orifice is thus elongated in the direction of travel of the sound waves, the sound waves can persist at the orifice for a relatively longer time, thereby increasing the efficiency of the injection.

Preferably, for each of said orifices, the outlet may have a smaller aspect ratio than the inlet. Applicants have found that orifices that are elongated parallel to the longitudinal axis, while having certain advantages as discussed above, may in some cases experience lower directional accuracy than circular orifices. However, the Applicant has also found that this problem of directional accuracy can be corrected by suitably shaping the outlet of the orifice. Suitably, therefore, the aspect ratio of the outlet of each orifice may be smaller than the aspect ratio of the inlet. Such an arrangement may still benefit from the advantages of elongation described above, since the inlet may be elongated in the longitudinal direction. Preferably, the outlet of each orifice may have an aspect ratio between 1.0 and 1.2 and, in some embodiments, the outlet of each orifice may have an aspect ratio of about 1.0. It may also be appropriate that each orifice is tapered such that the area (and aspect ratio) of the nozzle outlet is smaller than the area (and aspect ratio) of the nozzle inlet.

Suitably, the major dimension of the inlet of each of said orifices may be aligned with the longitudinal axis of the fluid chamber. Optionally, the major dimension of the outlet may also be aligned with the longitudinal axis of the fluid chamber.

Additionally, or otherwise, the outlet and inlet of the orifice may be approximately elliptical and, suitably, the major axis of the ellipse may be aligned with the longitudinal axis of the fluid chamber. Preferably, the outlet of each of said orifices may be approximately circular.

Preferably, each of said fluid chambers has a width w in said array direction so as to define a theoretical circular area _AT = 1/ _4TTW ² , the orifice outlet of each chamber having an area An where 0.48 _AT >A _n > _0.2AT .

It has been found that the through-flow serves to cool the device and in particular the actuator. In addition, the jet flow can also be used to cool the device (especially near the actuator), since heat is transferred to the fluid and then removed from the device with the jetted droplets. It would therefore be expected that as the orifice area increases, the cooling of the device will improve as the size of the droplets being sprayed will increase and thus more fluid will be removed from the chamber by the spray. However, applicants have discovered that, unexpectedly, orifices with larger areas do not necessarily provide more efficient cooling, and that orifices with areas within this particular range are more efficient than holes with larger areas. The mouth of the device provides more efficient cooling for devices, and especially piezoelectric actuators. Using only modest values of through-flow typically provides this cooling effect.

More preferably, the value of the through-flow is such that Q _TF >0.25Q _E . Using a throughflow in this range, using an orifice as defined above, may allow cooling of the device, and particularly the actuator, to such an extent that the fluid passing through the chamber is typically heated by only 2 degrees or less. This shows that the temperature difference can significantly increase the useful life of the device.

In this regard, it should be understood that a small increase in the temperature of the fluid is indicative of a large increase in the temperature of the device and particularly the actuator. Estimates for equipment life can be based on the Arrhenius model, where chemical attack of components is a major factor in failure of equipment. Therefore, it should be understood that device lifetime may be sensitive to even small temperature differences.

It should also be understood that large temperature differentials can result in adverse effects on droplet ejection characteristics. Applicants have found that such properties are sensitive to the rheology of the fluid, and that even small changes in temperature can significantly affect the rheology.

Still more preferably, the value of the through-flow is such that Q _TF >Q _E . This can lead to a significant increase in device reliability: since more fluid is passing through the orifice than is flowing through the orifice, even during maximum spraying, the through-flow is particularly effective in flushing debris away from the vicinity of the nozzle.

Optionally, each of said fluid chambers has a width w in said array direction, thereby defining a theoretical circular area A _T =1/4TTW ² , the orifice outlet of each chamber has an area A _n , and wherein 0.80 A _T >A _n >0.20A _T and Q _TF >4Q _E .

Applicants have found that with through-flows in this range, devices with orifices with areas as high as 0.80 _AT will generally have similar temperature differentials as devices with orifices with significantly smaller areas. Specifically, the temperature differential experienced within devices with larger orifices (those with areas up to 0.80 Å _T ) will typically be lower than those with smaller orifices (those with areas greater than 0.20 Å _T ). ) within 0.2 degrees of the temperature difference experienced in the device. Because 0.2 degrees is generally considered to be within a normal tolerance range, it can be neglected depending on the environment, and the performance of both devices in terms of lifetime and droplet characteristics is substantially the same.

Suitably, said longitudinal axis of said fluid chamber is parallel to the direction of channel extension. Preferably, the channel extension direction is perpendicular to the array direction.

According to a second aspect of the present invention there is provided a droplet ejection apparatus comprising: an array of elongate fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common fluid inlet a manifold; a common fluid outlet manifold; and a through-flow (Q _TF ); wherein each of said fluid chambers communicates with said common fluid inlet manifold at one end and communicates with said common fluid outlet manifold at an opposite end; wherein each chamber communicates with said common fluid outlet manifold; At least one piezoelectric actuator is associated for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting from the chamber and from the orifice, the jet flow being connected to the through-flow Occurring simultaneously, the jet flow has a maximum value Q _E ; wherein each of the fluid chambers has a width w in the array direction, thereby defining a theoretical circular area _AT = 1/4TTW ² , each chamber The orifice outlet has an area An _{where 0.48AT >A n > 0.20AT .}

As discussed in detail above, orifices with areas in the range _0.48AT >A _n > _0.20AT can provide a particularly small gap between the fluid at the inlet manifold and the fluid at the outlet manifold. temperature difference. This can correspond to a particularly efficient cooling of the device, and in particular of the piezoelectric actuator, without requiring large values for the throughflow. Such an effect does not necessarily rely on the elongation of the orifices described above.

Preferably, the value of _QTF is sufficient to ensure that the temperature of the fluid returning to the outlet common manifold remains substantially within 0.2 degrees of the fluid entering the chamber from the common inlet manifold.

According to a further aspect of the present invention there is provided a droplet ejection device comprising: an array of elongate fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common fluid an inlet manifold; a common fluid outlet manifold; and a through-flow for generating fluid from the common fluid inlet manifold through each chamber in the array and into the common fluid outlet manifold ( ( _QTF ) device; wherein each of said fluid chambers communicates with said common fluid inlet manifold at one end and communicates with said common fluid outlet manifold at an opposite end; wherein each chamber associated with at least one piezoelectric actuator for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting from the chamber and from the orifice, the jet flow communicating with the communication channel flow occurs simultaneously, the jet flow has a maximum value Q _E ; wherein each of the fluid chambers has a width w in the array direction, thereby defining a theoretical circular area _AT = 1/4TTW ² , each chamber The orifice outlet of has an area A _n , and where 0.80A _T >A _n >0.20A _T and Q _TF >4Q _E .

As discussed above, applicants have found that devices with orifices with areas as high as 0.80 _ΔT will typically have the same orifice with orifices with significantly smaller areas using a through-flow defined in the range _QTF > _4QE . mouth of the device similar temperature difference. Specifically, the temperature differential experienced within devices with larger orifices (those with areas up to _0.80AT ) will typically be lower than those with smaller orifices (those with areas greater than _0.20AT ). within 0.2 degrees of the temperature difference experienced in the device. Because 0.2 degrees is generally considered to be within a normal tolerance range, it can be neglected depending on the environment, and the performance of both devices in terms of lifetime and droplet characteristics is substantially the same.

According to a still further aspect of the present invention there is provided a droplet ejection apparatus comprising: an array of elongate fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common a fluid inlet manifold; a common fluid outlet manifold; and for creating a through-flow of fluid from the common fluid inlet manifold through each chamber in the array and into the common fluid outlet manifold The device of (Q _TF ); wherein each of said fluid chambers communicates at one end with said common fluid inlet manifold and at the opposite end with said common fluid outlet manifold; wherein each A chamber is associated with at least one piezoelectric actuator for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting the chamber and from the orifice, the jet flow being connected to the orifice Through-flow occurs simultaneously, the jet flow having a maximum value Q _E ; wherein the orifices are arranged in an orifice plate having a thickness of t micrometers, each orifice being tapered so as to define a taper angle θ; wherein the fluid Each of the chambers has a width of w microns in the array direction, thereby defining a practical circular area _AP = 1/4π(we-2t·tanθ) ² , where e takes a value of 10 microns, and the aperture of each chamber The mouth outlet has an area A _n , where 3A _P >A _n >1.25A _P .

This value e may correspond to the process precision with which the chambers and orifices are formed.

In an embodiment, the taper angle θ may take a value between 5 and 15° and preferably may take a value between 10 and 12°. It should be understood that references to taper angles should not be interpreted as implying that the orifice will necessarily have the same taper at all locations. Suitably, therefore, the taper angle Θ may correspond to the average taper angle for the orifice.

According to a still further aspect of the present invention there is provided a droplet ejection apparatus comprising: an array of elongate fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common a fluid inlet manifold; a common fluid outlet manifold; and for creating a through-flow of fluid from the common fluid inlet manifold through each chamber in the array and into the common fluid outlet manifold The device of (Q _TF ); wherein each of said fluid chambers communicates at one end with said common fluid inlet manifold and at the opposite end with said common fluid outlet manifold; wherein each A chamber is associated with at least one piezoelectric actuator for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting the chamber and from the orifice, the jet flow being connected to the orifice Through-flow occurs simultaneously, the jet flow having a maximum value Q _E ; wherein the orifices are arranged in an orifice plate having a thickness of t micrometers, each orifice being tapered so as to define a taper angle θ; wherein the fluid Each of the chambers has a width of w microns in the array direction, thereby defining a theoretical circular area _AP = 1/4π(we-2t·tanθ) ² , where e takes values between 5 and 10 microns, The orifice outlet of each chamber has an area An _where 5A _P >A _n >1.25A _P , and Q _TF >4Q _E .

This value e may correspond to the process precision with which the chambers and orifices are formed.

In an embodiment, the taper angle θ may take a value between 5 and 15° and preferably may take a value between 10 and 12°.

According to yet another aspect of the present invention, there is provided a droplet ejection apparatus comprising: an array of elongated fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common a fluid inlet manifold; a common fluid outlet manifold; and for creating a through-flow of fluid from the common fluid inlet manifold through each chamber in the array and into the common fluid outlet manifold The device of (Q _TF ); wherein each of said fluid chambers communicates at one end with said common fluid inlet manifold and at the opposite end with said common fluid outlet manifold; wherein each A chamber is associated with at least one piezoelectric actuator for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting the chamber and from the orifice, the jet flow being connected to the orifice The through-flow occurs simultaneously, the jet flow having a maximum value Q _E ; where the orifice outlet of each chamber has an area A _n , where 1600 μm ² >A _n >650 μm ² .

According to yet another aspect of the present invention, there is provided a droplet ejection apparatus comprising: an array of elongated fluid chambers, each chamber communicating with an orifice for droplet ejection, the array extending in the direction of the array; a common a fluid inlet manifold; a common fluid outlet manifold; and for creating a through-flow of fluid from the common fluid inlet manifold through each chamber in the array and into the common fluid outlet manifold The device of (Q _TF ); wherein each of said fluid chambers communicates at one end with said common fluid inlet manifold and at the opposite end with said common fluid outlet manifold; wherein each A chamber is associated with at least one piezoelectric actuator for generating an ejection of droplets from the orifice, resulting in a jet flow of fluid exiting the chamber and from the orifice, the jet flow being connected to the orifice The through-flow occurs simultaneously, the jet flow has a maximum value Q _E ; where the orifice outlet of each chamber has an area A _n , and where 2700 μm ² >A _n >650 μm ² and Q _TF >4Q _E .

According to a still further aspect of the present invention there is provided a method for depositing droplets of a fluid comprising the steps of: providing an apparatus according to any one of the preceding aspects; operating said apparatus so as to provide said through-flow and The jet flow.

Preferably, in each of the aspects provided above, each of the orifices is tapered such that the area of the orifice outlet is smaller than the area of the orifice inlet. Alternatively, the orifice inlet may be contained entirely within the fluid chamber such that it does not overlap the chamber walls. The orifice inlets may be defined in the surface facing the corresponding fluid chamber. The surface may surround the top of the corresponding fluid chamber. The orifice outlet may be defined in an opposing surface, which may be parallel to the surface in which the orifice inlet is defined.

Preferably, the orifices may be provided in the orifice plate. The orifice plate may include two generally planar opposing surfaces. One of these surfaces may provide the entrance to the orifice while the other provides the exit from the orifice. The surface defining the inlet therein may surround the top of the array of fluid chambers.

Preferably, each of said elongated chambers is bounded between two elongated chamber walls, the top edges of which together provide a generally flat surface, said orifice plate being attached to said orifice above the surface. Each chamber wall may comprise a piezoelectric material and, optionally, the piezoelectric material may be polarized such that the chamber wall will deform in response to an actuation signal to assume a V-shape. Specifically, when actuated, the wall will have a V-shape when viewed along the length of the chamber. This can be achieved by dividing the chamber wall into two halves along its length, with one half polarized in one direction and the other half polarized in the opposite direction.

To generate a droplet ejection, both chamber walls can be actuated simultaneously. Electrodes may be formed on both sides of the chamber wall facing the two chambers separated by the wall. Where the chamber walls contain piezoelectric material, they can deform in shear mode. The electrodes and the directional polarization of the piezoelectric material of the walls can be arranged to achieve deformation of the chamber walls.

The chambers may have a width, for example, between 20 and 150 microns, between 30 and 130 microns, between 40 and 110 microns, between 50 and 90 microns, or between 60 and 70 microns.

The device may be actuatable to eject droplets using a velocity v, where v is between 2 and 20 m/s, between 3 and 18 m/s, between 4 and 16 m/s, or between 5 and 14 m/s between s.

Description of drawings

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 illustrates a prior art inkjet printer;

Figure 2 is a perspective view from the rear of the printhead of Figure 1 with the end cap removed to show ink flow through the printhead;

3 is a cross-sectional view of the printhead of FIGS. 1 and 2 taken perpendicular to the direction of extension of the nozzle row;

4 is a cross-sectional view of the inkjet printer of FIGS. 1-3 taken along a fluid chamber of the module;

Figure 5 illustrates an additional example of a prior art printhead employing a dual-ended side-firing configuration similar to that of Figures 1-4;

6 is an exploded perspective view of the printhead of FIG. 5 showing conductive tracks for applying electrical signals to actuator elements;

Figure 7 shows an exploded perspective view of a printhead according to a first embodiment of the present invention with nozzles elongated in the direction of chamber extension;

Figure 8 is a perspective view along the length of the chamber of an inkjet printhead and shows the dimensions of the tapered nozzles relative to the size of the fluid chamber of the printhead;

Figure 9 shows the results of a series of tests carried out on printheads with different nozzle areas, at different values of through-flow, with the printhead ejecting droplets at a velocity of 6 m/s;

Figure 10 shows the results of a series of tests similar to those shown in Figure 9, but in which the printhead ejected droplets at a velocity of 12 m/s.

Figure 11 shows the test results of the directional accuracy in the direction perpendicular to the longitudinal axis of the fluid chamber for a series of printheads having nozzle outlets with different length-to-diameter ratios, the printheads all having A nozzle inlet with an aspect ratio of 1.8;

Figure 12 shows the results of a test for directional accuracy in a direction parallel to the longitudinal axis of the fluid chamber for the same series of printheads whose results are shown in Figure 11;

Figure 13 plots the ratio of the values shown in Figure 11 to the values shown in Figure 12, compared to the nozzle outlets for each of the series of printheads shown in Figures 11 and 12. The value of aspect ratio;

14(A)-14(C) are plan views of a series of additional embodiments according to the present invention, wherein alternative nozzle geometries of printheads to those shown in FIG. 7 are used; and

15(A)-15(B) are plan views of a series of yet further embodiments according to the present invention in which alternative chamber geometries of printheads to those shown in FIG. 7 are used.

detailed description

The invention can be implemented in an inkjet printer. Figure 7 thus illustrates an exploded view of an inkjet printhead in an inkjet printer according to a first embodiment of the present invention. As can be seen from the figure, the inkjet printhead comprises a single array of fluid chambers 2 each delimited between a pair of elongated chamber walls 3 . Each fluid chamber 2 is elongated in the channel extension direction C, and the chamber walls 3 are also elongated in this direction. The array extends in an array direction D perpendicular to the direction C of chamber extension. As indicated by arrow 7 in Figure 7, during use of the device, fluid enters each chamber at one longitudinal end of the chamber from a common inlet manifold 4, flows along the length of the chamber through orifice 6 (orifice 6 set toward the middle of the chamber relative to its longitudinal end), and leave the chamber at its other longitudinal end to return to the common outlet manifold 5 . One or more fluid conduits may also be provided to recirculate ink from the common outlet manifold to the common inlet manifold (not shown).

An inkjet printer may have similar structural features to those described above with reference to Figures 1 to 6, such as providing two arrays of ports communicating with a common inlet manifold and a common outlet manifold, respectively, in the surface of the substrate . As shown in Figures 1 to 3, the manifold may also be disposed within a single generally cylindrical housing.

To provide flow 7 through chamber 2, the ink supply system may apply a constant first pressure to the ink in the common inlet manifold 4, and simultaneously apply a constant, lower second pressure to the ink in the common outlet manifold. Ink in tube 5. Such a constant pressure may be provided by a reservoir vertically offset relative to the orifice as known from WO 00/38928, or simply by a corresponding fluid pressurizer. As is also known from WO 00/38928, the fluid supply system can apply a negative pressure (relative to atmospheric pressure) at the nozzle 6 . Those skilled in the art will recognize that this may require that the difference in value between the first pressure and the second pressure be negative. This negative pressure prevents fluid from dripping from the nozzle (6) during non-spraying periods.

The chamber wall 3 may be formed from a piezoelectric material, as described above with reference to Figures 1 to 6, with electrodes (not shown) formed on a portion of the chamber wall so that an actuation signal may be applied to the chamber wall. However, those skilled in the art will recognize that alternative piezoelectric actuators may be utilized in which the chamber is defined in a non-piezoelectric material. For example, chambers can be defined in a non-piezoelectric material using a photolithographic process, and piezoelectric actuators are placed in these chambers at an earlier or later stage, as required.

As represented in Figure 7, the opposing faces of the chamber walls 3 delimiting each chamber are separated by a width w, so that the chamber 2 is said to have a width equal to w. Using a circular nozzle 6, like the configuration of Figs. 1 to 6, the theoretical maximum area that the nozzle can have while still remaining inside the chamber will thus be equal to the value _AT = 1/ ^4TTW2 .

It should be understood that since the width bounds the fluid chamber 2, where the chamber walls 3 include one or more coatings (e.g., electrodes and/or passivation layers), the width should be from the outermost coating of one wall to the other. The outermost coating measures the width.

In practice, however, it may not be possible to reliably form a circular nozzle with such a theoretical maximum area, as this would require the nozzle 6 to precisely match the width and shape of the chamber 2 with one hundred percent accuracy. It may therefore be necessary to take into account the usual sources of manufacturing error in order to determine the actual maximum achievable area of the nozzle.

A first source of such errors is the process by which the nozzle 6 itself is formed. Typically an optical process is used to define the shape and size of the nozzle 6; for example, photolithography can be used to form a complete nozzle plate 8 from a photoresist material, or photoresist can be used as a negative to define the shape of the nozzle holes, where a metal nozzle plate 8 is electroformed around a photoresist pillar, as known from WO 2005/014292. Likewise, the nozzles 6 may be ablated directly within the nozzle plate 8, which may be formed of metal, polymer, or a combination of both. Although such optical processes are relatively accurate, they will still introduce uncertainties on the order of microns.

An additional source of manufacturing error is the process by which chamber 2 is formed. For example, as described above with reference to Figures 1 to 6, this could include sawing channels in strips of piezoelectric material, but could also include molding and sintering of piezoelectric material, or, when using non-piezoelectric materials In the case of defining channels, optical methods can be used. There will be uncertainty not only in the size and shape of the chambers 2, but also in the spacing of each chamber within the array.

Furthermore, the combination of the two processes, specifically the alignment or alignment of each nozzle with respect to its corresponding chamber, will also introduce uncertainty into the manufacturing process.

Taken in combination, these errors can be on the order of 10 microns. Therefore, it may often be necessary to space the edge of the nozzle 6 from the corresponding chamber wall 3 by a distance of nominally 5 micrometers. This is especially the case in situations where the process of forming the nozzle may cause damage to the chamber walls. For example, where laser ablation is used to form the nozzles, scorching of the walls and their coatings may occur.

While processes have been proposed to reduce the incidence of such damage, such as those disclosed in WO 2012/017248, these may only protect the interior walls of the chamber, but not the top edges of the chamber walls, including any coatings. As discussed in WO 2012/017248, damage to coatings such as electrodes and passivation layers can significantly affect the performance of the device: damage to the electrode layer can cause chambers to have lower activity than other chambers in the array , or even be completely inactive; damage to the passivation layer can lead to chemical attack on the underlying layers, which can affect the lifetime of the device. Therefore, even where protective processes such as those taught in WO 2012/017248 are available, it may still be important to isolate the nozzle inlet 6b from the chamber wall.

While the size of the nozzle inlet 6b can be related to the size of the chamber, it has been found that the size of the nozzle outlet 6a can be related to the throughput of the apparatus. In particular, for a given nozzle inlet 6b, the area of the nozzle outlet 6a is considered to be the limiting factor for the size of the droplets ejected by the device.

However, since it has been found that in some cases it is desirable to form a nozzle with a taper (which can result in improved stability of the fluid meniscus at the nozzle), the area of the nozzle outlet 6a can in turn be related to the area of the nozzle inlet 6b And, specifically, it may be smaller than the area of the nozzle inlet 6b. However, the applicant has identified certain methods in which the size of the nozzle outlet 6a can be optimized, applicable even with these constraints.

FIG. 8 is a perspective view along the length of the chamber 2 of an inkjet printhead showing the dimensions of such a tapered nozzle 6 relative to the size of the fluid chamber 2 . As can be seen, the inlet of the nozzle communicates with a fluid chamber having width w. The nozzles taper towards their outlets, which are formed in opposing surfaces of the nozzle plate.

As can be seen from FIG. 8 , the width of the nozzle inlet 6b is taken as w-e, where e is a value chosen to substantially increase the likelihood that the nozzle inlet 6b will lie entirely within the width of the chamber 2 . The value e is thus chosen so as to take into account the various sources of error in the formation of the nozzle 6 and chamber 2 discussed above, and may therefore take a suitable value, eg 10 microns, 7 microns, or 5 microns.

The width of the nozzle outlet 6a is then even smaller as a result of the nozzle's conical shape, which is defined by the angle θ. As shown in Figure 8, the taper angle Θ may be defined at the point where a line parallel to the array direction and passing through the center of the nozzle inlet 6b intersects the perimeter of the nozzle inlet. As also shown in Figure 8, the taper angle can be defined relative to a direction that is both perpendicular to the array direction and perpendicular to the chamber extension direction. In a typical inkjet printhead, the taper angle of the nozzles may be between 5 and 15 degrees, and in some instances may be between 10 and 12 degrees.

As further shown by FIG. 8 , the nozzle plate 8 in which the nozzles 6 are formed has a thickness t. In a typical inkjet printhead, the thickness of the nozzle plate 8 may be in the range of 50 to 150 microns, but those skilled in the art will appreciate that many other values would be suitable.

As is apparent from the diagram in FIG. 8 , the difference in width between the nozzle inlet 6b and the nozzle outlet 6a is 2t·tanθ, so that the nozzle inlet 6b has a width of (w−e−2t·tanθ). The nozzle outlet 6a thus has an area defined by the following relationship:

A _P ＝1/4TT(we-2t·tanθ) ²

Thus, where it is desired that the nozzle inlet 6b be contained within the width of the fluid chamber, the maximum value that the circular nozzle outlet 6a can take in practice may be _Ap , as defined in this equation. It will be appreciated by those skilled in the art that where different parts of the nozzle have different taper angles, the average value of the taper angles may be used in the above formula given that this represents only an approximation of design constraints.

For a typical drop deposition device, especially an inkjet printhead, this practical maximum area for a circular nozzle may be around 530 square microns. This is based on a chamber width w of 65 microns, taking into account a coating of 5 microns on each chamber wall (the spacing between the chamber walls themselves is thus 75 microns).

In contrast, in such a device, the theoretical maximum value ( _AT = 1/4TTW ² ) of a circular nozzle can thus be calculated based on these values to be about 3320 square microns, which is clearly significantly larger than A The value of _P.

Returning to the embodiment of Figure 7, as indicated above, the nozzle is elongated in the chamber extension direction C. Consequently, their area is increased relative to both the theoretical maximum and the practical maximum, since these maximums are based on circular nozzles. As noted above, the increased area of the nozzles, particularly of the nozzle outlets 6a, can lead to an increase in the volume of each ejected droplet, thereby increasing the productivity of the printhead. Furthermore, because the nozzle is elongated in the same direction as the flow of fluid through the chamber, the flow through the chamber is particularly effective at flushing debris away from the vicinity of the nozzle. This can lead to improved reliability of the printhead. This improvement in reliability may also be experienced by nozzles that do not exceed the practical maximum area _AP , but it should be understood that such printheads will not necessarily benefit from the improvement in productivity.

To achieve a considerable effect on the productivity of the printhead, it has been found that it will usually be necessary to increase the area of each nozzle by 25%. In order to improve the productivity of the printhead, a lower limit of _1.25AP may be imposed on the area of the nozzles. In the inkjet printhead described above, this lower limit may correspond to about 650 square microns.

Furthermore, since the area of the nozzles 6 is increased and thus more ink is ejected from the chamber 2, it is expected that the chamber will be cooled more effectively. Heat from the device, and in particular the actuator element 3 , will be transferred to the ink during use, wherein the ejection of this fluid thus serves to remove heat from the chamber 2 adjacent to the actuator element 3 . Thus, as the area of the nozzle 6 increases, and thus the amount of flow through the nozzle 6 in the form of droplets, the rate at which heat is transferred away from the actuator should increase, resulting in improved cooling of the equipment in addition to increased productivity .

In order to quantify this cooling effect, tests were carried out on a series of printheads, with different printheads each having nozzles 6 of a specific area. The operation of each of these printheads was tested at different rates of flow through the chamber 2 . The results of these experiments are shown in FIG. 9 .

The chamber 2 of the printhead has the same typical value for the chamber width discussed above, namely a chamber width w of 65 microns. A practical maximum of 530 square microns is taken for the nozzle outlet 6a, also as discussed above.

The printhead comprises an array of elongate chambers 2, as shown in Figure 7, each chamber bounded between a pair of elongate piezoelectric chamber walls 3, wherein during use a common inlet manifold is provided. The flow of tubes 4 to a common outlet manifold 5 runs along the length of each chamber. This through-flow occurs simultaneously with the ejection of droplets from the nozzle 6, which, although the droplets are undoubtedly discrete volumes of fluid, can be considered to correspond to another jet flow. For each printhead, the temperature difference between the ink at the inlet manifold 4 and the ink at the outlet manifold 5 was measured at various values of the flow through the chamber 2 .

On the abscissa of FIG. 9 the rate of flow through the print head is shown. Due to jetting, the flow rate of the printhead is expressed relative to the maximum flow through the nozzle 6 due to jetting. This corresponds to a chamber where drops are printed at maximum firing frequency, where the printhead imparts a velocity of 6 m/s to each drop. A value of 1 on the abscissa therefore corresponds to a flow through each chamber and to the outlet manifold equal to the maximum jet flow. Since the injection flow and the through-flow occur simultaneously, there will be an equal amount of fluid returned to the outlet manifold during maximum injection as injected from the nozzle 6 .

The values shown on the coordinates of FIG. 9 represent the temperature difference ΔT in degrees Celsius between the ink at the inlet manifold and the ink at the outlet manifold. This temperature difference can be used to represent the cooling effect within the printhead in question.

Each line on the graph of Figure 9 thus represents a different printhead with a respective nozzle exit area. The legend to the figure thus shows the respective nozzle areas for the chamber using the dimensionless area ratio AR, which is the ratio of the nozzle area in question to the actual maximum nozzle area _Ap . As noted above, the practical maximum nozzle area A _p value is 530 square microns.

As can be seen from Table 1 below, the increase in nozzle area resulted in an increase in productivity, as expected. The table illustrates the droplet volume measurements for each value of area ratio AR.

Table 1

While this increase in productivity (through an increase in droplet volume) was expected, it was unexpectedly found that larger nozzle areas did not remove heat from the chamber most efficiently, as can be seen from FIG. 9 . In fact, at modest values of throughflow, they perform significantly worse than nozzles with an area of 3A _P or less.

It is also expected that the amount of through-flow in the chamber will also serve to improve the cooling of the chamber. It is therefore particularly surprising that nozzles with larger areas have worse performance at similar through-flow values, since the through-flow values are relative to the jet flow, and therefore the same through-flow values for larger nozzle areas correspond to for further larger flows in absolute terms.

However the results do show that for nozzles 6 having an area larger than _3AP the effectiveness of cooling is greatly reduced. Thus, it turns out that nozzles 6 with an area of less than 3A _P would be particularly efficient at cooling the device. Thus, equipment using nozzles 6 having areas in the range of _1.25AP - _3AP may provide an increase in productivity while also allowing particularly efficient cooling of the equipment. The area of this range can also be expressed in terms of the theoretical maximum area _AT of the chamber, which is calculated based on the chamber width value of 65 microns (according to the formula A _T =1/4TTW ² ) to be about 3320 square microns. Therefore, the range of nozzle outlet 6a area can be restated as _0.48AT >An > _{0.20AT .} Alternatively, in absolute value, the range may be stated as 1600 μm ² >A _n >650 μm ² .

It should be understood that while the test results shown in Figure 9 appear to indicate an inflection point at _3AP , there may be some uncertainty in this value. Thus, an advantageous upper limit for nozzle area may take values less than 3AP, such as 2.5, 2.6, 2.7, 2.8, or _2.9AP , which correspond to 0.40, 0.42, 0.43, 0.45, and _0.46AT , _respectively , or about 1330 , 1380, 1430, 1487, and 1540 absolute values of square microns. Likewise, advantageous upper limits may take values greater than 3AP, such as 3.1, 3.2, 3.3, 3.4, or _3.5AP , which correspond to 0.50, 0.51, 0.53, _0.54 , and _0.56AT , respectively, or about 1650, 1700, Absolute values of 1750, 1810, and 1860 square microns.

Likewise, while a lower limit of _1.25AP may be appropriate for productivity reasons, a larger lower limit may be appropriate under certain conditions in order to provide a considerable increase in productivity. Therefore, lower limits of 1.30, 1.35, 1.40, 1.45, and 1.50 A _P may be satisfactory, which correspond to 0.21, 0.22, 0.22, 0.23, and 0.24 A _T , or 690, 720, 740, 770, and Absolute value of 800 square microns.

As can be seen from Figure 9, as the amount of through-flow increases, the variance between the different printheads decreases. In particular, the temperature difference experienced in the 5A _P printhead (corresponding to _0.8AT or about 2655 square microns) was 0.2 times the value of the temperature difference experienced in the other printheads when the throughflow exceeded the value of the jet flow by 4 times. within degrees. Since 0.2 degrees is generally considered to be within a normal deviation range, which can be neglected depending on the environment, the performance of both devices in terms of lifetime and droplet characteristics is substantially the same.

Figure 10 illustrates the results of another similar set of tests, but in which the printhead ejects droplets at a velocity of 12 m/s. The same pattern of less efficient cooling of the larger nozzle area shown in FIG. 9 can also be seen in FIG. 10 .

It is believed that the deterioration in cooling provided by printheads with larger nozzle areas is due to the higher drive voltage required to eject relatively larger droplets. Specifically, to achieve the same velocity of ejection of larger droplets, a greater amount of energy is required to overcome the relatively greater inertia of the droplets. This greater amount of energy can thus result in increased heating of the ink within the chamber. For typical values of the through-flow, this heating effect appears as an increased flow dominating the heat coming out of the chamber 2 due to the larger jet flow.

It will therefore be appreciated that similar effects should be expected with a variety of nozzle geometries, and not necessarily with elongated nozzles.

More specifically, although there may be advantages associated with the elongation of the nozzle inlet 6b, the effects described above are mainly related to the area of the nozzle outlet 6a, in contrast to the shape of the outlet 6a. It may therefore be particularly advantageous to provide a structure in which the nozzle inlet 6b is elongated in a direction parallel to the longitudinal axis of a corresponding one of the fluid chambers, and wherein the nozzle outlet 6a has the above An area within the range discussed that provides benefits in terms of providing productivity improvements with a desired level of temperature control.

Still more specifically, the applicants have found that it may be advantageous to provide nozzles in which the inlet 6b is elongate (in particular, in a direction parallel to the corresponding longitudinal axis of one of the fluid chambers) and has a ratio The aspect ratio of the nozzle outlet 6a is large. Figures 11 to 13 thus show the results of tests performed using a series of printheads having a range of values for the aspect ratio of the nozzle outlets, but all having nozzle inlets with the same aspect ratio of 1.8 . Both the nozzle outlet and the nozzle inlet are approximately elliptical in shape.

Each point on the graph corresponds to a result from a particular printhead (so note that two printheads were tested using each of the nozzle exit aspect ratio values of 1.0 and 1.4).

Figure 11 shows the error in the landing position of a drop produced by the printhead in the X direction (perpendicular to the longitudinal axis of the fluid chamber) versus the corresponding value of the nozzle outlet aspect ratio of the printhead. Specifically, error values are 3-sigma values measured in microns. As noted above, the aspect ratio of the nozzle inlet remained the same at 1.8 for all printheads.

As can be seen from the figure, with the increase of the value of the nozzle outlet aspect ratio, there is an obvious trend that the error of the drop point in the X direction increases (note that the two nozzles with the nozzle outlet aspect ratio value of 1.4 are recorded) printheads, with substantially the same drop placement error in the X direction). It can thus be understood that as the aspect ratio of the nozzle outlet decreases and thus the nozzle outlet becomes more circular, the landing error in the X direction also decreases.

Figure 12 shows the error in the landing position of a drop produced by the printhead in the Y direction (parallel to the longitudinal axis of the fluid chamber) compared to the corresponding value of the nozzle outlet aspect ratio of the printhead. Again, the error values are 3-sigma values measured in microns, and the aspect ratio of the nozzle inlet was kept the same for all printheads at 1.8.

Compared to the trend shown in Fig. 11, the drop point error in the Y-direction remained approximately constant for all tested nozzle exit aspect ratio values. The data therefore suggest that making the nozzle outlet more circular does not have a significant effect on the landing error in the Y direction.

FIG. 13 shows the ratio of the error in the X direction to the error in the Y direction compared to the value of the nozzle outlet aspect ratio. As can be seen from the graph, there is a very clear trend of decreasing error ratio values due to decreasing nozzle outlet aspect ratio values. It can therefore be appreciated that the directional accuracy of the device increases when the nozzle outlet is made more circular.

The data shown in Figures 11 to 13 thus clearly show that nozzles having a nozzle outlet with a lower aspect ratio than the nozzle inlet can have improved precision of droplet positioning. Furthermore, if the nozzle inlet is elongated in the direction of the longitudinal axis of the fluid chamber, it may also provide the manufacturing and operational benefits discussed further above.

The graph also shows that nozzles with approximately circular nozzle outlets (corresponding to an aspect ratio of 1.0) have a particularly high level of drop positioning accuracy. Thus, it may be particularly beneficial to provide nozzle inlets having an elongate shape in the longitudinal direction of the fluid chamber (and in particular nozzle inlets which are elliptical, where the major axis of the ellipse is aligned with the longitudinal axis of the chamber) and which are approximately circular Nozzles with shaped nozzle outlets. Furthermore, the nozzle outlet has an area that is one of the ranges discussed above, which provides benefits in terms of providing increased productivity with a desired level of temperature control.

It can also be noticed that the accuracy difference between the nozzle outlet with an aspect ratio of 1.0 and the nozzle outlet with an aspect ratio of 1.2 is small. Thus, similar advantages in accuracy can be experienced for orifices with aspect ratios between 1.0 and 1.2.

Figures 14(A)-14(C) and Figures 15(A)-15(B) illustrate still further embodiments with alternative geometries for the nozzle and also for the chamber, which can be experienced with reference to Similar improvements in productivity to those discussed in Figures 9 and 10, combined with good thermal control.

Figure 14(A), for example, provides circular nozzles whose inlets 20a have a diameter greater than the width w of the chamber 11 with which they communicate, compared to the embodiment described above, for example with reference to Figure 7 . Such nozzles may be fabricated by an "ex situ" process in which the nozzles are formed in a nozzle plate component before being attached to the edge of the chamber wall to surround the chamber. In this way, there is little risk that the nozzle forming process will damage the chamber walls.

Although the nozzle inlet 20a has a greater width than the chamber 11 with which the nozzle inlet 20a communicates, and thus has an area greater than the theoretical maximum A _T = ¹ /4TTW2 cited above, the nozzle outlet 20b still has the above-discussed An area within a range that provides benefits in providing productivity improvements with a desired level of temperature control. For example, the nozzle outlet 20 b may have an area defined within the range of _0.48AT >A _n > _0.20AT , or alternatively, in absolute terms, 1600 μm ² >A _n >650 μm ² .

Figure 14(B) illustrates a similar embodiment to Figure 14(A), but with the nozzle being elongated in the same direction as the fluid chamber. This can provide improvements in reliability as discussed above.

Figure 14(C) shows an alternative embodiment in which the outlet 20b of the nozzle is elongated and the inlet 20a is circular. As in the embodiment of FIG. 14(A), the diameter of the inlet 20a is larger than the width of the chamber 11.

Figure 15(A) illustrates a still further embodiment in which chamber walls are tapered along their length, wherein the direction of the taper alternates between adjacent chamber walls. This results in chambers 11 of substantially constant width, but which are not parallel to each other. More specifically, the length of each chamber is angularly offset relative to the array direction, wherein the direction of the angular offset alternates between adjacent chambers 11 .

Figure 15(B) illustrates a still further embodiment in which, like the embodiment of Figure 14(A), a circular nozzle is provided. However, in this embodiment the chamber includes a portion in the vicinity of the nozzle which has a relatively greater width than the remainder of the chamber. Specifically, portions of the chamber in the vicinity of the chamber follow a similar profile to the nozzle itself, which can help ensure that the inlet is confined between the chamber walls.

Those skilled in the art will appreciate that the above teachings are applicable to a wide range of droplet deposition devices and are not specific to printers. Accordingly, disclosures relating to printers and/or printheads should be understood to apply more generally to droplet deposition devices unless otherwise stated. In particular, the disclosure regarding printheads should be understood, unless otherwise stated, to apply to other droplet deposition devices comprising: an array of elongate fluid chambers, wherein each chamber is associated with an orifice for droplet ejection communicated, and the array extends in the direction of the array; a common fluid inlet manifold; a common fluid outlet manifold; Means for the flow of fluid through the common fluid outlet manifold.

Claims (19)

1. a kind of liquid-droplet ejecting apparatus, comprising:

The array of elongated fluid chamber, each elongated fluid chamber is connected with the aperture for droplet jet, and described array exists Array direction extends；

Common fluid intake manifold；

Common fluid issuing manifold；And

For produce from described common fluid intake manifold pass through described array each elongated fluid chamber and enter Through-flow (the q of the described common fluid of fluid issuing manifold_tf) device；

Each of wherein said elongated fluid chamber is connected with described common fluid intake manifold in a longitudinal end And connect with described common fluid issuing manifold in relative longitudinal end；

The elongated fluid chamber of each of which is associated the liquid for being produced from described aperture with least one piezo-activator Drip injection, lead to the jet flow of fluid left from described elongated fluid chamber and from described aperture, described jet flow with Described through-flow occur simultaneously, described jet flow has maximum q_e；

Each of wherein said elongated fluid chamber has width w in described array direction, thus defining described aperture Theoretical circular area a_t=1/4ttw², the aperture exit for each elongated fluid chamber has area a_n, wherein 0.48a_t>a_n> 0.20a_t.

2. equipment according to claim 1, wherein, being actuated at of each of described piezo-activator piezo-activator Each of the longitudinal end of fluid chamber elongated accordingly place produces sound wave, and described sound wave is then towards described aperture row Enter.

3. equipment according to claim 1, wherein, for each of described aperture aperture, described aperture exit Draw ratio is less than the draw ratio of aperture entrance.

4. equipment according to claim 3, wherein, the described aperture exit in each of described aperture aperture is approximate Ground is circular.

5. the equipment according to claim 1,2,3 or 4, wherein, q_tfValue be enough to ensure that and be back to described common fluid The temperature of the fluid of outlet manifold is generally kept in and enters described elongated fluid chamber from described common fluid intake manifold 0.2 DEG C of fluid in.

6. the equipment according to claim 1,2,3 or 4, wherein said through-flow amount makes q_tf>0.25q_e.

7. the equipment according to claim 1,2,3 or 4, wherein said through-flow amount makes q_tf>q_e.

8. the equipment according to claim 1,2,3 or 4, wherein, described aperture is arranged in orifice plates.

9. equipment according to claim 8, wherein, each of described elongated fluid chamber is in two elongated locular walls Between define, the top of described locular wall provides the surface of general planar jointly, and described orifice plates are attached to described surface.

10. the equipment according to claim 1,2,3 or 4, wherein, each of described elongated fluid chamber is long at two Define between the locular wall of shape.

11. equipment according to claim 9, wherein, each of described piezo-activator is along elongated accordingly The length of fluid chamber extends.

12. equipment according to claim 10, wherein, each of described piezo-activator is along elongated accordingly The length of fluid chamber extends.

13. equipment according to claim 11 or 12, wherein, each of described piezo-activator is generally from described The first end of elongated fluid chamber extends to the second end of described elongated fluid chamber.

14. equipment according to claim 9 or 11, wherein, described locular wall comprises piezoelectric, in described piezo-activator Each include corresponding one in described locular wall.

15. equipment according to claim 10, wherein, described locular wall comprises piezoelectric, in described piezo-activator Each includes corresponding one in described locular wall.

16. equipment according to claim 1,2,3,4,9,11,12 or 15, wherein, the longitudinal direction of described elongated fluid chamber In passage bearing of trend and wherein said passage extends perpendicularly to described array direction to diameter parallel.

17. equipment according to claim 1,2,3,4,9,11,12 or 15, wherein, each of described aperture becomes cone Shape is so that the area of described aperture exit is less than the area of aperture entrance.

18. equipment according to claim 1,2,3,4,9,11,12 or 15, wherein, each of described aperture is flat The direction of the longitudinal axis of corresponding in described elongated fluid chamber for the row is elongated.

A kind of 19. methods of the drop for deposits fluid, comprise the following steps:

There is provided according to equipment in any one of the preceding claims wherein；

Operate described equipment to provide described through-flow and described jet flow.